Gaskets are sheets made of materials such as rubber, silicone, paper, fiberglass, etc. Gaskets can also be made of metals, such as copper. Gaskets are used to provide a leakage proof seal between two pipes, bellows, or flanges. Gaskets work by filling the gaps caused by imperfections in the flange surfaces.
A gasket matches the surface of the flange. Thus, when a gasket is placed between the two flanges and the flanges tightened, it deforms to match the gaps between both the surfaces.
This ensures a leak-proof seal. A gasket should be able to withstand high compressive forces. Gaskets are usually used only once. This is because they deform to match the surface of the flanges. This deformation is unique and hence the gasket cannot be reused.
Gaskets are also used for functions other than sealing. Gaskets are used for vibration mitigation, pressure relief, etc. A gasket is designed to be the weakest point in a system. When the pressure of the system increases abnormally, the gasket will to give way.