Back-up rings, also known as support rings or anti-extrusion rings, are used to support O-rings in high-pressure applications. The support ring is placed directly next to the O-ring and helps prevent the elastomer from being forced into the gap between the sealing surfaces. This counteracts gap extrusion and can prevent damage or leakage of the O-ring.
Support rings are widely used in hydraulic and pneumatic systems and are available in different materials and designs. Common materials include PTFE, PE, HPU and NBR. Depending on the application, a closed, split, spiral or concave design can be used. View the available range of support rings and back-up rings.
Back-up rings are support rings used in combination with an O-ring. The ring is placed next to the O-ring in the sealing groove and forms a barrier between the O-ring and the sealing gap. This provides the O-ring with additional support as the pressure in the system increases.
Especially at high pressure, with large sealing gaps or fluctuating pressure loads, an O-ring without sufficient support can deform. Part of the rubber can then be forced into the gap. This can be counteracted by using a suitable support ring.
The terms support ring, back-up ring and anti-extrusion ring are used for the same type of sealing component. The term anti-extrusion ring refers directly to its main function: protecting the O-ring against extrusion under pressure.
Gap extrusion occurs when an O-ring is partially forced under pressure into the space between two sealing surfaces. If the load is high enough, this can damage the rubber. The O-ring may develop deformation, cuts or damaged edges. Eventually, this can result in leakage.
The support ring is positioned between the O-ring and the sealing gap. The ring therefore provides mechanical support that prevents the softer O-ring material from being easily forced into the gap. This provides better protection for an O-ring at higher pressures and under heavy loads.
A support ring is placed directly next to the O-ring in the sealing groove. The correct position depends on the direction in which pressure is applied. The support ring must prevent the O-ring from being extruded on the side of the sealing gap.
In an application where pressure comes from one direction, one back-up ring can be used depending on the construction. It is positioned so that the O-ring is supported on the side where extrusion may occur.
With alternating or bidirectional pressure, support rings can be installed on both sides of the O-ring. This supports the O-ring in both pressure directions. This arrangement is used, for example, in double-acting hydraulic cylinders.
Back-up rings are available in different materials. Which material is suitable depends on factors including pressure, temperature, medium, movement and the sealing construction. Common materials include PTFE, PE, HPU and NBR.
PTFE support rings combine high chemical resistance with good temperature and friction properties. PTFE is therefore widely used in demanding sealing applications. The rings can be supplied in different designs, including closed, split and spiral versions. View the available PTFE support rings.
PE support rings are used for general industrial sealing applications. PE is dimensionally stable, wear-resistant and resistant to various chemicals. The material can be a practical solution for applications with lower to medium pressure loads. View the available PE support rings.
HPU support rings offer high wear resistance and good mechanical properties. They are therefore used in hydraulic systems where high pressure and mechanical loads occur. View the available HPU support rings.
NBR concave support rings have a hollow inner side that follows the shape of the O-ring. This supports the O-ring and helps distribute the load. NBR is widely used in contact with oils and greases. View the available NBR concave support rings.
In addition to the material, the design of the support ring is also important. PTFE back-up rings in particular are available in different shapes. The choice depends on factors including the groove construction, installation, pressure and application.
A closed support ring consists of one continuous ring without an opening. This construction provides uniform support around the O-ring. With a closed groove, installation can be more difficult depending on the material and construction.
A split support ring has an opening, often with an angled cut. This makes it easier to install the ring in certain grooves. This can be particularly beneficial during maintenance or in difficult-to-access constructions.
A spiral support ring consists of an overlapping construction. This design can adapt to the groove and is used for specific sealing applications.
A concave support ring has a hollow-shaped side that is installed facing the O-ring. This allows the support ring to follow the round profile of the O-ring. This design is used, among others, for NBR back-up rings.
Back-up rings are used when an O-ring requires additional support against pressure and extrusion. They are widely used in hydraulic and pneumatic systems, as well as in pumps, valves, cylinders and other industrial machinery.
High pressures can occur in hydraulic systems. A support ring can support the O-ring and prevent it from being forced into an available sealing gap.
Support rings can also be used in pneumatic systems when the combination of pressure, gap size and O-ring material requires additional protection against extrusion.
When selecting the correct back-up ring, several factors must be considered. These include the O-ring dimensions, available groove, maximum pressure, temperature, medium and pressure direction.
The most suitable material and type of support ring can then be determined. PTFE can be an interesting choice when chemical or thermal resistance is important, while HPU offers good mechanical and wear properties. Concave NBR can be suitable for oil-containing hydraulic applications.
View the complete range of support rings to compare different materials, designs and dimensions.
A back-up ring is a support ring placed next to an O-ring to protect it against deformation and gap extrusion under high pressure.
There is no functional difference in this context. Support ring, back-up ring and anti-extrusion ring are different terms for a ring that supports an O-ring against extrusion.
A support ring may be required when an O-ring is exposed to high pressure and there is a risk that the elastomer will be forced into the sealing gap. Gap size, material and temperature also play a role.
A support ring is placed directly next to the O-ring in the groove. The exact position depends on the pressure direction. With alternating pressure, support rings can be used on both sides.
Common materials for support rings include PTFE, PE, HPU and NBR. Which material is suitable depends on factors including pressure, temperature, medium and application.
Yes. In applications with alternating pressure directions, support rings can be placed on both sides of the O-ring so that the O-ring is supported in both directions.
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