11
Figure 12. Type EZHSO DN 100 (Spring-to-Open Version) Operational Schematic
V
M
R
S
B
L
A
R2
R3
RP IP
R4
Monitoring Systems
Monitoring regulation is overpressure protection by
containment, therefore, there is no relief valve to vent
to the atmosphere. When the working regulator fails
to control the pressure, a monitor regulator installed in
series, which has been sensing the downstream and
control pressure, goes into operation to maintain the
downstream pressure at a slightly higher level than
normal pressure. During an overpressure situation, the
monitoring system keeps the customer on line.
Also testing is relatively easy and safe. To perform a
periodic test on a monitoring regulator, increase the
outlet set pressure of the working regulator and watch
the outlet pressure to determine if the monitoring
regulator takes over at the appropriate outlet pressure.
Wide-Open Monitoring Systems
In normal operation of a wide-open conguration, the
working regulator controls the system’s outlet pressure.
With a higher outlet pressure setting, the monitor
regulator senses a pressure lower than its setpoint and
tries to increase outlet pressure by going wide open.
If the working regulator fails, the monitoring regulator
assumes control and holds the outlet pressure at its outlet
pressure setting.
Figure 13 shows an upstream wide-open monitor
Type EZH (Spring-to-Close) and a downstream active
regulator Type EZHSO (Spring-to-Open). With this
conguration, in case of regulator main diaphragm
failure, it will fail in open position letting the monitor work
properly; in case of monitor main diaphragm failure, it will
fail in close position guaranteeing a protection against
overpressure to downstream system.
S - BLEED PORT TYPE SA/2
B - SUPPLY PORT V - SENSING
L - MOTORIZATION PORT R - PILOT
A - SENSING PORT M - INLET
S - BLEED PORT TYPE SA/2
B - SUPPLY PORT V - SENSING
L - MOTORIZATION PORT R - PILOT
A - SENSING PORT M - INLET
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