O-ring seal

elastomerrubbersilicone rubber

Product overview
A FEP/PFA encapsulated O-ring is a static sealing element consisting of an elastomer core ring that is seamlessly encased in a FEP/PFA jacket. FEP/PFA is a perfluorinated polymer that provides excellent chemical resistance similar to PTFE. The elastic pressing force is comparable to that of a conventional elastomer O-ring, but expansion and compression are more limited due to the encapsulation.

Fields of application

• Axial-static sealing
• Radial-static sealing

Main use
A simple sealant with excellent chemical resistance, used where enhanced chemical compatibility, physiological harmlessness and sterilizability are required.

Materials
Elastomer core materials (e.g. FKM, VMQ) with FEP or PFA encapsulation.

Advantages

• High resistance against aggressive media
• High performance in critical applications
• Wide operating temperature range
• Cost-effective
• Physiologically harmless and sterilizable
• Suitable for use in food, chemical and petrochemical industries
• FDA-compliancy
• Low coefficient of friction
• Low permeation

Design information
For installation the same groove designs as for standard elastomer O-rings generally apply. FEP/PFA encapsulated O-rings have limited stretching and compression compared to elastomer O-rings. Recommended maximum groove filling values for static sealing are lower than for elastomer O-rings (typical static sealing groove filling: 12–22%). Split grooves are recommended for installation.

Installation instructions

• Contact surfaces of the installation area must be free of scratches, dents and similar damage.
• Edges and insertion inclinations must be deburred as per guidelines.
• Heating the O-ring in hot, compatible media before assembly can facilitate deformation for installation; install immediately after heating.
• The O-ring must not be buckled or overstretched during assembly.

Notes
FEP/PFA O-rings should not be used in applications with abrasive contact surfaces or abrasive media, which can damage the encapsulation. Maximum values for temperature, speed and pressure are not simultaneously applicable and vary depending on material and media.

Characteristics / technical specifications

• Materials: Elastomer core (e.g. FKM, VMQ) with FEP/PFA encapsulation
• Inside diameter (d1): approx. 6 mm to 5000 mm
• Cross section (d2): approx. 1.5 mm to 20 mm
• Typical groove degree of filling for static sealing: 12 – 22%
• Installation preconditions: square groove, low pressing forces into housing, limited O-ring stretch; split grooves recommended
• Variants and technical values (examples):
  
  • Variant (FKM): Pressure up to 25 MPa; Temperature range approx. -25°C to +200°C (material dependent); Speed: not specified
  • Variant (VMQ): Pressure up to 25 MPa; Temperature range approx. -60°C to +200°C (material dependent); Speed: not specified
• Sealing effect: axial or radial compression of cross section; elastomer core provides pre-pressing, encapsulation reduces overall elasticity