35
REV
AL 182
Use, maintenance and warning instructions
MEDIUM PRESSURE REGULATOR
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DESCRIPTION AND OPERATION
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REV. 00
EN
In depressurised conditions, the plug (7) is kept in a shut-off position by the spring (9) and rests on the reinforced gasket
(6). The upstream pressure (Pu), although variable, does not change this position since the plug is fully balanced.
The upstream pressure (Pu) passes through the hole (A) in the stem (10) into the chamber (C). The stem (10) is balanced
between two equal pressures.
The position of the regulator plug (7) is controlled by the diaphragm (8) on which the following forces act:
• towards the shut-off position: the load of the spring (9) and the thrust resulting from the downstream pressure (Pd) in
the chamber (D);
• towards the open position: thrust derived from the loading pressure (Pm) in the chamber (E), fed by the pilot (4).
The loading pressure (Pm) is obtained by taking gas from the upstream pressure (Pu) of the regulator. The gas passes
through the filter (12) and is subjected to an initial decompression in the R31/A pre-regulator (3) up to the pressure value
at the pre-regulator (Pup).
The pressure at the pre-regulator (Pup) passes inside the valve seat (F) of the pilot (4). The plug (13) of the pilot reduces
the pressure at the pre-regulator to the value of the loading pressure (Pm) at the regulator head. The loading pressure (Pm)
is set by comparing:
• the force exerted by the setting spring (14) on the pilot (4);
• the action of the downstream pressure (Pd), which acts on the diaphragm (15) in the chamber (G).
The drive circuit is an open circuit with continuous discharge, through a transfer hole (18) in the diaphragm protection disc,
into the downstream pressure in the chamber (D).
Under normal operating conditions, the plug (13) of the pilot is positioned so that the value of the loading pressure (Pm) is
such that the value of the downstream pressure (Pd) remains around the set value.
If, during operation, the following should occur:
Operating conditions
Operating consequences
Concluding outcome
Decrease in downstream
pressure (Pd) for:
• increase in the request-
ed flow rate;
•
or drop in upstream
pressure (Pu).
Imbalance between the force of the pressure in
the chamber (G) and the setting spring (14) of
the pilot (4) causing:
• increased opening of the pilot (4) plug (13);
• increase in the loading pressure value (Pm)
Opening of the main regulator (1)
plug (7) until forces between the
downstream pressure (Pd) in the
chamber (G) and the pilot (4) calibra-
tion spring (14) have been balanced
again.
Increased downstream
pressure (Pd) for:
•
drop in the required flow
rate;
•
or increased upstream
pressure (Pu).
Imbalance between the force of the pressure
in the chamber (G) and the setting spring (14)
of the pilot (4) causing:
• the plug (13) of the pilot (4) to shut off;
• decrease in the loading pressure (Pm)
due to the transfer of this pressure
between the chambers (B) and (D) of the
regulator (1) through the transfer hole (18)
Close the plug (7) of the main regu-
lator until the downstream pressure
(Pd) has been restored to the pre-set
value and the forces between the
downstream pressure (Pd) in the
chamber (G) and the setting spring
(14) of the pilot (4) are balanced.
Tab. 4.14.
NOTICE!
To check the position of the plug (7), look at the position of the stroke indicator rod (20) referring to the
glass cover (19):
•
fully open 100%;
•
closed 0%.
Summary of Contents for REVAL 182
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