Here’s What Usually Causes O Ring Failure and How it Can Damage Your Project
On January 28, 1986, the Space Shuttle Challenger broke apart shortly after takeoff. An O-Ring failed which caused a breach in the SRB joint it sealed. This led to structural failure in the shuttle and its total disintegration.
Several situations and conditions can lead to o ring failure. Any of them can devastate your construction project. Continue reading to learn more about O-Ring failure and steps to take to prevent it.
Common Causes of O Ring Failure
In general, O-rings are not predisposed to failure. Yet, the manufacturing process requires absolute precision. A difference of only degrees or micrometers can make a difference. There are several common causes of O-Ring failure.
Out-gassing can occur if parts of the elastomer become volatilized when subjected to a vacuum. There are two different types of gas load. You need only be concerned with outgassing from the vacuum-side surface and diffusion transport.
These molecules, often water, come from the bulk to the same surface and then desorb into the air. The process of volatilization can happen during molding if gasses get trapped in the polymer matrix.
Pure polymer O-Rings have a lower risk of outgassing. Choose O-Rings that are correctly temperature-rated for the project application.
Chemical Attack or Swell
Always use caution to avoid the interaction of chemicals that react with elastomers. O-Rings exposed to harmful chemicals can become brittle, soft, tacky, and loses strength. The O-Ring may swell if the chemical compound seeps into it.
Both types of chemical damage results in loss of O-Ring shape and integrity. Thus, it’s important to only use the proper chemical materials within the parameters of the end-application.
High temperatures increase the risk of O-Ring compression set. The O-Ring shape can change and take on the grooves and glands of the contact surface. This decreases their elasticity causing leaks.
Some materials have variable compression set and temperature capability. During production, the chemical structure of the polymer is also important. O-Rings applied in a gland design, require monitoring to check for any over-compression.
Extrusion or Nibbling
Extrusion or Nibbling most often occurs due to high stresses and high friction. When this happens, the O-Ring edge looks nipped or “frilly”. Edge damage to the O-Ring can occur if it gets stuck between sharp edges of two mating surfaces.
You can prevent this extrusion by using a harder seal material. Ensure that you use the proper sized O-Ring. It must also be correctly mounted to reduce clearance gaps and nibbling
Improper O-Ring Size
O-Rings are used in many engineering applications. In the US, most O-Rings adhere to the US AS586 sizing standard. If your project specifications don’t adhere to standard O-Ring measures, you can order a custom size.
Remember to consider tolerances when choosing the O-Ring size. Manufacturing limitations may result in small differences in size. An improper fitting O-Ring can lead to leaks or other failures.
Are You Responsible for O-Ring Installation?
O-Rings require high manufacturing standards as well as precision placement. An o ring failure can be catastrophic for businesses and individuals.
CPV Manufacturing opened its doors more than 100 years ago. During the past century, our company’s goal has been to exceed industry standards for safety and reliability. You can rely on every industrial valve and ORFS fitting for sale surpassing the highest certification standards.
Contact us today to ask questions and order our quality ORFS fittings and industrial valves for your projects.