PRV Set Point Accuracy

Definitions
Definitions
NOTE: For the purpose of this paper we are going to define the following as:
High Volume test bench – PRV Test device with at a minimum capacity volume of 28 Liter [1 [ 1
cubic foot] test vessel and a minimum piping (between the Test Vessel Vessel
and the Test Connection
for the Valve being tested) diameter of 5 cm [2 inches].
Low Volume test bench – PRV Test device with a test vessel less than 28 Liter [1 cubic feet] and
a piping diameter (between the Test Vessel and the Test Connection Connection
for the Valve being tested)
of less than 5 cm [2 inches].
Set Pressure – The value of increasing inlet static pressure at which a pressure pressure
relief device
displays one of the operational characteristics as defined under opening pressure, popping
pressure, start-to start to-leak leak pressure, burst pressure, or breaking pressure. (The applicable applicable
operating
characteristic for a specific device design is specified by the device manufacturer.) PTC 25-2001 25 2001
Opening Pressure – The value of increasing inlet static pressure of a PRV at which there is a
measurable lift, or at which the discharge becomes continuous as determined by seeing, feeling,
or hearing. (For liquid Service) PTC 25-2001 25 2001
Popping Pressure – The value of increasing inlet static pressure at which the disk moves in the
opening direction at a faster rate as compared with corresponding corresponding
movement at higher or lower
pressures. PTC 25-2001 25 2001
Start-to Start to-Leak Leak Pressure – The value of increasing inlet static pressure at which the first first
bubble
occurs when a PRV is tested by means of air under a specified water water
seal on the outlet. PTC 25- 25
2001
Chatter – abnormal rapid reciprocating motion of movable parts of a pressure pressure
relief valve in
which the disk contacts the seat. PTC 25-2001 25 2001
First Steady Stream – Set pressure for liquid Service Pressure Relief Valves. When gravity gravity
overcomes cohesion the water drops straight off the Pressure Relief Relief
Valve outlet; an observable,
repeatable Phenomenon. NB 18
Cohesion – the attraction of like molecules
Note: For the purposes of this paper Test Bench, Test Device, Test Test
Stand, and/or Test Unit are
interchangeable.