FACILITIES STORING OR TREATING HAZARDOUS WASTE IN TANKS
A Technial Resource Document for Permit Writers
This document (SV7-XXX) was prepared by Fred C. Hart Associates,
Inc., under contract to EPA's Office of Solid Waste and Theodore P.
Senger of the Technology Branch, Hazardous & Industrial Waste Division,
Office of Solid Waste.
This document has not been peer and administratively
reviewed within EPA and is for internal Agency use/
distribution only.
Au thoruTz ed s ig na trar e
U.S. Environmental Protection Agency / 198/2
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PREFACE
This is one of a series of technical resource documents that
provides information :on standards for facilities that treat, store,
or dispose of hazardous waste.
The documents are being developed to assist permit writers in
evaluating facilities against standards (40 Code of Federal Regu-
lations, Part 264) issued under Subtitle C of the Resource Conserva-
tion and Recovery Act (RCRA) of 1976, as amended. Included in these
documents is detailed information about design, equipment, and
specific procedures for evaluating data submitted by the permit
applicant, as well as bibliographies that can be used to locate
additional information.
The series, which is being produced by the Technology Branch
of EPA's Office of Solid Waste, includes guidance on:
0 containers
0 tanks
0 compatibility of wastes
0 incineration
Permit writers should keep in mind when using this material
that the regulations are subject to change through amendments
and modifications and should incorporate any changes into their
evaluations of facilities.
The' material contained herein is for; guidance purposes o.nly
and' is^not; enf.orc.eable.. ; The technical^ resource documents are not
toffee; ihterpret.eci .as amending the fac.il.i.ty standards in 40 CFR
Part 264.
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CONTENTS
PAGE
1. INTRODUCTION 1-1
A. Purpose 1—1
B. The Permit Process 1—1
C. Concept of Best Engineering Judgment 1—1
D. Regulations 1—2
E. Organization of the Manual 1—2
2. CHECKLIST AND QUESTIONS FOR THE PERMIT WRITER 2—1
A. Checklist for Permit Writer 2—1
B. Questions to Be Answered by the Permit Writer 2—4
3. TANK DESIGN 3—1
A. Introduction 3—2
B. Tank Design Considerations 3—2
C. Ancillary Design Features for Safe Operation 3—27
D. Process Flow and Instrumentation 3—32
4. INSPECTION 4—2
A. Evaluation of an Inspection Plan 4—2
B. Tank External Inspection——Tank in Service 4—5
C. Internal Inspection——Tank in Service 4—8
D. Inspection of Ancillary Equipment 4—9
E. Frequency of Inspection 4—11
F. Response. to Leaks and Spills 4—12
5. COMMON TREATMENT PROCESSES OCCURRING IN TANKS 5-i
A. Chemical Oxidation 5—3
B. Chemical Reduction 5—6
C. Neutralization 5—10
D. Precipitation, Flocculation, and Sedimentation 5—14
6. CLOSURE 6—1
A. Closure Requirement 6—1
B. Closure Plan Evaluation 6—1
7. HAZARDOUS WASTE TANK COSTS 7-1
APPENDICES A—i
A. Types of Tanks Used for Hazardous Waste Storage A—i
B. Subsurface and Foundation Construction B—i
C. Tank Ancillary Features C—i
D. Appurtenances and Safety Equipment D—1
E. Secondary Containment E—1
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TABLES
PAGE
3—1. Tank Selection Considerations 3—4
3—2. General Corrosion Properties of Some Metals
and Alloys 3-8
3—3. Properties and Chemical Resistance of Organic
Coatings 3—16
3—4. Chemical Resistance of Rubber 3—18
4—1. Tank Inspection Point Listing 4—3
4—2. Required Inspection Frequencies 4—11
4—3. Operational Problems of Tanks 4—13
5—1. Oxidation Waste Treatment Applications 5—5
5—2. Information for Estimating Performance against
Corrosion 5—7
5—3. Reduction Waste Treatment Applications 5—9
5—4. Major Industries Using Neutralization 5—11
7—1. Cost Data for Tanks by Type and Capacity (1979) 7—2
C—i. Pump Classes and Types C—2
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FIGURES
PAGE
3—1. Float—Activated Level Sensing Switch 3—30
3—2. Head Device for Liquid Level Measurement 3—31
3—3. A Simple Process Flow Diagram 3—33
3—4. A Simplified Piping and Instrumentation
Diagram 3—34
3—5. A Simple Tank Diagram. 3—35
3—6. A Typical Tank Data Sheet 3—36
7-1. Tank Cost Data by Type and Capacity 7—4
7—2. Fiberglass Tank Cast Data Capacity 7—5
7—3. StainlesS Steel Tank Cost Data by Capacity 7—6
1. Cone—Roof Tank A—2
2. Umbrella—Roof Tank A—2
3. Pan—type Floating Roof A—3
4. Pontoon—type Floating Roof A—4
5. Double—Deck Floating Roof A—5
6. Cross—Section Sketches A—6
7. Floating—Roof with Seal A—7
8. Lifter—Roof Tank A—8
9. Flexible—Diaphragm Tank A—9
10. Dry—Seal Lifter Roof A—il
ii. Wet—Seal Lifter Roof A—12
12. Plain Breather—Roof Tank A—13
13. Balloon—ROOf Tank A—13
14. Horizontal Tank (Riveted) A—14
15. Horizontal Tank (Welded) A—14
16. Plain Hemispheroids A— 15
17. Drawings of HemispheroidS A—iS
18. Plain Spheroidal Tank A—16
19. Noded Spheriodal Tank A—16
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CHAPTER 1
INTRODUCTION
A. PURPOSE
The purpose of this manual is to provide guidance for permit
writers in the implementation of Part 264, Subpart 3, of the 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 purposes only and is not meant to replace
data and information that are specific to the facility being
assessed.
B. THE PERMIT PROCESS
EPA ’s regulations provide for issuing hazardous waste facility
permits in two phases: Part A of the permit application (interim
status) and Part B of the permit application (permanent status——the
final permit). Interim status allows facilities that are in exis-
tence to continue operations while administrative action on the
final permit is under way. These facilities must submit Part B of
the permit application upon request by EPA. New facilities must
submit Part B of the permit application 180 days prior to beginning
physical construction.
Part B of the permit application must contain information
on the equipment, structures, and procedures used for managing
hazardous waste at the facility. The application must also
provide data on the physical and chemical characteristics of the
wastes to be handled (40 CFR §122.25).
The permit writer evaluates the information provided in
Parts A and B of the application to determine whether the facility
meets the administrative technical standards (40 CFR 264) and the
procedural requirements for obtaining a permit (40 CFR 122 and 124).
To assist the permit writer, the Permit Guidance Manuals provide
background information and procedures for evaluating the data
provided by the applicant.
The RCRA administrative procedi’res permit manual (SW—934) pro-
vides guidance to permit writers on procedures to follow from the
point of initial contact with an applicant through review, public
hearings, and any administrative appeals of permit decisions. The
manual also contains guidance for conducting technical reviews.
C. CONCEPT OF BEST ENGINEERING JUDGMENT (BEJ)
Various sections of the final regulation for tank treatment
and storage require the use of best engineering judgment (BEJ).
This concept entails the application of a case—by- -case judgment,
based on site—specific circumstances, to facilities attempting to
meet permit requirements. In those sections of the regulations
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.hat have been written based on BEJ, some flexibility is provided
.n developing permit requirements. The Agency feels that the
evaluation of facilities on an individual basis will provide the
jreatest protection to truman health arid the environment and at
:he same time avoid overly restrictive requirements.
BEJ provides for tailoring permit requirements to the specific
astes and the design and environmental conditions of each facility
Dased on the best engineering judgment of the permit writer. In
Drder to make these judgments, the permit writer must have access
to information on current technology and be provided with facility
and site—specific data.
D. REGULATIONS
Section 3004 of RCRA directs EPA to develop standards for
owners and operators of hazardous waste treatment, storage, arid
disposal facilities. Under this directive EPA promulgated regu-
lations for the treatment and storage of hazardous waste in tanks
(40 CFR 264). Tanks are defined in 40 CFR 260 (45 Fed. Reg. 33076
[ May 19, 19801) to be a TM stationary device, designed to contain
an accumulation of hazardous waste which is constructed primarily
of non—earthen materials...wh.ich provide structural support.”
This manual discusses the regulations pertaining to treat-
ment and storage of hazardous wastes in tanks (40 CFR, Part 264
Subpart 3). The following areas are covered:
design of tanks (S264.191)
— general operating requirements (S264.192)
— inspections (S264.194)
— closure (S264.197)
— special requirements for ignitable or reactive
wastes (S264.198)
— special requirements for incompatible wastes (S264.199)
E. ORGANIZATION OF THE MANUAL
Chapter 1 provides an overview of the manual. It outlines
the areas that the RCRA hazardous waste tank regulation covers
and describes the content of bach chapter.
Chapter 2 is comprised of questions that are directly related
to the regulations. These questions are designed to serve as a
checklist for a permit writer during the evaluation of a permit
application. Answers to the questions will facilitate the decision—
making process of whether or not an applicant will be able to
comply with the RCRA regulations.
Chapter 3 presents a discussion of the factors thatinfluence
tank design and selection. Structural integrity and compatibility
are discussed as they relate to the expected service life of the
tank. The importance of pressure upon the tank structures is
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presented. Corrosion rate, corrosion allowances, and lining and
coatings as a protection against corrosion are examined. Design
features necessary for safe operation of a tank facility conclude
the chapter.
Chapter 4 includes external and internal visual inspection
points where a tank and its auxiliary equipment should be inspected.
Techniques used to perform inspections are listed, and the rationale
for determining inspection frequencies is outlined.
Chapter 5 addresses possible interactions of tank materials
and wastes or treatment reagents (or processes). Five common
treatment processes are described with emphasis upon the inter-
actions of the treatment processes and the tank materials. The
treatment processes are: (1) chemical oxidation, (2) chemjcal
reduction, (3) neutralization, (4) precipitation, and (5) sedi-
mentation.
Chapter 6 addresses the evaluation of a tank closure plan.
Disposal procedures for onsite waste and waste residues are
described, followed by decontamination procedures.
Chapter 7 discusses basic materials and costs, operating
and maintenance costs, and capital costs of constructing and
operating a tank facility.
The appendices provide general information on tank storage
facilities.
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CHAPTER 2
CHECKLIST AND QUESTIONS TO BE ASKED BY PERMIT WRITERS
A. CHECKLIST FOR PERMIT WRITERS
This section provides the permit writer with a checklist
for evaiuatiflg an application from an owner or operator of a
hazardous waste facility utilizing tanks for storage or treat-
ment. The checklist can be used to determine the completeness
and adequacy of the permit application.
1. General Facility Description
o number of tanks
o location of tanks
o buffer zones around tanks
(Note: §264.198 requires compliance with
National Fire Protection Association’s buffer
zone requirements)
2. Chemical and Physical Analyses of Wastes
O information necessary to determine waste—to—waste
compatibility, waste—to—tank compatibility, and
ignitability or reactivity
3. Waste Analysis Plan
o analyses used to determine characteristics and properties
of the waste to be stored or treated
o analyses needed for compliance with requirements for
ignitable, reactive, or incompatible wastes
o methods to obtain representative samples of waste
o frequency with which original analysis will be reviewed
or repeated
0 source of other information on properties or charac-
teristics of waste for offsite facilities
procedures to be used’to inspect each shipment of waste
received at the facility
4. Description of Security
5. Inspection Schedule
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o schedule for inspection of monitoring equipment, safety
and emergency equipment, and security devices, specified
in SS264.15 and 264.194(a)
o schedule for comprehensive inspections and assessments
of the condition of the tanks required in §264.194(b)
o list of items to be covered during routine external
inspection (e.g., cracks, leaks, corrosion, erosion
of foundation or tank sides or bottoms, deterioration
of foundation seal, corrosion or discoloration of tank
exterior, etc.)
o procedures for comprehensive inspections required in
S264.194(b)
— procedures for inspecting internal surfaces
— safety procedures for protecting inspector
6. Justification for Waiver of Preparedness and Prevention
Requirements
7. Contingency Plan
o actions to be taken in response to fires, explosions,
or unplanned releases of hazardous waste, including
procedures and timing for removal of waste and repair
of tank as required by S264.194(c).
o arrangements with police department, fire department,
hospitals, contractors, and State and local emergency
response teams
o list of emergency coordinators at the facility
o list and location of emergency equipment
o evacuation plan, if necessary
8. Descr.ption of Procedures to:
o prevent hazards in unloading
o prevent runoff from handling areas
o prevent contamination of water supplies
o mitigate effects of equipment failure and power outages
o prevent exposure of personnel to hazardous waste
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9. Incompatible, Ignitable, and Reactive Wastes
o procedur es for treating waste prior to placement in
tank, where applicable
o procedures used to prevent a waste from being placed in
an unwashed tank that previously held an incompatible
waste
O procedures used to prevent incompatible wastes from being
placed in the same tank
o documentation of precautions to prevent accidental igni-
tion or reaction (S264.198(a))
documentation of compliance with NFPA buffer zone require-
ments (S264.198(b))
O for offsite facilities, procedures for inspecting each
shipment of waste received (part of the waste analysis
plan)
10. Traffic Pattern and Volume
11. Facility Location
O political jurisdiction in which facility is located
o if facility is in an area listed in Appendix VI of
Part 264, demonstration of compliance with the seismic
standard (see §5264.18(a) and 122.25(a)(ll)(ii) for
details)
o identification of whether facility is located in a
100—year floodplain
O if facility is in a 100—year floodplain, engineering
analyses showing design of operational units and flood
protection devices and their ability to withstand
forces of a 100—year flood, or procedures for removing
hazardous waste prior to a flood (see SS264.18(b) and
122.25(a)(1l)(iv) for details)
if existing facility is not in compliance with §264.18(b) ,
a plan and schedule for bringing facility into compliance
12. Outline of Training Programs
13. Closure Plan (see S264.122)
14. Closure Cost Estimate and Financial Assurance Mechanism
(5264.142 and 264.143)
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15. Documentation of Compliance with Liability Requirements,
if applicable (S264.147)
16. Proof of Coverage by State Financial Mechanism, Where Appro-
priate (SS264.149 or 264.150)
17. Topographic Map (S122.25(a)(19))
18. Design Information for Each Tank:
o design standard and other engineering information used
in design; construction
0 identification of and specifications for construction
materials and lining materials including information
on corrosion resistance
° tank dimensions, capacity, and shell thickness
0 description of feed, cutoff, and bypass systems and
pressure controls
— description of devices for measuring liquid level
of flow rate
— description of overfilling controls (e.g., alarm
or cutoff)
— design standard or other information used in design
of pressure controls •(e.g., vents)
B. QUESTIONS TO BE ANSWERED BY PERMIT WRITERS
The following questions can be used by the permit writer in
in evaluating the information in the permit application and pre-
paring a facility permit.
1. Tank Design
a. Do nonearthen materials provide the structural support
(is it a tank?)?
b. What is the minimum required thickness of the tank
walls based on the design standard or other engineering
information?
c. Is sufficient vapor space provided to allow vapors to
expand when the ambient temperature rises?
d. Are adequate vents provided for pressure relief to
atmosphere or vapor recovery system?
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2. Compatibility of Waste with Tank
a. Does the waste analysis plan specify adequate procedures
for determining whether the waste is compatible with
the tank construction materials or lining materials?
b. Are the tank construction materials or lining materials
compatible with the waste stored?
c. Are corrosion inhibitors or cathodic protection used to
protect the tank material against attack?
d. Are the assumed corrosion rates of the material of con-
struction of the tank based on published literature or
submitted data?
e. Based on the estimated corrosion rate and present thick-
ness Of the tank, what is the expected service life of
the tank?
3. Overfilling Controls
a. Is the tank equipped with adequate controls to prevent
overfilling (e.g., high—level alarms, automatic feed
cutoff system, by—pass system to a stand—by tank, etc.)?
4. Inspection
a. Does the inspection schedule include the components
required by §264.194(c)?
b. Are the procedures for the comprehensive inspections
required by §264.194(b) adequate to detect cracks,
leaks, corrosion, and wall thinning.
c. Are adequate procedures specified for protecting the
inspector while inside the tank (if appropriate)?
d. Is the frequency o inspections based on the estimated
corrosion rate and service life of.. the tank?
e. Are procedures for responding to spills and repairing
the tank specified in the contingency plan?—
5. Closure
a. What are the expected general conditions of the tank
at closure?
o types of wastes stored
o maximum inventory
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b. What are the schedule and estimated cost of closure
activities?
c. How will the wastes be removed from the tanks?
d. Will he the wastes be treated, stored, or disposed of
onsite or offsite?
e. How will the tank and associated equipment be decon—
tami nated?
f. How will contaminated soils, cleaning products, and
residues be disposed of?
6. Ignitable, Reactive, and Incompatible Wastes
a. Do the procedures for management of ignitable, reactive,
and incompatible wastes satisfy the requirements of
5S264.17, 264.36, 264.198, and 264.199? (See checklist
item 19.)
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CHAPTER 3
TANK DESIGN
Chapter Outline
A. Introduction
B. Tank Design Considerations
1. Internal Pressure and Pressure Controls
a. Pressure
b. Venting
2. Minimum Wall Thickness and Compatability of Construction
Materials with Waste
a. Construction Materials
b. tlimimum Thickness and Corrosion Allowances
c. Expected Service Life
d. Examples
e. Decision Process
C. Ancillary Design Features Necessary for Safe Operations
1. Measurement Devices
2. Overfilling Control Systems
D. Diagrams of Process Flow and Instrumentation
1. Process Flow Diagrams
2. Piping and Instrumentation Diagrams
3. Plot Plans
4. Tank Diagrams and Data Sheets
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CHAPTER 3
A. INTRODUCTION
The RCRA Subtitle C regulations define a tank as a “stationary
device, designed to contain an accumulation of hazardous waste
which is constructed primarily of non—earthen materials (e.g.,
wood, concrete, steel, plastic) which provide structur 1 support.”
Liquid and semiliquid hazardous wastes are often stored or treated
in tanks, of which there is a variety of types and sizes.
Factors t:o consider when evaluating tank design include:
Tank Desrgn Basis
o design standards used
o other engineering information
Compatibility of Waste with Tank or Lining
o composition of waste
o construction materials of the tank
o corrosion rate of waste with respect to construction
material
o expected service life of tank
Operating Conditions
o pressure exerted on walls of tank
o temperature
Other Factors
o climate
o corrosivity of surrounding soil
These factors (with the exception of climate and soils) are
Hscussed in the remainder of the chapter.
3. TANK DESIGN CONSIDERATIONS
The three major considerations in designing a tank to store
particular hazardous waste are:
o internal vapor pressure
o stress caused oy weight of contents
O compatibility of construction material with the waste
stored
Internal pressure is discussed in the following section. A dis—
!ussion of strength and of compatibility of the tank with the wastes
;tored is presented later in this chapter. Additional information on
ompatabilities between waste and structural materials is contained
.n the technical resàurce document on waste compatibility. 2
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1. Internal Pressure and Pressure Controls
a. Pressure . Pressure imbalances affect the safe opera-
tion of a storage tank and, in extreme cases, can result in
instantaneous tank rupture. The petroleum and nemical industries
have historically based the primary selection of storage tanks on
design pressures. Currently, there are well—accepted industrial
design standards and codes for storing different types of liquids.
Among the most common are the following:
0 the design of welded steel tanks up to 2.5 pounds per
square inch gauge (psig) internal pressure is covered
by the American Petroleum Institute (API) standard 620k
0 the design of large welded, low—pressure storage tanks
up to 15 psig is covered by API standard 620
0 the design of water storage reservoirs, steel tanks,
and elevated tanks is coyered by the American Water
Works Association (AWWA) Code D100 5
0 the design of tanks with internal pressures above 15
psig and below 0 psig (vacuum tanks) is covered by the
American Society of Mechanical Engineers (ASME) pressure
vessel code 6
o tank design for flaziimable and combustible liquid
storage is covered by the National ire Protection
• Association (NFPA), Pamphlet No. 30’
0 the design of steel above—ground tanks for flammable
and combustible liquids is covered by Underwriters’
Laboratories, Inc., Subject No. 1428
0 the design of open concrete tanks is covered by American
Concrete Institute Publication ACI—350—R—77 9
The American Petroleum Institute classifies tanks into three
major divisions based on pressure. “Atmospheric tanks” are de-
signed to contain pressures up to 2.5 psig and are structurally
different from “low—pressure tanks” designed to withstand up to
15 psig. “High—pressure tanks” are designed to withsta 1 d pres-
sures greater than 15 psig.
o Liquid hazardous wastes are most commonly stored in
covere atmospheric or low—pressure, above—ground
tanks. High—pressure, vacuum, and unde ground tanks
are not covered in detail in this chapter. Table 3—1
lists the most commonly used types of tanks and selec-
tion considerations pertinent to each type of tank.
Appendix A presents descriptions of the tanks listed
in Table 3—1.
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Type of Tank
I. Atmospheric,
Above—ground,
Covered Tanks
a) Plain cylindrical
II. Low—Pressure,
Above—ground,
Covered Tanks
a) Hemispheroidal
b) Spheroidal
c) Noded—spheroidal
til. Underground Tanks
TABLE 3—1
TANK SELECTION CONSIDERATIONS
* Source:
Fred C.
Hart Associates, Inc.
Other Considerations
b) Fixed—roof
c) Variable vapor—
space
d) Breather roof
e) Floating roof
f) Covered floating
roof
Press ur e
0 to 2.5 pounds
per square inch
gauge (psig)
Up to 15 psig
Generally 0 psig
Atmospheric pres-
sure (() psig)
Nominal vapor pressure
fluctuations, small
volume
Nominal vapor pressure
fluctuations
Moderate vapor pressure
fluctuations
Moderate vapor pressure
fluctuations
Significant vapor
pressure fluctuations
Significant vapor
pressure fluctuations
plus heavy rainfalls
or snowf ails
Small—to—medium volumes
Large volumes
Very large volumes
Smal volume, aesthetics,
safety
Not currently allowed
at permitted treatment
or storage facilities
No volatile pollutants
IV. Uncovered Tanks
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On the basis of the pressure criterion, an owner or operator
can select an atmospheric, above—ground, covered tank to store
most hazardous wastes. Hazardous wastes that are highly volatile
and capable of exerting pressure higher than 2.5 psig should be
stored in low—pressure tanks.
The following general guidelines will aid in evaluating the
proper selection of tanks to store hazardous waste based on a
pressure criterion:
0 Pressurized tanks are used to store hazardous wastes
that have toxic vapors. If the waste is nonvolatile
or the vapors nonpolluting, atmospheric tanks can be
used to store hazardous wastes.
o Storage of liquid hazardous waste seldom requires the
utilization of high—pressure tanks (above 15 psig)
or tanks operating under vacuum.
0 Uncovered tanks are not recon mended for storage of
hazardous wastes unless the wastes are nonvolatile.
o Wastes with low boiling points (such as heavy metal—
laden pentane, which has a boiling point of 37°C)
tend to vaporize easily and exert higher vapor pres-
sure. If the vapor pressure of the waste is above
2.5 psig, the waste should be stored in low—pressure
tanks.
0 Vapor pressure of the waste at maximum ambient tempera-
ture must be known. The permit writer can then deter-
mine whether or not the tank is selected properly on
the basis of pressure.
b. Venting . Vents for tanks perform two general functions:
° Allow air, inert gas, or other blanket gas into the tank
or allow vapor to escape from the tank. In this manner
the vapor pressure of the tank will be maintained either
under atmospheric pressure or within the pressure limi-
tation of the tank design to preclude rupture or collapse
of the tank.
Serve as a discharge point to allow the collection of
either undesirable vapor emissions (i.e., hazardous
pollutants or other air pollutants) or vapors that
can be recovered and sold as a commercial product
(e.g., methane).
Venting designs of a tank facility are determined by the
types of wastes handled, pumping requirements, etc. Venting
designs include:
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(1) Maintaining Atmospheric or Design Pressure. Maintaining
internal t-ank pressure either equal to outside atmospheric pressure
or within the desi.red pressure of the tank is critical to the safe
operation of a tank facility. When liquid is drained out of the
bottom of a tank, a vacuum may be created in the space left above
the remaining liquid. This may cause the collapse of the tank
owing to the pressure differential. Vents must be designed to
allow air or other gas into the tank as liquid is removed. This
maintains the internal pressure of the tank. Vent sizes should
be determined according to industrial standards such as APE
standard 2000.10
Vents also serve to release vapor from a tank when it is
being filled. Vents open to the ambient air are usually used for
tanks containing wastes whose vapors are not considered to be
toxic or highly flammable. Control of air emissions from hazardous
waste tanks will be addressed in future regulations and guidance.
(2) Venting/Vapor Recovery Systems. Vapor recovery systems
have sophisticated pressure sensing and pressure control instru—
mentation that maintains vapor pressure equilibrium during all
periods of tank operation. Vapor recovery systems consist of
a system to collect the vapors frequently followed by a treatment
process that either renders the vapor harmless for venting to the
atmosphere or converts it to a product that has market value.
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 recovery units are used: 1) individual units for each
tank; and 2) commonvapor recovery units for a system of two or
more tanks that are being used to store wastes with similar
vapor chemical compositions.
The following items should be considered when evaluating
venting/vapor recovery systems:
O When more than one type of waste is handled, their
compatibility must be determined. When the wastes
are incompatible, their vapors may also be incom-
patible. Separate vapor recovery units would be
appropriate. —
o Vapor recovery systems must be maintained at airtight
conditions to preclude leakage.
The control instrumentation should be adequately
monitored and maintained on an appropriate schedule.
o The vapor recovery pipes should be sloped down to
a comuon place where condensation can be collected.
In addition, the vapor flow linear velocity must be
maintained under design limitations to preclude
excessive turbulence, vibration, etc.
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The permit writer should review the process flow diagram
(i.e., a diagram that depicts the direction and volume of vapor
and fluid movements) to evaluate factors such as the following:
o Is there a vapor recovery system or other method of
recovery to accommodate incompatible wastes? (Incom-
patible wastes should not utilize a common vapor
recovery system.)
0 If incompatible wastes are going to be handled, are
there separate piping systems?
2. Minimal Wall Thickness and Compatibility of Construction
Materials with Waste
The walls (or shell) of the tank must be of sufficient thick-
ness and strength to withstand the stresses caused by the weight
of the tank contents. Because corrosion reduces the thickness
of the tank shell, maintaining sufficient thickness and strength
necessitates consideration of the compatibility between the con-
tained waste and the tank construction material. This section
discusses the compatibility of tank construction materials and
wastes, minimum tank shell thickness and corrosion allowances,
and the expected service life of a tank based on estimated
corrosion rates.
a. Construction Material . Materials used for tank con-
struction include steel, concrete, plastic, and wood. Most
tanks currently in use are made of carbon steel and alloy steel.
Plastic and wood tanks are not discussed in this section. 11
(1) Steel Used in Tanks. Some of the features of carbon
and alloy steels are listed below. Table 3—2 summarizes the
general corrosion properties of a wide range of metals and alloys.
(a) Carbon steels
o most commonly used steel in the petroleum
and chemical industries
° can be usec.. to store alkalies; for example,
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 sea water
° commonly used to store organic solvents and
similar chemicals
3—7
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O.,s,.I C.u . I.s, Pop.e$l.s .4 kits. Uslals ond Allsyi’
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TABLE 3-2
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limited corrosion resistance to certain wastes;
therefore, extra thickness for corrosion
allowances is often needed beyond the minimum
thickness required for structural integrity
when no lining or coating is used
° should not be used on contact with hydro—
chioric, phosphoric, or nitric acid
(b) Alloy 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:
0 austenitic steel
— is the most highly resistantof stainless steels
to many acids, including hot or cold nitric acid
— retains strength at temperatures as low as liquid
helium
— responds well to severe stress at elevated
temperatures
0 martensitic steel
— is less corrosion resistant than austenitic steel
— used for mildly corrosive environments such as
organic exposures
0 ferritic steel
— has good corrosion resi \stance
(2) Concrete. This material is predominantly used in large
open tanks and treatment basins. Several characteristics of con-
crete are listed below:
° susceptible to freeze—thaw cracking and deterioration
if not properly air entrained
• subject to attack by copper and ferric sulfates if not
made with sulfate—resistant cement
0 subject to attack by certain chemicals including alum,
chlorine, ferric chloride, sodium bisulfite, sulfuric
• acid, and sodium hydroxide (<20 percent).
3—12
-------
The permit writer must ascertain the effect of the waste
proposed for storage upon the tank construction materials and
the liner materials (if present). For further discussion of
compatibility between the waste proposed for storage and the
tank materials, refer to:
o Compatibility of Wastes in Hazardous Waste Management
Facilitites: A Technical Resource Document. 2
o manufacturers’ literature regarding chemical and
physical properties of tank and liner materials
o Perry’s Chemical Engineers’ Handbook , which contains
specific sections on corrosion 11
o literature published by the National Association of
Corrosion Engineers in Houston, Texas 12 ’ 13
o information published by the American Concrete Insti-
tute 14
(3) Lining and Coating Material. 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. Both linings and coating materials are often used
to protect the construction materials of a tank. The permit writer
should review the waste type and tank materials of construction
to assure that the tank is protected against corrosion. Linings
and coatings are defined below.
o “Linings” are sheet materials attached to the inner
shell of a tank. Common lining materials include
rubber, plastic, tar, lead, and brick.
o “Coatings” are thin films and natural or synthetic
organic material, either sprayed or brushed on the
inside surface of the tank to reduce internal/external
deterioration.
The following discussion presents the more common lining and
coating materials. (Refer to the National Association of Corrosion
Engineers for further information.’ 3 )
(a) Plastics.’ 1 In general, plastics have the following
characteristics:
o have excellent resistance to weak mineral acids
and inorganic salt solutions
O have good electrical and thermal insulators
3—13
-------
o do not corrode from chemical reactions
o do not react to small changes in pH, minor
impurities, or oxygen content
The most widely used plastics for coating and lining materials
include: polyethylene, chlorinated polyether, cellulose acetate
butyrate, polyamide, polypropylene, polyester resin, and epoxy.
o Polyethylene is the least costly plastic that is
commercially available. The carbon—filled grades
are resistant to sunlight and weathering.
O Chlorinated polyether (Penton) can withstand
temperatures up to 255°F. It is not affected by
dilute acids, alkalies, or salts. However, nitric
acid over 25 percent in concentration, aromatics,
and ketones cause degradation.
O Cellulose acetate butyrate is affected by chlorinated
solvents, but not by dilute acids or alkalies.
° 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
with fiberglass, have good strength and good chemi-
cal resistance, except to alkalies. Polyesters
containing bisphenol are more alkali resistant.
The temperature limit for using polyesters is
about 200°F.
° Epoxy has good chemical resistance to nonoxidizing
and weak acids. It is also resistant to weak
alkaline solutions.
(b) Rubber. 11 Rubber and elastomers are creqjently
used as coating and lining materials. In addition to natural
rubber, a number of synthetic rubbers have been de”eloped. While
none have all the properties of natural rubber, some are superior
for specific uses.
Natural rubber is resistant to dilute mineral acids, a’tkalies,
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 synthetic rubber, thus making it both hard and strong.
3—14
-------
o Chioroprene or neoprene rubber is resistant to
atback by ozone, sunlight, oils, gasoline, and
aromatic or halogenated solvents.
o Styrene rubber has chemical resistance similar to
natural rubber.
o Nitrile rubber is resistant to oils and solverts.
0 Butyl rubber’s resistance to dilute mineral acids
and alkalies is exceptional; its resistance to
concentrated acids, except nitric and sulfurio,
is good.
0 Silicone rubbers, also known as polysioxanes, have
outstanding resistance to high and low temperatures
and to aliphatic solvents, oils, and greases.
0 Chiorosulfonated polyethylene, known as hypalon,
has outstanding resistance to most ozone and oxi-
dizing agents except fuming nitric and sulfuric
acids. Its oil resistance is good.
0 Fluroelastomer (Viton A, Kel—F) combines excellent
chemical and high—temperature resistance.
0 Polyvinyl chloride elastaner (Koroseal) was developed
to overcome some of the limitations of natural and
synthetic rubbers. It has excellent resistance to
mineral acids and petroleum oils.
• The cis—polybutadiene and cis—polyisoprene rubbers
are almost duplicates of natural rubber.
0 The newer ethylene—propylene rubbers have excellent
resistance to heat and oxidation.
Table 3—3 lists the properties and chemical resistance of
many organic coatings; Table 3—4 sui unarizes the chemical resistance
of rubber materials. Compatibility evaluation may be made based
on information in these tables.
(C) Gaskets. Gaskets serve as fiilers in static
clearances that usually occur at concentric cylinders. Sealing
is achieved by subjecting effective compression through bolts or
other mechanical means. Improper gasket installation can easily
result in a leak. Therefore, extra care should be given to select
the proper type of gasket as well as the proper material of con-
struction and to ensure quality control during inst2llation.
The most common types of gaskets are cylindrical or con-
centric, o—ring joints, and valve seats. Gasket selection should
be based on site—specific objectives. During installation, care
3—15
-------
TM1 E .3—3
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&CY; £ caccllrøt ; VC — vesy good; C u good; F lair; P poor.
tT ,so caSIngs are to, dilute (20%) and euncenirated. respectively.
‘Ticics r eilsigs sic (or dilute ( (0%). niedlwn (10—30%). and concentrated. respectively.
1 T 4 (‘.1i 1 1) wheil.
• Nut iccusnaueasktl with nitric
a. wjfls elcesug cyclic ekl ‘olsulions.
Source :
Chemical Engineers’ Handbook , 5th ed., Robert H. Perry and Cecil H.
Chilton (New York; McGraw—Hill, 1973). Used by permission of McGraw—
Hill. Book Company.
-------
TABLE 3—3
Source : Perry and. Chilton, Ed., Chem1ca Ençi lneers’ Handbook ,
5th Ed., McGraw-Hill Co., New York, 1973.
-------
TABLE 3-4
CHEMICAL RESISTANCE OF RUBBER MATERIALS
Type of Rubber Features
Butad ene—styrene . General-purpose; poor resistance to hydro-
carbons, oils, and oxidizing agents
Butyl . . . . . . General-purpose; relatively impermeable to
air; poor- resistance to hydrocarbons and oils
Chioroprene . . . . . . Good resistance to aliphatic solvents; poor
resistance to aromatic hydrocarbons and many
fuels
Chiorosul fonated Excel lent resi stance to oxidation, chemicals,
polyethylene . . . . and heat; poor resistance to aromatic oils
and most fuels a
cis—Polybutadiene . General-purpose; poor resistance to hydro-
carbons, oils, and oxidizing agents
cis—Polyisoprene . . . General-purpose; poor resistance to hydro-
carbons, oils, and oxidizing agents
Ethylene—propylene . . Excellent resistance to heat and oxidation
Fluorinated . . . . . .. Excellent resistance to high tempera.ture, oxi—
diving acids, and oxidation; good resistance
to fuels containing up t 30% aromatics
Natural . . . . . . . . General-purpose; poor rE.:istance to hydro-
carbons, oils, and oxidi.ing agents
Nitrile (butadiene— Excellent resistance to us, but not resistant
acrylonitrile) . . . to strong oxidizing agents; resistance to oils
is proportional to the acrylonitrile content
Polysulfide Good resistance to aromatic solvents; unusually
high impermeability to gases; poor compression
set and poor resistance to oxidizing acids
Silicone . Excellent resistance over unusually wide temp-
erature range (—150 to +500°F.); fair oil re—
sistance; poor resistance to aromatic oils,
fuels, high—pressure steam, and abrasion
Styrene . . . . . . . . Synonymous with butadiene—styrerte
Source : Chemical Engineers’ Handbook, 5th ed., Robert H.
Perry and Cecil H. Chilton (New York: McGraw—Hill,
1973). Used by permission of McGraw—Hill Book
Company.
-------
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 a re—
suit of incompatibility between hazardous materials 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’ recom-
mendations for installation as well as maintenance be followed.
In some cases, if deterioration is detected, the gasket should be
immediately replaced. 15
(d) Selection. Whether to use a liner or coating
material or utilize extra metal thickness to provide for tank
corrosion allowance is an engineering decision. 16 Factors to
consider include:
o type of waste stored
o construction material used for structural sup ört
O availability of material
o ease of application
b. Minimum Thickness and Corrosion Allowances . The fol-
lowing section considers minimum wall thickness and corrosion
allowance as they interact with the expected service life of a
tank.
All tanks must have a minimum wall thickness to provide
structural integrity and thus prevent the collapse of the tank.
Design standards for tanks specify a minimum thickness for the
tank shell. The specified minimum thickness includes a small
allowance for corrosion and 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 difference between the actual thickness of the tank wall
and the minimum required thickness (as specified in the design
standard of the facility’s permit) is frequently referred to as
the corrosion allowance.
(1) Minimum Wall Thickness. Minimum wall thickness is
specified in the design standard or the facility’s permit. The
Itinimum wall thickness is normally slightly greater than neces—
sary to provide structural support under normal conditions and
to allow for small amounts of corrosion Or erosion or extraor—
3 ir ary stresses. Since pressures on the tank wall are greater
t the bottom, different thicknesses might be specified for upper
nd lower portions of the tank shell. Inspection procedures for
neasuring wall thickness are required by the regulations.
3—19
-------
Minimum thickness is normally calculated on the basis of
a formula specified by each standard code. The components of
the formula include: specific gravity of contents, height of
liquid in tank, and diameter of tank.
The following are commonly used design and construction
codes for tanks.*
Atmospheric Pressure Tanks
o Underwriters’ Laboratories, Inc., No. 142,8 Standard
for Steel Aboveground Tanks for Flammable and Com-
bustible Liquids, 1972
o Underwriters’ Laboratories, Inc., No. 58, Standard for
Steel Underground Tanks for Flammable and Combustible
Liquids, Fifth Edition, December 1961
o American Petroleum Institute (API) Standard No. 12A,
Specification for Oil Storage Tanks with Riveted
Shells, Seventh Edition, September 1951;
o API Standard No. 12B, Specification for Bolted Produc-
tion Tanks Eleventh Edition, May 1958, and Supplement
1, March 1962
0 API Standard No. 12D, Specification for Large Welded
Production Tanks, Fifth Edition, March 1961
0 API Standard No. 650 Welded Steel Tanks for Oil Storage,
Sixth Edition, 1979
Low—Pressure Tanks
° API Standard No. 62O, Recommended Rules for the Design
and Construction of Large, Welded, Low—Pressure Storage
Tanks, Fifth Edition, 1973
* When tanks are not designed in accordance with American Petro-
leum Institute, American Society of Mechanical Engineers,
Underwriters’ Laboratories, or American Concrete Institute
standards, the stress on the tank must be calculated directly
and a margin of safety allowed in establishing minimum thick-
ness. If significant corrosion is anticipated, additional
thickness of the metal or suitable protective coatings or
linings should be provided to compensate for the loss from
corrosion expected during the life of the tank.
3—20
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O Code for Unfired Pressure Vessels, Section VIII of the
American Society of Mechanical Engineers (ASME) Boiler
and Pressure Vessels Code, 6 1974
High—Pressure Tanks
0 Section VIII of the ASME Boiler and Pressure Vessels
Code, 6 1974
Concrete Tanks
0 American Concrete Institute, publication ACI—350R—77,
Concrete Sanitary Engineering Structures 9
Fiberglass Tanks
0 Section X of the ASME Boiler and Pressure Vessels Code,
1974
(2) Corrosion Allowance. Corrosion alowance 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.
Actual thickness of tank walls varies. A pit or very small cor-
roded area does nbt weaken the shell plate appreciably from the
standpoint of resisting pressure. A good rule to follow in
establishing a plate thickness for a corroded area** is that the
average thickness over a distance in longitudinal direction is
equal to 16 times the minimum allowable thickness. This average
should be used for comparison with the minimum thickness. Because
corrosion is a continuous process, the corrosion allowance dimin-
ishes over time.
C. 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 thick-
ness 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.
* Measures of wall thickness should be exclusive of the
thickness of any coatings or linings applied to the tank
walls. However, use of coatings or linings to protect
and maintain wall thickness is encouraged in many cases.
** From American Petroleum Institute, Guide for Inspection
of Refinery Equipment, Chapter XIII, 3rd Edition, p.43.
Use of alternative methods for measuring shell thickness
should be justified by the permit applicant.
3—21
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Since hazardou s wastes are usually mixtures of chemicals,
the corrosion rates of materials exposed to them might not be
absolutely known. The National Association of Corrosion Engineers
(NACE) 12 ’ 13 and Perry 11 have published data on corrosion rates
for different materials. Representative tables and a discussion
of their use are contained in the permit writers’ guide on hazard-
ous waste compatibility. 2 These tables can be used to estimate
the corrosion rates of materials if the chemicals stored have
similar properties. If the properties of the major component of
the hazardous waste can be assumed to have dominating influence
on the properties of the waste, the corrosion rate may also be
assumed (conservatively) to be the :same as that for the pure
chemical. The actual corrosion rate must be measured thereafter
through periodic inspection. (Caution should be exercised in
relying upon published corrosion rates since such factors as the
oxygen and water content and the chlorine content and temperature
of the waste can significantly affect the corrosion rate causing
substantial variation from the published value.)
If a particular waste and the construction materials of the
tank are incompatible (very high corrosion rate), the tank should
not be used to store that waste.
In order to estimate the expected service life of a tank,
the permit writer should determine:
o the standard code used for building the tank;
o the materials used for construction and their properties;
o the required minimum thickness of the shell plates of
a tank, which is a function of the contained liquid’s
specific gravity, height of liquid level, and diameter
of the tank;
O the corrosion allowance;
o the presumed initial corrosion rate or the actual
corrosion rate based on periodic measurements.
d. Examples . Three examples have been developed to illu—
trate 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 determind. Various
interactIons (trade—of fs) among minimum required thickness, cor-
rosion allowance, and expected life are also presented.
(1) Example 1 . A vertical, cylindrical, welded carbon
steel tank built in 1974 and used for the storage of oil is to
be converted to store hazardous waste at a maximum design pres—
Sure equal to 0 psig (atmospheric pressure) and at ambient
3—22
-------
temperature. The tank, which has 72—inch butt—welded courses,
was built in accor.dance 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 thick-
ness 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 minimum thickness of
the tank’s walls to preclude excessive stresses:
t = ( 2.6) (D) (H’-l) (G )
(‘0.85) (21000)
t = minimum tall thickness, in inches
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
= specific gravity of liquid to be
stored, but in no case less than 1.0
0.85 joint efficiency fa ctor
21000 = maximum allowable tensile strength
for applying the factor for efficiency
of joint
t = ( 2.6) (60) (30—1) (1.0 )
(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 prLsented 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).
3—23
-------
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 allow-
ance to prolong the Service life of the tank. Since the specific
gravity of the waste will place greater stress on the tank’s
walls, the maximum height allowed for storing the waste is cal-
culated to be:
0.2.5 = ( 2.6) (60) (H—i) (1.2 )
(0.85) (21000)
H = 24 feet (approx.)
The tank in this case can only have a minimum waste liquid
level of 24 feet if the maximum allowable stress is not to be
exceeded. Overfilling controls should be established at this
level.
We assume that the hazardous waste is a salt solution con-
taminated by heavy metals with the major component being ferrous
sulfate. Utilizing the National Association of Corrosion Engineers
(P ACE) 12 table, we find that ferrous sulfate has a corrosion rate
of greater than 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 by 0.1 inch per year = 5.1 years). Therefore, theo-
retically 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
.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 period, 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 actualcorrosion rate as part of the periodic
assessment of the tank’s condition within a given period and
report it to the 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, thereiore, reduce the required
minimum wall thickness, and increase the corrosion allowance);
introduce a new waste with lower specific gravity to reduce the
Stress; or prepare the tank for closure.
(2) 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
3—24
-------
corrosive waste at ambient temperature and at a maximum internal
pressure of 0.5 psig. The tank was built according to the fourth
edition of tJnderwr.iters’ Laboratory (UL) Standard 142 and installed
in accordance with the Flammable and Combustible Liquids Code of
the National Fire Protection Association (NFPA No. 30). The tanI
is 144 inches in diameter and has a uniform measured shell thick—
ness of 3/8 inch and 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 material of the tank.
The owner would like to store from 1,000 to 30,000 gallons
of waste in the tank at a given time. The following tabulation
from UL 142 indicates that a minimum thickness of 0.25 inch must
be maintained to provide for structural stability to accommodate
the upper volume limit of 30,000 gallons:
METAL THICKNESS — HORIZONTAL TANKS
Maximum
Minimum
Capacity
Diameter,
Thickness
of
U.S.
Gallons
Inches
Steel, Inches
550 or less 48 0.105
551 — 1,100 64 0.135
1,101 — 9,000 76 0.179
1,101 — 35,000 144 0.250
35,001 — 50,000 144 0.375
The tank, therefore, has a maximum corrosion allowance of
0.125 inch, which is 3/8 inch (current actual thickness) minus
1/4 inch (allowable minimum thickness). If the waste to be
stored has a corrosion rate of 0.05 inch per year, the expected
iife of the tank storing 30,000 gallons of waste is 2 1/2 years
((0.125 inch divided by 0.05 inch per year) prior to coating,
lining, or closing the tank. Even if the tank were to be utilized
to store a maximum of 1,000 gallons, however, the tank could still
only be used for a period of 2 1/2 years (0.37E minus 0.250 inch
divided’ by 0.05 inch per year) beause a tank that is 144 inches
in diameter must have 0.25 inch minimum wa-li thickness, according
to this standard.
(3) Example 3 . A vertical, cylindrical welded carbon steel
tank is to be converted to storage of hazardous waste at a maximum
design pressure equal to 0 psig (atmospheric pressure) and of
aabient temperature. The tank was built in accordance with the
3—25
-------
9) .16 14) .19
13) .18 19) .16
The minimum of these local averages is used for comparison with
the required minimum thickness.
Since the measured thickness is less than the required mini-
mum thiOkness, 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:
t = ( 2.6 x H—I (55) (1.2 ) H = 17.6
( .85) (21000 ) rounding down
q = 17
The owner—operator woull install overfilling controls (e.g.,
high—level alarms or automatic feed cutoff) at 17 feet. In addi-
tion, since no corrosion allowance remains, the owner—operator
should coat or line the tank to prevent further loss of their
thickness.
* Formula from Example 1.
second edition of API Standard 650. The tank is 55 feet in dia-
meter and 25 feet high. The specific gravity of-the waste to be
stored in the tank was measured to be 1.2. Therefore, the minimum
wall thickness in inches is:
t = ( 2.6) (55) (24) (1.2 ) *
(.85) (21000)
t = 0.23 inches
The wall thickness of the tank is nonuniformly corroded.
The thickness was measured in 30 locations, and
the results are
given below:
1) 0.20 9) 0.16 17) 0.20
25) 0.21
2) 0.19 10) 0.20 18) 0.22
26) 0.19
3) 0.22 11) 0.21 19) 0.14
27) 0.21
4) 0.24 12) 0.19 20) 0.23
28) 0.24
5) 0.22 13) 0.17 21) 0.21
29) 0.19
6) 0.20 14) 0.17 22) 0.20
30) 0.19
7) 0.18 15) 0.18 23) 0.21
8) 0.23 16) 0.23 24) 0.24
At points 9, 13, 14, and 19, 5 additional
measures were made
along a longitudinal strip 4 inches long. The
average measured
thicknesses at these points were as follows:
3—26
-------
e. Decision Process . The minimum thickness of a tank
shell can be maintained by designing the tank with extra shell
thickness (corrosion allowance) or by lining or coating the tank.
The owner-operator must decide how the shell thickness will be
maintained when the tank is built or converted to store hazardous
waste. No specific guidance can be given on this decision. The
following example illustrates the decision—making process that
an owner—operator may undergo when converting an existing storage
tank to use as a hazardous waste storage tank.
When the tank was built, one of the following was the case:
(1) Extra metal thickness was provided as a corrosion
allowance. If so,
(a) the tank may have to be derated, meaning the
liquid level has to be lowered in order not
to exceed the maximum allowable stress;
(b) the tank may be used to store a hazardous waste
that is relatively noncorrosive with the tanks
material of construction so that the corrosion
allowance is not exceeded;
(c) lining material may have to be added;
(d) coating material may have to be added.
2) An interior lining or coating material was provided
when the tank was first constructed. If so, the tank
needs to be examined to determine whether the lining
or coating is in good condition. If there are leaks,
cracks, holes, or other deterioration, the tank should
be relined or recoated. The procedure used to calcu—
late the minimum required thickness of metal must be
followed to determine if the tank is structurally
sound in its present condition.
C. ANCILLARY DESIGN FEATURES FOR SAFE OPERATION
1. Measurement Devices
Process variables need to be measured and maintained routinely
at certain values. hese variables are monitored by electrical,
mechanical, or chemi’ al devices. Control devices may serve this
purpose. The following measures should be taken regularly to
ensure safe operation of a tank facility. The permit writer
should determine whether or not procedures needed to measure
these variables are adequate.
3—27
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a. Temperature of waste. Abnormal temperatures may indi-
cate that undesired reactions are occurring in the tank, excessive
heat iS being genexated, hazardous vapors are being. emitted, etc.
b. Pressure. Measure to ensure that dcaign pressure of a
tank is not being exceeded.
c. Flow. Measure to preclude overfilling of a tank, etc.
d.: Level. Measure to preclude overfi.Lling, maintain
desired liquid level.
e.: Specific Gravity. Measure to ensure that weight of
liquid does not place excessive stress upon the tank.
Refer to Perry’s Chemical Engineers’ Handbook , Chapter 22,
for a description of measurement devices. 1 ’
2. Overfilling Control Systems
40 CFR 264.192 states that tanks must be equipped with over—
filling control systems. The two most important components of
overfillirig control, flow measurement, and level measurement, are
discussed below. 17
a. Flow Measurement . Monitoring of the flow rate into
the tank can be used in continuous flow systems to prevent over—
filling or pressure buildup owing to an increase in the in—flow
rate. Flow rate measurements alone are, however, insufficient
to prevent overfilling. A complete overfilling control system
for a continuous flow tank should also include at least one of
the following:
(1) an alarm triggered by excessive flow rate and an
accessible feed cutoff valve;
(2) a by—pass line to a standby tank; or
(3) a feed cutoff system or alarm triggered by a liquid
level measurement device as described in the following section.
The major types of flow measurement devices are escribed below:
(a) Local static pressure. The pressure on the surface
of the pipe is measured by making a small hole perpendicular to the
surface and coriecting the opening to a pressure—sensing element.
(b) Velocity meters. Pitot tubes measure local velo-
cities by measuring the difference between impact pressure and
Static pressure.
(C) Pressure meters. The rate of flow through the pipe
is calculated from the pressure drop caused by the constriction.
3—28
-------
(d) Mass flowmeters. The mass flow rate can be measured
directly by creating angular momentum with an impeller and then
tneasuring the torque this momentum imparts to a turbine; or the
volumetric flow rate can be measured and the mass flow rate cal-
culated using fluid density.
b. Liquid—Level Measurement and Control. 11 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. Several types of liquid
level measurement devices are discussed below, any of which
could be used to control a switch for an alarm or feed cutoff
valve.
(1) Float—Activated Devices
Float—activated devices are characterized by a float on the
surface of a liquid. A level sensing electrical switch based on
a magnetic float—activated device is illustrated in Figure 3—1.
(2) Displacer Device
Displacer—activated level measuring is accomplished through
iteasurement of the buoyant force on a partially submerged float.
rhe force on the displacer (i.e., float) can be determined by
neasuring compression of a spring that holds the displacer in
place or through measurement of the force on a torque tube con-
nected to the displacer by a rod. The range of a displacer
device is limited to the length of the displacer.
(3) liead Device
A variety of devices utilize hydrostatic head as a measure
Df level. The majority of these devices utilize standard pres-
sure and di fferential pressure measuring devices. Figure 3—2
illustrates a simple hydrostatic head device in which a constant
ir flow is used to prevent entry of the process liquid into the
neasuring system.
c. Freeboard . In addition to overfillinc controls, owners—
perators of open tanks are required to maintai i sufficient free—
Doard to prevent overtopping owing to wind or wave action or
recipitation.’ 7 In a tank of less than 100 meters in diameter
:he maxix um height of a wind—induced wave is 4 to 5 inches. 18
Ulowing another 4 to 5 inches for splashing on the sides and
recipitation, 8 to 10 inches of freeboard is adequate for most
:anks.
3—29
-------
FtGURE 3 -1.
FIOAT-ACTIVATED LEVEL
SENSING
L’:.:
-.
_-.- ---;
(S?
— — -.
. .
a Iu( m.
• ( c d
I4
— —
- -,.
____
;.•-- •—-,.- -
-
- •.d
• -• -
• - •: - -
— •-
-
• ‘ :
: -
_
/ - , - •_.t____
L ,- - -- --- - — .• -
- — — _i_ —- • — — —
- ‘ •..Fç - ‘ - - - -. • -.
- ____ — . -f - ; —:
— -m. — - —
a
9urce : Chemical Engineers’ Handbook, 5thed., -Robert H. Perry
and Cecil H. Chilton (New York: McGraw-Hill, 1973).
Copyright 1973. Used by permission of McGraw—Hill Book
Company.
3—30
SWITCH
•
-------
FIGURE 3-2
HEAD DEVICE rOR LIQUID LEVEL MEASUREMENT
- . -1 4 *
—-44 - . - Sc__’
‘p, --
- - -r. -
= : -“
— —- -
- -- -
: . — — S — - — _• _ l,._ —. —
_____ - - ---- - .-. r -.
— S -’•._ —— 7 ’ — — — a•r_• S —
— —
-4 — --- —
‘-4---- _- ‘.; - —-4— . ‘— — ‘ —-, - —
. 5—- . - 5--—-- _•_—,_•_•_____ - ‘• - -
—- . 5 - ‘ - - - - . .
, I . - ‘ —‘---:= ..- . - -
.- -4: ’i t - - - - ,- - -c - .
..z;r — - :_ -. -- -
. - . 5- - - - - ‘ .- ., ‘ , ,- - - - -‘ - - - - ‘-- _ t. 1 _. .- -
_ _5 5 - . .a 4 • .— -‘ - —
. ,, ‘_: -4 . -— .J_ _ ._ r- .— —
r’- : - ‘ -- ---- . - - .-- - .
• •; _4• — —. • . . --. -. -- - — -S
- ‘ -- Ti’ - - --i • . - ;
..J 1 - - - -—- . . - ‘— - .-. — . -- - .z - - - .- : • -— .- —
:‘ Z .?’•- _ ., -
- ‘-,- —- • -Y: - - -
‘r . - - —
t. — j. - - - .5. - - • . . - — — — -
5
‘ -‘ — -
5-- - - —
-
Chemical Engineers Handbook, 5th ed., Robert H. Perry
and Cecil H. Chilton (New York: McGraw—Hill, . .1973).
Copyright 1973. Used by permission of McGraw—Hill Book
Company.
3—31
TI
Meosinr
ant
-T: - ---‘;.,-: Air -
‘ SuppLy
Sour ce :
-------
PROCESS FLOW AND INSTRUMENTATION
A process flow diagram (PFD) depicts flow directions of fluid
d fluid movement ii terms of mass per unit time (mass balance)
d volume per unit time (Figure 3—3). The mass balance is the
mmation of all fluid quantities that enter and leave a piece of
uipment. What leaves and enters must be equal. Since volume
.n be compressed or expanded, volume is not always in balance.
Process flow diagrams are important to determine the flow
.rection of liquid or vapor within the facility. Incompatible
Lstes should not flow in common piping or vapor recovery systems.
addition, process flow diagrams may indicate flow rates. High
.0W rates can cause equipment failures through erosion.
The simple process flow diagram (Figure 3—3) indicates that
tste streams number 8 and 14 are vented directly to the atmos—
Lere, and stream number 16 is discharged directly to the city
wer system. The permit writer should be satisfied that these
scharges meet applicable NPDES and Clean Air Act requirements.
Piping and Instrumentation Diagram (P&ID )
A P&ID shows instruments such as valves, level and pressure
)ntrols, and temperature and pressure indicators used to control
id monitor the operation of a tank. The permit writer should
amine the diagram to assure that incompatible wastes will not
! mixed because of facility design (see Figure 3—4).
Evaluation should include the following items:
° Whether appropriate lIquid level control and venting
control instrumentation are provided (they are of
primary concern in a tank facility). All control
mechanisms should be adequately sized.
O Whether a common vapor system or separate systems
to handle incompatible waste are used.
• Plot Plan
A plot plan of a facility with each piece of equipment drawn
) scale locates each piece of eqt ipment in relation to the entire
Icility. From a plot plan the adequacy of the following items
rn be evaluated:
o diking and drainage systems for tanks;
o space requirements between equipment;
0 ‘ eceiving areas for wastes.
• Tank Diagrams and Data Sheets
A typical tank diagram (see Figure 3—5) and a typical tank
ta sheet (see Figure 3-6) are presented and should be used in
njunction with the P&ID.
3—3 Z
-------
FIGURE 3-3
A SIMPLE PROCESS FLOW DIAGRAM
OILY WATER
To SIWEA
Sr
COM O $T
bRL*KOO*W
sass BALANCE
TA8LE
OFF-SITE
DISPOSAL
Source: Fred C. Hart Associates, Inc . , 1 O.
-------
FIGURE 3-4
I7
I\!A d
LS/b$* I
JFL4U4
.,
P$IA
COMP fN1
IU*KOO*N
MASS BALANCE
TABL(
A SIMPLIfIED PIPING AND INSTRUMENTATION IAGRAI4
OIL
CITY
WATER
OILY WATEB
T SEWER
PUMP
Source: Fred C. Hart Assocjatei, Inc ,, 1980.
-------
FIGURE 3—5
A SIMPLE TANK DIAGRAM
®
41
J:MIN. -
Source: Fred C. Hart Associates, Inc.
HLL High liquid level; LAH 2 Level alarm high; LU.. Low liquid level;
LAL * Level alarm low.
0
-------
1 LI( &V/U’ ‘U)i S u.,3q rvtA.,
High liquid ieve (HLL)
2 VAPOR 3 99 0.584 95 16.2 ieve Ahrm-Htgh(LAU)
3 LIQUID 1040 40.3(MIN.) 95 16.2 . Normal Liquid Level(NLL
1
Level Alarm-Low(LAL)
Low Liquid Level(LLL)
• Co tro1 Low(CL)
Low Control Leyel(LCL)
VAPOR PRESSURE MAX. .AN8. °F — PSIA
PROCESS CONTANINENTS
PRESS MARGIN; MIN SPEC. _______+_______ _______ PSI
HIM. DESIGN PRESS AT TOP _______ PSIG (MARG, + OPER,)
SYSTEM PSV SET AT _______ PSIG LOCATED
MIN. DESIGN TEMP @ PSIA
.
EXTERNAL PRESS DESIGN. F0RI_
VESSEL SUPPORT DATA: SKIRT LEGS LUGS SADDLES_______
HEIGHT KIN. MW. GRADE FIREPROOFING_______
NOZZ. NO. ET RATING & INT’L. TYPE
NO. SERVICE REQ ’D. SIZE FACING OR NOTE
Manway
J-5
J-4
J-3
J-2
PSV
8
7.
Drain 1 2”
L&J
Overflow •1 4”
Liquid 1 2”
Vapor Out 1 4” 20 FPS/1.4 psi/bOO ft. PSV • Press Sensing Valve
1 Llq.&Vapov 1 4” 20 FPS/),7 psl/1000 ft. . FPS feet Per Second
feed
cn,,rcp’ Frpij (‘. Hart Associates. Inc.
-------
REFERENCES
40 CFR 260; (45 Fed. Reg. 33076 [ May 19, 1980] ).
Compatibility of Wastes in Hazardous Waste Management Facilities:
A Technical Resource Document for Permit Writers. Fred C. Hart
Assoc., Inc., for U.S. EPA, Office of Solid Waste. 1981.
American Petroleum Institute. Standard 650, Welded Steel
Tanks for Oil Storage. 6th ed. Revision 3. Washington,
D.C., 1979.
American Petroleum Institute. Standard 620, Recommended Rules
for Design and Construction of Large, Welded, Low—Pressure
Storage Tanks. 5th ed. Washington, D.C., 1973.
The American Water Works Association. D100—79, Standard for
Steel Tanks——Standpipes, Reservoirs, and Elevated Tanks for
Water Storage. Denver, Colorado, 1979.
American Society of Mechanical Engineers. Boiler and Pres-
sure Vessel Code, Section VIII. New York, 1974.
National Fire Protection Association NFPA 30. “Flammable
and Combustible Code — 1977.” Quincy, Massachusetts.
Underwriters Laboratories UL142. Standard for Steel Above—
ground Tanks for Flammable and Combustible Liquids. 4th ed.
Northbrook, Illinois, 1972.
American Concrete Institute ACI—350R—77 Concrete Sanitary
Engineering Structures, Ad Committee Report 350 Detroit,
Michigan, 1977.
). American Petroleum Institute. Standard 2000, Venting Atinos—
pheric and Low Pressure Tanks, 2d ed. Washington, D.C.,
1973.
L. Robert H. Perry and Cecil II. Chilton, eds. Chemical Engineers’
Handbook . 5th ed. New York: McGraw—Hill, 1973. [ The manual
provides information on movement and storage of materials
and process controls in addition to materials of construction.]
). National Association of Corrosion Engineers. Corrosion
Data Survey. Metals Section. 5th ed., Houston, Texas, ‘975.
3. National Association of Corrosion Engineers. Corrosion Data
Survey. Nonmetals Section. 5th ed., Houston, Texas, 1975.
. American Concrete Institute, Committee 515. “Guide for the
Protection of Concrete against Chemical Attack by Means of
Coating and Other Corrosion Resistant Materials,” ACI Journal,
Proceedings , V. 63, No. 12, Dec. 1969, pp. 1305—1392.
3—37
-------
Marks. Standard Handbook for Mechanical Engineers . 8th ed.
New York: McGraw—Hill, pp. 8—143.
National Association of Corrosion Engineers. Direct Calcula-
tion of Economic Appraisals of Corrosion Control Measures.
Houston, Texas, 1972.
• 40 CFR 264, Subpart J (46 Fed. Reg. 2867 (Jan. 12, 19811 ).
yen Te Chow, ed. Handbook of Applied Hydrology . New York:
McGraw—Hill, 1964, pp. 23—25.
3—38
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CHAPTER 4
INSPECTION
Inspection and repair are the two major components of proper
tairitenance in any type of facility. Inspection is the foremost
;tep in maintenance and is of prime concern to the permit writer
ecause the inspection procedures and frequencies must be suff i—
ient to prevent uncontrolled discharges to the environment.
This chapter covers procedures used to inspect tanks. Topics
i1l include both external and internal visual inspection points
there a tank and its auxiliary equipment should be inspected and
ow it should be inspected, a brief description of tools and electo—
iechanica]. equipment utilized to perform inspection, and a rationale
Eor determining frequencies of inspections.
The regulatory requirements for inspections of tanks include:
° a list of components and minimum inspection frequencies
for external tanks inspections;
o a requirement for internal inspections with procedures
and frequencies to be specified by the owner—operator; and
o a requirement that procedures for spill response arid
tank repair be specified in the contingency plan. 1
EVALUATION OF AN INSPECTION PLAN
An inspection plan consists of a checklist of equipment and
parts to be inspected, procedures for inspecting equipment, and
frequency of inspection.
Table 4—1 is a sample checklist for inspecting a tank. A
:omprehensive plan should include procedures for inspecting each
item in the list.
4—2
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TABLE 4—1
TANK INSPECTION POINT LISTING
External Inspection —— Tank in Service
(1) Ladders, Stairways, Platforms, and Walkways
— corroding bolts
— cracked or spalled concrete pedestals
— low spots where water can collect
(2) Foundations
— erosion
— uneven settlement
— cracks and spalling in concrete pads, base
rings, 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) Protective Coatings
— rust spots, blisters, and film lifting
(5) Tank Walls
— corrosion
— discoloration of paint surface
— cracks at nozzle connections, in welded seams,
and in metal ligament between rivets
— cracks, buckles, and bulges
(6) Tank Roofs
— malfunctioning of seals
— blockage of water drains on roofs
— corrosion
(7) Overfilling Control
— malfunction of controls
— insufficient freeboard
• Internal Inspection —— Tank out of Service
(1) Preparation
— check air quality inside tank
— roof and internal support for deterioration
(2) Roof and Structural Members
— malfunctioning of roof’s seals
— corrosion
— loss of metal thickness
4—3
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(3) Tank Shell
— corrosionof vapor space and liquid—level line
— cracking of plate joints
— cracking of nozzle connection joints
— bulges, holes, or cracks of lining (if the inside
shell is coated)
— loss of metal thickness
(4) Tank Bottom
— corrosion pits
— sprung s ams
— rivets for tightness and corrosion
— depressions in the bottom areas around or under
roof supports and pipe supports
— bottom thickness
— unevenness of the bottom
Ancillary Equipment
(1) Pipes, Valves, nd Fittings
— loss of metal thickness
— leaks
— corrosion r deterioration
(2) Meat Exchangers
— corrosion or pitting
blisters
— erosion
— lQaks
(3) Pumps and Compressors
— foundation cracks and uneven settling
— leaky pump seals
— missing anchor bolts
excessive vibrations and noise
— depleted lubricating oil reservoir
— odor an4 smoke
— excessi’ e dirt
— excessive corrosion
— excessive vibration of pumps
— leaks and cracks of assembly bolts, gaskets,
cover plates, and flanges
(4) Instruments, Control Equipment, and Electrical Systems
— check proper operation of equipment by qualified
personnel according to the manufacturer’s recom-
mended frequency and methodology
4—4
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• TANK EXTERNAL INSPECTION —— TANK IN SERVICE
• Procedures 2
A visual maintenance check is the simplest way to detect
rroded or broken equipment.
An external inspection should include the following components
f the tank: ladders, stairways, platforms, walkways, foundations,
nchor bolts, pipe connections, overfilling controls, liquid level
n tank, protective coatings, insulation tank walls, tank roofs,
nd valves.
a. Ladders, Stairways, Platforms, and Walkways . Even though
he failure of any of these items would probably not cause leakage
r rupture of a tank, they do pose significant safety hazards and
re indicative of the overall condition of the tank facility.
tairway or walkway failure may be imminent if the concrete peds—
als are cracked or spalled. Bolts should be checked for corro—
ion at the contact points. Rust stains showing through paint are
vidence of corrosion. Low spots where water can collect should.
e examined carefully. The thickness of metals should be checked
ith calipers, and hammering can be used to check integrity. All
efects found should be marked with paint and recorded; repair
hould proceed as soon as possible.
b. Foundations . Erosion and uneven settlement should be
etected and corrected before serious damage occurs. The concrete
ads, base rings, and piers should be examined for cracks and
palling. Such deterioration can be uncovered by scraping the
uspected areas. The joint between the tank bottom and the con—
rete pad or base ring may have a seal for stopping water seepage,
nd, if so, it should be inspected for deterioration. Any wooden
upports for tanks should be checked for rot by hammering. Metal
oss in steel columns or piers can be checked by caliper readings
•gainst the original (or previously measured) thickness. Anchor
olts can be checked by visual inspeètion and hammering. Serious
oundation settling is usually indicated by distortion of anchor
‘olts, buckling of columns, and excessive concrete cracking.
c. Pipe Connections . The pipe connections to a tank
hould be inspected for external corrosion by visual examination,
craping, and picking. Underground piping should be uncovered
.f severe soil contamination is suspected. The pipe should be
craped, cleaned, and visually inspected. In the event that a
ank has settled excessively, special attention should be given
0 piping connections and piping as they may have cracked or
become distorted.
d. Overfilling Controls and Freeboard . Overfillir&g control
quipment should be inspected for corrosion, fouling, or other
talfunctions. In open tanks the liquid level should be checked
.o ensure that adequate freeboard remains to prevent overtopping
4—5
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wing to wave or wind action or accumulated precipitation. Section
rv contains additional details on inspection of measurement and
process control devices.
e. Protective Coatings . Rust spots, blisters,...and separa-
tion of the tank’s protective coating from them tank can usually
be detected by visual inspection or by scraping the film in sus-
pected areas. Paint blisters usually occur on the roof and on
the sunny side of the tank. Separation (or lifting) commonly
occurs below leaks in the seam.
f. Tank Walls . - External corrosion can occur on underground
portions of tanks and related structures. If any foreign material
has collected around the bottom of the shell, or if the tank is
below grade, the shell should be inspected at least a foot below
grade at several locations. Visual inspection, picking, scraping,
and hammering are usually sufficient to locate corroded areas.
When corrosion is found, thickness measurements should be taken
at corroded points. This can be accomplished with ultrasonic or
radiation—type instruments. The thickness measured externally
should be compared with the thickness measured internally to lo—
cate the thinnest points and to determine the corrosion allowance
left to operate the tank safely.
In addition to corràsion detection, the tank shell should
be inspected for leaks, cracks, buckles, and bulges. Leaks can
be spotted by a discoloration of paint in the area below the leak
or by leak—testing devices such as ultrasonic or vacuum devices.
Cracks can be found at nozzle connections, in welded seams, and
the metal ligament points between rivets. Cracks, buckles, and
bulges can initially be spotted by visual inspection, and their
extent can be more thoroughly determined by techniques such as
the magnetic—particle, penetrant—dye, or vacuum—box methods
described below.
All the external valves on the tank should be visually in-
spected to ensure that the seating surfaces are in good condition.
If there are signs o -corrosion, the thickness should be measured.
In cold weather, water draw—off valves should be inspected closely
to detect possible damage from freezing. Pressure vacuum vents
and breather valves should also be inspected for plugging, tight
seals, and corrosion. All pressure gauges should be tested for
accurate readings by using a deadweight tester or equivalent.
g. Tank Roofs . - Regardless of appearance, tank roofs should
be inspected thoroughly by h mmer.ng because of the strong possi-
bility of corrosion. Some safety measures should be taken before
and during the inspection, however, especially when the stability
of the roof is questionable or harmful vapors may be present.
Safety harnesses should be worn and planks long enough to span at
least two structural supports . should be laid as walkways until the
Structural safety of the roof is established. In addition, if the
4—6
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stored waste is volatile, tests for flammable vapors, generally
performed with a portable combustible gas indicator, should be
made prior to inspection.
Water drains on roofs should be inspected frequently for
blockage, since the accumulation of precipitation can cause a
floating roof to sink and fixed roofs to fail or corrode more
rapidly.
2. Inspection Tools and Electromechanical Equipment 2
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, or flange spreader
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, and leveling and plumbing tools.
The electronic devices include ultrasonic and electromagnetic
instruments. In addition, there are chemical examination methods
and destructive test methods.
The selection of a particular type of method is normally
based on the inspection requirement and cannot be generaliied.
Therefore, this section will only attempt to familiarize the
permit writer with some methods, as described below.
a. Penetrant—Dye Method . Penetrant dyes are often used to
detect surface cracks on the outside of a tank that would not be
revealed by a visual inspection. The penetrant is applied to a
cleaned and dried surface by either brushing or spraying. After
a few minutes of contact, a chemical developer is then sprayed
onto the surface to give a white appearance upon dyeing. The dye
stains the developer and exposes the extent and size of any defects.
b. Vacuum- Box Method . The vacuum box is an open box in
which the lips of the open side are covered with a sponge rubber
gasket, and the opposite side is glass. A vacuum gauge and air
siphon connection are installed inside the box. The seam of the
tank shell 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 any leak exists, bubbles will form inside the box
and can be seen through the glass.
c. Ultrasonic Instruments . Ultrasonic instruments can be
used to measure the tank’s thickness and determine the location,
size, and nature of 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
4—7
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type utilizes elec ric 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. Therefore, the time interval
between the pulses corresponds to a certain thickness.
C. INTERNAL INSPECTION —— TANK OUT OF SERVICE 2
1. Preparation and Safety .
The safety aspects preceding an internal inspection are very
important. The tank should be emptied of liquid, freed of gases,
and cleaned or decontaminated, if necessary. Respiratory protec-
tion should be provided for persons entering the tank. Several
types of respiratory protection are available, ranging from highly
protective self—contained bre athing apparatus to less—protective
air—purifying respirators. A complete discussion of safety pro-
cedures for internal tank inspections is beyond the scope of this
manual. Persons not experienced in the conduct of internal tank
inspections should contact the Occupational Safety and Health
Administration for assistance in establishing safety procedures.
Adequate lighting must be provided inside the tank for a safe
and effective inspection. The roof and internal supports should
be inspected first, followed by a preliminary visual inspection
of the shell to ensure that the tank is structurally stable.
2. Roof and Structural Members .
A visual inspection of the roof interior usually suffices.
Thickness measurements should be performed, however, when corro-
sion is evident. Special attention should be given to interior
roof seals.
3. Tank Shell .
The shell should be examined visually for corrosion. Tank
shell thickness should be measured at representative points to
ensure that the minimum thickness is maintained. While the
bottom, the roof, and especially the shell are being inspected
for corrosion, the plate joints and nozzle connection joints.
should be inspected for cracking. . f any cracking is found, a
more thorough investigation by magnetic—particle, penetrant—dye,
or radiographic methods may be needed.
When the inside surfaces of a tank are lined with corrosion—
resistant material, it is important to check for holes or cracks.
Scraping or dye penetration is effective in locating pinholes
and tight cracks. Bulges in the lining indicate leakage behind
the lining and possible liner deterioration.
4—8
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4. Tank Bottoms .
Tank bottoms should be hammered thoroughly to detect corro-
sion pits and sprung seams. The rivets should be checked at ran—
doni for tightness and corrosion. The depressions in the bottom
and the areas around or under roof supports and pipecoil supports
should also be checked for corrosion. Unevenness of the bottom
may be caused by settling and should be checked visually.
D. INSPECTION OF ANCILLARY EQUIPMENT 2
i.. Visual Inspection of Pipes, Valves, and Fittings
Inspections of pipes, valves, and fittings are usually con-
ducted to note any losses in metal thickness owing to external or
internal deterioration. These equipment parts are also subject
to erosion or wear because of the effects of high liquid turbulence
or velocity. It is preferable to inspect areas around pipe bends,
elbows, tees, and other restrictions, such as orifice plates and
throttling valves.
Visual inspection techniques include checking for leaks, mis-
alignment, unsound piping supports, vibration or swaying, external
corrosion, accumulations of corrosive liquids, and indications of
pipe fouling. Thickness measurements while the pipes are in opera-
tion can be taken utilizing ultrasonic or radiographic techniques.
If the tank is out of service, 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 extension 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.
Pressure tests for pipes may include a design test for newly
installed systems and leakage and tightness tests for existing
systems. Various media used for pressure testing including water
steam, air, apd carbon dioxide or other gases. [ Note: Pressure
tests with air are not recommended for tanks themselv:s because
they are not likely to detect a leak below the liquid level of
the tank and because they present a danger of rupturing the
tank or causing expulsion of its contents.]
Piping systems that cannot be inspected visually are fre-
quently pressure tested. They include:
underground and other inaccessible piping;
complicated manifold systems;
° small pipe and tubing systems;
0 all systems after a chemical cleaning operation.
4—9
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2. Visual Inspection of Heat Exchangers
Deterioration may be expected on all surfaces of exchangers
and condensers that contact chemicals, aater (both salt and fresh),
and steam. The form of attack may be electrochemical, chemical, or
mechanical, or a combination of the three. The attack may be further
influenced by certain accelerating factors such as temperature,
stress, fatigue, vibration, impingement, and high—flow velocity.
Appurtenant items to exchangers and condensers such as
ladders, platforms, foundations, pipe connections, paint, and
insulation can be inspected visually in a manner analogous to
the inspection of the tank proper. The exchanger or condenser
itself can be visually inspected for rust spots and blisters.
If the unit is out of service, the inspection procedures can be
more detailed. A scraper and a ball—peen hammer can be used in
conjunction with a visual inspection to detect areas subject to
excessive corrosion and erosion. Pressure tests utilizing a
test fluid can also be used to detect leaks or excessive erosion
or pitting.
3. Inspection of Pumps and Compressors
Mechanical wear is the predaninant 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.
Routine visual inspection of pumps and compressors to deter-
mine general conditions during operation should include:
o foundation cracks and uneven settling;
° leaky pump seals;
o missing anchor bolts;
o leaky piping connections;
o excessive vibrations and noise;
o deteriorating insulation;
o depleted lubrication oil reservoir;
o missing safety equipment such as a pump coupling guard;
o burning odor or smoke;
o excessive dirt;
o excessive corrosion.
Sinre 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.
4—10
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4, Visual Inspection of Instruments, Control Equipment, and
Electrical Systems
Instruments and control equipment are classified according
to the type of measurement of function performed. They include:
0 flow rate;
o level controls;
0 temperature gauges;
0 pressure gauges;
0 control valves;
• alarms and emergency shut—off devices;
0 analyzers.
The inspection of these instruments and controls includes checking
transmission systems, power supplies, seals, panels, and other
associated equipment. In many cases, instruments and controls are
inspected daily by the operator since they are an integral part
of the daily operation of the facility. All instrumentation and
control equipment should be thoroughly inspected and calibrated
according to the manufacturer’s recommended frequency and methods.
Environmental conditions such as heat, moisture, chemical
attack, and dirt are major reasons for deterioration of electrical
systems. Insulations, enclosures, operating mechanisms, insulating
and lubricating oils, protective relays, bearing, batteries, con-
nectors and rectifiers are areas that should be inspected.
E. FREQUENCY OF INSPECTION
Inspection intervals for a tank and its equipment are either
specified in the regulations or reviewed by the permit writer as
part of the inspection schedule.
The frequency of most components of an external inspection
of a tank have been specified in the regulations. Table 4—2
summarizes these requirements.
TABLE 4—2 -
REQUIRED INSPECTION FREQUENCIES
Inspected Daily
— overfilling control systems
- data from monitoring equipment (e.g., pressure and
temperature gauges)
— level of waste in uncovered tanks
Inspected Weekly
— above—ground portions of tank (e.g., exterior of tank
shell and roof)
— area immediately surrounding tank
4—11
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As stated in §264.15(b), 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.
The §264.194(b) requirements for periodic comprehensive tank inspec-
tions specify the following additional factors to be used in deter-
mining inspection intervals:
* material of construction of tank;
o type of erosion or corrosion protection used;
o characteristics of waste being stored;
0 rate of corrosion or erosion observed during previous
inspections. 1
The expected service life of the tank can be a useful tool
for establishing a minimum inspection frequency. For example,
a tank with an expected service life of 25 years might initially
be subjected to a comprehensive inspection every 3 years to
establish the actual rats of corrosion or deterioration. As the
tank approaches the end of its service life and the probability of
leaks or ruptures increases, however, the inspection frequency
should be increased to every 1 or 2 years.
In some cases the owner or operator may prefer to conduct
more frequent comprehensive external inspections of the tank to
avoid the expense of frequent internal inspections. In the example
cited above, the 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 5 years. As the condition of the tank deterio-
rates, however, the frequency of internal inspections should
increase to every 1 or 2 years.,
F. RESPONSE TO SPILLS AND LEAKS
Section 264.194(c) of the standards for inspection of hazard-
ous waste tanks provides that owners or operators must specify
the procedures they intend to. use to respond to tank spills or
leakage, including. procedures and timing for expeditious removal
of leaked or spilled waste and repLir of the tank.
The procedures specified by the owner—operator will depend
largely on. site—specific cIrcumstances. Factors will include the
permeability if the area surrounding the tank, availability of
excess capacity for emptying the tank, and the materials of con—
structiort of the tank.
Table 4—3 summarizes the types of incidents likely to occur
at a tank facility that should be addressed in the contingency plan.
4—12
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TABLE 4—3
OP ATIONAL PROBLEMS OF TANKS 4
Bulk Storage Facilities —— Tank Farms and Tankage
— Overfilling of tanks
— Rupture of tanks
— Leaks in tanks, pipes, valves, and fittings
— Leaks in containment dikes
— 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 overfi].ling
— Piping damage by collision with mobile equipment
— Spills from tank bottom cleanout and sludge disposal
— Spills from pipe and tankage changes
4—13
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REF ERENCES
1. 40 CFR 264, Subpart J (46 Fed. Reg. 2867—2868
(January 12, 1981]).
2. Guide for Inspection of Refinery Equipment (Chapters 1—V,
v i i, X—XIV), American Petroleum Institute, Washington, D.C.
3. 40 CFR 264, Subpart B (45 Fed. Reg. 33223 (May 19, 1980]).
4. Oil spill prevention control and countermeasure plan
review. A training program planned and presented by Rice Univer—
gity, Universities of Texas and Houston, and the U.S. E.P.A. The
pace Company, 1975.
4—14
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CHAPTER 5
COMMON TREATMENT. PROCESSES OCCURRING IN TANKS
A. Chemical Oxidation
1. Oxidation Processes
2. Types of Wastes Treated by Chemical Oxidation
3. Process Design and Operating Parameters
a. Type of Tank
b. Selecting Materials for the Oxidation Process
B. Chemical Reduction
1. Reduction Processes
2. Types of Waste Treated by Chemical Reduction
3. Process Design and Operating Parameters
c. Neutralization
1. Process Description
2. Application of Neutralization Process
3. Types of Tanks
4. Environmental Impacts
D. Precipation, Flocculation, and Sedimentation
1.. Precipitation
a. Process Description
b. Process Design and Operating Parameters
2. Flocculation
a. Process Description
3. Sedimentation
a. Process Description
b. Process Design and Operating Parameters
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
5. Environmental Considerations
5—1
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CHAPTER 5
COMMON TREATMENT PROCESSES OCCURRING IN TANKS
The service life of a tank can be prematurely shortened because
of interactions among the wastes with other wastes, with the tank’s
construction materials, and with the treatment process or treatment
reagents. 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 require-
ment, the operating requirements for tanks (40 CFR §264.192(a)) state
that “wastes and other materials (e.g., treatment reagents) 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
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.R
The following are common operating problems associated with
in—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
chronic acid 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 scaling . Salting and scaling is the formation
of an insulating layer at heat transfer surfaces that could contri-
bute 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 mix-
ing wastes that collectivsly generate large amounts of gaseous
emissions or result in an exothermic reaction may cause tanks to
explode, wa p, 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 waste, 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. En order to prevent
erosion, it is important to match the construction material of the
tank and ancillary equipment with the abrasion characteristics of
5—2
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the wastes expected to be treated, the anticipated liquid flow
rate of the treatment process, and the energy generated or dissi-
pated by mixing devices.
In order to determine whether a treatment process and its
associated reagents are suitable for the treatment of a parti-
cular waste within a particular 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 construction materials and design features.
-This chapter is meant to provide an overview of the treat-
ment processes that commonly occur in tanks and the possible in-
teractions 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..
A. CHEMICAL OXIDATION
1. Oxidation Processes 2
The processes discussed her e are based on chemical oxidation
as differentiated from thermal, electrolytic, and biological oxida-
tion 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 wast,ewater treat-
ment is a method for detoxifying obje çtionable and/or toxic
substances. These substances include:
o inorganic substances (e.g., Mn 2 +, Fe 2 +, S 2 , CN, S0 3 2 );
° organic substances (e.g., phenols, amirtes, humic acids,
odor— or color—producing or toxic compounds, bacteria, and
algae)
5—3
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Chemical oxidation processes most often used include:
o oxygenation or aeration;
0 ozonation
0 oxidation with hydrogen perioxide (very limited use);
0 oxidation with potassium permanganate;
o chlorination or hypochioririation;
o oxidation with chlorine dioxide;
0 oxidation with chromates or dichromates.
Table 5—1 is a listing of oxidants used to treat various wastes.
2. Types of Waste Treated by Chemical Oxidation 3
Liquids are the primary waste form treatable by chemical
oxidation. The most powerful oxidants are relatively nonselec—
tive; 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 axuines
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 organic matter
or the oxidizing agent 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.
5—4
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TABLE 5-].
OXIDATION WASTE TREATMENT APPLICATION 3
Oxidant Waste
Ozone Phenols
Chlorinated hydrocarbons
Air (atmospheric oxygen)
Suif ites
Sulf ides
Ferrous iron
Chlorine gas Sulfide
Mercaptans
Chlorine gas and caustic Cyanide
Chlorine dioxide Cyanide
Diguat
Par aquat
Sodium hypochiorite Cyanide
Lead
Calcium hypochiorite Cyanide
Potassium permanganate Cyanide — organic odors
Lead
Phenol
Diquat
Organic sulfur compounds
Rotenone
Formaldehyde
Permanganate Manganese
Hydrogen peroxide Phenol
Cyanide
Sulfur compounds
Lead
Nitric acid Benzidene
5—5
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3. Process Design and Operating Parameters
As a physicochemical process, the design of a system for
the chemical oxidation of a waste material involves considering
the following design and operating parameters:
0 type of tank (or reactor);
o mixing;
o location øf inlet and outlet pipes;
° pH or other process control;
o temperature control;
0 materials selection.
Both tank selection and materials selection are discussed below.
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 fluid ized 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 from
which are available).
The most important factor in selecting material is perfor-
mance regarding corrosion. The information listed in Table. 5—2
is valuable in estimating materials’ corrosion performance. Addi-
tional information on corrosion is provided in the technical
resource document titled Compatibility of Wastes in Hazardous Waste
Management Facilities.”
B. CHEMICAL REDUCTION
1. Reduction Processed 8
Reduction—oxidation, or Redox, reactions ar 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 be more easily handled.
Base metals such as iron, aluminum, zinc and sodium compounds
are good reducing agents. Sulfur compounds are among the more
Common reducing agents.
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TABLE 5—2
INFORMATION FOR ESTIMATING
CORROSION AGAINST PERFORMANCE 5
process Conditions
Main constituents (identity and amount) of waste
Impurities (identify and amount) in waste
Temperature
pH
Degree of aeration
Velocity of agitation
Pr essure
Estimated range of each variable
Environmental conditions
! ype 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?
What is the desired service life?
Experience
Has material been used in identical situations? With what
specific results?
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?
5—7
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2. Types of Waste Treated by Chemical Reduction 8
Liquids are the primary waste form treatable by chemical
reduction. the most powerful reducing agents are relatively
nonselective; 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 con-
tact between the reducing agent and the hazardous constituent.
Consequently, 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 reduc-
tion.
Table 5—3 lists some of the more common wastes and reducing
agents that undergo the reduction process.
3. Process Design and Operating Parameters
Analogous to the oxidation process, the design of a system
for the chemical reduction of a waste material involves the
following design and Operating parameters:
o type of tank (or reactor);
° reaction rates;
o mixing;
0 location of inlet and outlet. pipes;
o pH control;
0 temperature control;
0 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 required for chemical
reduction. This includes storage vessels for the reducing agents
and perhaps for the wastes, metering equipment for both streams,
and contact vessels with agitators to provide suitable contact of
reducing agent and waste. Some instrumentation is required t’
determine the concentration and pH of the waste and the degree of
completion of the reduction reaction. The reduction process may
be monitored by an oxidation—reduction potential (OR?) electrode.
This electrode is generally a piece of noble metal (often plati-
num) that is exposed to the reaction medium and produces an EMF
(electromotive force) output that is empirically relatable to the
reaction condition by revealing the ratio of the oxidized and re-
duced constituents.
5—8
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TABLE 5-3
REDUCTION WASTE TREATMENT APPLICATIONS 8
Waste Reducing Agent
Chromium (VI) Sulfur dioxide
(often flue gas)
Sulfite salts
sodium bisulfite
sodium hydrosulfite
Ferrous sulfate
Waste pickle liquor
Powdered waste aluminum
Powdered metallic zinc
Mercury
Sodium borohydride
Tetra—alkyl-].ead Sodium borohydride
Silver Sodium borohydride
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C. NEUTRALIZATION 9
1. Process Description
The process of neutralization is the interaction of an
acid with a base. The term wneutralization is often used to
describe adjustment of pa to values within the neutral range of
6.0 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 alkaline material, as determined by the required
final pH. The primary products of a neutralization reaction are a
salt and water.
2. Application of Neutralization Process
Neutralization is a treatment process of demonstrated techni-
cal and economic feasibility that is in full—scale use in a wide
spectrum of industries. A sample list of industries employing this
process is presented in Table 5—4. Neutralization finds its widest
application in the treatment of aqueous wastes containing strong
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 suitable liquid phase, as
in the case of alkali scrubbing of acid vapors. Slurries can be
neutralized, with due consideration for the nature of the suspended
solid and its dissolution properties. Sludges are also amenable to
pH adjustment, but the viscosity of the material complicates both
the process of physical mixing and the resultant contact between
acid and alkali, which is essential to the treatment. In principle,
even tars can be neutralized, although the problems of reagent
mixing and contact are usually severe, making the process impracti-
cal in most instances. Solids and powders that are acidic or
basic salts can also be neutralized if they are dissolved prior to
initiating the neutralization process.
Some of the more. common applications for pH treatment of
acidic and alkaline wastes are described in the fullowing para-
graphs.
Acid Exhausts — Industrial processes that utilize acids,
e.g., sulfric, 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 re-
cycled. In similar systems, flue gas desulfurization units absorb
and neutralize sulfur oxides with alkalies such as lime, limestone,
dolomite, or caustic soda.
5—10
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TABLE 5—4
MAJOR INDUSTRIES USING NEUTRALIZATION 9
INDUSTRY WASTEWATER pH RANGE
pulp and paper Acidic & basic
Dairy products Acidic & basic
Textiles Basic
pharmaceuticals Acidic & basic
Leather tanning and finishing Acidic & basic
petroleum refining Acidic & basis
Grain milling Acidic & basis
Fruits and vegetables Acidic & basic
Beverages Acidic & basic
Plastic and synthetic materials Acidic & basic
Steel pickling Acidic
By—product coke Basic
Metal finishing Acidic
Organic chemicals Acidic & basic
Inorganic chemicals Acidic & basic
Fertilizer Acidic & basic
Industrial gas products Acidic & basic
Cement, lime, and concrete products Ba sic
Electric and steaL generation Acidic & basic
Nonferrous metals—aluminum Acidic
5—11
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Petrochemical Waste Streams — Neutraljzajton is applied to:
(1) washwaters, acid or alkaline, (2) spent caustics, (3) acid
sludges (4) spent acid catalysts. Sulfuric acid and carbon dioxide
from flue gases are both used to treat spent caustic wastes. Pits
filled with lime, limestone, 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 5,000 gpd) neutralization of pickle liquor from steel
cleaning operations can be performed in a batch process, usually
with quicklime, typically, pickle liquor contains on the order of
70 grams of iron and 170 grams of sulfate per liter (approximately
5 percent sulfuric acid by weight). Large waste streams can be
handled in continuous flow systems, and other suitable alkaline
agents may be employed. If calcium—based materials are utilized
in the neutralization, 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 pre-
cipitate (at neutral pH) can produce a solid with poor settling and
filtering properties. Thus an oxidation step is often employed
since ferric hydroxide is very insoluble, and there is an optimum
ratio of terric to ferrous ions at which the sludge can be handled
most readily.
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 pro-
vide 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 require-
ments of the individual system.
The design of storage facilities for neutralizing agents
depends on the chemical reagents employed in the treatment pro-
cess. Caustic solutions and acids ma” 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, clan—
fiers, or vapor removal systems, depending on the specific neutra-
lization scheme,
In dealing with acids and alkalies, appropriate materials of
Con truction are required to provide reasonable service life for
equipment. Corrosion may result in deterioration of a construction
5—12
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material, e.g., lead is attached by hydrochloric acid. In many
cases, the specific concentration of a reagent is important in
selecting the corr.ect 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 — •3l6 stainless steel (SS) or
rubber
(dilute) — 316 stainless steel (SS), rubber,
carbon steel, or cast iron
calcium hydroxide — 316 SS, rubber, or carbon steel
Other less commonly used materials include glass, metal alloys
such as inonel, 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 need not be constructed
entirely of one material; it may be lined with lead, rubber,
glass, plastic, or other corrosion—resistant materials. Expected
length of service, temperature of operation, desired physical
strength, liquid flow rate, and mechanical 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 pro-
blems in contact with most metals.
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 re-
duction in the concentration of heavy metals if the treatment
proceeds to the basic pH range. Conversely, in neutralization
irvolving the addition of acid to alkali, there is the possibility
ot dissolution of metal—containing solids. This may, on occasion,
be disedvantageous, particularly if the suspended matter is slated
for removal, e.g., by filtration. FOr example, the anions result-
ing from neutralization of sulfuric and hydrochloric, acids are
sulfate and chloride, respectively. These ions ar.e not considered
hazardous, but there are recommended limits for discharge, based
primarily on problems in drinking water. The common cations pre-
sent after neutralization involving caustics soda and lime (or
limestone) are sodium and calcium (possibly magnesium), respec-
tively. These ions are not toxic and there are no ecomiuended
limits; calcium and magnesium are, however, responsible for water
5—13
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hardness and the accompanying scaling problem. Limestone neutra-
lization converts .the carbonate to harmless carbon dioxide gas.
With regard to atmospheric emissions, one must be cautious
not to neutralize wastewater streams indiscriminately. Acidi-
fication of streams containing certain salts, such as sulfide,
will produce toxic gases. If there is no satisfactory alterna-
tive, 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 preci-
pitate is of sufficie it purity, it would be a salable product;
otherwise, a disposal scheme must be devised.
D. PRECIPITATION, FLOCCULATION, 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 trans-
forms small suspended particles into larger suspended particles
so that they can be more easily removed. Sedimentation removes
the suspended particles from the liquid.
1. Precipitation
a. Process Description . Precipitation is a physicochemical
process whereby some or all of a substance in solution is trans-
formed 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 precipita-
tion reactions for indistrial or waste treatment purposes are
induced by one or a combination of the following steps:
0 adding a substance that will react directly with the
substance in solution to form a sparingly soluble
compound,
0 adding a substance that will cause a shift in the solu—
bility equilibrium to a point that no longer favors the
continued solubility of the substance ctiginally in
solution
0 changing the temperature of a saturated or nearly
saturated solution in the direction of decreased solu—
bility; since solubility is a function of temperature,
this change can cause ionic species to come out of
solution and form a solid phase.
5—14
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The most common precipitation reactions involve the removal
of inorganic ionic species from an aqueous medium. For example,
ZjflC 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 zinc 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 subse-
quent removal from the liquid phase. Precipitation per se does
not refer to any. of the liquid—solid 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 particles from a volume of liquid, it is very often
necessary to apply additional process steps, and these often in-
volve flocculation, sedimentaton, and/or some control that will
determine the final particle size —— and produce an easily separa-
ble solid (or crystal).
b. Process Design and Operating Parameters . The parameters
of interest for precipitation include the time required for reac-
tion, 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 thor-
oughly. Reagents should be added in a manner that minimizes contact
of the concentrated reagent with the tank surface. Although most
precipitation reactions take place extremely rapidly, a moderate.
amount of time is usually required to allow the chemicals to be dis-
persed throughout the solution. Characteristically, the solid par-
ticles, 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 precipita-
tion nuclei, or very small colloidal particles; or they can grow
into larger particles. Since mixing can shorten the dispersion
time of chemicals, some type of mixing equipment should be used.
The solids formed by precipitation are salts and should not
pose severe cor osion 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 the e chemicals to the waste
and upon mixing of the chemicals in order to minimize contact of
concentrated agents with the tank surface.
2. Flocculation
a. Process Description . The term flocculation as defined
here encompasses all of the mechanisms by which the suspended
5—15
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particles agglomerate into larger particles, including the addi-
tion of flocculating agents.
Many liquid—solid separation processes, such as sedimenta-
tion, are based on the use of gravitational and/or inertial 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:
o chemically induced destabilization of the repulsive sur-
face—related forces, thus allowing particles to stick
together when contact between particles is made;
.° chemical bridging and physical enmeshment between the
now nonrepelling 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 sedi-
mentation, provided a sufficient density difference exists between
the suspended matter and the liquid.
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.
3. -Sedimentation
a Process Description . Sedimentation is a physical pro—
cess whereby particles suspended in a liquid are made to settle
by means of gravitational and inertial forces acting on both the
particles suspended in the liquid and the liquid itself. Basi-
cally, particles settle out of a liquid by creating conditions
in which the gravitational and inertial forces acting on the parti-
cle in the desired direction of settling are greater in magnitude
than the various forces (drag forcei, inertial forces) acting in
the opposite direction. This force differential causes the par-
ticles to travel in the desired direction.
The fundamental elements of most sedimentation processes are:
o a tank or container of sufficient size to maintain
the liquid in a relatively quiescent state for a
specified period of time;
5—16
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0 a means of directing the liquid to be treated into the
tank in a manner that is conducive to settling;
o a means of physically removing the settled particlc from
the liquid (or the liquid 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 when large volumes of liquid are to be
treated.
Depending on the specific process configuration, the settled
particles are either removed from the bulk of the liquid, or 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 con-
taining the settled particles is commonly referred to as Nsludge.M
b. Process Design and Operating Parameters . Because sedi-
mentation 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 acconn odate 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 are often equipped with built—in floccula-
tion 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 periodically scraped by mechanical shovels,
draglines, or 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 equipnent, since many clarifiers
are equipped with separate zones for chemical mixing and pre-
cipitation, flocculation, and settling. Certain clarifiers are
equipped with low lift turbines that mix a portion of the pre-
viously settled precipitates with the incoming feed. The practice
has been show to enhance certain precipitation reactions and pro—
mote favorable particle growth.
5—17
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There are many variations of the sedimentation process,
encompassing a wide variety of commercially available equipment.
4. Precipitation, Flocculation, and Sedimentation Applications
to Hazardous Wastes
The processes of precipitation, flocculation, and sedimenta-
tion are finding widespread application in the treatment of waste—
water streams containing soluble heavy metals and colloidal haz-
ardous substances. A summary of general wastewater treatment
applications in a number of major industries is presented below.
a. Iron and Steel Industry . Wastewater streams from the
iron and steel industry are characterized by a very high con-
centration of settleable suspended particles and a relatively
low concentration of dissolved heavy metals, such as ferric iron,
zinc, lead, chromium, and manganese. Sedimentation is currently in
widespread use for the removal of suspended solids. Precipita-
tion (usually with 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 Industri . Wastewater streams from copper smelting
and refining contain a variety of soluble and colloidal heavy
metals (arsenic, cadmium, copper, iron, lead, mercury) that can
be removed, to varying degrees of effectiveness, by precipita—
tion, flocculation, and sedimentation using either lime or sodium
sulfide.
d. - Metal Finishing Industri . Soluble salts of copper,
nickel, cadmium, and chromium are removed from wastewater streams
by precipitation, for example, by utilizing lime to form insoluble
hydrated oxides followed by flocculation, and sedimentation.
Chromium usually present as chromate or dichromate must first be
reduced to the trivalent state so that the precipitation process
will be effective.
e Inorganic Chemicals Industry . Many manufacturing pro-
cesses within the inorganic chemic&ls industry produce wastewaters
that contain suspended solids and soluble heavy metals. Manufac-
ture of titanium dioxide and chrcinium pigments produce such
wastewaters. Precipitation, flocculation, and sedimentation are
used to treat many of these wastewaters.
f. Sludge Thickening . The first step used in a sludge de—
watering 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 clari-
fier in which the already settled solid particles are allowed to
5—18
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settle further and compact. Typically, the supernatant liquid
is returned to the main clarifier that performs the initial liquid—
5 olid separation, while the “thickened” sludge is drawn off and
either disposed of or sent to further dewatering steps, such as
vacuum filtration or centrifugation.
5. Environmental Considerations
Since precipitation, flocculation, and sedimentation processes
are basically liquid—solid separation processes, two output streams
will result —— ahigh—volume purified liquid stream and a low—
volume slurried solids stream. There are usually no air emissions
from the process. The processes do employ equipment that exposes
large open surfaces of liquid to the atmosphere, and, if that
liquid is other than water and is highly volatile àr contains
highly volatile components, air emissions could result.
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REFERENCES
1. 40 CFR 264.192(a), Subpart J (46 Fed. Reg . 2867
[ January 12, 1981]).
2. Walter J. Weber. Physiochemical Processes for Water
Quality . Chapter 8. New York: Wiley—Interscience, 1972.
3. Nancy J. Cunningham. Physical, Chemical, and Biological
Treatment Techniques for Industrial Waste. Chapter 35. Cambridge,
Mass.: Arthur D. Little, 1976.
4. Metcalf & Eddy, Wastewater Engineering Treatment, Dis-
posal and Reuse , 3rd ed. New YQrk: McGraw—Hill, 1979, Chapter 5.
5. Michael Henthorne, “Understanding Corrosion,” Chemical
Engineering Deskbook , Vol. 79, No. 27, December 4, 1972, P. 19.
6. Gary W. Kirby, “How to Select Materials,” Chemical
Engineering , November 3, 1980, 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 Waste,
Washington, D.C., 1982.
8. Nancy J. Cunningham. Physical, Chemical and Biological
Treatment Techniques for Industrial Waste. Arthur D. Little, Inc.,
Cambridge, Mass., Nov. 1976, Chapter 38.
9. Lawrence N. Davidson, “Physical, Chemical, and Biological
Treatment Techniques for Industrial Waste,” Cambridge, Mass.:
Arthur D. Little, Inc., 1976, Chapter 34.
10. 40 CFR 264 and 265 (45 Fed. Reg . 76074—83 [ Nov. 17, 1980] ).
11. Edmund H. Dohnert. Physical, Chemical, and Biological
Treatment Techniques for Industrial Wastes. Chapter 23. Cambridge,
Mass.: Arthur D. Little, Inc., 1976.
5—20
-------
CHAPTER 6
CLOSURE EVALUATION
Ch apter Outline
A. Closure Requirement
B. Closure Plan Evaluation
1. Disposal Procedures
2. Facility Decontamination Procedures
6—1
-------
CHAPTER 6
CLOSURE
A. CLOSURE REQUIREMENT
The closure requirement for tank facilities (40 CFR 264.197)
states that NAt closure, all hazardous waste and hazardous waste
residues must be removed from tanks, discharge control equipment,
and discharge confinement structures.* Also at closure, as
throughout the operating period, unless the owner or operator
can demonstrate, in accordance with Section 261.3(d), that the
residue removed from his tank is not hazardous waste, the owner—
operator becomes a generator of hazardous waste and must manage
it in accordance with allapplicable requirements of 40 CFR
Parts 262, 263, and 264.
B. CLOSURE PLAN EVALUATION
The tank closure plan must incorporate: (1) procedures for
removing hazardous waste from the tank, (2) disposal of the
removed residuals, and (3) decontamination of the tank itself.
The closure plan must be updated according to relevant facility
changes.
Closure plan data needs and evaluation procedures for the
closure of tank facilities are detailed in the guidance manual
on closure and postclosure (Subpart G). 1 This chapter emphasizes,
therefore, disposal of remaining wastes and residuals at closure
and tank decontamination procedures.
1. Disposal Procedures
The disposal procedures for the remaining waste within the
tank and waste residues should be described. The following
information should be included:
a. volume of waste to be disposed of;
b. method of removal from the tank;
c. processing or treatment method if required prior to
transport or disposal (i.e., neutralize . stabilize, solidify),
advisability of a trial treatment test if the treatmentprocess
is untried for the waste;
d. volume of waste for processing/treatment;
e. volume of waste resulting from processing/treatment.
The closure plan should describe either one of the following
Scenarios and include additional information as noted.
6—2
-------
a. Upon closure, the facility will be operated in a routine
manner for onsite disposal of all remaining hazardous waste and
for waste processing and treatment procedures. For onsite dis-
posal, the final onsite disposal method should be supplied.
b. Upon closure, all waste will be removed and transported
to another hazardous waste treatment, storage, or disposal facility.
For offsite disposal, the following information should be supplied:
O method of transport to disposal site (i.e.,
truck, rail, water);
0 distance of transport to disposal site;
O final disposal method (i.e., facility type, such
as a secure landfill).
If the closure plan calls for a combination of both on— and
off—site disposal, the quantity of waste to be disposed of by
each method must be identified.
2. Facility Decontamination Procedures
At closure, the entire facility should be cleaned, and no
hazardous materials should be left onsite. This includes cleanup
or disposal of contaminated equipment, soils, and residues. The
closure plan should include:
a. methods to test for contamination (laboratory procedures,
kits, mechanical, electrical, or visual methods);
b. areas of facility to be tested or cleaned:
0 tanks and other storage areas;
o all equipment used prior to storage or treatment in
a tank, such as waste feed systems, by—pass systems,
drainage systems, conveyors, containers used for
transport;
O discharge confinemeiit tructures such as dikes;
0 piping, pumps, valves, heat exchangers, compressors;
c. description of the testing, cleaning, and disposal
procedures;
d. disposal methods for decontamirtant solutions and residues;
e. labor force expected to perform decontamination (in—house
or outside contractor).
Preparation steps before testing and cleaning (after the
waste has been drained from the tanks) may include the fo].lowing: 2
6—3
-------
a. ventilation and gas testing;
b. assurances for safe entry and exit;
c. inspcc.tion of safety equipment such as safety belts,
respiratory equipment, and personal protective equipment;
d. removal of all sources of potential ignition of f lam—
jaable vapors such as smoking, welding, internal—combustion engines,
etc., from the area prior to initiating the cleaning operation.
The actual cleaning of tanks may involve the following steps.
These procedures should ensure that hazardous wastes are not
released to the environment and cleaning crews are adequately
protected. 3
a. Removal of Tank Contents. The waste can be pumped to
other storage within the facility or to a tank truck for offsite
handling. Following waste removal, all piping to and from the
tank should be disconnected and dismantled or decontaminated.
b. Removal of Flammable or Toxic Vapors. Displacement
of flammable vapor by nonreactive gas is a safe means to minimize
hazards. The gases commonly used are carbon dioxide and nitrogen.
Both may be obtained in portable form in cylinders and in tank
trucks. Other methods such as displacement with air, steam, or
water can be used when no potential flammable hazard is involved.
c. Removal of Residual Sludges. In some cases it may be
difficult to removal all liquid or solid residues, as these
residues may be trapped behind heavy scale or rust or may be too
viscous for pumping. When an internal inspection indicates that
such a condition exists, steam cleaning or chemical cleaning may
be needed to remove the residues. These two methods are also
useful in decontaminating the tank interior and any associated
contaminated auxiliary equipment. Steam cleaning utilizes
steam to vaporize the residues, and chemical cleaning uses any
of a number of industrial solvents to dissolve the residues.
Testing soils for contamination may or may not be necessary
depending on the facility’s conditions. In the closure plan,
the owner—operator sho’. Ld describe the criteria used to determine
the amount of contaminated soil.
6—4
-------
REFERENCES
1. Draft Guidance for Subpart G of the Interim Status
;taridards for Owners and Operators of Hazardous Waste Treatment,
;torage and Disposal Facilities. (Draft). International Research
tnd Technology Corporation (IR&T), McLean, Virginia, for U.S.
:pA, Office of Solid Waste, Washington, D.C., October 1980.
2. American Petroleum Institute. Guide for Inspection of
efinery Equipment, Chapter V. 3d ed. Washington, D.C., 1978.
“Cleaning Small Tanks and Containers.” National Fire
rotectiOn Association, NFPA No. 327. Quincy, Massachusetts,
975.
6—5
-------
CHAPTER 7
HAZARDOUS WASTE TANK COSTS
The types of tanks to be used in the handling and processing
of hazardous waste depends principally on the chemical composi-
tion of the wastes. For example, highly corrosive wastes would
probably have to be stored in tanks made of fairly inert material
such as fiberglass. On the other hand, noncorrosive wastes
containing toxic materials such as lead or mercury may be stored
in steel or concrete tanks.
There are generally 11 types of steel, concrete, wood, or
fiberglass tanks presently available from manufacturers.. They are:
1. prestressed concrete tanks;
2. ground—level steel tank;
3. steel tanks with standpipes;
4. elevated steel water tanks;
5. fixed—roof oil storage steel tanks;
6. floating—roof gasoline steel tanks;
7. wood tanks, ground level;
8. underground steel tanks;
9.. underground fiberglass tank
10. expansion tanks (ASME); and
11. water tanks .with cypress roofs.
Although all of these tanks are not necessarily used for
storing hazardous waste, they are included to indicate costs for
various sizes and Ltypes of tanks. Table 7—1 presents cost data
for the ditferent types and sizes of tanks. These costs are to
be used fo. general comparison purposes and not to prepare
engineering design estimates. The total estimated cost for the
tank includes material, installation, and manufacturer’s overhead
and profit; the estimated cost does not include piping, pumps,
and foundations. In addition, a 10 percent markup is assume’.i
on all equipment. Figure .7—1 is a graphic representation of
the cost of steel and concrete tanks by type and capacity. The
smaller capacity fiberglass tanks are shown in Figure 7_2.1
Cost data for two types of stainless steel tanks, Types 304
and 316, are presented in Figure 7—3. Included in the prices shown
are standard nozzles (manhole cover and coupling connections). 2
7—1
-------
TABLE 7-1
COST DATA FOR TANKS BY
TYPE AND
CAPACITY
(1979)
Type
Capacity
(thousand gal
ions)
($
Total
thou
Cost
sands)
prestressed concrete 250 110
500 180
1,000 260
2,000 390
4,000 620
6,000 850
Ground—level steel tanks 100 so
250 .60
500 100
750 140
1,000 230
2,000 320
4,000 560
6,000 1,010
8,000 1,130
Steel tanks with standpipes,
100 feet to overflow 500 160
750. 200
1,000 240
1,500 330
2,000 410
Elevated steel water tanks, 100
feet to bottom capacity line 50 110
100 140
250 190
500 310
750 440
1,000 550
Fix& —roof oil storage steel
tank 210 50
1,050 130
2,310 220
4,200 360
6,300 510
9,450 730
7—2
-------
TABLE 7—1 (cont.)
Capacity Total Cost
Type (thousand gallons) (S thousands)
Floating—roof gasoline 210 60
steel tanks 1,050 l80
2,310 270
4,200 430
6 300 570
9,450 810
Wood, ground level, 2 inches,
cypress 30 5
Wood, ground level, 2 1/2
inches, cypress 10 122
Wood, ground level, 3 inches,
redwood or fir 20 16
30 20
45 25
Steel, underground, coated, 1, 7 gauge shell
5, 14 thick shell 3
10, 14 thick shell - 4
10, 5/16 thick shell 5
20, 5/16 thick shell 9
30, 3/8w thick shell 150
Fiberglass, underground, not 2 34
including manways or hold— 4 49
down straps 6 51
.8 61
10 75
12 90
15 11
20 14
* This information is copyrighted by Robert S. Means Co. It
is reproduced, with permission, front Mechanical and Electrical
Cost Data —— 1979 .
7—3
-------
FIGURE 7 -1
TANK COST DATA BY TYPE AND CAPACITY
cost
$ooo
)Ol0
960
seo
800
I I I I I I
IiROUND lEVEL ]
‘LSTw TAt1K 5J —
,1____ _
/
:1
640
V
1 RESTRtS F 1)
L ” ’ IMP’
I-
/
, /
—/ -
•0
-ø
ELEVATED STEEL
WATEN TAP4I(S -
tOO list tobotlom
copocil tins
V
i
/
‘I
/
/
74
/
7
2
-
—
—
—
—
—
FLQATINQ R00 -
ST EELTANP S -
i E E
/
I -
480
400
320
240
/
STEE.11AP4 1(S
with slnndptpsi
tOOlsel toove,lto,v
yl
— —————-—-- ——.- -
FIXED NOOF
OIL S1DNAGE
STEEL TANKS
7
L
.4
/
/
/
— --— — ———p . .-————
—— - - -- ø --
0
/
V
S
7
I —
-ø
F.-
, - V
S
5.0 m.o 15.0 20.0 25.0 30.0
35.0 40.0 45.0 50.0 55.0 60.0
CAPACITY (100,000 Gallon .)
65.0 70.0 75.0 80.0 850 90.0 95.0 moo
Sour •e M.thnnkn ondE stIrlcoI CosI DoIo—S979,
R.b.wl ‘ ‘ ‘
-------
FIGURE 7—2
COST(DOLLARS)
FIBERGLASS TANK COST DATA BY CAPACITY
e,ooo iopoo it,ooo 4,OOO ,spoo
CAPACITY IBALLONS)
ie,ooo zo,000
In
2,00U
Sowce: M on3 B ffldIn uConsIrucUon Cost DaIa—S900,
-------
FIGURE 7-3
Stainless Steel Tank Cost
Data by Capacity
T 3l6 and T 3O4 are two different types of stainless steel tazics
Source:
Epstein, Lawrence D.”Costs of standard vertical storage
tanks and reactors,” ChemicalEngineering , 88 (14): 141,
July 1981.
I 2 -:3 - 4 ‘.5’ -t —7 8-
- -- 1,XO
7-6
-------
The tanks with the largest capacity are floating— and fixed—
roof steel tanks. Capacities for these tanks range from approxi—
inately 200,000 gallons to nearly 9,500,000 gallons. Fiberglass
tanks, on the other hand, seldom exceed a maximum capacity of
20,000 gallons.
There are numerous types and sizes of pipes that may be used
in conjunction with tanks. The choice of a particular type of
pipe is a direct function of the type and quantity of waste being
handled. For example, an aluminum pipe may be inappropriate for
a highly acidic waste. Instead, a more expensive corrosion—
resistant pipe may have to be used. In addition, if the tank
holds large volumes of waste, pipes of greater diameter will
have to be used. Therefore, the type and quantity of hazardous
waste handled by the tank will determine the particular type
and size of the pipe to be used and, consequently, the cost. In
general, piping costs at a tank farm facility can range as high
as 50 percent of the total facility cost.
The above discussion has focused on the essential components
of hazardous waste tanks, namely, the material and installation
costs of the tanks. Other costs that should be considered
include: the cost of pumps (e.g., material and energy costs),
the cost of site preparation (e.g., foundation, construction, and
labor costs), and other costs such as for vapor—recovery systems.
These costs may vary significantly with the type of tank used
and the geographical location.
7—7
-------
REFERENCES
1. Mechanical and Electrical Cost Data —— 1979 . Robert S.
Means Co., Kingston, Massachusetts, 1979.
2. Lawrence D. Epstein. “Costs of Standard Vertical
storage Tanks and Reactors.” Chemical Engineering , 88 (14):
141, July 1981.
7—8
-------
APPENDIX A
TYPES OF TANKS USED FOR HAZARDOUS WASTE STORAGE
A. ATMOSPHERIC ABOVE—GROUND, COVERED TANKS 1
Atmospheric tanks are used to store liquids having internal
vapor pressure approximating atmospheric pressure at ambient
storage temperatures. Vapor pressure is the pressure exerted
by the vapors of that liquid. Pressure varies with temperature.
Atmospheric tanks are equipped with vents that are designed to
balance the inside pressure and outside atmospheric pressure to
within a few ounces. per square inch to preclude rupture. Numerous
types of atmospheric tanks are described in the following sections.
1. Fixed—Roof Tank
A fixed—roof tank has a nonmovable roof. The simplest type
is the cone—roof as shown in Figure 1. These tanks may be as
large as 250 feet in diameter and 60 feet in height. A cone—roof
tanks has two common variations, the umbrella—roof tank (Figure 2)
and the dome—roof tank. The umbrella roof has segmental plates
placed on meridian center lines; the dome roof has spherically
curved roof plate segments.
2. Floating—Roof Tank
A floating—roof tank has a roof that floats above the surface
of the stored liquid. The floating roof serves to reduce evapora-
tion loss by maintaining a constant vapor space above the stored
liquid. Some examples of floating—roof tanks are the pan, the
annular—pontoon, and the double—deck, as shown in Figures 3, 4,
and 5, respectively. The cross—sectional views are shown in
Figure 6. The floating—roof and the tank wall are sealed by a
shoe or plate pressed against the wall by springs, connected with
a flexible membrane. An example of a seal is shown in Figure 7.
3. Covered Floating—Roof Tank
A covered floating—roof tank has a fixed roof combined with
a steel pan floating roof inside. The fixed root is usually a
cone. These tanks are often built in heavy snowfall areas where
an open—top floating roof may be insufficient to handle the load.
4. Var ia,le—Vapor—Space Tank
A variable—vapor—space tank has a gas—holder device that can
temporarily store expanding vapors. The lifter roof and the
flexible diaphragm, shown in F gures 8 and 9, respectively, are
the coimnon types.
A-l
-------
Guide for Inspection of Refinery Equipment,
Chapter XIII, 3rd ed., Pub. no. 821-00013,
p. 8, reprinted by courtesy of the Mierican
Petroleum Institute.
-
— — .- - - _ . -
TIC. 1 -Co...Rs.f T, nk.
ThH
FIG. a—.u b,.a..aøo Tank.
-------
Court y G aL A ccica Tran3porta on Corp.
flG .3 .—.Paa.T7p. F1o.dn ( East.
Evaporation Loss in the Petroleum Industry, API Bulletin 2513, 1959, p. 17,
reprinted by courtesy of the American Petroleum Institute.
r2 ) H 11
-------
- -
‘I
1
— .v•T._ .—
— V..
k
I. - T t - : • -4
- -r - V-’ - . -
— - - —- -
- - — -
— - --- -i- _ — -
—r -‘ ‘- •- --- —
— - — — —
-
- d.2 .
ourte y: Chi go Bridge and Iron Company.
FIG. 4 —Po.io..-Typ. flostiag Root.
Evaporation Loss In the Petroleum Industry, API Bulletin 2513, 1959, p.17,
reprjnt d by courtesy of American Petroleum Institute.
-------
-
— - - -
- —
:‘ ;- --
•1 ET J 2 I
Hamn2oa hon WorkL
TIC ’. 5 —Dos.bi. .Dsck flosignE Root.
Evaporation Loss In the Petro1eum Industry, API Bulletin 2513, 1959, p. 19,
reprinted by courtesy of the American Petroleum Institute.
-------
00U81E DECK FLOATING ROOF
FIG. 6—Cre.s-S eskns Sk.IcIse. .1 FIoath.gIIo.f Tank. Showing sko Moss beiporisna F.ss.sra.
Guide for Inspection of Refinery Equipment, Chapter xiii, ir’d ed . , p. 9, reprinted by courtesy of the
American Petroleum Institute.
‘AN FLOATING ROOF
PONTOON FLOATING ROOF
*UlOMdsC kUD * W14
$00 1 MaNO$1
-------
Guide for Inspection of Refinery Equipment,
Chapter XIII -, 3rd ed., p. 10, reprinted by
courtesy of the American Petroleum Institite.
TIC. 7—fl..d..a..1 5.sl Ua Coal 5p,1ngi _____
t S I.
-------
-. --—-
- - -. - --. - — . - .-- - — :. .•
- .
- — — — 1 _ —
- • -- ••
I, I I ! - * —r I
TIC & —Wt o.I Ta.k.
tide for Inspection of Refinery Equipment, Chapter XIII, 3rd e ., ‘uD. no. 821—3C013,
11, reprInted by courtesy of the Amen can Petrol eum Instl tute.
- _•J
-------
Evaporation Loss in the Petroleum Industry,
API Bulletin 2513, 1959, p. 21, reprinted
by courtesy of the Amen can Petrol eum
Institute.
Cour y: Hammond Iron Worlu.
FIG. 9 L. .DIspkra Tank (IntegraL Unit).
-------
5. Lifter—Roof Tank
A lifter—roof tank can have either a wet seal or a dry seal,
and the roof can move up or down the tank shefl as the vapor space
expands or contracts. A typical design of the wet—seal lifter
roof includes an annular space surrounding the shell containing
a sealing liquid inside. The seal liquid can be water, light
oil, or antifreeze depending on the climate, liquii solubility,
and tank design. The actual seal is provided by a dip skirt
that extends from the roof into the liquid. A dry—seal lifter
roof design, as shown in Figure 10, is similar to the wet—seal
design (Figure 11). It has rubber or dry seal instead of Liquid.
6. Flexible—Diaphragm Tank
A flexible—diaphragm tank can be either a separate nit or
an integral unit. It is essentially a fixed—roof tank with a
flexible diaphragm attached to the inside of the shell. The
diaphragm expands or contracts with the vapor volume.
7. Breather—Roof Tank
Breather—roof tanks provide expanded vapor space without
using a loose external roof. Sane examples of. breather—roof
tanks are the plain, balloon—roof, and vapor—dane tanks. A plain
breather—roof and a balloon—roof tank, as shown in Figures 12
and 13, respectively, have flexible steel roofs capable of moving
up and down within narrow limits. The balloon roof is capable
of providing a greater’change of volume. The vapor—dome roof
tank has an added fixed dome with a flexible membrane attached
to the wall inside. The membrane can be moved flexibly to provide
changes in volume.
8. Plain Cylindrical Tank
A plain cylindrical tank is used to store small quantities
of liquid at atmospheric pressure (see Figures 14 and 15). It
usually has a flat head and can be placed either vertically or
hor izontally.
B. LOW—PRESSURE ABOVE—GROUND, COVERED TANKS
Low—pressure tanks are used to store liquids having a vapor
pressure up to 15 psig at ambient temperatures. Two types of
low—pressure tanks are described below.
1. Bemispheroidal Tank
A hemispheroidal tank is similar to a cone—roof tank except
that the bottom and top are curved to withstand pressure. Plain
and noded hemispheroidal tanks are shown in Figures 16 and 17.
A—b
-------
-
4 d: _
- -
— -; -
-
J i1
if — --
-
,.— ! —
rt
•
4,- - ____
: - - & -- _____
r ____
. :—
4’L C kf
c ii 1-i
FIG. 10 —Dry.SsaI Lift., Roof.
Guide for Inspectior of Refinery Equipment,
Chapter XIII, 3rd ed., Pub. no. 821-00013,
p. 12, reprinted by courtesy of the
American Petroleum Institute.
.1
A.
I
)
— :
-------
curtcsy: Graver Tank and Manufacturing Company, Inc.
Evaporation Loss in the Petroleum Industry, API Bulletin 2513, 1959, p. 20,
reprinted by courtesy of the .ftmerican Petroleum Institute.
PIG.Il —Vet -Seal Lifter Roof.
-------
*QOV P .ATt
, To
$.IVELL CONNECTZOY
s tTc
Guide for Inspection of Refinery Equipment, Chapter XIII, 3rd ed., Pub. no. 821 . OOO13
p. 12, reprinted by courtesy of the American Petrol eum Insti tute.
FIG. 12—Plain Bre,*k.r.Roof Tank.
-------
FIG. IS —B.rfzo.eal Tank (W.1d. ) Ssppart.d on Co.a t. Cr.dI .
Guide for Inspection of Refinery Equipment, Chapter XIII, 3rd ed., Pub. no. 821-00013,
p. 14, reprinted by courtesy of the American Petroleum Institute.
.L
-------
HIGH UQUID LEVEL.
Guidefor Inspection of Refinery Equipment, Chapter XIII, 3rd ed., pp. 14—15,
reprinti d by courtesy of the American Petroleum Institute.
FIG. IS —PlajA Rs i.pbo dm.
£LZYATION SiCT1ON
PLAIN
NODED
FIG. 17 —Draw&ng, of H &spb oids.
S ICT1ON
-------
Guide for Inspection of Refinery Equipment, Chapter XIII, 3rd ed., p. 16, reprinted
by courtesy of the American Petroleum Institute.
F IG. I8 —PbAn Spheroidal Tank.
FIG 19 —Nided Spheroidal Tank.
-------
2. Spheroidal Tank
Spheroidal tanks are used under the same conditions as hemis—
pheroidal tanks and are normally used for the storage of large
volumes (see Figures 18 and 19).
C. UNDERGROUND TANKS
Underground tanks are used most frequently for small bulk
storage and are often horizontally, cylindrical in shape. The
major advantages of underground storage are safety and aesthetics.
Corrosion of underground steel tanks has been a disadvantage in
the past, but proper corrosion protection is now feasible with
cathodic devices or special coatings. Another disadvantage is
the difficulty in determining tank leakage and the consequent
danger of ground—water contamination. Polyester— and fiberglass—
reinforced tanks are commonly used underground and are priced
competitively with steel tanks. The permit requirements currently
exclude the use of covered underground tanks that cannot be
entered for inspection for treatment or storage of hazardous
waste.
D. UNCOVERED TANKS
Uncovered tanks and basins can be used to store hazardous
wastes that are relatively nonvolatile. Ground—water contamina-
tion is a major consideration in the evaluation of basins.
A—17
-------
REFERENCES
1. American Petroleum Institute. Guide for Inspection of
Refinery Equipment, Chapter XIII. 3d ed. Washington, D.C.,
1972.
2. American Petroleum Institute. Bulletin 2513. Evaporation
Loss in the Petroleum Industry —— Causes and Control. Washington,
D.C., 1973.
A-18
-------
APPENDIX B
SUBSURFACE AND FOUNDATION CONSTRUCTION
A. SITES REQUIRING SPECIAL CONSIDERATIONS
When facilities are constructed in the following areas, they
require special structural considerations: 1
o hillside sites, where part of a tank may be on undisturbed
ground or rock and part on fill or other material, or
where the depth of required fill is variable;
sites on swampy or filled ground, where layers of muck
or compressible vegetation are at or below the surface,
or where unstable or corrosive materials may have been
deposited as fill;
o sites over layers of plastic clay, which may temporarily
support heavy loads but may settle excessively over long
periods of time;
o sites adjacent to water courses or deep excavations,
where lateral stability of the ground is questionable;
o sites immediately adjacent to heavy structures, which
distribute some of their load to the subsoil under the
tank site, thereby reducing its capacity to carry the
additional load without excessive settlement;
o sites where tanks may be exposed to floodwaters, which
could result in possible uplift, displacement, or scour.
If the subgrade is weak or inadequate to carry the load of
a full tank, construction under the tank bottom is necessary. One
or more of the following general methods may be used:
0 remove the objectionable material and replace it with
other suitable and compact material;
0 compact the soft material with short piles or by pre—
loading with overburden of earth or other material
suitably drained;
° compact the soft material by draining off the water,
if practicable;
o stabilize the soft material by chemical methods or
injection of cement grout;
° drive bearing piles or construct foundation piers to
serve as a reinforced slab on which to distribute the
load of the tank.
B-i
-------
Fill material used to replace objectionable materials and to
build a suitable base (e.g., td build up the grade to a suitable
height) should be of high quality. It should be free of vegeta-
tion 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.
B. FOUNDATION TYPES 2
When the properties of the underlying soil are inadequate to
supportthe load of a full tank, a foundation 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 important when the facility
location is in an earthquake zone, a marshy area, or an otherwise
unstable area.
C. EARTHEN FOUNDATIONS 1
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 require-
ments for an earthen foundation are identical tO those associated
with artificial material foundations. Specifically, the foundation
should:
O provide a stable plane for the support of the tank;
o limit overall settlement of the tank grade to values
compatible with allowance provided in the design for
connecting piping; and
o provide adequate drainage.
D. TANK GRADES 2
It is suggested that the tank be constructed above the surface
of the surrounding around. This will provide for suitable drainage,
help keep the bottoiñ of the tank dry, and, even if some settlement
occurs, elevate the tank above the surrounding surface.
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.
Where fill beneath the tank is likely to wash oLt in the event
of a bottom leak, 1/2 to 1 inch of gravel is recommended for a
minimum depth of 3 inches. During construction, 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.
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In order to preserve the contour during construction and to
protect the tank bottom against ground moisture, the finishied
grade may be oiled or stabilized-in someother manner. Caution
should be exercised in assuring that quantity or kind of material
used for this purpose does not create welding difficulties or a
risk of galvanic corrosion.
It is suggested that the finished tank grade be crowned from
the outer periphery to the center. A slope of 1 inch in 1.0 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.
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REFERENCES
1. American Petroleum Institute. Standard 650, Welded Ste 1
Tanks for Oil Storage. Appendix B, 6th ed. Washington, D.C., 1979.
2. American Petroleum Institute. Guide for Inspection of
Refinery Equipment. Chapter XII. 2d ed. , Washington, D.C., 1975.
B—4
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APPENDIX C
TANK ANCILLARY FEATURES
A. PUMPS 1 -
Pumps are necessary for all tank storage/treatment facilities.
The cost of pumping can be a major factor in plant design and
op er a t ion.
There are three broad classes of pumps: centrifugal, rotary,
and reciprocating. Table 1 summarizes pump classes and types..
Several factors must be considered when selecting a pump to
handle hazardous wastes. These factors include: capacity, pump
head, nature of liquid handled, cost, and materials of construction.
1. The pump capacity requirement is determined by the
liquid volume to be handled. A design safety factor is needed
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
material.
4. Cost factors in part dictate the pumping scheme or type
of pump acceptable to a facility. Comparison of cost factors may
allow the owner—operator 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. Factors include corrosion—erosion re-
sistance when transporting acids, alkalies, slurries, and other
liquids; ease of installation, operation, and maintenance; and
dependability. For example, a typical centrifugal pump for
handling acid and slurry can be made of materials such as lead,
stainless steel, solid plastic, or solid rubber. When special
designs are not required, rut.oer, teflon, or neoprene base
coverings are available for the casing and impeller.
The permit writer is referred to an enginering textbook 2
for illustrations on pump head and power requirements.
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TABLE C—i
PUMP CLASSES AND TYPES
CLASS TYPE
Centrifugal Volute
(Single—stage and multistage) Diffuser
Regenerative—turbine
Vertical—turbine
Mixed—flow
Axial—flow (propeller)
Rotary Gear
Vane
Cam and piston
Screw
Lobe
Shuttle—block
Reciprocating Direct—acting
Power (including crank—
and fly wheel)
Diaphragm
Rotary—piston
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B. FITTINGS
Valves are fi.ttings that serve to regulate the flow of
fluids and isolate piping for maintenance without interfering
with the normal operation. The selection of fittings to handle
hazardous wastes is primarily based on the compatibility of the
construction materials with the wastes (see Section 5). The
permit writer is referred to References 2 and 3 for details on
fittings.
C • HEAT EXCHANGERS
Heat exchangers are devices that are used to transfer heat
from one fluid to another. Design variations are numerous, but
always consist of the transfer of heat from a hot phase to a
cold phase with the two phases separated by a solid boundary.
Shell and tube heat exchangers are probably the most commonly
used types of exchangers. The design is usually based on the
Tubular Exchanger Manufacturers Association (TEMA) standards. 4
The American Petroleum Institute’s Standard 66O supplements
TEMA standards for refinery services. The permit writer is
referred to References 2, 3, and 4 for drawings and required
heat transfer area determinations.
D. COMPRESSORS 2 ’ 3
There are two kinds of compressors: positive—displacement
and centrifugal. Reciprocating and rotary compressors are posi-
tive—displacement types. Fans and blowers are centrifugal com-
pressors. Fans and blowers operate at low pressure so that gas
volume compression at inlets and outlets is essentially equal.
Fans are simply movers of gas. They are classified by the direc-
tion of air flow: radial, centrifugal, or axial.
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REFERENCES
1. T.G. Hicks and T.W. Edwards. Pump Application
Engineering . New York: McGraw—Hill, 1971.
2. Principles of Unit Operations . New York: John Wiley
and Sons, 1960.
3. R.H. Perry and C.H. Chilton, eds. Chemical Engineers’
Handbook . 5th ed. New York, McGraw—Hill, 1973.
4. Tubular Exchanger Manufacturers Association Standards.
5th ed. New York, 1968.
5. American Petroleum Institute. Standard 660. Heat
Exchangers for General Refinery Services. 2d ed. Washington,
D.C., 1972.
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APPENDIX D
A2PURTENANCES AND SAFETY EQUIPMENT
In general, tanks at hazardou. waste facilities should be
equipped with process process nozzles, service nozzles, and
safety equipment.
1. Inlets and Outlets
o inlet nozzles must be adequate to handle the incoming
waste at the. design linear velocity;
o outlet nozzles must be adequate to handle outgoing
waste at the design linear velocity;
o vent connections (depending on the type of tank) must
be able to maintain the pressure of the tank according
to tank specifications, such as atmospheric or low
pressure;
o overflow connections (to prevent tank bursting) must
be equal or larger than the inlet nozzle;
o drain connections should be located at the bottom of
the tank to allow for emptying the tank’s contents
by gravity.
The sizing of process nozzles depends on the properties of
the fluid handled. Properties to be considered include:
o percent of solids by weight;
o volumetric flow rate;
0 minimum and maximum linear velocity; and
o pressure drop at the entrance and the exit of the nozzle 1 .
Tanks are equipped with several instrument nozzles that
provide conduits for measuring devices and indicators.
2. Instrumentation
° high liquid level (ULL), which indicates when the liquid
level has reached the design capacity of the tank;
o low liquid level (LLL), which indicates when the liquid
level has reached the low mark of the design capacity;
° level alarm —— high (LAH), which indicates when the
liquid has reached the dangerous level. If the situation
is not rectified, the waste will overflow from the tank.
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° level alarm low (LAL), which indicates when the liquid
level has reached the dangerous level. If the situation
is not rectified, pump cavitation can occur because of
pumping air instead of liquid.
Level indicators/controllers are illustrated in Figures 3—2
and 3—3 of the text. The time needed to fill the tank from LLL
to ELL is called the retention time of a tank. The working or
design capacity of the tank is equal to the volumetric flow rate
(gallons per minute) times the retention time. The volume of
waste stored in a tank should not exceed the tank design capacity.
3. Service Ports
o manway to provide entrance into a tank to perform
inspection and maintenance work;
o temperature indicator port;
o pressure gauge port;
o sampling port.
Temperature and sampi-ing ports are located at a point that
is representative of conditions within the tank. Usually, they
are located slightly above the expected LLL of the tank.
4. Safety Equipment
° pressure safety valves are designed to open when the
pressure exceeds a predetermined level to. preclude
rupture of the tank. Common types of pressure safety
valves include pilot—operated relief valves, pressure
relief valves, or pressure vacuum valves.
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APPENDIX E
SECONDARY CONTAINMENT
Currently, EPA’s h zardous waste regulations do not require
a secondary containment system for tanks that treat or store
hazardous waste. These systems are, however, effective means
for detecting and containing leaks and spills and are included
in the design of many facilities. Some types of secondary con-
tainment are:
o runoff and leachate collection systems;
0 peripheral diking systems; and
0 liner systems.
Runoff and Leachate Collection Systems . These systems should
be constructed of materials compatible with the waste and should
be designed to include:
0 a slope of greater than 1 percent away from the tank
or the collection point;
0 a collection point where runoff or precipitation can be
routed so that it can be removed;
0 capacity equal to the volume of the largest tank or 10
percent of the volume of all the tanks in the contain-
ment system and allowance for preciptation; and
o sufficient freeboard for sumps (if applicable)..
Peripheral Dike Systems . Peripheral drainage collection
can serve two purposes: it can prevent precipitation from en-
tering 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;
O walls that are designed to be liquid tight and to with-
stand a full hydrostatic head. The slope of earthen walls
should be consistent with the soil’s angle of repose;
0 piping (which passes through dike walls) that is liquid
tight and designed to prevent excessive stresses as a
result of settlement;
0 relatively impermeable ground within the dike area to
preclude ground—water or surface—water contamination;
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o 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 d’rained
utilizing a portable pump may be installed;
o diked area should be kept free of drums, debris, etc.
For structural stability purposes, earthf ill dikes should
have side slopes of horizontal to vertical no greater than 2 to
1,. Additionally, a cutoff joining the base of the dike with
the underlying soil is recommended to “key” the dike into the
indigenous soil.
Liners . A liner is a continuous layer of natural or man-
made materials, beneath or on the sides of a containment system,
that restricts the downward 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:
o degree of impermeability (and thickness) required;
o hydraulic head of waste;
o availability of the material;
o costs.
See EPA ’s technical resource document titled Lining of Waste
Impoundment and Disposal Facilities 3 for further information on
liners.
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REF
1. “Flammable and Combus
Protection Association, NFPA 3C
1980.
2. Oil spill prevention
review. A training program p1
sity, the Universities of Texa
mental Protection Agency. The
3. Lining of Waste Impc
Office of Water and Waste Man
September 1980.
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