Polymer gears won't gall or swell

Minneapolis--Engineering plastics continue to replace metals in critical applications. Pumps provide a good example.

When Northern Pump looked for a plastic to replace 300 series stainless steel for the gears in its Dura series pumps, it needed a material that would resist chemicals, corrosion, and wear, but also have low moisture absorption characteristics.

"Galling presented a problem with 300 series stainless steel gears in the absence of lubrication," explains Bob Adamek, Northern Pump general manager. "The gears essentially destroy themselves."

The solution: a switch to PEEK(TM) (polyetheretherketone) polymer supplied by VICTREX USA Inc. (West Chester, PA).

"Using PEEK polymer for the gears means the pumps can handle fluids with a much wider pH range than traditional materials," Adamek reports. "Since we customize our pumps to the chemical industry's exact requirements, using this material gives us a much broader range of problem-solving capabilities.

Also, "clearances in our gear pumps are so close that, if a gear absorbs moisture and starts to swell, it can seize up," Adamek explains. "PEEK's low moisture absorption eliminated that concern."

Even design flexibility played a role in choosing PEEK. "Our helical gears have an angle, as opposed to spur gears, which are straight cut. This is not an easy shape to make out of a composite. In fact, its pretty revolutionary. We are pleased with the results of our PEEK gear design. Best of all, our customers like what they see."

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