Types EZH and EZHSO
12
Figure 13. Upstream Wide-Open Monitoring System Operational Schematic for DN 25, 50, and 80
V
V
R
R
M
M
S
S
L
L
A
A
B
B
R1
R2
R3
R4
TYPE SA/2
TYPE SA/2
TYPE PRX
TYPE PRX
TYPE EZH TYPE EZHO
Inlet pressure (Pu)
Outlet pressure (Pd)
Motorization pressure (Pm)
Pilot feeding pressure (Pup)
Atmospheric pressure (Pb)
CAUTION
The working regulator must be rated for the
maximum allowable operating pressure of the
system because this will be its inlet pressure
if the monitoring regulator fails. Also, the
outlet pressure rating of the monitoring
pilot Type PRX/125 or PRX/125-AP and any
other components that are exposed to the
intermediate pressure must be rated for full
inlet pressure.
Working monitor installations require a Type EZH or EZHSO
main valve with a Type PRX/120 or PRX/120-AP working
pilot, a Type PRX/125 or PRX/125-AP monitoring pilot for
the upstream regulator, and a Type EZH or EZHSO with
the appropriate Type PRX/120 or PRX/120-AP pilot for the
downstream regulator.
Adjusting the monitor regulator is the same as adjusting the
main regulator. Monitor setpoints are set slightly higher than
the main regulator. However, the value of this difference
cannot be determined in advance, as it depends on the
particular characteristics of each application.
The schematic from Figure 13 represents the conguration
for the DN 25, 50, and 80, for the DN 100 the schematic
remains the same with the remark that a check valve
(Figure 26) must be installed between outlet pressure and
loading pressure impulse lines of the regulator and wide
open monitor as well.
Working Monitor System with PRX Pilot
(Figure 14)
In a working monitoring system, the upstream regulator
requires two pilots and it is always the monitoring regulator.
The additional pilot PRX/125 or PRX/125-AP permits the
monitoring regulator to act as a series regulator to control an
intermediate pressure during normal operation. In this way,
both units are always operating and can be easily checked
for proper operation.
In normal operation, the working regulator controls the outlet
pressure of the system. The monitoring regulator’s working
pilot Type PRX/120 or PRX/120-AP controls the intermediate
pressure and the monitor pilot Type PRX/125 or PRX/125-AP
senses the system’s outlet pressure. If the working regulator
fails, the monitoring pilot Type PRX/125 or PRX/125-AP will
sense the increase in outlet pressure and take control.
TYPE PRX:
S - BLEED PORT TYPE SA/2
B - SUPPLY PORT V - SENSING
L - MOTORIZATION PORT R - PILOT
A - SENSING PORT M - INLET
(20 stránky)
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