XLC 420
9
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MSM
– Upstream pressure sustaining/relief pilot
The upstream pressure sustaining/relief pilot
is a diaphragm operated valve, spring
loaded and direct acting, that can be
installed basically in any position.
The function is nothing but to sustain or
relief the upstream pressure regardless of
flow rate and pressure variations.
Operation
The valve is normally opened thanks to the
force exerted by the spring over the
diaphragm, that is opposed to the upstream
pressure applied directly below it.
When the upstream pressure exceeds the
force of the spring the obturator is pushed up
closing the passage through the pilot and
therefore leading the pressure towards the
main chamber and allowing for the valve to
throttle, which will result in a pressure
increase because of the head loss created
between the valves inlet and outlet.
We obtain the regulation by acting on the
screw (21), i.e. clockwise to increase the
pressure and counter-clockwise to decrease
it.
Disassembly
It is not necessary to remove the pilot from
the circuit for the disassembly. Instead use
the enclosed picture which indicates the
numbers specified here below to perform the
operations.
1- Remove the hood of the pilot (4) loosen
the tightening nut (36) and turn the lead
screw (21) anticlockwise, until the spring is
completely unloaded.
2- Remove the screws (33) holding the cover
(20).
3- Separate the cover, the spring (35) and
the spring guide (7).
22
28
39
27
11
40
33
36
10
26
25
29
04
21
12
35
20
07
16
31
30
41
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