ProSoft Technology PTQ-AFC - Manual (Page 139)

PTQ-AFC ♦ Modicon Quantum Platform Meter Proving
Liquid and Gas Flow Computer for Hydrocarbon Products User Manual
ProSoft Technology, Inc. Page 139 of 259
June 23, 2011
Unidirectional Pipe Prover
This is a long pipe, with a ball or piston that fills the pipe and moves with the
fluid flow. At each end of the pipe is a switch that is tripped when the ball
passes it. A proving run counts the pulses occurring between the switch trips.
A run is prepared by positioning the ball in a cul-de-sac upstream of the first
switch, ready to be injected into the stream. At the end of the run, the ball is
extracted from the stream and returned via another path to the upstream end.
In order to calculate a meter factor with sufficient precision, the prover volume
must be large enough to count sufficient pulses. Therefore, unidirectional
provers can be quite large.