Double block and bleed valves operate on the principle that isolation can be achieved from both the upstream and downstream process flow / pressures. This is achieved by two ball, gate, globe, needle, etc. valves placed back to back, with a third “isolatable” valve in the centre cavity. Once isolation has been achieved in one or more of the main process isolation valves, the cavity that is created between these isolations can be drained. This is useful for flow diverting, sampling or injection situations, and for maintenance / integrity check situations where seat leakage can be monitored through the third “bleed” valve.
Specifications
General design criteria
Standard pressure class ratings / end connections
Common materials of construction
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Material specifications
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Standard carbon steel
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ASTM A105A216 WCB WCC
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Low temperature carbon steel
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ASTM LF2 A352 LCC LCB
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Stainless steel
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ASTM A182 F316 ASTM A182 F316L ASTM A182 F304 ASTM A182 F304L ASTM A182 F321 ASTM A182 F347 ASTM A351 CF8M ASTM A351 CF3M
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Specials
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F44 SMO F51 Duplex Super Duplex Monel Hastelloy TitaniumInconel Bronze Alu. Bronze
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Other
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Actuated
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