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Zinc Phosphate Case Study – MetoKote Corporation

CentraSep filtration system improves process and reduces operating costs for MetoKote

Innovation has brought the automobile assembly line a long way since the days of Henry Ford. While the basic concept remains the same, these days, automobile manufacturers have further streamlined and automated all of the processes involved including working with various partner companies to complete critical steps in the car-building process. However, even with all the advancements made, manufacturers and their partner companies alike are continually looking for ways to make processes more efficient and cost-effective.

MetoKote Corporation, headquartered in Lima, Ohio, is one such partner company, providing a diverse range of coating technology solutions, such as electro coating, powder coating, liquid paint and others. 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 is applied in an 18,000-gallon immersion dip tank, and acts as a critical corrosion retardant.

The Problem: Lost Production and High Maintenance Costs

According to Bill Holloway, general manager, Northern Region, MetoKote, one of the challenges the company faces is keeping the pretreatment tanks clean. A natural chemical reaction between the zinc phosphate and steel creates a sludge bi-product that rapidly builds in the tank, says Holloway. If the tanks aren’t kept clean, the sludge will cling to the frames.

MetoKote developed its own proprietary filtering system to reduce the amount of sludge and waste in its dip tank. 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.

Dave Haefner, plant manager describes the system: Essentially, it was two gravity filter bed systems consisting of continuous rolls of 60 in. indexing filter paper constantly screening the contents of the tank to keep it as clean and as sludge-free as possible.

While the system was effective, MetoKote is always looking for ways to improve its processes. 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. The process doesn’t filter the fine particulate, so 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

At a trade show in Indianapolis, Indiana, MetoKote was introduced to CentraSep Centrifuges, and its CentraSep centrifugal filtration system. The chance to become more efficient and reduce operating costs was appealing. Initially, we were reluctant because it seemed almost too good to be true, says Holloway. But we looked at other companies and no one else offered what they did so we decided to take them up on their trial program at one of our plants.

The trial was conducted on the 18,000-gallon zinc phosphate tank used for coating frames. The 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, says 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 continues, 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.

CentraSep specializes in centrifugally separating solids from liquids in industrial applications. The CentraSep unit has a maximum gravitational force of 2,012 G’s with removal capabilities that far exceed traditional media filtration technologies like gravity bed filters. According to Jeff Beattey, Executive Vice President of Product Development at CentraSep Centrifuges, Every application and customer need is different. From the beginning, we assess those needs and clearly define CentraSep’s filtration capabilities to ensure proper application of our centrifuge technology.

The patented CentraSep unit is simple. It is comprised of a single motor vertical self-discharging centrifuge all other vertical self-discharging centrifuges require two motors and complex drive mechanisms to function. The patented combination of a single motor with a single proprietary clutch design keeps the unit simple and provides significant reliability and efficiency advantages to the end user compared to other centrifuges and other filtration technologies.

The CentraSep unit runs unattended and discharges its accumulated solids automatically. It requires no filter media or labor. 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. This combination provides reliability and equipment protection not found with two-motor-style centrifuges. Other vertical self-discharging centrifuges use gear motors to generate torque, which can lead to component failure and broken parts in an overload condition.

Keeping Maintenance to a Minimum

What began as a trial has turned into a two-year partnership. The CentraSep system comes with a standard one-year parts and labor warranty. CentraSep offers the option to renew that warranty annually through its warranty extension program.

The training and set-up for the unit was simple, says Gibbish. So we really only had to learn some basic on/off procedures. There’s just not a lot to it from a training standpoint.

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 that’s suggested by CentraSep for the unit a clutch lubrication that takes less than fifteen minutes and CentraSep trains its customers at the onset of the relationship

If we’re running normally at the plant, the line is running about 16 to 17 hours per day, five days a week, adds Haefner. We’ve had no maintenance issues of any kind with CentraSep.

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, says Haefner. 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 continues, 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, adds Haefner. These are $6,000 to $8,000 affairs just for disposal costs. So, if we avoid the need to clean the tank because of the extra filtration the CentraSep unit offers, that’s a $6,000 or $8,000 savings every time.

Another area of savings is the filter paper. Obviously, the filter paper on our old system was not reusable, so once that filter paper was used, you’d have to throw that out and start over, says Gibbish. So we also have a labor reduction and a purchase reduction of handling the filter media paper because the CentraSep is not using any kind of media. On the old system, changing filters was a regular occurrence. During our busiest times, we needed to change them every week.

In quantifying a total payback or cost savings to date, Holloway says, We were anticipating a year-and-a-half to two-year payback if everything went according to plan. And we’re right on track with what we thought which is very good.

MetoKote has been so pleased with CentraSep that the company is looking across its organization for other applications where it could apply this solution.

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