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Type VS-FL
PILOTS
VS-FL relief valves are equipped with the PRX/ series pilots.
model
PRX/182
PRX-AP/182
N.B.: 1/4" NPT female threaded connections
OPEraTION
Figure 3. Closed VS-FL Relief Valve
The diaphragm unit (permanently connected to the shutter) divides the relief valve actuator into two chambers.
The chamber 1 is connected to the atmospheric pressure, chamber 2 is connected to the pilot.
In normal working conditions the two chambers are not containing pressure and the relief valve spring acts on the diaphragm unit
and closes the shutter.
If the line pressure exceeds the pilot set point, the pilot allows the gas to flow from the line to chamber 2.
The shutter moves to its open position when the force produced by gas pressure acting on the diaphragm unit becomes greater
than the load of the relief valve spring.
Once the excess gas is released and line pressure returns to normal working conditions, the pilot stops the pressure flow,
Chamber 2 is no longer being fed, it is emptied through the jet.
The diaphragm unit is pushed upward by the relief valve spring and the shutter moves to its closed position.
4
Table 2. Pilots Type PRX/182 and PRX-AP/182 Characteristics
Pilot
PRX/182
Shutter
Chamber 2
L
B
Jet
A
Diaphragm unit
Chamber 1
Relief valve spring
allowable Pressure
PS (bar)
100
Figure 4. Opened VS-FL Relief Valve
Set range
Body and Covers
Wd (bar)
0.5 - 40
30 - 80
Shutter
Chamber 2
Jet
Diaphragm unit
Chamber 1
Relief valve spring
material
Steel
Pilot
PRX/182
L
B
A
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