MetoKote Corp., Lima, Ohio, is one such partner company, providing a diverse range of coating technology solutions, such as electro coating, powder coating, and liquid paint. At one of its frame plants, MetoKote applies a zinc phosphate coating to steel car and truck frames as a pretreatment to the electro coating process. The zinc phosphate, applied in an 18,000-gal. immersion dip tank, acts as a critical corrosion retardant.
The Problem: Sludge Build-Up
According to Bill Holloway, general manager, Northern Region, MetoKote, one of the challenges facing the company is keeping the pre-treatment tanks clean. “A natural chemical reaction between the zinc phosphate and steel creates a sludge by-product that rapidly builds in the tank,” said Holloway. “If the tanks aren’t kept clean, the sludge will cling to the frames.”
In trying to solve the problem, MetoKote developed its own proprietary filtering system to reduce the amount of sludge and waste in the dip tanks. Designing an effective filtration system for this process was particularly challenging. Phosphatizing tanks are typically very large, normally with a flat bottom, making it difficult to concentrate the solids into an area of the tank where they can effectively feed to a filtration unit.
MetroKote's filtering system used two gravity filter beds and continuous rolls of 60-in. indexing filter paper that constantly screened the contents of the tank to keep it as clean and sludge-free as possible.
While the system was effective, MetoKote knew they needed to improve the process. In addition to the cost associated with buying and disposing of the paper media, the zinc phosphate was continually exposed to the air during the filtering process – causing it to lose heat. Because the process did not filter fine particulates, impurities left behind created sludge build-up. Scheduled tank cleanings needed to be completed to remove the solid waste, and the labor to remove the waste combined with disposal fees were costly.
A Durable, Cost-Effective Solution
After researching several solutions, MetoKote decided to invest in CentraSep Technologies' centrifugal filtration system, and participated in the trial program that CentraSep offered.
The trial was conducted on the 18,000-gal. zinc phosphate tank used for coating frames. A CentraSep unit was installed on a side-stream kidney loop basis – running completely independent of the line. Even when the tank was not in production, CentraSep would continue processing the bath.
The CentraSep unit now keeps the filtering process completely contained – instead of exposing the tank contents to the atmosphere while filtering – and it does so in a small footprint. The enclosed filtering process provides the ability to maintain a consistent temperature, optimizing chemistry efficiency and saving on chemical, water and energy costs to heat the tank.
“With the closed system provided by CentraSep, and the lower water content of the CentraSep sludge, we’ve greatly reduced make-up water usage and scale build up; therefore the boiler isn’t working so hard to maintain bath temperature,” said Todd Gibbish, facility maintenance manager. “While we can’t put an exact number on the energy savings because the boiler feeds other parts of the facility, we know the savings are significant.”
He continued, “Consistency is key to production and quality. If the bath temperature is not maintained at a steady state, we have to increase the concentration of chemical or make other adjustments to allow the bath temperature to come back into range. With the CentraSep unit, our ability to maintain heat is greatly improved. With the bath temperature more consistent, we have reduced the need to monitor and adjust chemical make-up.”
“Plus, with a cleaner phosphate tank, there’s been a reduction in the amount of solids carried over into our rinse bath,” says Gibbish.The CentraSep unit has a maximum gravitational force of 2,012 G’s with removal capabilities that exceed traditional media filtration technologies like gravity bed filters. The system is simple, but effective and reliable. It is comprised of a single-motor, vertical self-discharging centrifuge, as opposed to vertical self-discharging centrifuges that use two motors and complex drive mechanisms to function.
The CentraSep unit runs unattended and discharges its accumulated solids automatically. No filter media or labor is required. Powered by an intuitive PLC program and an ABB drive using solution-specific firmware, the unit electronically generates the torque required to automatically discharge the collected waste during the scrape cycle.Little Training; Minimum Maintenance
“The training and set-up for the unit was simple,” said Gibbish. “We really only had to learn some basic on/off procedures. There’s just not a lot to it from a training standpoint.”A programmer reviews the CentraSep's PLC program |
Preventative maintenance is easy as well. “We follow some simple procedures that they showed us, but quite frankly there is just not much we need to do,” continues Gibbish. “Other than emptying the hopper and occasionally cleaning the strainer that protects the pump inlet, we’ve really done nothing since installation.”
Once every six months, there is one preventative maintenance item suggested by CentraSep – a clutch lubrication that takes less than fifteen minutes – and CentraSep trains its customers at the onset of the relationship.
The Payback
“The main reason we got the unit was to take more sludge out of the tank than the filter beds allowed us to,” said Dave Haefner, plant manager. “We also liked that the sludge that it removed was drier because of its centrifugal force, returning more liquid back to the tank – instead of holding it in the sludge like our old system. It costs more to dispose of the wet sludge since you pay for its removal by weight. And environmentally speaking, the drier it is, the safer it is.”
Haefner continued, “With the CentraSep unit, the dried sludge is deposited into a hopper that you’re able to dump every day, so you’re only paying for the true disposal as it leaves.”
“In the past, to clean the tank, it was a six-to-eight-hour job and we normally brought in an outside company to help,” added Haefner. “These are $6,000 to $8,000 affairs – just for disposal costs. So, if we avoid the need to clean the tank becaus