9
Figure 10. Type EZH-OS2 DN 100 (Spring-to-Close Version) Operational Schematic
S - BLEED PORT TYPE SA/2
B - SUPPLY PORT V - SENSING
L - MOTORIZATION PORT R - PILOT
A - SENSING PORT M - INLET
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).
Type EZHSO uses inlet pressure as the operating
medium, which is reduced through pilot operation to load
the actuator diaphragm (lower chamber). The upper
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
INLET PRESSURE (Pu)
OUTLET PRESSURE (Pd)
MOTORIZATION PRESSURE (Pm)
PILOT FEEDING PRESSURE (Pup)
ATMOSPHERIC PRESSURE (Pb)
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