p.1 

OAR Box 1313 

Prepped by LaTeia Shed 

Document Number: 

66) ll-B-40 

Docket Number: 

A-88-02 

Printed 6/12/2008 9:03:30 A M Sheet 66 of 99 
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MRI® MIDWEST RESEARCH INSTITUTE 

Suite .

,

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: 

-01 Harrison Oaks Boulev-n 

Gary. NC. 27? 1 

A-88-02 

Date: May 19, 1988 

(Finalized June 30, 1988) 

Subject: Site Visit—Saco Defense Inc., Saco, Maine 

Chromium Electroplating NESHAP 

EPA Contract 68-02-3817; ESD Project 85/02a 

MRI Project 7717-K 

From: Randy Strait 

To: Andrew Smith 

ESD/ISB/SSS (MD-13) 

U. S. Environmental Protection Agency 

Research Triangle Park, N.C. 27711 

I. Purpose 

The purpose of this site visit was to evaluate the single packed-bed 

horizontal-flow scrubber used to control chromium emissions from three 

hard chromium plating tanks. The scrubber system is being considered as a 

candidate for emission testing to determine the extent to which 

reconditioning can improve scrubber performance. 

II. Place and Date 

Saco Defense Inc. 

291 North Street 

Saco, Maine 04072 

January 25, 1988 

(207) 283-3611 

III. Attendees 

Saco Defense Inc. 

Robert Daigle, Manager, Manufacturing Services 

Robert Noonan, Senior Environmental Engineer 

Midwest Research Institute 

Randy Strait 

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IV. Discussion 

The visit began with a discussion about EPA's emission test program 

and the capture and control equipment used to control chromium emissions 

from the hard chromium electroplating tanks at the plant. The discussion 

was followed by a tour of the plating shop and an evaluation of the 

capture and control equipment. 

A. General 

Saco Defense Inc., is a large captive shop that manufactures 

military artillery. The plant operates 18 hard chromium plating tanks. 

Tanks 22 through 24 are controlled by a single packed-bed horizontal-flow 

scrubber; Tanks 33 through 36 are controlled by a vertical-flow packed-bed 

scrubber; and Tanks 1 through 4, Tanks 10 and 11, and Tanks 25 through 29 

are controlled by three separate horizontal-flow scrubbers. 

The focus of the visit was the single packed-bed horizontal-flow 

scrubber used to control emissions from Tanks 22 through 24. It is the 

only horizontal-flow packed-bed scrubbers at the plant. Detailed 

information on Tanks 22 through 24 and the single packed-bed scrubber is 

presented below. General information on the other four scrubbers used at 

the plant is presented in Section F of this report. 

B. Process Information 

Tanks 22, 23, and 24 are used to deposit chromium on the inside 

surface of artillery gun barrels. Based on operating parameters such as 

current, voltage, chromic acid concentration, and plating time, the 

plating tanks appear to be typical of other hard chromium plating tanks in 

the electroplating industry. Each tank is 2.4 meters (m) (8.0 feet [ft]) 

long, 0.6 m (2.0 ft) wide, and 1.3 m (4.2 ft) deep and holds about 

1,700 liters (450 gallons) of plating solution. The plating solution 

contains 247 grams of chromic acid per liter (33 ounces per gallon) of 

solution. The temperature of the plating solution is maintained at 60°C 

(140°F). Each tank is equipped with one rectifier with maximum ratings of 

12 volts and 3,000 amperes. Typically, 20 barrels are plated at a time in 

each tank at 2,000 amperes for 3.5 hours. Each tank is operated about 

20 hours per day, 5 days per week, 50 weeks per year. 

C. Emission Control 

Figure 1 is a plan view of the capture and control system for 

Tanks 22, 23, and 24. All three tanks are equipped with push-pull capture 

systems. Tanks 23 and 24 were not operating during the visit. In 

addition, plant personnel had turned off the push-air side of the capture 

system on Tank 22 because the push air forced chromic acid mist into the 

room air. Plant personnel speculated that the push air was not being 

drawn through the pull side of the hood either because of interference 

produced by the part racks in the tank and/or because of a potential 

deficit in makeup air. Even with the air curtain system offline, no 

visible emissions were observed escaping the capture system on Tank 22 

during the visit. 

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Fiyure 1. Plan view of capture and control system for hard chromium plating 

Tanks 22, 23, and 24 at Saco Defense. 

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Figure 2. Side view of single packed-bed scrubber for hard chromium plating 

Tanks 22, 23, and 24 at Saco Defense. 

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Chromic acid emissions from the plating tanks are vented to a single 

packed-bed horizontal-flow scrubber. The scrubber and fan are located on a 

mezzanine in a room next to the plating shop (see Figure 2) . The scrubber 

exhaust is discharged through a stack in the roof. 

The scrubber was manufactured by Duall Industries, Inc., (Duall) and 

installed in 1971. The scrubber is designed for an airflow rate of 

340 cubic meters per minute (12,000 cubic feet per minute) and a pressure 

drop of 0.5 kilopascal (2.0 inches of water column). The packed bed is 

about 0.3 m (1.0 ft) in depth, 1.6 m (5.3 ft) in height, and 1.7 m 

(5.5 ft) in width. The design face velocity of the airflow through the 

packed bed is 125 meters per minute (m/min) (410 feet per minute 

[ft/min]). The packing media used in the packed bed was manufactured by 

Protak. The packing media is made of polypropylene and consists of three 

concentric circles that form a sphere. Each sphere is 6.35 centimeters 

(2.5 inches) in diameter. The packing media has a surface area-to-volume 

ratio of 128 square meters per cubic meter (39 square feet per cubic foot) 

and a void space of 90.6 percent. 

A chevron-blade mist eliminator with a single set of overlappingtype blades is installed downstream of the packed bed. The mist 

elimination section is about 0.20 m (0.67 ft) in depth, 1.6 m (5.3 ft) in 

height, and 1.6 m (5.3 ft) in width. The design face velocity of the 

airflow through the mist elimination section is 130 m/min (430 ft/min). 

The scrubber is equipped with four spray nozzles located at the 

inlet of the scrubber and four spray nozzles that are located over the top 

of the packed bed. The design water flow rate to the scrubber is 

132 liters per minute (35 gallons per minute). The scrubber water is 

pumped through the spray nozzles, drained to a rinse tank, and 

recirculated continuously to the scrubber. The chromic acid concentration 

of the scrubber water is about 1.1 grams per liter (0.15 ounce per 

gallon). 

All four of the spray nozzles at the inlet are partially plugged, 

and no water was being pumped to the spray nozzles located over the packed 

bed. In addition, there is buildup of chromic acid on the packing media, 

inside walls, and mist elimination section of the scrubber. The frame 

holding the packing media is warped. This warping has allowed the packing 

media to settle, leaving an empty space between the top of the scrubber 

and the packing media. Consequently, a portion of the air stream was 

passing over, rather than through, the packing media in the packed bed. 

Duall has indicated that warping of the frame of the packed bed is 

not unusual for units that have been operated for several years. Warping 

of the packed-bed frame typically occurs when the strands of polypropylene 

that tie the walls of the packed bed together break due to wear. Ouall 

has agreed to inspect the scrubber and perform any maintenance needed to 

ensure that the scrubber is operating according to design specifications 

before any testing is performed. [Note: A Duall field representative 

inspected the scrubber on March 31, 1988. Results of the inspection are 

summarized in a trip report dated March 31, 1988 (attached)]. 

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D. Availability of Test Locations 

There appears to be sufficient length of straight ductwork between 

the exhaust plenum on tank No. 22 and the scrubber to allow for inlet 

testing. The ductwork is about 2.4 m (8.0 ft) in length and 0.76 m 

(2.5 ft) in diameter. Outlet testing can be performed in the stack 

located on the roof of the plant. However, a stack extension may need to 

be installed. 

E. Conclusions 

The scrubber used to control emissions from Tanks 22, 23, and 24 is 

a good candidate for emission testing for the following reasons: 

(1) operating parameters of the plating tanks are within the ranges 

typical of hard chromium plating tanks, (2) the type and amount of work 

plated will generate an emissions loading suitable for testing, (3) the 

scrubber design is representative of the packed-bed horizontal-flow 

scrubber designs previously tested, (4) there appears to be a suitable 

location for testing at the inlet of the scrubber, and (5) the scrubber is 

a used unit that can be tested to determine the extent to which cleaning 

can improve scrubber performance. 

The effectiveness of the capture systems on the tanks and the 

operating condition of the scrubber will need further evaluation before a 

final decision can be made on whether to test the scrubber. Plant 

personnel have hired an industrial hygiene consultant to evaluate the 

effectiveness of the capture systems on the tanks and will request Duall 

to evaluate the operating condition of the scrubber. Evaluations of the 

capture systems and scrubber are expected to be completed within 2 months. 

Saco Defense Inc., personnel were very cooperative during the visit 

and are willing to allow EPA to test the scrubber. Plant personnel 

indicated that they would have the ventilation system inspected and 

balanced to ensure that the ventilation system complies with industrial 

ventilation guidelines for chromium plating tanks prior to any emission 

testing. If selected for testing, plant personnel also have agreed to 

hire Duall to recondition the scrubber. The plant has offered to provide 

a hoist for test crew access to the scrubber inlet ductwork during the 

test. 

F. Additional Information 

The manufacturer of the vertical-flow packed-bed scrubber used to 

control emissions from Tanks 33 through 36 is unknown. The duct length at 

the inlet of the scrubber is not adequate for conducting inlet testing. 

The three horizontal-flow scrubbers that are used to control 

emissions from Tanks 1 through 4, Tanks 10 and 11, and Tanks 25 through 29 

are old units that were manufactured by CRECO, Inc., Owosso, Michigan. 

CRECO refers to their scrubbers as "air washers." A product information 

brochure for the air washer is presented in Attachment 2 of this report. 

Each of the air washers at the plant contains four filter pads that are 
P.8 

about 15 centimeters (6 inches) in depth. Each filter pad is a polyvinylchloride frame that is wrapped with one layer of woven mesh made of 

polypropylene. The filter pads in the air washers at the plant were 

empty; they were not filled with packing media. Water spray systems are 

located on both sides of the first filter pad. Chromic acid mist in the 

ventilation air is wetted by the spray systems and then impinges on the 

woven mesh as the ventilation air passes through the filter pads. 

2 Attachments 

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CRECO, Inc. 

GuAtom. Plastic QdtJucatvU 

500 Smith Avenue - P.O. Box 473 - Phone 517-725-5355 

OWOSSO. MICHIGAN 48867 

Item #1 Standard P.V.C is most commonly used and recommended. 

However, other material raay be substituted for fabrication 

of our Air Washer. 

Item *>2 Dimensions can be changed slightly for special conditions 

or circumstances. It is advisable to mention the problem 

involved for solutions and the temperature involved so 

we may make recommendations accordingly. 

Item #3 FPR Washers contain multiple washing filter packs. 2 stage 

washing with extractor filter packs for standard, and 

3 stage washing with 2 extractor filter packs for hard to 

wash fumes. 

Item #4 Efficiency expected to be up to 907. of all water soluble 

contaminates. 

Item #5 Only 1-1/4" to 1-1/2" of static pressure loss to be expected. 

Item #6 .Round or rectangular inlets and outlets are optional. 

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CREC O FPR AIR WASHER 

P V C FABRICATION 

Washers are shipped ready to install, but do 

not include Fan, Pump, Recirculation Tank or 

Piping. 

The Washer is equipped with a steel base for 

a ready means of securing the collector to 

its supporting media inside or outside of 

plant. 

The Washer is a self-draining unit. 

In most locations it is most economical to 

recirculate the water for units using more 

than ten (10) gallons per minute. 

If a recirculation tank and pump are used, we 

recommend the tank be located in a heated 

building for ease of adding a neutralizer as 

well as to guard against freezing. The top 

of this tank must be at least 12" below the 

base of the washer to insure proper drainage. 

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