But doing so usually involves replacing and disposing dirty filters. A new device from SMC Corp. of America, Indianapolis (www.smcusa.com), the FN1, employs a filter element constructed of a series of grooved filter plates and wave washers stacked one after the other and compressed together by a pneumatic cylinder. When the elements clog, a differential-pressure switch signals for backwash operation. This closes the filter's inlet valve and the pneumatic cylinder releases pressure, letting the filter stack expand. A reservoir valve opens and clean, pressurized fluid backwashes dirt and debris from the filter elements. A ball valve at the bottom of the unit opens to drain dirty fluid to a dust-removal filter tank. The operation can be synchronized with machine operation.

Flow capacity is either 400 or 800 liter/min, and a range of seals permits use with water, coolants, and petroleum and alkali solutions.