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Bellow seal valves
Bellow seal valves
Bellow sealed globe and gate valves are available in all types and materials. In bellow sealed valves, a bellow cartridge welded to the valve bonnet and stem replaces conventional gland packing. A bellow is a long accordion-like tube. As the valve stem strokes, the bellows expands or compresses with the stroke movement. There are no sliding or rotating seals through which process fluid can pass. There are two main types of bellows, welded bellows and formed bellows. The latter is made by a relatively recent method in which a uniform bellows is produced from a thin tube. The shaping of the metal is carried out in a collapsible die under high fluid pressure. This is the most rational method of producing weldless bellows. Features: comply with full condition at high temperature and high pressure; prevent leakage of sensitive media which constitute high fire risk; capable of withstanding 20,000 cycles and above without failure under pressure; steam at pressure of 150 PSI escapes through a stem/gland clearance of 1/1000th of an inch at a rate of 24 lbs per hour; gland packed valves often demand continual maintenance - inaccessibility creating particular difficulties; and best suited valve for all critical applications
