Hard seal butterfly valve:
Sealing pair are on both sides of the metal material or hard other material referred to as the "hard seal". The seal of the seal performance is poorer, but high temperature resistance; wear resistance, good mechanical properties. Such as: steel + steel; Steel + copper; Steel + graphite; Steel + alloy steel;(where the steel may also be cast iron, cast steel, alloy steel can also be surfacing welding, spraying alloy).
Soft sealing butterfly valve, both sides of the seal side is the metal material; on the other side is elastic non-metallic materials are referred to as "soft seal". This kind of seal sealing performance is good, but not high temperature resistant, easy to wear and poor machinery. Such as: steel + rubber; Steel + [wiki] four fluorine polyethylene [/ wiki]; Such as rotor pump. The advantage of soft sealing butterfly valve is sealed performance is good, defect is easy ageing, wear and short service life.
Hard seal butterfly valves service life is long, but the sealing is relatively worse than soft seal.
