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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...

O Ring Replacement

Replacing an O Ring in pressure washer wands is probably one of the most common replacements you'll find when working with seals.  Unfortunately, O Rings don't last forever, and over time they do deteriorate, and you will require an O Ring replacement.  It's important...

Reasons behind seal failure and a look into seal replacement

Unfortunately, there are occasions where O-rings, in particular, fail.  The failure of these seals is not simply due to one factor, but various factors that can occur across a range of applications – hence why locating the exact cause of such problems is just that, a...

Gaskets and seals for Aerospace

Gaskets and seals used for aerospace applications and equipment must be of premium quality and to a substantially high standard.  They are used across a range of applications such as radars, antennas, lighting, access panels, electrical conductivity, pressure sealing,...

Finding the best sealing materials for Food Grade Applications

You will find rubber seals across various industries, providing an important element and operating as a vital fixing across a wide range of different applications and equipment.  However, these FDA gaskets must follow strict, set guidelines, in terms of their material...

The Evolution of Gasket Solutions

When we talk about gaskets and the history of a gasket, we must start at the very beginning.  What is a gasket?  Ultimately, a gasket is a manufactured seal that is used to fill the gap/space between two or more surfaces.  Gaskets are typically manufactured by cutting...

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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