Back-Up Rings
Back-up rings, also known as anti-extrusion rings, are used alongside O-rings and other seals to prevent seal extrusion in high-pressure hydraulic and pneumatic systems. M Seals supplies PTFE, NBR, FKM, polyurethane and custom-manufactured back-up rings in standard and bespoke sizes for hydraulic, pneumatic and industrial sealing applications.
What are Back-up Rings?
Back-up rings are installed on one or both sides of the primary seal to provide additional support and prevent extrusion under pressure. By filling the clearance gap between mating components, they help maintain sealing performance and extend seal life.
Commonly manufactured from PTFE, NBR, FKM, polyurethane and other engineering materials, back-up rings are used in hydraulic cylinders, pneumatic systems, pumps, valves and industrial machinery where demanding operating conditions place increased stress on sealing systems.
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How Back-Up Rings Prevent Seal Extrusion
In high-pressure hydraulic and pneumatic systems, the primary seal can be forced into the clearance gap between components, causing damage and leakage. This is known as seal extrusion.
Back-up rings are installed alongside the primary seal to provide additional support and fill the clearance gap. By preventing the seal material from being pushed into the gap, they help maintain sealing performance, extend seal life and improve system reliability.
Back-up rings are commonly used in demanding applications where high pressures, temperature fluctuations or larger clearances increase the risk of seal extrusion.
Types of Back-Up Rings
Back-up rings are available in several designs to suit different installation requirements, operating pressures and application environments. The most common types are solid, split and spiral back-up rings.
Solid Back-Up Rings
Solid back-up rings are manufactured as a continuous ring and provide excellent support for the primary seal. They are commonly used in high-pressure applications where maximum extrusion resistance is required and are typically installed during equipment assembly. Solid back-up rings are a reliable choice for hydraulic cylinders, valves and other demanding sealing applications.
Split Back-Up Rings
Split back-up rings feature a cut or split in the ring, allowing them to be installed without fully dismantling the equipment. This makes them ideal for maintenance and retrofit applications where access is limited. Split back-up rings provide effective extrusion protection while simplifying installation and reducing downtime.
Spiral Back-Up Rings
Spiral back-up rings are formed from a continuous spiral of material, allowing them to expand during installation and return to their original shape once fitted. They offer excellent flexibility, easy installation and reliable extrusion resistance, making them particularly suitable for high-pressure hydraulic and pneumatic systems where assembly convenience and sealing performance are equally important.
Back-Up Ring Materials
PTFE Back-Up Rings
PTFE, or polytetrafluoroethylene, is a popular material for back-up rings due to its exceptional chemical resistance and low coefficient of friction. Back-up rings made from PTFE are ideal for use in applications where aggressive chemicals or high temperatures are present, as they can withstand a wide range of corrosive and abrasive fluids. PTFE back-up rings also offer excellent resistance to extrusion and wear, which helps to prolong the life of the primary seal and prevent leaks in your hydraulic or pneumatic system.
NBR Back-Up Rings
Nitrile rubber (NBR) back-up rings provide excellent resistance to oils, greases and hydraulic fluids. They are a cost-effective option for many industrial and hydraulic applications where reliable extrusion resistance is required.
FKM Back-Up Rings
FKM (fluorocarbon) back-up rings offer excellent resistance to high temperatures, fuels, oils and aggressive chemicals. They are commonly used in demanding hydraulic, pneumatic and industrial sealing applications where long-term reliability is required.
Polyurethane Back-Up Rings
Back-up rings made from polyurethane offer excellent resistance to wear, abrasion and high pressures. They are also known for their high load-bearing capacity and low compression set, which makes them ideal for use in heavy-duty applications.
Silicone Back-Up Rings
Silicone back-up rings are ideal for use in high-temperature applications, as they can withstand temperatures of up to 200°C. They are also highly resistant to ozone and UV light, which makes them suitable for use in outdoor environments.
Applications
Back-up rings, often referred to as anti-extrusion rings, are widely used in hydraulic and pneumatic systems where high pressures, temperature variations or large clearance gaps increase the risk of seal extrusion. Typical applications include:
- Hydraulic cylinders
- Hydraulic pumps
- Pneumatic cylinders
- Valves
- Industrial machinery
- Mobile hydraulics
- Process equipment
- Oil and gas systems
- Construction equipment
They are frequently specified wherever system reliability, seal life and leakage prevention are critical.
Standard and Custom Back-Up Rings
M Seals supplies both standard and custom-manufactured back-up rings to suit a wide range of hydraulic and pneumatic sealing applications. Available in a variety of materials, including PTFE, NBR, FKM and polyurethane, our back-up rings are designed to provide reliable extrusion resistance in demanding operating environments.
Whether you require a standard size for a routine maintenance replacement or a custom solution for a specialised application, our sealing experts can help identify the most suitable design and material. We offer fast quotations, technical support and bespoke manufacturing capabilities to meet specific pressure, temperature and media compatibility requirements.
With access to a broad range of standard and custom sizes, M Seals can provide back-up rings for everything from general industrial equipment to highly demanding hydraulic and pneumatic systems.
Order Back-up Rings
M Seals supplies standard and custom-manufactured back-up rings and anti-extrusion rings in a wide range of materials and sizes. Our team provides fast quotations, expert material selection support and international delivery to customers worldwide.
Back-up Ring FAQs
What is a back-up ring?
A back-up ring, or anti-extrusion ring, is a rigid support ring used alongside an O-ring or seal to prevent extrusion under pressure.
When should a back-up ring be used?
Back-up rings are typically recommended when system pressures exceed the extrusion resistance of the primary seal.
Can back-up rings be used with O-rings?
Yes. Back-up rings are commonly installed alongside O-rings to prevent extrusion and extend seal life in high-pressure sealing systems.
What materials are best for back-up rings?
PTFE is often preferred for high-pressure and chemically aggressive applications, while NBR, FKM and polyurethane may be selected depending on operating temperature, media compatibility and performance requirements.
What's the difference between a split and solid back-up ring?
Split back-up rings can be installed without dismantling equipment, whereas solid rings generally require assembly during installation.