PB89-126478
Permit Writers Guidance Manual for
Hazardous Waste Tanks
Battelle Columbus Div..- OH
Prepared for
Environmental Protection Agency, New York
1988
I
J
U;S. Department of Commerce
National Technical Information Service
-------
-------
- 1 ^ b 4 7 6
DRAFT
on
PERMIT WRITERS' GUIDANCE MANUAL
FOR
HAZARDOUS WASTE TANKS
to
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION II
from
BATTELLE •
Columbus Division
505 King Avenue
Columbus, Ohio 43201
EPA Contract 68-01-6515
U'A 02-004
REPRODUCED BY
U.S. DEPARTMENT OF COMMERCE
NATIONAL TECHNICAL INFORMATION SERVICE
SPRINGFIELD. M. 22:61
-------
ACKNOWLEDGEMENTS
This document was prepared at Battelle's Columbus Division with
contributions being made by G.C. Stotler (Project Manager), John Hallowell
(Work Assignment Manager), and J.L. Otis, T.S. Reddy. ancJ-Dr. D.N. Gideon
(Principal Investigators). Battelle ««ss acting as a subcontractor to
A.T. Kearney, Inc., with Mr. Joseph Fantasia serving as Regional Liaison
for that organization.
The project was supported and directed by staff of the U.S. EPA
at ths Region II office. Early definition of the content of the document
was guided by comments from permit reviewers at many of the EPA Region
offices with special inputs from Heather Ford, Garrett Smith, and D. Pagan;
important contributions to the direction of the project were made by Ernie
Regna and especially the ZPA Region II Project Officer, Barbara Kropf.
Comments on the draft report are encouraged. They should be
directed to:
Ms. Barbara Kropf
U.G. EPA Regior, II
Waste Management Division
26 Federal Plaza
New York City, New York 10278
Telephone: (212) 264-0504.
-------
PREFACE
This Working Draft of the "Permit Writers' Guidance Manual for
Hazardous Waste Tanks" was developed to provide guidance to the permit
reviewer in evaluating the design of hazardous waste tanks, piping, controls,
and ancillaries (containment measures, vents, etc.)- The manual is aimed
at presenting supporting material where possible within the manual or,
alternatively, offering summaries or indications of content and coverage
of the extensive technical material contained in existing standards, codes,
handbooks, etc.
Because of the wide spectrum of tank characteristics and applications
anticipated to be encountered by the permit reviewer, the content of this
document contains a diversity of subject matter. Some of the content was
selected for coverage on the basis of comments from Regional Offices contacted
as the first step in the preparation of this manual. The format and arrangement
of the draft manual have been selected with the aim of allowing for addition
of supplementary material by the individual user and possibly the incorporation
of uniform changes and additions at some future time.
Similarly, sach section contains a detailed listing of content
intended as an aid in assessing material as different requirements arise.
-------
TABLE OF CONTENTS
1.0 USE AND ORGANIZATION OF THE MANUAL ............. 1-2
1.1 How to Use the Manual ................ • 1-2
1.2 Manual Organization .................. 1-3
1.3 References, Codes, and Handbooks ........ • • • 1-4
REFERENCES ....................... ..... 1-6
2.0 GENERAL PROCESS CONSIDERATIONS ... ............ 2-2
2.1 Process Flow Diageam (PFD) ............ • • 2-2
2.2 Piping and Instrumentation Diagram iP&ID) ...... . 2-4
2.3 Classification of Hazardous Wastes .......... 2-5
2.4 Installation of Outside Above-Ground Tanks ...... 2-7
3.0 STANDARD METAL TANK DESIGN ................ 3-3
3.1 General ........................ 3-3
3.2 New Metal Tanks .................... 3-10
4.0 USED, NON-METAL, AMD OTHER TANKS ............. 4-2
4.1 Used Steel Tanks . .................. 4-2
4.2 Fiberglass-Reinforced Plastic Tanks .......... 4-8
4.3 Rectangular (Polygonal) and Other Son-Standard
i^etal Tanks ....... . ....... ..... 4-13
4.4 Concrete Tanks ................. ... 4-14
5.0 TANK ANCILLARIES: PRESSURE AND OTHER CONTROL SYSTEMS ... 5-2
5.1 Internal Pressure .ind Pressure Controls ........ 5-2
5.2 Other Controls and Instruments ............ 5-10
6.0 TANK ANCILLARIES: PUMPS, PIPING AND AGITATOR
STUFFING BOXES ...................... 6-2
6.1 Pumps ......................... 6-2
6.2 Piping ..................... ... 6-4
6.3 Agitator Stuffing Boxes ................ 6-10
7.0 TANK ANCILLARIES: FOUNDATIONS, SUPPORTS, INSULATION,
AND GROUNDING . . . . .......... _ ........ 7-2
7.1 Foundations ..................... 7-2
7.2 Structural Tank Supports ............... 7-5
7.3 Thermal Insulation .................. 7-6
7.4 Electrical Grounding ................ 7-6
-------
TABLE OF CONTENTS
(Continued]
Page
8.0 INSPECTIONS 8-2
8.1 Evaluation of Inspection Plan _ 8-4
8.2 Weekly Above-Ground External Tank Inspection 8-6
8.3 Detailed Assessment of Tank Condition 8-6
8.4 Inspection of Auxiliary Equipment 8-7
8.5 Inspection Tools and Procedures 8-16
8.6 Frequency of Tank Inspection 8-18
9.0 SPILLS, LEAKS, AND SECONDARY. CONTAINMENT 9-2
10.0 REACTIONS IN TANKS 10-2
APPENDIX A
TABLE A-l. REGULATORY ANALYSIS OF TANKS A-2
APPENDIX B
CORROSION AND DETERIORATION OF
MATERIALS OF CONSTRUCTION B-2
LIST OF TABLES
Table 1-1. References for Use with the Permit Guidance
Manual for Hazardous Waste Tanks ........... 1-5
Table 2-'. Buffer Zones for Tanks of Stable Liquids ....... 2-8
Table 2-2. Buffer Zones for Tanks Containing Stable
Liquids ............... . ........ 2-9
Table 2-?. Buffer Zones for Tanks Containing Boil -Over
Liquids ........................ 2-9
Table 2-4. Buffer Zones for Tanks Containing Unstable
Liquids ........................ 2-10
Table 2-5. Buffar Zones for Tanks Containing Class III B
Liquids ........................ 2-11
Table 2-6. Reference Table for Use With Tables
2-1 to 2-4 ...................... 2-11
O
iv
-------
TABLE QF_CONTENTS
~~ (Continued)
LIST OF TABLES
(Continued)~
Table 3-1. Impact of Selected Properties of the
Waste on Tank Design ................ 3-7
Table 3-2. Summary Checklist for Tank Design ......... 3-11
Table 3-3. Materials Groups ............. 3-21
Table 3-4. Maximum Allowable Stress Values fcr Simple
Tension .... ..... 3-26
Table 3-5. Maximum Allowable Efficiencies for Arc-Welded
Joints . 3-29
Table 3-6. Permissible Plate Materials and Allowable
Stresses 3-33
Table 6-1. Pump Classes and Types 6-3
Table 8-1. Checklist of Tank External - Inspection Points , . . 8-8
Table 8-2. Chec.list for Tank Internal Inspection (Tank
Out of Service) ......... 3-10
Table 3-3. Checklist for Inspection of Piping, Valves, and
Fittings 8-13
Table 8-4. Checklist for Visual Inspection of
Pumps and Compressors 8-14
Table 8-5. Checklist for Inspection of Instruments
and Control Systems 8-15
Table 8-6. Mandated Inspection Frequencies 8-19
Table 9-1. Operational Problems of Tanks 9-3
Table 10-1. Oxidation Waste Treatment Applications 10-4
Table 10-2. Information for Estimating Corrosion
Against Performance 10-7
Table 10-3. Reduction Waste Treatment Applications 10-8
-------
LIST OF FIGURES
Page
Figure 2-2. A Simplified Piping and Instrumentation
Diagram 2-6
Figure 3-1. Minimum Permissible Design Metal Temperature
for Plates Used in Tank Shells Without Impact'
Testing (in degree Fahrenheit) 3-20
Figure 3-2. Biaxial Stress Chart for Combined Tension and
Compression, 30,000 to 38,000 psi Yield Strength
Steels 3-39
Figure 3-3. Typical Tank Data Sheet 3-46
Figure 3-4. A Simple Tank Diagram 3-47
Figure 5-1. Simplified Process Flow Diagram, Common Vapor
Recovery System 5-9
V1
-------
CHAPTER CONTENTS
USE AND ORGANIZATION OF THE MANUAL
1,1 How to Use the Manual
1.2 Manual Organization
1.3 References, Codes, and Handbooks
-------
1-2
1.0 USE AND ORGANIZATION OF THE MANUAL
The purpose of this manual 1s to provide a resource for permit
writers in the implementation of Part 264, Subpart J*, of Code of Federal
Regulations, which sets forth regulations for facilities that use tanks to
treat or store hazardous waste. The material is meant for guidance pur-
poses only and is not meant to replace data and Information that are
specific to the facility being assessed.
More specifically, this manual has been written primarily to
assist permit writers when performing a technical review of Part B permit
applications for facilities that treat or store hazardous ^?ste in tanks and
when writing the fi^al permit. While this manual was not primarily designed
to support the activity of a "completeness check", the regulatory analysis
(i.e., an itemized breakdown of regulatory requirements) given in Appendix
A can be useJ as a support item in a completeness check.
In general, it has been assumed that the most likely user of the
manual would be either an engineer or a scientist with some experience in
reviewing engineering information. Nevertheless, other professionals
could probably make significant use of the nu.iLial if engineering *csociate«
were available for consulting.
I.I How to Use the Manual
This manual can be used only in conjunction with a reference
library of various standards, codes, handbooks, data surveys, and other
literature—conceptually the manual could be called "Volume I" and bhould
be expected to make frequent reference to documents in a reference library
that could be called "Volume II' for further details. However, nearly all
of the reference library is copyrighted material that cannot be legally
integrated into a real "Volume II".
The subject of tank permitting has many aspects about which the
permit writer should be aware, ranging from systems, tank types, controls,
auxiliaries, foundations and supports, inspections, spills and containment.
hazardous mixtures, deterioration, to regulations. To assist the perrrt
-------
1-3
writer, these suojects have been subdivided into discrete subject areas
under a large nurnoer of subject headings.
Only major headings are presented in the rain Table of Contents
at the beginning of the manual; this will allow the permit writer to
quickly scan the main Table of Contents to determine the ehapiar in which
the desired material is likely to be found, and go directly, to the appro-
priate chapter. Each chapter containing three or n.ore levels of headings
has its own detailed chapter Table of Contents showing both the major and
the minor headings. The detailed chapter outline will allow the permit
writer to determine th«? specific section number in which the desired
information is located. (Note: Conventional pace numbers are not used
to allow easy insertion, without pagination problems, of either naw or
revised material as it is developed by the permit writers themselves,
or in response to their needs; it is hoped that this manual will become
a "1iving" document.)
1.2 Manual Organization
The manua'i is organized assuming that tl.e permit writer will have
icientifiea tc.-c.hnleal jrtas for wrricn he needs ^uidanoe, T^e overall scheTH?
of the manual is as follows:
• The general relationship of tanks to the rest of the
facility is presented first in Chapter 2.
o Standard ne* metal tanks are presented next in Chapter 3,
and all other types of tanks are presented in Chapter 4.
« Tank ancillaries are presented in Chapters 5, 6, and 7.
- Chapter 5. Pressure and Other Control Systems
- Chapter 6. Pumps, Piping and Stuffing Boxes
- Chapter 7. Foundations, Supports, Insulation and Grounding
• Required inspections of tanks are discussed in Chapter 8.
0 Chapter 9 contains a discussion of spills and leaks and
secondary containment as these pertain to tanks from both
a regulatory and practical viewpoint.
• Chapter 10 contains a discussion of problems that may occur
upon mixing of various hazardous wastes.
-------
• A concise regualtory analysis 1s presented as Appendix A
for quick reference by the permit writer.
• A discussion about corrosion and deterioration of various
materials of construction is presented^in Appendix B.
Even though thought was given to the manual's outline, problem
areas did arise in attempting to formulate and use an outline. Although
an effort was made to categorize the information presented into discrete
sections of the manual with a minimum amount of cross references, some
cross referencing was necessary to avoid excessive redundancy. Some of
the consequences are as follow:
* Permit writers will not have to refer to Chapter 4 if only
new standard metal tanks are being permitted. However,
reference to both Chapters 3 and 4 will probably be required
if used metal tanks are Involved.
• Inspection of fiberglass-reinforced plastic tanks is covered
1n Chapter 4 even though Chapter 8 1s titled "Inspections".
Some chapters and appendices have not been completed. Neverthe-
less, in most cases some information was available from 3 similar manual
previously prepared by Frad C. Hart Associates, Inc., and this information
was inserted where appropriate. Examples are as follow:
"Pumps" in Chatper 6
"Spills and Leaks" and "Secondary Containment'1 in Chapter 9
"Reactions in Tanks" 1n Chapter 10
1.3 References, Codes, and Handbooks
As stated, this Manual serves as a "bridge" to the extensive tech-
nical background possibly required in consideration of issuing a permit for
a tank. This manual cannot include all technical background which might
be required for specific cases because of the volume of such material and
because some of the material is covered by copyright restrictions. However,
in developing this manual, some reference materials were judged to be more
often used than others. The reference materials relevant to tanks is listed
in Table 1-1 with an indication of the estimate of the likely importance o*
the reference material in the activity of permit review.
-------
1-5
TABLE 1-1. REFERENCES FOR USE HITH THE
PERMIT GUIFjANCE MANUAL FOR
HAZARDOUS WASTE TANKS
Reference
API 620
API 640
NFPA 30
API 12B
API 12D
AM liS-'
/.Pl i2A
ANSI 1396-1
UL 142
III 56
ASKE Section VIII
API Guide for Imputing Refinery
Chapter XIII
Chapter II
Chtpter IV
Chapter V
Chapter XV
Chapter XVI
Other Chapters
AS7M C.'021-81
'."_ 13^ (tentetlv*!
Primary Options! Seldom Used
Subject (Short Form) Referenc? Reference Reference
Low pressure tanks x
Atmospheric pressure tanks x
Flasmabl* 'Iquids x
Bolted tanks • x
Large tanks x
tell Uf-itS X
Riveted tsnks x
AliRlnuR tinis x
Above-grour;! "gas" 'unks x
Underground "gas" tanks x
Pressure vessels x
Equipment
Tanks - low pressure x
Conditions causing failures x
Inspection tools *
Safe practices x
Instruments x
Pressure relieving devices x
(miscellaneous) x
Fiberglass-reinforced tanks x
Fiberglass-reinforced tanks, x
of Concrete Practic
ACI 3'3
AC I 350
ACI 201.1 R-68
ACI 311-75
API 2000
ANSI 8 31.3
ANSI 8 31.4
NACE - Corrosion Data Survey
NFPA 31
Perry's Handbook
K- rtt's Handbook
NFPA 77
Petroleun Process Handbook
Reinforced concrete
Sanitary Engineering practice
Condition of concrete
Inspection of concrete
Tank venting
Refinery piping
Transport piping
Hetals Section
Non-««t*ls Sect'.on
Oil-burning equipment
Cheailcal engineering
Mechanical engineering
Static electricity
O
-------
1-6
REFERENCES
"Welded Steel Tanks for 011 Storage", API Standard 650, Seventh Edition,
November 1980; American Petroleum Institute, 2101 L Street Northwest,
Washington, D.C. 20037.
"Standard for Glass-Fiber-Reinforced Underground Storage Tanks for retroleum
Products - UL 1316" (draft, January 1982), Underwriters Laboratories, Inc.,
333 Pfingsten Road, Northbrook, Illinois 60062.
"Flammable and Combustible Liquids Code, NFPA30-1981", National Fire Protection
Association, Batterymarch Park, Quincy, Massachusetts.
"Guide for Inspection of Refinery Equipment", American Petroleum Institute,
Washington, D.C.
"Metals Section - Corrosion Data Survey", Fifth Edition, National Association
of Corrosion Engineers, Houston, Texas, 1974.
"Non-Metals Section - Corrosion Data Survey", Fifth Edition, National Association
of Corrosion Engineers, Houston, Texas, 1975.
"Mark's Standard Handbook for Mechanical Engineers", Eighth Edition, McGraw-
Hill Book Company. New York.
"Petroleum Processing Handbook", W.F. Bland and R.L. Davidson, McGraw-Hill
Book Company, Me* York, 1967.
"Chemical Engineers' Handbook", Fifth Edition, R.H. Perry and C.H. Chilton,
ed;tors, McGraw-Hill Book Company, New York, 1973.
"Manual of Concrete Practice", American Concrete Institute, Detroit, Michigan,
1979.
"Standard Specification for Glass-Fiber-Reinforced Polyester Underground
Petroleum Storage Tanks - ASTM D4021-81", American Society for Testing and
Materials, Philadelphia, Pennsylvania, 1981.
American Society of Mechanical Engineers 1980 Boiler and Pressure Vessel
Code - Section VIII - Pressure Vessels. New York, 1980.
"American National Standard for Welded Aluniinum-Alloy Storage Tanks, ANSI
B96.1-1981", American National Standards Institute, 1430 Broadway, New York
City, New York 10018.
"Oil Storage Tanks with Riveted Shells", API Standard 12A, Seventh Edition,
March, 1941 (reissued September, 1951), American rjetroleum institute, New
York City, New York.
-------
1-7
"Petroleum Refinery Piping - ANSI B31.3 - 1973", The American Society of
Mechanical Engineers, 345 East 47th Street, New York, New York 10017.
"Liquid Petroleum Transportation Piping Systems - ANSI B31.4 - 1974", The
American Society of Mechanical Engineers, 345 East 47th Street, New York
City, New York 10017.
"Steel Underground Tanks for Flammable and Combustible Liquids - UL 5b"s
Seventh Edition, April 1981; Underwriters Laboratories, Inc., 333 Pfingsten
Road, Morthbrook, Illinois 60062.
"Recommended Rules for Design and Construction of Large, Welded, Low-Pressure
Storage Tanks", API Standard 620, Seventh Edition, September 1982; American
Petroleum Institute, 2101 L Street Northwest, Washington, D.C. 20037.
"Steel Above-Ground Tanks for Flammable and Combustible Liquids - UL 142",
Fifth Edition, 1902, Underwriters Laboratories, Inc., Northbrook, Illinois.
"Recommended Practices on Static Electricity - NFPA Code 77", National Fire
Protection Association, Quincy, Massachusetts.
-------
2-1
CHAPTER CONTENTS
2.0 GENERAL PROCESS CONSIDERATIONS
2.1 Process Flow Diagram (PFD)
2.2 Piping and Instrumentation Diagram (P&ID)
2.3 Classification of Hazardous Wastes
2.4 Installation of Outside Above-ground Tanks j"~
-------
2-2
L.Q_ GENERAL PROCESS _CONSI DERM-IONS
The general process considerations presented in this chapter
relate broadly to overall systems factors and cover those subject areas
t. dt do not fit well into other more specific sections of this manual.
Hence, the subject areas have covered a general theme. Process flow dia-
grams (PFD)*, piping and Instrumentation diagrams (P&ID)*, classification
<•'. liquids and hazardous waste (HW), and buffer zone or installation of
outside above-ground tanks are addressed here.
2.1 Process Flow Diagram (PFD)
A review of a process flow diagram and associated text may
serve, depending on the method selected by the originator for presentation
of information, to supply certain required information relevant to the
requirements to be satisfied in terms of a tank, its design, and its probable
performance. The process may consist of a single source of waste, one
input line, and one outlet. The associated diagram could be correspondingly
.-,:,.,ple. Alternatively, the process flow die/gram may show the overall plant
processes and/or sources of a number of wastes and their corresponding
routing to waste storage or treatment processes. The process flow diagram
may thus be of interest in terms of gaining an understanding of the role
of one or more waste storage tanks in terms of overall plant operations.
An example of a process flow diagram is given in Figure 2-1.
In this particular example the information of interest is that for the spent
oil tank and includes direction of flow, operating temperature and pressure,
size and indication of data listings of interest, i.e., 10, 12, and 14 in
the mass balance table included on the flow diagram.
The process flow diagram should be reviewed to obtain a general
orientation to the hazardous waste management system for the plant and
is a possible source or location of data for any of the following factors:
'According to 270.16 (Specific Part B information requirements for tariK
Applicants " . . must provide . . . (d) A diagram of piping, instru-
rnnnfaflrin Anrl nr*nracc f 1 riuj "
. .
, and process flow."
-------
BIMIA
O
Source: Fred C. Hart Associates, INc., 1980
FIGURE 2-1. A SIMPLE PROCESS FLOW DIAGRAM
-------
2-4
1. Basio for siting the tanks (see 3.1.2)
2. Mass balance between inlet and outlet stream
3. Direction of waste stream flow
4. The possibility of mixing incompatible wastes or
their placement in tanks of inappropriate materials
of construction
5. Each item of major equipment (grouping duplicate items
together)
6. The identifying number, name, material of construction,
and critical dimensions, performance requirement, and
capacities for each item or group of duplicate items
7. The required pressure and temperature renditions for each
item or group of items
8. The flow rate, composition, specific gravity, molecular
weight, and properites of each process stream
9. The flow rate and conditions of supply for steam, cooling
water, and other utilities
10. Batch sizes and operating cycles for batch processes.
All of the above information should appear on the PFD, How-
ever, there may be some variations in the preparation of PFDs by the
applicants. Seme of the supporting information such as items 1, 4, 9,
and 10 may be given in the text or on a separate sheet or drawing; but
iterns 2, 3, 5, 7, and 3 may be given in the PFD. The PFD does not
usually include valves and pipe fittings, but it may show major control
schemes.
2.2 Piping and Instrumentation'Diagram (P?JD)
PSIDs are drawings with details of piping and instruments. These
drawings are useful to the process or project engineer for reviewing the
adequacy cf design for fail-safe operation of process equipment. A P&ID
drawn specifically for a tank should contain the following information:
• Each tank with its identification number
• Each process pipe with its identification number, material
of construction, pressure rating code, and size
-------
2-5
• Each valve, by means of a symbol that indicates the valve
type (a code for the symbols should be provided)
* Steam tracing (or jacketing) and steam traps
• All instruments and interconnections between instruments
and controls.
Important items on the P&ID that should be reviewed in accordance
with subsequent sections of this manual by a permit writer regarding tanks
include:
• Level controls
• Pressure controls or vents
• Adequacy of controls to assure that no mixing of
incompatible wastes would occur
t Adequacy of the size of control and vent valves
• Adequacy of the pipe sizes
• Material of construction for valves and piping
0 Types of instruments (manual or automatic).
An example of a simplified P&ID for a storage tank is given in
Figure 2-2. It should be noted that the discussion above postulates that
the applicant would provide a normal PSID including all of the required
information indicated, because a complete P&ID would normally be the
most convenient form of presentation. However, much of the information
required by the permit writer could be presented in alternative formats.
2.3 Classification of Hazardous Wastes
Waste liquids or aqueous solutions are normally stored in tanks
or containers. These liquids may be classified as hazardous or non-
hazardous types. If the liquids exhibit any characteristics of ingitability.
corrosivity. reactivity, or EP toxicity. they are classified as hazardous
waste. These hazardous waste characteristics are defined in 40 CFR 261.20
through CFR 261.24.
A liquid or aqueous solution is considered corrosive if its
corrosivity toward a specific material is greater than 6.35 mm per year or
its pH outside the range of 2 to 12.5.
-------
Note: On noii-simplifled P&IOs
size (Inches), flow rate
(gpm), pressure rating
(pslgi, temperature (CF),
specific gravity, and
materials of construction
will be indicated adjacent
_ to earn pipe.
Source: Fred C. Hart Associates Ii.c., 1980
FIGURE 2-2. A SIMPLIFIED PIPING AND INSTRUMENTATION DIAGRAM
-------
2-7
A liquid or aqueous solution is reactive if re has any of the
following properties.
• Reacts violently with water
c Forms
-------
2-f
"able- 2-1. STABLE LIQUIDS (OPERATING PRESSURE 2.5 psig OR LESS)
(17.24 kPa)
Mlalrnura Dtos>A£« la
F««t from Pi utMl vy Line
Whub !> ar Cui B« Sum
'
Sld« at m
Way asd Shall R« Not
Laaa Tb«t! 5 Faot
MtaJmnm Dtacmaca Us
P®«t from Na*,.-aaf Slda «
'm- Public Way or from
th« Sam*
Shall B«
5 F«»c
Eoaf
2-2.1.!(»)!
diameter of
teai
NCTSC
Dia»«ftt., ex' IMUI but
freed no! exceed ' 7S
fast
er erf
tanfe
ft-iam or
U*3tUl£
Vt reicaJ mtctn oo Hi omet diameur erf
irntJi '.arita not t«ni
^LT •> U €StCOCdjJltf
a^ol- ISO feet in
to "^ "~*
l±l Protecooo
r tor Diameter of t-^nfr
(jd£ f v
2^ » 1 \ CcfpQVUTCI
•*. 1.1)
2 anxa di&meter erf tAnJs
NODC but oeed not '.ixced 350
feet
Keciioiuai LT^rrtinf
Ve^a] ti*l*iU u _ _
H Dma dimmeter erf
tmnk
H ctmea diajneter erf
tmntf
H ama diajneter
erf tuui
^ nmma Tal-vir ">-<,
Hebef
Veaonf
To Umu
r'rcarara
ProcDr&on
far
EjqxmMTi*
Tabk 2-6
NODE
2 ama TatWe 2-6
2-6
SI Unil. ! fi . 0 JO48 m
"Ser drfinttton foe "Prwrnton ior £*po»um "
"For unkj wwr 1M fi m dumnrrutc Pnxmion for F.jpoium 01 None
Reprinted with permission from NFPA 30-1981, Flammable and
Combustible Liquids Code, Copyright® 1980, National Fire
Protection Association. Quincy, Massachusetts 02269. This
reprinteO material is not the complete and official position of
the NfPA on the referenced subject, which is represented only by
the standard in its entirety.
-------
2-9
TABLE 2-2. STABLE LIQUIDS (OPERATING PRESSURE GREATER THAN 2.5 psig)
(17.24 k ~'
Minimum DUtmnoi In Minimum Ducua la
TI9* <* p~~-,,,_ Which It'w On B« Built Ajir Public »«y «r lr*m
Tuk ' »»l—-l»« L'poo. lacludln* th« N«ar»«( Impormaf
"|i|nMii SJ3« at • Fubtlc luJldLnf. on th« Jum
W«y Plov« lr
Protection 1 4 ama TibJe 2-6 but 1 '•$ omei T»bJe 2-6 but
[or >haH not be le» fhin tiuul aot be leu thu
25 ton 25 feet
3 uma Ttble 2-4 but 1 H nmrt TibJe 2-6 but
None ihiil cot be le» thic ih*H aot be lea Uv»c
SO feet 2i fact
SI L'nri 1 ft - 0 ?O«J m
'See Dcnruooa for " Protection for EjqK»urc«."
TABLE 2-3. BOIL-OVER LIQUIDS
Minimum Diacm»c« ui Maximum I
F*«t from FropMTy Lln« F*»t fro«n ,N««r«BC 14^0 «tf
Which !• or C&n B« Built Any P\jbU< Way or fr««B
Om>aM(« &id« atf • Public
way •ad ^ull B« >oi
L«IM Torn* A ?Mf
Protccuoa
for t
[See
2-2.1.!(.)) Nooe Dumettroiuni H Qmcs diimetrr rf
r*nk
Duunerer
-------
2-10
TABLE 2-4, UNSTABLE LIQUIDS
Tvp« at
tiak
Minimum Di*u.ac* la Minimum CHitaoc* la
?#•( from Property Lio« !•'••( Irom ,N*ar«*c S44« a/
Which It or O*n B* B lit \at Public Way at frc*m
Upon, (.icludluj ttat S*ar««( Imrcsrtsai
Oppc*U* £id« at • Public Building oo tbe S=»rn»
Way
Tani
cay me
Horwon- °f ^=
^ ,od foUW-TJlg.
'j'c;fca^ Appso/ed
rlaiu vmier^iay.
wub, App.ov.-d
A 4.
Table 2-b but DOS less
ihs.r> 25 feet
Not lem ehio 25 feti
ftilief
Ventuo^
o Permit
Prmure
No« in
^..ce.. of
refnyeriuoo,
Approv-ed
Protection
Tifck
but
Noi l«e th
50 feet
None
5 qrp«T Table 2-^S but
not leu man 100 feet
Not
than 100 £ect
T»ak
protected
with
aoy one
of the
foiJowin^ •
A ppro^ed
- ama Tible 2-6 ''ut
act it-* ch*n 5<> reev
NCT i
Elmer ~
Approves!
u> Pe
PreMorc
Over
Approved
fVo^no0
4 ama Tuble 2-6 but
oo* lex unn 1 (Xi feet
Ncx ten than 100 feet
8 a m
no* le
T*bJc 2-6 wjt
Ui»n 1 SO feet
Ncx
UXKO ISO feet
SI i'run I ft * 0 3048 m
'See definjcun for "Prateenon for Elxpc«una '
Reprinted with permiscloii from NFPA 30-1981, Flamable and
CcfrDustit)ie Liquids Code, Copyright© 1980, National fire
P-otection Association, Quincy. Massachusetts 02269. This
repnnted mate-'ial is not the complete and official position cf
the NfPA on the referenced subject, which is represented only by
the standard in its entirety.
-------
2-11
TABLE 2-5. CLASS >IIS LIQUIDS
Minimum DtfttAac* IB
r*»«t from Prop«rTy L^ja*
Which li or Can frt Built
Upon. locludLai (b«
W.r
Minimum CHtranc* tB
F*»t from NMTWI S*4« at
\ay PubUc Wty
-------
3-1
CHAr-TER CONTENTS
3.0 STANDARD METAL TANK DESIGN
3.1 General
3.1.1 Regulations
3.1.2 Basis for Tank Design
3.1.2.1 Properties of the Waste
3.1,2.2 Operating Conditions
3.1.2.3 Sizes of Nozzles and Fittings
3.1.2.4 Suirmary Checklist on Tank Design Basis
3.1.3 Applicant to Specify Tank Standards
3.2 New Metal Tanks
3.2.1 Slanaard Codes
3.2.1.1 API Standard 620
3.2.1.2 API Standard 650
3.2.1.3 NFPA 30-1981
3.2.1.4 API 12B
3.2.1.5 API 12D
3.2.1.6 API 12T
3.2.1.7 API 12A
3.2.1.8 ANSI Standard B96.1
3.2.1.9 UL 142
3.2.1.10 UL 58
3.2.1.11 ASME Section VIII Division I
3.2.1.12 ASME Section VIII Division 2
3.2,2 Tank Materials
3.2.3 Tank Fabrication and Erection
3.2.4 Tank Wall Corrosion Allowance
3.2.5 Tank Wall Stress
3.2.5.1 API 520 Tanks
3.2.5.2 API 650 Tanks
3.2.5.3 UL 58 anU 142 Tanks
3.2.5.4 ASME Section VIII Pressure Vessels
3.2.6 Minimum Thickness, Corrosion Allowance, and
Service Life
-------
3-2
CHAPTER CONTENTS
CHAPTER 3 (Continued)
3.2.6.1 Minimum Shell Thickness
3.2.6.2 Corrosion Allowance
3.2.6.3 Expected Service Life
3.2.6.4 Examples
3.2.7 Tank Openings
3.2.7.1 Tank Openings in API 620 Tanks
3.2.7.2 Tank Openings in API 650 Tanks
3.2.3 Tank Diagrams and Data Sheets
3.2.9 Inspection and Evaluation of Welds (Seams)
3.2.9.1 Tanks Built to Standards
3.2.9.1.1 Used Tanks
3.2.9.2 Tanks Not Built to Standards
-------
3-3
3.0_j.IA!iPARD METAL TAfJ< DESIGN
Many tanks to be used for storage and treatment of hazardous
t
wastes are likely to have been fabricated from met'.Is using the standards
for design developed by association or societies of industry groups,
insurers, or engineers. The primary purpose of Chapter 3.d of this manual
is to present the standards used during the fabrication of the common
metal tanks likely to ba encountered by parent writers. Chapter 4.0
presents similar information for non-metallic tanks and an approach on
how to develop permits for used metal tanks or non-specification metal
tanks.
Th-'s chapter starts with a general section on the regulations
and issues to be considered in permitting a tank. Some of the issues in
preparing the basis for tank design by the process engineer for use by
the tank design engineer are then discussed. It is also noted that the
applicant is required to specify the standards or equivalent information
used to design and fabricate the tank. The subsequent section 2.2 pre-
sents abstracts of the various codes or standards used to design metal
tanks, which is then followed by details on tank materials, fabrication,
corrosion allowance, tank wall stress, and tank openings.
If tha hazardous waste facility is to use new standard metal
tanks, then the permit writer does not need to use Chapter 4.0. But, if
a used standard metal tank or a new or used non-standard metal tank is or
will be used in a hazardous waste facility, then the permit writers would
likely refer to both Chapters 3.0 and 4.0.
3.1 General
This section of the manual covers information specific to the
design (or selection) of tanks for use in hazardous waste facilities;
Chapter 2.0 covered information with a more general "systems" orientation
which pertained less to the design of the tank and more to either the
environment of the tank or information which did not fit well in Chapter 3.
-------
Subjects covered in this section include:
• Regulations pertaining to tanks
0 Basis for tank design
• Requirement that applicant specify tank standards
or design basis.
3.1.1 Regulations
The applicable regulations for design, fabrication, installation,
operation, and closure of tanks at hazardous waste facilities are contained
primarily in 40 CFR 264.190 through 264.199 and 270.16. A regulatory
analysis of tanks in outline format is presented as Appendix A. Each of
the specific items required in the regulation have been listed with
(a) The reference to the specific regulatory section and
(b) The preferred item designation of the permit application
outline as given in "A Guide for Preparing RCRA Permit
Applications for Existing Storage Facilities".
3/1.2 Basis for Tank Design
In the design of a tank, the designer takes into account the
factors covered in the following sections of the chapter. The principal
and initial factors to be considered are
• The amount and certain properties of the material to be
contained, principally
- the specific gravity
- vapcr pressure
- corrosion behavior
0 Type of service, i.e., operating conditions for the
tank, (e.g., access requirements), connections required,
and operating temperature range.
The corrosion behavior of the liquid influences materials selctions, e.g.,
carbon steel, painted, coated or lined carbon steel, stainless steel, etc.
The specific gravity of the liquid influences the hydrostatic pressura in
-------
3-5
i
\
i ,j tsnK, Trie vapor pressure determines the selection of an open or closed
;;.r,k, naed for venting and/or vapor control. The operating temperature
rrige defines needs for low-temperature ductility, (i.e., no cold weather
brittleness), and connections and access determine the nesd for welded
connections and access ports, supports, etc. Once these major factors
are defined, the majority of tanks can be specified in terms of existing
exoerience, a large amount of which has been assembled in various codes
and standards. Some standards or codes are stated in terms of design
procedures, e.g., a set of steps using values from various tabulations of
data; other standards or codes are stated in terms of final specifications,
e.g., a range of conditions are described and final specifications (e.g.,
tank wall thickness) is given.
Similarly, standards have been written for the procedures for
fabrication and construction, inspection and testing of tanks. These
existing standards, developed by concensus and experience over a period of
time, usually deal with the welding of tanks. Such standards are only
recently available for fiberglass-reinforced tanks.
The following sections of this chapter discuss each factor in
tank design and give br'ef descriptions of many of the commonly used
standards and codes.
The remainder of this section will address
• Properties of the waste
• Operating conditions
• Nozzles and fittings.
3.1.2.1 Properties of the Waste.' Section 2.3 previously pre-
sented the factors used to classify wastes as hazardous including toxicity,
reactivity, corroslvity, and ignitability. Although these factors are
important in the selection and design of tanks, two other properties should
also be considered:
• Density (or specific gravity)
• Vapor pressure at maximum anticipated storage tenperature.
-------
3-6
As indicated in Table 3-1, "Impact of Selected Properties of
the Waste on Tank Design", these factors are used to determine if the
tank should be enclosed, if the proper materials of construction have
been selected, and to calculate the thickness of the tank.
3.1.2.2 Operating Conditions. The operating conditions that
are important in designing a tank for hazardous waste storage include:
• Pressure
t Temperature
• Liquid level.
The shell of a tank should be adequate to withstand specified
design pressure. This design pressure is a function of the working pres-
sure of the tank. If the tank is open to the atmosphere, even if through
a small tube, then the working pressure is dependent only on the height
and density of the liquid in the tank. For example, if the liquid height
is 20 feet and the density of the liquid is 62.4 pounds/cubic foot (the
same as water), then the pressure at the bottom of the tank is
20 feet x 62.4 pound: 20 feet , 62.4 pounds 1249 pounds
cubic foot
cubic foot square foot
or, if pounds per square inch (psi) is desired,
20 feet 62.4 pounds
cubic foot
feet
144 square inches
8.77 psi
Alternatively, if the liquid to be stored in a tank open to the atmosphere
were some mixture "A" with a specific gravity of 0.93, then the pressure
in psi could be calculated as follows:
Density of "V « 0.93 x 62.4 pourds = 58.0_pounds
cubic foot cubic foot
i
20 feet 58 pounds scuare foot 3 3.1 :s
and pressure *
cubic foot i44 square, incnes
-------
3-7
TABLE 3-1. IMPACT OF SELF.CTED PROPERTIES OF THE
WASTE ON TANK DESIGN
Property of Waste
Impact on Tank Design
Reactivity
Toxici ty
Corrosiveness
Ignit?bili ty
Density (or specific gravity)
Vapor pressure (at maximum
storage temperature)
None on storage tank unless reactive
to water or carbon dioxide in the
air, in which case the tank should
be enclosed.
Tank should generally be enclosed
(unless toxic components are not
volatile or components are of low
volatility and are not toxic at low
concentrations).
A material of construction for the
tank must be selected that has a low
corrosion rate>or an effective liner
or coating material must be used that
is compatible with the waste (and
operating conditions).
Generally, steel must be used for
the t
-------
3-8
However, if the tank is to be enclosed, then the pressure at the top of
the tank will become at least equal to the vapor pressure of the material
in the tank. For example, if the material "B" could be expected to reach
a maximum of 90 F due to sunlight and ambient temperature during the day
and its vapor pressure at 90 F were 2 atmospheres (absolute), then the
pressure at the top of the tank would be
2 atmospheres absolute less 1 atmosphere = 1 atmosphere gauge*
— : — EU —
atmosphere
and 1 atmosphere gauge x — : — EU — - 14.7 ps-j gauge = 14.7
30 feet
50 pounds
cubic foot
square feet
144 square inches
In the above situation, if the density were 50 pounds/cubic foot and the
liquid height were 30 feet, then the pressure at the bottom of the tdn
could be calculated as
i4.7 psig
14.7 = 10.4 - 25.1 psig.
It should be noted that under a variety of conditions the pressurf: of
a closed tank may exceed the values calculated above. For example, the
pressure would be higher if air were originally trapped above the liquid.
Strength of material is also a function of temperature, with
the strength of materials declining as temperature increases.. Howeve-,
the effect of temperature neea not be considered for metals unless it
exceeds 300 F (in which case, the applicable codes should be referred to
'Vapor pressures of liquids are measured starting at zero absolute
pressure. However, tank design is based on the difference: between
atmospheric pressure and the pressure in the tank.
-------
3-9
oy tnc ps.TTiit vinter).* Some caution should also be applied to use of
mo".enal:; such as rubber, plastics, end fiberglass-reinforced polyester
materials if the maximum temperature exceeds about 120 F.
3.1.2.3 Sizes of Nozzles and Fittings. In some cases, the
permit application r^ay not present a sufficiently detailed' tank diagram
to a "Mow a complete determination of all nozzles and fittings on a tank.
Furthermore, nozzles to be used for filling and emptying the tank during
operations would seldom create hazardous situations.
The size of any overflow outlet (a port or pipe) should be
than any inlet. For example, waste may be pumped into a tank
under some condition of pump pressure and flow rate determined by pump
character! .tics. Any overflow will occur without pump pressure. There-
fore, the overflow outlet should be larger than the inlet because, at
overflow conditions, the overflow rate must accommodate the pump rate,
but at lower pressure. A similar situation exists for vent and other
pressure relief nozzles which must be sufficiently large to hai.dle the
maximum flow anticipated; furthermore, such nozzles should be used only
for the purpose of venting and pressure relief.
It ',3 beyond the scope of this manual to present the complex
fluid flow equations to actually verify the design of vent and overflow
nozzles. The permit writer should assure himself that such nozzles were
designed instead of '"guessed".
In general, vent pipes must be no less than 1-1/4 inches inside
diameter (see NFPA 30, section 2.24) and may vary with tank size up to
4 inches in diameter for gasoline tanks in the size range of 35,000 to
50,000 gallons (UL 1316). These noted sizes are not universally applicable
since vent size is dependent on vapor pressure, heating conditions, pumping
rates, and other factors.
*The use of the value of 300 F here is a conservative judgment; the
existing standards for tank design dealt with here do not include any
recognition of service at elevated temperature; it iu judged that tank
steels would undergo negligible change of properties up to 300 F.
-------
3-10
3.1.2.4 Surmary Checklist on Tank Design Basis. A "Summary
Checklist for Tank Design Basis" is presented as Table 3-2.
3.1.3 Applicant to Specify Tank Standards
The applicant must specify the specific standards used for the
tank design and the date of the applicable standard. Much information
about the general applicability of the tank for the storage of hazardous
waste is disclosed through knowing the applicable tank standard or code.
Non-standard tanks (such as rectangular tanks) have not been
disallowed from use in hazardous waste facilities but, in such cases
the Regional Administrator must be presented sufficient information to
support the conclusion that such a tank has been adequately designed.
The only source of such information is the applicant. The permitting of
non-standard tanks normally will require significant engineering analyses
to verify that such tanks can safely be used in a hazardous waste facility.
3.2 New Metal Tanks
This section of the manual deals with the standards and codes
used for the fabrication of new standard metal tanks most likely to be
encountered in hazardous storage and treatment facilities.
Specific subjects covered include:
• Standard codes
t Tank materials
• Tank fabrication and erection
• Tank wall corrosion allowance
• Tank wall stress
t Minimum thickness, corrosion allowance, and service life
« Tank openings
t Tank diagrams and data sheets.
The most common metal tanks likely to be used in hazardous waste
facilities are those fabricated according to API Standard 620 for up to
-------
3-11
TABLE 3-2. SUMMARY CHECKLIST FOR TANK DESIGN BASIS
Note: The answer to ail questions should be 'yes" or "not ?oplicable"
1 I f the waste is toxic or ignitable, is ttv; tank enclosed'.' ___
?.. If 'che waste is reactive to water or carbon dioxide (from
the a"r),is the tank enclosed or under cov,»r?
3. >ds the tank been enclosed or covered if rain might over-
fill the tank?
4. Have materials of construction been carefully selected
considering corrosivity and compatibility of the waste?
5. If the waste is ignitable, is the tank shell constructed
of steel?
6. Has liquid hfiqht and its density been used in calculating
the she!1 thickness?
7. If the tank is enclosed, has the vapor pressure of the waste
been considered in calculating shell thickness?
8. If the tank is stee- and the maxir.sim operating temperature is
greater than 260 F, h.as this been considered in calculating
sneii thickness?
9. If the tank or its liner or coating is rubber, plastic,
fiberglass-reinforced plastic, or a paint, and tne maximum
operating temperature is greater than 120 F, har. this been
carefully evaluated as 5eing safe?
10. Is the general capacity of the tank adequate to handle
operational delay*:?
11 Is it likely tnat overfill and vent or pressure relief
nc?^;es have been designed sufficiently large to perform
their function?
12. Is there significant potential liquid height (several
feet) above overfill nozzles to avoid undesirable spills?
-------
3-12
15 psig, API Standard 650 for up to 2.5 psig, UL Standard 142 for above-
ground storage of flammable materials up to 0.5 psig, and UL Standard 58
for underground storage of flammable materials, lanks fabricated in
accordance with ASME Section VIII Division I and Division II for pressure
vessels operating greater than 15 psig may occasionally be used in hazardous
waste facilities when in new condition, but are more likely to be derated
after having been used in other applications for use in hazardous waste
storage at low pressure (lass than 15 psig). NFPA Code 30 for flammable and
and combustible liquids is not really a tank design standard, but covers
other aspects of storage for such materials. Other codes and standards
which are described briefly but would seldom be applicable to hazardous
waste facilities include API Standard 12B for bolted production tanks,
API Standard 12D for large production tanks, API Standard 12F for small
oil-field serivce, API Standard 12A for tanks with riveted shells, and
API Standard 1396.1 for welded aluminum-alloy storage tanks.
3.2.1 Standard Codes
Steel tanks intended for use in the petroleum or chemical process-
ing industries sr3 ordinarily specified tc "oet certain code: or standards,
such as (.odes or standards which have been developej by the American °etroleum
Institut;; (API), the American Society of Mechanical Engineers (ASME), the
National Fire Protection Association (NFPA), or the Underwriters Laboratories
(UL). B.-ief descriptions of standards most frequently encountered are
gi ven be Iow.
3.2.1.1 API Standard 520
Title: "Recommended Rules for Design and Construction of Large,
Welded. Low-Pressure Storage Tanks"
Scope: Rules cover design and construction of large, welded, ]_ow_-
pressure. carbon steel, aboveground tanks which have a
single vertical axis of revolution and are to be operated
at netal temperatures of 200 F or less and pressures 1n
their gas or vapor spaces greater than permitted by AF!
Standard 650 but not exceeding 15 psig. The rules prcv ze
-------
3-13
for installations in areas where the lowest recorded
one-day mean temperature is as low as -50 F. Some
low alloy steels are also covered in the API 620
appendices.
3.2.1.2 API Standard 650
Title: "Welded Steel Tanks for 011 Storage"
Scope: This standard covers material, design, fabrication,
erection, and testing requirements for vertical, cylindrjcaj_,
abgvegrsund, closed and open top, wiided_s_teej_ storage
tanks in various sizes and capacities for internal pressures
near atmospheric pressure up to 2.5 psig. For tanks with
open tops, floating roofs, or with bolted door sheets,
metal operating temperatures shall not exceed 200 F; for
certain shell materials and design features, metal
operating temperatures may- range up to 500 F. The standard
covers only non-refrigerated service.
3.?.1.3 NFPA 30-1981
Title: "Flammable and Combustible Liquids Code" - 1977
Scope- The code applies to all flammable and combustible liquids
except those that are solid <»t 100 F or above. The code
contains separate chapters on tank storage; piping, valves,
and fittings; container and portable tank storage;
•industrial plants; bulk plants; service stations; pro-
cessing plants; and refineries, chemical plants, and
distilleries. Rules for storage tanks concern osoects
of tank materials, linings, fabrication, design standards,
installation, site requirements, venting, and cont,-ol of
spillage.
Note that NFPA 30 is not a design standard for tanks, but
prescribes which design standards may be used, and pro/ides
certain requirements or recommendations on the aspect?
noted above.
O
-------
3-14
3.2.1.4 API 12B
Title: "API Specification for Bolted Production Tanks"
Scope: Specification covers material, design, and erection
requirements for vertical cy'l indrical , aboveground, bol ted-
steel , production tanks in nominal capacities of 100 to
10,000 bbl for oil-field service. It also includes
appurtenance requirements. Operating pressures will be
near atmospheric pressure.
3.2.1.5 API 12D
Title; "API Specification for Large Welded Production Tanks"
Scope: Specification covers material, design, fabrication, and
erection requirements for vertical cylindrical, aboveground,
welded-steel, production tanks in nominal capacities of
500 to 3000 bbls for oil-field service. Operating pressures
will be near atmospheric pressure.
3.2.1.5 API 12F
Title: "API Specification for Small Welded Production Tanks"
Scope: Specification covers material, design, and construction
requirements for vertical cylindrical . aboveground, shop-
welded steel production tanks in nominal capacities cf
90 to 500 bbls for oil-field service. Operating pressures
will be near atmospheric pressure.
3.2.1.7 API 12A
Title: "API Specification for Oil Storage Tanks with Riveted
Shells"
Scope: API 12A tanks are flat-bottomed, vertical cylindrical
tanks designed to operate at atmospheric pressure. The
specification includes design specifications for materials;
shell, roof, and bottom; fabrication and erection.
Materials are ASTH A7 and A10 open hearth steel only.
The designs include standard sizes from ?40 to 255,OCC
bbl.
-------
3-15
The 12A specification is not listed in the 1983 API
Publications Catalog; a copy recently obtained from API
was marked "historical" and was issued in 1951. Because
riveted tanks are not expected to be commonly encountered,
no further information is presented here.
3.2.1.8 ANSI Standard B96.1
Title: '|_Ajrierican National Stardar_d_fg_r Uelded Aluminum-Alloy
Storage Tanks"
Scope: This standard covers the design, fabrication, erection,
inspection, testing of welded aluminum-alloy, field-
erected or shop-assembled, above-ground, vertical cylin-
drical , flat-bottomed, atmospheric storage tanks of
open- and closed-top construction. The design temperature
covers the range from -20 F through +400 F. Typical
nominal sizes range from 168 bbl to very large capacities.
Aluminum storage tanks will normally not be used because
of their higher cost and poor corrosion resistance in
many applications. Therefore, no further information is
presented here.
3.2.1.9 UL 142
Title: "Steel Aboveground Tanks for Flammable and Combustible
Liquids"
Scope: UL 142 requirements cover horizontal and vertical welded
Steel tanks Intended for the storage aboveground of
flammable and combustible liquids at pressures between
atmospheric and 0.5 psig. They are intended for use with
only non-corrosive, stable liquids that have a specific
gravity not exceeding that of water. Tanks covered by
these requirements are fabricated, Inspected, and tested
for leaks before being shipped from the factory as com-
pletely assembled vessels. They are intended to meet the
requirements of NFPA 30. Tanks shall be constructed of
commercial or structural grade carbon steel or of Type 304
or 316 stainless steel, per soecificatiors.
-------
3-16
UL Standard 142 tanks are specified with little or no
corrosion allowance, but such an allowance may be added.
In general, the standard provides specifications and not
a design procedure.
If inspection of a UL 142 tank results in the finding
of significant corrosion, then the tank should be repaired
or taken out of service unless a corrosion allowance
was provided when the tank was fabricated.
The standard has been included for reference; no further
discussion is oresented here.
UL 142 contains no specifications, recommendations, or
commpr.cs regarding the number, detailed design, or pi .ce-
ment of supports for either horizontal or vertical tanks
built according to this standard.
3.2.1.10 UL 58
Title: "Steel Underground Tanks for Flammable and Combustible
Liquids"
Scope: UL 58 requirements cover horizontal cylindrical,
atmospheric-type, welded steel tanks, Intended for
Installation and use 1n accordance with NFPA No. 30, the
Fidmnable and Combustible Liquids Code, and NFPA No. 31,
Standard for the Installation of 011-Burning Equipment.
These tanki are fabricated. Inspected, and testeu for
leaks before shipment from the factory. Capacities,
dimensions, and metal thicknesses are specified in tables
1n the Standard. The steel shall be new, cotrmerclal
quality, uncoated or galvanized, and of good welding quality.
-------
3-17
In many respects, UL, Standard 58 is similar to UL Standard
142; i.e., it presents specifications for the tanks and is
not a design procedure. The Standard is not explicit
regarding corrosive service; therefore, it is presumed that
specified plate thicknesses include no corrosion allowance.
Manholes are permissible on the tanks; therefore, 40 CFR
264.190(b) may, or may not, be applicable, which states
"The regulations of this Subpart [Subpart J—Tanks] do not
apply to facilities that treat or store hazardous wastes
in covered underground t&nks that cannot be entered for
inspection." Although the standard has been included for
reference, no further discussion is presented here.
If inspection of a UL 58 tank results in the finding of
significant corrosion, then the tank should be repaired
or taken out of service unless a corrosion allowance was
added when fabricated.
3.6.1.11 ASME Sectic i VIII Division I
Title: "Rules for Construction of Pressure Vessels"
Scope: The rules In this Division of Section VIII cover minimum
construction requirements for the design, fabrication,
inspection and certification of pressure vessels other than
those covered 1n other Sections and other exceptions. Sub-
section A covers the general requirements applicable to all
pressure vessels. Subsection B covers the specific require-
ments that are applicable to the various methods of fabrica-
tion: welding, riveting, forging, and brazing. Subsection
C covers specific '-equirements applicable to several classes
of materials: carbon and low-alloy steels, non-ferrous
metals, high-alloy steels, cast f»"on, clad and lined materials,
cast nodular iron, and ferritic steels. The rules have been
formulated on the basis of design principles and construction
practices applicable to vessels designed for pressures up tc
30CO psi. For pressures above 3000 psi, deviations from and
-------
2-13
additions to these rules are necessary to meet the reqirre-
ments of design principles and construction practices for
these higher pressures. The design temperature shall not
be less than the mean metal temperature (through the thick-
ness) expected under operating conditions; in no case shall
the surface temperature exceed the maximum temperature
listed in the stress tables for materials nor exceed
temperature limitations specified elsewhere in Division
I of Section VIII.
Corrosion service is covered by ASME Section VIII, Division
I, Appendix E, "Suggested Good Practice Regarding Corrosion
Allowance", and by ASME Appendix F, "Suggested Good Practice
Regarding Linings". In the former, paragraph UA-156 states
that "v,hen. the rate of corrosion is already predictable,
additional wall thickness . . . shall be provided, which
shall be at least equal to the expected corrosion loss
during the desired life of the vessel". Paragraph UA-157
states that when the corrosion effects ^rc indeterTiiiiialP
prior to design of the vessel, or when corrosion is inci-
dental, localized, and/or variable in rate and extent,
the designer must exercise his best judgment in establishing
a reasonable maximum excess shell thickness. Paragraph
UA-159 suggests that, when a vessel goes into corrosive
service without previous service experience, service
inspections be made at frequent intervals until the nature
and rate of corrosion in service can be definitely
established.
3.2.1.12 ASME Section VIII Division 2
Title: "Alternative Rules for Construction of Pressure Vessels"
Scope: The scope of Division 2 is similar to that of Division 1
as far as design pressures, design temoeratures, etc.,
are concerned. The rj"'es of Division 2 are nore restnrv.vc
in the choice of materials whp'ch may be 'jsed, •"ore
-------
3-19
design procedures are required, some common design
details are prohibited, permissible fabrication
procedures are specifically delineated and more com-
plete examination, testing, and inspection are required.
3.2.2 Tank Materials
Each code or design standard has specific materials requirements
either explicitly or by reference to material standards such as ASTM.
API Standard 650 daals with materials requirements in Section
2. These requirements are enunciated separately for plates, sheets,
structural shapes, piping and forgings, flanges, bolting, and welding
electrodes. A most important aspect of the requirements is the concept
of design metal temperature. In API 650 the steel plates used for the shell
of a tank must meet certain minimum values of toughness as exhibited by
specified procedures (Charpy V-notch tests) depending on the lowest one-day
mean temperature at the srte of the tank. These temperatures are shown in
Figure 2-1 of the API 650 for the whole United States. The permissible
design metal temperatures are shown in Figurs 3-1 for all of the groups
or candidate steeis (defined in Table 3-3), As an example, Figure 3-1
shows that, in a piace where the design metal temperature is -30 F, plates
as thick as 0.50 inch could be selected from Group VI; Group VI includes
eight different />STM specifications. See Section 2 of API 650 for details
of specifications referred to above.
The API 620 materials specifications are qualitatively similar to
those of API 650, just described. For details see Section 2 of API 620.
NFPA Code 30, "Flammable and Combustible Liquids Code", generally
requires that tanks storing flammable or combustible liquids be fabricated
of steel, but provides several exceptions and limitations as follow:
(a) The material of construction used for tank fabrication
must be compatible with the flammable or combustible
liquid.
(b) If the tank is constructed of a combustible material,
its use must be approved by the appropriate authority
and is limited to one of the following uses:
-------
3-20
-60
0.25 050 0 75 10 1.25
PLATE THICKNESS INCLUDING COHPOSlON ALLOWANCE. INCHES
1 50
Motes
1 See T»bls 2-3 for mttcnili in e«cti group.
2 Figure 2-2ijnoi«pplic»bleioconirolled-rolledp(»tei(»e«2.:.7 4).
FIGURE 3-1. MINIMUM PERMISSIBLE DESIGN METAL TEMPERATURE FOR PLATES
USED IN TANK SHELLS WITHOUT IMPACT TESTING (IN DEGREE
FAHRENHEIT)
API Standard 650, Welded Steel Tanks for Oil Storage, Seventh Edition,
1960. Reprinted by courtesy of tne American Petroleum Institute".
-------
3-21
TABLE 3-3. MATERIALS GROUPS (See Figure 3-1)
Group 1
As-rolled
Semi-killed
Material Note*
A 283 C
A 285 C
A 131 A
A 36 2
Fe 42 B
Or 37 3. 4
Gr 41 4
Group IV
AJ- rolled
Killed
Fine Grain Practice
Material Noiei
A 573-65
A 573-70
A 516-65
A 516-70
A 662 B
G 40 21-44 T
G 40 21-50T
F- 44 B. C. D 7
*- 32 C. D 7
Gr .44 4. 7
Group 11
A*- roiled
Kjlled or semi-killed
Material Notes
A 131 B
A 36 5
A 442-55
A M7-60
G 40.21-38 W
G 40.21-44 W
Fe 42 C
Gr 41 . . 4. 6
Grass? fVA
Aj-roikd
lOUed
Fine Grain Practice
Material Notes
A 662 C
A 573-70 Mod .... 9
G 40.21-44 T . . . 9
G 40.21-50 T . 9
Group III
A*- rolled
Kjlled
Fine Grain Practice
Maienai Notes
A 573-58
A 516-55
A ; 16-60
G 40.21-38 T
Fe 42 D 7
Gr 41 4, 7
Group v
Nomuued
KJIled
Fine Grain Practice
Material Notes
A 573-70
A 516-65
A 516-70
G 4021-44 T
G 40.21-50 T
Group MIA
Normalized
Killed
Fine Gram Practice
Material Notes
A 131 CS
Group 111
Materials 8
Group VI
Normalized or Quenched
and Tempered
Killed
fine Gram Practice
Reduced Carbon
Material Notes
A 131 EH 36
A 6i3C
A 633 D
A 537 1
A 53' II
A 678 A
A 678 E
A 73^ 3
1 All specification ,iumcen refer to ASTM specifications except G
40 21 which is a Canadian Standard* Association specification: Fe 42.
Fe 44. and Fe 52 which are contained in ISO Recommendation R 630;
and Gr 37. Gr 4|. and Gr 44 which refer to national standards.
2 Limited to 0 50 men t.hickneu unless manganese content modified
per 2 2 2 in wmch case it is limited to 1 inch tlucknca.
3 Maximum thickness 0 50 inch.
4. Maximum ihkknew 0.75 inches when control rolled
5 Manganese content modified per 2.2.2.
6. Must be lulled.
7. Must be lulled and fine grain practice
8. MUJU be oormaiued.
9. Musi have chemistry (heat) modified to carbon mammum of 0 20
and iniii|»»i»tf maximum of 1.60 (tee 2.2.6.4).
API Standard 650, Welded Steel Tank for Oil Storage. Seventh Edition, 1980,
Reprinted by courtesy of the American Petroleum Institute.
-------
3-22
(1) underground installation
(2) where required by the stored liquid'; properties
(3) above-ground storage of Mquid'with i flash point
greater than 200 F with no potential for a spill
or leak in the area from a liquid with, a flash point
less than 140 F
(4) Storage of liquid with a flash point greater than
200 F inside a building with an approved automatic
fire extinguishing system
(c) Concrete tanks may be used as follows:
(1) Unlined, if the API gravity is 40 or heavier
(51.4 pounds/cubic foot)
(2) Lined, if the API gravity is less than 40 and
the tank must have been designed using sound
engineering practices.
3.2.3 Tank Fabrication and Erection
The topics of fabrication and erection in the design standards
generally are concerned with workmanship; tolerable deviations of tank lines
and dimensions from plumb, roundness, etc; deviations of curved surfaces
from design sha, ?; adequacy of bearing strength of foundation; methods of
shaping of plates not to affect mechanical properties; qualification of
welders and welding procedure; and related items. In addition, they cover
inspection and testing.
The design standards have detailed, specific requirements for
inspection of welds - visually, by radiography, by sectioning, by leak
testing with vacuum, air pressure, or reverse water pressure; for repair of
welds; and, finally, for hydrostatic testing of the tank shell, including
concurrent inspection for leaks. If the tank is to be a closed tank, the "o
must also be tested for leaks by application of internal gas pressure
use of soap film or similar detector.
-------
3-23
For more specific and detailed information, see the appropriate
sections of the standards, as follows:
Standard 650: Fabrication Section 4
Erection Section 5
Methods of Inspecting Joints Section 6
Standard 620: Fabrication Section 4
Inspection and Testing Section 5
3.2.4 Tank Wall Corrosion Allowance
If a tank wall will be exposed directly to a corrosive liquid,
i.e., P.O liner or coating and, therefore, is expected to corrode over a
period of time, then a corrosion allowance must be made in the total wall
thickness. Thus, the total initial minimum wall thickness t can be
considered to have two components:
tc = the corrosion allowance
ts = the thickness required to carry the stress caused
by the pressure.
The total initial minimum thickness t - tc + ts. Methods and data required
for estimating tc and ts are given in later sections (3.2.5.1 and 3.2.6.4).
3.Z.5 Tank Wall Stress
The stress in the steel wall of a vertical cylindrical tank con-
taining a liquid or a gas or vapor under pressure will be tensile in the
horizintal (;hoop) direction (due to liquid head and gas/vapor pressure) and
generally, for low pressure tanks, will be co;npressive in the vertical
direction (due to the weight of the wall itself, plus the weight of the
roof resting on the wall). The compressive stress at the bottom of a
uniform-thickness wall, due only to the weight of tha steel wall itself,
will be about 3.4 psi per foot of height.* This will usually be a small
'Calculated on the basis of a density of steel of 0.28 pounds per
cubic inch.
-------
3-24
fraction of the tensile circumferential stress in the wall of a tank
operating at its design pressure, especi:lly for the small tanks used
to store hazardous liquids.
3.2.5.1 API 620 Tanks. As indicated in 3.2.1.1, API Standard
520 covers the de?1gn of tanks with a single vertical axis which may be
operated at pressures in their gas or vapor spaces up to 15 psig. If a
tank were to be designed for such a pressure, it is most probably that the
tank would be designed with hemispherical or ellipsoidal or similar top
and bottom; a flat bottom would not be practical Because of anchoring
required to prevent uplift and damage to the wall/bottom connection. If
the operating gas space pressure were to be only, say, 3 psi, then in some
circumstances a flat bottom might be practical For the design of tanks
with non-flat bottoms, see API Standard 620, Section 3.9.
API 620 prescribes "least permissible thicknesses" for the tank
wall as the greatest of the following:
(1) 3/16 inch plus the corrosion allowance
(2) the calculated thickness per section 3.10.3 of API 620
plus the corrosion allowance
(3) the nominal thickness as per Table 3-4 of API 620:
Tank Radius (ft) Nominal Plate Tnickress (inch)
0-25 inclusive 3/16*
over 25-60 inclusive 1/4
over 60-100 inclusive 5/16
over 100 3/8
A tank to be designed according to API 620 and to be operated to, say, 15
psig in the gas/vapor space would have a bottom and a roof which are curved
figures of revolution about a vertical axis. The design calculations for
such a tank are complex and beyond the scope of this manual; the API Standard
620 should be consulted for a description of the design methods. It is
*The Seventh Edition of API 620 (Septembe~ 1982) shows the thickness
as 3/18 inch. It is believed that this is a Tiisorint. Clarification
has been requested from API in Washington, D.C.
-------
3-25
L'i'ed in what follows that a tank having a flat bottom has been designed
according to API 620 for operation at the lov, end of the range 2.5 to 15
psig. (Such a tank might be similar to one designed according to API 550
except that the upper limit of design pressure in API 650 is 2.5 psig.)
Some vertical cylindrical tanks have courses with different
thicknesses, the bottom course being thickest and the top course being
thinnest. Generally, the tensile circumferential stress at the bottom of
any course In a vertical cylindrical tank is given by
P x d
2 x ts
where P ~ total pressure at bottom edge of course
= liquid head + pressure in vapor space
HG + Pv
and
P = pressure in vapor space
H * maximum height of liquid above bottom edge of a given course
G * density of 1iquid
S = maximum allowable stress fo<* simple tension
d = diameter of tank
t 3 thickness of wall course required to carry the pressure *
total thickness - corrosion allowance
(Equation 1 will give accurate values of hoop stress at all levels except
in the bottom portion of the bottom course. In this region the hoop stress
will be less than the valu*» from Equation 1 due to the restraint given by
the bottom of the tank. However, this restraint also produces bending
stress ;.r, the wal 1.)
The design standard allows certain maximum stresses for specified
grades of steel. The maximum stresses must be calculated uy multiplying
the "maximum allowable tensile stress for simple tension" for the specified
grade of steel by the joint efficiency for the type of weld. The "maximum
allowable tensile stress for simple tension" is presented in Table 3-1 in
API Standard 620, in the right hand column. The joint efficiency varies by
the type of joint and the completeness of radiographic examination and is
-------
3-26
TABLE 3-4. MAXIMUM ALLOWABLE STRESS VALUES
FOR SIMPLE TENSION
Specification No.
(See Note 1)
ASTM A 36
ASTM A 131
ASTM A 131
ASTM A 131
ASTM A 283
ASTM A 283
ASTM A 285
ASTM A 442
ASTM A 442
ASTM A 516
ASTM A 516
ASTM A 516
ASTM A 516
ASTM A 537
ASTM A 537
ASTM A 573
ASTM A 573
ASTM A 573
ASTM A 633
ASTM A 66\2
ASTM A 662
ASTM A 678
AS 1 M A 678
ASTM A 737
CSA G 40 2 1
CSA G JO 21
ISO R630 Fe 42
ISO R630 Fe 44
ISO R 630 Fe 52
API Std 5L
ASTM A 53
ASTM A 106
ASTM A 106
ASTM A 333
ASTM A 333
ASTM A 524
ASTM A 324
Electric- Fuiion- Welded
ASTM A 134
ASTM A 134
ASTM A 139
ASTM A 671
ASTM A 671
ASTM A 071
ASTM A 67
ASTM A 67
ASTM A 67
ASTM A 6~
ASTM A 67
Grade
A
B
CS
C
D
C
55
60
5?
60
65
70
Qais 1
Claia 2
58
63
70
C and D
3
C
A
B
a
38W and 38T
4JW ind 44T
C and D
C and D
C and D
B
B
3
C
O
3
I
n
A 283 Grade C
A 2S3 Grade C
B
CA_<5
CC60
CC65
ccro
CTTO
CD80
CE55
CE60
Notes
5
4, 5, 6
5
5
4, 5
4. 5, 6
4
_
—
—
—
—
—
8
8
5
5
j
X 8
—
8
5 7
5. 8
8
5
5
5
5
5
—
—
—
—
—
—
•~
4. 5. 9
4. 9
9
9
9
9
9
1 9
S.9
9
?
Specified
Tenule
Strength (pound!
per square inch)
Plata
58.000
58.000
58.000
58.000
55.000
60.000
55.000
55.000
60.000
55.000
60.000
65.000
70.000
70.000
80000
d • *J
'J. _•-*!
70.000
70.000
65.000
70.000
70.000
30.000
"UOOO
60.000
65.000
60.000
62.500
71,000
?!pe
60.000
60.000
60000
••o.ooo
55.000
6i.OOO
60.000
55.000
55.000
55.000
60.000
55.000
60.000
65.000
*nooo
"O.UOO
30 000
55 000
60 000
"•linimum
Yield
Point (pound!
per squa'* inch)
36.000
34.000
34 000
.U.OOO
30.000
33 000
30.000
30.000
32.000
30.000
32.000
35.000
38,000
50.000
60 000
32.000
35.000
42.000
50.000
40.000
43.000
50.000
60.000
50.000
3?. 000
44.000
34.000
35.500
48.500
35.000
35.000
35.000
40.000
30.000
35.000
35.000
30.000
30.000
30.000
35.000
30.000
32.000
3 5. CO)
38.000
50 000
60.000
30 000
: :.ooo
vlujmum AJlCT»»ole tensile
Streis for Simple
Tension. 5. (pounds
per square inch)
(See Note 2. 3)
16.000
15.200
16.000
16.000
15.200
15.:.00
16.500
16.500
18.000
16.500
18.000
19.500
21.000
21.000
24.000
16.000
18.000
19.300
19.300
19.500
21.000
19 V>1
22.100
21.000
16.500
18.000
16.500
17. .TOO
19.600
18.000
18.000
IB.uCC
21.000
16.500
19.500
18.000
16.500
12.100
13.200
14.400
13 :oo
14 .100
15 -««J
16 >X>
16 *X'
1 9 200
!.; 2'X)
. i JJ»i
-------
3-27
TABLE 3-4. MAXIMUM ALLOWABLE STRESS VALUES
FOR SIMPLE TENSION (continued)
Speciliciiion No
iSc.- ^oie 1)
Grade
Specified
Tensile
Strength (pounds
Notes per square inch)
Minimum
Yield
Point (pounds
per square inch)
Maximum Allowable Tensile
Stress for Supple
Tension. $„ (pounds
per square mchi
(See Note .. 3 1
Forging*
>ST: , \ ,05
ASf .. A 181
AS "IX A !81
AST '. A 350
AS1V X 350
ASTV, A 350
I
11
LF!
LF:
LF 3
— 00.000
— 60.000
— 70.000
— 60.000
70.000
"0.000
30.000
30.000
36,000
30.000
3600C
40.000
18,'A'J
18.000
: i.ooo
18.000
:i.tro
21.000
Castings and Bolting
ASTM A 2"
ASTM A 193
ASTM A 307
ASTM A 307
ASTM A 320
SO-W
B7
B for (Unees and
pressure pans
B for structural pans
and anchor bolting
L:
10 60.000
— 1Z5.COO
11 55.000
— 55.000
— 1Z5.000
30.000
105.000
—
—
105.000
M 400
24.000
8. -MX)
15 00(5
24 000
Structural Shapes Resisting Internal Pressure
ASTM A 36
ASTM A 131
A
5. 6 58.000
5. 6 58.000
36.000
34.000
15 :oo
11 2V'
Non •.
V r<*nn:r>' mor'ilicition; jnd hnv'itions of ;pe-rJ5cation; n-
quired BV 2 2 tnrougji 2 6 ihall s« complied with
I Except for incse cases wnere additional faclon or tirruia'.ioni «re
applied as indicated bv references to Notes 5. 6. 10. or 11 the allow-
able tensile stresv vaiuex given in this lable lor maienah other than
boiling steel are the lesser of (ai 30 percent of the specified minimum
ultimate tensile strength for the material, or (b). 60 percent of the
specified minimum yield point
3 Eicept where a joint efficiency tactor u aJreadv refleaed in the
specified allowable stress yalue is indicated bv the references to Note
10. or *here the yalue of \ deiermmed in accordance with 3 5 2 2 is
less than the applicable joint efficiency jiven in Table 3—6 (and there-
fore effects a grener reduction in allowable stress :ha.n (he perunent
joint etfioencv lat:or would effect, if applied), (he specified stress
values for »eldj in tcrttion shall he multiplied bv the applicable joint
etficiencv factor. £, pven in Table 3—6
i Plu-i ind p.pj -inail noi bt t-»cd la
inch
5 i;.*M vaJ;n f
01 •; 92
o Stitsi v»juei are limned to tho^e lo
tensile strength of onlv 55.000 pounds fr: '^uare mtn
7 To 1": inch thirkness. inclusive
8 To 21/: inch thicknesi. inclusive
9 Stress values (o< fusion-welded pipe include j welded
cieno (acior of 0 30 .'See nose in 3 2J 2 , OnU sii^m-
shall be uicd. the ijse <.'i ipirai scam pipe is proh.DMed
10 Stress values for castings include a qualiiv tactor oi 0 <0
1 1 Allowable stress based on Seaion \ III o! ihc -980 ASME Boat
and Prfisurr Vfssfl Cotif. multiplied b\ the raiio r; :hr desien sires
iactors in API Standard 620 and ASME Section \Ii: njme
0 3Q'0 25
siru_i;4ial qunln\ sieels include a quaiit\ factor
an -jinmate
eifi-,
pipe
API Standard 620, Recommneded Rules for Design and Construction of
Large, Welded, Low-pressure Storage Tanks. Seventh Edition,
Reprinted by courtesy of the American Petroleum Institute.
1982.
-------
3-23
presented 1n API Standard 620 as Table 3 ;, "maximum allowable efficiencies
for arc-welded joints". For example, if a tank is built with ASTM A36
steel plate and the joints are double-welded butt joints spot radiographed,
then the maximum allowable tensile stress S
t3
Sta » 16000 psi x 0.35 - 13600 psi.
If the compressive (vertical) stresses are large (greater than 5 percent of
the tensile circumferential stress), then the maximum allowable stress must
be reduced further by a factor given in Figure 3-1 of API 620. However,
for cases where the compressive stress does not exceed 5 percent of the tensile
stress (likely for small hazardous liquid tanks), then the design may use the
values as calculated in the example above.
Equation 1 can be arranged to yield t directly:
s
where the allowable value of stress is obtained from the standard itself,
as explained above. In using Equation 2, consistent units must be used.
For example, to obtain ts in inches, express d and H in inches, P and S
in bls/in2 (psi), and G in Ibs/in^. Other units may be used if care is
taken to convert to compatible units. Thus, if G is used in Ibs/ft3 and
H and d in feet, the formula becomes:
ts(in) - H(ft) G(lb/ft3) •» Pv(psi) Id(ft) x 12 (3)
(2)
H(ft)
G(lb/ft3) * Pv(psi)
144
Id(ft) x 12
L J
2x5 (psi,
If the tank is open, i.e., is vented to the atmosphere, then Pv = 0 and
t n^ - ] H(ft) G(lb/ft3) d(ft)
tsim) - ^ $'(psi) (4)
If all courses of a tank are the same thickness, then the above
calculations (using Equation 3 cr a) must be made only once using H -
"o> T-.jm height of liquid above bottom of ''ower edge of first course.
-------
3-29
TABLE 3-5. MAXIMUM ALLOWABLE EFFICIENCIES
FOR ARC-WELDED JOINTS
Tvpe of Joint
ix luble -welded butt joint
Single-welded butt jomt with backing snip
or equivalent
Limitation
None
Longitudinal or mendionel joints gnd
enti£J or latitudinal joints between
over Hi inches thicK, and nozzle
welding without thickness limitation.
> Basic
Joint
Effjaency
(Note 1)
(percent)
85
arcumfer- 75
pUttes not
attachment
Radio-
graphed
. (Note 2)
Spot
Full (Note 4,
Spot
Full (Note 4)
Maximum
Joint
EiTicier.cv
(Note 3)
(percent ]
85
100
75
85
Single-welded butt joint without backing
stnp
Double full-fillet lap joint
Single full-fillet Up joint
Single I'.Ji nllet lap joints for head to noi-
zie toi'i.s
i.tschneni welding. 70
Longitudinal or meridional joints and equivalent 70
(Note 5) circumferential or latitudinal joints b«-
rween phies not over H inches thick, except thai
joints of this type shall not be used for longi-
tudinal or meriodmal joints which the provisions
of 3 12.1 require to be butt-welded.
Other circumferential or lanrudinal joints between 65
plates not over H inches thick.
Longitudinal or meridional joints ind circumfer- 35
enual or latitudinal joints between plates not
over H inches thick, except that joints of this type
shall not be used for longitudinal or meridional
joints which the provisions of 3. 12. 1 require to be
bin-welded. Multipass welding is required when
the thinner plate joined exceeds n inch.
For the attachment of he»ds copies 'o prwure not 35
over Vk inch required thjcknaai. only -*vh use of
fillet weld on made of nozzle.
TO
65
35
Nozzl: attachment fillet welds
Plug welds (see 3 24 5)
NOTTS
: Spot examination in all main seams as specified in 5.16 when not
completely radiographed.
: See 3 26 and 5 15
3 Regardless of any values given in this column, the efficiency for
lap-welded |0ints beiwren plates having surfaces of double curvature.
«.hich ha\e d cnmpressive stress across the joint from a negative value
of P^ or other external loading, may be liken M unity; bul such
compressi'.e stress shall not exceed 700 pounds per square inch. For
all other lap-welded jutnts. the joint efficiency factor must be applied
to the allowable compressive s'ress, 5^ The efficiency 'or full-pene-
tration t>utt-we:dea joints, which are in compression acroM the enure
inicknrss of the connected plain, may be taken a< unity.
•i All main butt welded seams completely radiognphed as specified
Attachment welding for nozzles and their reinforce-
ments.
(Included in strength factors in
3.16.7.2 Item I)
Attachment welding for nozzle reinforcements. 80
(Note 6)
35
80
in 5.15. and nozzle and reinforcement attachment welding examined
by mzgnenc-pirnde method as specified m 5.20.
5. For the purposes of tfcs table, a circumferential or latitudinal joint
shall be considered to be subject to the same requirements and limita-
tions as longitudinal or meridional joints when juch arcumterential or
latitudinal joint is located: (a) '.n a spherical, tcnsphencal. or ellip-
soidal shape or in any other surface of double curvature, ibi. at the
junction between a conical or dished roof (or bottom I and cylindrical
sidewalls. such as considered in 3.12.2; or (c). at a similar juncture si
either end of a transition section or reducer such as shown in Figure
3-7.
6. The efficiency factors shown for fillet welds and plug welds are not
to be applied to the allowable shearing stress values shown in Table
3-2 for structural welds.
API Standard 620. Recotruiended Rules for Design and Construction of Large,
'.•.'e1 ded, Low-Pressure Storage Tanks ,
courtesv of
a /Seventh Edition,T9S2. Reprinted by
the American Petroleum Institute.
-------
3-30
COf JUSTEN1 COMPRESSJVE STRESS. Sc. FOR BlAKIAL T£NSWN -COMPRESSION. PS*
M*-»,»0*J*0
§ § § § § § 1 §
1 AT NO TIME CAN A COMPRFSSIVE STRESS FOR A PARTICULAR ' : ' j ' ' i ' ! !
' VALUE OF y EXCEED So REPRESENTED »T CURVE OAK. ! ; ' | ' [^COMPHESSIVE STRESS IS
MQ V*IM%$ o» COMPRfSSrvf *TiHf4 OR >• *R» PMnrnro TO ; ! ^ .TminiuAi M«T o n
1 FAU. TO THE LIFT OR AtOVE TM» CUKVE. | | : I ! i iF COMPRESSJVE STRESS IS
! (SEE FIGURE ^-3 TOR RELATIONSHIP tCTWEEN FACTORS M ANO N> ! ,
1 ! ! , • ! ill ^M» i i s«- is.ooo P»I , c
1 ' \^^^.^ — r — ~\ iQ.ifl
^— .$e«-MSc»-':,000 M
—
^—~~*m
1 /„ : Q nn
—
i
U '
1 -y !'•'!_ i ' 2
/ • i ' ! !
/ ! , ; ' s-i°
/ II,
/ , i ! i 'I ! ! ' I'll .
s
;
0 0.003 0.004 0.00* 0.001 0.010 0.01] 0.01* O.OIt 0.011 0.03S 0013
(l-el/R RATW IUINOTI)
FIGURE 3-2. BIAXIAL STRESS CHART FOR COMBINED TENSION ANO
COMPRESSION, 30,OGO TO 38,000 PSI YIELD
STRENGTH STEELS
API Standard 620, Recommended Rules for Design and Construction of Large,
Welded, Low-Pressure Storage Tanks, Seventh Edition, 1982. Reprinted by
courtesy of the American Petroleum Institute,
-------
3-31
If the calculated (required) total thickness of any course
(t = tc + ts) is greater than the actual thickness of that course, then
a possible mode of operation would be to reduct the allowable maximum
height of liquid to a value where the calculated thickness is less than
the actual thickness. In this case. Equation 3 can be rearranged to
yield H directly:
H (ft)
144
G(lb/ft3)
S(psi) ts(in)
6 d(ft)
If this equation is applied to each of several courses of a tank, then
the allowable H would be the smallest value found among the results.
3.2.5.1.1 Sample Calculation. Assume a tank is to be do:
to API 620 for a liquid with the following properties:
• Vapor pressure at 100 F = 10 psig
0 Density = 80 Ib/ft3
Tank to be built of A36 steel, single-welded butt joints with spot radio-
graphs, 30 feet high and 20 feet diameter; maximum liquid height = 23
feet; maximum steel temperature, 100 F.
These design values give:
Pv = 10 psig
S = 16000 x 0.75 = 12000 (tensile strength [from Table 3-4] x
weld efficiency factor [from Table 3-5])
d = 20 feet
H * 28 feet
G = 80 bl/ft3.
Assuming that the compressive stress in the bottom course is less than 5
percent of 12000 psi, Equation 3 then will give ts for the bottom course as
follows:
loo « on 1
20 x 12 inch
2 x 12000
24COO
= 0.26 inch.
-------
3-32
3.2.5.2 API 650 Tanks. Shell design in the 650 Standard can be
considered to begin with a choice of plate material from a list of permissible
materials in Table 3-2 of the Standard (see Table 3-6). This table presents
a number of ASTM, CSA, National Standard, and ISO-R630 Standards specifi-
cations and grades of steel plate which are permissible. Also shown are
minimum yield and tensile strengths, product design stress' Sj, and hydro-
static test stress St. It is noted that for some steel specifications/
grades, Table 3-2 (of the Standard) shows lower values of Sd or St for the
first (bottom) course than for upper courses.
Since the applicant is required to report the design standard
used and 'do the deisgn calculations, the permit writer must merely review
the submitted information. A brief discussion of methods which may be
refer-.nced by the applicant is given below.
Section 3.6 of the 650 Standard cites two methods of calculating
shell thickness:
• One-Foot Method
• Variable Design Point Method.
The Variable Design Point Method normally provides a reduction
in shell course thicknesses and total material weight than will be obtained
by the One-Foot Method. As cited in Section 3.6 of API 650, a more impor-
tant aspect of this procedure is its potential to permit construction of
larger diameter tanks within the maximum plate thickness limitation (i.e.,
without impact testing). The method is illustrated by an example in
Appendix K of Standard 650. Since tanks for storage of hazardous fluids are
expected to be relatively very small (in the range of tens of thousands of
gallons), the major advantage of the Variable Design Point Method will not
be realized for them.
The One-Foot Method may be used, and most likely in the simplified
form of Appendix A of Standard 650, which provides an optional design basis
for relatively small tanks. These tanks would be field-erected tanks in
which the stressed components are limited to a maximum of 1/2 inch nominal
thickness, including any corrosion allowance; the maximum design tensile
stress is 21,000 psi. Such tanks also are limited to design metal
-------
3-33
TABLE 3-6. PERMISSIBLE PLATE MATERIALS AND
ALLOWABLE STRESSES (in pounds
per square inch)
Plate
Spea-
Gcanon
ASTM
A2S3
A2S5
A131
A131
A36
A442
A442
A573
A573
A573
A516
A516
A516
A316
A662
A662
A537
A537
A633
A678
A678
A 737
Grade
C
C
A.B.CS
EH 36
55
60
58
65
70
55
60
63
70
B
C
1
2
CD
A
B
B
Minimum
Yield
Strength
30,000
30.000
34,000
51,000
36,000
30,000
32.000
32,000
35.000
42,000
30,000
32,000
35,000
38.000
40.000
43,000
50,000
60,000
50,000
50,000
60.000
50,000
Minimum
Tensile
Strength
55,000
55.000
58,000
71.000'
58.000
55.000
60.000
58.000
65.000
70,000'
55,000
60.000
65.000
70,000
65,000
70,000'
70,000'
30.000'
70,000'
70,000'
80,000'
70,000'
Product Design
Stress 5j
1st Course
20.000
20.000
21.800
26.600
21.800
20,000
21JOO
21JOO
23.300
26.300
20,000
21JOO
23,300
2SJOO
24,403
26.300
26,300
30.000
26JOQ
26JOO
30,000
26.300
Upper Coune
20,000
20,000
22.700
28.400
2X200
20,000
21JOO
21JOO
23JOO
28.000
20.000
21JOO
23.300
23JOO
26.000
28.000
28,000
32,000
28.000
28.000
32.000
28.000
Hydrostatic Test
Stress S,
1st Course
22.000
22,000
23,200
28,400
23.200
22.000
24.000
23.200
26,000
28.000
22.000
24,000
26,000
28.000
26.000
28.000
2S.ono
32.000
28,000
mono.
32,000
28.000
Upper Coune
22,500
22.500
24,900
30,400
24.900
22.500
24,000
24,000
26JOO
30.000
22.500
24.000
26JOO
28.500
27.900
30.000
30.000
34,300
30.000
30.000
34.300
30,000
CSA Standards
G40.21
G40.21
G40.21
National
38
44
50
Standards
37
41
44
38.000
44.000
50,000
30.000
34,000
36,000
60,000
65.000
70,000'
52.600
58.300
62.600
22.500
24.400
26JOO
19.700
21,900
23.500
24,000
26.000
28.000
20,000
22.700
24.000
24,000
26.000
28.000
21.000
23,300
25,000
25,700
27.900
30.000
22 ..500
25.000
26.800
ISO-R630 Standards
Fe42
Fe*4
Fe52
B,C
3,C
CD
34,000
35 JO)
48.500
60.000
62.500
71.000'
22.500
23,400
26.600
22.700
23.700
28.400
24.000
25,000
28.400
7-5.500
^6.600
30.400
Note:
1. By agreement between purchaser and manufacturer, the tensile strength of these materials may be increased up to 75,000 psi minimum
and W.OOO pn maximum (and to 85.000 psi minimum and 100.000 pii maximum (or ASTM A 537, Claw 2 and A678. grade 65. *hen ihu
11 done the allowable stresses shall be determined u stated in Par. 3.6.2.1 ~.nd 3.6.2.2.
API Standard 650, Welded Steel Tanks for Oil Storage. Seventh Edition,
Reprinted by courtesy of the AmericaV'Pe'troleW Institute.
-------
3-34
tures above minus 20 F (above minus 40 F when killed and fine grain
material is used). For a more complete description of the design methods,
materials, and limitations, see Appendix A of API Ttandard 650.
In the One-Foot Method of calculating shell plate thicknesses,
the required minimum thickness shall be the greater of the values computed
from the following formulae:
Design shell thickness t,(in) = 2'V(H'1?2 + C.A.
d bd
Hydrostatic test shell thickness tt(ln) = 2-6 d(H-1)
i it
where
d = nominal diameter of tank, feet
H * height from bottom of course to maximum height
of liquid, feet
g * specific gravity of liquid
C.A. a corrosion allowance, inch
Sd = allowable design stress, psi
St * allowable stress for hydrostatic test condition
The Standard also specifies that the total shell thickness for
each course shall not be less than required by Sections 3.6.1.1, 3.6.1.6,
and 3.6.1.7 of Standard 650. These requirements are:
API 650. Section 3.6.1.1
(1) Design shell thicknesses, including corrosion
allowance, or
(2) Hydrostatic test shell thicknesses (excluding
corrosion allowance)
(3) But in no case shall the shell thickness be less
than the following:
Nominal Tank Nominal Plate
Diameterl Thickness2
(feet) jinches) r
Smaller than 50 3/16
50 to 120, exclusive 1/4
120 to 200, inclusive 5/16
Over 200 3/8
-------
3-35
Notes: 1. Nominal tank diameter shall be center-line diameter of the
bottom shell course plates, unless otherwise specified by
the purchaser.
2. Nominal plate thickness refers to the tank shell as constructed.
The thicknesses specified are based^on erection requirements.
~^e minimum thicknesses specified by (3) apply to all tanks.
API tlO. Section 3.6.1.6
The calculated stress for each course shall not be greater than
permitted for the particular material for that course. No
shell course shall be thinner than the course above it. The
design stress for an upper shell course shall not be greater
than the design stress for a lower shell course.
API 650, Section 3.6.1.7
The tank shell shall be checked for stability against buckling
from the design wind velocity by the rules of Section 3.9.7 of
API 650. If required, additional structural members or increased
plate tnicknesses, or both, shall be utilized.
Minimum thicknesses are also specified for bottom plates. All
bottom plates shall have a minimum (nominal) thickness of 1/4
inch (6.0 mm) when specified by the purchaser. Annular bottom
plates shall have (nominal) thicknesses not less than those
listed in Table 3-1 of the Standard. No further calculations
are required. (All thicknesses specified in design standards
are nominal, and material is purchased by the manufacturer by
nominal thickness. Dimensional tolerances on the plate thicknesses
are given in the material specification, e.g., ASfM.)
3.2.5.3 UL 58 and 142 Tanks. UL 142 steel above-ground tanks
are explicitly stated as being intended only for use wit'i non-corrosive,
stable liquids. Based on an analysis of the testing procedure used for Ul
58 steel underground tanks, it is clear that such tanks are also intended
only for USe v/ith non-corrosive liquids. Thus, it is concluded that the
entire original shell thickness is required for the anticipated tank wall
-------
3-36
stresses likely to be imposed and there is n£ inherent corrosion allowance
in these standards. However, corrosion allowance may be added to the
thicknesses.
3.2.5.4 ASME Section VIII Pressure Vessels. In uncommon situ-
ations where tanks for pressures greater than 15 psig are 'required in
hazardous waste facilities, then the ASME rules for Section VII pressure
vessels will be required as guidance. Corrosion allowances are used in
such vessels. (See Section 3.2.1.11 of this manual for more information.)
If used pressure vessels are to be derated for use in atmospheric or low
pressure hazardous waste storage, then API 650 or API 620 can be used for
guidance in setting the minimum shell thickness. The minimum thickness
for the tops and bottoms are more cif'Mcult to specify because the "special
heads" typically used for pressure vessels are capable of withstanding
greater pressure at equal thickness than the flat bottoms and tops used
in API 620 and 650 tanks. The applicant should provide the engineering
information to support a suggested minimum top and bottom thickness in
the permit application for each such tank. In some cases, API Standard
620 may provide adequate guidance for tops and bottoms.
3.2.6 Minimum Thickness, Corrosion Allowance,
and Service Life" ~
The following section considers wall thickness and corrosion
allowance as they interact with the expected service life of a tank.
3.2.6.1 Minimum Shell Thickness. Title 40 CFR 264.191(a) states
that "Tanks must have sufficient shell strength . . to assure that they
do not collapse or rupture . . . The Regional Administrator shall require
that a minimum shell thickness be maintained at all times to ensure sufficient
shell strength." The design standards presented in sections 3.2.1 and the
tank wall stress considerations discussed in section 3.2.5 of this manual
either provide the procedure to compute the minimum shell thickness required
by 40 CFR 264.191(a) or specify such a wall thickness. Such a computed or
specified minimum thickness includes a negligible allowance for minor surface
-------
3-37
corrosion and some allowance for unexpected stresses owing to pressure
changes. On the basis of applicable design standards or other engineering
information, the permit writer will specify a minimum thickness for the
tank in the facility's permit. The owner or operator is expected to
maintain this minimum thickness throughout the service life of the tank.
The consideration of non-uniform thickness in a corroded tank
is illustrated in a following section (see Example 3 in section 3.2.5.4
of this report.)
_3_._2_L6.j__CgrrQSion Allowance. Corrosion allowance is defined as
the difference between the actual thickness of a tank's walls at a given
time and the required minimum thickness of the tank wall. (Measures of
wall thickness should be exclusive of the thickness of any linings or
coatings applied to the tank walls. However, use of coatings or lining
to protect and maintain wall thickness is encouraged in many cases.)
Because corrosion is a continuous process, the corrosion allowance
diminishes over time.
3.2.6.3 Expected Service Life. Expected service life is defined
as the corrosion allowance divided by. the corrosion rate of the waste upon
the construction materials of the tank. The expected life is the amount
of time that a hazardous waste can be stored in a tank before the corrosive
action of the waste causes the thickness of the tank walls to equal the
minimum required thickness. Information on the expected service life is
valuable in determining frequency of inspection and renewal dates for permits
The National Association of Corrosion Engineers (NACE) &rd others have
published data en corrosion rates for different relatively pure chemicals.
Representative tables and a discussion of their use are contained in the
permit writers' guide on hazardous waste compatibility. These tables can
be used to estimate the corrosion rates of such chemicals if the chemicals
stored have similar properties. Further information about corrosion raxes
is presented in Appendix B of this manual.
Caution should be exercised in relying upon published corrosion
rates since such factors as the oxygen and water content and the chloride
content of the waste can significantly affect the corrosion r.ite, causing
substantial variation from the published value.
-------
3-38
Unfortunately, hazardous wastes are usually mixtures of chemicals;
the corrosion rates of materials exposed to them are likely not to be
known. In such circumstances where the corrosion rate of the mixture
is not known, a conservative approach is recomrended. In general, the
corrosion rate is not profoundly affected by the concentration of salts
in aqueous solutions; that is, if the concentration is reduced by 50
percent, the corrosion rate may not be reduced at all or far less than
50 percent.
A procedure for estimating the corrosion rate of mixtures would
be first to determine the chemicals and the range of their concentrations
in the mixture. Then, through the NACE (or other) data, determine the
corrosion rate (at the indicated concentration range if possible) for
each of the chemicals present with the material of construction of the
tank interior. After this data has been tabulated, the highest corrosion
rate indicated should be selected as the anticipated corrosion rate of
the tank with the mixture. Based on this value, the anticipated service
life for the tank may be calculated, from which the required inspection
frequency can be specified by the permit writer partially contingent on
results of future periodic inspections. The desirability of acquiring
corrosion test data before the first tank inspection by exposing (within
the tank) test specimens of the specific material of construction used
for the tank to the hazardous waste mixuture may become obvious. (See
Section 8.6.2.2 of this manual for further information.)
In order to estimate the expected service life of a tank,
the permit writer should determine:
• The standard code used for building the tank and its
• date or edition
• The specific materials of construction and their
properties
• The required minimum thickness of the shell plates of
a tank (a function of fie containea liquid's specific
gravity, height of liquid level, and diameter of the
tank)
• The corrosion a'llowance
• The presumed initial corrosion rate or the actual
corrosion rate based on periodic measurements.
-------
3-39
3.2.6.4 Examples. Three examples have been developed to illustrate
the interdependency of the factors involved in determining the expected service
life of a tank. These examples illustrate how the minimum required tank wall
thickness, the corrosion allowance, and the expected service life are determined
Various interactions (trade-offs) among minimum required thickness, corrosion
allowance, and expected life are also presented.
Example 1. A vertical, cylindrical, welded carbon steel tank built
in 1974 and u^cu for the storage of oil is to be converted to store hazardous
waste at a maximum design pressure equal to 0 psig (atmospheric pressure) and
at ambient temperature. The tank, which has 72-inch butt-welded courses, was
fabricated in accordance with the second edition of API Standard 650. The tank
is 60 feet in diameter and 30 feet high. The oil-specific gravity is less
than 1.0, and the shell plate thickness was measured to be 0.76 inch uniformly
prior to the tank's being converted to store the waste. API Standard 650
specifies the following formula in calculating the minim-jm thickness of the
tank's walls to preclude excessive stresses:
t . . U.6)(d)(
0 (0.85H2
(0.85)(21000)
td = minimum shell thickness, in inch;--
d - nominal diameter of tank, in feet
H = height, in feet, from bottom of course under consideration
to overflow that limits tank filling or to overfilling
alarm or feed cutoff trigger
g = specific gravity of liquid to be stored, but in no case
less than 1.0
-------
3-40
0.85 = joint efficiency factor for butt-welded joints (see Table 3-5)
21000 = maximum allowable tensile strength for applying the
factor for efficiency of joint
2.6)(60)(30-1)(1.Q)
!.6)(60)(30-1)
(0.85)(21000
= 0.25 inch (approx.)
As calculated above, this tank requires a minimum wall thickness of 0.25 inches
to accommodate the stresses presented by oil stored in this tank to a height
of 30 feet. If the tank were to be used to store hazardous waste with a specific
gravity less than or equal to 1.0 and a height of 30 feet, the initial corrosion
allowance would be 1/2 inch (0.76 inches - 0.25 inches - 0.51 inches).
The hazardous waste to be introduced into this tank, however, was
measured to have a specific gravity of 1.2, and the owner or operator has
decided to keep the minimum wall thickness of 0.25 inch in order to have the
maximum 0.51 inches of corrosion allowance to prolong the service life of the
tank. Because the specific gravity of the waste will place greater stress
on the tank's walls, the maximum height allowed for storing the waste is
calculated to be:
n ?q - (2.6)(6g)(H-l)n.2)
u'" " (0.85)(2100oJ
»
H = 24 feet (approx.)
The tank in this case can only have a maximum waste liquid level of
24 feet if the maximum allowable stress is not to be exceeded. Overfilling
controls should be established at this level.
The assumed hazardous waste is a salt solution contaminated by
heavy metals with the most corrosive component at concentration being ferrous
sulfate. Utilizing the National Association of Corrosion Engineers (NACE)
table, we find that ferrous sulfate has a corrosion rate of greater than
-------
3-41
0.05 inch per year on carbon steel. Assuming conservatively that the waste
has a corrosion rate of 0.1 inches per year, we determine that the expected
service life of this tank for storing this waste is calculated to be 5.1 years
(0.51 inch divided 0.1 inch per year = 5.1 years). Therefore, theoretically
this tank should be used to store this particular waste for no more than 5.1
years at a height not to exceed 24 feet. It should be noted, however, that
a corrosion rate of greater than 0.05 inches per year is extremely high. (In
most cases, a liner would be used if ferrous sulfate were to be stored in a
carbon steel tank.) After an initial storage oeriod, the actual corrosion
rate should be physically measured, and by knowing the corrosion allowance
and this actual corrosion rate, we can determine the expected life of a tank.
The owner-operator should be required to measure the actual corrosion rate
as part of the periodic assessment of the tank's condition within a given period
and report it to "he permit writer when renewing the permit.
As the tank approaches the end of its expected life, the owner-
operator should increase the frequency of comprehensive inspections of the
tank and be prepared to recoat or reline the tank; derate the tank (which means
that the liquid level can be lowered to reduce the stress and, therefore,
reduce the required minimum wall thickness, and increase the corrosion allowance)
or introduce a new waste with lower specific gravity to reduc5 the stress; or
prepare the tank for closure.
Example 2. An above-ground, horizontal, cylindrical welded steel
tank, built in 1973 and used for the storage of gasoline, is to be converted
for the temporary storage of slightly corrosive waste at ambient temperature
and at a maximum internal pressure of 0.5 psig. The tank was fabricated
according to the fourth edition of Underwriters' Laboratory (UL) Standard 142
with an extra corrosion allowance and installed in accordance with Flammable
and Comoustible Liquids Code of the National Fire Protection Association (NFPA
No. 30). The tank is 144 inches in diameter and has a uniform measured shell
thickness of 3/8 inch aid a maximum capacity of 35,000 U.S. gallons. The
hazardous waste to be stored has a specific gravity of less than 1.0 and a
theoretical corrosion rate of 0.05 inch per year on the construction mater'a 1
of L'-'e tank.
-------
The owner would like to store from 1,CCO to 30,000 gallons of waste
in the tank at a given tine. The following tabulation from UL 142 indicates
that a minimum thickness of 0.25 inch must he maintained to prO"ide for strurtuial
stability to accor^iodate the upper vo^me liiiit of 30,LOO gallons.
METAL THICKNESS - WQRIZCN^L TANKS
Capacity,
U.S. Gallons
S50 or less
551 - 1,100
1 ,101 - 9,000
1 ,101 - 35,000
35,001 • 50,000
Maximum
Diameter,
inches
48
64
76
144
144
Mi n i muni
Thickness of
Steel , inches
0.105
0.135
0.179
0.250
0.375
The tank, therefore, has a maximum corrosion allowance of 0.125 inch,
wnich is 3/3 inch (current actual thickness) minus 1/4 inch (illowable minimum
thickness). If the ^aste to Le stored has a corrosion rate of 0.05 inch per
year, the expected life of the tank storing 30,000 gallons of waste is "-1/2
year (0.125 inch divided by 0.05 inch per year) prior to coating, lining, or
closing the cank. Even if the tank were to be utilized to store a maximum of
1,300 gallons, however, trs tank co'jld still only be used for a period of
2-1/2 years (0.375 minus 0.250 inch divided 0.05 inch per year) because a tank
that is 144 inches in diameter must have 0.25-inch-minimum wall thickness,
according to this standard.
Example 3. A vertical, cylindrical welded carbon steel tank is to
Le converted to storage of hazardous waste av. a maximum design oressure equ^l
to 0 osig (atirospheric pressure) and at ambient temoerature. The tank was
fabricated in accordance with the second edition of API Standard 650. The
tank - 55 feet in diameter and 25 feet hiah. The specific gravity of the
waste to be stored in the tank ,vas measured to be 1.2. Therefore, the min--ur
•vall thickness in inches is:
-------
3-43
t L2.6)(55)(24)(1.2) *
1 (0.85}[7TOM1
t 0.23 inches
The wall thickness of the tar.k is nonuniformly corroded. The thickness
was measured in 20 locations, and the results are given below:
1) 0.20
2) 0.19
3) 0.22
4) 0.24
6) 0.20
7) 0.13
8) 0.23
9) 0.16
11) 0.21
12) 0.19
13) 0.17
14) 0.17
16) 0.23
17) 0.20
18) 0.22
19) 0.14
5) 0.22 10) 0.20 15) 0.18 20) 0.23
At points 9, 13, 14, and 19, five additional measures were made along
a longitudinal strip 4 inches long. The average measured thicknesses at these
points were as follows:
9) 0.16 14) 0.19
13) 0.18 19) 0.16
The minimum of these local averages (0.16 inches) is used for comparison with
the required minimum thickness.
Because the measured thickness is less than the required minimum
thickness, the tank must be derated or removed from service. If it is assumed
that the owner-operator decided to derate the tank, the new high level would
be calculated as follows if the hazardous waste is not corrosive:
.
(0.85H21000)
H = 17.6
rounding down
H * 17
* rorruia from Example
-------
3-44
In this case, the owner-operator would install overfilling controls (e.g.,
high-level alarms or automatic feed cutoff) at 17 feet. However, if the tank
were to store a corrosive liquid, the tank should be lined or coated to prevent
further corrosion because there is no corrosion allowance for the tank.
3.2.7 Tank Openings
Tanks generally will have a number of openings for such purposes
as inspection (manholes), liquid inlets and outlets, liquid overflow,
attachment of pressure/vacuum control devices, gas/vapor venting, etc.
The various design standards have specific requirements regarding the sizes
and shapes,-locations, reinforcements, welding details, etc. Some of the
most important features are indicated below.
3.2.7.1 Tank Openings in API 620 Tanks. In API 620 tanks, all
openings in sidewalls, roofs, or bottoms shall be circular, elliptical, or
obround (an obround figure is one which is formed by two parallel sides and
semicircular ends). For elliptical or obround openings, the long dimensions
shall not exceed twice the short dimension; the long dimension shall pre-
ferably coincide with the direction of greater strsss.
Section 3.14 of the Standard prescribes how far an opening must
be from other openings, from changes in geometry such 'as junctures between
wall and bottom, from attachments such as supports, etc. Also, each opening
shall be located so that any attachment or reinforcement attached to it can
be made fully accessible for inspection and repair on both the inside and
the outside of the tank, except in the case of connections which, for
compelling reasons, must be located on the underside of a tank bottom resting
directly on the tank foundation.
There are no limits of the sizes of openings, provided they
satisfy the requirements outlined above and are properly reinforced, except
that the largest inside dimension of an opening shall not exceed 1.5 times
the smallest radius of 'curvature in that portion of the tank. The latter
limitation does not apply to large openings centrally located or the '•oo*'
or bottom of a tank with the axis of the opening coincident with the
•verf.cal) axis of the tan*.
-------
3-45
There are special requirements for amounts of reinforcement, and
their v.eldments, for the dimensions of nozzles and their reinforcements,
for bolted flange connections, and for cover plates. See Sections 3..16
and 3.17 of API 620.
3.2.7.2 Tank Openings i > API 650 Tanks. Section .3.7 of Standard
650 describes the requirements fa- shell openings. Generally, the intent
is to restrict the use of appurte • :• :'es to those providing for attachment
to the shell by welding. The use y designs provided in 3.7 are required,
except that connections and appurtenances complying with API 620 are
satisfactory alternative designs.
Section 3.7 describes in detail the requirements for reinforcement
and welding, spacing of welds, thermal stress relief, shell manholes, shell
nozzles and flanges, flush-type cleanout fittings and shell connections,
and inspection of welds.
3.2.8 Tank Diagrams and Data Sheets
To describe the tank, nozzles, and selected process data, the
permit apolicant may submit a completed form such as is presented a*
Figure 3-3. Alternatively, copies of the original tank specification
sheet used for purchase of the tank might be provided along with a defini-
tion of the use of each nozzle; a sample of such a tank specification
sheet is presented in Appendix L of API 650. Similarly, a simple tank
diagram illustrating the location of nozzles and instrumentation may be
prepared by the applicant, or the diagram or sketch of the tank submitted
with the original tank specification sheet may be modified and used for
the permit application.
An example of a tank diagram is given in Figure 3-4.
-------
c
o
£ >J
o o
14 _
i/1 » J
i/l nC
Qj t__
O Q*
O •"*
*- O
O.
C
QJ
m L_
nj d*
-t: QC
o> c:
ac en
at
i "^
UL . or
No/ / .
\
2
3
Fluid
LiqSVap
Vapor
Liquid
Muw,
Lb/llr
4539
3499
1040
Dens i ty
Lb/ft3
0.754 (Max.)
0.584
40.3 (Min.
1 euiiiet ature, F,
Honn Max/Min
95
95
95
Press . , ps ia
Norm Max. Tiii^e LL Data for
16.2 Level Control High (LCII)
-------
Source: Fred C. Hart Associates, Inc.
FIGURE 3-4. A SIMPLE TANK DIAGRAM
Note: Circled numbers refer to nozzle numbers.
HIT - high liquid level; LAH = level alarm high; ILL = low liquid level
LAL s Level alarm low.
-------
3-48
3.2.9 Inspection and Evaluation of Welds (Seams)
Title 40 CFR 264.19(a) requires the Regional EPA Administrator
to review design of the tanks including seams. The following discusses
the issues involved for tanks built to standards, those not built to
standards, and both new and used tanks.
3.2.9.1 Tanks Built to Standards. Tanks which have been built to
recognized standards such as ASME Section VIII, API 620, API 650, UL 58 or
UL 142 will have been inspected and tested according to the requirements
of the particular standard. The ASME and the API standards are very specific
in their requirements regarding qualification of welders and of welding
procedures, and also regarding inspection and testing of welds and of the
vessels. The UL standards specify types of acceptable welded joints,
including geometric details and dimensions, but are not specific about
qualification of walders or of welding procedures. The final test specified
by UL 142 and UL 58 is a leak test: either air pressure between 5 and 7
psig together with a leak-finding fluid, or filling the tank with water
plus an additional 5 psig overpressure.
It is reasonable to as sums that i new tank built to a recognized
standard does not require additional inspection or tests of the welds beyond
those required to meet the standard.
3.2.9.1.1 Used Tanks. For used tanks which were built to standards
such as those mentioned above, evaluation of the welds in the used condition
involves problems similar to those discussed elsewhere regarding the walls
and the floor. See Sections 4.1.1 and 4.1.2 for guidance on methods of
inspection ar,.1 particular features to be measured or observed. Of course,
in the present context, the application should include specifically a
description of the conditions of the welds, and should indicate the methods
of inspection used to determine the conditions.
3.2.9.2 Tanks Not Bui.U ..to Standards.. Evaluation of welds in tanks
not built to a recognized standard involves similar problems to that dM'js
-------
3-49
Regional EPA Administrator will rely on appropriate standards and other
available information in the reviewing and permitting process. Since we
are concerned here with evaluation of tanks and welds which were assembled
without reference to a standard, the burden will be on the applicant to
provide sufficient data on the materials, design, welding procedures,
welder qualification, weld inspection methods and results, such that the
tank may be reviewed in detail by a qualified engineer. The permit
writer should anticipate that review will require an engineering analysis
at the completeness-check phase and at the technical evaluation phase.
-------
4-1
CHAPTER CONTENTS
4.0 USED, NON-METAL, AND OTHER TANKS
4.1 Used Steel Tanks
4.1.1 Inspection Procedures
4.1.2 Description of Condition
4.1.3 Estimation of Adequacy of Wall Thickness
4.1.4 Use of Tank History
4.1.5 Estimation of Service Life of Used Tanks
4.2 Fiberglass-Reinforced Plastic Tanks
4.2.1 Standards and Codes
4.4.1 .1 AS7M D4021-81
4.2.1.2 UL 1316 (Tentative)
4,2.2 Evaluation of Fiberglass-Reinforced Plastic
Tank Applicability
4.2.3 Minimum Shell Thickness Equivalent
4.2.4 Frequency of Inspections
4.2.4.1 Immersed Test Specimens
4.2.4.2 External Inspections
4.3 Rectangular (Polygonal) an
-------
4-2
4.0 USED, NON-METAL, AND OTHER TINKS
Chapter 3.0 dealt with the permitting of new metal tanks with emphasis
on the types most likely to be used in hazardous waste storage facilities. If
the permit application is for a new facility that will use only new standard
metal tanks, then the permit writer would not need to refer to this Chapter 4.0
which deals with used tanks, non-standard metal tanks, and tanks constructed of
non-metallic materials of construction. The standards and codes are well developed
for new metal tanks and the approach in permitting such tanks can be "by the book".
Conversely, less guidance is available for the material presented in Chapter 4.0
because codes and standards have not been as well developed.
More specifically, the subjects addressed in this Chapter include:
4.1 Used Steel Tanks
4.2 Fiberglass-Reinforced Plastic Tanks
4.3 Rectangular (Polygonal) and Other Non-Standard Metal Tanks
4.4 Concrete Tanks
Other types of tanks could have been addressed in this chapter such
as wood and solid plastic tanks, but these have been omitted because they are
not likely to be encountered in sufficient frequency to justify preparation of
guidance. If a oennit application with such a tank is encountered, the permit
writer should anticipate^ that some special study will likely be required in the
permitting process, and the applicant should provide adequate enoineerina detail
to support their permitting.
4.1 Used Steel Tanks
When permitting an existing hazardous waste storage facility, the
tanks ^re obviously in used condition at the time the permit is sought by the
applicant. Furthermore, used tanks may be acquired for use in a new hazardous
waste facility.
When permittinn used tanks, ask two types of questions as follows:
1. If the tank were new, would the tank be suitable for the
proposed us;e in terms of pressure, materials of construction,
and other design aspects? What would be specified by the
-------
4-3
permit writer for the minimum shell thickness and the
inspection frequency? (See Chapters 3.0 and 8.0).
2. Based on recent tank inspection information, does the
tank need to be repaired, derated, or removed from service?
The remainder of this section discusses used steel tanks, although
the approach is generally applicable to other types of tanks. For a used
steel tank, applicant should provide the following data:
1. Design standard used and its date or edition number
2. Dimensions of tank
3. Shell thickness
4. Steel specification and grade
5. Description of condition of tank, especially degree and
type of corrosion from past service
6. Type and quality of foundation and tank supports
7. Proposed operating conditions, i.e.,
Identity of liquid to be stored
Density of liquid
Corrosivity of liquid and compatibility with tank materials
Maximum height of liquid
Temperature of liquid
Vapor pressure of liquid at storage temperature
Pressure in gas/vapor space.
8. Complete documentation of any sampling and testing pro-
cedures used to establish characteristics of tank materials
such as sampling procedures and analytical and testing
laboratory reports.
9. Description of inspection procedures including extent
of coverage of internal and external surfaces, degree of
inspection of welds, valves, vents, gaskets or seals
whether paint coatings, linings, or insulation was
partially or totally removed and results of inspection.
10. Description of any remedial measures planned or performed
to offset defects from past service or those involved in
inspection.
-------
4-4
(
4. T.I Inspection Procedures
Inspection of used tanks intended for storage of hazardous wastes
will be required in order to determine the conditions of the tank, its foundations.
and appurtenances, as these may have deteriorated due to service. Reasons for
inspection, particular features to be observed and measured, tools required, etc.
are discussed fully in the API Guide for Inspection of Refinery Equipment,
especially Chapter XIII, Atmospheric and Low-Pressure Storage Tanks. Chapter XIII
covers these major topics:
• Descriptions of Types of Tanks
• Reasons for Inspection and Causes of Deterioration
« Frequency and Time of Inspection
• Methods of Inspection and Limits and Tools
• Methods of Repair
Other pertinent chapters include:
• Chapter II - Conditions Causing Deterioration or Failures
• Chapter IV - Inspection Tools
* Chapter XI - Pipe, Valves, and Fittings
• Chapter XII - Foundations, Structures, and Buildings
• Chapter XVI - Pressure-Relieving Devices
4.1.2 Description of Condition
Tho inspection procedures (see 4.1.1) should yield a description
of the condition of the tank required for the review. Specifically, in
addition to data demonstrating that the tank is ,in good condition, the
inspection report should give (1) the actual thickness of steel in the
vertical wall and the location of where it is thinnest, and (2) similar
data for the bottom. These data will provide the basis for determining
a minimum wall thickness to sustain the operating stresses and for
determining how much corrosion allowance will exist initially.
-------
4-5
The methods available to determine wall thickness include
ultrasonic and radiographic techniques and the more traditional method
of drilling and direct mechanical measurement using a hook gauge. While
the first two methods are more modern and sophisticated, they are also
more complex. The traditional method of drill, measure, and plug (with
a threaded plug) has beaen practiced for many years; properly done, it
offers no more potential detriment to tank integrity than other shell
penetrations for pipes, gauges, etc.
The applicant may measure and report thickness of each course
of metal plate in the vertical wall of a large API 620 or similar tank.
In such cases the permit writer must specify the minimum shell thickness
for each course based on a method such as is presented in Section 3.2.5.1
recalling that the pressure imposed on the vertical wall of a tank at any
level is proportional to the height of liquid above that level. After such
calculations have been performed, it will become possible to calculate the
remaining corrosion allowance for each course. This later data will be
useful in estimating the remaining service life and in specifying the
inspection frequency as discussed in Section 8.6 of this manual.
4.1.3 Estimation of Adequacy of Shell Thickness
Adequacy of wall thickness can be estimated as follows:
la. If applicant has provided data giving steel specification
and grade, reviewer can calculate ts for each course of
the tank wall by the methods of 3.2.5.1.
Ib. In cases where steel specification and grade are unknown,
require applicant to determine an equivalent specification
and grade by measuring chemical composition and mechanical
properties on samples taken from tank (see following
discussion on sampling). Analogous procedures for new
unidentified tank materials are described in API standard
650, Appendix N and in API Standard 620, Appendix B. The
taking and testing of specimens are to be performed by a
qualified testing laboratory; repair of the areas from whi.r,
-------
4-6
specimens are taken should be done by a qualified welder
using steel material and procedures appropriate to a
suitable design standard and the planned operating
conditions. Given a specification and grade for the
steel in each course, a value of t can be calculated
as In la above.
2. Compare the calculated values of t with the actual minimum
thickness of each course as reported from the inspection.
Any excess of actual minimum thickness over the calculated
t for a course can be considered to be a corrosion
allowance for that course. The least such corrosion
allowance for all the courses may be used as the corrosion
allowance for the tank.
3. If the comparison in 2 shows for any course that the cal-
culated t is greater than the actual minimum thickness,
then the permissible maximum height of liquid in the tank
must be reduced to a value which will yield an acceptable
corrosion allowance. See 3.2.5 1, Equation 5.
As partially indicated in the discussion of determining shell
thickness, samples may be taken from a tank for chemical ana:^ ; or even
for determination of mechanical properties; sampled locations, when properly
repaired, represent little significant difference- in characteristics
from original tank attachments or penetrations. The safety factors
implicit in allowable stress levels and in weld efficiency factors allow
for initial tank fabrication and subsequent repairs.
Typically, a sample for chemical analysis would be obtained
in the form of drill chips and be on the order of five grams or less in
size. Judicious selection of sample numbers and locations would be part
of the exercise of material identification. The sanple(s) should truly
reflect shell composition, i.e., not weld metal; any traces of surface
coatir.gs or contamination should be discarded or avoided during sampling.
If samples for mechanical property tests are taken, choice
of test specimen size would be involved and might, for example,
-------
4-7
a I";';* for test specimens in the range of 1" x 8" to 2'1 x 12" for -ensile
testing. Cnce the properties of the shell are determined, a repair with
suitable ma tens Is and welding (if a metal tank) procedures can bt
jefineu. Acain, a judicious choice of sar.ple numbers and location should
be evidenced, with consideration for measurement of representative pro-
perties anj reliability of repair.
A.I.A Use of Tank History
It may be imrractical for tne cermit applicant to provide a -ecent
cecnrvcal description of condition as Jescribed in sections 4.1.2 and 4.1.3
Jtcve. For example, the applicant may be processing hazardous wastes in an
e^ist'ng facility rsinc tanks that were purchased new several years ago or
jsi>; tanks that were irsta'lled (or used in place) after having been used
f^r other service.
The applicant may believe it premature to stop processing wastes
*:r a detailed tank insoection.
Under carefully selected conditions, the permit writer may accept
•\ tack n! story in lieu of a recent inspection. The primary
conation would be that it is not timely to require thai; a tank inspection
ie ^»rfor""td !~ased on the permit writer's judgment of the required fre-
H-.'^CV of tank inspection described in section 8.6 of this manual. Of course,
'* v.~pr chemicals or liquids have ever been stored or processed in the tank
5'-.;^ the detailed description of tank condition was prepared, tnen the pre-
-^ -e: corrosic-. rate under that condition and the possibility of non-uniform
c:--csion ~ust also be defined. Nevertheless, the permit writer should
"c;L.Tre that tank inspections be perforrcd in the future consistent with
a i'--?;onceived schedule.
L: t' ~a.tion of Service Life of Used Tanks
'-.a-rles of row to esf'".3te the e-rected service life or used tanks
n a
section of this ~anual--3.. .6.4.
-------
4-8
4.2 Fiberglass-Reinfo_rce_d_Plastic Tanks
Fiberglass-reinforced plastic tanks (FRP tanks) are frequently
encountered in permit applications because they are relatively inexpensive
and have excellent ''corrosion" resistance to many chemicals. Unfortunately,
the only "official" standard issued about FRP tanks was for'underground
storage of petroleum based fuels and oils at atmospheric pressure; this
standard was issued by ASTM. In addition, UL has proposed a standard for
nearly the identical service. Thus, the standards and codes for FRP tanks
have not been well developed.
°art of the problem in preparing such codes or standards is that
a very large array of specific plastic materials or formulations can be useci
as the "corrosion" barrier and as the matrix material to bond the fiberglass;
•^anv different ^orms of fiberglass may be used, including chopped individual
fibers, woven mats, and highly oriented filament winding; and several fab-
rication methods are available. The standards that have been written to date
do not provide design procedures, but rather, impose performance requirements
and cite some specifications.
Many cf the FRP tanks to be used in hazardous waste facilities are
likcl. lo r.ave ueen fabricated according to the specification issued by the
-anufacturer of the tank. The permit writer should be prepared for cases
in rth-^ch no reference to the ASTM (or tentative UL) standard is made by the
rant- manufacturer in a tank specification. In many respects, the FRP tank
32icifications issjed by a manufacturer are likely to be similar to ASTM
r^C2!-3l or UL 1316 (tentative); however, the manufacturer is likely to be
-•-.:! "-ore specific about standard materials, fabrication methods, tank
STX-S and configurations available, and otner design details. The ASTM and
tentative UL standards are presented in the next section.
-.2.1 Standards and Codes
Fiberglass-'-einforcea plastic tanks intended for use in the petroleum
:r cre.-ica1, ;:rccessinq industries may be soecified to meet certain codes or
;t>,-.;:d<-.:!:. such 2? iS~M cr UL.
-------
4-9
4.2.1.1 4STM 04021-81
Title: "Standard Specification for Glass-Fiber-Reinforced
Polyester Underground Petroleum Storage Tanks"
Scope: Specification covers fiberglass-reinforced horizontal,
cylindrical, and spherical-type underground tanks for
atmospheric pressure storage of petroleum-based fuels
and oils. The specification covers the materials, the
manufacture, workmanship, external load requirements,
internal pressure, fitting-moment load and torque load
ratings, leakage, internal iirnact resistance, chemical
resistance, quality control, end test methods.
4.2.1.2 UL 1316 (Tentative]
Title: "Proposed First Edition of the Standard for Glass-Fiber-
Reinforced Plastic Underground Storage Tanks" (January,
1982 draft)
Scope: These requirements cover spherical or horizontal cylindrical,
atmospheric-type tanks of fiberglass-reinforced plastic (FRP)
that are intended for the underground storage of petroleum-
based flammable and combustible liquids. These tanks are
completely assembled and tested for leakage before shipment,
and intended for installation and use in accordance with the
Standard Installation of Oil-Burning Equipment, NFPA No. 31,
and the Flammable and Combustible Liquids Code, NFPA No. 30.
The standard allows for the incorporation of manholes; there-
fore, 40 CFR 264.191(a) which states "The regulations of this
Subpart [Subpart J - Tanks] do not apply to facilities that
treat or store hazardous wastes in covered underground tanks
that cannot be entered for inspection", will remove from con-
sideration tncse tanks fabricated without manholes.
-------
4-10
4.2.2 Evaluati.n at Fiberglass-Reinforced Plastic Tank Applicability
The regulations in Title 40 CFR were not writtan with the use of
fiberglass-reinforced pi.is tic (FRP) tanks in mind. Metal tanks fail by the
process cf corrosion or erosion that involves the. removal of metal from the plates
of the tank, and the concept of minimum shell thickness is generally valid; both
of these processes result in metal thinning. Conversely, FRP tanks may fail by
processes that actually swell the plastic and eventually allow delamination of
the tank. Thus, the concept of minimum shell thickness is not directly applicable
to FRP tanks. Furthermore, unless metal tanks are clad, lined or coated, the
standards, by implication, are able to assume that the metal is homogeneous for
design computations. (Actually, metals are r.ct homogeneous on a molecular or
crystalline basis.) Conversely, as indicated previously, most FRF tanks are
realTy fabricated as laminations that may involve several plastic formulations,
several forms of fiberglass, and several techniques of fabrication in each tank.
Thus, the tank cannot be conceived of as being of a homogeneous material. Many
different proprietory materials and procedures are available to the manufacturers
of such tanks. Because of these facts, it is impractical for the permit writer
to ccr.sidor ^3e of design procedures or Computations to verify the adequacy of
tank design.
Based on the above information, it is clear that the permit writer
must rely on information submitted by the permit applicant to determine the
applicability of a specific FRP tank to a given hazardous waste service. Such
information submitted by the applicant should preferably be copies of a tank
specification and/or other engineering information submitted by the tank
manufacturer to the applicant about the tank purchased and its applicability to
the intended service. That is, the applicant should havs requested a tank using
materials of construction compatible with the specific hazardous waste, under
specific maximum operating conditions of pressure, temperature, and liquid level;
if the specific gravity of the liquid were greater than 1 (62.4 Ibs/cu. ft.), this
should nave been specified too. The manufacturer should have responded that
the tank purchased would be suitable for such service.
-------
4-11
The permit writer may receive less information from the applicant
than the ideal presented above. In such cases, the permi't writer must exercise
judgement in the determination or whether the information is sufficient, specific
to the application, relatively unbiased, and reflects adequate engineering
analysis. Analysis of data from NACE (See Appendix E) may indicate no problem
of incompatability. General brochures or specifications may be adequate if the
tank is to be operated at ambient temperatures and atmospheric pressure with a
liquid of a relatively low specific gravity. However, if higher pressures or
temperatures are involved, or if NACE presents no data or some problem is
indicated by NACE, the permit writer should use caution.
4.2.3 Mini mem Shell Thickness Equivalent
FRP tanks are more likely to fail due to reaction, softening, swelling,
or crazing than to wall thinning (through dissolution). Thus, the minimum shell
thickness requirement should be specified such that no fiberglass shall be
exposed and the tank shall show no significant deterioration upon visual inspection
as evidenced by obvious wall thinning, discoloration, disintegration, crazing,
softening, swelling, indentations or delomination. Many tanks will be sufficiently
translucent to also inspect the tank for porosity, air or other bubbles, and other
inclusions.
-------
4-12
4.2.4 Frequency of Inspections
Because of the manner in which FRP tanks fail, the general lack of
published public data on service life of such tanks, and, th? fact that FRP
tanks have not had a long history of use, the best recommendation on frequency
of inspection is likely the manufacturer of the tank cr possibly, others (such
as manufacturers of chemicals) that have used the same or a similar plastic
material formulation for the corrosion barrier to contain similar liquids.
The tank manufacturer should be made aware that leaks or spills cf the
hazardous waste are intolerable and must be avoided through adequate inspections.
Generally, the permit applicant should be required to obtain such information
from the manufacturer and incorporate it in the permit application for FRP
tanks.
In specifying the inspection frequency, the permit writer should not
be unduly concerned about using relatively long inspection periods if the
plastic used is ~ot attacked by the hazardous waste. Service life under these
conditions could be indefinite. Furthermore, upon detection of significant
deterioration, the tank should either be repaired or removed from service; the
concept of the wall thinning to the minimum shell thickness is not applicable tc
FRP tanks.
Similar to the situation for metal tanks, there are certain practical
considerations tha: the permit writer can apply in establishing the frequency of
inspection. (See section 8.6.2.)
4.2.4.1 Imnersed Test Specimens. Users of FRP tanks for liquid
storage should be encouraged to use appropriate test specimens immersed within
the tank as indicators of the tank condition if the compatibility of the plastic
with the liquid is uncertain. Such specimens may not only be visually inspected,
out also tested for strength, hardness and weighed either for weight gain or
loss. Further discussion indicating the general concept (for metal tanks) is
presented in Section 8.6.2.2 of this manual.
-------
4-13
4.2.4.2 External Inspection^. External inspection of FRP tank is
not effective in the determination of the condition of the interior. Therefore,
more frequent detailed external inspections would have no practical impact on
the desired frequency of internal inspections.
4.3 Rectangular (Polygonal) and Other Non-Standard Metal Tanks
Permit applications may be prepared for facilities that use or may
use, non-standard metal tanks. Although such tanks may be entirely suitable
if they are properly designed, special problems are imposed on the permit
writer in such cases. Such tanks may be fabricated in either the typical
cylindrical configuration or may be composed of a large number of flat plates.
4.3.1 Cylindrical Metal Tanks
If non-standard cylindrical metal tanks are included in the permit
application, then the applicant should provide all detailed drawings and design
calculations to enable a mechanical (or equivalent) engineer to verify that the
tank is suitable for the intended service. It may be possible for the applicant
to cite a standard after which the tank was patterned if departures from such
a standard are not severe; in this case, the task of review engineer may not
be intensive. Conversely, if no such comparable standard is available, then
the task may become burdensome and require the assistance of a tank design
specialist.
4.3.2 Rectangular (Polygonal) Metal Tanks
Reviewers should anticipate receipt of applications for tanks
that are not cylindrical, such as are covered by API 620 or API 650, et al,
but are constructed entirely with flat plates fastened together by some means.
Such tanks necessarily involve intersections of the sides with each other which
are plane angles, and similarly for intersections of sides with the (flat) botru
If the tanks are rectangular, the angles will be 90 degrees. There is no re-
cognized code or standard for the design, fabrication, inspection, testing, o<-
certification of such tanks.
-------
4-14
According to 40 CFR 264.191(a), the regional EPA administrator
fcill rely on appropriate industrial standards and other available information
in the reviewing and permitting process. Since there is not an applicable
code or standard for metal tanks constructed entirely with flat plates, the
burden will be on the applicant to provide sufficient data on the materials,
design, fabrication, inspection, and testing such that the design may be
reviewed in detail by a qualified engineer. The permit writer should
anticipate that review will require engineering expertise at the completeness-
'•Jidv.k phase and detailed engineering analysis at the technical-evaluation phase.
4.4 Concrete Tanks
Concrete tanks are used for storage of waters and aqueous solutions
of inorganic materials, as settling tanks and may be the subject of an application.
Thus, standards issued by the American Concrete Institute are presented in
this section. The National Association of Corrosion Engineers also report
some data for concrete (see Appendix B).
If a storage facility is to use concrete tanks for hazardous wastes
then the burden should bs placed on the permit applicant to provide information
justifying the compatibility of the tank with the liquid, standards used in
fabrication, and the engineering design computations. In addition, the appli-
cant should provide criteria and justification for the criteria for taking the
tank out of service and for a suggested frequency of inspection.
t
4.4.1 Standards and Codes
As with other types of tanks, such as steel tanks, the design and
construction of concrete tanks is covered by various standards, depending on
the intended use. The principal source of data, recommended practice, and
standards for the use of concrete is the American Concrete Institute (ACI)
(address: Box 19150, Redford Station, Detroit, MI 482"i9). The ACI publishes
various standards, guides, reports, etc, each of which is available separately.
The ACI also publishes periodically its ACI Manual of Concrete Practice wlvch
-------
4-15
is a large, three-part reference work containing the current editions of
standards, guides, reports, etc. The contents of the ACI Manual of Concrete
Practice (1979) are current committee reports and standards concerned with:
Part 1: Materials and Properties of Concrete
Construction Practices and Inspection
Pavements and Slabs
Part 2. Notation and Nomenclature
Structural Design
Structural Specifications
Structural Analysis
Part 3: Products and Processes.
The scopes of those items considered most pertinent for EPA reviewers are
summarized below.
4.4.1.1 ACI 318-77
Title: ACI Standard. Building Code Requirements for Reinforced
Concrete
Scope: This is the basic standard for the proper desion and
construction of buildings of reinforced concrete. It
covers (1) standards for tests and materials, (2) concrete
quality. (3) mixing and placing concrete, (4) formwork,
embedded pipes, and construction joints, (5) details of
reinforcement, (6) analysis and design, and (7) structural
systems. The code provides rrim'Mum requirements for design
and construction of reinforced concrete structural elements
of any structure erected under requirements of general
building codes, but does not specifically cover tanks. The
code states that for special structures, including tanks,
provisions of this code shall govern where applicable.
-------
,4-16
R-77
Title: Concrete Sanitary Engineering Structures
Scope: As indicated by "R" in the ACI designation, this is for
a committee report, and as such contains recommendations
for structural design, materials, and construction of
concrete tanks, reservoirs, and other structures commonly
used in water and waste treatment works where dense,
impermeable concrete with high resistance to chemical
attack is required. Special emphasis is placed on designs
which minimize cracking and accommodate vibrating equipment
and other special loads. Chapter 5 - Protection Against
Chemicals - states that concrete made with the proper type
of cement, which has been properly proportioned, mixed,
placed, and cured, will be Jense, strong, watertight, and
resistant to most chemical attack; therefore, under ordinary
service conditions, quality concrete does not require
protection against chemical deterioration or corrosion.
However, in industrial waste treatment plants, where the
pH of acid waste may go as TOW as 1.0, the types of protection
generally used are chemi cal -resistant mortar, acid-rproof brick
or tile, thick bituminous coatings, epoxies, and heavy sheets
or liners of rubber or plastic.
4.4.1 .3 ACI 201.1 R-68
Title: Guide for Making a Condition Survey of Concrete in Service
Scope: This guide provides a system for reporting on the
condition of concrete in service. It includes a check
list of the many details to be considered, and provides
standard definitions (with pictures) of 40 terms associated
with the durability of concrete.
-------
4-17
4.4.1.4 ACI 311-75
Title: Recommended Practice for Concrete Inspection
Scope: This document sets forth standards and procedures
relating to concrete construction which will serve
as a guide to owners, architects, and engineers in
planning inspection programs.
4.4.1.5 ACI 311.1 R-75
Title: ACI Manual of Concrete Inspection
Scope: This 275-page book is intended as a supplement to
specifications and as a guide in matters not covered
by specifications. It includes information on inspection
fundamentals, proportioning and control of mixes, testing
of materials, inspection before, during, and after con-
creting, sampling, and tests of fresh and hardened concrete
-------
5-1
CHAPTER CONTENTS
CHAPTER 5
5.0 TANK ANCILLARIES: PRESSURE AND OTHER CONTROL SYSTEMS
5.1 Internal Pressure and Pressure Controls
5.1.1 Internal Pressure
5.1.2 Venting or Pressure Relief
5.1.2.1 Venting and Pressure Control for API
Standard 620 Tanks
5.1.2.2 Venting and Pressure Control for API
Standard 650 Tanks
5.1.3 Vapor Recovery Systems
5.1.3.1 A Common Vapor Recovery Syst?m
5.2 Other Controls and Instruments
5.2.1 Process Control—Simpl ified
5.2.1.1 Fail-Safe Positioning
5.2.2 Process Variables Requiring Measurement
5.2.2.1 Temperature
5.2.2,2 Pressure
5.2.2.3 Flow Rate
5.2.2.4 Level
5.2.2.5 Liquid Specific Gravity
5.2.2.6 Other Variables
5.2.3 Overfilling Control Systems
5.2.3.1 Flow Measurement >
5.2.3.2 Liquid-Level Measurement and Control
5.2.4 Freeboard
-------
5-2
5.0 TANK ANCILLARIES
PRESSURE AND OTHER CONTROL SYSTEMS
In brief outline format, the Title 40 CRR regulations require
the following pertaining to design of pressure and other control systems:
t A diagram of piping, instrumentation, and prqcess
flow [270.16(d)]
• Description of feed systems, safety cutoff, bypass systems,
and pressure controls [270.16(e)]
• Review of the design of pressure controls for closed
tanks to assure that they do not collapse or rupture
[264.191(a)]
• Use of appropriate controls and practices to prevent
overfilling [264.192(a)(2)].
All such control systems should be diagrammed on a piping and
instrumentation diagram (P&ID), which was described in an earlier section
of this manual (Section 2.2).
Internal pressure and pressure controls are presented in Section
5.1 and other controls and instruments are presented in Section 5.2 of this
manual.
5.1 Internal Pressure and Pressure Controls
Tanks are designed to withstand working or design pressures (or
vacuum—an external pressure) up to specified limits as indicated in
Section 3.2 of this manual. Tanks designed according to standards or codes
often appear to have inherent theoretical safety factors in the range of
about 3 to 5; however, the reason the standards were initially developed
w-:s because failures were occurring with smaller safety factors. Thus,
thn acceptable working or design pressures should not be significantly
pxceeded under plant operating conditions. (Nevertheless, tanks and pressure
vessels are frequently hydrostatically tested with water under safe con-
ditions at about 150 percent of the design pressure.)
-------
5-3
The following sections briefly discuss internal pressure, venting
or pressure relief, and vapor recovery systems.
5.1.1 Internal Pressure
For an open (uncovered) tank, the only pressure imposed on the
tank is that due to the hydrostatic head imposed by the neight (or head)
of the contained fluid. Engineers may measure this literally as feet of
water or contained fluid. Conversion to a more conventional pressure unit,
pounds per square inch (psi), is accomplished oy multiplying the feet of
head by the density of fluid in pounds per cubic foot, divided by 144 to
convert pounds per square foot to pounds per square inch; for example,
. . , . (1 foot) (62.4 pounds/cubic foot)
i TOOL of water = -> '—> ' :— __~~_j.
(144 square inchs/square foot)
= 0.433 psi.
A closed Lank will nomally have a pressure at least squal to the
hydrostatic head plus t-he vapor pressure at storage temperature of tne
contained liquid. Vapor pressures r,ay be determined for many chemicals
and other liquid products by reference to standard handbooks; nevertheless,
the permit applicant should provide the vapor pressures for the volatile
liquids (or mixtures) to be stored in the facility. Such vapor pressures
are often cited in units of millimeters of mercury (mm Hg) or atmospheres
(atn) and may be converted to psi by knowledge that the following are
eciui val ent:
760 mm Hg = 1 atm = 14.7 psi.
However, the pressure in closed tanks can be increased to
hazardous levels due to a numuer of other factors including:
• Forwarding liquid cr gas into tne otherwise closed
tank from a higher pressure source such as a pump,
compressor, or gas cylinder
-------
5-4
• An increase in the storage temperature resulting in
increased vapor pressure because of an increase in
ambient temperature, the introduction of hot fluid
to the tank, tank overheating, or exposure to fire.
Similarly, the pressure in the tank may be reduced by the converse of the
above; that is,
t Pumping or draining the liquid out of an otherwise
closed tank
« Reducing the liquid storage temperature such as
caused by a decrease in ambient temperature.
In some cases, pressure reduction may bd sufficient to create a vacuum
in a tank such that the tank will collapse due to the external pressure
imposed by the atmosphere on the tank.
5.1.2 Venting or Pressure Relief
Venting or pressure relief for tanks performs two general
functions:
• Allows air, inert gas, or other blanket gas into the
tank or allows vapor to escape from the tank. In this
manner the internal pressure of the tank will be main-
tained either at atmospheric pressure or within the
pressure limitation of the tank design to preclude rupture
or collapse of the tank.
• Serves as a collection point for vapor emissions. Such
vapor emissions may then be recovered or treated to avoid
emission to the environment.
Venting or pressure relief devices for use on petroleum
product tanks are categorized by API Standard 2000 "Venting Atmosphere
and Low-Pressure Stor?ge Tanks", as either normal or emergency vents.
Normal vents include:
• Pilot-operated relief valvas (of 3 fail-safe type, which
excludes use of the weight and l
-------
5-5
• Pressure relief valve (for tanks operating above
atmosphere pressure)
• Pressure vacuum valve (for tanks where a vacuum can
be created)
• Open vents with flame arrester (for petroleum products
with flash points below 100 F or on tanks where the oil
is heated above the flash point)
« Open vents (for petroleum products with flash points
above 100 F, tanks where the oil is heated but below the
flash point, or tanks less than 2500-gallon capacity of
petroleum products)
Emergency vents include:
• Larger or more open vents, but only where open vents
may be used
• Larger or more pressure vacuum valves or pressure relief
valves
• A gage hatch or manhole where a cover will lift if high
internal pressure is experienced
• A weak seam connection between the roof and shell of
the tank
• Other forms of construction comparable for pressure
relief purposes (rupture or frangible disks, which are
thin metallic disks, presumably fit this category).
Required venting capacity of the devices expressed in terms
of cubic feet of free air per hour for both "normal" and ''emergency
venting for fire exposrue" is presented in API Standard 2000, Sections
2 and 3, respectively. NFPA 30 also presents comparable information
in Sections 2-2.4 and 2-2.5, respectively.
-------
5-6
5.1.2.1 Venting and Pressure Control for API Standard. 620 Tanks.
Tanks built to the design rules of API Standard 620 shall be equipped,
within the pressure limits of the standard, with pressure-relieving and
emergency vacuum-relieving valves. The standard stipulates specific
limits of pressure excursion above the maximum allowable working pressure,
for the provision of supplementary pressure-relieving devices where a
tank may be exposed to accidental external fires, and contains recommen-
dations regarding the materials, the construction, and types of devices.
A tank which is likely to operate completely filled with liquid
shall also be equipped with me or more liquid-relief valves ft the top
of the roof.
The relieving devices for gases, if not on the roof, shall be
installed on the connected piping, if any, as close to the tank as practical;
and if vented to atmosphere, at a sufficient height to prevent any chance of
ignition (see API Standard 2000: "Venting Atmospheric and Low-Pressure
Storage Tanks").
5.1.2.2 Venting and Pressure Control for API Standard 650 Tanks.
Appendix F of API- Standard 650 provides for the design of closed-top tanks
to operate with small internal pressures, up to a maximum of 2.5 psig.
Such tanks shall have vents sized and set so that at their rated capacity,
the internal pressure under any normal operating condition shall not exceed
either the internal design pressure, P, or the maximum design pressure,
Pmax- For definitions of these pressures and methods of their calculation,
see Section F.5 of the Standard.
For certain design conditions specified in F.2.2 of the Standard,
emergency venting devices conforming to API Standard 2000 shall be provided.
5.1.3 Vapor Recovery Systems
Vapor recovery systems have sophisticated pressure-sensing and
pressure-control instrumentation that maintains vapor pressure eouilibrium
during all periods ot tank operation. These systems collect the vapors
and are frequently followed by a treatment process that either renders the
vspcr harmless for venting to the atmosphere or converts it to a product
-------
5-7
that has market value. The liquid may also be recycled. Common treatment
methods include compression, absorption, and condensation. If the product
has no value, it can be disposed of by flaring, incineration, or other
methods. Two configurations of vapor reccvery units are used: (1) indi-
vidual units for each tank and (2) cor/inon vapor recovery units for a system
of two or more tanks that are being used t.o store wastes wtth similar
vapor chemical compositions.
The following items should be considered when evaluating vapor
recovery systems:
• When more than one type of waste is handled, compatibility
must be determined; when the wastes are incompatible, their
vapors may also be incompatible and separate vapor recovery
units would be appropriate.
• Vapor recovery systems must bi= maintained at airtight
conditions to preclude leakage.
t The vapor recovery pipe' should be sloped down to a common
place where condensation can be collected. In addition, the
linear velocity of vapor must be maintained under design
limitation to preclude excessive turbulence, vibration, etc.
The permit writer should review the process flow diagram (PFD) that depicts
the direction of vapor and fluid movements to evaluate factors such as the
following:
• Is there a vapor recovery system or other method of
recovery to accommodate incompatible wastes? (Incompatible
wastes should not utilize a common vapor recovery system.)
6 If compatible wastes *re going to be handled, are there
separate piping systems?
5.1.3.1 A Common Vapor Recovery System. A common vapor recovery
system which connects all the tanks and process equipment in a facility
collects all excessive vapors generated and disposes of them in an environ-
mentally acceptable manner (treatment system flaring, etc.). It consists
of an interconnecting piping system with manifolds and headers linking all
the vents, plus pressure and temperature instrumentation. The common vapor
recovery header serves to form a pressure-balancing system.
-------
5-8
The design of a common vapor recovery system requires the fol1owing
information:
1. Properties of the Fluid. The properties of fluid in.storage,
especially the degree of volatility, are directly linked to the header size.
For example, relevant fluid properties of facilities storing hydrocarbons
include the fluid specific gravity, the flash point temperature, weight per-
cent solids, weight percent water, viscosity at the storage temperature,
amount of dissolved inert gas, amount of dissolved and free phase water,
and the vapor pressure at storage condition.
2. Design and Normal Operating Conditions. The design and
normal operating conditions of the facility, primarily temperature and
pressure, are linked to the breathing requirement. The breathing in turn
affects the header size.
3. Capacity Requirements. The capacity requirements refer to the
vapor recovery system's vents. They must be designed to accommodate the
expected volumetric flow rate, e.g., fill rate when pumping.
4. Vapor Recovery Methods. Vapor recovery methods, such as
compression, cooling, or the combination of both, affect the venting design.
The selection of a recovery method is primarily dictated by cost.
An example of a common vapor recovery system for an oil refinery
storage facility is shown on the simplified process flow diagram (Figure
5-1). Crude oil from shipment 1s first stored in tanks, then pumped to
different treatment units and refined into gasoline, kerosene, diesel, and
other products. On the process PFD, each stream is numbered. In a
complete PFD, a mass balance table would also be included; the sizing of
tanks, pipelines, and process equipment is always based on the maximum
flow. Note that the tanks are either blanketed with nonreactive gas or
natural gas. Under normal operating conditions, there is no vapor from
nonreactive gas-blanketed tanks.
The vent gas from the tanks flows to the first stage knockout
drum. Upon entering the drum, some mist condenses and 1s collected at
the drum bottom and pumped back to the storage tanks. The vapcr is con-
densed by compression and cooled by ? heat exchanger. The condensed
liquid 1s collected at the liquid recovery drum bottom and pumped back
to the storage tanks. The non-condensed vapor is sent to a flare. Tho
-------
NITROGEN
NATURAL CAS
OILY WATER
T« TREATMENT
OIL T« STORAGE
Note: Numbers indicate stream numbers.
Source: Fred C. Hart Associates, Inc.
FIGURE 5-1. SIMPLIFIED PROCESS SLOW DIAGRAM, COMMON VAPOR RECOVERY SYSTEM
-------
5-10
natural gas blanket and tank vapor goes through a scrubbing process before
going throun;: the compressor-knockout drum recovery process.
5.2 Other Controls and Instruments
Section 5.1 discussed internal pressure, pressure controls,
and vapor recovery systems. The purpose of this section is to discuss
other controls and instruments. However, it should be noted that some
of the controls discussed in this secticn may be related to pressure
controls. For example, if the temperature rises in a closed tank con-
taining a volatile liquid, then the pressure will rise; however, che
temperature may be controlled by cooling the contents of the tank with
cooling water and, thus, reduce the pressure.
As was mentioned previously, all such control system? should
be diagrammed on a P&ID and, as required in 40 CFR ?70.16{e), the applicant
should present a description of the feed, safety cutoff, and oypass system.
Title 40 CFR 264.192(a)(2) requires the use of appropriate controls and
practices to prevent overfilling.
Process control is a very complex subject that is far beyond
the scope of this manual; for example. Perry's Handbook (Chemical Engi-
..-aers' Handbook, Fifth Edition, R. H. Perry and C. H. Chilton, Editors,
McGraw-Hill, New York, 1963) presents a 148-page chapte^ on the subject
which is an excellent summary. Therefore, this section of the manual
should be considered very elementary and pragmatic in nature.
5.2.1 Process Control—Simplified
The following presents a very simplified description of a typical
process control system to illustrate the principles involved.
The first step is to sense (or measure) that some process con-
dition such as temperature, pressure, flow rate, level, physical property
(density, viscosity, etc.), or chemical analysis is either desirable or
undesirable. Such a sensing device may create a signal that is convenient
for use, such as a thermocouple generating a voltage which may be transmitted
Conversely, a liquid-level float floating on top of the surface of liqvid
-------
5-11
creates no signal; however, the float connected to a lever may be used to
throw a switch allowing current to flow, which signals that the level is
too high (or low). Thus, the second step may be to convert the action of
the sensing device to a signal that may be transmitted; transducers are
often required to perform this second step.
The third step is to transmit the signal to a control (or indi-
cating) instrument or an alanr.. If the instrument is only
an indicating instrument or an alarm, all subsequent control functions
must be performed manually. However, if a control instrument (or con-
troller) is used, then in the fourth step it will generate a signal to
a control device such as a control valve or pump switch. This latter
signal is often either electrical or pneumatic. In addition, this latter
signal may be of an on or off nature to tell the "final control element".
such as a valve, to either open fully or close fully, or it may be pro-
portional—that is, the valve should open (or close) proportional to the
amplitude of the signal.
In the fifth step, the final control element may turn off a pump
switch to stop a tank rrom overfisling secause 3 hign-1iquid-level switch
has been activated, or it may open a steam valve a little bit more to the
shell side of a heat exchanger because the temperature inside a tank has
cooled to just below an acceptable level.
Process controls can become very complex and involve feedback
control where the poor operating condition is corrected by controlling
sore device ahead of the point at which the condition is measured. Alter-
natively, a fesd-forvard control system may be used when; a poor operating
condition is anticipated unless something is done; for example, if the feed
rate is increased, then a control valve to allow more cooling water into a
heat exchanger may be opened further to assure adequate cooling. Many
chemical manufacturing plants now use computers for optimized process
control.
5.2.1.1 Fail-Safe Positioning. In analyses of process control
systems, the permit writer should determine that if power outages or instru-
ment air failures were to occur, then the final control elements would
position themselves in a fail-safe orientation. Control valves and
-------
5-12
electrical switches can be selected such that upon instrument air or power
failure, the final control elements would be either fully on or off (or
fully open or closed). Thus, the permit applicant should fully describe
the position of the final control elements upon either a power or instrument
air failure and present adequate discussion to indicate that such a
position is the fail-safe position.
5.2.2 Process Variables Requiring Measurement
Process variables need to be measured and maintained routinely
at certain values. These variables arc monitored by electrical, mechanical,
or chemical devices. The following measures should be taken regularly to
ensure safe operation of a hazardous waste tank facility. The permit writer
should cetermine whether or not procedures needed to measure these variables
are adequate.
5.2.2.1 Temperature. Abnormal temperatures may indicate tnat
undesired reactions are occurring in the tan*, excessive heat is being
generated, hazardous vapors ara being emitted, etc. Excessive temperature
may also cause a higher pressure in the tank.
5.2.2.2 Pressure. Measure pressure to ensure that design pressure
of a tank is not being exceeded.
5.2.2.3 F'ow Rate. Measure flow rate to preclude overfilling of
a tank, etc.
5.2.2.4 Level. Measure level to preclude overfilling and main-
tain the desired liquid level.
5.2.2.5 Liquid Specific Gravity. Measure specific gravity to
ensure that weight of liquid does not place excessive stress upon the
tank.
-------
5-13
5.2.2.6 Other Variables. Under specific conditions it ray be
appropriate to measure other variables such as pH, flash point, chemical
analyses, or moisture content to assure that the system is operating
properly or that the liquid is not corrosive to the tank. However, the
ones mentioned above are most important to assure proper tank operation.
Refer to Perry's Chemical Engineers' Handbook, Fifth Edition,
Chapter 22, for a description of measurement devices.
5.2.3 Overfilling Cor-trol Systens
Title 40 CFR 264.192(a)(2) states that tanks must be equipped
with overfilling control systems. The two most important components of
overfill ing .control, flow measurement and level measurement, are discussed
below.
5.2.3.1 Flow Measurement. Monitoring of the flow rate into a
tank can be used to prevent overfilling or pressure buildup due to an
increase in the feed rate without a corresponding increase in the efflu-
ent rate. However, flow rate measurements alone are insufficient to pre-
vent overfilling. A complete overfilling control system shou'ld also
include at least one of the following systems:
(1) An alarm triggered by excessive flow rate and also a
feed cutoff valve accessible to the operator
(2) An open by-pass line to an empty or nearly eropty stand-
by tank, or
(3) A feed cutoff system or alarm triggered by a liquid-
level measurement device as described in the following
section (5.2.3.2).
5.2.3.1. Local Static Pressure. The internal pressure on the
surface of the pipe is measured by making a small internal hole perpen-
dicular to the surafce and connecting and opening to a pressure-sensing
elenent.
-------
5-14
5.2.3.1.2 Velocity Meters. Pitot tubes measure local velocities
by measuring the difference between impact pressure and static pressure.
5.2.3.1.3 Pressure Meters. The rate of flow through the pips
is calculated from ten pressure drop caused by a constriction such as
an orifice.
5.2.3.1.4 Mass Flowmeters. The mass flow rate can be measured
directly by creating angular momentum with an impeller and then measuring
the torque this mu'i.entum imparts to a tubine, or the volumetric flow rate
can be measured and the mass flow rate calculated using fluid density.
j.2.3.2 Liquid-Level Measurement and Control. One of the most
effective means of preventing overfilling in a tank is through the use of
a liquid-level measurement device connected to an alarm or automatic feed
cutoff system; another effective means of preventing overfil 1 ing is by
allowing the tank to overflow to another tank. Several types of liquid-
level measurement devices are discussed ceiow, any of wmcn could be used
to control a switch for an alarm or feed rutoff valve.
In some cases where float-activated (see below) devices ar? used,
four liquid-Tevel measuring devices may actually be installed on the tank.
They include the following:
• High liquid level (HLL). which indicates when the liquid
level has reached the design capacity of the tank
• Low liquid level (ILL), which indicates when the liquid
level is low
• Level alarm high (LAM), which indicates when the liquid
has reached the dangerous level. If the situation is not
rectified, the waste will overflow from the tank.
• Level alarm low (i_AL). which indicates when the liquid level
has reached a dangerous level for the pump. If the situa-
tion is not rectified, pump cavitatinn can occur because of
pumping air instead of liquid.
-------
5-15
In other cases, when other types of devices are used, such as
a head device (see below), the high and low liquid levels may be indi-
cated as points on an instruriicnt chart and the leve> alarms (high and low)
activated all through one measunny device. Nevertheless, it may be
prudent for the permit writer to require use of a backup high level alarm
system for hazardous wastes that are particularly obnoxious.
5.2.3.2.1 Float-Activated Devices. Float-activated device? are
characterized by a float en the surafce of a liquid. In one type, an
electrical switch is activated by a magnetic float.
5.2.3.2.2 Displacer Device. Displacer-activated level measuring
is accomplished through measurement of the buoyant force on a partially
submerged float. The force on the displacer (i.e., float) can be deter-
mined by measuring compression of a spring that holds the displacer in
place or through measurement of the force on a torque tube connected to
the displacar by z. rod. The range of a displacer device is limited to
Lhe length of the displacer.
5.2.3.2.3 Head Device. A variety of device* utilize hydro-
static head as a measure of level. The majority of these devices use
differential pressure-measuring devices to measure the difference in
pressure between atmospheric oressure and the pressure near the bottom
cf the tank.
5.2.4 Freeboard
In addition to overfilling controls, C'-mers-operatorj of open
tanks are required to maintain sufficient freeboard to prevent overtopping
owing to wind or wave action or precipitation. In a tank of less than ICO
meters in diameter, the maximum height of a wind-induced wave i? often
about 4 to 5 inches. Allowing another 4 tu 5 inches for splashing on the
sides and 6 inches for precipitation, 14 to 16 inche? of freeboard would
barel> be adequate for most tanks; 18 inch°s would orovide some safety
factor.
-------
6-1
CHAPTER CONTENTS
6.0 TANK ANCILLARIES: PUMPS, PIPING, AND AGITATOR STUFFING BOXES
6.1 Pumps
6.2 Piping
6.2.1 Cedes and Standards
6.2.1.1 ANSI Standard B31.3
6.2.1.2 ANSI Standard B31.4
6.2.2 Materials
6.2.3 Piping Joints
6.2.4 Piping Supports
6.2.5 Valves
6.2.6 Inspection and Testing
6.3 Agitator Stuffing Boxes
-------
6-2
6.0 TANK ANCILLARIES: PUMPS. PIPING
AND AGITATOR STUFFING SOXES
Chapter 6.0 deals with hardware-type iten.S typically associated
with t?nks such as pumps, piping, and agitator seals. Chapter 5.0 dealt
with instrumentation, pressure control, and process control-. Chapter 7.0
will deal with tank foundations, supports, thermal insulation, and
electrical grounding.
6.1 Pumps
Interim guidance is provided in the following pages, which have
been copied directly from a similar manual prepared by Fred C. Hart
Associates, Inc.
Pumps are necessary for all tank storage/treatment facilities.
The cost of pumping can be a ntfjor factor in plant design and operation.
There are three broad classes of pumps: centrifugal, rotary
and reciprocating. Table 6-1 summarizes pump classes and types.
Several factors must be considered when selecting a pump to
handle hazardous wastes. These factors include:
1. capacity
2. pump head
3. nature of liquid handled
4. cost
5. materials of construction
1. The pump capacity requirement is determined by the liquid
volume to be handled. A design safety factor is needed
* Source: T. G. Hicks and T. W. Edwards, "Pvinp Application Engineering",
New York, McGraw-Hill, 1971.
-------
6-3
TABLE 6-1. PUMP CLASSES -;ND TYPES
Class
Type
Centrifugal
(Single-stage and multistage)
Rotary
Reciprocating
Volute
Diffuser
Regenerative-turbine
Vertical-turbine
Mixed-flow
Axial-flow (propeller)
Gear
Vane
Cam and piston
Screw
Lobe
Shuttle-block
Direct-acting
Power (including crank- and fly wheel)
Diaphragm
Rotary-piston
-------
6-4
in case the flow exceeds the normal capacity. A stand-by
pump is recommended when the flow of a particular stream
cannot be interrupted.
2. The pump head requirement is primarily determined by the
height the liquid must be lifted and friction losses
exerted by piping and fittings.
3. The nature of the liquid handled, i.e., viscosity, volatility,
corrosiveness, and amount of solids in suspension,
will determine the type of pumps to be used and_the
construction materials.
4. Cost factors, in part, dictate the pumping scheme or type
of pump acceptable to a facility. Comparison of cost
factors may allow owner/operators to secure the lowest
annual cost per gallon of liquid pumped. Dependability,
ease of maintenance and repair, and flexibility are other
factors.
5. Materials used in construction are important in the
design of service pumps. Factor's include corrosioiverosion
resistance when transporting acids, alkalies, slurries, and
other liquids, ease of installation, operation, and main-
tenance, and dependability. For example, a typical
centrifugal pump for handling add and slurry can be made
of materials such as lead, stainless steel, solid plastic
or solid rubber. When special designs are not required,
rubber, teflon, or neoprene base coverings are available
for the casing, and impeller.
6.2 Piping
Although there is no direct regulatory requirements that the
permit writer review the piping associated with tanks, piping is such an
integral part of tank systems that some analysis may involve review of
piping to assure that the piping was designed for its intended use as
opposed to being put together in a configuration which has significant
risk of future failure. In support of such possible review, this section
presents the following:
-------
6-5
6.2.1 Codes and Standards
6.2.2 Materials
6.2.3 Piping Joints
6.2.4 Piping Supports
6.2.5 Valves
6.2.6 Inspection and Testing.
6.2.1 Codes and Standards
Piping Intended for use in the petroleum or chemical processing
industries is ordinarily specified to meet certain codes or standards, such
as those developed by the API, the ASME, ANSI, and ASTM. Brief descriptions
of those most likely to be encountered in connection with handling or
storage of hazardous liquids are given below.
6.2.1.1 ANSI Standard B31.3
Title: "Petroleum Refinery Piping"
Scope: B31.3 prescribes minimum requirements for the materials,
design, fabrication, assembly, test, and examination of
petiwleum refinery pressure and vacuum piping systems.
The Code applies to systems handling all fluids, including
fluidized solids, and to all types of services, including
oil, gas, steam, air, water, chemicals, and refrigerants.
Piping consists of pipe, flanges, bolting, gaskets, valves,
fittings, the pressure-centaln1 rig parts of other compon-
ents, and pipe-supporting elements.
6.2.1.2 ANSI Standard 831.4
Title: "Liquid Petroleum Transportation Piping System"
Scope: B31.4 prescribes minimum requirements for the design,
materials, construction, assembly, inspection, and testing
of piping transporting liquid petroleum such as crude
oil, condensate, natural gasoline, natural gas liquids,
liquified petroleum gas, and liquid petroleum products
between producers' lease facilities, tank farms, natura1
gas processing plants, refineries, stations, terminals,
and other delivery and receiving points.
-------
6-6
ANSI 831. 3 pennits a material to be used for piping, provided it
is listed in Appendix A of the Standard, "Allowable Stresses in Tension
for Materials", and meets requirements of the Code with respect to tempera-
ture limitations and design stresses. There are provisions1 for qualification
of unlisted materials by means of engineering calculations, experimental
stress analysis, proof testing,, and taking into account service conditions.
Reclaimed pipe or piping components may also be used, provided they
conform to a specification in Appendix A and meet other requirements of the
Code. Upper temperature limits generally will correspond to the high°r.t
temperature at which stress values are shown in Appendix A, a material may
be used at a higher temperature provided the design engineer determines that
the material is suitable for the service conditions and no prohibition appears
in Appendix A. Similarly, the lower temperature limits generally are the
"Minimum Temperatures" listed in Appendix A; a material may be used at a
lower temperature if impact testing shows that the material has adequate
toughness at the design temperatures. 831.3 has special Mmits *nd pro-
hibitions regarding certain alloys. Section 323.2.3 also presents in great
detail descriptions of impact testing methods and acceptance criteria which
shall be used when impact testing is required elsewhere in the Code, or
by engineering design.
ANSI B31.4 generally pennits only steel for pipe, and the
recognized standards for pipe steels and piping materials are listed in
Table 423.1 of the Standard. Cast, malleable, and wrought iron arc not
to be used for pressure-containing parts except under certain specific
restrictions, notably a pressure limit. Limitations on gasket and
bolting materials are also covered in the Standard in Section 425.
6.2.3 Piping Joints
ANSI 831.3 on refinery piping deals with piping joi'-.ts in
Chapter II, Part 4. Many types of joints are permitted under the standard:
welded joints; flanged; expanded; threaded; flareless and comoression;
caulked; brazed and soldered; and proprietary joints, all subject to
stated limitations. The most important specific limitations are as follow.
-------
6-7
Welded joints -
Threaded joints -
Caulked joints -
may be used 1n any materials for. .which
it is possible to qualify welding pro-
cedures, welders, apd welding operators.
Dimensional and other requirements
are detailed.
major consideration here is tight-
ness, especially for flammable
or toxic liquids, and it -is suggested that
threaded joints be avoided where severe cre-
vice corrosion or erosion may occur.
may be used only for water and
drainage service.
Brazsd and soldered Joints -
may not be used in systems contain-
ing flammable or toxic fluids.
Proprietary Joints -
may be used provided adequate pro-
vision is made to prevent separation
and provided a prototype Joint
has been subjected to performance
tests to determine the safety under
simulated service conditions.
ANSI Standard B31.4 permits fewer types of Joints tha-i B31.3: only
welded, threaded, and patented Joint?. The requirements of 831.4 for making
these Joints are qualitatively similar to these of B31.3.
6.2.4 Piping Supports
The importance of piping supports arises from the many different
sources of loads on piping systems and the corresponding need to lirait the
-------
6-7
Welded joints -
Threaded joints
may be used 1n any materials for which
1t 1s possible to qualify welding pro-
cedures, welders, and welding operators.
Dimensional and other requirements
are detailed.
major consideration here is tight-
ness, especially for flammable
or toxic liquids, and it -Is suggested that
threaded joints be avoided where sevtre cre-
vice corrosion or erosion may occur.
Caulked joints -
Brazed and soldered joints -
may be used only for water and
drainage service.
may not be used in systems contain-
ing flammable or toxic fluids.
Proprietary joints -
may De used provided adequate pro-
vision is made to prevent separation
and provided a prototype joint
has been subjected to performance
tests to determine the safety under
simulated service conditions.
ANSI Standard 831.4 permits fewer types of joints than 831.3: only
welded, threaded, and patented joints. The requirements of 531.4 for making
these joints are qualitatively similar to these of B31.3.
6.2.4 Piping Supports
The importance of piping supports arises from the many different
sources of loads on piping systems and the corresponding t.eed to limit the
O
-------
6-8
motions and stresses 1n the piping system. The conditions and Influences
which must be taken Into account in designing piping systems and their supports
and restraints include the following:
t Design pressure and temperature
»• Ambient Influences, e.g. cooling of a gas or vapor or Increased
pressure due to heating of static fluid in a piping system
t Dynamic effects, including Impact forces such as hydraulic shock
or slugging, wind, 'earthquake, vibration and discharge reactions.
t Weight Effects, Including weight of piping and weight of medium
transported
• Thermal expansion and contraction effects .
The design of the piping,Including the supports, must be made with the object-
ives of preventing the following:
• Excessive stresses 1n the pipe
• Leakage at joints
t Excessive forces or moments on connected equipment
• Excessive stresses 1n the supports
• Resonance with imposed vibrations
• Excessive interference with thermal expansion and cor.tractlon
• Unintentional disengagement of piping frcm supports
• Excessive sag in piping squiring drainage slope.
There are specifications for supports regarding materials to be used, threads,
means of attachment to pipe, etc; for details on these, see Section 321 of
ANSI 831.3 and Section 421 of MS! 831.4.
6.2.5 Valves
In ANSI 831.3, valves must comply with specifications listed In
Appendix A, Allowable Stresses in Tension for Materials, and in Table 326.1,
Dimensional Standards. Special valves not specifically covered by standards
listed 1n Table 326.1 may be used provided the designs meet Code requirements
of Section 304, Pressure Design of Components.
Similarly, in ANSI 831.4, standards and specifications for valves
are covered as follows:
-------
6-9
Steel valves Tables 423.1, Material Standards and 426.1,
Dimensional Standards and Paragraph 3.2 of
API Std 60 covering certain cast, malleable,
or wrought Iron parts.
Cast Iron valves Tables 423.1 and 426.1 for pressures not
greater than 250 psi
Special valves not listed in Tables 423.1 and 426.1 shall
be permitted provided that their design is
of at least equal strength and tightness
and will meet same test requirements as covered
In 831.4.
forking pressure ratings of steel parts of steel valves are applic-
able within temperature limitations of -20 F to 250 F.
6.2.6 Inspection and Testing
In ANSI B31.3 a distinction 1s made between Inspection and examin-
ation:
« "Examination" or "examiner" refer to quality control functions
performed by personnel 1n the employ of the manufacturer, fabri-
cator, or erector
• "Inspection" or "Inspector" applies to functions performed by
or for the owner to determine that the appropriate "examination"
has been done and that the piping tnersfore meets Code require-
ments.
This distinction is not made 1n 831.4. However, the quality control methods
to be used are similar IP 'the two codes. Generally, nondestructive examina-
tion methods are specified, and include: visual, magnetic particle, liquid
penetrant, radlographlc, and ultrasonic examination methods. 331.4 also includes
the possibility of destructive testing of welds where required by the inspector.
All of the methods are covered by sections of the Standards themselves, or
by other codes indicated. See Section 336 of 831.3 and Section 436 of 831.4
for details of examination requirements.
-------
6-10
ANSI B31.3 requires that Installed piping be pressure tested before
Initial optratlon. There 1s no exception from this requirement for hazardous
liquids. Internal pressure piping shall be hydrostatically tested at a pressure
at least 1% times the design pressure, unless the design conditions will result
in stressing of some parts at such a pressure beyond 90 percent of minimum
specified yield strength (MSYS) at test temperature. In the latter case,
the hydrostatic test pressure shall be lowered to a value such that the stress
does not exceed 90 percent of MSYS. Also, if the design temperature is above
650 F, the minimum test pressure shall be as calcualted by Equation 20 of
Section 337. If hydrostatic testing is not considered practical, then pneu-
matic tests or other special alternate tests may be used as specified in
Sections 337.4.3 cr 337.5.
ANSI 831.4 requires that after construction, all liquid petroleum
transportation piping systems be tested, specifically that systems to be
operated at a hoop stress of more than 20 percent of MSYS shall be hydro-
s:atically tested to a pressure not less than 1.25 times the design pressure
Tor not less than 8 hours. Systems to be operated it less than 20 percent
cf MSYS may be tested pnpumatically at 100 psig, mainly to locate leaks.
See Section 437 of 831.4 for full details on testing.
6.3 Agitator Stuffing Poxes
Stuffing boxes or seals are used to avoid the flow of fluids
from a tank to the environment through the space between a rotating shaft
and its housing. In some cases, agitators may be used on tanks containing
hazardous wastes. If such wastes are volatile and either toxic or ignitable,
then some major operating troubles may occur involving leaks unless the
agitator stuffing box is well designed. Where agitators are used on tanks
containing volatile hazardous, materials, the permit writer should assure
himself that agitator stuffing boxes are not Vikely to become a source of
significant leaks and that proper design procedures have been used. Thus,
the oermit writer should request information from the applicant regarding
the engineering details used in the design of the stuffing box.
-------
6-11
Two types of stuffing boxes are in common use—mechanical seals
and stuffing boxes packed with materials frequently used for gaskets. Proper
selection of materials of construction is essential for both types of
stuffing boxes. Some discussion of materials of construction for seals is
presented in Appendix B, Section B.4.1, titled "Gaskets". (The full refer-
ence to a duscussion about seals in Mark's Standard Handbook for Mechanical
Engineers is also presented in Section B.4.1.)
-------
7-1
CHAPTER CONTENTS
7.0 TANK ANCILLARIES: FOUNDATIONS, SUPPORTS, INSULATION AND GROUNDING
7.1 Foundations
7.1.1 Sites Requiring Special Considerations
7.1.2 helhoas to Correst Subgrades
7.1.3 Nonearthen Foundations
7.1.4 Earthen Foundations
7.1.5 Tank Grades
7.2 Structural Tank Supports
7.3 Thermal Insulation
7.4 Electrical Grounding
-------
7-2
7.0 TANK ANCILLARIES: FOUNDATIONS, SUPPORTS,
INSULATION, AND_GROUNDING
Chapter 5.0 dealt with instrumentation amj control systems for
safe tank operation and Chapter 6.0 dealt with tank system hardware such
^:- pumps and piping. This Chapter 7.0 deals with other tan* anci'Maries
including foundations, supports, thermal insulation, and electrical
grounding.
Title 40 CFR 264.191(a) requires that "The Regional Adminis-
trate"- will review the design of the tanks, including the foundation, [and]
structural support, . .".
7.1 Foundations
Specific standards for the design of foundations are not avail-
able probably ber.ause of :he complexity of the subject and the numerous
solutions available to the engineer for solving varying site conditions.
Appendix C of API 620 and Appendix D of API 650 provide some general
auidance about foundations.
Because foundation standards are not available, the permit writer
must rely on information provided by the applicant to review the foundation
design. The most important aspect in such a review is that the design
must have been performed by qualified personnel such as a geologist and
a foundation engineer.
Specific ueil^n details made available to the permit writer
should include the following:
• Soil-bearing tests or other information defining conserva-
tive soil-bearing values.
t Computation of the design loading to be imposed by the tank
and Its contents when full.
• Design details where applicable of unsuitable soil to be
removed; fill sand, gravel, or crushed stone to be used
(sometimes to avoid corrosion to the bottom of the tank);
compact ion of the fill: elevan'o'i of the *cundaf!or sbove gra^e
i^e of a oarr; footing depth ana width; use of ACI ?tandar:j
313 for reinforced conor^t?; ring wall design: and the jrrount
of c-cwn to te uied under the tank.
-------
7-3
• In some cases for API 62C tanks, settlement measurements during
the hydrostatic test may be available.
The following information is primarily an abstract taken from API
Standard 650 for atmospheric-pressure storage tanks.
7.1.1 Sites Requiring Special Considerations
When facilities are constructed at the following types of sites,
special structural considerations are required.
• Hillside sites, where the depth of required fill is variable
• Sites on swampy or filled ground, where compressible
vegetation is near the surface, or where unstable or cor-
rosive materials may have been used
t Sites over layers of plastic clay, which may st-ttle excessively
• Sites adjacent to water courses or deep excavations, where
lateral stability of the ground is questionable
• Sites immediately adjacent to heavy structures, which dis-
tribute some of their load to the subsoil under the tank
site
• Sites whera tanks may be exposed to floodwaters.
7.1.2 Methods to Correct Subgrades
If the subgrade is weak or inadequate to carry the load cf a full
tank, construction under the tank bottom is necessary. One or more of the
following general methods may be used:
• Remove the objectionable material and replace with otner
suitable material
t Compact soft material with short piles or by preloading with
an overburden of eerth or other material and by assuring proper
drainage of the overburden
• Compact the soft material by draining off the water
• Stabilize the soft material by chemical methods or injection
of cement grout
9 Drive load-bearing piles or ccnstr-jct foundation piers to
s«rvf> as a reinforced s'*b on which to distribute t!ie load
of the tank.
-------
: 7-4
Fill material used to replace objectionable materials and to build
a suitable base (e.g , to build up the grade to a suitable height) should be
of high quality. It should be free of vegetation and organic matter and
should not contain substances, such as cinders, that could cause corrosion
of the tank bottom. The fill should be thoroughly compacted.
7.1.3 Nonearthen Foundations
When the properties of the underlying soil are corrosive to the
tank or inadequate to support the load of a full tank, a nonearthen foun-
dation is needed. Piles may be used under the foundation for support.
Piles can be made of steel, reinforced concrete, or concrete-filled steel
shells. Appropriate foundations are especially importan* when the facility
location is in an earthquake zone, a marshy area, or an otherwise unstable
area.
7.1.4 Earthen Foundations
If subsurface conditions indicate that it is unnecessary to
construct a substructure to support the tank, suitable foundations may be
constructed from earthen materials. The performance requirements for an
earthen foundation are identical to those associated with artificial
mater-ial foundations. Specifically, the foundation should:
• Provide a stable plane for the support of the tank
• Limit overall settlement of the tank grade to values
compatible with allowance provided in the design for
connecting piping and
• Provide adequate drainage.
7.1.5 Tank Grades
The tank should be constructed above the surface of the Surrounding
ground. This will provide for suitable drainage, help keep the bottom
of the tank dry, and even if some settlement occurs, elevate the tank abov»
the surrounding surface.
-------
7-5
It is suggested that the top 3 to 4 inches of the finished
grade consist of clean sand, gravel, crushed stone, or some similar inert
material that can be readily shaped to the proper contour. During con-
struction, the movement of equipment and materials across the grade will
mar the surface of the softer materials. These irregularities should be
corrected before the bottom plates are in place for welding.
To preserve the contour during construction and to protect the
tank bottom against ground moisture, the finished grade may be oiled or
stabilized in some other manner. Caution should be exercised jn assuring
that the quantity or kind of material used for this purpose does not create
welding difficulties or a risk of galvanic corrosion.
Normally, the finished tank foundation grade should be crowned
from the outer periphery to the center. A slope of 1 inch in 10 feet is
suggested as a minimum. Because the amount of crown will affect the lengths
of roof-support columns, it is essential that the tank manufacturer be
fully informed of the slope in advance. Some settlement of this crown
should be anticipated upon filling and operating the tank.
7.2 Structural Tank Supports
The design of structural supports for tanks is another area for
which there are no specific design standards. However, Appendix D of API
Standard 620 does provide some general guidance. Similar to the situation
for foundations, the permit writer must rely on information provided by
the applicant.
• The most important aspect of the permit review is that
the structural design must have been performed by
qualified personnel (or organization).
If the vendor of the tank was made aware of the amount and type of material
to be stored in the tank and was made responsible for the design and fabri-
cation of the structural supports, then the permit writer need not be
overly concerned, assuming that the tank vendor is generally recoanized as
beinn reputable.
In other cases, it is suggested that the permit writer review
Aopendix D of API Standard 620; the permit writer should also anticipate
-------
7-6
the need for some moderate engineering analysis during both the complete-
ness and technical review phases of the permitting process. Nevertheless,
the applicant must provide full disclosure of design computations and
drawings.
7.3 Thermal Insulation
There is no regulatory requirements in Title 40 CFR regarding
hazardous waste storage and treatment that the Regional Administrator
review the thermal insulation on tanks. Furthermore, thermal insulation
on tanks will seldom be required to make the process operable in such
facilities. Nevertheless, the permit writer may become concerned about
personnel protection against burns from tanks containing unusually hot
materials. There is no code specifying that tanks with a surface
temperature exceeding some specific value should be thermally insulated.
If the temperature is about 120 F (50 C), then the 'luman hand can be held
continuously against steel with some discomfort. However, some burning
is possible if the temperature exceeds aoout 175 F (80 C); therefore,
thermal insulation might be suggested if the contents of a tank are likely
to exceed this latter temperature and contact of personnel with the
tank is possible.
7.1 Electrical Grounding
When fluids are pumped at sufficiently high velocities through
piping or orifices, ;tatic electricity is likely to be formed. In the
presence of a flammable mixture, this static electricity may cause a
spark, and a subsequent explosion or fire. However, static electricity
may be dissipated by "aroundlno" it back to a steel tank containing the
liquid. The permit writer should become most concerned if a metal pipe
pumping flammable (ignitable) liquids discharges the fluid near the top
of the tank and if the pipe is not electrically "grounded" to the shell
of a steel tank. (The word grounded when used above may be viewed as
a misnomer because the grounding is not to the earth, but rather to the
shell of the tank.) In the situation above, the problem may be remedied
-------
7-7
by providing such grounding by a conductive (non-corrosive) metal. However
an alternative remedy must be used when the pipe or tank is non-metallic;
the most appropriate remedy may be to assure that the liquid enters near
the bottom of the tank. The National Fire Proteciton Association (NFPA)
Code 77, "Recommended Practices on Static Electricity", presents a full
discussion of the subject with further elaboration on the scope of concern
and on potential remedies.
-------
8-1
CHAPTER CONTENTS
8.0 INSPECTIONS
8.1 Evaluation of Inspection Plan
8.2 Weekly Abovegrouncl External Tank Inspection
8.3 Detailed Assessment of Tank Condition, (as scheduled)
8.3.1 External Inspection
8.3.2 Internal Inspection
8.4 Inspection of Auxiliary Equipment
8.4.1 Pipes, Valves, and Fittings
8.4.2 Pumps and Compressors
8.4.3 Instruments, Control Equipment, and Electrical
Systems
8.5 Inspection Tools and Procedures
3.5.1 Hammering Method
3.5.2 Penetrant-Dye Method
8.5.3 Magnetic-Particle Method
•1.5.4 Radiographic Method
8.5.5 Ultrasonic Method
8.5.6 Vacuum-Box Method
8.6 Frequency of Tank Inspection
8.6.1 Regulatory Requirements
8.6.2 Practical Considerations
8.6.2.1 More Frequent Detailed External Inspections
8.6.2.2 Immersed Test Coupons
8.6.2.3 Secondary Containment
-------
8-2
8.0 INSPECTIONS
A tank and its auxiliary equipment must be properly inspected
on a routine basis to ensure that the tank system is in good working order
primarily to prevent uncontrolled discharges of hazardous wastes to the
environment. Inspections may result in the conclusion that the tank should
be derated or no longer used for service if the tank is not economically
repairable. The regulations do not require secondary containment for tanks
and, therefore, any leak or other failure is an extremely hazardous situation
to be avoided. Regular inspections using effective procedures are the only
mechanism available to forecast the possibility of tank failure.
The permit writer is responsible for soecifyinq the minimum
allowable shell thickness and the frequency of inspections. According to
regulation 40 CFR 264.194(b), the applicant is required to develop a pro-
cedure to assess the condition of its tanks. The permit writer should be
concerned that the procedure proposed by the applicant will detect any
defect in the tank before the defect's depth can violate the minimum
shell thickness. The maintenance of a minimum shell thickness
for a tank may be viewed as beinq similar to the reouirement for
secondary containmert.
In general, this chapter 8.0 is written with metal tanks in mind.
Fiberglass-reinforced plastic tanks are somewhat different in that they often
fail by different mechanisms of deterioration than metal tanks. Section
4.2 " Fibernlass-Reinforced Plastic Tanks" presents further information
about plastic tanks, including a discussion about minimum shell thickness
equivalent (Section 4.2.3) and frequency of inspection (Section 4.2.4).
Stress corrosion around weld seams, corrosion at the liquid-vapor
interfac:, oxidative corrosion due to the presence of oxygen (from the air)
in the vapor space of vented atmospheric tanks, caustic embrittlement, and
hydrogen blistering are all types of corrosion which may occur in a non-
uniform way on the surface of the metal. However, careful vi:ual inspection
for these types of corrosion will usually be adequate to detect the possi-
bility of defects which would require more detailed examination. However,
pitting is another form of corrosion that in some cases may not be readily
-------
8-3
detected through visual inpsection. Furthermore, the nature of corrosion by
pitting is such that once the pit has been formed, the rate of corrosion may
be accelerated.
Pitting may occur where the liquid is locally stagnant, and
a concentration gradient rf electrolyte may develope that, in turn,
develops a small electrolytic cell, causing localized corrosion in
the form of a pit. Tank bottoms, weld seams and dead pockets are
the tank locations in which pitting often occurs. Liquid streams
containing chlorides are notorious for the possibility, of pit corrosion,
as are liquid streams containing sludges which may settle to the tank
bottom and, thus, form a dead pocket. Pitting has been observed directly
below openings on tanks storing crude petroleum due to rainwater settling
to the bottom and forming electrolytic solutions from the salts cont-
ained in the petroleum. In sorre cases, the pits formed in the metal may
not appear to be pits upon causual inspection because they have become
filled with corrosion products and sludge.
Thus, the permit writer should
t Require that the applicant provide information on the
expected corrosion rate of the liquid on the tank material
and the likelihood of pitting and other forms of non-uniform
corrosion.
« Insist that the applicant provide information supporting
the conclusion that inspections will oe performed by quali-
fied personnel using procedures that would detect both
uniform and non-uniform corrosion of all t>p-?s.
All permit writers unfamiliar with tank inspection procedures
should read the American Petroleum Institute Guide for Inspection of
Refinery Equipment, Chapter XIII,"Atmospheric and Low-Pressure Storage
Tanks". Particular attention should be given to sections 1302 through
1306.03.
A list of tools required for tank inspections is presented in
Section 1304 of the AP,I Inspection Guide as Tables 1 and 2. (Also see
section 8.5 of this manual.) Relatively detailed axpUnations on how many
of the common tools are used in inspection are presented in the text.
-------
8-4
i
It should be noted that in the API Guide relatively heavy
reliance is made initially on visual techniques of tank inspection to
detect evidence of non-uniform corrosion; however, upon detection of
potential defects, mora sophisticated methods are used to verify aH
determine the extent of the defect. For example, pits may be measured by
depth gage; thicknesses determined by calipers or, in some cases, drilling
a hole, which is then measured by hook gage and plugged; cracks measured
by penetrant dye or magnetic particle techniques and leaks verified by a
vacuum-box tester with soapy water. In some cases test specimens may be
removed from some portion of the tank (frequently the bottom )
for detailed examination. Some of the methods mentioned above are destruc-
tive in nature. Ultrasonic thickness detectors are common!" used to
measure for changes in thickness due to uniform corrosic at;o ;o detect
other flaws. Ultrasonic inspection has the advantage ttK: .: .asurements
mav be made from the exterior of the tank.
8.1 Evaluation of Inspection Plan
The inspection plan proposed in a permit application should
clearly describe all the procedures required to comply with the regula-
tions in 40 CFR 264.194. In brief outline format the required inspections
are:
(1) Overfilling control equipment, once per day
(2) Data on tank operating conditions, once per day
(3) Level in uncovered tanks, once per day
(4) Above-ground (external) portions of the tank to
detect corrosion and leaks, once per week
(5) Area around tank to detect signs of leaks, once
per week
(6) Detailed external and Internal assessment of tank
condition adequate to detect cracks, corrosion,
erosion, or wall thinning that may lead to leaks or
inadequate strength according to a predetermined schedule.
The dc'ily inspection of (1) overfilling control equipment is covered in
great?1' detail in Section 8.4.3.
-------
8-5-
The daily inspection of (2) data on tank operating conditions
such as pressures, temperatures, anc1 liquid levels that should be recorded
on operator's log sheets or on charts from recording instrurants, should
be part of the normal operating procedure. Operators and foremen, should
be trained about the range of values that are acceptable practice and to
notify supervision when such values have been violated. Further discussion
of this latter type of inspection is not presented here.
The daily inspection of the (3) level of wastes in uncovered
tanks to assure adequate freeboard to prevent overtopping due to winds
or precipitation is reasonably self-explanatory. Of course, specific
standards should be established to guide operators on the maximum levels
that can ba allowed without problems. It would be prudent for the appli-
cant to initially set very conservative maximum levels and then base any
changes on observations made on windy days. The minimum freeboard that
should be allowed is a function of many variables, including maximum
wind velocity, nearby topography and buildings, windscreens, wind
direction, tank diameter, liquid viscosity, and maximum 24-hour (or
longer) rainfall. This inspection is to be made visually and not by
reliance o^ instruments and ether indirect means of data acquisition.
Further discussion on this Inspection is not presented herein.
Trie weekly inspection of (5) the *r~z arouna tanks to detect
signs of leaks such >s we I spots, dried residues, dead vegetation, or
discolored spots does not require further explanation.
The remainder of this section presents information to guide
the permit writer on the inspection of
(1) Over-billing control equipment, daily
(4) Above-ground (external) tank Inspection for
leaks and corrosion, weekly
(5) Detailed external and internal assessment of tank
condition
-------
8-6
8.2 Weekly Above-Ground External Tank Inspection
Regulation 264.194(a) (4) requires inspection of "the construction
materials of the above-ground portions of the tanki at least weekly, to
detect corrosion or erosion and leaking of fixtures and seams". The
intent of this regulation should be viewed more as an attempt to detect
leaks or the potential for itnninent leaks, and less as a detailed assess-
ment of the condition of the tanks. Items to be assessed during this
inspection include:
• Erosion aro-:nd and cracks in the foundation and pads
* Corrosion, leaks, or distortion around nozzles and piping
connected to the tank
• Evidence of deterioration of protective coatings by the
appearance of corrosion, discoloration, blisters or other
film lifting.
• Evidence of corrosion of tank tops or roofs
• Proper functioning of roof seals (if any) and roof drains
(if any)
• Corrosion, discoloration, leaks, cracks, bulges, and
buckles of seams and plates of the tank wall and bottom
(if accessible).
If the external portions of the tank are covered with insulation, then
careful Inspection cf the insulation for leaks or evidence of leaks such
as discoloration would be the appropriate procedure.
Until potential defects are observed, this inspection is strictly
a visual inspection. However, upon detection of a defect, mone sophis-
ticated inspection procedures would be appropriate. Cf course, if a leak
is detected, further leakage should be stopped and the tank promptly
repaired or replaced.
8.3 Detailed Assessment of Tank Condition.
(as scheduled)
The detailed assessrrent of tank condition proceeds in two stages.
the external insoection and the internal inspection, as follow:
-------
8-7
External Inspection
Many elements of the external tank Inspection may be made while
the tank is in service; for example, ultrasonic examination of the average
inell thickness. (However, the measurement of average shell thickness
is listed as part of the internal inspection procedure in 'this document.)
A detailed description of the external tank Inspection procedure is pre-
sented as section 1304.02 of the API Guide of Inspection of Rjjfj_nery_
Equipment Chapter XIII, "Atmosoheric and Low-Pressure Storaae Tanks" and
is not repeitad herein. However, a checklist of the items to be investi-
gated and what to look for has been presented as Table 8-1 based on the
API Guide. Some external inspection procedures should not be performed
until the tank has been shut down and emptied.
8.3.2 Internal Inspection
The internal inspection described by the applicant should take
place in at least two major phases — emptying the tanic ana trie inspection.
According to 40 CFR 2G4.184(b), the applicant must establish procedures
for emptying the tank to allow entry and inspection of the interior.
Although the intent of this regulation is not made explicit, the permit
writer should be concerned with safety of personnel, avoidance of spills
to the environment, and other hazardous conditions. A checklist of items
w-'th which to be concerned is presented in Table 8.2. The checklist
includes consideration of lined and fiberglass-reinforced plastic (FRP)
tanks. (Further information about FRP tanks is presented in Section 4.2.3.)
8.4 Inspection of Auxiliary Equipment
C->"»"on auxiliary equipment and system components attached
to tanks used for hazardous waste include pipes, valves, and fittings;
pumos and compressors; and instruments, control equipment, and electrical
systems. Inspection of these are discussed in the following sections.
-------
8-8
TA3LE 8-1. CHECKLIST OF TANK EXTERNAL-INSPECTION POINTS
A. Tank In Service
(1) Ladders, Stairways, Platforms and Walkways
- worn or broken parts and treads
- corroding parts
- cracked or spalled concrete pedestals
- low spots where water can collect
- loose rivets and bolts
(2) Foundations
- erosion
- uneven settlement
- cracks and spall ing in concrete pads, basa
rinos,and piers
- deterioration of water seal between tank
bottom and the foundation
- distortion of anchor bolts
(3) Pipe Connections
- external corrosion
- cracks and distortion
(4) Electrical Grounds
- corrosion where enters ground
- resistance
(5) Protective Coatings
- rust spots, blisters, and film liftino
(6) Tank Walls
- corrosion (underground and under insulation in oarticular)
- discoloration of paint surface
- cracks at nozzle connections, In welded seams,
and at the metal ligament between rivets
- cracks, buckles, and bulqes
- tightness of bolts or rivets, if applicable
(7) Tank Roofs
- malfunctioning of seals
- olockage or breakage of water drains on roofs
- corrosion
-------
8-9
TABLE 3.1. (Continued)
(8) Overfilling Control
- malfunction of controls
- insufficient freeboard
-k Out of Service
(1) Tank Bottoms (only if appropriate)
- tunneling ..ethod
(2) Pipe Connections
- hanmering
- at point of entrance at soil line
(3) Tank roofs, pontoons, double decks, seals, and purlins
- harrmering
- visual
- leaks
(4) Valves and Valve Seats
- visual
(5) Auxiliaries
- vents fo~ plugging, breather vtlves for seating
- liquid-level controls for cracks and corrosion
- pressure gaqes for plugging and accuracy.
-------
8-10
TABLE 8-2. CHECKLIST FOR TANK INTERNAL INSPECTION
(TANK OUT OF SERVICE)
A. Tank Emptying and Preparation For Inspection
- avoidance of spills
- avoidance of hazardous conditions (reaction, ignition,
or toxic exposure)
- use of appropriate materials of construction for any
temporary storage containers (or tanks) and connecting
systems
- cleaning and ventilation procedure
- complete disconnection or blanking off of all connecting
piping
- air quality check
- adequate lighting
- personal safety equipment as appropriate (clothing and
respiratory)
- Standby equipment and services readily available
B. Interior Inspection of Solid Steel Tanks
(1) Roof and Structural Supports (visual first for safety)
- no hazard of falling objects
- corrosion
(2) Koof and Structural Supports (more rigorous)
- loss of metal thickness
- crr.cks, leaks at welds
- cracks at nozzle connections
- malfunction of floating roof seals
- water drain system deterioration
- hammering
(3) Tank Shell
- cracks at seams
- corrosion of vapor space and liquid-level line
- cracking of plate joints
- cracking of nozzle connection joints
- loss of metal thickness
-------
8-11
TABLE 8-2, (CONTINUED)
(4) Tank Bottom
- hammer testing
- corrosion pits
- sprung or cracked seams
- rivets for tightness and corrosion
- depressions in the bottom areas arcurd or under
roof supports and pipe supports
- bottom thickness
- unevenness of the bottom
- sample coupons, if appropriate
C. Interior Inspection of Lined Steel Tanks
NOTE: Some of the procedures and locations to inspect noted
in section B for solid steel tanks above are equally
applicable to lined tanks. Tanks may be lined with alloy
steel, lead, rubber, glass, coatings, and concrete.
- general condition of lining (holes, cracks, gaps, corrosion,
erosion, swelling, hardness, loss of thickness)
- oroper •oositioning cf liner
- bulges, bli^-ering t or spalling
- spark testing with rubber, nlass, and orqanic type
coatings
- ultrasonic examination of steel outer shell thickness
is possible if any deterioration is suspected.
D. Interior Inspection of Fiberglass Reinforced Plastic Tanks
- hardness test of any test specimens exoosed to liquid
in the tank
- indentations,cracks, exposed fibers, crazing, checking,
lack of surface resin, and delamination
- if sufficiently translucent, porosity, air or other
bubbles, other inclusions, and thin areas
- ultrasonic examination cf laminate thickness is possible
if any deterioration is suspected in the polyester matrix.
-------
.8-12
8.4.1 Pipes. Valves, and Fittings
Inspections of pipes, valves, and fittings are usually con-
ducted to note any leaks, cracks, corrosion, or bosses in metal thickness
owing to external or internal deterioration. The internals of these
equipment parts are subject to erosion or wear because of the effects of
high liquid turbulence or velocity. Areas around pipe bends, elbows, tees,
and other restrictions, such as orifice plates and throttling valves,
are particularly subject to erosion.
Visual inspection techniques include checking for leaks, mis-
alignment, unsound piping supports, vibration or swaying, external cor-
rosion, accumulations of corrosive liquids, and indications of pipe
fouling. Thickness measurements while the pipes are in operation can be
taken utilizing ultrasonic or radiographic techniques.
If the tank is out of service or if a line can be valved off,
with proper safety precautions piping can be opened at various places
by removing a valve or fitting or by springing the pipe apart at flanged
locations to permit internal visual inspection. A flashlight or exten-
sion light is needed in most cases and a probe-type .instrument, such as
a borescope, or a mirror and light will permit a more detailed view. If
corrosion or erosion conditions are noted visually for some parts,
radiographic or ultrasonic techniques can be used to inspect the entire
length of pipe, if inaccessible to visual examination. Replacement may
be more economical than such techniques in some cases if the entire
piping run is suspect. Gaskets should often be replaced if the line is
broken at flanges.
A brief checklist for inspection of piping, valves, and fittings
is presented as Table 8-3.
-------
8-13
TABLE S-3. CHECKLIST FOR INSPECTION OF PIPING,
VAtVES, AND FITTINGS
Leaks
Cracks or corrosion
Metal thickness (by hammering or caliper)
Metal thickness (by ultrasonics, radiation, or eddy
current
Gasket condition
Alignment, distortion, and swaying
Valve seats
Pipe rack supports or hangers
Vibration
Erosion
Piping systems that cannot be inspected visually are frequently
pressure tested, They include:
t Underground and other inaccessible piping
• Complicated manifold systems
9 Small pipe and tubing systems
• All systems after a chemical cleaning operation.
The most used media for pressure tests is water. In this type
of test the water is pumped into the pipe such that the quantity of gas
in the pipe is minimal. When the pressure has reached the test pressure,
the system is valved off but with a pressure gage on the closed system.
Small leaks of the incompressible water results in a rapid and significant
drop in pressure and, thus, the probability of a leak is established. Use
of compressible or condensible gases such as steam, air, carbon dioxide,
and so forth is generally less reliable; more reliance must be placed on
hearing the sound of escaping gas or otherwise detecting leaks.
-------
8-14
8.A.2 Pumps and Compressors
Mechanical wear is the predominant cause of deterioration of
pumping and compression equipment, although erosion and corrosion are
also responsible for an appreciable amount of deterioration. Other
deteriorating factors include improper operating conditions, piping
stresses, cavitation, and foundation deterioration causing misalignment
or vibrations.
Since vibration can rapidly deteriorate a pump or compressor,
periodic examination of the vibration level should be made using an
electronic vibration meter. Inspection of all assembly bolts, gaskets,
cover plates, and flanges should be conducted to detect leaks and cracks
as a result of vibration or abnormal operating conditions.
A brief checklist for the visual inspection of pumps and
compressors is presented as Table 8-4.
TABLE 8-4. CHECKLIST FOR VISUAL INSPECTION
OF PUMPS AND COMPRESSORS
- Misalignment
- Foundation cracks and uneven settling
- Kissing or broken anchor bolts
- Leaky piping connections
- Excessive vibrations and noise
- Deteriorating 4nsulation
- Depleted lubrication oil reservoir
- Missing safety equioment such as a pump coupling guard
- Burning odor or smoke
- Excessive dirt
- Excessive corrosion
- Leaks and cracks at assembly bolts, gaskets coverplates,
and flanges
Two pumps are often installed in parallel such that one pump
may be shut down while the other does all the reouired pumping. Thus,
one pump nay undergo a complete internal inspection cr replacement
.vh.-Me t^e system regains in operation.
-------
8-15
8.4.3 Instruments, Control Equipment, and
Electrical Systems
Instruments, control equipment) and electrical systems must be
inspected at the minimum required frequencies given in 40 CFR 265.194
and section 8.5 of this manual to ensure that they are in gooa working
order. Level controls, emergency shut-off devices, and alarms are among
the most important devices for fail-proof tank operation. Flow rate
controls, temperature gauges, pressure gauges, and analyzers ari' among
the less important devices.
A brief checklist of what should be inspected regarding the
instruments, control equipment, and electrical systems is presented in
Table 8-5.
TABLE 8-5. CHECKLIST FOR INSPECTION OF INSTRUMENTS
AND CONTROL SYSTEMS
- Instruments
- Transmission systems
- Power supplies
- Seals
- Panels and enclosures
- Electrical Equipment
- Insulation
- Operating mechanisms (moving parts)
- Insulating and lubricating oils
- Protective relays
- Bearings
- Batteries
- Connectors
- Rectifiers
The visual inspection should specifically watch out for any
deteriorating effects of the following on electrical systems:
- Heat
- Dirt O
- Moisture
- Chemical attack.
-------
8-16
The instruments and controls must be calibrated by qualified
personnel as per the: methodology and frequency recommended by the
vendors.
Inspection of the data gathered by instruments should be included
as an integral pert of the overall inspection plan for instruments, control
equipment, and electrical systems. Any unexpected discontinuities or
abnormal peaks in data charts or data logs may indicate that there is some
cause for concern in the control systems.
8.5 Inspection Tools and Procedures
When visual inspection suggests that tools are needed for a more
detailed inspection, simple hand tools may be used as an initial aid.
Tools such as a scraper, digger, flange spreader, knives, paint or crayon,
portable lights, and rules are indispensable for visual inspection-.
Additional tools such as hammers, mirrors, magnifiers, magnets, and
internal visual scopes are also helpful.
The mechanical measuring tools Include calipers, micrometers,
scales and tapes, wire gauges, level and plumb bob and line, depth
gage, hook gage, square, and straightedge.
Approved destructive examination methods include drilling a
nole through the tank wall or bottom, then using a hook gage to measure
thickness, tapping the hole, and inserting a threaded plug. Another
method is to cut large (12 inch by 12 inch) test specimens from the
tank for detailed examinations; this is often performed for tanks where
the bottom cannot be externally Inspected.- A trepanning saw i.iay be
used to renc/3 a portion of a weld from the tank for examination.
Brief descriptions of other inspection tools and methods follow:
8.5.1 Hammering Method
Full blows of the hammer are used and the sound, feel, and
imprint of t.'ie hammer head noted. Where corrosion or erosion is signifi-
cant, the sound will be dull, the feel soft, and a dent or hole likely.
Hammering is frequently performed on tank roofs, bottoms, and on floating
roof components.
-------
8-17
8.5.2 Fenetrant-Dye Method
Penetrant dyes are often used to define surface cracks on a tank
that would not be verified by a visual inspection.' The penetrant is aoplied
by either brushing or spraying to a surface carefully cleaned (often by
sandblasting), dried, and then the excess is removed. After a few minutes
of contact to allow penetration into the crack, a chemical developer is
then applied to the surface. The dye stains the developer and exposes the
extent and size (but not the depth) of any defects.
8.5.3 Magnetic-Particle Method
The magnetic-particle method is also used to define surface
cracks on tanks similar to the penetrar.t-dye method. The surface must
also be carefully cleaned and then iron particles are sprinkled on the
surface. A magnetic field is then imposed near the particles either by
a permanent magnet (especially if flammable materials are stored nearby)
or an electromagnetic device and the particles arrange themselves along
the crack and particularly near the ends of the crack. The magnetic
field should b» imposed in two directions to assure there is no crack
or to identify two or more cracks running in different directions. No
indication is given about the depth of the crack. This method may be
used only on tanks constructed of magnetic materials.
8.5.4 Radiographic Method
Welds are often radiographed during tank fabrication to detect
thickness and flaws of the welds. This method may also be used to deter-
mine thickness of tank plates. The device may use either X-rays or gamma
radiation and must be calibrated prior to use. It is similar in many
respects to the X-ray machines used for dental and medical purposes.
-------
8-18
8.5.5 Ultrasonic Method
Ultrasonic instruments can be used to measure the tank's thick-
r.ess and determine the location, size, and nature if defects. They can
be used while the tank is in operation as only the outside of the tank
needs to be contacted with the device. Two types of ultrasonic instruments,
the resonance and the pulse type, are most commonly used for tanks. The
pulse type utilizes electric pulses and transforms them into pulses of
ultrasonic waves. The waves travel through the metal until they reach a
reflecting surface. The waves then are reflected back, converted to
electrical pulses, and show up on a time-base line of an oscilloscope.
The instrument is calibrated by using a material of known thickness. There-
fore, the time interval between the pulses corresponds to a certain
thickness.
8.5.6 Vacuum-Box. Method
The vacuum box is an open box in which the lips of the open
side are covertd with a sponge rubber gasket, and the opposite side
is glass. A vacuum gauge and air siphon connection are installed on
the box. The seam of the tank shell where a leak is suspected is first
wetted with a soap solution, then the vacuum box is pressed tightly
over the seam. The foam-rubber gasket forms a seal, and a vacuum is
achieved inside the box by the air siphon. If a leak exists, bubbles
will form insida the box and can be seen through the gl?.ss.
8.6 Frequency of Tank Inspection
There are several regulatory requirements regarding tank inspec-
tions and. in the case of 'the detailed assessment of tank condition,
other practical considerations.
3.6.1 Regulatory Requirements
The frequency of performing some types of tank inspections ;3
presented in 40 CFR 261.19 and is summarized in Table 8-6.
-------
> 19
TABLE 8-6. MANDATED INSPECTION FREQUENCIES
At Least Once Per Normal Operating Day
- Overfilling control equipment
- Data on tank operating conditions
- Level in uncovered tanks
At Least Once Per Week
- Abovs-ground external portions of tank
- Area surrounding tank
Although the permit applicant is required to present a schedule
for the detailed assessment of tank condition, the permit writer is
ultimately responsible for specifying the appropriate schedule in the
permit issued to the applicant.
Title 40 CFR 264.15(b) states that the frequency of inspection
for other items should be based on the rate of possible deterioration of
the equipment and the probability of an environmental or human health
incident if the deterioration or malfunction goes undetected. Part 264.i91(b;
requirements for periodic comprehensive tank inspections specify the
following additional factors to be us«d in determining inspection intervals:
• Material of construction of tank
• Type of erosion or corrosion protection used
* Characteristics of waste being stored
9 Rate of corrosion or erosion observed during previous
inspections.
8.6.2 Practical Considerations
The detailed tank assessment is often a costly requirement
for the operator of a hazardous waste storage facility because the tank
must be shut down, blocked off, emptied, cleaned, and undergo detailed
examination by qualified personnel. Unless the operator has spare tanks,
shutdown of the tank may temporarily also necessitate closure of the
-------
8-20
facility. Adequate tank cleaning f*- personnel safety may also be a
costly step in terms of both elapsed time and other dollar costs. Further-
more, there is always some potential for residual hazardous materials to
remain in nozzles or piping associated with the tank. Thus, tank inspec-
tions must be frequent enough to avoid leaks and spills but should not
become necessarily burdensome to the operator of the facility.
In ca^es where the corrosion rate data are known at storage
temperature for the specific material of construction of the tank witn the
specific liquid to be stored in the tank and only uniform corrosion has
been experienced in prior applications, the expected service life of the
tank can be realistically estimated, which can then be used to establish
a reasonable inspection schedule. During the initial years, scheduled
inspections at 20, 40, and 60 percent of the tank's service life would
be reasonable frequency. For example, a tank with an expected service
life of 25 years might initially be subjected to a comprehensive inspection
every 5 years to establish the actual rate of corrosion or deterioration.
However, after shell thickness measurements were made and the existence
of any non-uniform corrosion noted, the estimated service life coula be
re-estimated and the inspection frequency increased if necessary as the
tank approaches the end of its service life and the probability of leaks
or ruptures increases; for example, the inspection frequency could be
increased to every 1 to 2 years.
If non-uniform corrosion has been experienced by a material
of construction with the liquid to be contained, much more frequent
initial insoections :,hould be scheduled. Pitting and crevice corrosion
are particularly obnoxious because not only dees there often seem to be
an induction period with little observable physical damage, but also the
corrosion accelerates onca the pit or crevice is formed due to formation
of a larger electrolytic cell. Materials subject to pitting or crevice
corrosion should normally not be selected unless an economic analysis
clearly indicates a preference toward frequent inspections rather than
to a more costly material of construction.
-------
8-21
8.6.2.1 More Frequent r°t;.i'!ttd External Inspections. In some
cases where any form of non-uniform crr -osion is not expected, the owner
or operator may prefer to conduct more frequent comprehensive external
inspections of tne tank to avoid the expense of frequent internal inspec-
tions, providing all portions of the tan!-: are accessible, including the
bottom. In the example cited above, fie owner-operator could initially
conduct annual external inspections, which include intensive measurements
of tank shell thickness (i.e, one measurement per square yard of surface
area) and reduce the frequency of internal inspections to once every 7
years. As the condition of the tank deteriorates, however, the frequency
of internal inspections should increase to every 1 or 2 years.
8.6.2.2 Immersed Test Coupons. In cases where few corrosion
data are available or proper tank inspection would be very costly, test
specimens (coupons) of material literally from the same heat (or batch) of
the metal used to construct the tank may be immersed in the liquid, with
some coupons allowed to rest on the bottom of the tank. These test coupons
ray be stressed by bending and welding to form crevices to simulate
problem areas in the tank. Samples can be withdrawn annually and measure-
ments made of thickness and observations made about stress, crevice, and
pitting corrosion. The data collected could than be used to suggest an
appropriate inspection schedule; of course, an inspection schedule should
be established that requires greater frequency than that projected by
the data from the coupons.
In the case where a used tank has been installed and no coupons
may be taken from the specific heat (or batch) of material from which
th
-------
8-22
8.6.2.3 Secondary Containment. If the tank operates at close
to atmospheric pressure and a leak would not cause undue detriment to
personnel, property, or the environment if the leak were collected in a
secondary containment system, then some reduction could be considered in
the frequency of the internal tank inspection. Obviously, if the malarial
stored were volatile and toxic upon inhalation or if the waste were highly
reactive with water (rain) or with the material of construction used for the
containment system, then this approach would not be suitable.
Other considerations include the size of the tank or quantity
of material which might be leaked to the secondary containment system.
Upon detection of a leak it may be possible to rapidly pump the tank's
contents to an alternative tank as a temporary measure and thus avoid
too large a spill. Of course, good housekeeping combined with frequent
inspections would be required to assure that any leaks wer? detected :oon
ufter failure. The difficulty in cleaning up a spill should •jlso be con-
sidered. Because of the difficulty in inspecting insulated tanks for leaks,
reliance on secondary containment and early leak detection in this situation
would not be practical.
Another problem emerges with tanks where the bottom .rests directly
on a foundation such that the bottom cannot be externally inspected. Ob-
viously, the foundation must be within Me secondary containment system.
Furthermore, if pitting or other forms of non-uniform corrosion are experi-
enced in the bottom, a leak may be present for a significant period of
time before it becomes detected. During this period of time, considerable
further deterioration of the tank may continue leading to a major failure.
Particular attention should be given to avoiding ignition of
hazardous wastes if they are combustible . Use of expolosision-proof motors and
prohibit of nearby motor vehichles and the like near the secondary
containment syste'ft. Also, there should be no possibility of mixing incom-
patible wastes in the same secondary containment area if simultaneous leaks
were to occjr.
-------
9-1
CH APTE R_CONTENTS_
Q.3 S°ILLS, LEAKS, AND SECONDARY CONTAINMENT
Response to Spills and Leaks
Secondary Containment
Runoff and Leachate Collection System
Peripheral Dike Systems
Liner Systems
References
-------
9-2
9.0 SPILLS. LEAKS. AND SECONDARY CONTAINMENT
Chapter 9.0 is reserved for a possible future expanded discussion
of the causes of spills and leaks and a minimal description of secondary
containment. Some interim guidance on these matters is provided in the
following pages which have been copied directly from a simila-r manual
prepared by Fred C. Hart Associates, Inc. Other guidance should be obtained
for the preparation of contingency plans including response to spills and
leaks and in reviewing secondary containment systems.
Secondary containment systems are not generally required for
tanks containing hazardous wastes. Nevertheless, as discussed in section
8.6.2.3 of this manual, under selected conditions the required frequency of
tank inspection may be reduced if the tank has an effective secondary
containment system.
Response to Spills and Leaks
Section 264.194(c) of the standards for inspection of hazardous
waste tanss orovides that owners or operators must specify the procedures
they intend to use to respond to tank spills or leakage, including pro-
cedures and timing for expeditious removal of leaked or spilled waste and
repair of the tank.
The procedures specified by the owner-operator will depend
largely on site-specific circumstances. Factors will include the permeability
of tr.e area surrounding the tank, availablility of excess capacity for
emptying the tank, anci the materials of construction of the tank.
Table 9-1 summarizes the types of incidents -1ikely to occur
at a tank facility that should be addressed in the contingency plan.
Secondary Containment
Currently, EPA's hazardous waste regulations do not reouira
a secondary containment svstem for tanks that treat or store hazardous
waste. Th2s^ systems a'-e, however, effective means for detect"iq
-------
9-3
TABLE 9-1. OPERATIONAL PROBLEMS OF TANKS*
Bulk Storage Facilities - Tank Farms and Tankage
« Overfilling of tanks
§ Rupture of tanks
« Leaks in tanks, pipes, valves, and fittings
• Leaks in containment dikes
t Inadequate dike volume to hold contents of leaking tanks
• Water flow from diked area through open dike valve
« Leaks from pump seals and maintenance
• Level instrument failure allowing tank overfilling
» Piping damage by collision with mobile equipment
e Spills from tank bottom cleanout and sludge disposal
• Spills from pipe and tankage changes
* Oil spill prevention control and countermeasure plan
review. A training program planned and presented by Rice
University, University of Texas and Houston, and the U.S.
F.?A. The Pace Company, 1975.
-------
9-4
and containing leaks and spills and are included in the design of many
facilities. Some types of secondary containment are:
• runoff and leachate collection systems
• peripheral diking systems
• liner systems.
Runoff and Leachate Collection Systems
These systems should be constructed of materials compatible with
the waste and should be designed to include:
• a slope of greater than one percent away from the tank
or the collection point
t a collection point where runoff or precipitation can be
routed so that it can be removed
« capacity equal to the volume of the largest tank or
10 percent of the volume of dll the tanks in the con-
tainment system and allowance for precipitation
» sufficient freeboard for sumps (if applicable).
Peripheral Dike Systems
Peripheral drainage collection can serve two purposes: it
can prevent precipitation from entering the contained system, and it can
contain leaks, runoff, and precipitation within the system. An acceptable
design for a tank diking system should include the following:
• a capacity equal to the volume of the largest tank or
10 percent of the volume of all tanks (whichever is
greater) in the containment system
• walls that are designed to be liquid tight and to withsf.ano
a full hydrostatic head. The slope cf earthen walls should
be consistent with the soil's angle of repose
• piping (which passes through dike walls) that is liquid
tight and designed to prevent excessive stresses as a
••asult of settlement
-------
9-5
• relatively impermeable ground within the dike area to
preclude ground-water or surface-water contamination
• a drain (such as drain pipes or grates) with control
valves for the systematic collection and drainage of
runoff, leakage, and precipitation from the diked area
Alternatively, a sump system that can be drained utilizing
a portable pump may be installed
t diked area should be kept free of drums, debris, etc.
For structural stability purposes, earthfill dikes should have
side slopes of horizontal to vertical no greater than two to one.
Additionally, a cutoff joining the base of the dike with the underlying
soil is recommended to "key" the dike-into the indigenous soil.
Liner Systems
A liner is a continuous layer of natural or man-made materials,
beneath or on the sides of c containment system, that restricts the down-
ward or lateral escape of hazardous waste, Hazardous waste constituents,
or leachate. The purpose of a liner for a tank storage facility is to prevent
hazardous waste from coming in contact with the soil or surface or ground
water. Liners may or may not be used at a facility. . If liners are used,
they may be found under or on top of the containment area or in other unique
applications. A variety of natural and synthetic materials are available
for use as liners. Their selection is generally based on the following
factors:
• degree of impermeability (and thickness) required
• hydraulic head of waste
• availability of the material
• costs.
See EPA's technical resource document titled Lining Qf Waste,
Impoundment and Disposal Facilities^ for further information on liners.
-------
9-6
REFERENCES
1. "Flammable and Combustible Liquids", National Fire Protection Association
NFPA 30, 1981. Quincy, Massachusetts, 1980.
2. Oil spill prevention control and countermeasure plan review. A training
program planned and presented by Rice University, the Universities
of Texas and Houston, and the U.S. Environmental Protection Agency.
The Pace Company. 1975.
3. Lining of Waste Impoundment and Disposal Facilities. Office of Water
and Waste Management, U.S. EPA SW-870, September, 1980.
-------
10-1
REACTIONS IN TANKS
10.1 Chemical Oxidation
10.1.1 Oxidation Processes
10.1.2 Types of Wastes Treated by fhemical Oxidation
10.1.3 Process Design and Operating Parameters
(a) Type of Tank
(b) Selecting Materials for the Oxidation Process
10.2 Chemical Reduction
10.2.1 Reduction Processes
10.2.2 Types of Waste Treated by Chemical Reduction
10.2.3 Process Design and Operating Parameters
10.3 Neutralization
10.3.1 Process Description
10.3.2 Application of Neutralization Process
10.3.3 Types of Tanks
10.3.4 Environira ital Impacts
10.4 Precipitation, Flocajlation, and Sedimentation
10.4.1 Precipitation
(a) Process Description
(b) Process Design and Operating Parameters
10.4.2 Flocculation
(a) Process Description
10.4.3 Sedimentation
(a) Process Description
(b) Process Design and Operating Parameters
10.4.4 Precipitation, Flocculation, and Sedimentation Applications
to Hazardous Wastes
(a) Iron and Steel Industry
(b) Aluminum Industry
(c) Copper Industry
(d) Metal Finishing Industry
(e) Inorganic Chemicals Industry
(f) Sludge Thickening
10.4.5 Environmental Considerations
-------
10-2
10.0 REACTIONS IN TANKS"
The service life of a tank can be prematurely shortened because of inter-
actions among the wastes with other wastes, with the tank's construction materials,
and with tie treatment proems or treatment reagent. To avoid adverse effects,
the regulation (40 CFR 264.13) requires that a waste analysis be performed before
treating, storing, or disposing of hazardous waste. In addition to this general
requirement, the operating requirements for tanks [40 CFR §264.i92(a)] nate
that "wastes and other materials (e.g., treatment reagents) which are incom-
patible with the material of construction of the tank must not be placed in the
tank unless the tank is protected from accelerated corrosion, erosion, or
abrasion through the use of: (1) An inner liner or coating which is compatible
with the waste or material...; or (2) Alternative means of protection."
The following are common operating problems associated with ;n-tank
processes discussed in this chapter.
1. Corrosion. Corrosion of a tank may be accelerated by the treatment
process itself or by the chemical reagents used to treat the waste. For example,
chromic acid (an oxidizing agent) generally corrodes all metals. It would
therefore be inappropriate to treat chromic ac'd by neutralization or precipitation
in a steel tank unless the tank is lined with a material that is relatively inert
to chromic acid (e.g., glass, polyethylene, or PVC).
2. Salting and seal ing. Salting and scaling is the fcmation of 3" insu-
lating layer at heat transfer surfaces that cculd contribute to the failure of
tanks and the subsequent escape of hazardous waste to the environment. Salting
and scaling may be reduced or prevented by preliminary treatment of the influent
waste stream or by other operational controls.
3. Pressure and heat. High pressure or heat caused by mixing wastes that
collectively generate large amounts of gaseous emissions or result in an exo-
thermic reaction may cause tanks to explode, warp, or weaken unless the tank
has been designed to withstand high pressure or temperature. Toxic or flammable
gases may also be emitted as a result of process reactions.
4. Liquid flow rate and mechanical abrasion Mechanical abrasion from
materials contained in the waite, high liquid flow rates, or high velocity mixing,
may damage the construction materials of tanks, pumps, or ancillary equipment.
Points of contact experiencing the most wear are, for example, nozzle necks,
pump cases, valve seats, and pipe fittings. In order to prevent erosion, it is
important to match the construction material of the tank and ancillary equipment
with the abrasion characteristics of the wastes expected to be treated, the
anticipated liquid flow rate of the treatment process, and the energy generated
or dissipated by mixing devices.
* Source:"Draft Permit Guidance Manual - Tanks", July, 1981, by T. P. Seng^r
and Fred C. Hart Associates, Inc., for the ;-nvi rcnmental Protection Agency.
Wai,hinyton, D.C.
-------
10-3
In order to determine whether a treatment process and its associated
reagents are suitable for the treatment of a particular waste within a parti-
cular type of tanks, one must consider several factors. A treatment trial
test can be conducted to examine the possibility of heat evolution or gas
evolution, the compatibility of the treatment process -intermediates and end
products, and the compatibility of any added reagents with the tank's construc-
tion materials and design features.
This chapter is meant to provide an overview of the treatment processes
that commonly occur in tanks and the possible interactions of the treatment
processes with a tank. The five treatment processes described herein and
the potential areas of process-tank interaction are as follows:
(1) chemical oxidation - corrosion, abrasion owing to mixing, high heat;
(2) chemical reduction - corrosion, abrasion owing to mixing, high heat;
(3) neutralization - corrosion, high heat or pressure, abrasion owing
to mixing;
(4) precipitation - corrosion, abrasion due to mixing, scaling;
(5) sedimentation - corrosion, salting, scaling.
10.1 CHEMICAL OXIDATION
i'°N
10.1.1 Oxidation Processesvfc!
The processes discussed here are based on chemical oxidation as differen-
tiated from thermal, electrolytic, and biological oxidation. Chemical oxidation
is a process in which the oxidation state of a substance is increased (i.e.,
the substance loses electrons). Chemical oxidation in water and wastewater
treatment is a method for detoxifying objectionable and/or toxic substances.
These substances include:
2+ "+ 2- - 2
• inorganic substances (e.g., Mn , Fec , S , CN , SO, );
• organic substances (e.g., phenols, amines, humic acids, odor- or
color-producing or toxic compounds, bacteria, and algae).
Chemical oxidation processes most often used include:
oxygenation or aeration;
ozonation
oxidation with hydrogen peroxide (very limited use);
oxidation with potassium permanganate;
chlorination or nypochlorination;
oxidation with chlorine dioxide;
oxidation v/ith chromates or dichromates.
Table 10-1 is ^ listing of oxidants used to treat various wastes.
-------
10-4
TABLE 10-1. OXIDATION WASTE TREATMENT APPLICATIONS^
Oxidant
Waste
Ozone
Air (atmospheric oxygen)
Chlorine gas
Chlorine gas and caustic
Chlorine dioxide
Sodium hypochlorite
Calcium hypochlorite
Potassium permanganate
Permanganate
Hydrogen peroxide
Nitric acid
Phenols
Chlorinated hydrocarbons
Sulfites
Sulfides
Ferrous iron
Sulfide
Mercaptans
Cyanide
Cyanide
Diquat
Paraquat
Cyanide
Lead
Cyanide
Cyanide - organic odors
Lead
Phenol
Diquat
Organic sulfur compounds
Rotenone
Forma'idphyde
Manganese
Phanol
Cyanide
fulfur compounds
_ead
Benzidene
-------
10-5
10.1.2 Types of Wasfre Treated by
Chemical Oxidafion(3r
Liquids are the primary waste form treatable by chemical oxidation. The most
powerful oxidants are relatively nonselective; any easily oxidizable material
in the waste stream will, therefore, be treated. For example, if an easily
oxidizable organic solvent was used, little of the chemical effect of the
oxidizing agent would be available for further oxidation.
Gases have been treated by scrubbing with oxidizing solutions for the
destruction of odorous substances, such as certain amines and sulfur compounds.
Potassium permanganate, for instance, has been used in certain chemical processes,
in the manufacture of kraft paper, and in the rendering industry. Oxidizing
solutions are also used for small-scale disposal of certain reactive gases in
laboratories.
Oxidation has limited application to slurries, tars, and sludges. Because
other components of the sludge, as well as the material to be oxidized, may be
attacked indiscriminately by oxidizing agents, careful control of pH, etc.,
are required to ensure that the desired components are being oxidized.
Chemical oxidation can be used to treat both organic and inorganic waste
components. Since some oxidizing agents may react violently in the presence of
significant quantities of readily oxidizable organic material, either the
ornanic matter or the oxidizing agsr.t should be added slowly. Sudden large
additions should be avoided.
The primary use of chemical oxidation for hazardous waste treatment is
in the conversion and destruction of cyanides from plating operations where
metals, such as zinc, copper, and chromium, are present.
10.1.3 Process Design and Operating Parameters
As a physicochemical process, the design of a system for the chemical
oxidation of a s'a^ta material involves considering the following design and
operating parameters:
type of tank (or reactor);
mixing;
location of inlet and outlet pipes;
pH or other process control;
temperature control ;
materials selection.
Both tank selection and materials selection are discussed below.
-------
10-6
(a) Type of Tank. Types of vessels, containers, or tanks (commonly
called reactors) in which chemical and biological reactions are carried out
include batch, plug flow, continuous, packed, or fluidized bed.
\
(b) Selecting Materials for the Oxidation Process. When selecting the
materials of construction for the oxidation process, one must protect the tank
against the corrosive effects of the oxidizing agent. Specifying a material of
construction usually involves three stages: listing the requirements, selecting
and evaluating the candidate materials, and choosing the most cost-effective
material. A valuable source of information on selection of materials of
construction is "How to Select Materials" in the November 3, 1980, issue of
Chemical Engineering (reprints of which are available).
The most important factor in selecting material is performance regarding
corrosion. The information listed in Table 10-2 is valuable in estimating
materials' corrosion performance. Additional information on corrosion is
provided in the technical resource document titled "Compatibility of Wastes in
Hazardous Waste Management Facilities."^'
10.2 CHEMICAL REDUCTION
10.2.1 Reduction Processes^ 8 •
Reduction-oxidation, or Redox, reactions are those in which the oxidation
state of at least one reactant is raised while that of another is lowered.
Reduction is used to treat wastes in such a way that the reducing agent lowers
the oxidation state of a substance, reduces its solubility, or transforms it
into a form that can b« more easily handled.
Rase metals such as iron, aluminum, zinc and sodium compounds are good
reducing agents. Sulfur compounds are among the more common reducing agents.
(8)
10.2.2 Types of Waste Treated by Chemical Reduction* '
Liquids are the primary waste form treataole by chemical reduction. The
most powerful reducing agents are relatively nonselecti ve; any material in
the waste stream that is relatively easily reduced can, therefore, be affected.
Reduction has limited application to slurries, tars, and sludges, because
of the difficulties of achieving intimate contact between the reducing agent
and the hazardous constituent. Consequent 1^ , the reduction process would be
very inefficient. In general, hazardous materials occurring as powders or
other solids would usually have to be dissolved prior to chemical reduction.
Table 10-3 lists some of the "u-e common wastes an^, reducing agents that
undergo the reduction process.
-------
10-7
FABLE 1C-2. INFORMATION FOR ESTIMATING CORROSION
AGAINST PERFORMANCE^'
Process Conditions
Main constituents (identity and amount) of waste
Impurities (identity and amount) in waste
Temperature
PH
Degree of aeration
Velocity of agitation
Pressure
Estimated range of each variable
Environmental conditions
Type of Application
What is function of part or equipment?
What effect will uniform corrosion have on serviceability?
What effect will localized corrosion have on usefulness?
Will there be stresses present? Is stress-corrosion cracking a
possibility? Are crevice or pitting corrosion likely to occur?
Is design compatible with the corrosion characteristics of the material?
W'iat is the des'irsd service life?
Experience
Has material been used in identical situations? With what specific result!
If equipment is still in operation, has it been inspected?
Has material been used in similar situation? What was performance,
and specifically, what are differences in old and new situation?
Any pilot-plant experience?
Any plant corrosion-test data?
Have laboratory corrosion tests been run?
What literature is available?
-------
10-8
TABLE 10-3. REDUCTION WASTE TREATMENT APPLICATIONS^
Waste Reducing Agent
Chromium (VI) Sulfur dioxide (often flue gas)
Sulfite salts
sodium bisulfite
sodium hydrosulfite
Ferrous sulfate
Waste pickle liquor
Powdered waste aluminum
Mercury Powdered metallic zinc
Sodium borohydride
Tetra-alkyl-lead Sodium borohydride
Silver Sodium borohydride
-------
10-9
10.2.3 Process Design and Operating Parameters
Analogous to the oxidation process, the design of a system for the chem-
ical reduction of a waste material involves the following design and operating
parameters:
type of tank (or reactor);
reaction rates;
mixing;
location of inlet and outlet pipes;
pH control;
temperature control;
materials selection.
Both type of tank and materials selection have been discussed in the oxidation
section of this chapter.
In general, very simple equipment is recuTed for chemical reduction.
This includes storage vessels for the reducing agents and perhaps for the wastes
metering equipment for both streams, and cortact vessels with agitators to
provide suitable contact of reducing agent and waste. Seme instrumentation is
required to determine the concentration and pH of the waste ana the degree of
completion of the reduction reaction. The reduction process may be monitored
by an oxidation-reduction potential (ORP) electrode. This electrode is
generally a piece of noble metal (often platinum) that is exposed to the
reaction medium and procuces an EMF (electromotive force) output that is
empirically relatable to ihe reaction condition oy revealing tne ratio of the
oxidized and reduced constituents.
10.3 NEUTRALIZATION^
10.3.1 Process Description
The process of neutralization is the interaction of an acid with a base.
The term "neutralization" is often used to describe adjustment of pH to
values within the neutral range of 5.0 to 9.0.
The actual process of neutralization is accomplished by the addition of
an alkaline material to an acidic material or by adding an acidic to an
•ilkaline material, as determined by the required final pH. The primary
products of a neutralization reaction are a salt and water.
-------
10-10
10.3.2 Application of Neutralization Process
Neutralization is a treatment process of demonstrated technical and economic
feasibility that is in full-scale use in a wide spectrum or industries. A
sample list of industries employing this process is presented in Table 10-4.
Neutralization finds its widest aoplication in the treatment, of aqueous wastes
containing s;-ong acids such as sulfuric and hydrochloric, or strong bases such
as caustic soda and sodium hydroxide. The process can, however, be used with
nonaqueous materials (for example, acidic phenols, which are insoluble in
water). Although neutralization is a liquid phase phenomenon, it can also
treat both gaseous and solid waste streams. Gases can be handled by absorption
in a suitaole liquid phase, as in the case of alkali scrubbing of acid vapors.
Slurries can be neutralized, with due consideration for the na'L.'° of the sus-
pended solid did its dissolution properties. Sludges ara also amenable to pH
adjustment, but the viscosity of the material complicates both the process of
pnysical mixing and the resultant contact between acid and alkali, wnich is
essential to the treatment. In principle, even tars can be neutralised,
although the problems of reagent mixing and contact are usually severe, making
the process impractical in most instances. Solids and powders that are acidic
or basic salts can also be neutralized if they are dissolved prior tc initiating
the neutralization process.
Some of the more common applications for pH treatment of acidic ana
alkaline wastes are described in the following paragraphs.
Acid Exhausts - Industrial processes that utilize acids, e.g., sulfuric,
nitric, or hydrochloric, frequently have problems with acid mist in the exhaust.
Scrubbing with water on packed bed columns produces an acid-free gas, but the
spent water must be neutralized. Alkali is usually added automatically to
produce a water stream with a pH of 6.5-7.5 that can be discharged or recycled.
In similar systems, Hue gas desulfurization units absorb and neutralize sulfur
oxide: with alkalie.3 such as lime, limestone, dolomite, or caustic soda.
Petrochemical Waste Streams - Neutralization is applied to: (1) wasnwaters,
acid or alkaline, (2) spent caustics, (3) acid sludges, or (4) spent acid
catalysts. Sulfuric acid and c^-bon dioxide from flue gases are both used to
treat spent caustic wastes. Pits filled with lime, limestone, and even oyster
shells (a source of calcium carbonate) are utilized to neutralize spent acid
sludges.
Sulfuric Acid Pickle Liquor - In small-scale operations (less than 5,OCG
gpd) neutralization of pickle liquor from steel cleaning operations can be
performed in a batch process, usually with quicklime. Typically, pickle liouor
contains en the order of 70 grams of iron and 170 grams of sulfate per liter
(approximately 5 percent sulfuric acid by weight). Large xaste streams can be
handled in continuous flow systems, and other suitable alkaline agents may
be employed. If calcium-based materials are utilized in the nertralization,
-------
10-11
TABLE 10-4. MAJOR INDUSTRIES USING NEUTRALIZATION
(9)
Industry
Pulp and paper
Dairy products
Textiles
Pharmaceuticals
Leather tanning and finishing
Petroleum refining
Grain mil 1 ing
Fruits and vegetables
Beverages
Plastic and synthetic materials
Steel pickling
By-product coke
Metal finishing
Organic chemicals
Inorganic chemicals
Ferti 1 izer
Industrial gas products
Cement, lime, and concrete products
Electric and steam generation
Nonferrous metals-aluminum
Wastewater pH Range
Acidic and basic
Acidic and basic
Basic
Acidic and basic
Acidic and basic
Acidic and basic
Acidic and basic
Acidic and basic
Acidic and basic
Acidic and basic
Ac i d i c
Basic
Acidic
Acidic and basic
Acidic and basic
Acidic and basic
Acidic and basic
Basic
Acidic and basic
Acidic
-------
10-12
calcium sulfate will form a product sludge, which is usually dewatered by
vacuum filtration or placed in a lagoon. The formation of a flocculated
ferrous hydroxide precipitate (at neutral pH) can oroduce a solid with poor
settling and filtering properties. Thus an oxidation step is often employed
since ferric hydroxide is very insoluble, and trmre is an optimum ratio of
ferric to ferrous ions at which the sludge can be handled most readily.
10.3.3 Types of Tanks
The required equipment for neutralization is simple: storage and reaction
tanks with accessory agitators and delivery systems. The tanks may be of any
shape, but must be properly baffled to allow adequate mixing and prevent
"short-circuiting". Frequently, the neutralization is carried out in a
series of tanks to provide better control of the final pH.
Appropriate instrumentation must be provided and include pH measurement
(and possible recording) devices with appropriate sample pumps. The feed of
neutralizing agent may be regulated automatically by the pH monitoring unit,
depending on the requirements of the individual system.
The design of storage facilities for neutializing agents depends on the
chemical reagents employed in the treatment process. Caustic solutions and
acids may be stored in the open, but quicklime should be kept in waterproof
silos, hoppers, or even bags. Delivery systems depend on the physical form
of the reagents. Liquids may be transferred with pumps, while slurries can
be moved through gravity piping, pumps, or open flumes. Ancillary equipment
might include installations such as equalization basins, clarfiers, or vapor
removal systems, depending on the specific neutralization scheme.
In dealing with acids and alkalines, appropriate materials of construction
are required to provide reasonable service life for equipment. Corrosion may
result in deterioration of a construction material, e.g., lead is attacked by
hydrochloric acid. In many cases, the specific concentration of a reagent is
important in selecting the correct material used in pumps, pipes, tanks, etc.
Examples of materials recommended for handling different acids and alkalies
at ambient temperature are:
sulfuric acid (75-95 percent concentration) - lead
(10 percent concentration) - lead or rubber
hydrochloric acid (concentrated or dilute) - rubber
sodium hydroxide (concentrated) - 31G stainless steel (SS) or -ubber
(dilute) - 316 stainless steel (SS), rubber, carbon
steel , or cast iron
calcium hydroxide - 316 SS, rubber, or carbon steel.
-------
10-13
Other less comnonly used materials include glass, metal alloys such as monel,
plastics, such as PVC, and even wood. The expense of such materials frequently
precludes their use except for small-scale applications or in situations where
there is no alternative. It is important to realize that a vessel nead not be
constructed entirely of one material; it may he lined Vnth lead, rubber, glass,
plastic, or other corrosion-resistant materials. Expected length of service,
temperature of operation, desired physical strength, liquid flow *-dte, and
mecnanical abrasion are some of the other factors to be considered in selecting
materials.
In general, fiberglass tanks or tanks lined with an organic material are
used for storing acids that present corrosion problems in contact with most
metals.
10.3.4 Environmental Impacts
After neutralization a waste stream will usually show an increased total
dissolved solids content because of the addition of the chemical agent, but
there may also be an accompanying reduction in the concentration of heavy metals
if the treatment proceeds to the basic pH range. Conversely, in neutralization
involving the addition of acid to alkali, there is the possibility of disso-
lution of metal-containing solids. This may, on occasion, be disadvantageous,
particularly if the suspended matter is slated for removal, e.g., by filtration.
For example, the anions resulting from neutralization of sulfuric and hydrochloric
acids are sulfate and chloride, respectively. These ions are not considered
hazardous, but there are reconmended limits for discharge, based primarily on
problems in drinking water. The common cations present after neutralization
involving caustic soda and lime (or limestone) are sodium and calcium (possibly
magnesium), respectively. These ions are not toxic and there are no recommended
limits; calcium and magnesium are, however, responsible for water hardness and
the accompanying scaling problem. Limestone neutralization converts the carbonate
to harmless carbon dioxide gas.
With regard to atmospheric emissions, one must be cautious not to neutralize
wastewater streams indiscriminately. Acidification of streams containing certain
salts, such as 'iulfide, will produce toxic gases. If there is no satisfactory
alternative, the gas must be removed through scrubbing or some other treatment.
In cases where solid products are formed (as in the precipitation of calcium
sulfate, or heavy metal hydroxides), clarifier/thickeners and filters must be
provided. If the precipitate is of sufficient purity, it would be a salable
product; otherwise, a disposal scheme must be u£vise<1.
O
-------
10-14
10.4 PRECIPITATION, FIOCCULATION, AND SEDIMENTATION^11^
Precipitation, flocculation, and sedimentation are discussed together in
a single section because in waste treatment they are most commonly used together
as consecutive treatments to the same stream. Precipitation removes a substance
in solution and transforms it into a second phase, often in the form of solid
particles that may be small or even colloidal. Flocculation transforms small
suspended particles into larger suspended particles so that they can be more
easily removed. Sedimentation removes the suspended particles from the liquid.
10.4.1 Precipitation
(a) Process Description. Precipitation is a physicochemical process
whereby some or all of a substance in solution is transformed into the solid
phase and thereby removed from solution. Precipitation involves an alteration
of the chemical equilibrium relationships affecting the solubility of the
component(s). This alteration can be achieved by a variety of means. Most
precipitation reactions for industrial or waste treatment purposes are induced
by one cr a combination of the following steps:
• adding a substance that will react directly with the substance
in solution to form a sparingly soluble compounds,
• adding a substance that will cause a shift in the solubility
equilibrium to a point that no longer favors the continued
solubility of the substance originally in solution
• changing the temperature of a saturated or nearly saturated
solution in the direction of decreased solubility; since
solubility is a function of temperature, this change can cause
ionic species to coi:ie out of solution and form a solid phase.
The most common precipitation reactions involve the removal of inorganic
ionic species from an aqueous medium. For example, zinc chloride is highly
soluble in water, as is sodium sulfide. Zinc sulfide, however, has an extremely
low solubility in water. Thus, if an aqueous solution of zinc chloride is
mixed with an aqueous solution of sodium sulfide, zinc ions and sulfide ions
will rapidly combine to form solid line sulfide particles.
It is important to recognize that the term "precipitation", as strictly
defined, refers only to the conversion of dissolved substances into insoluble
ones in order to facilitate their subsequent removal from the Mquid phase.
Precipitation per se does not refer to any of the liquid-sclid separation
processes that are required to remove the precipitated solid particles from
the original volume of liquid. In order to effect the removal of precipitated
parf'cles From a volume of liquid, it is very often necessary to apply
additional process steps, and these often involve flocculation, sedimentation,
-------
10-15
and/or some control that will determine the final particle size—and produce
an easily separable solid (or crystal).
(b) Process Design and Operating Parameters. The parameters of interest
for precipitation include the time required for reaction, the solubility
product of the substance to be precipitated, and the effect of the reaction upon
the tank construction materials and types of tanks.
Physically, most precipitation reactions are carried out by adding the
appropriate chemicals to the solution and mixing thoroughly. Reagents should
be added in a manner that minimizes contact of the Concentrated reagent with
the tank surface. Although most precipitation reactions take place 'i-xtremely
rapidly, a moderate amount of time is usually required to allow the chemicals
to be dispersed throughout the solution. Characteristically, the solid particles
when first formed, are very small. Depending on the nature of the chemical
system involved and the types of further treatment applied, the solid particles
can remain as submicroscopic precipitation nuclei, or very small colloidal
particles; or they can grow into larger particles. Since mixing can shorten
the disparsion time of chemicals, some type of mixing equipment should be used.
The solids formed by precipitation are salts and should not pose severe
corrosion problems. The chemicals added to the waste in order to induce
precipitation are, however, often corrosive in nature, such as concentrated
hydroxides or strong acids. Again, caution should be taken when adding these
chemicals to the waste and upon mixing o'f the chemicals in order to minimize
contact of concentrated agents with the t^nk surface.
10.4.2 Flocculation
(a) Process Description. Th" term "flocculation" as defined here encom-
passes all jf the mechanisms by which the suspended particles agglomerate into
larger particles, including the addition of flocculating agents.
Many liquid-solid separation processes, such as sedimentation, are based
on the use of gravitational and/or inertia! forces to remove solid particles
from a liquid. It is generally true that the larger the particle size, the
easier will be the removal of the particle from the liquid.
A variety of mechanisms is involved in flocculation whereby small particles
are made to form larger particles.
Most of these mechanisms involve surface chemistry and particle charge
phenomena. In simple terms, these various phenomena can be grouped into the
following two sequential mechanisms:
-------
10-16
• chemically-induced destabilization of the repulsive surface-related
forces, thus allowing particles to stick together when contact
between particles is made;
t chemical bridging and physical enmeshment between the now nonre-
pelling particles, thus allowing for the formation of large
particles.
Once suspended particles have been flocculated into larger particles,
they can usually be removed from the liquid by sedimentation, provided a
sufficient density difference exists between the suspended matter and the
1iquid.
As in precipitation, the solids formed by flocculation are salts and
should not pose severe corrosion problems. Chemical reagents that are corrosive
in nature should, however, be added to a tank and mixed with caution, so as
to minimize contact of the reagent with the tank surface.
10.4.3 Sedimentation
(a) Process Description. Sedimentation is a physical process whereby
particles suspended in a liquid are made to settle by means of q<-avitational
and inertial forces acting on both the particles suspended in the liquid and
the liquid itself. Basically, particles settle out of d liquid by creating
conditions in which the gravitational and inertial forces acting on the
particle in the desired direction of settling are greater in magnitude than
the various forces (drag forces, inertial forces) acting in the opposite
direction. This force differential causes the particles to travel in the
desired direction.
The fundamental elements of most sedimentation processes are:
• a tank or container of sufficient size to maintain the liquid
in a relatively quiescent state for a specified period of time;
• a means of directing the liquid to be treated into the tank
in a manner tnat is conducive to settling;
• a means of physically removing the settled particles from the
liquid (or the licuid from the settled particles, whichever
the case may be).
Sedimentation can be carried out as either a batch or a continuous
process. Continuous processes are by far the most common, particularly wnen
large volumes of liquid an; to be treated.
-------
10-17
Depending on the specific process configuration, the settled particles
are either -ernoved from the bulk u,- the lu;uid, cr the liquid is separated
from the settled particles by decantation. The end result, and single purpose,
of sedimentation is the separation of liquids from solids. The fraction of
liquid containing the settled particles is commonly referred to as "sludge".
(b) Process Design and Operating Parameters. Because sedimentation is
purely a physical separation, the type of tank used to provide the separation
is the most important factor. Since there is little control over the particle
size or density, the only method that can be used to accommodate these factors
is to design tanks to handle the different settling characteristics of various
wastes.
Sedimentation can be carried out in rudimentary settling ponds (surface
impoundments), conventional settling basins, or in more advanced clarifiers
that arfl often equipped with built-in flocculation zones and tube-like devices
that enhance settling.
In settling ponds, the liquid is merely decanted as the particles accumulate
on the bottom of the pond and eventually fill it. Often the pond is period-
ically scraped by mechanical shovels, draglines, cr siphons. Sedimentation
basins and clarifiers are more sophisticated and usually employ a built-in
solids collection and removal device such as a sludge scraper and draw-off
mechanism. Sedimentation basins tend to be rectangular in configuration,
usually employ a belt-like collection mechanism, and tend to be used more for
the removal of easily settleable particles from a liquid.
Clarifiers are generally circular and are usually used in applications
that involve precipitation and flocculation in addition to sedimentation. Very
often all three processes take place within the same piece of equipment, since
many clarifiers are equipped with separate zones for chemical mixing and precio-
itation, flocculation, and settling. Certain clarifiers are equipped with
low lift turbines that mix a portion of the previously settled precipitates
with tne incoming feed. The practice has been shown to enhance certain
precipitation reactions and promote favorable particle growth.
There are many variations of the sedimentation process, encompassing a
wide variety of commercially available equipment.
10.4.4 Precipitation, Flocculation. and Sedimentation
Applications to Hazardous Wastes"
The processes of precipitation, flocculation, ar>d sedimentation are
finding widespread application in the treatment of wastewater streams containing
soluble heavy metals and colloidal hazardous substances. A summary of general
wastewater treatment applications in a number of major inoustries is presented
below.
-------
10-18
(a) Iron and Steel Industry. Wastewater streams from the iron and
steel industry are cnaracterized by a very high concentration of settleable
suspended particles and a relatively low concentration of dissolved heavy
metals, such as ferric iron, zinc, lead, chromium, and manganese. Sedimen-
tation is currently in widespread use for the removal of suspended solids.
Precipitation (usually witn lime and alum) is used to remove heavy metals.
(b) Aluminum Industry. Wastewater streams from the aluminum industry
contain high concentrations of soluble fluoride salts. The commonly used
treatment process entails precipitation as calcium fluoride (with lime),
flocculation, and sedimentation to remove the fluoride as solid particles.
(c) Copper Industry. Wastewater streams from copper smeltiny and
refining contain a variety of soluble and colloidal heavy metals (arsenic,
cadium, copper, iron, lead, mercury) that can be removed, to varying degrees
of effectiveness, by precipitation, flocculation, and sedimentation using
either lime or scdium sulfide.
(rl) Metal Finishing^Industry. Soluble salts of copper, nickel, cadmium,
and chromium are removed rrom wastewater streams by precipitation, for example,
by utilizing lime to form insoluble hydrated oxides followed by flocculation,
and sedimentation. Chromium usually present as chrorr-ate or dichromate must
first be reduced to the trivalent state so that the precipitation process will
be effective.
(e) Inorganic Ch*:," >aIs Industry. Many manufacturing processes within
the inorganic chemicals industry produce wastewaters that contain suspended
solids and soluble heavy metals. Manufacture of titanium dioxide and chromium
pigments produce such wastewaters. Precipitation, flocculation, and sedimen-
tation are used to treat many of these wastewaters.
(f) Sludge Thickening. The f';rsc step used in a sludge dewatering
process is often simply a better sedimentation process commonly referred to
as "sludge thickening" or ''gravity thickening". In the gravity thickening,
the sludge is sent to a type of c'larifier in which the already settled solid
particles are allowed to settle further and compact. Typically, the supernatent
liquid is returned to the main clarifier that performs the initial liquid-solid
separation, while the "thickened" sludge is drawn off and either disposed of
or sent to further dewatering steps, such as vacuum filtration or centrifugation
10.4.5 Environmental Considerations
Since precipitation, flocculation, ana sedimentation processes are
basically liquid-solid separation processes, two output streams will resu't -
a high-volume purified liquid stream and a low-volume slurr*:ed solids stream.
There are usually no air emissions from the process. The processes do ernolov
equipment that exposes large open surfaces of liquid to the atmosphere, and,
if that liquid is other than water and is highly volatile or contains hign'y
volatile components, air emissions could result.
-------
10-19
(8)
REFERENCES
(1) 40 CFR 264.192(3), Subpart J (46 Fed. Res. 2867 [January 12, 1981]}.
(2) Ualter J. Weber, Physiochemical Processes for Water Quality, Chapter 8,
New York: Wiley-Interscience, 1972. !
(3) Nancy J. Cunningham, Physical, Chemical, and Biological Treatment Tech-
niques for Industrial Waste, Chapter 35, Cambridge, Mass.: Arthur 0.
Little, 197&:
(4) Hetcalf and Eddy, Wastewater Engineering Treatment, Disposal and Reuse,
3rd ed., New York: McGraw-Hill, 1979, Cnapter 5.
(5) Michael Henthorne, "Understanding Corrosion", Chemical Engineering Desk-
book, Vol. 79, No. 27, December 4, 1972, p. 19.
(6) Gary w. Kirby, "How to Select Materials", Chemical Engineering, November 3,
1Q30, pp. 87-130, Reprint No. 046.
(7) "Compatibility of Wastes in Hazardous Waste Management Facilities: A
Technical Resource Document for Permit Writers", Fred C. Hart Associates,
Inc., for U.S. EPA, Office of Solid Wastes, Washington, D.C., 1982.
Nancy J. Cunningham, Physical, Chemical and Biological Treatment Techniques
fo*1 Ind-jstr-Jal V'3;te> ArtSijr 0. Little, Inc., Cambridge, *as3., *!:venber, •
" ~
976," Chapter ~3fi.
(9) Lawrence N. Davidson, Physical, Chemical, and Biological Treatment Tech-
niques for Industrial Waste, Arthur D. Little, Inc., Cambridge, Mass.,
November, 1976, Chapter 34.
(10) 40 CFR 264 and 265 (45 Fed. Reg. 76076-83 [November 17, 1980]).
(11) Edmund H. Dohnert, Physical, Chemical, and Biological Treatment Techniques
for Industrial Wastes, Arthur D. Little, Inc.. Cambridge. Mass.. November.
1976, Chapter 23.
-------
A-l
APPENDIX A CONTENTS
Table A-l. Regulatory Analysis of Tanks
-------
APPEND]X_ A
TABLE A-l REGULATORY ANALYSIS OF TANKS
Section of The Preferred Section Nu.nter of
4j3 _Cf_R__ Permit Application Outline(d)
. 16 D-2a Tanks to store or treat hazardous wastes
(a) D-2a Reference to design st.ndards or other in formation
for design and construction of the tank
(b) D-2b Description of design specifications and corrosion
and erosion characteristics of construction/lining
materials f"
ro
ic\ D-2a Tank dimension0, capacity, and shell thickness
(d) D-2c Process flow diagram (PFD) and pipinq and instru-
mentation diagram (P&ID)
(e) D-2a Description of feed systems, safety cutoff, bypass
systems, and pressure controls (e.g., vents)
D-2c Description of procedures for handling incompatible,
igr.itable or reactive wastes, including the use of
buffer zones
264.190 Applicability
264 190(a) Applicable to owners/operators of facilities that use
tanks to treat, or store hazardous waste
-------
TABLE A-l (Continued)
l-Vi t ion of
4:) nk
Tne Preferred Section Nunber of
Pejrini t AJJJJ 1_i_c aj.i_on Out 1 i ne(d'
D-2a
264.192
264.1fJ?(a)(l)
?S4.192(a}{2)
264.192(b)
D-2c
D-2b
D-2b
D-2b
D-2c
0-2c
Subject Covered
Tanks must have sufficient shell strength and
pressure controls (e.g., vents to assure that
they do not collapse or rupture. The Regional
Administrator will review the design of tanks,
Including the foundation, structural support,
seams and pressure controls. Minimum shell thick-
ness must be maintained at all times to ensure
sufficient shell strength; factors to be con-
sidered include the width, height, and materials of
construction of the tank, and the specific gravity
(S.Ci.) of the waste. Regional Administrator shall
rely upon appropriate industrial design standards
and other available information. *
Cx
General operating requirements
Materials which are incompatible with the materials
of construction of the tank must not be placed in
the tank unless protected from accelerated corrosion,
erosion, or abrasion :
Throuoh inner liner or coating
Through cathodic protection or corrosion inhibitors.
Must use practices to prevent overfilling of the
tank
Controls such as waste feed cutoff system or bypass
system to a standby tank
-------
fAlU F A-1 ( C<.111 i nued]
Si-i. I Uiii i) f Ihe Preferred Section Number of
4.) (. I rf Pennit Application Outline^' _ Subject Cohered __
2M !''2(t))(2) D-2c (or fJ.P.L0_y_e.rll _ta_nk_s, mdintenance of sufficient
freeboard to prevent overtopping by wave or wind
action or precipitation
LV1 19-1 F-2b(2) Inspections :
2t4.llJ4(l) F-2b(2) Overfilling control equipment--once each operating
day
.VI.194(2) F-2b(?) Data gathered from monitoring equipment--once
each operating day
-------
The Prv ti-ri i>d ',!•< I i on Mumbvr .) f
Permit Apji 1 n ,11 i un Ou t 1 i in;'''' _ Subjec t_ C_o_y_e_r(ed__
I '.;!• Special requirements for iqni+abl'1 or reactive
wast ?s
(-Si' Ignitable or reactive waste must not be placed in a
tank uiless:
I-be The waste is treated so that the resulting
waste no longer meets the definition or ignitable
or reac t i ve was te.
?i'j'1. l'JH( a) (?) foe or stored suf;h that it is protected from any con-
ditions which may cause ignition or reaction
t'M. l')H(a) ( )) r'-Le or the tank is used solely for emergencies f
?M.19H(b) f-'je Compliant, with the buffer ?one requirements or
NFPA's "Flar.imable ar:d Combustible Liquids Code",
1977 or 1981.
1'M.l'jy f-'jf bpeci
-------
6-1
APPENDIX B CON~ENT_S_
3.D CORROSION AND DETERIORATION OF MATERIALS OF CONSTRUCTION
B.I Materials of Construction
B.1.1 Carocn Steels
B.I.2 Alloy Steels
8.1.3 Concrete
B.I - Plastics
3.1.1.5 Rubbe>-
3.2 Mac.hinism of Deterioration of Materials
3.2.1 Metals
B.2.2 Concrete
3.2.3 Plastics and Rubbers
3.3 AODroach to Permitting
3.4 Gaskets, Liners, and Coalings
B 4.1 Gaskets
3.4.2 Lining ana Coating Materials
-------
B-2
APPENDIX 8
CORROSION AND DETERIORATION OF
MATERIALS OF CONSTRDCTION
Title 40 CFR 270.16(b) requires "a description of design
specifications including identification of construction materials
and lining materials (include pertinent characteristics such as corrosion
and erosion resistance)".- Part. 25"1. lS2(a) ,-requi res that "wastes and other
materials which-are .incompatible with the material of construction of the
tank must not be placed in the tank unless the tank is,protected from
accelerated erosion or corrosion through-the use of (1) an inner liner
or coating-which is compatible with the waste or material ... or (2)
alternative means of protection-. . ." Sections. 3.2.6 and 8.6 of this
manual indicate the need for corrosion rate data and other information to
-calculate expected service life and the required inspection frequency of
tanks.
The purpose of this Appendix is to present general information to
the permit writer on how to approach the subjects of corrosion resistance,
compatibility, and corrosion rate to-assist him in judging compatibility
and in writing the inspection frequency specification. Many companies have
corrosion metallurgists and other specialists who make lifetime commitments
to this field; and there is a large body of accompanying published and
unpublished literature. Therefore, it is far beyond the scope of this
manual to present specific data to cover specific situations. The
information presented is necessarily general in nature and will often
not be useful in the analysis of-specific tanks.and the liquid to be
contai ned.
B.I Materials of Construction
There is a large variety of materials of construction from which
tanks, tank liners and coatings, and tank auxiliaries may be constructed.
The liaticnal Association of Corrosion Engineers (flACE) Corrosion Data Sur^e*.
attempts to report in its Metals Section corrosion data in tabular array for
-------
5-3
25 different types of metals including mild steel, stainless steel, copper
base alloys, nickel base alloys, aluminum, lead, and other expensive metals
such as gold, tantalum, and zirconium. NACE, in its Non-Metals Section
of the Corrosion Data Survey, reports similar data (where available) for
up to 36 types o* materials including many plastics (including fiber-
reinforced plastics), carbon-graphite, ceramics, concrete, glass, glassed
steel, rubbers,and wood.
It is well recognized that the proper selection of a material
of construction involves an economic analysis to achieve lowest capital
and maintenance costs over the anticipated lifetime of the project. In
some cases where color or product purity is of concern such as in the
chemical industry, this will be factored into the analysis; corrosion
products may color products or be unacceptable impurities. Prudent
management will usually specify Materials that will be relatively trouble-
free over the life of the project because forced shutdowns may result in
production of off-grade product or lost sales revenues and profits. There-
rore, selections of materials of construction are usually made using a
conservative bias.
Historically, carbon steel tanks have been the least expensive.
More recently, fiberglass-reinforced plastic (FRP) tanks have become
generally less expensive than 304 stainless steel ta;.
-------
B-4
After the above steels have been considered, the next step is
to review the possibility of using tanks lined with rubber, lead, or
possibly coated with other non-metal lies . Alternatively, special metal
alloys may be considered at this cost level. The very costly noble
metals such as titanium, tantalum, zirconium, and gold are specified
only as a last resort.
Thus, when a material of construction is being selected for
use with a chemical, the corrosion engineer will evaluate the compati-
bility of the low-cost materials first; if carbon (or mild) steel has
a low corrosion rare of less than 2/1000 inch per year, then the proper-
ties of the stainless steels are of no interest. Conversely, if mild
steel has a moderately low corrosion rate of less than 20/1000 ,nch
per year, the engineer is likely to investigate the compatibility of the
liquid with the 301 types of stainless steel and FRP, but not 2>16 types
of stainless. This orientation has been used to prepare Table 8-1,
which shows the co npati bi 1 i ty of common materials of construction with
various chemicals. The specific chemicals included in the table were
selected to represent each of the common classes of chemicals. Generally,
assessment of compatibility was very severe; that is, unless the corrosion
rate for metals was less than 2/1000 inch per year, the m.etal or FRP
was shown in the table as incompatible. Although there are hazards in
generalizing by the non-specialist, when the corrosive properties of a
chemical on a material are unknown, the corrosion engineer is likely to
base his suggestion for a material of construction by analyzing the cor-
rosive properties of other chemicals that are chemically similar for
which the corrosion characteristics are known.
As background the following sections present generalizations
the common construction materials used for tanks. This infor-
should not be accepted as being adequate for specific situations.
6.1.1 Carbon 5tee1_s . Carbon or mild steel is the most
used steel in the petroleum and chemical industries.
• Can be used to store alkalies; for examole, caustic soda
can be stored in concentrations up to 75 percent at
temperatures ranging to 212 F
• Only slightly subject to corrosion by brines and seawate
-------
6-5
TABLE 8-1. COMPATIBILITY OF MATERIALS OF CONSTRUCTION
WITH VARIOUS CHEMICALS
Compatible With
Incomoatible With
Mineral Acids
Sulfuric
Hydrochloric acid^ '
Nitric acid
Phosphoric acid
Organic Acids
Acetic acid
Bases
Sodium hydroxide
FRP(2)
Mild steel
Rubber-lined
FRP
FRP
FRP
(4)
FRP
FRP
Mild ,st.ee~j
,(5)
Mild steel
Mild steel
Mild steel
Mild steel
Mild steel
(5)
A.mmoni urn hydro xi de
Aqueous Salts
Calcium chloride
Sodium su'l fate
Copper sulfate
Ferric chloride
Sodium hypochloride
Starnous chloride
S'jdi un chlori de
Alu:r
Mild steeP b'
FRP
FRP
FRP
FRP
FRP
Special metal alloys
Stainless steel (ss)
to 5 or,
Noble metals
FRP
FRP
Mild steer J'
Mild steel(7)
Mi Id 'steel
Mild stee1
Mild steel
Mild steel
FRP
Mild steel
Mild steel
;i) ' Huiibers refer to notes at the er,o of the table.
-------
B-6
TABLE B-l (Continued)
Compatible With
Incompatible With
Solvents
Perchlorpethylene
Carbon tetrachloride
Ethyl alcohol
Methyl ethyl Ketone
Acetone
Mi seel laneous
Benzene
Hexane
(17)
i i ny
Ani 1 i ne
Ni trobenzene
Phenol
Chlorobenzene
Naphthal ene
Benzoic acid
Di ethyl ami ne
Formaldehyde
Mild steel
FRP(1D
FRF
FRP
13)
15)
Mild steel
Mi !d steel
FRP
(16)
us)
Stainless steel
FRP' ', mild steel
Mild steel and
stainless steel
Mild steel
Stainless steel
Mild steel
(20)
special metals
(nickel-case alloys)
Mild
FRP
Stainless steel
Mild steel
Mild steel
Stainless steel
Mild steel ^2^
Mild steel (u)
Mild steel
FRP
FRP, mild steel
FRP
FRP
(21
Mild steel
Mild steel
-------
5-7
TABLE 8-1 (Continued)
(1) Needs the attention of a corrosion specialist. FRP is good up to
70 percent concentration. Mild steel (M.S.) 'is 'good for concentrations
of from §3 to 98-percent.
(2) Fiberglass-reinforced polyester plastics (FRP) have been considered
here However, there are fiberglass-reinforced epoxy resins avail-
able which are not considered in this table.
(3) FRP is good to 30 percent concentration. No organic solvents should
be present. NACE has a graph for the compatibil ity "of various metals
for HC1 use.
(4.-). FRP is good to 15 percent concentration.,.
(5) M.S. is good only to 25,C. 316 S.S. is recommended for service
conditions above 25 C.
(6) FRP is good to about 50 percent concentration.
(7) M.S. is incompatible after about 5 percent concentration at 100 C.
(8) FRP is good to about 25 C.
(9) FRP is good t~ about .125 C.
(10) FRP is good for 95 percent concentration and 21 to 66 G.
(11) FRP is good from 10 to.35 C.
(12) Mild steel is incompatible for concentraitons below 100 aercent.
(13). FRP is good for 10 percent concentration and 21 to 79.5 C.
(14) Mild steel is incompatible for concentrations below 100 percent.
115) FRP is good at 10 to 32 C.
(1C) Mild steel is good for 100 percent solvent to 100 C.
(17) NACE did not have data for gasoline; therefore, they were obtained
from Petroleum Processing Handbook by W..F. 8land and n.L. Davidson
( 13677", pp 5-3.
(13) Stainless steel :s qood at 100 percent concentration.
(10) F^r is yjo-j for 5 percent concentration and 2'\ to 52 C.
-------
TABLE 8-1 (Continued^
(20) Mild steel is good for 100 percent concentration.
(21) FRP is good for only 100 percent concentration and 21 to 27 C;
therefore, it is listed as incompatible.
(22) Mild steel is good only at 100 percent concentration and uo to 100 C
-------
B-9
& Commonly used to store organic solvents a.id similar
chemi cals
• Limited corrosion resistance to certain wastes; there--
fore, extra thickness for corrosion allowances is oftc-n
needed beyond tlis ir.inimum thickness requir°d for struc-
tural integrity when no lining or coating is used.
• Should not be used on contact with hydrochloric,
phosphoric, or nitric acid.
3.1.2 Al1oy Steels. Stainless steel is the most widely used
alloy steel. At high temperatures it is highly resistant to corrosion and
oxidation while maintaining considerable strength.
The following is a list of the types of alloy (stainless )steels
and their characteristics:
• Austenitic steel (types 302, 304, 321, 326, 316, 317, and
others)
- Is the most highly resistant of stainless steels to
nary acids, includi^q hot or cold nitric = cid
- Retains strength at temperatures as low as liquid helium
- Responds well to severe strebb at elevated temperatures
- Subject to pitting with chloride ion
• Martensitic steel (types "OS through 410)
- Is less corrosion resistant than austenitic steel
Used for mildly corrosive environments such as organic
exposures
B.1.3 Concrete. This material is used predominant!v in large
open tanks and treatment basins. Several characteristics of concrete are
listed below:
• Susceptible to freeze-thaw cracking and deterioration
if not properly air entrained
• Subject to attack by nearly all sulfate salts if not
made with sulfate-resistant cement
-------
8-10
• Subject to attack by many chemicals including alum,
chlorine, ferric chloride, sodium bisulfite, sulfuric
acid, and sodium hydroxide (<20 percent).
« May be permeable to some liquids.
B•1 -4 Plasti cs. In general, plastics have the following
cnaracteri sties:
t Have excellent resistance to weak mineral acids and
inorganic salt solutions
• Are qood electrical and thermal insulators
• Do not corrode from chemical reactions
• Do not react to small changes in pH, minor impurities,
or oxygen cont
Plastics are widely used for coating and lining materials and
include polyethylene, chlorinated oolyether, cellulose acetate butyrate,
polyamide, polypropylene, polyester resin, and epoxy.
t Polyethylene is the least costly plastic that is com-
mercially available. The carbon-filled grades are
resistant to sunlight and waatharing.
• Chlorinated po'lyether can withstand temperatures
up to 225 F. It is not affected by dilute acids,
alkalis , or salr.s. However, nitric acid over 25 percent
in concentration, aromatics, and ketones cause degradation.
• Cellulose acetate butyrata is affected by chlorinated
solvents, but not by dilute acids or alkalis.
• Polyamide (nylon) resists a number of organic solvents,
but is not resistant to phenols, strong oxidizing agents,
or mineral acids.
• Polypropylene has characteristics similar to those of
polyethylene, and it can be used at temperatures greater
than 250 F.
• General purpose polyester resins, when reinforced witn
fiberglass, have good strength and good chemical resistance
£/c2yt to alkali*. Polyesters containing bisphenoi are-
rore alkali resistant. The Ismoarature lirrit for j-.ira
'july^Gters is about 290 F.
-------
B-ll
« Epoxy has good chemical resistance to non-oxidizing
and weak acids. It is also resistant to weak alkaline
solutions.
3.1.1.5 Rubber. Rubber and elastomers are also frequently
used as coating and lining materials. In addition to natural rubber,
a number of synthetic rubbers have been developed. While none have all
the properties of natural rubber, some are superior for specific uses.
Natural rubber is resistant to dilute mineral acids, alkalis,
and salts, but not to oxidizing agents, oils, benzene, and ketones.
Hard rubber is made by adding 25 percent or more sulfur to natural or
s/nthetic rubber, thus making it both hard and strong.
• Chloroprene or neoprene rubber is resistant to attack by
ozone, sunlight, oils, gasoline, and aromatic or
halogenated solvents.
• Styrene rubber has chemical resistance similar to natural
rubber.
• Nitrile rubber is resistant to oils and solvents.
• Butyl rubber's resistance to dilute mineral acids and
alkalis is exceptional; its resistance to concentrated
acids, except nitric and sulfuric, is good.
• Silicone rubbers, also known as polysiloxanes, have out-
standing resistance to high and low temperatures end to
aliphatic solvents, oils, and greases.
9 Chlorosjlfonated polyethylene, known as hypalon, has out-
standing resistance to most ozone and oxidizing agents
except fuming nitric and sulfuric acids. Its oil resis-
tance is good.
• Fluoroelastomer combines excellent chemical and hiah -
temperature resistance.
• Polyvinyl chloride elastomer was developed to
overcome some of the limitations of natural and synthetic
rubbers. It has excellent resistance to mineral acids
and oetroleum oils.
• The cis-polybutadiene and cis-pclyiscprene rubbers are
almost duplicates of natural rubber.
-------
8-12
• The newer ethylene-propylene rubbers have excellent
resistance to heat and oxidation.
6.2 Mechanism of Deterioration of Materials
The purpose of this section is to orient the permit writer to
the fact that the mechanism of deterioration differs for various classes
of materials .
.2.1
Corrosion is the primary process by which metals deteriorate.
In the process of corrosion, the metal is reacted with a cnemical in the
liquid (or atmosphere) to form a non-metallic reaction product such as
iron oxide or ferric chloride that has no strength and which is normally
dissolved into the liquid. In some cases, intergranular corrosion may
occur where the corrosion reaction occurs at the grain boundaries of the
crystals in the metal matrix with a resultant loss of strength. If
dissimilar metals are used in tank fabrication and assembly or if there
are crevices or pits in the tank's surface, then galvanic-electrochemical
reactions :.nd, tl"'js, corrosion of metals may occur.
Erosion is another form of deterioration that may occur with
nearly all of the materials of construction. Erosion usually occurs because
of a wearing action due to the presence of solids in a solution and high
velocities at the ir*»tal or plastic surface. In is wearing action will
seldom occur i,i properly designed tanks. However, if erosion is combined ^it
corrosion, the rate of metal removal may be very high.
3.2.2 Concrete
In some respects, the deterioration of concrete is similar to
that of metals; chemical reacticns are involved. However, several kinds
o* reactions may be involved. The formation of concrete involves the
rorma';'!on of crystalline mineral hydrates to bind the mixture of minerals
and accre^ates into an integral structure. The formation of concrete is
-------
B-13
referred to as hydraulic bonding (which is a misnomer). Nevertheless,
the chemicals.in,a liquid may react with either the hydrate portion of
the crystal the minerals, or the aggregate. Concrete is very susceptible
to attack by acids and aqueous solutions of sulfate salts. In some cases,
concrete may b% permeable to certain liquids even though MACE aata indi-
cates use of concrete is recommended.
d.2.3 Plastics and Rubbers
Although seme reactions may occur between liquids and polymeric
materials, their failure in service is seldom due to reactions. Nor do
such materials normally fail due to complete dissolution--the dissolving
of the polymer into the liquid. Such materials usually fail by absorption
of liquids into the polymer with subseauent swelling and softening of the
plastic resulting in the materials loss of strength. Occasionally.
the material may become discolored or embrittled due to reactions. Poly-
.rers are also subject to stress cracking or crazing upon exposure to some
organic chemicals.
6.3 Approach to Pernitting
The permit writer must ascertain the effect of the waste pro-
posed ^or storage.upon the tank construction materials and the liner
rr.dterialsr (i f present). For further discussion of general compatibility
between the waste proposed for storage and the .tank materials, refer to:
• Conoatibl 1 i ty- of Wastes in Hazardous Waste Management
fa c ilities: > A Technical Resource Document.
• Perry's Chemical Engineers' Handbook, which contains a
specific section on corrosion
• Information published by the American Concrete Institute.
However, trie.National Association, of Corrosion Engineers has
-r-eoa'-ed two bocks, :lon-'letals Section--r.orr-.ocion Data Survey., fifth
edi.tion, NACE, Houston, Texas (197,5) and Metals Section — Corrosion Dat^
" j •'••/o y , f i f r.h'«di tion, Houston, Texas (1974) that nort onlv provide
information about general .conpatioility, but also present numerous footnotes
-------
B-14
about the presence of non-uniform corrosion or the type of failure that
can be expected. This latter type of information is essential to the
permit writer in specifying the required frequency of inspection and to
\
assure that appropriate inspection procedures are used to identify potential
tank defects.
Other good sources of information are manufacturers of the
materials of construction and occasionally manufacturers of tanks.
Finally, one of the best sources of qualitative-type information that
can be helpful in specifying inspection frequencies is the manufacturers
of the chemical constltutents of hazardous wastes.
It is recommended that the applicant far required to orovide
such information at the time the permit application is mads to fully
support the applicant's selection of a suitable material of construction
and suggested tank inspection frequency.
B.4 Gaskets, Liners, and Coatings
Many of the gasket, liner, and coating materials have been
covered in sections B.2 through 8.3. Nevertheless, some further infor-
mation is presented for clarification.
B.4.1 Gaskets
Gaskets serve as fillers in static clearances that usually occur
at concentric cylinders such as at flanges. Sealing is achieved by sub-
jecting effective compression through bolts o- other mechanical means.
Improper gasket installation can easily result in a leak. Therefore, extra
care should be given to select the proper type and material of construction
for the gasket to ensure quality control during installation.
The most common types of gaskets are cylindrical or concentric,
o-ring joints, and valve seats. Gasket selection should be based on site-
specific objectives. Curing installation, care should be taken so that
the gasket is properly placed in the flange and that it is not excessively
compressed beyond the material's elastic limit. It should be noted that
proper materials selection is imperative to avoid gasket deterioration, as
-------
B-15
a result of incompatibility between hazardous meterials stored in the
tank and the material of construction of the gasket.
Proper maintenance of gaskets will enhance the life and maxi-
mize performance. It is imperative that the manufacturers' recommen-
dations for installation as well as maintenance be followed. In some
cases, if deterioration is detected, the gasket should be immediately
replaced.
Additional information about the important properties of gasket
materials is presented in Table 5-24 of the Pe.trQ.1eum Processing Hand-
book (by W. F. Bland and R. 1. Davidson, McGraw-Hill, New York, 1957).
The Mark's Handbook (Mark's Standard Handbook for Mechanical Engineers,
Eighth Edition, McGraw-Hill, New York) presents a discussion of packings
and seals in Section 8 of the handbook.
B.4.2 Lining and Coating Materials
Tank deterioration, as a result of waste and tank material
incompatibility, may cause tank failure. In situations where the waste
is corrosive to the material of construction of the tank, some type of
protection may be required. Eitl.cr linings or coatino materials are
often used to protect the construction materials of a tank. The permit
writer snould review the waste type and tank materials of construction
to assure that the tank is protected against corrosion. Linings and
coatings are defined below:
• "Linings" are materials attached to the inner
shell of a tank. Common lining materials include glass,
rubber, plastic, lead, tar, and brick.
t "Coatings" are thin films of natural or synthetic
organic material, either- sprayed or brushed on the inside
surface of the tank to reduce internal/external
deterioration.
-------
8-16
Table 8-2. IMPORTANT PROPERTIES OF GASKET MATERIALS
RESERVED PENDING RECEIPT OF PERMISSION TO REPRODUCE.
TABLE 5-24 OF "PETROLEUM PROCESSING HANDBOOK".
-------
3-17
TABLE B-2. (CONTINUED)
RESERVED PENDING RECEIPT OF PERMISSION
TO REPRODUCE. TABLE 5-24 of "PETROLEUM
PROCESSING HANDBOOK".
-------
B-18
TABLE B-2 (CONTINUED)
RESERVED PENDING RECEIPT OF PERMISSION TO REPRODUCE.
TABLE 5-24 OF "PETROLEUM PROCESSING HANDBOOK".
-------
------- |