Triple eccentric design principle as follows,
Metal Seated high pressure butterfly valves provide bi-directional bubble tight shut off which achieved by introducing state of the triple eccentric disc geometry.
The valve shaft is off set against the seat and the centre line of the valve body respectively.the seating edges are machined with a continuously changing slope from an angle on top of the oval seat ring to an angle at the opposite side. This geometry ensures that the seat ring stays clear of the seat except at the final shut off position which results long life seat.
Various disc seals are available for each temperature and pressure service applications,solid metal seals are often used for temperatures above 510 degree and up to 815 degree or low temperature service. the laminated metal seal consisted of stainless steel with intermediate material of graphite or ceramic fiber layers is used widely.The laminated seal is secured to the disc with a bolt-on stainless steel retainer and easily accessible for replacement.the graphite laminated seal ring is suitable for tempertures between -40 degree and 650 degree in general. the seal leakage meets API589 or API6D.
The solid metal seating valve can be operated in a temperature range of -253 degree to 815 degree.valve for cryogenic application shall be provided with extended stem.