Self-Cleaning Filtration Basics

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SELF-CLEANING FILTRATION BASICS

FILTRATION

Filtration has long been recognized for its ability to improve product quality, increase throughput and protect downstream equipment. Due to the predominant use of disposable media filters, however, it was also seen as a necessary contributor to a company’s environmental impact. Today, that view is changing as manufacturers are tasked with the strategic corporate mandate to reduce the amount of waste they produce and dispose. As a result, many manufacturers are re-evaluating their filtration strategy and turning to self-cleaning filters, which promise not only to minimize waste at the source but also maximize productivity and increase profits.

Traditionally, plant 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 to maintain production – including piping, valves, support and service connections.

Moreover, there are hidden costs associated with disposable media filters. When users purchase disposable media filters, they often fail to account for the true costs of doing so. There is the initial 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 $400-$800 per drum, while that of hazardous waste is approaching $1,000 per drum.

There are also labor costs involved with transporting, handling and storing disposable filter media, as well as replacement. 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 and 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 and the potential cost of disposable media rupturing or overflowing (as bags sometimes do), contaminating product or machinery downstream and slowing production.

Other costs include 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.

The trend in manufacturing is now toward self-cleaning filtration with minimal need for labor. Variations of this, such as disc clean filters (DCF), are helping manufacturers to improve profit, worker safety and waste-minimization goals as operations become more efficient.

Though an upfront capital expense, many companies and their plant engineers are now realizing the extent that self-cleaning filters add to the bottom line. To start with, since a self-cleaning filter system automatically cleans itself while in use, this allows a simple, single piping arrangement, minimal valving and fewer connections. 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 haul off to the landfill or incinerator. Self-cleaning filter systems clean themselves within seconds of starting a cleaning cycle. They can be automated to clean themselves according to schedule, or only when necessary.

Self-cleaning is controlled by the pressure differential between inlet and outlet headers as contaminants collect on the filter screen. The screens automatically clean themselves when the pressure reaches a predetermined level. This reduces both labor and waste in the filtration process at the source.

SELF-CLEANING FILTERS NOT ONLY REDUCE "WASTE" BUT ALSO CAN TURN IT INTO PROFIT

Dispose of the contaminants, not the filters, to reduce waste and lower disposal costs. 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.

For example, cleaning liquid can often be recycled for additional cleaning, and at times the contaminant itself can be recycled into the manufacturing process as a raw material.

SELF-CLEANING FILTERS NOT ONLY REDUCE "WASTE" BUT ALSO CAN TURN IT INTO PROFIT

Since 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. Positive elastomeric-to-metal seals can virtually eliminate off-spec product due to solids bypassing the filter media. Because cleanable media are seldom removed from the housing, seal failure almost never occurs. 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.

EXAMPLES OF SELF-CLEANING FILTER APPLICATIONS

Process Water
Cooling Water
Chemicals
Pharmaceuticals and cosmetics
Fuels and petroleum chemicals
Coatings paint and ink
RO pre-filtration
Resins and adhesives
Metalworking fluids
Process fluids
Coolants and oils
Wastewater
Pulp and paper

SELF-CLEANING FILTER OPTIONS

DCF- Cleaning Disc is moved up and down inside the filter by way of an electric motor and screw type shaft, or with an externally mounted cylinder. The drawback with the DCF is there can be contamination introduced into the filter through the shaft seals.
MCF- Magnetically coupled filter features an innovative design driven by a magnetically coupled cleaning disc. This design eliminates the need for lid through holes and seals, thus eliminating contamination.
Tubular Backwashing Filters. Used for tight retentions and high flow. Modular, so your system can grow with your application demands. These have a wide range of operating pressures.

Note: “Tech Tips” offered by Flodraulic Group or its companies are presented as a convenience to those who may wish to use them and are not presented as an alternative to formal fluid power education or professional system design assistance.

Experts in fluid power, electrical and mechanical technologies.

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