| 摘要 |
A meter prover has a piston (40) slidably engaged within a proving cylinder (22) which is in turn coaxially supported within a cylindrical shell (14). In a proving run, flow from the meter to be proved is diverted by closure of a bypass valve to enter inlet (18) in the shell (14). The flow passes along the annular gap between the cylinder (22) and shell (14), enters the bore through apertures (36) and drives the piston along the cylinder in synchronism with the flow. After reopening of the bypass valve equal fluid pressure acting on opposite faces of the piston serves to retract the piston upstream, having regard to the difference in effective piston face areas due to piston rod (42). |
