Orifice meter with pressure venting and equalizing safety device

摘要

An orifice meter including a carrier, which is movable between two parallel body walls while maintaining sealing engagement therewith. In one position it seals around the pipeline flow passage, and in a second position it seals around an orifice disc service opening in one of the body plates. A small, axially movable valve plug in the body plate adjacent the service opening is operative in one position to equalize the pressure in the space within the carrier seals with the rest of the valve body and in a second position to vent that space to atmosphere. Interengaging means on the valve plug and a rotatable closure for the service opening prevent removal of the closure unless the valve plug is in its venting position. The valve plug has two annular grooves, each carrying an 0-ring to seal against inner surfaces of axially aligned inner equalizing passage and outer vent passage. A transfer duct opens from between the two passages to the space within the service opening. Bypass ducts opening from the grooves prevent 0-ring dislodgement.