Gaskets are mechanical seals, usually formed like a ring and used for sealing of flange joints.In general, gaskets should not be reused.
Various types of gaskets are available depending upon their construction, materials, and features.
The following are the type of gaskets commonly used: Non-Metallic Gaskets (ASME B 16.21) Spiral-Wound Gaskets (ASME B 16.20) Ring Joint Gaskets (ASME B 16.20) Non-Metallic Gaskets are used with flat face or raised face flanges.Spiral-Wound Gaskets are used with raised face flanges.
They are available with an inner ring and outer ring, which is also known as the cantering ring.
This leads to plastic deformation of the gasket.
Thus, the hardness of the gasket is kept less than the hardness of the groove to achieve coining i.e.
bringing two metal surfaces of different hardness so tightly together that the softer surface deforms to match harder surface exactly in shape and finish.Hence RTJ gaskets are not recommended for reuse.Źródło: https://en.wikipedia.org/wiki/Piping_and_plumbing_fitting
Water systems of ancient times relied on gravity for the supply of water, using pipes or channels usually made of clay, lead, bamboo, wood, or stone.Hollowed wooden logs wrapped in steel banding were used for plumbing pipes, particularly water mains. Logs were used for water distribution in England close to 500 years ago. US cities began using hollowed logs in the late 1700s through the 1800s.8 Today, most plumbing supply pipe is made out of steel, copper, and plastic; most waste (also known as "soil") out of steel, copper, plastic, and cast iron. The straight sections of plumbing systems are called "pipes" or "tubes". A pipe is typically formed via casting or welding, whereas a tube is made through extrusion.
These joining techniques are discussed in more detail in the piping and plumbing fittings article.Źródło: https://en.wikipedia.org/wiki/Plumbing#Materials.