You can extend the service life of ISO-KF seals in high temperature applications by switching from generic fluoroelastomers (FKM) such as Viton, to perfluoroelastomers (FFKM), and by ensuring the seal is properly sized.

ISO-KF (or ISO-QF or ISO-NW) type flange seals provide an economical, convenient and simplified means of constructing vacuum systems. However, despite the efficiency offered by these flanges, you may face premature seal failure and unscheduled equipment downtime when standard AS-568A o-rings are specified for locations which will be exposed to >/= 150 degrees C and/or harsh process effluent, particularly in heated forelines and exhaust lines.

NW Series perfluoroelastomer seals (o-rings) from DuPont Performance Elastomers increase seal life and reduce downtime over standard ISO-KF seals in high-temperature applications because:

  1. The various NW size cross-sections are optimized to provide the best sealing performance with the lowest amount of mechanical stress, thus avoiding premature breakdown.
  2. Certain Kalrez FFKM materials can operate continuously up to 325C, as opposed to the practical limit of 150C (short term max 200C) for standard FKM materials.
  3. Kalrez FFKM material significantly out-performs FKM material, providing strong resistance to both chemical and physical plasma attack.
Standard AS-568A O-Ring Recommended NW Series O-Ring
KF/NW-10 2-312 KNW-10
KF/NW-16 2-314 KNW-16
KF/NW-25 2-320 KNW-25
KF/NW-40 2-326 KNW-40
KF/NW-50 2-330 KNW-50
ISO/LF-63 2-336 KNW-63
ISO/LF-80 2-340 KNW-80
ISO/LF-100 2-346 KNW-100
ISO/LF-160 2-361 KNW-160
ISO/LF-200 2-371 KNW-200

Application Note: Kalrez NW Series 0-Rings
Video on Kalrez perfluoroelastomer technology


IES Technical Sales is a manufacturer’s representative and distribution firm which focuses on technical applications involving vacuum, thin film/plasma, temperature, and flow. For more information, contact us.