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"The county was sure that our water meter was faulty. They tried to arrange for us to shut down so they could come in and take the meter apart and inspect it," stated Dale Diemer, environment, safety and health manager for Metal Seal and Products, Inc. (Willoughby, OH). The county had trouble believing that the company's water savings could be due to the new water recycling and wastewater system it installed for use with its anodizing, zinc plating and passivation processes. Eventually, Mr. Diemer convinced the county that the water savings was due to the new system, and the shutdown was avoided.
According to Gordon Diemer, plant manager and cousin of Dale, the whole system came about because the company was spending a "small fortune" on water and waste treatment. "We were also having a lot of plating problems, where we were probably reworking 12-15% of what we made," noted Mr. Diemer.
Major customers for Metal Seal include the automotive, plumbing and electronics industry, with automotive making up the majority of the work. Metal Seal handles all parts from start to finish. It receives the raw steel and aluminum and uses CNC machinery, drills, tappers, spindle and screw machines, among others to form the metals into parts. Parts for the automotive industry include mostly brake pistons for anti-lock brake systems, ABS components and other automotive and truck brake components.
Most of these parts are passivated, zinc plated or anodized. The zinc plating line was replaced a year and a half ago in order to increase capacity. The old line could handle approximately 60,000 pieces per day. The new line tripled the capacity of the previous line. However, the new installation was not without problems. Gordon Diemer tells of a frustrating, but now somewhat amusing story of what happened in one of the zinc plating tanks. "After we put in the new zinc line, one of our zinc plating baths went bad. We were getting terrible plating. We sent out a bath sample to Atotech for analysis, and it came back with formaldehyde in it. That was odd, and we did not know where it was coming from until we realized that someone had left the overhead door in the back open too long and some leaves had blown into the tank. When the leaves break down, they create formaldehyde. We had to dump an 8,000 gal tank, scrub it, passivate it, hose it out and make it up all over again. Not to mention the debris we found in the tank from the guys working on the roof putting in a new air duct: PVC, a screwdriver, fiberglass and a steak knife. I would not want to go through that again."
The zinc line is automated with five rack stations and one barrel station. Parts are manually loaded and then a PLC reads the bar code to determine the plating sequence for the parts.
The new water recycling and waste treatment system from Kinetico Inc. has helped tremendously on the zinc plating line. Not only are the rinses and baths cleaner, but also the blue bright, yellow and olive drab chromates adhere better to the parts. The olive drab is a special color that Metal Seal runs only for Ford. Ford wants everything under the hood of the truck to be silver or black, however this one part cannot be made black, and Ford does not want it silver. The dark olive drab is the best option. "It is a difficult bath to maintain," noted Mr. Diemer. "We only run about 10,000 pieces a year in this color. It is finicky, with a tight pH and concentration range."
All finishing baths are titrated daily using an auto-titrator. Metal Seal also does routine split sampling of the baths, sending samples to Atotech and an independent laboratory for analysis.
Most of the parts at Metal Seal, however, are anodized. Recently, Metal Seal installed its third anodizing line, having outgrown the previous two. The new line, from Abfintech, is random loading and runs nearly nonstop, anodizing between 80,000 and 120,000 pieces a day of mostly 6061 aluminum and its alloys. Both Type II and Type III anodizing are done on the 43-station line where parts can be also be dyed purple, red, gold, brown, green and blue. Parts are dyed for identification purposes only, since all the parts Metal Seal manufactures are functional in nature.
|TABLE I-Chemical Design Specifications|
Solution Temperature, maximum
TDS (total dissolved solids), maximum
TSS (total suspended solids), maximum
TOC (total organic carbons), maximum
Oils and Grease, maximum
The Kinetico system again helped with the anodizing line by not only keeping the rinses clean and cleaning up the baths through turnovers, but the dyes now adhere much better. "Our reject rate has gone from 12-15% down to 1-2%," commented Mr. Diemer. "I attribute it all to the water softener we put in that removes calcium and magnesium. By filtering out the magnesium and calcium, we were able to use sulfuric acid instead of hydrochloric acid in the treatment system. Sulfuric acid is less expensive. Because our baths and rinses are so clean, we save about $2,000 to 4,000 a month in chemical costs."
In addition to reducing reject rates, the water softener, in conjunction with the wastewater treatment system, has helped Metal Seal save even more money by recycling 80% of its water. In addition, it has enabled Metal Seal to meet the discharge limits proposed by the new MP&M rule. With this foundation, Metal Seal hopes to become a small quantity hazardous waste generator. Presently, Metal Seal separates its wastes into two streams, chrome (from the sodium dichromate and red dye) and nonchrome. It loses the 20% of water to the chromium wastes, because that water is not recycled. Treating all of the waste as one stream used to generate 8-10 tons of F006 and F019 filter cake every 90 days, making Metal Seal a large quantity generator. "Now we are down to a one-cubic-yard box, roughly 1,000 lbs every 3-4 weeks. We are right on the edge of becoming a small quantity generator," said Mr. Diemer. "When we add a sludge dryer to take 50% of the moisture out of the filter cake, we should be able to reduce hazardous waste (filter cake) below the 2,200 lb/month cut off."
TABLE II-Waste Disposal Cost Savings
After separating the chrome and nonchrome streams, rinse water from the zinc plating, anodizing and passivating lines flows by gravity to two lift stations. Air diaphragm pumps, controlled by level sensors in the lift stations, pump the rinse water to the water recycling system feed tank. From the feed tank, duplex feed pumps pressurize the water through backwashing media filters, granular activated carbon filtration, cation ion exchange and anion ion exchange. The deionized (DI) water is collected in a storage tank where duplex pumps return it to the rinse tanks. The return pumps also recirculate water through an ultraviolet light to control microbiological growth in the stored water. The system is capable of processing 100 gpm.
The backwashing filtration system has two 36-inch diameter tanks of filter media. The filter media removes solids that may precipitate when acid and caustic rinse water combine in the system feed tank. During normal operation, one tank processes the entire flow while the other is in backwash or standby. Flow to the ion exchange system stops during a filter backwash. A differential pressure switch senses the pressure drop across the operating filter, initiating a filter backwash. The filters can also backwash based on volume of water processed.
After passing through the media filter, the water flows through two 42-inch diameter granular activated carbon filters. The activated carbon removes oils and dissolved organic compounds that could foul the ion exchange resins. The carbon filters backwash automatically based on the water volume processed. During filtration, both carbon tanks process solution. During backwash, the full flow is processed through one tank, and the filtered water is used to backwash the other tank. After the activated carbon filter, bag filters are used to catch any solids that pass through the backwashing filters.
After the water has been processed through all the filtration steps, it goes through duplex cation and duplex anion exchange tanks. The tanks are duplex to provide an uninterrupted flow of DI water. DI water is collected in a 4,000 gal tank, allowing for an uninterrupted supply to the plating lines, even during operations such as filter backwashing, where the flow rate temporarily slows down.
The main control panel for the system contains the PLC that monitors and controls all system functions. The PLC and all system controls are accessed through an operator interface panel. The control panel also contains a modem with a dedicated phone line, so that the PLC can be accessed remotely for monitoring and troubleshooting.
As for the operator, the display at his control is a touch screen that can be used to adjust system set points (password protected) and display and log system alarms. The display shows piping, tanks, vessels and automatic valves. "This entire system is very easy to operate," stated Mr. Diemer. "We simply come in each morning, push a button on the DI unit and open 7 valves, and we are ready for the day." Flow and system status changes are shown by color changes. Actual flow rates, conductivities and other parameters are displayed as well.
All of these changes have helped Metal Seal produce a better product more efficiently. And, not only that, the system has helped the company save on chemical, water and hazardous waste disposal costs. "We were averaging about $7,000 a quarter on water bills before installing the system. Our average bill now is $4,100. That's a 30% savings, even though production has increased. We are spending 25 to 35% less on chemicals and recycling 80% of our water. We have also achieved QS 9000 certification. When we get to small quantity generator status, and we will achieve that, we will be far ahead of the game," stated Mr. Diemer.blog comments powered by Disqus