5 Mar 2002
PEEK™ polymer significantly improves seal performance for centrifugal compressors
Greene Tweed, a world leader in high performance seal technology, has designed an innovative labyrinth seal using a carbon fibre reinforced PEEK™ composite. This tailor-made grade, based on VICTREX® PEEK™ polyaryletherketone, has been specifically developed to meet the demands of compressor manufacturers for improved performance, reduced maintenance costs and increased productivity.
Traditionally, aluminium has been the material of choice as it provided high quality seals that did not abrade the compressor shaft. However, when contact occurs between an aluminium seal and a shaft made of carbon steel, particularly at high speeds, the aluminium can become permanently damaged. This significantly increases the clearance between the seal and the shaft and thereby compromises the efficiency of the compressor.
Greene Tweed tested a variety of engineering thermoplastics polymers including the PEEK™ composite. Some exhibited hygroscopic behaviour, especially at elevated temperatures, which caused the material to swell or distort and become brittle, while others were not able to withstand the temperatures typically encountered in centrifugal compressors.
Compared to other thermoplastics, PEEK™ polymer offers outstanding high temperature performance. With a melting temperature of 340°C, and a UL Continuous Use Temperature of 260°C, the composite can be used at much higher temperatures than even aluminium which starts softening at temperatures in excess of 200°C. Furthermore, PEEK™ polymer is characterised by excellent hydrolysis resistance, outstanding friction and wear properties, and resistance to a wide range of chemicals, even at elevated temperatures. These include, for example, ammonia and alkalines that are corrosive to aluminium.
In radial wear tests which compared PEEK™ polymer seals with those made of aluminium, Greene Tweed found that PEEK™ polymer seals showed significantly less wear than the aluminium seals. Furthermore, a visual examination of the shafts showed that the aluminium labyrinth seal caused extensive grooving and galling, whereas the PEEK™ polymer seals caused only light surface scratching.
A major feature of the PEEK™ polymer composite is its ductility. This allows the teeth of the seal to flex if it comes in contact with the shaft. This important property allowed Greene Tweed to decrease the clearance between the seal and the shaft, thereby enhancing the efficiency of the compressor and the overall productivity. According to the manufacturer, using labyrinth seals made with the PEEK™ composite can deliver efficiency gains of up to 1% per stage in a compressor. It is not uncommon for a whole compressor to have an efficiency gain of 5% - 6%, which can bring considerable operating cost savings.
Reader enquiries
Helen SwarbrickVictrex plc
Victrex Technology Centre
Hillhouse International
Thornton Cleveleys
Lancashire FY5 4QD
United Kingdom
Tel +44 1253 897700
Fax +44 1253 897701
United Kingdom
Notes for editors
Victrex plc, which has its sales, technical and production headquarters at Thornton Cleveleys in Lancashire, UK, had a turnover of more than £72m in the last financial year. The company exports 98 percent of its VICTREX® PEEK™ polymer output to OEMs in the automotive, industrial, medical, food and electronics market sectors in Europe, North America and Asia Pacific.
Information on products, technical support services and sales and distribution contacts worldwide, can be accessed through the company’s web site: www.victrex.com
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The PEEK™ Trademark
For many years Victrex plc has been using the PEEK™ trademark to refer to its brand of Polyaryletherketone. Victrex plc is the sole manufacturer and supplier of the PEEK™ brand polymer world-wide. PEEK™ is a trademark of Victrex plc.
Related images
PEEK™ composite labyrinth seals from Green Tweed improve centrifugal compressor performance and efficiency.
