Fisher EZH User Manual

Europe, Middle East and Africa Document Only
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
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 14 represents the
conguration for the DN 25, 50 and 80, for the DN 100
The schematic from Figure 13 represents the
conguration 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
Type 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
Type 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.

S - BLEED PORT TYPE SA/2
B - SUPPLY PORT V - SENSING
L - MOTORIZATION PORT R - PILOT
A - SENSING PORT M - INLET
INLET PRESSURE (Pu)
OUTLET PRESSURE (Pd)
MOTORIZATION PRESSURE (Pm)
PILOT FEEDING PRESSURE (Pup)
ATMOSPHERIC PRESSURE (Pb)

Fisher EZH Specifications

General

Brand	Fisher
Model	EZH
Category	Controller
Language	English