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PEEK (polyetheretherketone) is a popular engineering polymer that is used in everything from high-performance bearings to labyrinth seals.

In this blog post, we are going to look at how and why PEEK is being used in reciprocating compressors, starting with piston rings.

PEEK_Valve_Plate.jpgSource

Piston Rings

The main purpose of a piston ring is to restrict the flow of gas between the cylinder bore and the piston, and its sealing effect is activated when there is cylinder pressure present. Failed piston rings are one of the common causes of reciprocating compressor shutdown, which is why it is vital that they be made from a reliable, dimensionally stable, and chemically neutral material like PEEK.  In addition, PEEK provides very good abrasion resistance and a hard surface that is quite wear resistant but won’t damage any metal surfaces it comes into contact with.


Failed piston rings are one of the common causes of reciprocating compressor shutdown.



Valves

Another major cause of failure in reciprocating compressors is the compressor valves.  PEEK is being used more and more for these parts because of its corrosion resistance, resistance to abrasion, excellent wear properties, and low-density (much, much lighter than its metal counterparts).  The impact strength of PEEK along with its fatigue resistance are two additional reasons that more and more engineers are turning to PEEK for reciprocating compressor valves.

Rider Bands

The piston ring is free floating because of the radial clearance between the ring and the piston.  The rider band has a radial thickness that is greater than the piston ring groove depth so that it supports the piston while it rides on the cylinder bore to prevent metal-to-metal contact. This part, like piston rings, must be reliable with low friction, self-lubrication, dimensional stability, and functionality at high temperatures. Since it prevents metal-to-metal contact, it must have a hard enough surface to resist abrasion while at the same time not damaging the metal surfaces it contacts.  It must also be quite wear resistant.

Labyrinth Seals

PEEK labyrinth seals are an effective sealing solutions for a variety of applications, including reciprocating compressors. Its thermal properties are one of the primary reasons behind its popularity for labyrinth seal: it has a high continuous use temperature and is dimensionally stable even at high temperatures.  Other key features include its low friction, light weight, strength, and chemical resistivity.

Conclusion

PEEK has excellent strength properties, outstanding chemical resistance, low friction, good impact strength, self-lubricating, favorable wear properties, and a maximum operating temperature around 480°F. This explains, in part, its popularity for valves, piston rings, rider bands, and labyrinth seals found in reciprocating compressors.
 

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