Anti-extrusion ring put to the test at the Polytechnic University of Catalonia

At Epidor Seals and Rubber Technology, we have tested our anti-extrusion rings in the test bench that we lent to the research laboratory of the Fluid Mechanics Department of the Universitat Politècnica de Catalunya (UPC). We can tell you that the results have been a success. Moreover, in this weekly post, we review how extrusion can affect the equipment and we take a look into the functions to be fulfilled by an anti-extrusion ring working in hydraulic applications.

What is the function of the anti-extrusion ring?

In applications where high pressure stresses are required, or even in assemblies where the extrusion groove is of considerable dimensions, it is common to find assemblies where profiles may appear that incorporate a ring on the back side. This ring is known as an anti-extrusion ring. The main function of this sealing solution is to avoid extrusion of the gasket, caused by the high pressure it has to withstand. Extrusion can occur at these two points:

1. Extrusion groove in stem:
2. Extrusion groove in piston:

The anti-extrusion ring can be found in both static and dynamic assemblies, in O-rings and/or collars.

Our anti-extrusion ring passes UPC tests with ease

Supported by the test bench that we have at the UPC facilities. in Terrassa we have subjected our anti-extrusion rings to a series of tests to guarantee that they fulfil their function to 100%. Below we share a diagram that summarises the conditions of this test that seeks to confirm the sealing performance of the anti-extrusion ring:

• 1. Two equal profiles were assembled, one without an anti-extrusion ring and one with a ring. The profiles are as follows:

1. 2. To further exemplify the results, the two profiles were manufactured in soft material and the ring was machined in POM. Afterwards, a 50,000 cycle test at 200 Bar was launched.
2. 3. Once the test was completed, the system was disassembled and it was observed that, in the housings where the parts without the anti-extrusion ring were installed, gasket remains appeared, as can be seen in the image.

A visual comparison of the images of the two gaskets below shows the extrusion suffered by the gasket without the anti-extrusion ring: In short, the seals designed and manufactured by our team have been shown to withstand the watertightness tests in the series of tests to which they have been subjected on the UPC test bench.

The effects of extrusion can be devastating for equipment.

In all our technical data sheets we indicate the maximum permissible extrusion grooves depending on the application pressure and shaft/piston diameter for the most common materials. A good initial design is the best guarantee to avoid future problems and production stoppages due to problems with the equipment in the plant. At Epidor Seals and Rubber Technology we have a team of engineers to advise our customers on housings and finishes of hydraulic systems.