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Polymer seal extends compressor valve life

A Victrex product story
Edited by the Engineeringtalk editorial team Jun 6, 2003

Cook Manley of Stafford, USA, has developed the on-site-reparable Moppet compressor valve, featuring a Victrex Peek polymer seal ring.

Cook Manley of Stafford, USA, has developed the on-site-reparable Moppet compressor valve, featuring a Victrex Peek polymer seal ring.

With its inherent long-term dimensional stability, flexural properties, fatigue and wear resistance over a wide range of temperatures and pressures, the polymer contributes to the valve's proven success in petrochemical and natural gas installations.

Compressors used in these demanding industries have to operate in a variety of environments, ranging from vacuum refrigeration to very high temperature, high pressure refinery processes.

Unlike nylon, which can only withstand temperatures up to 140-145C depending upon the type of pressure being applied, Victrex Peek polymer delivers high temperature performance up to 250C over a wide pressure range.

It is essential that the valves maintain dimensional stability while in the end-use customer's inventory.

When compared to materials such as nylon, which is inherently hygroscopic, Peek polymer has extremely low moisture absorption and is therefore very dimensionally stable.

Victrex Peek polymer's excellent fatigue and flexural properties are also important to this application.

"When a compressor is running, it can become contaminated with dirt and liquids", explains Mr Parks, Plant Manger at Cook Manley, "Unless the seal ring is flexible, it can snap under these conditions.

Whilst there are many materials that are flexible in nature, very few have the fatigue strength of Victrex Peek polymer.

This is an essential property, as a seal ring has to bend and flex during millions of cycles per year, running at typically 300-330rev/min.

Some compressors can operate up to 2000rev/min".

Cook Manley has successfully used Victrex Peek polymer for many years for its radius-disc valves.

The Moppet is in fact a series of individual radius-disc valves encapsulated in modular cartridges.

The cartridges are interchangeable from valve to valve and from compressor to compressor, thereby minimizing end-user inventories.

The Moppet valves significantly reduce both maintenance costs and compressor downtime.

Unlike traditional valves, which are typically sent back to shore for repair, these patented valves can be easily repaired on-site, with no specialist tools or training required.

However, with its combination of high mechanical strength and long-term fatigue resistance, Victrex Peek polymer contributes to the valve's extended service lifetime.

According to Bill Peterson, Area Supervisor for the Hanover Company, a large compressor rental company: "At one station, we were replacing OEM plate valves every week.

We installed a set of Moppet valves over a year ago and they are still going strong".

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