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O-rings suitable for the pharmaceutical industry

O rings are widely used across various industries to support a variety of different pieces of equipment and applications.  They provide an essential function and are ultimately moulded and manufactured to ensure they provide a continually high level of quality through...

The Best Chemical Resistant Gaskets for Sulfuric Acid

If you are using sulfuric acid on a regular basis within your industry, you might be aware of how corrosive it can be. While it can be useful for dyes, explosives, fertilisers, and many more applications, finding a chemical resistant gasket can often be one of the...

Different elastomers for o rings and various applications

An elastomer is a primary raw material used for most o rings. They are typically manufactured as gum rubber or manufactured synthetically, and surprisingly today, there are approximately over 32 different synthetic rubbers now available.  Elastomer compounds will...

Spiral wound gasket thickness – what’s best?

It is often recommended that using a thinner gasket type/material will result in better sealing performance.  Why?  Because thinner gaskets tend to require much less gasket stress to provide applications with the perfect seal, they also have an excellent response to...

Choosing the correct oil seal application

Choosing and using the proper sealing devices within oil and gas applications can be vital when preventing dirt, dust, water, and other debris from potentially getting inside and contaminating products.  Of course, all rubber materials and seals will provide a range...

Nitrile rubber, NBR, and Buna-N – how well do you know your o ring materials?

A widely used elastomer, Nitrile, Buna-N, or NBR rubber, are all oil and fuel resistant and provide a great level of strength, making them a popular material for seals across various industries.  Suitable for a range of applications, this versatile rubber material,...

Optimum squeezing force for an o ring

It is true that the more squeeze you place on an o ring, the tighter the seal it will provide. In essence, the more squeeze (compression) you apply, the greater the force between the o ring and its mating hardware.  And ensuring you have the perfect seal is all...

O Ring Squeeze

The squeeze and shrinkage on an o ring are vital to understanding as these factors stand in the way of your application either experiencing a perfect seal or your application suffering from leaks.  You can measure the shrinkage of an o ring during...

Keeping your o rings bonded

EMI o rings. Those seal ring gaskets are made of silicone compounds, combining environmental sealing with electromagnetic interference protection.  Consisting of metal or metal-coated particles, silicone o rings are filled with silver, silver aluminium, or nickel...

The importance of mechanical seals when reducing water consumption in mining

Environmental considerations are at the top of most industry's agendas in the 21st century as companies evaluate and improve operations, processes, and systems.  Conserving water in mining is one such area that is now being investigated further with the rotation of...

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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