
Types EZH and EZHSO
9
Figure 10. Type EZH-OS2 DN 100 (Spring-to-Close Version) Operational Schematic
TYPE PRX:
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)
Type EZHSO — Spring-to-Open Version
Type EZHSO Single-Pilot Regulator
(Figures 11 and 12)
CAUTION
The pilot-operated Type EZHSO (Spring-to-
Open version) will fail in open position in
case of main valve diaphragm failure or lack
of pressure supply to the pilot (see Table 4
for Failure Mode Analysis).
When the gas demand in the downstream system has
been satised, the outlet pressure (Pd) increases. The
increased pressure is transmitted through the downstream
control line and acts on the pilot diaphragm. This pressure
exceeds the pilot spring setting and moves the Type PRX
diaphragm, closing the Type PRX orice and interrupting
the motorization pressure supply to main valve actuator.
The excess of motorization pressure (Pm) acting on both
the main diaphragm and Type PRX pilot bleeds to the
downstream system through a bleed restriction in the pilot.
For Type EZH DN 100 a check valve (Figure 26) is installed
between outlet pressure and motorization pressure impulse
lines; this valve will protect the diaphragm assembly from
wrong procedures during startup, avoiding a too high pressure
differential between outlet and motorization pressure.
V
S
B
L
A
R2
RP IP
IS
R
M
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