ProSoft Technology PTQ-AFC - Manual (Page 140)

Meter Proving PTQ-AFC ♦ Modicon Quantum Platform
User Manual Liquid and Gas Flow Computer for Hydrocarbon Products
Page 140 of 259 ProSoft Technology, Inc.
June 23, 2011
Bidirectional Pipe Prover
This is similar to a unidirectional prover, except that use is made of the deadhead
transfer of the ball back to its starting point. Instead of returning the ball via a
separate path, valves are swung to reverse the direction of flow in the prover and
the ball is returned along its original path to trip the switches a second time in the
opposite order. The first pass of the ball is called the forward leg and the second
is called the backward or return leg. The pulse count for the run is then the sum
of the counts for the two legs. Because the run's pulse count arises from two
passes between the switches, a bidirectional prover need be only half the volume
of its unidirectional counterpart and can be correspondingly smaller.