Operation of the
Internal Relief Valve
5
The internal relief valve is
optional (refer to Basic Models
Table, page 2).
Often called an “IRV”, it is built
into the center of the
diaphragm assembly as
shown in the adjoining sketch
and works in essentially the
same way as standard relief
valves.
It opens when outlet pressure
exceeds the setpoint by
approximately 9” w.c. thereby
allowing excess gas to
escape through the vent to
atmosphere. An optional
spring is available on the 243-
8-2 for relieving at approxi-
mately 20” w.c. above set
point. A cross-section of a
complete 243 with IRV is
shown on page 6.
Performance is given on the
curves at the right. The IRV
will prevent the outlet pres-
sure from exceeding the value
shown by the curves upon
regulator failure at the condi-
tions specified.
The IRV is a proven design of
quality construction. Within its
capacity limits it adds a meas-
ure of safety protection to the
outstanding and dependable
performance of the 243.
Caution: Note that an IRV, like any other relief valve, must be sized carefully. If the curves indicate that outlet pressure can
exceed the maximum safe limit it is essential to provide an additional relief valve carefully sized to handle the difference.
