O-rings and grommets aren’t the same. While they feature a similar shape, they are nuances in their design that affect their utility. For most applications, o-rings and grommets aren’t interchangeable. You may be able to use an o-ring for one application and a grommet for another application.
What Is an O-Ring?
An o-ring is a mechanical seal that’s shaped like the letter “O.” It’s used to prevent leaks around the mating surface of two fluid- or gas-carrying passages. When fluid and gas heat up, they’ll typically expand. Known as thermal expansion, it can cause leaks. The pressurized fluid or gas may push out of unsealed mating surfaces. O-rings prevent this from happening by sealing the mating surface.
All O-rings are used in sealing applications. They are used specifically around mating surfaces to prevent leaks. Pipes, tubes and other passages may require an O-ring to prevent leaks.
What Is a Grommet?
A grommet is a mechanical reinforcement for a circular-shaped opening. They are used to reinforce holes and other circular-shaped openings. Grommets are available in many of the same materials. You can find them in rubber, silicone, polyvinyl chloride (PVC) and more. Grommets are simply rings that are placed around a circular-shaped opening.
Differences Between O-Rings and Grommets
O-rings and grommets are both shaped like the letter “O,” but they are used for different purposes. O-rings are used to prevent leaks. You can install them in machinery to prevent fluids or gases from leaking out of the machinery. Grommets, on the other hand, are used to reinforce openings.
Grommets aren’t designed to prevent leaks; they are only designed to reinforce openings. You can place a grommet around an opening. Holes in metal workpieces, for instance, may be jagged. Rather than leaving this jagged opening in place, you can reinforce it with a grommet. The grommet will cover the jagged opening so that it doesn’t cause bodily injury or damage to any cords running through it.
Another difference between O-rings and grommets is that the former has a smooth exterior, whereas the latter has a collared exterior. Grommets aren’t smooth. The exterior dips in the center, resulting in a top and bottom collar.
You can see an example of a grommet in the photo above. As depicted in the photo, grommets have a collared design. This collared design allows for a tighter and more secure fit. Grommets have a lip that will slide over the openings with which they are used.
