Metal Wear Component Replacement
In this article we are going to look at another fiber-reinforced polymer material that is being used to replace metal wear components in pump applications: PEEK + carbon fibers.
For further investigation into polymer wear components check out these Advanced EMC Technologies Blog articles:
- Dummy’s Guide to Composite Materials for Wear Components
- Ultimate Cheat Sheet for Polymer Wear Components in Pumps
- Polymer Bushings Taking a Beating: Two Important Concepts behind the Wear and Tear
PEEK (polyetheretherketone) combined with carbon fiber is a popular choice as a fiber-reinforced polymer (FRP) composite for use in wear components. On its own, PEEK is known for
- outstanding chemical resistance,
- low friction,
- very little moisture absorption,
- has high strength,
- with low flammability and smoke emission.
It is dimensionally stable, and its resistance to the degrading effects of long-term radiation exposure. It usually outperforms other plastics when it comes to long term exposure to hot water and steam, too.
Carbon fibers are known for being heat resistant, in fact, Thomas Edison used carbon fibers in his early light-bulb filament designs for this very reason, indicating that they first came into use during the 1800s. It wasn’t until the 1950s that scientists and engineers discovered how to develop high-tensile strength carbon fibers, and their potential use as reinforcement in composite materials began to be exploited. As far as their applicability to wear components, carbon fibers are chemically inert, and provide significant strength and stiffness while adding minimal weight.
When combined, PEEK and carbon fibers offer a combination of low friction and high impact strength. Because PEEK is considerably softer than metal, the PEEK carbon fiber FRP wear component will wear away should contact occur, rather than causing galling or seizing. If dry run should occur, the primary components will remain undamaged, but the composite wear component might begin to melt if sufficient heat is generated by friction. However, its purpose is to serve as a sacrificial component.
FRP and API Standards
As of 2003, PEEK-based carbon fiber composites were included in the API (American Petroleum Institute) standards as an acceptable choice for replacing metal wear components in appropriate applications. According to the API 610 9th edition, when filled with chopped carbon fibers PEEK composites have a limiting pressure differential of 20 bar (300 psi) and a temperature range from -20°F to 275°F, but are mainly limited in application to stationary parts. Continuous carbon fiber wound reinforced PEEK has the same minimum temperature but its maximum service temperature is 450°F with a 35 bar (500 psi) limiting pressure differential. However, if supported properly the pressure differential can go up to 140 bar (or 2000 psi).
Polymers as Wear Component Material
The use of polymers as wear component materials is still evolving, with many options available to today’s engineer. Carbon-reinforced PEEK is one of many options, and offers low friction, excellent impact strength, and successfully prevents galling and seizing. It a good service temperature range, and very good limiting pressure differentials, and works extremely well in hostile environments including those involving exposure to radiation, and constant exposure to steam or hot water.
Check out the PEEK Plastic versus Metal slide-deck download from Advanced EMC Technologies.