How to Spec a Filter Cart

A customer recently asked me to take a look at a quote he had received from a local filter distributor on a set of filter carts. As I scanned the fax for information, it became obvious that the quote was just that ... a series of numbers and letters and a price for the equipment that was represented by those numbers and letters. There was absolutely no information on the page about the filter carts’ performance or features other than the option of purchasing one or two filters.

It was apparent that one of two things happened.

It is common for a customer to call the local supplier and inquire about the supplier’s filter carts. The supplier will usually provide only three details – pump displacement in gallons per minute (GPM), price and delivery date. There is usually no mention of filter performance, viscosity limitations or possible options. Most suppliers have standard five GPM, 10 GPM and 15 GPM filter carts stocked and ready to go.

The second possible scenario is that the customer called the supplier and discussed only one or two details that may have included price range and pump displacement in GPM. Either way, there was a lack of understanding on both sides.

Every filter cart should be compatible with the lubricant and the intended application. When considering the addition of a filter cart to your contamination control program, take into account the following:

• Filter type, availability and replacement cost. You must be able to get filters when you need them from any supplier you choose. Make sure there are at least two or three suppliers for the filter housing (or head) installed on your cart. Spin-on filters do a great job and are cheap, interchangeable and available from all of the major filter companies.
  
  Cartridge filters can usually hold more dirt relative to cost, but many are harder to cross-reference to other suppliers. Make sure the filters you specify on your filter cart are available in a range of media types and beta ratings. This will enable you to change your filter efficiency as your contamination control program changes.

• Minimum and maximum viscosity range. Make sure your filter cart is designed to meet the viscosity of the lubricant you intend to decontaminate. All filter cart pumps have a minimum and maximum viscosity range, so make sure you specify which lubricant you will be using at the expected temperature extremes.

• Pump flow rate. The maximum pump flow rate should be only 10 percent of the total sump volume. A 10-gallon reservoir requires no more than one GPM for decontamination. Insufficient flow will result in long decontamination periods.

• Size and weight. Ideally, the unit should be able to reach each system that requires periodic decontamination. If the overall size and weight of the filter cart is too cumbersome, it may not reach the equipment that is difficult to access.

Other items to consider are oil-resistant tires, air (pneumatic) or electric power, power cord length, a filter bypass valve, suction and return hose length, before and after filter sample valves, a suction strainer, hose end configuration, clogging indicators or differential pressure gauges, vacuum shut-off, seal compatibility, timer, on-line particle counter, color and price.

Now, the mystery behind your filter cart is in your hands. Determine exactly what you need and provide your supplier with the details. The leading suppliers will be able to design the filter cart to meet your exact needs, giving you the most for your investment.