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Monday, October 17, 2011

How Much Pressure can You Withstand?

Did you know that when O-rings - solid-rubber seals shaped like a doughnut - are compressed between mating surfaces they block the passage of liquids or gases? O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable, and have simple mounting requirements. They can seal tens of megapascals (thousands of psi) pressure. To put this in perspective as to how much pressure they can seal, the air pressure in one tire of a family sedan is 32 psi.

O-rings are used broadly in many industries including petrochemical, automotive, aerospace, biomedical and electronics, even your electric toothbrush has an o-ring that prevents the entry of water to the batteries compartment which would damage the electric circuits.

The appropriate performance of O-rings is a key factor for the operation of static or dynamic systems such as pumps, hydraulic cylinder pistons, engines, compressors, and tanks. Therefore, it is extremely important to test O-rings to set their technical specifications and to evaluate their quality.

Due to the circular shape geometry, the related testing standards of O-rings, like ASTM D1414, include a mathematical expression for tensile elongation that depends on the O-ring and the testing fixture dimensions. This expression can be easily handled with a Virtual Measurement and provides the required flexibility to handle tensile tests of O-rings.

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