"A heavy duty mainline valve made to hold bubble tight against high pressure. When the block valve is closed, its effectiveness may be checked by opening the bleeder valve for evidence of any leakage from the upstream high pressure side." . "Qualified" . "BLOCK AND BLEED VALVE" . "BLOCK AND BLEED VALVE" . "RDS431594" . "A valve that has one seat which provides a seal, and a bleeder line and valve that are tapped into the block valve's bonnet." . "u82237" . "2005.12.21" . .