The soft seat design

Improvements in valve seat design and technology have expanded the application range of ball valves. Depending on the valve design and seat material, these seats can provide a variety of functions. They need to provide a tight closure in the case of elastic materials, as well as support the sphere in the float design, and be able to provide good cycle life. The seat can also be fitted with a characteristic port for flow control.

The soft seat design, often referred to as a "snap" design, provides full surface contact when assembled, or as a flexible lip design, reduces surface contact, resulting in reduced torque and extended cycle life. Many manufacturers' designs also provide some form of chamber pressure release to prevent damage to the seat and valve when the medium in the closed valve creates chamber pressure.

Currently used soft seat materials include, but are not limited to:
▶ Rubber, including neoprene and nitrile butadiene
▶ Fluoropolymers, including PTFE, TFM, PBI and PFA
▶ UHMWPE (Ultra-High Molecular weight polyethylene)
▶ PEEK (Polyether ether ketone)
▶ Derling
▶ Nylon

Ball valves are designed with metal seats to withstand the harshest application environments, including high pressure, high temperature, wear and flow control. There are many metal seat designs in use today, the most common of which is a solid metal seat with a hardened or coated surface and a lap to a similarly hardened ball, which allows the ball and the seat surface to match for a good seal.