Self-cleaning filters minimize waste and maximize profits

by Del Williams

Until recently, liquid process filtration tended to be an afterthought in many manufacturing facilities. But this view is rapidly changing due to increased environmental pressures, regulatory requirements and yield targets – not to mention shrinking profits, staffing and capital budgets. As result, many manufacturers are re-evaluating their filtration strategy and turning instead to self-cleaning filters, which promise not only to minimize waste at the source but also maximize productivity and increase profits.

In accordance with the recommendations of the Environmental Protection Agency’s Priority Hierarchy of Waste Management, manufacturers have shifted their focus from end-of-pipe pollution controls to minimizing waste at the source. The reasons for this shift are well documented. Minimizing waste at the source provides a cleaner, safer environment; saves resources and money – in some cases, millions of dollars; and reduces long-term risk and liability. 

Also, by filtering early in the manufacturing process, the cost of filtration decreases significantly since capturing and eliminating undesirable solids is often much more difficult later in the process. Simply put, generating less waste makes good business sense.

The hidden, ongoing costs of disposable media filters
Traditionally, engineers have opted for disposable media filters such as bags or cartridges due to their lower initial cost. While initial cost may be lower for small batch operations, this is seldom true for continuous operations which require a costly, redundant filtration system - including piping, valves, support, and service connections - to maintain production. Moreover, there are significant hidden costs associated with disposable media filters.

To begin with, there’s the ongoing disposable filter purchase price, which typically runs at least $3 per bag or cartridge per day, plus the ongoing cost of waste disposal. For non-hazardous waste, disposal is already $400-$800 per drum, while that of hazardous waste is approaching $1,000 per drum. It’s not unusual for the typical manufacturer to produce about 20 drums per year of filter media for disposal, not including the cost of treating or eliminating any run-off process fluids.

Significant labor costs are also involved with transporting, handling and storing disposable filter media, as well as with replacing it. For example, for just a small 30-gpm cartridge filter with six 10-inch cartridges, the operator must remove 16 separate parts including the cover, compression seals, cartridges and seal plates. The operator must reassemble all 16 parts with proper alignment to ensure good seals. Then someone must haul away the spent filter media.

There’s also a housekeeping cost for cleaning any spillage from disposable media, along with increased emissions, safety risk and liability. Then there’s the potential cost of disposable media rupturing or overflowing (as bags sometimes do), contaminating product or machinery downstream and slowing production.

Finally, add the cost of buying, maintaining, and cleaning workers’ protective clothing for replacing disposable media, as well as the extra time and labor required to fill out MSDS forms and other paperwork required for items hauled to landfills or incinerators.

Self-cleaning filters: A bottom-line boosting alternative
With the hidden, ongoing costs of disposable filter media, the trend in manufacturing is now toward self-cleaning filtration with minimal need for labor. Variations of this, such as disc clean filters (DCF), help manufacturers improve profit, worker safety and waste minimization goals, as operations become more efficient.

Though an upfront capital expense, companies and their plant engineers realize the extent to which self-cleaning filters add to the bottom line. Since a self-cleaning filter system automatically cleans itself while in use, this allows a simple, single piping arrangement, minimal valving and fewer connections, instead of complex, redundant systems. This translates into lower total system cost and reduced waste. A number of other benefits accrue as well, including:

Automated cleaning minimizes disposal waste and labor costs
With cleanable filter media, there are no bags or cartridges to landfill or incinerate. Self-cleaning filter systems clean themselves within seconds. They can be automated to clean themselves according to schedule, or only when necessary.

“Contrary to disposable media which tend to be replaced according to an arbitrary schedule once a shift, day or week, self-cleaning filters can be automated to clean at precisely the right time,” said RPA Process Technologies sales application specialist Roger Weinberg. RPA Process makes industrial filtration systems. Formerly known as Ronningen-Petter, RPA Process has filtration solutions at thousands of installations in more than 10,000 distinct applications.

Self-cleaning filters reduce waste and turn it into profit 
“Dispose of the contaminants - not the filters - to reduce waste and lower disposal costs,” said Weinberg. “Since disposable filter media, especially cartridges, absorb process liquid like a sponge, every time you dispose of a cartridge and its contaminants, you’re also disposing of your process liquid. Cleanable media eliminate this source of waste and can be used over and over to dramatically lower disposal costs.” 

Self-cleaning filters reduce emissions and future liability
With disposable media, the filter is opened every time the media is replaced. This can potentially expose workers and the environment to VOCs (volatile organic compounds) or other toxic emissions. 

Disposable filters also routinely spill some liquid when removed and placed in disposal drums. Quite often, workers simply hose this process liquid to a drain, which adds to potential exposure and waste treatment cost.

Moreover, with disposable filters such as cartridges, contaminants can travel downstream to ruin a product. This can happen, for example, when the knife-edges used to seal cartridges get nicked and permit solids to bypass the media. Contamination can also occur if cartridges aren’t stacked properly in the housing, which is a common problem. In some cases, even the media itself can shed and cause downstream contamination. 

With a self-cleaning filter, however, the filter is opened only for inspection. This drastically reduces emissions and their potential risks.

“Because cleanable media are seldom removed from the housing, seal failure almost never occurs,” said Weinberg. “What’s more, reducing waste with cleanable media not only minimizes current worker safety and landfill liability, but also that from legislation that could require costly clean-up years from now.”

Savings of $70,000 per year
Flint Ink, an international ink supplier, depends on proper filtration to manufacture its ink products for industrial and commercial use. Jonathan Bernblum, while a process engineer at Flint Ink’s Lebanon, Ohio, plant, aimed to streamline cost and quality in producing flexiographic ink for use in food packaging. He found the plant’s existing bag and cartridge filters costly, messy and labor intensive. Workers changed six disposable filters at a time, at least three times a day. When producing particularly viscous inks, production slowed up to 20 percent, as filters sometimes had to be replaced multiple times in a single batch.

“The disposable filters cost hundreds of dollars per day, all year round,” said Bernblum. "At first, they had to be disposed of as a hazardous material in drums, at a cost of about $20,000 per year. Later, with modifications, we were able to dispose of them in dumpsters. Yet 95 percent of our waste stream was the filters themselves, along with good ink trapped inside.

“No one wanted to change out the bag or cartridge filters,” continued Bernblum. “When hot melted varnish occasionally held them in place due to high processing temperatures, they had to be chipped out. It was a nasty, messy process to get them out. Ink spills required cleaning and added to the cost of labor and supplies. Altogether the bag and cartridge filters cost the plant about $70,000 per year in filters, labor, disposal and clean up.”

Moreover, the disposable filters compromised Flint Ink’s commitment to quality. Improper filter installment or any lapse in replacing them could allow small foreign particles into ink products, which could damage client printing presses. Even a small amount of particulate, if present, could cause ink cross contamination and off-spec color as well. This could negatively affect multiple batches. Any such problems had to be troubleshot by managers and line staff, and procedures altered to prevent further incidents.

Bernblum proactively sought out RPA Process, who replaced the bag and cartridge filters with DCF-800 self-cleaning filters. The DCF’s filtering screen has a 150-micron or 230-micron retention size, depending on the quality dictated by the application.

At set intervals, or pre-determined changes in pressure, the DCF cleans the filtering screen then purges the trapped solids, without interrupting production. The DCF filters allow filtration and cleaning to occur simultaneously, which maximizes production.  

“Ninety-five percent of our waste stream is now eliminated with the self-cleaning DCF filters, and production is significantly streamlined,” said Bernblum. “We’re no longer paying for costly disposable filters or high disposal fees. We’re no longer throwing out good salable ink along with filters to be landfilled.

“Since the DCF filters have integrated cleaning loops, no one has to deal with changing out messy filters,” said Bernblum. “Not only is ink quality higher, but the root cause of most quality issues was solved with the switch to DCF filters. Altogether we save about $70,000 per year in filters, labor, disposal and clean-up. We achieved about seven-month ROI, including higher, more reliable and flexible production capacity.”

Four-month ROI on self-cleaning filters
PPG Architectural Finishes, a latex paint and stain manufacturer in Louisville, Ky., knew its filling operation was overly complicated, noisy, and required far too much operator attention. More importantly, PPG experienced an unacceptable percentage of product loss in the filtering process. 

An air operated diaphragm pump at the base of a blend tank pumped product onto a large, open, vibrating screen. Product exiting the vibrating screen fed into an accumulating vessel, where another pump transferred product through a polishing filter into a rotary drum-filling machine. With the two pumps, vibrating screen and open-air vessel, the system was complex, noisy and wasteful.

To stay competitive in the tough, low-margin paint industry, Doug Story, plant engineer at the Louisville site, aimed to streamline the company’s filling operation. His goals: to produce as much finished product as possible, using the least wasteful, most environmentally friendly methods available.

In consultation with RPA Process, PPG replaced their vibrating screen, accumulating vessel and diaphragm pump with a DCF-800, mechanically-cleaned filter. Removing the vibrating screen eliminated the need for the accumulating vessel, associated piping and controls, as well as the second diaphragm and its compressed air components and controls.

The DCF filter virtually eliminated operator involvement in the operation, and removing the vibrating screen and second diaphragm pump reduced noise levels. The DCF filter purges residual paint and debris into the plant recycling system, where the solids are separated and the paint is reused.

According to Story, there has been a significant reduction in product waste. 

“Post-installation cost for the first year was under $10,” said Story. “Payback was achieved in four months, and this analysis does not include the savings generated in utility costs for the vibrating screen, its maintenance or additional operator time. The DCF filter contributed to our paint and stain production efficiency, and exceeded the objectives set at the beginning of the project. It also provides our workers with a quieter, more environmentally friendly workplace.”

For more information on self-cleaning filter technology, write to RPA Process Technologies, Inc. at 9151 Shaver Road, Portage, Mich. , USA; call 866-867-2893 toll free; fax ; or visit www.rpaprocess.com. Del Williams is a technical writer based in Torrance, Calif.

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