A gasket is a mechanical seal situated between two objects, typically employed to prevent leakage caused by pressure, corrosion, or the natural thermal expansion and contraction of piping systems. Since machined surfaces are never perfectly smooth, gaskets serve to fill these irregularities. Gaskets are typically fabricated from sheet materials such as gasket paper, rubber, silicone rubber, metal, cork, felt, neoprene, nitrile rubber, fiberglass, or plastic polymers (such as PTFE). Gaskets intended for specific applications may contain asbestos.
A washer is a thin plate (usually circular) featuring a hole (typically in the center), primarily used to distribute the load of threaded fasteners. Other applications include serving as a spacer, a spring (e.g., Belleville washers or wave washers), a wear pad, a preload-indicating device, or a locking mechanism. Rubber washers are also utilized in faucets (valves) to seal off the flow of liquids or gases. Additionally, rubber or silicone washers may be used to dampen fan vibrations. Typically, the outer diameter of a washer is approximately twice its inner diameter.
