KF Centring Rings & FKM O-Ring Seals

ISO-KF centring rings and FKM O-ring seals provide reliable vacuum-tight connections between ISO-KF (NW/QF) flanges. Available in different configurations, flange sizes and ring materials, they ensure correct positioning and sealing between mating KF flanges.

The metal centring rings support and position the elastomer O-ring, while the KF clamp compresses the seal to establish a vacuum-tight connection.

Available Configurations

Outer Centring Ring with Inner Support Ring

This configuration consists of an external centring ring and an additional internal support ring, with an FKM O-ring positioned between them.

The outer ring provides alignment around the flange connection, while the inner ring supports the elastomer seal. Different material combinations are available for the outer and inner rings.

Inner Centring Ring

The standard internal centring ring carries an FKM O-ring around its outer circumference. It ensures correct positioning of the seal between the KF flanges and supports the O-ring against inward displacement.

Available in stainless steel or aluminium, depending on the selected flange size.

Centring Ring with Mesh

This configuration combines an internal centring ring with an integrated stainless steel mesh screen and an FKM O-ring.

The mesh helps prevent particles and foreign objects from entering vacuum pumps and other connected vacuum components.

Standard mesh specification: 30 mesh.

Replacement O-Ring

Replacement FKM O-rings are available separately without a metal centring ring.

They can be used to replace worn or damaged seals in compatible ISO-KF centring ring assemblies.

Select None under Ring Material (Outer-Inner) when ordering an O-ring without a metal ring.

Ring Materials

The available ring materials depend on the selected configuration and flange size.

For outer centring rings with inner support rings, the material designation indicates the outer ring material first, followed by the inner ring material.

Available combinations include aluminium with stainless steel 1.4301 (AISI 304) or stainless steel 1.4404 (AISI 316L).

Single centring rings are available in aluminium, stainless steel 1.4301 (AISI 304) or stainless steel 1.4404 (AISI 316L), depending on the configuration.

The material option None applies to replacement O-rings supplied without a metal centring ring.

O-Ring Material

All configurations are supplied with FKM (Viton®) O-ring seals.

FKM offers good resistance to many chemicals, low gas permeability and reliable sealing performance for rough and high vacuum applications.

Available Flange Sizes

Available for ISO-KF flange sizes DN10 KF, DN16 KF, DN25 KF, DN40 KF and DN50 KF, depending on the selected configuration.

Operating Temperature

FKM (Viton®) O-rings are typically suitable for operating temperatures from −20 °C to +150 °C, with intermittent exposure up to +200 °C, depending on the specific compound and operating conditions.

Applications

ISO-KF centring rings and FKM O-ring seals are suitable for vacuum pumping lines, vacuum chambers, scientific instruments, research laboratories and industrial vacuum systems.

Select the appropriate Type, Flange size and Ring Material (Outer-Inner) to configure the required sealing assembly or replacement O-ring.