In-Process
Pollution
Abatement
Upgrading Metal-Finishing
Facilities to Reduce Pollution
EPA Technology Transfer Seminar Publication
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EPA 625/3-73-002
IN-PROCESS POLLUTION ABATEMENT
Upgrading Metal-Finishing Facilities
to Reduce Pollution
US EPA
Headquarters and Chemical Libraries
EPA West Bldg Room 3340
Mailcode 3404T
1301 Constitution Ave NW
Washington DC 20004
202-566-0556
ENVIRONMENTAL PROTECTION AGENCY* Technology Transfer
Repository Material
Permanent Collection
July 1973
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ACKNOWLEDGMENTS
This seminar publication contains materials prepared for the
U.S. Environmental Protection Agency Technology Transfer Program
and presented at industrial pollution-control seminars for the metal-
finishing industry.
The introduction and chapter I of this publication were prepared
by Alan E. Olsen, Director, Environmental Services Group, Oxy
Metal Finishing Corporation, Madison Heights, Mich. Chapters II
and III were prepared by Edward N. Hanf, General Sales Manager,
Air Pollution Control Division, The Ceilcote Company, Inc., Berea,
Ohio.
NOTICE
The mention of trade names of commercial products in this publication is
for illustration purposes, and does not constitute endorsement or recommenda-
tion for use by the U.S. Environmental Protection Agency.
Revised January 1974
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CONTENTS
Page
Introduction 1
What Is Metal Finishing? 1
Type of Metal Finishers 2
Chemicals and Basic Materials Used in the Metal-Finishing Industry 2
Chapter I. Water-Pollution Control 7
Introduction 7
Processing Equipment Used in the Metal-Finishing Industry 7
Some Methods for Reducing or Eliminating Chemical
Waste in Metal Finishing 8
Planning to Prevent Pollution Catastrophes 12
Water-Conservation Techniques 13
Updating Metal Finishing and Pollution Control at Company X 18
References 22
Chapter II. Ventilation and Air-Pollution Control 41
Introduction 41
Ventilation 42
Air-Pollution Control Devices 47
Conclusion 53
References 54
Chapter III. Corrosion Protection of Floors and Equipment 57
Floor Protection 57
Protection of Equipment 59
Other Considerations 59
Appendix A. Examples of Ventilation Systems Using Air-Pollution-Control Devices 61
Appendix B. Examples of Floor Protection Coating Applications 65
111
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INTRODUCTION
The threat of air and water pollution to the welfare of the United States has been recognized
only in recent years. The task of determining just how industrial wastes adversely alter the environ-
ment is still fraught with unknowns, because this work also has just begun.
Clear to the metal-finishing industry is the fact that its wastes are detrimental to the environ-
ment. The industry wonders about the extent of the detriment, the reasoning behind regulatory
correctional measures, and the steps that industry must take to make permanent peace with the
environment and still continue to use it.
This paper intends only to assist the metal finisher to understand where his pollution begins
and how to reduce it, and, having done so, to have a proper assemblage of facts accumulated so
that his future endeavors at pollution control are not just self-serving, but technologically sound
and not inclined to obsolescence.
WHAT IS METAL FINISHING?
Metal finishing is used to improve the surface of a basic material by
• Cleaning it
• Hardening or softening it
• Smoothing or roughening it
• Depositing another metal on it by chemical exchange
• Electroplating another metal or series of metals on it
• Converting its surface by chemical deposition
• Coating it with organic materials
• Electrocoating it with organic materials
• Oxidizing by electrolysis
These processes are known more familiarly as cleaning and pickling, annealing, case hardening,
polishing, buffing, immersion plating, electroplating, phosphating, conversion coating, oxidizing,
painting, electropainting, and anodizing.
The corresponding changes produced by these methods of metal finishing on the basic material
serve to enhance the value of the treated item by providing such improvements as
• Corrosion resistance
• Durability
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• Esthetic appearance
• Electrical conductivity
Such processes also fill many special engineering requirements of industry such as stress relief,
ductility, heat resistance, or the ability to stamp and form metal objects.
TYPE OF METAL FINISHERS
The metal-finishing industry may be considered in three segments: large captive shops, small
captive shops, and job shops.
The large captive shop is usually a division of, or operated by, a major manufacturer whose
product requires metal-finished items in quantity. These shops are to be found generally in the
automotive and appliance industries and are noteworthy because of the size of their metal-finishing
facilities and the magnitudes of their daily production and chemical consumption.
The small captive shops are usually minor adjuncts to their parent industries. Their roles are to
supply metal-finished incidentals to the principal products. An example of this type of captive shop
might be found in the machine-tool industry or in many of the sports equipment manufacturing
companies.
Where large corporations find it impractical to maintain their own captive metal-finishing opera-
tions, the job shops serve as sources for satisfying their requirements for metal-finished parts.
The job shops exist solely on profits accrued from metal finishing. Jobs are accepted for metal
finishing on contract, and the job-shop owner must be prepared to serve a variety of industries.
His role does not end with the finishing of his customer's wares. For survival, he is required to
keep abreast of all changes in metal-finishing technology and his products' end-use requirements,
thus serving his customers as supplier, inspector, and counsel—a role that the customers themselves
are loathe to countenance technically or endure financially.
CHEMICALS AND BASIC MATERIALS USED IN THE
METAL-FINISHING INDUSTRY
The list of chemicals shown in table 1 is not guaranteed to be comprehensive; it represents the
great majority of potential pollutants with which we are concerned as we consider plant waste-control
planning.
The types and quantities of materials and chemicals purchased furnish an excellent key to pre-
diction of the process effluent characteristics. They also act as cross-checks on the accuracy of
effluent analyses. An attempt has been made to indicate the expected environmental impacts of
these materials when they become waterborne and airborne.
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Table 1.-Some chemicals used in the metal-finishing industry
Chemical
Aluminum potassium sulfate
Aluminum silicate
Ammonium acetate
Ammonium bifluoride
Ammonium chloride
Ammonium citrate
Ammonium hydroxide
Ammonium molybdate
Ammonium nitrate
Ammonium sulfate
Anisic aldehyde
Antimony potassium tartrate
Barium carbonate
Barium sulfate
Benzene (benzol)
Boric acid
Cadmium cyanide
Cadmium sulfate
Calcium nitrate
Chromic acid
Citric acid
Cobalt carbonate
Cobalt sulfate
Cupric sulfate
Diammonium phosphate
Ferric nitrate
Fluoboric acid
Formaldehyde
Glue
Glycerine
Hydrazine sulfate
Hydrochloric acid CP
Hydrofluosilicic
Hydrogen peroxide
Hydro xyacetic acid
Hypophosphorus acid
PH
adjustment
required
X
X
X
X
X
X
X.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cyanide
or
chromium
treatment
required
X
X
Waste products1
MS.DS
MS, DS
DS, NH3
MS, DS, NH3
DS, NH3
DS,NH3,0
DS, NH3
MS, DS, NH3
DS, NH3
MS, DS, NH3
0
MS, DS, 0
MS
MS
0
DS
MS, DS
MS.DS
DS
MS, DS
DS,0
MS
MS.DS
MS, DS
MS, DS, NH3
MS, DS
MS.DS
0
0
0
DS
DS
MS, DS
DS.O
MS.DS
'MS = metal sludge; NH3 = ammonia; DS = dissolved solids; O = organic matter.
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Table 1 .—Some chemicals used in the metal-finishing industry—Continued
Chemical
Indium su If ate
Iron oxide
Isopropanol
Lard oil
Lead f luoborate
Lead oxide
Lime (calcium hydroxide)
Magnesium sulfate
Manganese carbonate
Manganese sulfate
Methanol
Monoammonium phosphate
Nickel carbonate
Nickel chloride
Nickel sulfate
Nickel sulfamate
Nitric acid
Oxalic acid
Phosphorus acid
Potassium bromate
Potassium citrate
Potassium chloride
Potassium copper cyanide
Potassium cyanide
Potassium ferricyanide
Potassium hydroxide
Potassium phosphate
Potassium stannate
Potassium thiocyanate
Sodium acid pyrophosphate
Soda ash (sodium carbonate)
Sodium bicarbonate
Sodium bisulfite
Sodium bifluoride
Sodium citrate
Sodium copper cyanide
PH
adjustment
required
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cyanide
or
chromium
treatment
required
X
X
X
X
Waste products1
MS, DS
MS
0
O
MS, DS
MS
MS
MS, DS
MS
MS, DS
O
MS. DS, NH3
MS
MS. DS
MS, DS
MS, DS
DS
MS, DS
MS, DS
DS
DS, 0
DS
MS, DS
MS, DS
MS.DS
DS
MS, DS
MS, DS
DS
MS.DS
DS
DS
DS
MS.DS
DS, 0
MS.DS
1MS = metal sludge; NH3 - ammonia; DS - dissolved solids; O = organic matter.
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Table 1 .—Some chemicals used in the metal-finishing industry—Continued
Chemical
Sodium cyanide
Sodium dichromate
Sodium f luoborate
Sodium gluconate
Sodium hexametaphosphate
Sodium hypophosphite
Sodium Hydrosulfite
Sodium hydroxide (caustic soda)
Sodium metasilicate
Sodium molybdate
Sodium nitrate
Sodium orthosilicate
Sodium polysulfide
Sodium stannate
Sodium sulfate
Sodium sulfide
Sodium sulfite
Sodium tripolyphosphate
Stannous fluoborate
Stannous sulfate
Stearic acid
Sulfamic acid
Sulfur (liquid)
Su If uric acid
Tallow glyceride
Tartaric acid
Tetrapotassium pyrophosphate
Tetrasodium pyrophosphate
Toluene (Toluol)
Trichlorethylene
Trichloroethane
Trisodium phosphate
Xylene (Xylol)
Zinc chloride
Zinc cyanide
pH
adjustment
required
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Cyanide
or
chromium
treatment
required
X
X
X
Waste products1
DS
MS,DS
MS, DS
DS
MS.DS
MS, DS
DS
DS
MS, DS
MS.DS
DS
MS.DS
MS, DS
MS, DS
DS
MS.DS
DS
MS, DS
MS.DS
MS.DS
0
DS
MS
MS.DS
0
O
MS.DS
MS, DS
0
0
0
MS.DS
0
MS.DS
MS, DS
1MS = metal sludge; NHg = ammonia; DS = dissolved solids; O = organic matter.
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Chapter I
WATER-POLLUTION CONTROL
INTRODUCTION
This part of the paper identifies the in-process water-pollution-abatement techniques including
the equipment available, reduction of chemical waste, planning to prevent pollution catastrophes,
water conservation techniques, and a case study of the upgrading of in-process facilities to reduce
pollution.
PROCESSING EQUIPMENT USED IN THE
METAL-FINISHING INDUSTRY
It is not convenient to the scope of this report to discuss entirely the great diversity of equip-
ment used in metal finishing. It is assumed that the reader needs no further description of the type
of processing that is performed by hand through a great variety of tank-and-vat assemblies. Rather,
it is hoped that the following scan of commonly used automated equipment will enlighten and also
invite increased awareness of the difficulties to be met and resolved during the application of pollution-
control technology and equipment to the metal-finishing facility.
As is seen in figures 1-1 through 1-8, the applicability of any of the automatic finishing machines
is directly dependent upon the quantity of production required in a given length of time, the physi-
cal shape of the workpieces and the means by which they are to be fixtured for processing, and, of
course, the nature of the metal finishing required. From workpieces so tiny that they may scarcely
be observed by the eye to items weighing many tons apiece, all may be processed in variations of
this basic line of equipment.
From the effluent-control standpoint, the type of machine chosen to be the most effective in
fulfilling the desired production requirements will also have a marked effect on the nature of the
effluent and the cost to handle it. For example, if a return-type automatic is to be selected, it is
convenient and inexpensive to incorporate counterflow rinsing, because the rinse tanks are very
small, handle only a rack or two at a time, and do not add a costly and lengthy enlargement to the
prospective machine. Programed hoist equipment requires rinse tanks large enough to handle a
battery of racks or a single rack of long parts. Incorporating more rinse tanks so that counterflow
water-conservation tactics may be employed inevitably implies larger initial capital outlays. On the
other hand, the motion of the hoist in transporting the work may be much more adaptable than
the return-type automatic to delayed dwells in the "up" position, or to repeated dunkings of the
work in the same rinse before moving on to the next process.
With existing equipment, any rearrangements that may lend themselves to chemicals and water-
conservation techniques should also be closely considered for the effect they may have on
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• Cost to make the change
• Cycle reprograming
• Foundation updating
• Busswork and piping
• Ventilation
• Structural supports
SOME METHODS FOR REDUCING OR ELIMINATING CHEMICAL
WASTE IN METAL FINISHING
Process Substitution
Wholesale substitution of low-concentration processes for those of high concentration or proc-
esses containing nontoxic materials for those containing toxic constituents has commenced only in
recent years, inspired undoubtedly by the advent of pollution-control requirements. Unfortunately,
the chemicals contained hi the time-honored processes that made the greatest contribution to a
profitable and efficient metal-finishing job were invariably the same chemicals causing the greatest
adverse impacts to the environment as wastes in the plant effluents.
Substitution, therefore, became practical only when it did not compromise the quality of the
metal finishing and was able to produce an environmental benefit. Perhaps the best known type of
substitution in the past few years has involved cyanide-plating baths, principally those related to
zinc. Elimination or reduction of cyanide was obtained by using noncyanide or low-cyanide-type
processes. The noncyanide baths offered complete freedom from cyanide, but many of these proc-
esses employed chelating and sequestering addition agents to keep the zinc in a soluble form (one
of the jobs formerly performed so well by the cyanide). Treatment of the resulting effluent hence
became virtually impossible as no means was at hand to remove the equally undesirable zinc from
the wastewater stream. Since cyanide was also a good cleaner, the first few minutes of dwell time
in the cyanide-plating bath were cheerfully accepted as cleaning time to complete the job only per-
functorily performed by the previous cleaning and pickling cycle. Without any cyanide, substantial
improvements were required in the preplating treatment steps to achieve good metal-finishing quality.
Many different types of noncyanide processes are now available. Applicability of these processes
must be weighed with due consideration of effluent improvement and process-operational changes.
The low-cyanide processing solutions obviously do not offer complete relief from the onus of
cyanide in the effluent, but they can account for a substantial reduction in use (90 percent is achiev-
able) and an equally substantial improvement in effluent quality. These baths are not really sub-
stitutes, but dilute versions of the baths they "replace." Tighter process control generally is
required when these baths replace conventional cyanide processes, but the use of chelates may be
avoided and the zinc disposal problem may become solvable.
Other substitutes have found use in the industry. They are
• Nonphosphate cleaners
• Non-chromium-bearing dips (in conversion coatings and anodizing)
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• Noncyanide stripping solutions
• Non-chromium-bearing bactericides for cooling waters
• Noncyanide gold and copper processes
Some guideline questions should always be considered when substitution is contemplated.
• Will I eliminate one effluent problem and create another?
• Do I understand fully the control problems that might accompany the change?
• Have I sufficient man-hours available to handle tighter control requirements?
• Will the substitution affect in any way the final quality of my product?
• May I expect an increase in cost in my operation, or will I experience a saving?
• If I already have a waste-treatment facility, what effect will the substitution have on the
treatment system when it is mixed with my normal waste flows?
• Did I overlook any unforeseen ventilation or Occupational Safety and Health Act-related
problem?
• Have I calculated the cost of changing my equipment to accept the substitute process?
Process Solution Concentration—Minimum Limits
Most processes offer a range of concentrations in which they may be operated successfully.
The industry traditionally has selected the midpoint in these ranges as the operating concentration.
With effluent standards and cost savings in mind, serious consideration should be applied to oper-
ating the process solutions at their minimum concentrations! limits. As an example, a standard
nickel-plating solution has the following composition limits:
Chemical
Nickel sulfate (NiS04 6H2O)
Nickel chloride (NiCI2.6H2O)
Boric acid (HoBO-j)
O O
Range
40-50 oz/gal
8-12oz/gal
6.0-6.5 oz/gal
Operating
concentration
45 oz/gal
10 oz/gal
6.3 oz/gal
At the above operating concentrations, a typical small plating shop running an average of 12
hours per day and 250 days per year would experience an annual loss of nickel salts (due to dragout)
of approximately 6,500 pounds nickel sulfate and 1,900 pounds nickel chloride (based on the proc-
essing of 600 square feet per hour and a conservative dragout rate of 1.5 gallons per 1,000 square
feet). Had minimum concentrations been used for the year, the resultant saving in nickel salts would
have been 950 pounds nickel sulfate and 375 pounds nickel chloride, or a saving of about $800. If
this shop applied the same thinking to the other process solutions in the plating line, a major improve-
ment in operating costs would be readily obtainable. Not considered in the improvement is the poten-
tial cost savings in effluent treatment. All metal-finishing operations merit this type of assessment.
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If minimum concentration limits become the practice, tighter process control should be expected and
accommodated. Likewise, any possibility of a reduction in product quality due to mediocre proc-
ess performance should be evaluated.
Control of Dragout
"Dragout" is defined by Kushner1 as "the volume of solution carried over the edge of a process
tank by an emerging piece of work." There are several factors that influence the rate of dragout.
They are
• Velocity of withdrawal of the workpieces
• The geometry of the workpieces
• The positioning of the pieces on the rack or fixture
• The drainage time allowed over the process tank
• The viscosity and density of the process solution
• The temperature of the solution
Many devices may be used successfully for dragout reduction. The velocity of withdrawal of
work from the process tank is least controllable when the metal-finishing cycle is operated by hand,
owing to human fatigue. An excellent method of circumventing this obstacle is to place a bar or
rail above the process tank where the rack may be suspended for drainage while its predecessor is
removed from the rail and transported to the next phase of the finishing cycle. If, however, the
equipment is automated, withdrawal may frequently be slowed, without a subsequent loss of pro-
duction, by reorganizing machine motion. (Vendors of metal-finishing machines can assist on these
motion studies.) No standard rule is available to predict accurately the amount of dragout volume
to be saved by a given reduction in withdrawal speed; noteworthy only is that a saving may be ex-
pected, the degree to be determined by the specific application.
When the purchase of new equipment is being considered, withdrawal and drainage times should
merit close attention before a final design is chosen. This consideration is especially important when
related to bulk processing or barrel plating. Slow barrel rotation during withdrawal has reduced
dragout volumes by as much as 50 percent. Machines may be automated readily to accommodate
this type of rotation at the time of design.
In general, as the chemical content of a solution is increased, its viscosity increases, resulting
in a thickening of the film clinging to work withdrawn from the process solution. This increase
contributes not only to a larger volume of dragout, but to more chemical waste in that volume and
increased difficulty with subsequent rinsing.
Temperature also has an effect on dragout. Elevating the operating temperature of a process
solution will result in diminished dragout by reducing viscosity. Care must be exercised, when in-
creasing temperatures, that bath performance remains unimpaired and that the workpieces acquire
no adverse surface conditions such as dry-on patterns.
A dilemma historically plaguing the metal finisher, especially in electroplating, has always been
the positioning of workpieces on a rack. The primary consideration in racking is proper exposure
of the work to the anodes so that the coverage and thickness uniformity of the electrodeposit may
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be optimum. Drainage and rinsability figure in the racking deliberations because of possible damage
to the workpiece surface by insufficient or inefficient rinsing, or to succeeding process solutions by
drag-in of unremoved chemicals from the previous solution. A contemporary consideration of chem-
ical waste is now made more critical by potential effluent treatment costs. There is even the possi-
bility that the reduction of this waste (and its attendant effluent purification costs) may in some
cases make acceptable the incipient difficulties of poorer coverage and plate distribution.
Maintenance of racks, fixtures, and rack coatings, as an industry average, has been generally
poor. Transport of chemicals from one process to others underneath loose-rack coatings is not
uncommon. Chromium-bearing solutions, for example, appearing in plant effluents in spite of treat-
ment systems designed to handle the normal chromium discharge sources, have been traced to rinse
tanks and process solutions remotely located from the chromium discharge points, having arrived
in these areas by the loose-rack coating route. Increased attention to rack maintenance not only will
eliminate this potential hazard; it is certain to contribute to a welcome reduction in the numbers of
workpieces rejected because of poor contact.
Kushner1 has summarized dragout loss reduction principles with 10 rules.
1. Keep the concentrations of all dissolved materials at the minimum value requisite to the
proper operation of the bath.
2. Do not add anything to a plating bath that does not perform a necessary function in the
same.
3. Operate the plating bath as hot as possible.
4. If there is a choice of conducting salts that can be used in a plating bath, use the salts that
give the greatest density and the smallest viscosity per unit concentration.
5. Make use of an effective wetting agent in the plating bath.
6. With a given, fixed time period allowed for withdrawal and drainage, use the largest part
of the period for withdrawal.
7. For minimum dragout, rack solid objects so that they are extended in area rather than in
depth.
8. Do not rack objects directly above each other so as to lengthen the drainage path.
9. Tilt all solid objects with plane or singly curved surfaces so that drainage flow is consolidated.
10. Every solid object, outside of a sphere, has at least one position in which dragout will be at
a minimum.
Significant chemical losses are also encountered in connection with the batch purifications of
process solutions in external storage tanks and the repacking of process filter equipment. Process
liquids entrapped in sludges and in discarded filter packs are recoverable by the simple expedient of
flushing with water and returning the water, properly filtered, back to the process to replace evapora-
tion losses. Such a practice becomes doubly valuable when the eventual disposal of the sludges re-
maining after purification is considered, as the presence of soluble metals or other toxic materials
in these residues, by today's standards, is forbidden generally by regulations for the disposal of solid
wastes to landfill sites.
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PLANNING TO PREVENT POLLUTION CATASTROPHES
There is, of course, a great difference between the type of pollution that causes a nuisance to
the public domain by gradually altering the environment to which it has been discharged, and a
catastrophic pollution that causes not only a sudden and far-reaching change in the environment,
but also poses a direct and immediate threat to the health of aquatic life and humans.
In the metal-finishing plant, nuisance pollution is characterized by the daily flow of waste
rinse waters to the sewer, usually coupled with small-volume spillages incurred in workpiece trans-
port between processes or during the addition of maintenance chemicals to the processes themselves.
Spent process solutions gradually discharged along with waste rinse waters may also be considered
nuisance pollution.
On the other hand, process solutions, containing concentrated toxic materials, discharged
suddenly and in large volume to the sewer, constitute potential catastrophic pollution. When these
discharges are deliberate, they result from human carelessness and error, and may be eliminated
only by stringent in-plant housekeeping measures. Electromechanical devices strategically located
within the plumbing system may sense the passage of such discharges, but serve only to inform of
the damaging event after its occurrence.
Accidental discharges of a catastrophic nature are far more insidious because they are not pre-
dictable. Fortunately, they are very rare in this industry.
Although revision of a plant to prevent both nuisance and catastrophic pollution is more prop-
erly the province of the pollution-control systems-design engineer, as it is an integral portion of his
entire prospective treatment scheme, control measures should be at least evaluated by the plant
operator before design discussion. Such evaluations may forestall delays and interruptions of the
operator's work schedule that otherwise may be caused by the installation of the treatment systems.
Several general plans may apply as temporary catastrophic-pollution-prevention techniques,
as follows:
1. All rinse waters are piped directly to the sewer (with plans to pipe these rinse waters to
their respective treatment plant areas once the waste-treatment system is designed and in-
stalled). Thus, all floor exits to the sewer may be plugged, preventing the escape of acci-
dental spills of concentrated solutions. Spent process solutions in this system are pumped
to holding tanks for removal by scavenger, or for treatment and gradual discharge. Floor
sumps will be required for sump pumps. Obviously, where both cyanide and chromium
solutions are in use, steps must be taken in floor segregation to assure that cyanide and
alkali-spent solutions are prevented from mixing with chromium and acid wastes, thus avoid-
ing the possibility of generating toxic hydrocyanic acid gases. Separate drainage, sumps,
and holding tanks would be provided for this condition.
2. Another method is to install a large holding pit or lined lagoon located outside. All flows
exiting from the plant would pass through this pit or lagoon before entering the sewer.
Electromechanical devices for the measurement of pH and conductivity would be installed
before the holding area. Any sudden and large variations in pH or conductivity sensed by
the instruments would sound an alarm and turn off all incoming water to the processing
plant. The retention time in the pit or lagoon would be sufficient to cushion and absorb
the incoming concentrated solution, or "slug," without adverse effect at the outfall. Thus,
the slug would be retained in the holding facility for treatment or disposition.
12
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3. A third means of attack is based on the supposition that the plant in question has existing
floor trenches through which all wastes are conveyed from the plant, and that these trenches
are large enough to be divided lengthwise into two subtrenches. By this dividing technique,
the outer side of the trench could be used for rinse waters. The headers from the rinse-water
tanks could go directly to this portion of the trench, which would then be covered over to
prevent entry of floor spillage. The other half of the trench would remain open and would
be used as in plan 2, i.e., it would end in a sump. Accordingly, this open portion of the
trench would have no exit to sewer, and would catch all solution dumps and floor spills for
pumping to a disposition point elsewhere.
To increase awareness of potential pollutive sources within the plant, the following suggestions
for an investigative effort are made:
• Begin by tracking all plant incoming water from its sources to its ultimate destination.
• Do not overlook fume scrubbers, water-cooled rectifiers, heat exchangers, boilers, heating
and cooling coils, air conditioners, and welders.
• Ascertain that all inlet water lines to process solutions have antisiphon devices.
• Inspect all heating and cooling coils for physical condition. (Conductivity meters for leak
detection will be required when a waste-treatment system is installed.)
• Thoroughly inspect all floors and foundations in the processing areas for possible leakage
and consequent percolation to ground waters.
• Check all chemical storage areas for compliance with safety regulations and methods for
handling "empty" and broken containers.
• Make an inspection inside and out of all process tanks and filters for physical condition.
Check especially those tanks where processes are seldom, if ever, removed. All piping should
also be examined.
• Record all data acquired with the foregoing steps. They will prove very useful later.
WATER-CONSERVATION TECHNIQUES
Rinsing represents the most frequently used process in metal finishing. It is by far the largest
consumer of water, and has been given little or no consideration as a cost or problem area. Abun-
dance, ready availability, and low cost historically have contributed to this inattention to plant water
use and to good rinsing practices. Hardening this attitude has been the absence of any strictly en-
forced restrictions on the discharge of waste rinse waters. Rinsing difficulties could always be over-
come with more water—where the water went afterward was a matter of no import. But today the
environment commands attention. Water use and effluent-water quality thus have become major
factors in profit-and-loss statements, and are the principal determinants of the magnitudes of capital
expenditures for water-pollution-control systems.
Modern effluent regulations have eliminated any remaining possibility of continuing to dis-
charge untreated water. Open to question only are the nature and degree of treatment that will be
required. Of great economic consequence, therefore, is any reduction in water use that may be
13
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achieved through plant reorganization of rinsing practices. In plants where there has been little at-
tention to rinse-flow rates, water-conservation studies have repeatedly shown that each rinse-tank
flow usually may be reduced by 50 percent or more without impairment of rinsability. (In one
large plant, a flow of 10,000 gal/hr was reduced to 700 gal/hr before rejected work attributable to
poor rinsing was detected.)
The objective of rinsing is to flush away and remove dissolved salts and solids clinging to work-
pieces so that
• Coatings subsequently applied will bond properly to the work.
• No unwelcome discoloration or chemical change will occur to the work surface due to residual
films.
• Contamination of succeeding process solutions may be prevented.
The objective in water conservation is to get the maximum amount of rinsing with the least
amount of water. Rinsing occurs at the work surface and is influenced by
• Exposure time of the workpieces to the water
• The amount of "fresh" water that may be brought to the work surface during the exposure
time
• The temperature of the entering workpieces and the temperature of the rinse water
• The shape of the work and its position on the rack or in the fixture
Rinse water removes chemical films from workpieces by the process of diffusion. The rate at
which the film is removed is dependent upon the water solubility of the chemicals in that film. The
chemicals are thus absorbed into the body of the rinse water. From a practical standpoint, there
are a number of methods available (although, inexplicably, seldom used) to improve diffusion and
hasten the completion of the rinsing process. Many of these methods also produce a dramatic reduc-
tion in water use.
The most difficult part of the water conservation is the first step, the determination of mini-
mum water use for each rinse phase of the metal-finishing cycle. "Minimum water requirements"
cannot be based on the supposition that the workpieces must be completely free of any chemical
films, for the amount of water to produce such workpiece surfaces is so great as to be economically
untenable and probably unavailable. In actual practice, a chemical film will almost always remain on
the work after rinsing. The amount of film that safely may be allowed to remain on the work is
based on two considerations:
• Chemical films remaining after rinsing must not poison the succeeding process to which the
workpieces will be exposed.
• These postrinsing chemical films must not produce adverse effects on the workpiece surfaces
themselves, or cause underlying problems for subsequent coatings to be applied on the work.
In short, one must reduce rinse-water flow until the residual chemical film, because of its con-
centration and/or thickness, begins to cause subsequent production problems.
Implicit to these considerations is the fact that each process and each plant is different; pro-
duction, work geometry, incoming water quality, processing equipment configuration, even the
14
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protective coatings on incoming basic materials and storage practices, all will influence water re-
quirements. Therefore, each plant operator will be obliged to determine his own minimum water
requirements step by step and rinse by rinse. A logical approach might include the following steps:
Step 1
Investigate plant chemical-consumption records. Peak periods of chemical additions to process
tanks and a rundown on parts that were metal finished during these peak periods will help to locate
the work producing the most dragout.
Step 2
When this work is being run, select a rinse tank following a process whose solution is known to
be difficult to rinse. (Chromium or cyanide baths are good examples.) The rinse tank must have
been cleaned and filled with fresh water and then turned off. The level should be high enough to
allow immersion of the rack or barrel to the usual depth, but should be low enough to prevent water
displaced by the immersion to overflow. Vigorous agitation of the work and/or the rinse water is
suggested. With the volume of water known by simple tank measurement, and with an analysis of
the process bath preceding the rinse already available, an analysis of one process bath constituent in
the rinse water predicts all the other constituents by ratio and establishes a highest dragout-volume
figure. This figure may be assumed to be the dragout volume from each of the rest of the metal-
finishing processes in the cycle where the same racks or barrels are used. Although it is recognized
that 100-percent removal of the chemical film may not always be removed in this single stagnant
rinse, the operator may exercise his own judgment on the efficiency of a second stagnant rinse for
dragout determination. A hose might be used (as a second rinsing) as the work is being withdrawn,
and the used water collected, measured for volume, and analyzed as before.
Step 3
When the volume of dragout has been thus established, its concentrations in the case of every
process bath should be arithmetically adjusted to the highest levels at which any of these baths
might be operated. A similar dragout determination should be considered wherever a different line
is involved and the work processing motions and fixtures are likewise different. (Dragout figures
thus achieved are of paramount importance in the successful design of waste-treatment systems.)
Step 4
With the dragout concentrations and volumes now known, reduction of water use in rinse tanks
may commence. Existing rinse-water flows must be measured. In the absence of flowmeters, two
techniques may be used successfully.
The first method involves physical measurement of the working volume of the rinse tank, a
lowering of the rinse-water level to a measured depth (at the end of the working day after the water
has been turned off) and a measure (at the beginning of the next day when the water is turned on
again) of how long it takes to fill the tank again to operating level. This method is effective when
rinse-tank outlet headers are permanently piped into the exit trench or sewer. A variation of this
method is to insert a 5-gallon bucket into the flowing rinse. By withdrawing 5 gallons of rinse water
rapidly, one may time the period required for 5 more gallons of rinse water in the rinse tank to reach
overflow levels again. This test must be repeated several times and the results averaged, because it
15
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is difficult to ascertain visually the exact time at which the flow over the overflow dam has reached
a stabilized flow condition.
The second method involves a 5-gallon bucket and a stopwatch for measurements at the over-
flow outlet. An alternative method is to buy a flowmeter and use it in each of the incoming rinse-
water lines, one by one, until the necessary information is obtained.
All flow-rate measurements should be recorded carefully, as should readings at the water main.
Now the actual reduction of rinse flows may begin. This is the most difficult phase of the entire
conservation and abatement operation. It is laborious, because each rinse must be carefully ob-
served during the gradual day-to-day reduction in flow rate so that the effect on the work and/or
the succeeding process may be duly noted as the moment arrives when poor rinsing begins to cause
rejections. The strictest discipline must be maintained in the plant by the operating personnel so
that the cause for rejection may be traced to its true source. Valve settings on rinse-water lines
must be under the specific control of the person charged with water conservation, and tampering
should not be tolerated. As the maximum reduction in flow rate for each rinse is revealed and the
readings recorded, rinse-water flows may be advanced slightly to prevent further rejection. At this
juncture, if no further conservation measures are to be considered, flow-restrictor valves should be
installed in all rinse-tank incoming waterlines. Several types are available that not only restrict
water flow to a fixed maximum output, but also will adjust automatically to changes in water main
pressure, even act simultaneously as siphon breakers, and are tamperproof. Flowmeters may be
used in conjunction with normal valving to control flow, having the advantage of advancing flow
rates when desired, but they are not tamperproof and are much more expensive. It should be duly
noted that up to the point of installing valves or meters, no money has been spent except in the
necessary labor. It is also likely that the average plant, upon concluding this first water-conservation
effort, will achieve a reduction of about 50 percent in its water use. An average plant with a total
flow rate of 100 gal/min can thus save approximately 50 gal/min, and, based on 3,000 operating
hours per year and a water charge of 25 cents per 1,000 gallons, an annual saving of over $2,000
is achieved. The same reduction in water use will cut the capital costs of a waste-treatment system
in half—for the average plant, that saving can amount to $40,000.
Further and equally dramatic reductions in water consumption are achievable through the use
of mechanical devices and equipment rearrangements, such as the following.
Counter-flow Multiple-Tank Rinsing (Figs. 1-9 and 1-10). In counterflow rinsing, used water
exiting the first tank becomes feed water for the second, and after being used again, feeds the third
tank, and so on.
The advantage of counterflow rinsing is in the repeated exposure of the workpieces to the water,
the increase in dwell time (permitting more diffusion to occur), and the ability to bring most of the
water passing through into more intimate contact with the work. The results in water saving are
gratifying. For example, if a dragout of 1 gal/hr in a given case required a 1,000-to-l dilution in order
to produce acceptable work, 1,000 gallons of rinse water per hour would be required in a single rinse
tank; in a double counterflow rinse system, 30-35 gal/hr are required, and in a triple counterflow
rinse system, 8-12 gal/hr are needed. The disadvantage is that the work requires two or three proc-
essing steps instead of one, and more equipment and space is also mandatory. If multiple counter-
flow rinsing is designed into prospective automatic metal-finishing equipment, the initial disadvantages
are increased capital expense and space requirements. The ultimate advantage lies not only in the
enormous drop in water costs, but also in a sharp reduction in the cost of the supporting waste-
treatment system. Additionally, the curtailment of water volume makes the use of waste recovery
systems more inviting.
Multiple-Tank Rinsing (Fig. 1-11). This type of rinsing is merely a battery of single rinses, each
with its own feed waters. The principles are generally the same as in counterflow multiple-tank
16
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rinsing, although the total reduction in water consumption will not be as great as with the counter-
flow system.
Spray Rinsing (Fig. 1-12). Two categories of spray rinsing may be used. The first, impact spray-
ing, uses both impact and diffusion to remove contaminant films. It uses little water compared to
immersion rinsing, and may be used in some cases as a recovery rinse by pumping the collected
spray volume into the previous process tank, but is disadvantaged when the workpieces have areas
inaccessible to the spray nozzles.
The second method, rinse and spray, employs immersion rinsing followed by a spray operational
only when the work is withdrawn from the rinse tank. It is advantageous in removing stubborn
films by impact and permits lower water flows in the main body of the rinse tank.
Fog Rinsing (Fig. 1-13). Fog rinsing finds utility at exit stations of process tanks. A fine fog
is sprayed on the work, thus diluting the dragout film and causing a runback into the process solu-
tion. Fog rinsing finds application in those instances where process operating temperatures, high
enough to produce a high evaporation rate, allow replacement water to be added to the process in
this manner. Fog rinsing also prevents dry-on patterns by cooling the workpieces. To be effective,
fog rinsing requires a slow rate of withdrawal of the work from the process tank.
Chemical Rinsing (Figs. 1-14 and 1-15). The principle of chemical rinsing has been used by the
metal-finishing industry for many years. One of the oldest applications of this principle was used
quite effectively to eliminate staining from the chromium solution, notoriously difficult to rinse.
By the simple expedient of making the first rinse after chromium plate a stagnant rinse containing
sodium bisulfite, the drag-in of hexavalent chromium was converted to trivalent chromium. Thus,
the rinsability of the work in the second rinse was improved considerably by:
• Changing the chemical nature of the film on the work in the stagnant rinse, and
• Reducing film concentrations before attempting to rinse by diffusion. The same principle is
frequently employed hi "neutralizing" dips.
The application of chemical rinsing to plant effluent treatment has been well described by
Lancy2' 3> 4 and Pinner5 and is known as "integrated waste treatment" in the industry. Aside from
the environmental benefits thus achieved, this type of chemical rinsing also prevents the majority of
heavy metal solids formed in the chemical rinse from reaching the succeeding water rinses by remov-
ing these materials in an external settling vessel. This is accomplished by flowing the chemical rinse
solution to a treatment reservoir. The overflow from the reservoir is pumped back to the rinse tanks
forming a complete closed-loop system. Chemicals are added to the reservoir to provide a controlled
excess of reagent in the solution. The reservoir acts as a combined reaction and settling tank. Be-
cause of the presence of a controlled excess of reagents in the chemical rinse tank, toxic materials
and heavy metals are removed from the metal-finishing sequence and are prevented from entering
the subsequent water rinse. At the same time rinsing is improved due to the fact that the diffusion
layer, which is present during conventional water rinsing, is broken down by the chemical reaction.
Some Additional Techniques
Such equipment rearrangements and additions as water-conservation measures are capable of
reductions in water use of up to 90 percent! Additionally, the savings related to prospective capital
outlays cannot be calculated solely in terms of reduction in equipment size; it can make the differ-
ence between satisfying effluent-control demands or closing the metal-finishing plant, if considered
only from the standpoint of available plant space. The basis for future effluent-control systems
design, likewise, may be radically changed by the skillful application of conservation techniques.
17
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Other devices that assist in the improvement of rinsing are
• Agitation of the work in the rinse tank
• Air agitation of the rinse water
• Hydraulic agitation of the rinse water
• Agitation through mixers or impellers
• Ultrasonic agitation
• Elevation of rinse-water temperature
• Use of rinse aids and wetting agents
• Recirculation and reuse of rinse water using ion exchange
No consideration has been given here to the possibilities of reusing treated water from a prospec-
tive effluent-treatment facility to achieve yet a further reduction in water purchases. An accurate
assessment of the volume and quality of reuse water from this source cannot be made until the de-
sign concept for a treatment system has been decided. The treatment methods chosen will determine
the quality of the treated water and the selection of rinse tanks where it may be safely used. None-
theless, the prospect of recovered water must be considered as a factor during water-conservation
planning endeavors.
When the foregoing water-conservation practices have been concluded, the compiled data will
supply the necessary ingredients to predict rinse-water volumes required when the new workpieces
and racking produce a change in dragout conditions. Only the new dragout volume and concentra-
tion need be determined by actual analysis (as defined earlier in this presentation). Formulas6' 7 • 8
may then be applied to calculate the flow rate required, and the proper restrictor valve settings may
then be applied.
UPDATING METAL FINISHING AND POLLUTION
CONTROL AT COMPANY X
At a meeting of the board of directors of Company X on October 18,1971, the major topic of
discussion was pollution control and what to do about it. Everyone agreed that something should be
done, but since very little pressure had been received by Company X from the people down at the
sewage works to clean up the company's discharges (and besides, there were no clear rules or recom-
mendations to date that pointed the way to doing a once-and-for-all job on pollution control), there
was an understandable reluctance to spend money when the goal was not clear and it did not make
a profit.
The conclusion of the board on that day was that it would be necessary to appoint a responsi-
ble member of middle management to the task of finding out what the scope of the problem was,
and, then, how it could reduce the amount of pollution and get ready, once the oncoming regulations
applying to them became known, to put in pollution-control systems. If, at the same time, a way
could be found to reduce the waste of the company's chemicals and water, so much the better.
18
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To accomplish these objectives quickly and expeditiously, the board selected an aggressive
young manager. His primary responsibility was to define the plant's environmental problem—
if time remained to perform his other duties, fine^f not, those duties would be assigned to some-
one else. In addition, he was told that all future environmental considerations affecting the opera-
tions of Company X would be his responsibility. In effect, he became the new pollution control
officer reporting directly to the president and chairman of the board. He was given the authority
to require the cooperation of all plant personnel to accomplish his mission.
The first step was to develop a site plan (see fig. 1-16) to show
• Where the waterborne wastes came from and where they were going
• Where the plant boundaries were
• What usable space was available for future pollution-control equipment
• What influence the topography might have on drainage
Several more points were revealed during the site investigation.
• There was no manhole at the point where the plant industrial sewer joined the interceptor,
and thus, no easy way to sample the effluent for analysis or to determine the flow rate. A
design for a manhole was obtained from the city sanitary department; it included a calibrated
V-notch weir and provisions for monitoring equipment.
• It was possible during a rain to have drainage from a chemical storage area for "empty" con-
tainers run into a ditch leading to a small creek.
• The water table at the outside area assigned to future pollution control equipment was more
than 30 feet down.
Next came a sketch and study of the equipment layout (see fig. 1-17), which included
• The location of each waste-producing piece of equipment
• The processing cycles
• The production from each cycle
• The location of accessory equipment
The geography of the equipment would prove useful when the time came to move pollution-
control equipment into the plant. Updating of this layout print whenever any equipment changes
occurred would prevent the appearance of an obstacle (where no obstacle was supposed to be) to
confound the installation engineer. (The importance of this document to a pollution-control sys-
tems design engineer is incalculable; it has a major influence on the selection of both treatment con-
cept and equipment.) Recorded also at this time was information concerning
• Plant electrical power and capacity
• Steam availability
19
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• Head space and usability
• Support column locations
Since four major metal-finishing lines were to be examined, it was decided to look at them one
at a time. Hence, an individual equipment layout was drawn in each case. The nickel-chromium
plater (see fig. 1-18)—including its rack strip line—began the parade. The object was to determine
and record what was in each process tank in terms of major chemical constituents, when spent proc-
esses were dumped, how much rinse water was being used, and what volume of dragout was being
developed. To accomplish the first, a record of purchases of all chemicals and basic materials for
1971 was obtained from the chief buyer, and matched with the metal-finishing department's record
of additions to the various tanks. Where proprietary materials were involved, the suppliers of those
materials were contacted for information on the principal ingredients.
Next came the determination of dragout and process dumping schedules (see fig. 1-19). In this
line, the chromium-plating solution was chosen for the measurement and used as the criterion for
the other process dragout volumes in the line. No substitutions were contemplated, but plans were
made to investigate the applicability of phosphate-free cleaners. All processes were reduced to their
minimum concentrations, and a fog rinse was installed at the exit station of the nickel bath.
Attention now turned to the rinse flows (see fig. 1-20). Gradual reduction of these flows over
a period of 5 weeks produced an average cutback for the entire line of 910 gal/hr, or approximately
55 percent.
In the zinc plater (see figs. 1-21 through 1-23) the same procedure was used. The cyanide zinc
solution was replaced with a noncyanide, nonchelated alkaline zinc process, and the chromates were
made to last 50 percent longer by altering the baths with inhibitors and increasing updwell time over
them. Double dunking is now being considered in selected rinses.
Rinse-flow reduction amounted to an aggregate of 1,400 gal/hr, or about 45 percent.
The phosphater (see figs. 1-24 through 1-26) did not have any substitution of process. Rinse-
water flow was reduced by 750 gal/hr, or about 40 percent. It was discovered that the cleaners
would last for 10 days if small frequent additions of replenishment cleaner were made. This practice
resulted in a 50-percent saving by decreasing the frequency of the discard of spent process.
Only a small saving was realized in the anodizer (see figs. 1-27 through 1-29). The desmutter
was replaced by a chromium-free process, and a reduction in water use of 80 gal/hr, or about 35
percent, was realized.
After the rinse-water conservation program was completed, several remedial measures were
taken to prevent the new housekeeping attitude from having a relapse.
• All incoming rinse-water lines were equipped with restrictor valves.
• All hoses were spring loaded so that they could not be abandoned in a running condition.
• All the rinse-water mains leading to each automated line were equipped with solenoid valves
connected to the control panels of each machine. When the machines were not operating
during breaks or lunch periods, the valves automatically shut off rinse-water flow.
• An investigation is now being carried out to determine the advisability of conductivity cells
for the rinse tanks.
20
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• Areas between adjacent tanks (where spillage and drippage from work in transfer could fall
to the floor) were equipped with troughs to catch such drippage and let it drain back to the
process from which it had originated.
• All naked anode rails were taped to prevent erosion of contaminating metals into the proc-
esses they served.
• Tank covers furnished with original equipment, and long since removed from the tanks, were
returned to their intended purpose.
• Chemical definitions of all protective oils or drawing and stamping compounds used either
in the plant or by vendors were obtained, tested for ease of removal, and catalogued. Ven-
dors and plant personnel alike were expressly forbidden to change the composition of any of
these coatings without notifying the plant chemist and the pollution-control group. Sim-
ilarly, changes in metal-finishing process compositions could not be made without approval
by the pollution-control group.
Company X, in the first year of operation since these changes were made, has saved:
Amount
By lowering water use $ 4,300
By reducing chemical use 5,800
By a 1.7-percent drop in overall rejection rate 7,700
Total $17,800
What is more important, Company X had only a few more chores to perform and it would be
ready for pollution-control design. A foundation plan (see fig. 1-30) was needed so that a design en-
gineer could make recommendations on the segregation of accidental spills and on the most con-
venient disposition of spent processes. The problem of catastrophe prevention would require a long
look at the types of coatings available for floor and foundation protection. Although Company X
had never experienced a catastrophic spill in its 17 years of operation, it was painfully evident to the
board of directors that the existing foundation plan did not offer safety, should the 17-year record
be ended inadvertently. (And, too, the city had just received funds to erect a secondary treatment
system, complete with bugs that eat sewage but do not much like metal-finishing wastes.) The foun-
dation plan, however, did lend itself to the temporary piping of all rinse waters to the underground
pipes leading to the interceptor. Thus, the trenches could house the rinse-water pipes and also be
used to convey floor spills and dumps to blind sumps from which they would be pumped into hold-
ing tanks for disposition. This plan is now being implemented by Company X.
All that now remained was to tabulate each toxic material (see table 1-1) by reviewing materials
purchased and process composition. The tabulation accurately predicts the quality of the effluent.
With the new manhole now installed, Company X is recording flow rates exiting from the plant.
Composite samples are being taken by means of a 24-hour sampler recently purchased. Quantitative
results will soon be available. Because Company X took the time to survey its plant and its chemi-
cal use, the need for extensive and expensive effluent sampling has been greatly reduced. Effluent
sampling will confirm by analysis the accuracy of the earlier dragout determinations. The record
on the contents of each process and Company X's purchases will tell the analyst what he must search
for in the samples.
21
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Table 1-1 .—Items to be expected in plant effluent
of Company X
Metals
Nickel
Chromium
Copper
Iron
Antimony
Aluminum
Lead
Zinc
Organ ics
Soluble oils
Immiscible oils
Gluconates
Dyes
Proprietary additives
Dissolved solids
Calcium
Sodium
Potassium
Borates
Carbonates
Nitrates
Chlorides
Sulfates
Fluorides
Silicates
Phosphates
The company has now turned its attentions to developments in environmental regulations.
Plans for company growth will be influenced, but Company X now has bought the time to weigh
these plans carefully, the time to examine the field for firms whose capabilities in environmental
control design will conclude successfully the work it has started. Company X is also satisfied that
when the control system it chooses is installed, it will be able to accommodate the work without
any serious interruption in normal production.
Company X reckons that it has spent almost $6,000 in man-hours, analysis, and some equip-
ment. It has discovered many serious lapses in production techniques during the investigation. It
has eliminated any reasonable possibility of catastrophic pollution. Most of all, Company X is
ready for the future.
REFERENCES
1J. B. Kushner, Metal Finishing, pp. 59, 60, 61, 64, Nov. and Dec. 1951.
2L. E. Lancy, Metal Finishing, pp. 49(2), 56,1951.
3L. E. Lancy and H. F. Hanson, Plat ing, pp. 39, 210,1952.
4 L. E. Lancy, Sewage and Industrial Wastes, pp. 26,1117,1954.
5 R. Pinner, Electroplating and Metal Finishing, p. 20, July, Aug., Sept., 1967.
6 A. F. Mohrnheim,Pfafmg, pp. 715-718, June 1969.
7J. B. Kushner, Metal Finishing, pp. 715-718, Jan. 1955.
* J. A. Tallmadge and B. A. Buffham, Journal of Water Pollution Control Federation, pp. 817-
828, Aug. 1961.
22
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Figure 1-1. Return-type automatic system: medium duty rack application.
Figure I-2. Conveyorized automatic loading and unloading.
23
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Figure 1-3. Sidearm return-type automatic systems: heavy duty applications.
Figure 1-4. Programed automatic hoist system: heavy duty applications.
24
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Figure 1-5. Typical heavy duty application.
Figure 1-6. Programed hoist system: bulk-finishing applications.
-------
Figure 1-7. Programed automatic hoist system: bulk-finishing applications.
Figure 1-8. Oblique-barrel automatic system: bulk-finishing applications.
26
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SINGLE RINSE
OUTGOING WATER -
iiiii
WORK MOVEMENT
INCOMING WATER
DOUBLE COUNTERFLOW
RINSE
OUTGOING WATER -
* WORK MOVEMENT
INCOMING WATER
Figure 1-9. Counterflow multiple-tank rinsing: (a) single rinse; (b) double counterflow rinse.
27
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TRIPLE COUNTERFLOW
RINSE
WORK MOVEMENT
p- INCOMING WATER
OUTGOING WATER
OUTBOARD TRIPLE COUNTERFLOW RINSE
WORK MOVEMENT
INCOMING
WATER
OUTGOING WATER
Figure 1-10. Counterflow multiple-tank rinsing: (a) triple counterflow rinse; (b) outboard triple counter-
flow rinse.
28
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WORK MOVEMENT
t-' —INCOMING
WATER
OUTGOING WATER
Figure 1-11. Multiple-tank rinsing.
SPRAY RINSING
•
.
r
INCOMING
WATER
IMPACT SPRAY 1 RINSE AND SPRAY
OUTGOING WATER
Figure 1-12. Spray rinsing.
WORK MOVEMENT
PROCESS TANK
Figure 1-13. Fog rinsing.
29
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WORK MOVEMENT
RINSE WATER
OUTGOING WATER
PERIODIC BATCH DUMP
Figure 1-14. Chemical rinsing.
. WORK MOVEMENT
TREATMENT CHEMICAL ADD-i
SLUDGE REMOVAL
Figure 1-15. Integrated chemical rinse.
30
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FUTURE
PUNT
EXPANSION
SHIPPING
DOCK
SHIPPING
ft RECEIVING
EMPLOYEE
PARKING
VISITOR PARKING
L
GRADE
ELEV. W3.tr
OUTSIDE AREA
AVAILABLE FOR
WASTE TREATMENT
EQUIPMENT
ROOM AVAILABLE
FOR WASTE
TREATMENT EQUIP.
\
J
MANUFACTURING
OFFICES
(PLANT FLOOR ELEV. 605.37')
PLATING ROOM
= _£ MACHINES (REF.) r
[BUFFING ! STORAGE
i ROOM I
SEWER
LOT BOUNDARY LINE
GRADE
ELEV. 803.25
I
a
a
jm
BRADLEY
Figure 1-16. Company X site plan.
-------
09
i j
RECTIFIER ["]
ZINC
RACK STRIP
NICKEL-CHROMIUM PLATER (AUTOMATIC)
46 RACKS/HR.-16 HR./DAV
6 SO. FT./RACK. MAX.
WORKPIECES- STEEL STAMPINGS
RECTIFIER
I
TEM
RECTIFIER
NITER
A-A BLOWER
RECTIFIER
BARREL ZINC PLATER (AUTOMATIC)
12 BARRELS/HR.-16 HR /DAY
300 LB./BBL MAX.
WORKPIECES-STEEL FASTENERS
BARREL SIZt 1S"«36"
ZINC COOLING SYSTEM
BARREL PHOSPHATER (AUTOMATIC)
10 BARRELS/HR. 16 HR./DAY
500 LB./BBL. MAX.
WORKPIECES-STEEL THREADED FASTENERS
BARREL SIZE 18" x 30"
RECTIFIER
0
©:©"0"6"©!©!o!fof© &'©"&
Q; ©
ANODIZER (MANUAL HOIST)
2 LOADS/HR. 8 HR./DAY
60 SQ. FT./LOAD MAX.
WORKPIECES- ALUMINUM STAMPINGS
FILTER
DEIONIZER
A-A BLOWER RECTIFIER
Figure 1-17. Company X equipment layout.
-------
8 OZ/GAL
SODA ASH
CONC.
NITRIC ACID
(PROPRIETARY
ADDITIVES)
w
DO
[©1
I
12 OZ/GAL
CAUSTIC SODA
SODA ASH
PHOSPHATES
SILICATES
SURFACTANTS
30% BY VOL.
HYDROCHLORIC
ACID
A
SAME AS (6)
SAME AS (3)
12 OZ/GAL
CAUSTIC SODA
SODA ASH
PHOSPHATES
SILICATES
SURFACTANTS
--q)
50 OZ/GAL NICKEL SULFATE
12 OZ/GAL NICKEL CHLORIDE
7 OZ/GAL BORIC ACID
PROPRIETARY ADDITION AGENTS
50 OZ/GAL CHROMIC ACID
CATALYST (SULFURIC ACID
AND FLUORIDES)
(PROPRIETARY)
12 OZ/GAL
CAUSTIC SODA
SODA ASH
SURFACTANTS
PHOSPHATES
GLUCONATES
Figure 1-18. Nickel-chromium plater process composition.
-------
, t
[0|© '!<•
\
300 GAL
TWICE
YEARLY
H
>1- 00
i
r
I
300 GAL. 300 GAL.
YEARLY QUARTERLY
190 GAL.
300 GAL. 300 GAL. (EST.) 'T... ~TnRflr7 MONTHLY
QUARTERLY MONTHLY rdl « 190 GAL
100 GAL IEST I B— TWICE
1UU UflL. (CM.) ) /-p,|TrR S~\\ UUCCI/IV WE
MONTHLY -|jj L FILTER \J\ WEEKLY
(pi jt y\ <
H^ijy iS'^(;)lii) Q i
III £ '& © , $ . (
di
540 GAL.
MONTHLY
GAL. i
EKLY
5 © £22 3 Cb fij y
;
idi] I;
NOT DISCARDED NOT DISCARDED iqn 'Rfl| 1100 GAL.
PROCESS
1. SOAK CLEAN
2. C.W. RINSE
3. ANODIC CLEAN
4. C.W. RINSE
PROCESS
TANK
CAPACITY
1100 GAL.
540 GAL.
PROCESS
TANK
PROCESS CAPACITY
12. C.W. RINSE
13. NICKEL PLATE 3300 GAL.
DAILY MONTHLY
RACK STRIP
RINSE
TANK
14. ORAGOUT P«0«SS CAPACITY
15. C.W. RINSE 1 CHROME STRIP 300 GAL
5. C.W. RINSE & SPRAY
6. ACID 190 GAL
1. C.W. RINSE
8. C.W. RINSE & SPRAY
9. ANODIC CLEAN
190 GAL
10. C.W. RINSE & SPRAY
1R T W RINSF 2 DRAIN
IB. C.W. HINbt
17. CHROME PLATE 560 GAL. J N,CKEL STRIP 300 GAL
18 DRAGOUT B
C.W. RINSE
19. C.W. RINSE B. NEUTRALIZE 300 GAL.
20. C.W. RINSE & SPRAY 7. C.W. RINSE
21. H.W. RINSE 190 GAL. 8. H.W. RINSE 300 GAL.
11. ACID
190 GAL.
22. LOAD & UNLOAD
Figure 1-19. Nickel-chromium plater and rack strip dumping schedule: spent processes.
-------
CO
O!
RACK STRIP
' . -I i : i • • i ' •
2 GPH
10 GPH 10 GPH
RINSE FLOWS
10 GPH 1 i
* * t
1
240 G
!
, , , , v .
, , , , ,0, , @:§
i
240
RINSE FLOWS
RINSE
TANK
PROCESS CAPAI i i PROCESS
90 GPH
90 kpH 360 GPH
L , ! i -o •
— f* i i »i
®G> ^lOiOM^I ' d) ' S3I *Q*
'$- « ty , IC^Ml^M + EL, I ,Q,y
1
!±
LJ 4-1
GPH 20 PGH
120 GPH
RACK STRIP
RINSE RINSE
TANK TANK
CAPACITY PROCESS CAPACIT>
1. SOAK CLEAN 12. C.W. RINSE 190 GAL. , CHROME STRIP
2. C.W. RINSE 190 GAL. 13. NICKEL PLATE 2. DRAIN
3. ANODIC CLEAN 14. DRAGOUT 3 c w RjNSE
4. C.W. RINSE COUNTERFLOW 190 GAL. 15. C.W RINSE 190 GAL. 4 N|CKEL STRIP
5, C.W. RINSE 190 GAL. 16 C.W. RINSE 190 GAL. 5 CW RINSE
& SPRAY 17. CHROME PLATE e NEUTRALIZE
6 ACID 18. DRAGOUT 7 c w RINSE
7. C W RINSE 190 GAL. 19. C W. RINSE COUNTERFLOW 190 GAL 8 H W RINSE
8. C.W. RINSE COUNTERFLOW 190 GAL. 20. C.W. RINSE 190 GAL.
& SPRAY & SPRAY
9 ANODIC CLEAN 21. H.W. RINSE 190 GAL
10. C.W RINSE & SPRAY 190 GAL. 22. LOAD & UNLOAD
300 GAL
300 GAL
300 GAL.
300 GAL.
11. ACID
Figure I-20. Nickel-chromium plater and rack-strip rinse-water data.
-------
p
(ft
6 OZ/GAL ZINC METAL
10 OZ/GAL CAUSTIC SODA
12 OZ/GAL CYANIDE
CARBONATES
PROPRIETARY ADDITIVES
© O © 0
30 BY VOL.
HYDROCHLORIC ACID
12 OZ/GAL
CAUSTIC SODA
SODA ASH
SURFACTANTS
PHOSPHATES
GLUCONATES
©©© © o-
10 OZ/GAL SODIUM DICHROMATE
3 FL. OZ/GAL NITRIC ACID
1 OZ/GAL SODIUM DICHROMATE
2 FL. OZ/GAL NITRIC ACID
12 OZ/GAL
CAUSTIC SODA
SODA ASH
PHOSPHATES
SILICATES
SURFACTANTS
Figure 1-21. Zinc plater process composition.
220 GAL.
TWICE
WEEKLY
©
NOT DISCARDED
SO©
!
265 GAL.
WEEKLY
© Q © © © © 0 © O
t
220 GAL
DAILY
t
220 GAL
TWICE
1
220 GAL
WEEKLY DAILY
300 GAL
WEEKLY
PROCESS
1
1
LOAD & UNLOAD
SOAK CLEAN
C.W. RINSE
ACID PICKLE
C W RINSE
C.W RINSE
PR ELECTRO CLEAN
C W RINSE
PROCESS
TANK
CAPACITY
300 GAL
220 GAL
265 GAL
PROCESS
9. ZINC PLATE
10 C W RINSE
11 C.W RINSE
12. CHROMATE 1
13 CHROMATE II
14 C W RINSE
15 W W RINSE
PROCESS
TANK
CAPACITY
1800 GAL
220 GAL
220 GAL
220 GAL
Figure I-22. Barrel zinc plater dumping schedule: spent process.
36
-------
© ©
^' ••-
1
300 GPH
© O © © 0 © © ©0©
*
\ r
300 GPH
I
850 GPH 850 GPH 850 GP
111 1
© o
1
20 GPH
H
PROCESS
1 LOAD & UNLOAD
2 SOAK CLEAN
3 C W RINSE
4 ACID PICKLE
5 C W RINSE!
6 C W RINSE
7 PR ELECTRO CLEAN
8 C W RINSE
RINSE
TANK
CAPACITY
(D
220 GAL
UNTERFLOW 220 GAL
220 GAL.
PROCESS
9
ZINC PLATE
C.W. RINSE COLIIMTERFLOW
C W. RINSE
CHROMATE 1
CHROMATE II
C.W RINSE
RINSE
TANK
CAPACITY
220 GAL
220 GAL
220 GAL
15 W W RINSE
220 GAL
220 GAL
Figure 1-23. Barrel zinc plater rinse-water data.
5 OZ/GAL
ZINC PHOSPHATE
PHOSPHORIC ACID
NITRATES
iPROPRIETARYi
13 BY VOL.
HYDROCHLORIC ACID
AND ANTIMONY
(PROPRIETARY)
-.•' T *
I
SAME AS >2
10 BY VOL.
SULFURIC ACID
EMULSIFIED
MINERAL OIL
12 OZ/GAL
CAUSTIC SODA
SODA ASH
SURFACTANTS
PHOSPHATES
GLUCONATES
Figure 1-24. Phosphater process composition.
37
-------
£a =H=a E - .:fi) - /£
if
ill I'L^k H
; ! i i
,
© C
225 GAL.
NOT WEEKLY
DISCARDED 1
270 GAL.
DAILY
270
^\ (e^^sfeS^d
' ' '• 1
|>;l © i®iii®|y
310 GAL.
WEEKLY
27C
D
GAL.
WEEKLY
PROCESS
TANK
'ROCESS CAPACITY
1. LOAD SHUTTLE
2. SOAK CLEAN 310 GAL.
3 SOAK CLEAN 310 GAL.
4. C.W. RINSE
5. HOT SULFURIC PICKLE 270 GAL
6. C.W. RINSE
7 PRE DIP 225 GAL.
PROCESS
8.
9.
10.
11.
12.
13.
14.
W.W. RINSE
PHOSPHATE
C.W. RINSE
C.W. RINSE
H.W. RINSE
SEAL & OIL
UNLOAD STAND
^^
i " ! n
I ; 1 '
— ,. •
i
GAL.
AILY
NOT
DISCARDED
PROCESS
TANK
CAPACITY
270 GAL.
1080 GAL.
270 GAL.
270 GAL.
Figure I-25. Phosphate dumping schedule: spent process.
©^
t
240 GPH 120 GPH 720 GPH 720 GPH
i 1 I 1
(£^
120 GPH
- ia*u urn -
PROCESS
1. LOAD SHUTTLE
2 SOAK CLEAN
3 SOAK CLEAN
4. C.W RINSE
5. HOT SULFURIC PICKLE
6. C W RINSE
7. PRE DIP
RINSE
TANK
CAPACITY
225 GAL
225 GAL.
PROCESS
8.
9.
10.
11.
12.
13.
14
W.W. RINSE
PHOSPHATE
C W. RINSElCOUNTERFLOW
c.w. RINSE]
H.W. RINSE
SEAL & OIL
UNLOAD STAND
RINSE
TANK
CAPACITY
270 GAL.
225 GAL.
225 GAL.
225 GAL
270 GAL.
0
Figure 1-26. Barrel phosphater rinse-water data.
38
-------
VARIABLE
DILUTE
CONCENTRATION
NICKEL ACETATE
15% BY WEIGHT
SULFURIC ACID
SURFACTANT
16 OZ/GAL
CAUSTIC SODA
AND
PROPRIETARY
ADDITIVES
5% BY VOL.
CHROMIC ACID
NITRIC ACID
12 OZ/GAL
CAUSTIC SODA
SODA ASH
SURFACTANTS
PHOSPHATES
GLUCONATES
Figure 1-27. Anodizer process composition.
320 GAL.
VARIABLE
(AV6.
QUARTERLY)
320 GAL.
TWICE
MONTHLY
320 GAL.
WEEKLY
475 GAL.
QUARTERLY
320 GAL.
WEEKLY
PROCESS
1. SOAK CLEAN
2. RINSE
3. CAUSTIC ETCH
PROCESS
TANK
CAPACITY
320 GAL.
320 GAL.
4. RINSE
5. RINSE
6. DESMUT
7. RINSE
320 GAL.
PROCESS
8.
S
II
11
12
ia
ANODIZE
RINSE
D.I. RINSE
DYE
RINSE
HOT WATER SEAL
PROCESS
TANK
CAPACITY
475 GAL.
320 GAL.
320 GAL.
14. WARM D.I. RINSE
Figure 1-28. Anodizer dumping schedule: spent processes.
39
-------
— 245 GPH
PROCESS
15 GPH
RINSE FLOWS
RINSE
TANK
CAPACITY
PROCESS
SOAK CLEAN
RINSE 320 GAL.
CAUSTIC ETCH
RINSE COUNTERFLOW 320 GAL.
RINSE 320 GAL.
DESMUT
RINSE 320 GAL.
g. ANODIZE
9. RINSE
10. D.I. RINSE
It. DYE
12. RINSE
13. HOT WATER SEAL
14. WARM D.I. RINSE
TANK
CAPACITY
320 GAL.
320 GAL.
320 GAL.
320 GAL.
Figure 1-29. Anodizer rinse-water data.
OUTSIDE
BUILDING
WALL
JNDERGROUNO PIPE
TO SEWER
IMIIUi'lll
NICKEL-CHROMIUM PLATER
OPEN TRENCH
HIHI i ii i ii in
ANODIZER
Figure 1-30. Foundation layout.
40
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Chapter II
VENTILATION AND AIR-POLLUTION CONTROL
INTRODUCTION
In the discussion of any ventilation system for a metal-finishing operation, two distinct areas
should be covered. These areas are
• The ventilation of the fumes from the work area
• The removal of any contaminants from the exhaust stream that can cause an air-pollution
hazard
In addition to a general discussion of these points, this part of the paper will also deal with
some of the operating and design principles upon which ventilation and air-pollution-control equip-
ment is based. It is mandatory that the owner and operator of the metal-finishing equipment have
a general idea of the principles involved so that he can make the best selection of design and equip-
ment for his own application. In the final analysis, the owner is the one responsible for the proper
operation and function of the equipment.
Even if he has recourse back to the supplier, the owner should never assume that a vendor's
"guarantee" absolves him of all responsibility. The owner also should consider carefully all vendors
to assure that, if legal recourse is required, the vendor is economically strong enough to back up his
guarantee.
The owner should also be able to understand the operating and design principles behind the
vendor's equipment well enough so that he has a high degree of technical confidence in the vendor's
guarantee. It is ludicrous for the owner not to be able to judge the technical merits of the design
and operation of any vendor's equipment when he is the one responsible to the pollution-control
authorities for the proper operation of his plant and equipment. For this reason alone, the owner
should be competent to analyze and compare the vendor's equipment and quotation beyond the
simple "first cost price comparison." When the control authorities want to padlock the door for
creating an air-pollution hazard, they will not be impressed by how much money the owner saved
by purchasing the least expensive equipment.
To prevent action by any air-pollution authority, the owner must be confident that the equip-
ment he selects will perform satisfactorily for many years, will satisfy the existing air-pollution
requirements, and will meet all other codes and regulatory requirements, including the Occupational
Safety and Health Act (OSHA).
41
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VENTILATION
OSHA Considerations
OSHA1 has specific guidelines for the design and evaluation of exhaust systems.
The primary requisite for any ventilation system as required by the OSHA is to assure that
any airborne toxic material be held below the threshold limit value (TLV) or the maximum
allowable concentration (MAC). Both the TLV and MAC mean essentially the same thing in that
it has been experienced that this concentration of toxic materials will not affect materially the
health of any worker so exposed for a period of 8 hours per working day for his entire working
life. Hie values of the TLV are those determined by various governmental agencies; the OSHA does
include a listing of these as published by the American Conference of Governmental Industrial
Hygienists.2
In addition to the requirement that all ventilation systems "be adequate to reduce the concen-
tration of the air contaminant to the degree that a hazard to the worker does not exist," OSHA1
also lists a specific method for determining exhaust rates from each tank. This determination is as
published by the Committee on Industrial Ventilation's "Industrial Ventilation" handbook,2 12th
edition. It should be noted here that in most cases the ventilation rates recommended in this 12th
edition are higher than those listed for identical applications in previous editions. OSHA in effect
states that in many cases additional exhaust volumes are needed to control the contaminant at less
than the TLV in the area immediately surrounding the tanks being exhausted.
In the past, lower rates have accomplished this control in most applications. Care must be
exercised, however, in the initial design to provide an area where crossdrafts are a minimum. To
do this, the location of windows and doors becomes extremely critical and should be watched care-
fully in the vicinity where exhaust of the metal-finishing tanks is required. Other considerations-
such as traffic patterns, workflow, method of work movement, and location of personnel—must be
studied.
When planning a new system or revising an existing system, special emphasis should be placed
on how workers are exposed to possible contaminants. Obviously, the farther away you can keep
your workers and the greater the internal dilution, the lower exhaust rate required to keep contami-
nants below the TLV level. Fresh air movement into the area should be controlled such that it flows
past the worker at his work station.
These, then, are the considerations that should be taken into account in order to comply with
OSHA.
Other Factors
In addition to the foregoing considerations, there should be other factors that will help in the
overall design of the exhaust system designed and installed.
One of the most critical items in any ventilation system is the proper amount of makeup air
that is provided. The amount of makeup air should be slightly less than the total volume being
exhausted, but the amount of this difference should be less than 2-5 percent. Many ventilation
manuals state that the amount of makeup air should be greater than the amount of exhaust air.
When dealing with toxic contaminants and air-pollution-control requirements, however, it is
mandatory to keep control of the toxic fumes in the area where they can be removed effectively.
42
-------
Having a positive pressure within this area means that wherever windows are open or doors
are open, airflow will be out of the immediate area, and consequently toxic contaminants can find
their way into other areas of the building. In any building, it is suggested that the metal-finishing
operation where tanks are involved be segregated somewhat from the remainder of the area. In
this fashion, makeup air can be supplied to the remaining portion of the building at an excess quantity,
with sufficient air makeup to cover the slight negative values that would be found in the metal-finishing
tank area. This method, then, will insure that all airborne contaminants would be carried through the
ventilation system in the metal-finishing area, which has been specifically designed and constructed to
handle these contaminants.
Materials of Construction
Obviously, the ventilation system in the metal-finishing area should be constructed of corrosion-
resistant materials that are also fire retardant. Some of the considerations that should be given to
materials of construction would be the following:
• Corrosion resistance to contaminants being handled
• Physical strength of the materials
• Fire retardance
• First cost and installation cost
• Ease of modification
Over the past 15 years, it has been proven that solid plastic construction materials used in
ventilation systems offer many of these advantages at low first cost, and they are installed readily
by most personnel. Solid plastic materials available include polyvinyl chloride (PVC), polyethylene,
polypropylene, glass-reinforced polyester, as well as other glass-reinforced thermosetting materials.
The first three materials listed are thermoplastics, which are by their very nature susceptible
to heat degradation at high temperatures but are effective when it is expected that operating tem-
peratures within the system are kept well below the upper operating limits generally recommended.
These operating limits are as follows:
PVC, 140° F
Polyethylene, 200° F
Polypropylene, 230° F
Thermosetting resins, such as glass-reinforced polyesters, do not exhibit the same physical
strength loss with increase in temperature and do expand at a slightly lower rate than most of the
thermoplastics. Glass-reinforced polyesters used in ventilation systems have operated successfully
at temperatures in excess of 250° F. They can be made fire retardant, and will contain fire and
smoke should a fire occur.
Although PVC generally is regarded as noncombustible, it does give off copious quantities
of HC1 when burned, and will drop flaming globules when exposed to a fire. In several cases, PVC
fires have snuffed themselves out in a relatively short period of time, but extensive structural steel
damage has been caused by the large amount of HC1 generated. In other cases, it has been shown
that PVC has spread the fire by dripping these flaming globules of molten PVC plastic. Polyethylene
43
-------
is combustible and generally is not recommended where fire retardance is a prime requisite—which
should always be the case in a metal-finishing operation. Polypropylene is available in fire-retardant
grades, but this material will bum at a faster rate than a comparable glass-reinforced polyester.
The key to the effective design of any ventilation system is to follow some specific guidelines.
The "Industrial Ventilation" manual2 offers excellent advice about the basic components of the
ventilation system.
In addition to this information, it is recommended generally that duct velocities in the range
of 2,500-3,500 ft/min be used for ventilation systems for metal-finishing operations. This range
generally keeps the static pressure in the total duct system to a reasonable amount, generally in the
range of 1.5-3 inches water gage.
Hoods
Exhaust hoods should be designed to insure the capture of all fumes generated from the
tanks. It is important to remember that the maximum fuming occurs when the work is placed in
the tank and as the work is removed from the tank. It is mandatory, therefore, that the pickup
points be arranged to capture the fumes in these areas. If the tank is hot the fumes tend to rise;
therefore, pickup points should be installed above the point where the maximum height of work
occurs during this transferring operation.
In addition to consideration for the pickup points, additional consideration should be given to
providing baffles of some type around the immediate hood itself. The addition of 12 inches or more
of baffles beyond all extremities of the hood can increase materially the effectiveness of the removal
of the contaminants from the tank area. It is surprising how much more effective a hood can be when
it is baffled and when the pickup points are located properly.
In general, for most metal-finishing operations, slot hoods are used, as these tend to give equal
distribution to the suction of the fumes across the width of the tank. Slot velocities in the slot
hoods are kept generally in the range of 2,000-3,000 ft/min, due to the high static pressure created
with this type of arrangement. A slot hood with this velocity generally will have no more than
%-% inch static pressure for the hood itself.
The design of the hood in the duct system should be based on the following premises:
Containment of the Fumes. The fumes should be kept in the tank area until they can be picked
up thoroughly by the exhaust hood. Additional baffles or artificial walls will assist in this operation.
Baffles tend to eliminate the crossdrafts and also help to contain the fumes in the tank area. It is
sometimes evident that baffles are also required directly above the maximum height of work to con-
trol the fumes from rising too rapidly before they are picked up into the exhaust hood.
Controlled Airflow Into the Fuming Area. The placement of the tanks within the room and
the location of items that can contribute to crossdrafts should be studied carefully. The objective
is to maintain the flow of air into the tank area in such a fashion that it constantly flows past the
work stations and toward the exhaust hoods. A study on paper of the location of windows and
doors, as well as of the location of the tanks themselves in relationship to these openings, is impor-
tant. Consideration for baffles and rearrangement of tanks within a given area can sometimes
eliminate problems and reduce the total amount of ventilation required to keep the contaminants
below the TLV in the work area. Baffles extended on either side of the tanks, as well as between
all hoods, as mentioned earlier, help the orderly flow of air into this area and generally assist the
exhaust system in performing its vital function, that is to say, removal of the contaminants.
44
-------
Removal of the Fumes From the Tank Area. Although it may seem redundant, it is important
that this third item be included with the first two because the amount of exhaust air used for a given
tank or tanks must be adequate to remove the fumes from the area in which they are being contained
as quickly as possible. Obviously, an inadequate amount of exhaust air allows the fumes to linger
in the exhaust area for too long a period of time, permitting their eventual escape into the room
itself with possible contamination of the entire working area. In general, the exhaust volume should
be 100-200 cfm for heated tanks and not less than 50-75 cfm for cool tanks. However, the "Indus-
trial Ventilation" manual2 or OSHA1 should be studied before any exhaust volumes are defined in
a given situation. The values given here can be used only if the fumes are contained and the airflow
into the area is controlled as indicated above.
Ductwork
In addition to the design and location of the hoods and other items, some consideration should
be given to the runs of ductwork themselves. The duct runs should be sloped and drainage points
provided so that condensation on the interior of the duct walls can be controlled. The duct construc-
tion material should be such that if a leak occurs due to physical damage, repairs can be effected
easily to eliminate this potential source of pollution into a sewer system not equipped to handle
toxic contaminants. In general, the design of the duct system should follow the guidelines outlined
in "Industrial Ventilation"2 with some consideration given to standard practices within the plastics
industry. For instance, in most instances plastics fabricators use an elbow turning radius of V/z times
the diameter of the duct rather than two times the diameter as recommended in "Industrial Ventila-
tion."2 This practice is merely a compromise between static pressure loss and initial cost of materials.
Fans
The exhaust fan is the heart of any exhaust system. Without the fan providing the necessary
suction and the necessary air movement through the hoods, duct system, scrubber, and stack, there
can be no exhaust system.
The exhaust fan should be sized to handle the full exhaust volume at the static pressure for
which the system is designed. Since metal-finishing installations traditionally are modified over
the years, it is suggested that the fan selected be of such a size that additional capacity can be added
at a future date by changing the motor and drive arrangement.
The fan manufacturer should be consulted to make certain that the fan selected is at the
"midpoint" of the performance range for the particular fan size. The design engineer should make
certain that the fan is constructed so that this additional capacity can actually be realized at a future
date. He should beware of furnishing a class I fan when an increase in cubic feet per minute or
slight change in the static pressure would require class II construction. This warning also applies to
the differential between class II and class III, especially where metal fans are involved. In some
cases, solid plastic fans have similar restrictions, and care must be exercised in making these
selections.3
In any metal-finishing ventilation system, it is advisable to make certain that the fan is com-
pletely corrosion resistant on the inside as well as the outside of the fan itself. That corrosion of
the exterior housing surfaces of a fan can lead to premature failure of the fan when the interior
has an expensive corrosion-resistant system is humorous but sometimes all too true, and is un-
necessarily expensive.
The most critical part of the fan is the impeller itself. It is important to make certain that the
impeller is of adequate design and structurally strong to handle any increase in capacity at any future
date.
45
-------
The impeller should be constructed of materials that are completely corrosion resistant to the
expected fumes that the fan will handle. If the fan is supplied with a coated impeller, it should be
specified that the coating installer must spark-test this fan after it has been balanced. If the coating
so applied is a thermoplastic coating, this coating should be supplied in adequate thickness for the
corrosion protection involved. Particular attention should be given to the tip speed of the impeller.
It is important to make certain that the centrifugal forces do not exceed the bond strength of the
coating material, causing the coating to fling off and fail prematurely.
If the fan impeller is constructed of a thermosetting fiberglass-reinforced polyester, then it is
important that it is in fact solid plastic construction and that it is built of the same resin as the
remainder of the duct system. Again, particular care should be taken to insure that the resin
selected has adequate corrosion resistance to all the contaminants the fan is expected to handle.
Construction of the fan should include an inspection door and housing drain. The housing
drain helps to insure adequate drainage of the condensation caused by the natural centrifugal force
of the fan impeller rotating within the housing. Since in many cases the exhaust stream coming
from the metal-finishing operation is saturated heavily with liquid droplets, the liquids can be expected
to build up within the fan housing very rapidly. Therefore, a drain should always be used on any fan
involved on a metal-finishing application. This drain should be connected to a seal leg so that it can
drain away the liquid properly without having to overcome the negative static pressure that may be
encountered on the inlet side of the fan. An access door on the side of the fan housing should be
provided so tnat inspection of the fan impeller can be accomplished with minimum difficulty.
This access also permits cleaning of the fan impeller by washing or similar action. Cleaning of the fan
impeller will help to extend the service life of the fan itself.
After the fan impeller, the fan housing is the next most critical item to which attention should
be paid. The interior of the fan housing should be coated with the same material as the fan impeller.
If all internal surfaces are coated as mentioned earlier, it is recommended that the exterior of the
fan be provided with some type of corrosion protection as well.
If the fan housing is of steel to which a coating will be applied, then it should be so constructed
that the coating can be applied with integrity. This means that all welds should be ground smooth
with a slight radius in all corners. (Note that a steel impeller must have similar preparation.) All
coatings should be spark tested after they are applied to the fan housing, and the coating should be
carried through to the outside of all flanges and should overlap the edges of all comers.
If the fan housing is solid plastic, then it should be stiffened adequately to withstand the nega-
tive static pressures that may be encountered during normal operation or at some future date.
In addition to the foregoing considerations, both the fan housing and impeller should be
constructed of materials that are basically fire retardant. In the remote event of a fire occurring in
the ventilation system, the fan should be kept on to remove the smoke and fumes from the burning
area through the exhaust system to the outside of the building. Smoke damage within the building
itself sometimes can be more costly than the fire damage to a localized area of the exhaust system.
There are several additional accessory items that should be provided to facilitate installation
and operation of the fan. One such item is the flexible connector used to connect the ductwork
to the inlet and discharge sides of the fan, isolating the fan from the remainder of the duct system.
Use of these connectors tends to reduce the sound transmitted by the fan to the entire ventilation
system, and also will reduce any vibration that the fan may transmit to the duct system.
Another additional accessory item used with fans should be the vibration isolator. Depending
on the location of fan mounting and the type of mounting supports, vibration isolators definitely
46
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should be included in all fan installations. This accessory serves the same function as the flexible
connector; that is, it tends to reduce the transmission of noise and vibration from the fan to
surrounding systems.
Drains
In conjunction with the exhaust system and fan, condensate drains have been mentioned. It
should be pointed out that these condensate drains should be connected to the waste-treatment
area. These drains are a potential source of toxic contaminants, and special provisions should be
made to connect these drain systems to prevent contaminants from entering the normal sanitary-
drain system or storm-water system. Note that some hoods are also provided with condensate
drains. These drains should be connected to a seal leg or capped for periodic drainage. This effort
will prevent exhaust air from being drawn into the drain and reducing the effectiveness of the hood.
These drains also should be connected to the metal-finishing waste-treatment system.
AIR-POLLUTION CONTROL DEVICES
Introduction
Metal-finishing operations that are carried on within liquid tanks create in general two different
types of emissions; that is to say, emissions of a gaseous nature, and emissions of entrained liquid
particulate. In very rare instances, mists are formed, but these occurrences are so infrequent that
they will not be a subject of discussion in this paper.
Gaseous contaminants can be defined as those specific contaminants composed of gas
molecules that are controlled by their brownian movement and are generally in the range of less
than 0.01 micron in particle size.
Entrained liquid particles are contaminants that are released from a bath due to air agitation,
drippage, mechanical agitation, and so forth, and that are generally 10 microns in size and larger.
A micron is defined as one-millionth of a meter, which is equivalent to roughly one twenty-
five thousandth of an inch. For reference purposes, it should be noted that the smallest individual
particle that can be detected with the naked eye has been reported to be between 60 and 100
microns in size. The average human adult red blood cell is 7.5 ± 0.3 microns in particle size.
Tobacco smoke generally is defined as composed of solid particles that range from 0.01 micron
to 1 micron in particle size. These points of comparison would give the metal-finishing operator
some appreciation of the size of the particles with which he is dealing.
The amount of air-pollution-control equipment required and the efficiency with which this
equipment must work will be dictated by local, State, and Federal Environmental Protection
Agency (EPA) regulations. Due to the nature of the specific contaminants and the myriad of
possible chemicals involved in metal-finishing operations, however, the present regulations are not
specific enough to permit a discussion in this paper of the maximum emission levels for individual
chemicals. In some cases, emission levels are specified as a maximum rate per pound of work
processed. In other cases, there is no specific mention of any of the normal contaminants found
in a metal-finishing operation. Some States do have emission regulations for such items as hydro-
gen fluoride, sulfuric acid, and hydrochloric acid, where a large segment of the State industrial
complex handles such items.
47
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There is a trend by the EPA to spell out, in some detail, limitations on specific contaminants.
It is expected that such limitations will be established in detail for the metal-finishing industry in
the very near future. In the meantime some companies, in an effort to anticipate tentative goals,
have established that the scrubber or pollution-control device they install shall have an outlet
concentration of contaminants that does not exceed the TLV.
There have been specific cases in the past where metal finishers have been subjected to the
"nuisance" clause. The nuisance clause usually is included in most regulations; it is included spe-
cifically so that no industry or company can interfere with the right of any individual to the pursuit
of his happiness and well-being or cause a nuisance that interferes with that basic right. There have
been specific cases where metal finishers have chromic acid emissions that have caused damage to
nearby property and houses. These cases have forced the particular company involved to make
restitution for this damage. Subsequently, the company involved has been obligated to install
pollution-control equipment that will remove specifically all the chromic acid contaminants passing
through the system. There have been other similar cases involving other types of contaminants,
but it should be noted here that proper planning and care in the design of the exhaust system as
well as in the selection of the air-pollution-control device will preclude such instances.
As mentioned earlier, because of the fact that most contaminants coming from a metal-
finishing operation are either gaseous or entrained liquid particulate in nature, wet scrubbers
generally have been used for this type of operation.4 Wet scrubbers are considered to be a chemical
type of pollution-control device (as opposed to a mechanical or electrical device).
A packed tower generally is recommended for control of gaseous contaminants. There are some
scrubbers on the market that do provide a limited amount of gas absorption through some other
means other than a packed bed. The amount of absorption provided is limited, however, and if the
objective is to reach the TLV on the discharge side of the wet scrubber, then a packed-tower absorp-
tion device definitely will be required. The packed-tower scrubber generally uses a recirculation
system to recirculate the absorbing liquid through and across the packed bed. There are several
different geometric modes of configuration for a packed tower. The geometric mode concerns itself
with the manner in which the liquid comes in contact with the gas. In a countercurrent packed column,
the liquid enters the top of the column and flows countercurrent to the gas stream, which enters the
bottom of the packed column. In a crossflow packed column, the gas flows horizontally through a packed
bed; the liquid flows from the top of the packed bed down to the bottom of the packed bed and discharges
at the bottom while the gas discharges through the rear of the packed bed (see figs. II-l and II-2).
For liquid-entrainment removal, wet scrubbers of various designs have been employed effec-
tively to obtain efficiencies in the range of 99 percent removal or more. The nature of the liquid
entrainment coming from the metal-finishing operation must be studied carefully. If the tank is at
room temperature, the entrainment generally will be relatively large, that is, probably 100 microns
or larger. For this particular type of liquid entrainment, a simple air washer, which is essentially
an entrainment-removal device with a washing action to keep the concentration of the contaminants
to a minimum, is all that is required. If the tank is heated, however, there is some concern that
smaller particles will be generated. In this particular case, the air washer or entrainment separator
should be selected with care, since there is a possibility that liquid particulate matter as small as 10
microns in size can be emitted.5
In the case of chromic acid fumes, it is important to remember that even a very small
particulate droplet of chromic acid can cause damage to painted surfaces. For this reason, an
entrainment-removal device that is efficient down to the range of 3-5 microns generally is
recommended.
48
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Recovery of Contaminants
There have been many installations where the recovery of contaminants from a metal-finishing
operation has proven to be economical. In general, in order to recover the contaminants economi-
cally, the water used for washing and dilution must be evaporated to increase the concentration of
the contaminant to a level where it can be reused back into the metal-finishing process.
An evaporator, using a supply of heated water, generally is recommended for such applications
as nickel-plating and chrome-plating operations where recovery can be economical. Table II-l shows
the results of such an evaporator design and indicates the approximate range of in\e\ concentrations
over which an evaporator can be economically effective.
There are many cases where an evaporator can be combined effectively with a wet scrubber.
That is, the wet scrubber serves a dual function—removal as well as recovery of contaminants. In
order to accomplish this function effectively, additional equipment must be provided. This addi-
tional equipment involves a heat exchanger and extra piping, as well as arrangements to run a batch
operation through the evaporator/wet-scrubber system. In this particular case, the scrubbing liquid
is heated to a point where water is evaporated from the airstream while the contaminant is being
removed within the packed bed.
There are some cases where a separate evaporation system can be justified economically. A
separate evaporation system will be employed where a number of small scrubbing installations are
handled separately, and the liquid from each of these is fed to a single evaporator system.
Water Consumption
A wet scrubber, to be efficient, must raise the relative humidity of the exiting air to the
saturation level. Since the relative humidity on the inlet side of the scrubber is generally less than
the saturation level, evaporation of water takes place within the scrubber itself. For this reason,
a makeup supply of some type of relatively "fresh" water must be added to the scrubber recircula-
tion system. The amount of water used as makeup must be greater than the evaporative losses that
can be expected within the scrubber itself.
If the contaminant being removed is of a gaseous nature, then the amount of fresh water added
to the system must be of sufficient quantity and quality to permit the recirculation solution to be
kept well below the level at which the concentration of the contaminant in the liquid phase does not
interfere with the gas absorption rate. For most metal-finishing operations, this amounts to a make-
up rate of approximately 5-10 percent of the total amount being recirculated in the scrubber system.
In addition to the above considerations, it may be necessary to consider maintaining the con-
centration of the contaminant in the overflow of the scrubber in the range where it can be handled
effectively by the waste water-treatment system that has been installed.
Since the overall consumption of water for any metal-finishing operation is limited in order
to keep the capital investment of the wastewater-treatment system to a minimum, the source of
fresh water for the scrubbing system should be studied carefully. While it is best to use fresh city
water for the scrubbing solution, in some cases the fresh water can be the clarified water from the
waste-treatment system. That is, the treated water from the waste-treatment system could be
returned to the scrubbers as the fresh-water supply, leading to recycling of the stream. This
recycling will tend to reduce the amount of city water being used in the system.
In addition to the foregoing arrangement, there are other arrangements where the rinse water
from the secondary or tertiary rinse tank can be used as the fresh-water makeup for the scrubber.
49
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Table 11 -1 .—Typical operating data for chrome- and nickel-plating evaporator/scrubber systems
Recovery data
Parameter:
Inlet air:
Rate, CFM
Temperature/relative humidity
Steam use pounds per minute at 25 psi ....
Total electrical use, amperes at 440 V
Recycle rate gallons per minute . . .
Heat exchanger temperature
Reservoir temperature
Evaporation rate gallons per minute . .
Return rate to tank, gallons per minute
Output air:
Temperature
Relative humidity
Hourly reclaim rate, pounds per hour expressed
as chrome or nickel solution
Average value over
test period
Chrome
10,000
77° F/40%
120
200
225
150°-155° F
114°F
9:5
1.5
131° F
100%
215
Nickel
10,000
77° F/40%
120
200
225
150°-155° F
114° F
9.5
1.5
131° F
100%
83
Operating costs
Dollars per hour
Item:
Electrical at 1.5 cents per kW-h
Steam, at $1.50 per 1,000 pounds
Total cost per hour
Reclaim cost per pound CrOo
Original chrome cost per pound .
0.35
10.75
11.10
052
.50
0.35
10.75
11.10
.134
1.50
Note.—Based on actual case study using countercurrent-flow packed-bed scrubber, containing 4 feet of 1-inch Tellereties.
50
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The concentration of the contaminants in the fresh-water makeup to the scrubber must be kept to a
sufficiently low value to preclude any release of the contaminants to the airstream in the scrubber
itself. In some cases, even the primary rinse tank may have a sufficiently low concentration to
permit using this water as the makeup water to the scrubber.
As a further water-conservation practice, there have been cases where the overflow from the
scrubber has been used as makeup for a primary rinse tank. This practice would be especially
beneficial when more than one rinse tank is employed in a process.
The exact nature of the supply of fresh-water makeup for a scrubber system can only be
determined upon detailed examination of the specific application. Each application must be
weighed carefully with all the alternatives previously mentioned carefully considered, and the final
selection must be based on the merits of the case in point.
With the recirculation piping, drainline piping, and other piping connections on the scrubber,
care should be taken that all of these are connected to the wastewater-treatment system.
Costs
Table 11-2 illustrates typical costs for the installation of ventilation and air-pollution-control
equipment for some typical metal-finishing operations.
The number of tanks being exhausted, as well as exhaust rate, together with the size of the
individual equipment selected, will control the actual installation and operating costs.
Care should be exercised in the selection of the air-pollution-control equipment so that the
operating cost is not excessive. It is important to remember that, as a rule of thumb, the operating
costs of each motor used on the ventilation and air-pollution-control system will range from $50
to $100 per brake horsepower per year, depending on local electrical costs. On a large system,
this cost can mount up quickly to a point where the savings of several inches of static pressure of
resistance within the system by careful selection of the pollution-control equipment and design of
the ventilation system can save many thousands of dollars of operating costs in a year's time.
Other Considerations
In appendix B of this paper are some examples of ventilation systems employing air-pollution-
control devices that have been installed in metal-finishing operations at various locations through-
out the country.
In addition to the design considerations listed earlier, there are several items that should be
mentioned in the ventilation of metal-finishing operations. These items should be taken into
account on any installation.
If the metal-finishing operation includes cyanide salts as one type of metal-finishing solution
and the cyanide tanks must be exhausted, then the exhaust system for the cyanide solutions should
be kept separate from any exhaust system that incorporates acid solutions. This practice will pre-
clude the formation of any hydrogen cyanide within the exhaust system itself, which could lead
to potential problems.
Normally, if there are alkali solutions containing no cyanide salts that must be exhausted,
they can be introduced into an exhaust system handling acid solutions so that some neutralization
can be effected within the duct system before reaching the scrubber. This practice will serve to
51
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Table \\-2.-Typical costs of ventilation system
Metal-finishing operation
Chrome
Nickel
Zinc
Phosphate coat
Type of
scrubber
Countercurrent
Air washer
Crossflow
Air washer
Pressure drop
Of
scrubber
Inches
2
1
1.5
.7
Total
Inches
4.5
3.5
4.0
3.2
Liquid rate
of scrubber
recirculated1
gpm
120
60
60
50
Horsepower
Pump2
0.7
.4
.4
.3
Fan3
12.8
9.4
11.5
9.1
First cost
of scrubber,
approximate
Dollars
6,000
3,500
7,000
3,000
Annual
power
cost4
Dollars
1,490
837
1,024
810
Total installed
cost, complete
system
Dollars
12,000
9,000
13,000
8,000
Ul
to
' Fresh makeup rate will be from 5 to 10 percent of figure shown, but no less than 3 gpm.
2pUmphP= 8'33Hs<9Pm>
M M 33000 (50% eff)'
3.. . .000157 Q (includes w.c.)
Fanhp= 55% eff
Operating cost = hr (hp) (.746) (1.5).
Note.—Basis of comparison: 10,000 CFM for all systems; static pressure loss in all air-handling systems exclusive of scrubber is 2.5 inches water gage; fan efficiency, 55 percent;
pump efficiency, 50 percent; annual operating days, 300; power cost, 1.5 cents per kilowatt-hour; all scrubbers 95 percent efficient or better.
-------
reduce the load of acid contaminants entering the waste-water-treatment system. This step should
not be taken, however, if recovery of the acid contaminants is being attempted.
There are some metal-finishing operations that use an ammonium-based alkali within the tank
system. Any exhaust system that is venting an ammonia tank should be kept separate from an
exhaust system that is handling hydrochloric acid. The combination of ammonia and hydrochloric
acid in an exhaust system forms the compound ammonium chloride (NH4C1). Ammonium
chloride, when it is formed, becomes a submicron particulate matter that is impossible to remove
in any of the wet scrubbers discussed in this presentation. Ammonium chloride can appear as a
dense white cloud that can lead to serious problems. The metal-finishing operator who has an
ammonium chloride effluent may find himself faced with complaints from local citizens due to the
reduced visibility in the plant area. The simple expedient of separating these two exhaust streams
internally, making certain that the hydrochloric acid vapors are removed to a high efficiency, and
then separating the exhaust points of the two by as wide a distance as possible will help to preclude
this possibility.
CONCLUSION
The design of a ventilation system for metal-finishing operation should be based on OSHA
considerations within the building. The specific manner in which the exhaust fumes are contained
within the area and removed through the exhaust system should be studied carefully so that the
contaminants are kept within a confined area. The flow of fresh ah- should be constant past all
work stations so that the TLV of the contaminants is not exceeded.
The exhaust system should be designed so that it uses a minimum of static pressure resistance
to keep the operating costs down. Materials of construction used should have corrosion-resistant
characteristics combined with fire-retardant characteristics so that the effectiveness of the exhaust
system does not deteriorate with age.
The fan and the pollution-control device selected should be constructed of similar corrosion-
resistant and fire-retardant materials. The air-pollution-control device selected should be efficient
enough to allow operation under existing codes. Some provisions can be made in many scrubber
designs to increase the efficiency at a later date. Care must be used in this selection, however, so
that the fan capacity can be increased at slight additional costs at some future date.
All condensate drains and drainline connections to the wet scrubber should be directed to the
waste-treatment system to prevent contamination of ground water, sanitary, or storm-sewer
effluents.
Careful consideration of the fresh-water makeup to the wet-scrubber system should be included
in the overall planning of the wastewater-treatment system.
A detailed evaluation of any vendor's proposal for the complete exhaust system and/or
pollution-control devices should include the major points covered in this paper.
53
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REFERENCES
Department of Labor, "Occupational Safety and Health Standards," Occupational Safety and
Health Administration, Federal Register, vol. 36, No. 105, pt. II, May 29, 1971.
2 Committee on Industrial Ventilation, Industrial Ventilation, 12th ed., American Conference
of Governmental Industrial Hygienists, 1972.
3 Johli S. Eckert, "Use of Packed Beds for Separation of Entrained Particles and Fumes From
an Air Stream," APCA Journal, vol. 16, No. 2, Feb. 1966.
4E. B. Hanf, "A Guide to Scrubber Selection," Environmental Science and Technology vol 4
No. 2, Feb. 1970.
5E. B. Hanf, "Fume Washers for Medium and Small Size Plating Shops," Plating, vol. 58
No. 12, Dec. 1971.
6 Dr. A. J. Teller, "New Engineering Concepts in Pollution Control," Engineering Digest Aug
1970.
54
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Cleaned
Gas
Contaminated
Gas
I
— -4 "
I |
1 *~
1 //
1
l
-i
-r~ |"
\ X 1
1
1
ijrtijn ,p5-rLQjD TIT pjrlsl
Liquid Inlet
Counter-Current Flow
Figure 11-1. Countercurrent packed-bed scrubber.
55
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Liquid
Inlet
Contaminated
Gas
Ol
Cleaned
Gas
Crossflow
Figure 11-2. Crossflow packed-column scrubber.
-------
Chapter III
CORROSION PROTECTION OF FLOORS AND EQUIPMENT
FLOOR PROTECTIOM
In the consideration of any wastewater system, some means of surface protection of the floor
area around the tanks is always included. Surface protection of the floor is required to protect the
substrate (actual floor material) from damage due to spills, splash, drippage, overflow, or catastrophe.
In the event of a catastrophe, it is imperative that the liquids involved all be contained within the
area serviced by the wastewater-treatment system provided. Depending on the specific design used
and the extent of the catastrophe, spill, or other problem, the liquids involved may have to be con-
tained within this area for from several minutes to several hours. Obviously, the liquids could cause
severe damage to the substrate and even the building and/or building foundation if the area is not
properly protected.
The type of material selected for this service should be based on the following considerations:
• Substrate material
• Type of traffic, if any, that will be using this floor area
• Broad-range corrosion resistance
• First cost
• Ease of installation and its cost
• Repairability
There are many different types of materials available on the market. Most of these materials
are considered to be monolithics and are based on the use of a thermosetting resin. Thermosetting
resins are those resins using a catalyst system. They start off at room temperature as a liquid to
which the catalyst is added and, depending upon the amount of catalyst and the temperature and
humidity, the resin "sets up" or becomes a solid with an exothermic reaction within from 5 minutes
to several hours. Once this exothermic reaction is complete and the heat has dissipated, the resin is
fully cured and usually can be treated in the same manner as the substrate. The complete cure may
be complete within several hours, but most materials should not be subjected to anything other than
foot traffic for from 24 to 48 hours after being fully installed. Thermosetting resins include epoxies,
polyesters, and furans, although most floor-protection materials are based on either epoxies or poly-
ester resins.
It is imperative to point out that there are probably well over 100 different epoxy resins avail-
able, as well as over 500 different polyesters. However, limiting the materials to the foregoing con-
siderations probably will reduce these numbers to 20 and 100, respectively, for epoxies and polyesters.
With this variety still available, the ideal material should be selected based on the following
parameters:
57
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• Corrosion resistance to a wide range of acids and alkalis
• Low first cost and installation cost
• High resistance to impact damage
• High bond strength to substrate
• Visual-inspection capability and ease of repair
The only other consideration is the amount of traffic or type of load to which the material
will be subjected. In some cases, the materials are applied using nothing more than an aggregate or
other type of filler. The aggregate is used to enhance impact strength and thermal expansion char-
acteristics, and to provide additional thickness of material. In other cases, the same materials or
slightly different formulations are used in conjunction with some type of additional reinforcement,
such as glass cloth.
Reinforcement with glass cloth markedly increases the impact strength of the material. It also
enhances other properties that make this type of addition very valuable in many instances.
When taking all factors into consideration, a material that approaches the ideal would be a
modified glass-reinforced polyester. This material has the following properties:
• It is corrosion resistant to the vast majority of plating solutions.
• It has a total installed cost of from $2 to $3 per square foot, which makes it economical.
• It bonds tenaciously to the substrate and discourages undercutting so that cracks and damage
are contained within a localized area.
• The glass reinforcement provides high impact strength and permits the material to bridge
minor shrinkage cracks in the substrate.
• Cracks, if they do occur, can be repaired readily by maintenance personnel with minimum
training.
• Cure is complete within hours, so that downtime for repairs or interruption of initial con-
struction can be held to minimum.
• The material can also be applied to vertical surfaces so that curbs and walls can be given the
same corrosion protection. Thus, any chemicals involved in a catastrophic spill can be con-
tained within the designated area serviced by the water-treatment system.
The best material selected for floor protection service is wasted if the proper consideration is
not given to the overall design of the substrate, the method of installation of the material, and the
surface preparation. Areas that warrant particular attention include floor drains, joints between
walls and floors, and so forth. Illustrated here are the methods that are used generally to handle
these potential trouble areas.
Note that before the installation of any monolithic material the substrate must have the surface
preparation recommended by the manufacturer. For most monolithics, when concrete is the sub-
strate, the surface preparation is generally a steel-trowel finish followed by acid etching of the fully
cured concrete.
58
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PROTECTION OF EQUIPMENT
In addition to protection of the floor under the tanks, consideration should also be given to
protection of other areas. Whenever corrosive chemicals are used, all equipment exposed to the
same atmosphere or in direct contact with the chemicals is subjected to rapid degradation. Equip-
ment and areas in this category include the following:
• The exterior of the tanks
• All surfaces of a plating machine
• Structural steel used anywhere in the vicinity of the corrosive chemicals
• Utility connections or pipelines that are located within the area where floor protection is
provided
Equipment installed in a metal-finishing operation is expensive to replace. It is also extremely
expensive if the equipment must be repaired constantly.
One of the best questions that is always asked in conjunction with any discussion of catastrophes
in a plating area is, "How could they occur?" There is probably no better response or more likely
occurrence than "through the forces of corrosion and neglect." Therefore, it is economic folly when
considering floor protection not to investigate the possibility of providing similar protection to all
equipment contained within the floor area that will be protected.
With the normal maintenance that will be required by the treatment plant and equipment, as
well as by the plating equipment itself, corrosion protection of tanks, machinery, and structural
steel will reduce maintenance on these items, freeing personnel to maintain critical equipment. It
will also lessen materially the chances of a catastrophic event.
Corrosion protection for these parts and areas can be provided by coatings that are applied
readily by brush or spray and that have the same properties and corrosion resistance as the mono-
lithics used on the floor.
Typical of such materials is a flake-reinforced polyester. This material is available in the same
grades as the monolithics and can be applied to a thickness of from 15 to 30 mils at a nominal cost.
The typical installation will range from 80 cents to $1.50 per square foot, depending on the amount
of surface area being covered and the complexity of shape. This means that the material is competi
tive with most epoxy, vinyl, or similar paint systems used as coatings. The advantage of this type
of coating is its superior impact resistance, better thermal-shock resistance, lower expansion coef-
ficient, and resistance to undercutting.
The coatings mentioned here have been field proven in years of trouble-free service, where
they have eliminated the usual annual reapplication of materials that is normal with most paint sys-
tems in corrosive areas. They are also readily cleaned with a water flush and could even be brushed
with a stiff bristle brush without fear of damage.
OTHER CONSIDERATIONS
It is obvious that the area occupied by the waste-water treatment should receive the same con-
siderations. Although the function here is one of neutralization of corrosives, it should also be re-
alized that the same types of spills, leaks, splash, and other minor occurrences could cause serious
damage to floors, tank exteriors, structural work, and so forth.
59
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In addition, serious consideration should be given to the manner and means in which the
liquid effluent from the metal-finishing area is transported to the treatment plant. Pipelines
must be installed properly and completely corrosion resistant, both inside and out. Trenches,
if used, should be protected similarly.
In all cases, wherever corrosive chemicals are used within the plant, careful attention should
be given to corrosion protection of all surfaces in those areas where the chemicals are received,
stored, consumed, and transported to the waste-treatment plant, and where they are finally
neutralized.
60
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Appendix A
EXAMPLES OF VENTILATION SYSTEMS
USING AIR-POLLUTION-CONTROL DEVICES
V
riELO IOIWT
to
rs
8s
I J
.
t- U
.
2
a
g ,
I I
.Is!
-------
Oi
to
OPERATING CONDITION*
CUSTOMER
DESCRIPTION
cuvr. DWO. NO.
PRESSURE'DESIGN
PRESSURE-OPERAS HO
CONSTRUCTION
THE CEILCOTE CO., INC.
•ERCA (CLEVELAND), c
c-
-------
OS
CO
CONSTRUCTION
ITEM
DUR.ACOR VENTILATION SYSTEM
CUSTOMER
AR l
CO STEEL CO.
THE CEILCOTE CO., INC.
140 SHELDON ROAD BEREA (CLEVELAND) OHIO
PATE^-2S--47 SCALE
DRWN. U"V5
CHK'D.
DATE
B-
-------
Appendix B
EXAMPLES OF FLOOR PROTECTION
COATING APPLICATIONS
Expansion Joints
for monolithic floor
Monolithic Topping
Expansion Joint
Pre-formed Joint
Drains
for monolithic floor
Expansion Joint
Monolithic Topping
65
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Drains
for brick floor
Expansion Joint Material
Acidproof
Cement
Acidproof Brick
Membrane
Concrete slab
66
-------
ACIDPROOF BRICK &
MEMBRANE CONSTRUCTION
Membrane seals and protects concrete
substrate.
Acidproof brick protects membrane from
impact, abrasion, and thermal shock.
Acidproof cement bonds brick solidly in
place and prevents liquids from seeping
through to the membrane.
Acidproof Membrane,
Brick & Cement Construction
GROUTED
BRICK CONSTRUCTION
Ribbed bottom vitrified tile or brick set in
uncured base of cement and sand.
Tiles tamped evenly in place with i/4" joint
spacing.
Joints grouted flush with acidproof cement
after base cures.
^^^^
Grouted Brick Construction
67
-------
Brick Wall Coving
Flexible resin-based membrane pro-
tecting the concrete substrate is carried
up the wall behind coving. All joints
are made with acidproof cement.
Cove Brick
Acidproof Cement
Joints
Brick & Monolithic Column Bases
Both types are treated essentially the same as side-
wall covings for the respective materials.
Monolithic Wall Coving
Lining for Vail is applied first and
feathered down over the floor. Mono-
lithic floor topping is then trowelled up
to the side wall and the joint is addi-
tionally protected with polysulfide
sealant.
Monolithic Wall Lining
-Expansion Joint Sealant
Monolithic Topping
Monolithic Topping
Monolithic
Lining^
Expansion
Joint -
Expansion Joint
Acidproof
Brick
Monolithic
Membrane
68
-------
Monolithic Floor Combined
With Acidproof Brick Trenches
Trench is lined with flexible membrane. Brick is then
layed up with acidproof cement. Glass reinforced
monolithic floor topping is trowelled across the
header course to completely seal the joint between
the concrete trench and its brick lining.
Reinforced Monolithic Topping
a. • a
- a •
A d
•a
-
Membrane
1 1 1 1*1 1 1 1
Monolithic Trenches
Consists of reinforced monolithic lining material
specially formulated for vertical surfaces. Note that
lining runs up on to the floor, and that the floor top-
ping is brought to the edge of the trench to com-
pletely seal the monolithic joint.
Monolithic Topping
\ *!
Monolithic Lining
4 Glass Cloth
Reinforcement
i&ar \
& . a
Monolithic Pump Base
Top and sides of the base are covered with mono-
lithic lining which is feathered over the floor. Mono-
lithic floor topping is then trowelled on floor area and
lapped up the side of the base. Use of reinforcement
is determined by service conditions.
Monolithic Flooring
Monolithic Lining
..GOVERNMENT PRINTING OFFICE:I976-757-056/543l Region No. 5-11 69
-------
METRIC CONVERSION TABLES
Recommended Units
Description
Length
Area
Volume
'
Mass
Time
Force
Moment or
torque
Stress
Unit
metre
kilometre
millimetre
micrometre
square metre
square kilometre
square millimetre
hectare
cubic metre
litre
kilogram
gram
milligram
tonne or
megagram
second
day
year
newton
newton metre
pascal
kilopascal
Symbol
m
km
mm
/zm.
m2
km2
mm*
ha
m3
1
kg
9
mg
t
Mg
s
d
year
N
N-m
Pa
kPa
Comments
Basic SI unit
The hectare (10 000
m2) is a recognized
multiple unit and
will remain in inter-
national use.
The litre is now
recognized as the
special name for
the cubic decimetre.
Basic SI unit
1 tonne = 1 000 kg
1 Mg = 1 000 kg
Basic SI unit
Neither the day nor
the year is an SI unit
but both are impor-
tant.
The newton is that
force that produces
an acceleration of
1 m/s2 in a mass
of 1 kg.
The metre is
measured perpendicu-
lar to the line of
action of the force
N. Not a joule.
Customary
Equivalents
39.37 in.=3.28 ft=
1.09yd
0.62 mi
0.03937 in.
3.937 X 103=103A
1 0.764 sq ft
= 1.196 sq yd
6.384 sq mi =
247 acres
0.001 55 sq in.
2.471 acres
35.314 cu ft =
1.3079cuyd
1. 057 qt = 0.264 gal
= 0.81 X 10 4 acre-
ft
2.205 Ib
0.035 oz = 1 5.43 gr
0.01 543 gr
0.984 ton (long) =
1.1023 ton (short)
0.22481 Ib (weight)
= 7.233 poundals
0.7375 ft-lbf -
0.02089 Ibf/sq ft
0.14465 Ibf/sq in
Description
Velocity
linear
angular
Flow (volumetric)
Viscosity
Pressure
Temperature
Work, energy,
quantity of heat
Power
Application of Units
Description
Precipitation,
run-off,
evaporation
River flow
Flow in pipes,
conduits, chan-
nels, over weirs,
pumping
Discharges or
abstractions,
yields
Usage of water
Density
Unit
millimetre
cubic metre
per second
cubic metre per
second
litre per second
cubic metre
per day
cubic metre
per year
litre per person
per day
kilogram per
cubic metre
Symbol
mm
m3/s
m3/s
l/s
m3/d
m3/year
I/person
day
kg/m3
Comments
For meteorological
purposes it may be
convenient to meas-
ure precipitation in
terms of mass/unit
area (kg/m3).
1 mm of rain =
1 kg/in2
Commonly called
the cumec
1l/s = 86.4m3/d
The density of
water under stand-
ard conditions is
1 000 kg/m3 or
1 000 g/l or
1 g/ml.
Customary
Equivalents
35.314 cfs
IS.SSgpm
1.83X10-3gpm
0.264 gcpd
0.0624 Ib/cu ft
Description
Concentration
BOD loading
Hydraulic load
per unit area;
e.g. filtration
rates
Hydraulic load
per unit volume;
e.g., biological
filters, lagoons
Air supply
Pipes
diameter
length
Optical units
Recommended Units
Unit
metre per
second
millimetre
per second
kilometres
per second
radians per
second
cubic metre
per second
litre per second
pascal second
newton per
square metre
or pascal
kilometre per
square metre
or kilopascal
bar
Kelvin
deqr-» Celsius
joule
kilojoule
watt
kilowatt
joule per second
Symbol
m/s
mm/s
km/s
rad/s
m3/s
l/s
Pa-s
N/m2
Pa
kN/m2
kPa
bar
K
C
J
kJ
W
kW
J/s
Comments
Commonly called
the cumec
Basic SI unit
The Kelvin and
Celsius degrees
are identical.
The use of the
Celsius scale is
recommended as
it is the former
centigrade scale.
1 joule = 1 N-m
where metres are
measured along
the line of
action of
force N.
1 watt = 1 J/s
Customary
Equivalents
3.28 fps
0.00328 fps
2.230 mph
1 5,850 gpm
= 2.120 cfm
15.85 gpm
0.00672
poundals/sq ft
0.000145 Ib/sq in
0.145 Ib/sq in.
14.5b/sqin.
5F
T -17.77
9
2.778 X 10 7
kwhr =
3.725 X 10'7
hp-hr = 0.73756
ft-lb = 9.48 X
1048tu
2.778 kw-hr
Application of Units
Unit
milligram per
litre
kilogram per
cubic metre
per day
cubic metre
per square metre
per day
cubic metre
per cubic metre
per day
cubic metre or
litre of free air
per second
millimetre
metre
lumen per
square metre
Symbol
mg/t
kg/m3d
m3/m2d
m3/m3d
m3/s
l/s
mm
m
lumen/m2
Comments
If this is con-
verted to a
velocity, it
should be ex-
pressed in mm/s
(1 mm/s = 86.4
m3/m2 day).
Customary
Equivalents
1 ppm
0.0624 Ib/cu-ft
day
3.28 cu ft/sq ft
0 03937 in
39.37 in. =
3.28ft
0.092ft
candle/sq ft
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