
52 | BHGE
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dome seal.
3. Back pressure testing for leakage
a. Backpressure is the pressure measured at the valve
outlet, in pounds per square inch gauge (psig or barg).
b. Backpressure tests are to be performed after
adjustment of set pressure and blowdown on each
valve designed for use in a closed system having an
inlet size greater than 1” (25.4 mm) NPS.
c. The pressure, at which the valve is to be backpressure
tested, shall be 30 psig (2.1 barg)(minimum) or system
backpressure, whichever is higher. Air or nitrogen shall
be used as the test medium for applying backpressure.
d. Backpressure tests are to be performed by applying
pressure with air or nitrogen to the valve outlet and
the valve dome. Pressure may be applied directly
to the valve dome or via the pilot valve. Leakage
may be detected by application of soap solution, or
equivalent, at points of possible leakage. Pressure
is to be held constant at the test pressure while the
valve is being examined for leakage.
e. The following points shall be examined for leakage
during backpressure testing.
(i) Cover Plate, inlet and outlet joints.
(ii) All tube fittings and connections.
(iii) Possible point of leakage on the pilot valve.
4. Drain all water from pilot valve, main valve, and tubing
after completion of testing. Compressed air may be used
to aid in drying.
XX. Setting and Testing (Cont.)