Rawac Plating Co., Springfield, Ohio, bought a used plating machine and gave it new life. With the help of its next door neighbor, Corrotec, Inc., Rawac was able to resurrect the giant machine and make it a first class zinc plating line.
It all started when Dave Stratton of Corrotec called Dave Fail of Rawac and asked if he would be interested in a used plating line. Considering that several competing businesses in the Springfield area were leaving or closing, Mr. Fail and his boss, Art Gianakopoulos, decided it would be a good investment. However, simply moving the line into the building was not the answer. Rawac had to build an addition to its existing facility to accommodate the new line.
This allowed Corrotec to assist in the setup and layout of the new building, as well as make recommendations about the floor, dikes, secondary containment and waste treatment facilities.
The line became a marriage of old and new. The used line was coupled with new programming, heaters, rectifiers, washer, dryer and conveyor line. A prewash system was added also to the line to help remove the variety of oils and soils that come in on parts.
"Each manufacturer uses a different oil, it seems," noted Mr. Fail. "We needed something that would work with all types of soils." Job shops are being confronted with more and different types of soils. There are several theories as to why parts are arriving at job shops with more oils and/or soils on them. One theory is that the demise of vapor degreasing has prompted manufacturers to send dirty parts to the plater for cleanup. Another theory is that manufacturers are changing the oils they use due to environmental regulations. Since there is an array of machining fluids, lubricants and oils, the plater has to find a way to clean all of them off the parts.
The prewash system at Rawac is a single-stage process in which parts are impinged with a low concentration (four oz/gal) alkaline cleaner for three min. A gas-fired immersion burner heats the cleaner. Two vertical pumps, producing 150 gph at 60 tdh, pump the solution through risers to nozzles, where parts are sprayed at 300 gpm. This removes 90 pct of all soils before the parts ever reach the cleaners on the zinc plating line. It also keeps the zinc plating baths clean, allowing one to see clear to the bottom of the tank.
The prewash system was a solution to problems Rawac had experienced on its other plating lines. The oils from incoming parts were killing the immersion cleaners and, subsequently, additional waste treatment and greater chemical use resulted. There was also added downtime for dumping the cleaner tanks and recharging them with fresh cleaner.
The prewash is off-line yet set up adjacent to the plating line. After the loader removes two racks from the plating line it loads two racks from the washer onto the line.
The original plating system was designed to plate different size parts than those plated at Rawac. Corrotec rebuilt the load bars to accommodate new parts and heavier racks. All the system controls were converted into programmable logic controls. The system runs from a PLC-basic control system with operator interface. A similar return-type machine was already running at the Rawac facility and was used as the foundation for the new system.
The plating line has 44 stations and handles 88 racks at a time. Cycling is just over one min per cycle, producing two racks of parts or 120 racks/hr of plated parts. The plating cycle is listed in Table I.
All rinses, except those between the soak and electrocleaner, are countercurrent. In the cleaning tanks, cleaners are pumped from the bottom of the tank and through a ripple pipe to skim off the oils. The recovered oils are sent to a reclaimer.
The last rinse in each countercurrent rinse sequence has a flow restriction of five gpm. The total rinse water discharged from the plating line is less than 25 gpm.
Water from the line is collected in a large sump and from there is transferred to a sump in the main building. The main building houses an expanded 150 gpm waste treatment system.
When Rawac decided to install the zinc plating line, it knew it would have to also consider a larger waste treatment system. First, Rawac purchased a larger clarifier from Lanco Environmental Products. The treatment reactors also were enlarged. The reactor system consists of a series of tanks that elevate the pH to approximately 10, doses it with chemicals and polymers, sends it to the surge tank and then to the clarifier. From the clarifier, wastewater goes through a sludge thickener followed by a filter press for dewatering. Clarified liquid goes to a weir tank and is then discharged to the local POTW. The limit on zinc in Springfield is three ppm.
The ventilation system is a 18,500 cfm Duall System scrubber. The hoods and ductwork were rebuilt, along with a new remote recirculating tank and piping.
The marriage of used equipment with new was an accomplishment. But Rawac felt it had to make it work in order to stay productive. "There are fewer platers out there today, and with the increase in the demand for productivity and absolute quality, we had to find a way to deliver," stated Mr. Fail. And Rawac did!
|TABLE I -- Rack Zinc Line Cycle|
|1.Spray Wash||3 min cycle at 140°F using Enprep 150|
|2.Soak Clean||3 min cycle at 160°F with Enprep 126|
|3.Cold Water Rinse|
|4.Electroclean||3 min cycle at 160°F with 10 Amps/sq ft using Enprep 271|
|5.Cold Water Rinse|
|6.Cold Water Rinse|
|7.Acid Pickle||5 min cycle at 50 pct concentration of Hydrochloric Acid|
|8.Cold Water Rinse|
|9.Cold Water Rinse|
|10.Plating Cycle||19 stations at 10 Amps/sq ft using Enthobright 941|
|11.Cold Water Rinse|
|12.Cold Water Rinse|
|13.Pre-Dip||0.10 pct of Hydrochloric Acid|
|14.Bright Dip||Permapass 9903|
|15.Cold Water Rinse|
|16.Cold Water Rinse|
|17.Warm Water Rinse|
|18.Air Knife||For 30 sec|
|19.Forced Air Dry||At 110°F for 10 min|