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O Ring Colour Identification

O rings come in various colours, and it's important to understand what these colours indicate as the o rings you choose will affect your overall process application.  Ultimately, different o ring colours are used to help differentiate between different materials. ...

Spiral Wound Gasket Compressibility and Pressure Ratings

In order to form a reliable seal, spiral wound gaskets do require a certain degree of pressure.   The applied pressure allows the gasket to be compressed tightly between the mating surfaces preventing any leaks from occurring.  Factors such as operating temperature...

Elastomeric Compounds

What is elastomer?  Elastomeric compounds are rubber seals produced using natural rubbers or manufactured by the chemicals industry.  Elastomeric sealing compounds consist of between 50-60% rubber; the remainder of the compound consists of fillers,...

Is there such a thing as the right flange gasket?

We cannot stress enough how important gaskets and seals can be. Gaskets are vital for an application's reliability and integrity, and trust us when we say, choosing the right gasket now can help you avoid costly issues in the future.  Taking a closer look at pipe...

Plastic gaskets, the best alternative to metal

Plastic gaskets and seals are not that uncommon.  In fact, they’re used in many devices due to the longevity and functionality they offer.  Helping to prevent leaks and maintain temperature control, plastic gaskets help equipment and appliances operate to the best of...

Protecting your seals

Dust gets everywhere.  We see it across the surfaces of our homes and even in our workplaces, especially when the light shines through to show it in its full glory!  However, dust that seeps and builds up within engineering equipment can be disastrous.  Causing damage...

Importance of durometer testing

Durometer or shore durometer is a way for industry professionals to measure how hard such things as plastic, rubber, and non-metallic materials genuinely are.  Its focus is to measure on a Shore A or Shore D scale, looking at how robust material is when examining its...

Metal Detectable O Rings

Metal detectable o rings became a necessary must when it was identified that some chemicals, exposure to extreme temperatures, and continuous vibrations could cause failings in standard o rings.  Failings that not only mean a breaking of the seal, but there is also an...

Tips for best o ring maintenance

If o rings are not maintained, leaks can occur, and water and other fluids can enter the appliance or application, and even product in the mix!  If this happens, damage can occur to internal parts and mechanisms, causing deployment failings, potential false readings,...

What you need to know about O Ring Lubricants

Silicone grease and lubricants aren’t just a nice to have for o rings, but they can quite often be a must-have.  However, with so many greases and lubricants to choose from, it can often be a minefield choosing the best ones and the right ones for your o ring and...

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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