We recently highlighted three common causes of O-ring failure. But there are more.

This article highlights three more frequent causes of failure.

1. Explosive decompression results when, after a period of service under high pressure gas, when the pressure is reduced too rapidly, the gas trapped within the internal structure of the O-ring expands rapidly, causing small ruptures or pitting on the O-ring surface. Solutions include: increase decompression time to allow trapped gas to work out of seal material; choose a seal material with good resistance to explosive decompression; and if the problem persists and pressures are very high, consider the use of a metallic O-ring or C-ring.

2. Another rather common type of O-ring failure is abrasion. This is usually found in dynamic seals subject either to reciprocating, oscillating or rotary motion. Solutions include: use proper surface finish; provide adequate lubrication by use of proper system fluid; consider use of internally lubricated O-rings to reduce friction and wear; check for contamination of fluid and eliminate source; install filters if necessary; and consider changing to an O-ring material with improved abrasion resistance.

3. Many O-ring failures can be directly attributed to improper installation. In spite of its simple appearance, the O-ring is a precision device requiring care during installation. Solutions include: break all sharp edges on metal components; provide a 20-degree lead-in chamfer; check all components for cleanliness before installation; tape all threads over which the O-ring will pass; use an O-ring lubricant; double check the O-ring to ensure correct size and material; and be careful.

The failure of an O-ring in service can usually be attributed to a combination of causes. Most often, with the absence of one of the conditions existing at the time of failure, the O-ring would have continued performing. It is important to maximize sealing life and reliability by reducing the probability of seal failure at the onset by the use of good design practices, proper compound selection, pre-production testing, and continued education and training of assembly personnel.


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