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The importance of backup rings to O rings

Backup rings are ultimately used to help stop o ring migration, and they achieve this in both static and dynamic fluid power applications as the pressure cycles occur, preventing the extrusion of an o ring in the gap.  Ultimately a backup ring is a rigid ring that...

Gasket manufacturing process explained

Specialist Sealing Products have been providing high-quality gaskets to customers throughout the UK for many years. We pride ourselves in the range of gaskets we have available, suitable for a variety of applications across a range of industries.  Rubber gaskets are...

Designing seals for the food industry

There’s a number of factors to take into consideration when designing seals for the food industry. That’s because seals used within this sector need to work exceptionally hard in all food processing environments where hygiene and health and safety are of the utmost...

Storing your gaskets!

A strange headline for a gasket article, we know.  However, it’s an important area and one, which in this sector is often overlooked.  When we think about most products or items in and around our homes and business, we will recognise that most come with manufacturing...

Flange Gasket materials – What you need to know

Getting the most out of flange gasket materials and ensuring the performance of the gasket is not affected when you come to use it, means several things must be taken into consideration.  For example, factors such as their design, how they’re manufactured, installed,...

Spiral Wound Gaskets and Sheet Gaskets

Gaskets come in a range of different shapes and sizes.  All are offering similar functionality; gaskets are produced using a range of different materials to suit a range and a variety of environmental factors, industrial uses, and product requirements.  When it comes...

Benefits of Kammprofile Gaskets

Used to prevent leakage, gaskets are constructed to fit between a range of different sizes and types of surfaces in order to provide the perfect seal.  Typically used in pipes and heat exchangers, gaskets are widely used as industrial sealants.  Kammprofile gaskets,...

Purpose of a Kammprofile Gasket

The ultimate purpose of a gasket is to stop leaks while being able to deal with varying levels of compression.  When it comes to Kammprofile gaskets, these are ideal for standard pipeline and heat exchanger applications.  As due to their grooved metalcore, with a...

Are your gaskets completely compliant?

In industries where gaskets are not just important but essential, there are numerous challenges to be faced and considerations to take on board.  This is especially true when it comes to making sure this “essential” element is also compliant.  With the implementation...

Everything you need to know about Manway Gaskets

When it comes to manway gaskets, we want to keep things simple, introducing them as the small sealing ring found in hatches/openings that are constructed for large tanks. Openings which give people access to the inside of the aforementioned tanks and vessels. The...

BACK-UP RINGS

Also referred to as anti-extrusion rings, these are not actual seals themselves but are used in conjunction with ‘O’ Rings and are installed to prevent the extrusion of an elastomeric ‘O’ Ring in its housing groove under certain operating conditions. They can be used in all applications but primarily are used when higher pressures or pressure spikes, higher temperatures and / or larger extrusion gaps form part of the operating conditions. 

They are normally recommended for applications where; 

  • Fluid media pressure exceeds 10 MPa 
  • ‘O’ Rings of low strength elastomers are used 
  • Adverse mechanical conditions prevail 

Back-up Rings

Materials available

  • Virgin PTFE 
  • Filled PTFE – Fillers are sometimes added to the Virgin PTFE to improve some of its basic properties and characteristics, such as, enhanced compressive strength and thermal conductivity, reduced thermal expansion and reduced wear 
  • PEEK™ (from Victrex plc) 

This range of materials, the chemical resistance of which is almost universal, with the exception of molten alkali metals, fluorine gas and elemental fluorine, making them the ideal material choice for ‘O’ Ring Back-Up Rings. 

There are three main manufactured styles of Back-Up Rings 

Spiral Wound – A spiral of two turns is the most commonly used type of construction. This method of production allows the back-up ring to be easily opened to enable easy installation over a shaft and it also ensures the ‘O’ Ring is supported around its entire diameter. 

Solid – Generally used on very small diameters but can be difficult to install 

Endless Split  Single turn can also be supplied as an endless configuration to ensure good support. These can also be scarf split if required although we do not generally recommend this as extrusion can occur at the split 

Alternative Material Options 

Nitrile or Viton Back-Up rings are also available and have the following characteristics 

  • Molded in one-piece contoured design which enables the ‘O’ Ring to keep its shape under high pressure 
  • Can be stretched easily into place 
  • Do not cause the localised wear on ‘O’ Rings  

 

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