Materials of Construction: Considerations When Purchasing a Filter Press or Aftermarket Parts
M.W. Watermark wants to make a difference. We are passionate about the world’s water. We are innovative, focused on customer service and always try to exceed expectations. We are an environmentally conscious company with people who are energized, encouraged and inspired to make a difference in the water business, and as a result, make a positive difference to our planet by helping to keep our shared, finite water supply clean and usable for generations to come. We build amazing water and wastewater treatment equipment. Together, we can make a difference.
As part of M.W. Watermark’s efforts to make a difference, we would like to present some thought starters to you – on the multiple factors to consider when planning the types of materials of construction that are needed in a filter press to adequately handle the job at hand.
The first question to always ask is, “What is the slurry?”
The temperature, pressure, pH, chemical compatibility and abrasiveness of the slurry can each play an important role when selecting filter press components.
For example, materials that perform well at room temperature do not always hold up at a higher temperature, such as 200 degrees Fahrenheit. An abrasive slurry such as occurs during lime dewatering can be hard on filter cloths, and cause premature wear. However, at the same time it is critical to choose the right fabric for the optimum formation of a filter cake.
Polypropylene is the standard for filter cloths and performs ideally in most applications. This material can withstand higher temperatures, does not easily succumb to blinding (clogging of the weave) and has a smooth surface which aids in cake removal. However, it’s important to know the make-up of the slurry before assuming that polypropylene is the material of choice. For example, if the slurry is bleach, polypropylene will not be compatible, and polyester filter cloth materials must be used.
Piping can also be affected by the type of slurry being dewatered. Potential piping materials include: PVC (standard), Polypropylene, CPVC, carbon steel, and stainless steel. A combination of EPDM (Ethylene Propylene Diene Monomer, or M-class) rubber and stainless steel is the least expensive for piping and gasketing, but depending on the chemicals in the slurry, a nylon coating may also be required. Depending on the pH of the chemical, Viton® (also referred to as FKM) may also be needed instead of EPDM.
Slurries with a high temperature can also cause pressure issues, causing standard threaded connections to no longer be adequate. Or, if the application is in the food industry, threaded connections cannot be used. In this case, a different piping material may need to be used, such as stainless versus PVC, or the piping itself may need to be flanged.
The selection of gasketing and seals can also be affected by the composition of the slurry. EPDM is standard material for gasketing, however, a slurry such as biodiesel will cause EPDM to become gummy. In this case, Viton® (FKM) becomes the ideal choice of material.
By now we can see that the chemical make-up of the slurry has an effect on many of the filter press parts and components. Even the sludge pump is affected by the nature of the slurry it is pushing through. Potential pump materials can include: Polypropylene, carbon steel or stainless steel.
One final, yet very important filter press component to consider is the hardware and fasteners. Hardware must be carefully selected to be compatible with the wetted material moving through the press.
For example, a steel company needed M.W. Watermark’s assistance with slurry that was dissolving both stainless steel and nylon. It dissolved multiple sets of hardware. Watermark’s Service and Engineering teams found that the only hardware and piping combination that was chemically compatible was titanium – and the head plate had to be re-worked to include a caulking groove for the head cloth.
Another solution that M.W. Watermark offers for enhanced resistance to corrosion and wear is the EnduroLiner™ coating. EnduroLiner™ is a polyurea/polyurethane spray-on coating that exhibits excellent adhesion for seamless protection from wear and abrasion. EnduroLiner™ also provides excellent UV light, chemical, and moisture resistance necessary for demanding applications.
Hopefully, this blog posting gives you a general sense of materials of construction factors to start thinking about when considering the purchase of a filter press, and later, any aftermarket replacement parts you may need.
Because each of the filter presses we build are customized based on our customer’s specific application, we recommend contacting the M.W. Watermark Sales and Service team to discuss the best components for your situation.
Contact the M.W. Watermark Sales and Service team of experts today to discuss your specific application.
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