Meter proving apparatus

Claim 1

A proving apparatus for a flow meter comprising a calibration conduit for receiving a fluid, a plug locatable in the conduit to be carried along the conduit by fluid flow, two end stations at the ends of the conduit for accommodating the plug prior to a test operation, two plug detector devices spaced apart along the conduit between the ends of the stations to signal the passing of the plug along the conduit, a second conduit connected to one of the end stations, a first diverter valve in said second conduit, a third conduit extending from the first diverter valve to the said one end station at a location between the connections of the second concuit and of the calibration conduit with said one end station to provide a by-pass for a part of said one end station, a fourth conduit connected to the other end station, a second diverter valve located in the fourth conduit, a fifth conduit extending from the second diverter valve to said other end station between the connections of the fourth conduit and of the calibration conduit with said other end station to provide a by-pass for a part of said other end station and a further valve for connecting supply and return conduits to the second and fourth conduits to establish a fluid flow in either direction through the calibration conduit, the by-passes for the end stations permitting a stabilized flow rate to be established in the calibration conduit, with said plug being located in the by-passed part of one of said end stations, prior to a test operation so that during a test, the fluid flow rate moving said plug through said conduit is substantially constant.