Principle of Operation
EZH Series – Spring-to-Close Version
CAUTION
The pilot-operated EZH Series
(Spring-to-Close version) will fail in close
position with a main valve diaphragm failure
or lack of pressure supply to the pilot (see
Table 3 for Failure Mode Analysis).
EZH Series (Figure 3) uses inlet pressure, which is reduced
through pilot operation to load the regulator actuator
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pressure assists the main spring that tends to close the
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PRX Series pilot is supplied with pressure coming from
pre-regulator Type SA/2, which reduces inlet pressure to the
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When outlet pressure drops below the setting of the
pilot control spring, pilot control spring force on the pilot
diaphragm opens the pilot valve disk, providing additional
loading pressure to the lower chamber of the regulator
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lower chamber of the actuator diaphragm and pilot escapes
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When the gas demand in the downstream system has
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pressure increases over the setting of the pilot spring, the
pilot valve disk will be closed, reducing loading pressure to
the lower chamber of the regulator actuator diaphragm; the
pressure in the upper case and the main spring will force the
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the regulator actuator diaphragm and pilot bleeds to the
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outlet pressure and loading pressure impulse lines; this valve
is designed to protect the main valve diaphragm assembly
from excessive differential pressure during startup if incorrect
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differential pressure between the outlet pressure and loading
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EZHSO Series – Spring-to-Open Version
CAUTION
The pilot-operated EZHSO Series (Spring-to-
Open version) will fail in open position with
a main valve diaphragm failure or lack of
pressure supply to the pilot (see Table 3 for
Failure Mode Analysis).
EZHSO Series (Figure 4) uses inlet pressure, which is
reduced through pilot operation to load the regulator
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is provided to the regulator actuator diaphragm (upper
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that tends to open the regulator, and opposes the loading
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PRX Series pilot is supplied with pressure coming from
pre-regulator Type SA/2, which reduces inlet pressure to the
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When outlet pressure drops below the setting of the
pilot control spring, pilot control spring force on the pilot
diaphragm opens the pilot valve disk, providing additional
loading pressure to the lower chamber of the regulator
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the lower chamber of the regulator actuator diaphragm and
pilot escapes downstream through the bleed restriction in
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When the gas demand in the downstream system has
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pressure increases over the setting of the pilot spring, the
pilot valve disk will be closed, reducing loading pressure to
the lower chamber of the regulator actuator diaphragm; the
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The excess loading pressure acting under the regulator
actuator diaphragm and pilot bleeds to the downstream
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pilot supply pressure and loading pressure impulse lines;
this valve is designed to protect the main valve diaphragm
assembly from excessive differential pressure during
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Monitoring Systems
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containment; therefore, there is no relief valve to vent to the
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pressure, a monitor regulator installed in series, sensing
the downstream pressure, goes into operation to maintain
the downstream pressure at a slightly higher than normal
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To perform a periodic test on a monitoring regulator, increase
the outlet set pressure of the working regulator and watch
the outlet pressure gauge to determine if the monitoring
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Wide-Open Monitoring System (Figure 5)
There are two types of wide-open monitoring systems:
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upstream and downstream monitoring is that the functions
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from upstream to downstream monitoring and vice-versa,
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5
EZH and EZHSO Series
