SPECIAL TOPIC : SEVERE SERVICE APPLICATIONS
14-Day Back-up Ring Testing
0.14 0.12 0.1 0.08 0.06 0.04 0.02
0 Extrusion height H ( inch )
Extrusion vs . Time @ 35,000 psi / 550 ° F
PEEK 30 % Carbon Filled PEEK Arlon 3000XT
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1 |
3 |
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Test Duration ( Hr .) |
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Test results , coupons tested at 550 ° F ( 288 ° C ), 35 ksi ( 2,413 bar ), e-gap 0.020 ”
Arlon 3000XT ® shows improved extrusion resistence vs . virgin and filled versions of PEEK
Tests fixture schematic , e-gap 0.020 ” 4
• The extrusion performance of Arlon 3000XT ® is superior to filled versions of PEEK
• Unfilled cross-linked 3000XT is much more more creep resistant than competitive 30 % fiber filled “ standard ” PEEK grades
PEEK ( left ) shows 10 times greater extrusion than Arlon ® 3000XT ( right )
Creep Resistance : Greene Tweed Custom Coupon Test 5
Creep Resistance : Greene Tweed Custom Coupon Test 5
• Creep / stress relaxation at very long timescales approaches the properties seen in a short-term DMA tests at higher temperatures
• Improving the Tg and increasing the rubbery plateau should improve creep resistance and reduce stress relaxation ( seen empirically in products in service under load for long periods of time )
Lifetime Prediction : Time Temperature Equivalency 6
Lifetime Prediction : Time Temperature Equivalency 6
benefits of a material which can be used under more severe service conditions that once required metal seals and valve seats .
When operating temperatures exceed the working temperatures of crosslinked PEEK , 650 ° F ( 343 ° C ), operators are firmly in the range where metal seals and valve seats must be used . Even at the temperature range above the capabilities of polymers , there are notable advances in materials and coatings that can extend the life of your valve under extreme conditions . TCC ( Tungsten Carbide Coating ) or CCC ( Chromium Carbide Coating ) seats can operate at very high temperatures and pressures and enhance wear resistance .
Final Words
In summary , polymer valve seats , backup rings , seals , bushings and other components offer many performance benefits over metal components , but the polymer components have traditionally been limited to temperatures below 550 ° F ( 288 ° C ). New advances in crosslinked PEEK enable polymers to be used in valve seats up to 650 ° F ( 343 ° C ) with improved performance and a longer service life , while having reduced risk of chemical attack or
ABOUT THE AUTHOR brittle failure from impact . Even beyond 650 ° F ( 343 ° C ), the crosslinked PEEK goes through a phase transition to a stable rubbery plateau to at least 824 ° F ( 440 ° C ), where this crosslinked PEEK will perform like an ultra-high temperature elastomer , a feature which can be very useful for certain applications or high temperature excursions . Using the latest materials solutions can greatly improve safety , reliability , capability limits and service life for severe service valves .
REFERENCES
1 . Scheirs , J . ( 2000 ). Compositional and Failure Analysis of Polymers : A Practical Approach . Wiley .
2 . Campbell , F . J . ( 1983 ). Temperature Dependence of Hydrolysis of Polyimide Wire Insulation . NRL Memorandum Report , 5158 . 3 . Greene Tweed unpublished data . ( 2005-2013 ). 4 . Ren , J . ( 2012 ). Testing and Challenge of High-Performance Thermoplastics for Oil and Gas High Pressure / High-Temperature Sealing Applications . ANTEC .
5 . Bekisli , B . ( 2016 ). New Frontiers for High Performance Thermoplastics in Oilfield Applications . Oil & Gas Polymer Engineering Texas . Houston .
6 . Menczel , J . D ., & Prime , R . B . ( 2018 ). Thermal Analysis of Polymers : Fundamentals and Applications . Wiley .
Brian Callahan is a Thermoplastics Product Manager at Greene Tweed with over 18 years of polymer experience , including 11 years in high performance polymers , designing and testing polymer materials and products using them in a wide range of high-performance sealing applications with roles in product design , application engineering , materials engineering and management , as well as sales and product management .
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