O-rings are one of the most common types of mechanical seals. Consisting of a ring-shaped piece of elastomeric material, they are placed around the mating surfaces of two parts. O-rings are designed to prevent leaks from around these mating surfaces. There are instances, however, in which O-rings can fail.
There’s no such thing as a one-size-fits-all O-ring. While they are all ring-shaped, O-rings are available in different sizes. O-rings have an inner diameter size and a thickness size. The inner diameter of an O-ring must accommodate the parts with which it’s used. If the inner diameter is too big, the O-ring will fit loosely over the parts. As a result, pressurized gases or liquids traveling through the parts may leak through the O-ring.
O-rings that are installed improperly may fail. Parts often have a groove around their mating surface. This groove acts as a seat for an O-ring. When installing O-rings, you should check for a groove. Positioning the O-ring into the groove will create a stronger seal that’s better protected against failure. If the O-ring is out of the groove, on the other hand, it may fail.
Exposure to excessive pressure may cause O-rings to fail. With their elastomeric construction, O-rings can withstand pressure. They’ll expand under pressure, and after the pressure has been removed, they’ll revert back to their original size. O-rings, though, can fail when exposed to excessive pressure.
Another reason O-rings can fail is expansion rupture. Expansion rupture is a phenomenon that involves trapped gas or air. Pressurized gar or air may build up underneath an O-ring. As the pressure increases, it may reach a point where it ruptures. The O-ring may essentially burst from this trapped, pressurized gas or air. Known as expansion rupture, it can cause O-rings to fail.
Chemical degradation can cause O-rings to fail. Different types of O-rings are made of different materials. They are typically all made of an elastomeric material, which allows them to withstand a certain amount of pressure. But there are dozens of types of elastomeric materials, some of which may degrade when exposed to various chemicals.
O-rings can fail in different ways. Some of the most common reasons for failure include the wrong size, improper installation, excessive pressure, expansion rupture and chemical degradation. When shopping for O-rings, choose the right type to minimize the risk of failure.
O-rings are one of the most common seals used in machine design today. A mechanical gasket in the shape of a doughnut, an O-ring is a loop of elastomer with a round cross-section, designed to be placed in a groove and compressed during assembly between two or more parts, creating a seal at the interface. They are inexpensive, easy to make, and reliable. Like everything though, O-rings sometimes fail or break, and need to be replaced. O-rings can fail for a variety of different reasons. Today we discuss some characteristics that help us identify a damaged O-ring material, causes of failure, and when they should be replaced.
If your O-ring is not performing as you expected, and there is no visual damage, it does not necessarily mean you have a damaged one. It could just mean you have the wrong size O-ring for the application you are using it with. Once you confirm the appropriate size, here are some troubleshooting tips for identifying damaged O-rings.
Develops circumferential splits within the flattened surface. This is usually due to excessive compression.
Exhibits blisters, pocks, or pits on its surface, due to rapid pressure changes.
Exhibits small cuts, nicks, or gashes. This is typically from installation damages.
Exhibits a flat surface parallel to the direction or motion. Loose particles and scrapes may be found on the seal surface, due to friction from a rough sealing surface.
Develops ragged edges that appear tattered, typically due to excessive clearances.
May exhibit radial cracks located on the highest temperature surfaces. In addition, certain elastomers may exhibit signs of softening. This is due to exposure to excessive heat.
May exhibit many signs of degradation including blisters, cracks, voids, or discoloration, due to chemical incompatibility.
Any of the above conditions warrant the replacement of your O-ring. A good rule of thumb is to replace them once a year.
When it’s time to replace your O-rings, Manufacturer’s Rubber & Supply has you covered. Not only do we carry a wide variety of O-rings and O-ring material, but we also carry an abundance of resources that will make your job even easier. Contact us at Manufacturer’s Rubber today to speak with our experienced team!