Double block & bleed valves

It has been customary for manifold systems and other process piping, where inter-contamination of products was undesirable, to position two valves back to back with a small bleed valve located between them. This is commonly referred to as a “Double Block and Bleed System” or “Block and Bleed Service.” Using TFE or RTFE as a seat material has permitted the substitution of a single valve for the two valves which made up the previous system. A bleed valve is required and is connected to the body cavity around the ball of the ball valve. A Double Block and Bleed application requires that both seats be tight and act as upstream seals when there is pressure on one or both sides of the valve, with the cavity around the ball being bled to atmosphere by open- ing the body drain valve.

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