NON-METALLIC SOLUTIONS FOR SEALS, GASKETS, AND VALVE SEATS
For centuries, ever since the first systems to transport water, composite (non-metallic) materials have been used as seals and gaskets with the same basic requirements as generically similar applications today: to maintain pressure and prevent leakage.
Modern sealing applications have a much more demanding set of performance requirements in an ever-increasing range of challenging environments. Higher temperatures, higher pressures, more aggressive chemical environments, and an emphasis on safety require highly specific solutions to today’s seal applications.
From small diameter seals in scientific equipment to downhole insulator seats, to large diameter flow valve seats in water and oil transport systems, to turbocompressor labyrinth seals with diameters measured in feet – today’s modern composite material availabilities offer performance and cost-in-use advantages to both the OEM and end-user.
WS Hampshire offers a wide range of materials for these seal applications, in both standard and customized materials. While UHMW-PE, nylon, and acetal are still used for lower-end applications, today’s designers look to high-performance thermoplastics (HPM’s) for most new systems. These include: (brand names included for reference only)
- PTFE (polytetrafluorethylene, or “Teflon®”) based materials, characterized by outstanding chemical resistance and extremely low coefficient of friction (COF) – available with a wide range of reinforcement types (including combinations) and load levels to enhance specific performance properties
- PPS (polyphenylene sulfide or “Ryton®”) – a “poor man’s PEEK”, this base chemistry is known for outstanding chemical resistance and is available in unfilled, glass filled and bearing grade versions at a lower cost than PEEK
- PEEK (“VICTREX®”) – the “Swiss Army Knife” of HPM’s”, the base chemistry is characterized by extreme toughness and hydrolysis resistance to ~320֯ F, and can be reinforced with glass or carbon fiber, and also a bearing grade package to improve stiffness, COF and/or wear properties
- PAI (polyamide-imide, or “Torlon®”) – the highest performing melt-processable plastic, it is characterized by excellent temperature resistance, from cryogenic to 500֯ F, high strength at temperature, plus excellent dimensional stability, stiffness and creep resistance; it is available in a wide range of reinforced and wear-enhanced version. As with all “iridized” materials (including PI & PBI), PAI is susceptible to hydrolysis attack in prolonged exposure to steam or super-heated water
- PI (polyimide, or “Vespel®”) – this material is chosen where the high-temperature requirements exceed those of PAI (can withstand to 570֯ F), is equally good as PAI in cryogenic service, and is characterized by excellent mechanical strength and toughness, low outgassing and inherently good wear resistance; as with most HPM’s, reinforced and enhanced versions offer property customization; as with PAI, prolonged exposure to high-temperature moisture is not recommended
- PBI (polybenzimidazole, or “Celazole®”) – essentially a thermoplastic ceramic, PBI is characterized by the highest mechanical properties of any plastic material above 400֯ F, the highest heat deflection temperature @ 800֯ F, continuous service temperature of 750֯ F and short-term excursions to 1000֯ F; it also has the lowest coefficient of thermal expansion and highest compressive strength of any unfilled plastic; PBI is extremely expensive to make and fabricate, and is chosen when all other material options do not meet these most severe requirements
The team at WS Hampshire can assist you with material selection – let us know your needs!