Direct acting PRV Mod. VRCD
6
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When the valve reacts to modulate, in reducing the downstream pressure, the effective pressure
variation on the line depends on the length of the entire system and part of the network subject to
the VRCD. This could take sometimes minutes, therefore allow for it before acting on the spring.
The flow rate is an effect of the pressure reduced by the VRCD for that specific system. A certain
outlet pressure value, for an instance 3 bar, wouldn’t produce the same flow rate everywhere as it
depends on headloss between the valve itself and the final boundary conditions.
Maintenance
The pressure reducer VRCD is sturdy and reliable, and it was designed to minimize maintenance.
A semi-annual visual inspection for the proper movement of the piston and the cleaning of the
compensation chamber is recommended. A routine maintenance for gasket, control, o-rings and if
needed replacements is recommended every 4 years and explained on page (11) ref picture 1 on
page 7. A possible malfunction can be identified by a leakage through the seat, normally caused by
dirt accumulated inside the body, seeping through the shaft and leaking through to the cover,
hunting and excessive variation of the downstream pressure.
Set up
Before the start-up of the valve make sure the instructions provided on the maintenance
section
“Installation” on page 5 were properly followed and understood.
Operate very slowly on the following procedure to avoid stresses on the valve and
unexpected pressure surges.
The valve is initially isolated from the main line by means of the sectioning devices
upstream and downstream.
Open the upstream gate valve by 30%, then open slowly the downstream sectioning device
to generate some flow through the valve. Make sure the maximum nominal pressure is not
exceeded during this operation
Unless the valve has been ordered with a specific setting turn the adjusting screw (9)
anticlockwise to relief the spring (not completely), make sure VRCD will respond with a
smooth modulation by reducing the downstream pressure.
Open completely the upstream gate valve.
Let VRCD work and modulate according to the demand, act on the adjusting screw (9) by
turning it clockwise to increase the downstream pressure and check the pressure gauges.
Allow for enough time for the system to balance.
By means a pressure gauge upstream and downstream and a flow meter make sure that
both the flow rate and difference in pressure, in dynamic condition,
doesn’t go above the
recommended values displayed in the catalogue.
Be sure to allow for 5 mt increase in the set pressure occurring between dynamic and static
(no flow) conditions
