PIETRO FIORENTINI REVAL 182, Use And Maintenance Instructions

Page: 44 / 404

44
REV
AL 182
EN
Use, maintenance and warning instructions
MEDIUM PRESSURE REGULATOR | DESCRIPTION AND OPERATION | REV. 00
BUILT-IN MONITOR OPERATION IN THE EVENT OF FAILURE OF THE
MAIN REGULATOR:
1
2
4
3
B
C
7
6
9
A
5
U
pstream pressUre
D
ownstream pressUre
p
re
-
regULator pressUre
m
onitor LoaDing pressUre
Fig. 4.8. Built-in monitor operation in the event of failure of the main regulator
Should the main regulator (2) fail, the PM/182 monitor (1) will trip until balanced adjustment is achieved.
If, during operation, the following should occur:
Operating conditions Operating consequences Concluding outcome
Decrease in downstream
pressure (Pd) due to:
• increase in the request-
ed flow rate;
• or decrease in upstream
pressure (Up).
Imbalance between the pressure force in the
chamber (A) and the calibration spring (3) of the
pilot (4) which causes:
• increased opening of the pilot (4) plug (5);
• consequent increase in the value of the load-
ing pressure (Pm), inside the chamber (B).
Opening of the main regulator
(2) plug (7) until forces between
the downstream pressure (Pd) in
the chamber (A) and the pilot (4)
calibration spring (3) have been
balanced again.
Increase in downstream
pressure (Pd) with the pilot
(4) plug (5) being moved to
the shut-off position.
Moving the main regulator (2) plug (7) to the
shut-off position due to:
• the plug (13) of the pilot (4) shutting 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
regulator 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. 4.20.