PTFE Back-up Rings

M Barnwell Services’ PTFE Back-up Rings, also referred to as Anti-Extrusion Rings, play a crucial role in bolstering O Rings and X-Rings/Quad-Rings across static and dynamic applications. They effectively counteract seal extrusion caused by high system pressure, a common issue when seals lack support. Typically, Back-up Rings become necessary when system pressures exceed 105 BAR (1500 PSI) or when extrusion gaps are significant.

PTFE Back-up rings serve a protective role rather than sealing. They’re crafted from durable materials to resist extrusion, typically featuring a rectangular shape. Installed alongside elastomeric seals, like O Rings, in static settings, they prevent the extrusion of the elastomeric element under pressure.

Advantages

High-pressure O Ring applications.
Low-hardness O Ring materials utilised.
Compensation for radial sealing gaps.
Versatile for internal and external sealing, accommodating reciprocating and rotating movements.
Effective in managing large temperature variations.
Suitable for both static and dynamic applications.

PTFE Back-up Rings Types

Types of Back-up rings include uncut varieties like the BM and BCM seal types and cut versions like the BG and BCC seal types. Additionally, there are spiral Back-up rings like the SP seal type, each with specific features for different installation needs:

Uncut

BM Seal Type
External sealing (Bore) Internal sealing (Rod)
– Material: PTFE.
– Rectangular cross-section.
– Standard: AS568, MS27595, JISB2407.
– Static and dynamic applications.
– Reciprocating and rotating movements are possible.
BCM Seal Type
External sealing (Bore) Internal sealing (Rod)
– Material: NBR,FKM,PTFE.
– Concave cross-section.
– Standard: AS568.
– The large contact surface protects the O-Ring against deformation in cases of high pulsating pressure.
– The dimensional stability of the O-Ring improves the sealing force and increases the service life.
– Preferably for static use.
– Reciprocating movements are possible.

Cut

BG Seal Type
External sealing (Bore) Internal sealing (Rod)
– Material: PTFE.
– Rectangular cross-section.
– Cut angle of 30° or 45° or 20°.
– Static and dynamic use.
– Reciprocating and rotating movements are possible
– Preferred for installations in a closed groove where uncut Back-up Rings are not suitable.
BCC Seal Type
External sealing (Bore) Internal sealing (Rod)
– Material: PTFE.
– Concave cross-section.
– Cut angle of 30° or 45°.
– The large contact surface protects the O-Ring against deformation in cases of high pulsating pressure.
– The dimensional stability of the O-Ring improves the sealing force and increases the service life.
– Preferably for static use.
– Reciprocating movements are possible.
– Preferred for installations in a closed groove where uncut Back-up Rings are not suitable.

Spiral

SP Seal Type
External sealing (Bore) Internal sealing (Rod)
– Material: PTFE.
– Rectangular cross-section.
– Cut angle of 30° or 45°.
– Consists of standard two spiral windings which are cut at the ends at an angle.
– Static and dynamic use.
– For reciprocating movements only.
– Preferred for installations in a closed groove where uncut Back-up rings are not suitable.
– Compensation of large temperature changes and tolerances without difficulties by a screw-like elongation and contraction.
– Easy Installation in closed grooves for external sealing applications.
– The dimensions are different compared to standard Back-up Rings.

PTFE Back-up Rings Materials

Materials for Back-up rings vary based on application requirements. While standard Back-up rings are made of virgin PTFE, filled PTFE or thermoplastic materials are used for higher loads or sealing against high pressures. Injection-molded options are available for mass production.

Applications and Technical Data

These rings find application across various industries such as:

Technical data specifies their operating parameters including speed, pressure, and temperature range. They can handle speeds up to 2 m/s, pressures ranging from 15 to 250 MPa, and operate within a temperature range of -200°C to +260°C.

Use the following links to find detailed information on our range of Back-up Rings:

For further details on our offerings, access our catalogue, explore the Seal Maker Page, or contact one of our team members. E & OE.

Sizes

Manufactured as standard to suit O-Ring sizes but can be manufactured to almost any size.

Profiles

Solid, Contoured, Spiral, Single Turn and Split.

Materials

PTFE, Nitrile (NBR), Viton® (FKM/FPM), Polyurethane (AU), Leather, Hytrel®, Rubberised-Fabric & many more.

Associated Products

O-Rings, X-Rings / Quad Rings.