When trying to choose between a gasket and seal, your first impression might be that they are the same thing. After all, they perform essentially the same function, right? In some ways they are certainly the same, but there are some important differences that you should understand when deciding which one is right for your project.
Gaskets seal a connection between two components or flanges that have flat surfaces, while seals are used between engine parts, pumps and shafts that rotate. Every time any equipment is taken apart and then reassembled, a new gasket should be used. Along with this equipment, gaskets are used wherever a union or flange is required to prevent leaking. Gaskets are manufactured using many different materials. Viton, Neoprene, Nitrile, Pure Gum Rubber, EPDM Butyl, and SBR are just a sampling of the most common rubber or elastomeric materials commonly used to manufacture gaskets. Gaskets can be manufactured from many more diverse products including treated fibre (vegetable fibre), Cork, Cork and Rubber, Non-asbestos (Aramid fibre), Graphite, PTFE or closed cell sponge when a highly compressible gasket is required.
Gaskets are used in many industries including oil and gas, pulp and paper, electric generation and transportation. Gaskets are most commonly used as static seals.
As already mentioned, seals are used between engine parts, pumps and shafts that rotate rather than those that are static. Common uses for seals include keeping leaks from occurring at the end of the shaft where it comes out of the cover and sealing hydraulic lines. This type of seal is generally a moulded or machined product. Seals tend to be flat and round, while gaskets are often cut into different shapes so that they fit the components. Most seals are made of an outer ring that is metal and nests over an inner surface that is often made of rubber. The inner circle is tilted just a bit, which creates a lip for the seal. The lip is designed as a second barrier against any drops that manage to get past the first edge of the seal. The only bad thing about this design is the fact that they can only keep leaks from occurring at one end of the seal, so it is essential that it be installed correctly. If it’s installed backwards, you could end up with a leaky mess on your hands.
When installing the seal, it’s usually fitted into the hole by a press and then tapped further in using a hammer. Lubrication is usually necessary to keep the crankshaft from damaging the seal as it goes through it. Seals are often used in bearings, which is basically just a ball bearing surrounded by a rubber seal, which keeps it from leaking and sometimes reduces the amount of noise that occurs during operation. When a seal breaks down, the entire bearing must be replaced rather than just the seal.
D&D Valve was established over 30 years ago and are importers, stockist and distributors of a wide range of valves, pipes, pipe fittings, flanges and gaskets, covering a wide range of applications to the general and mining industry. With our experience and knowledge in this market, D&D Valve can offer technical advice for most applications. We have also built up a reputation as being a one-stop engineering supply store.