Back-up rings PTFE

What Are PTFE Back-up Rings?

PTFE back-up rings, also known as anti-extrusion rings, are designed to be used alongside O-rings in high-pressure systems. Depending on the pressure direction, the ring is placed on one or both sides of the seal. This creates a barrier between the O-ring and the sealing gap, preventing the O-ring from being forced into the gap under pressure.

This helps to prevent extrusion, a common form of O-ring failure in high-pressure environments, and reduces the risk of leakage. Especially in applications with fluctuating pressure, back-up rings are essential. Their shape and positioning provide critical support to the O-ring, contributing to a stable and reliable sealing system.

Advantages of PTFE as a Material

PTFE (Polytetrafluoroethylene), also known under the brand name Teflon®, is a high-performance plastic that excels in key sealing characteristics. It offers outstanding chemical resistance, making it unaffected by acids, solvents, and fuels.

PTFE has a broad temperature range from -260°C to +200°C, maintaining its shape and function even in extreme conditions. Its low coefficient of friction prevents sticking or seizing, especially beneficial in dynamic applications. Though PTFE is not elastic like elastomers, it is highly wear-resistant and dimensionally stable, both critical features for preventing extrusion under extreme conditions.

Moreover, PTFE is FDA and EC1935/2004 compliant, making it a safe and versatile choice for industrial applications where reliability and safety are essential.

Applications of PTFE Back-up Rings

PTFE back-up rings are used in systems exposed to high pressure, extreme temperatures, and aggressive media that could otherwise damage the O-ring. Common applications include hydraulic and pneumatic systems, where constant motion and pressure require added protection. They are also widely used in heavy industries, including cylinders, valves, and pumps.

Types of PTFE Back-up Rings

PTFE support rings are available in three types: Solid (Closed), Split, and Spiral. Each variant is engineered to provide optimal extrusion resistance under specific conditions. The best choice depends on installation requirements, pressure levels, temperature, and dynamic movement. With these three standard types, there's always a PTFE back-up ring suitable for your needs.

Solid (Closed) Back-up Rings

Solid PTFE back-up rings feature a continuous, unbroken structure that offers the highest protection against gap extrusion. These are especially suited for applications where high pressure and temperature are combined, such as rods, pistons, and flat seals. Their rigid design helps maintain position and makes them ideal for static sealing. A disadvantage is the difficulty of installing them in closed grooves, especially in small sizes, yet they are preferred when maximum reliability is critical.

Split Back-up Rings

Split PTFE back-up rings have a precise 45° scarf-cut, allowing for easy installation without dismantling the system. This makes them perfect for retrofit applications or systems with limited access. They flexibly adapt to the sealing gap and are suitable for dynamic high-pressure environments. While there is a slight risk of extrusion or micro-leaks where the O-ring contacts the cut, split rings remain the most commonly used type due to their easy installation.

Spiral Back-up Rings

Spiral PTFE back-up rings are made from ultra-thin, overlapping coils that provide even pressure distribution and extra support in extreme conditions. They are flexible and resistant to chemical, thermal, and mechanical stress. However, spiral rings are used less frequently in modern designs because the ends can be fragile during installation and they offer lower extrusion resistance. This is due to their two-part coil structure, each half the thickness of a solid or split ring. They're also more expensive and less readily available.

Which PTFE Back-up Ring is Right for Your Application?

Choosing the correct PTFE back-up ring depends on factors like pressure, temperature, gap size, and dynamic load. Solid back-up rings offer the best protection against extrusion and are ideal for static applications but may be difficult to install in confined grooves. In such cases, split rings are a better option due to their easy installation, particularly in maintenance or retrofit scenarios. That’s why split rings are the most commonly used type. Spiral rings offer good pressure distribution but are less suitable for new designs due to lower resistance and handling concerns.

Always consider system pressure, temperature range, extrusion gap, and dynamic forces to determine the best PTFE back-up ring for your application. This prevents leakage and extends the service life of your O-ring.

Order PTFE Back-up Rings at O-ring-stocks.eu

At O-ring-stocks.eu, you'll find a complete range of PTFE back-up rings in three variants: Solid, Split, and Spiral. Whether you need maximum extrusion protection, easy maintenance, or a solution for dynamic sealing, we offer the right PTFE back-up ring for your specific requirements. With our large stock and fast delivery, your PTFE rings will be at your door in no time.

Need help choosing the correct type or size? Our specialists are happy to assist you with technical advice and help you select the best sealing solution.