150-712-200-02
Appendix A - Technical Reference
HRE-712 List 1 and List 2
July 26, 2000
35
V
ALVE
R
EPLACEMENT
P
ROCEDURES
All four of the metal valves shown in
can be replaced if needed. Order the valve replacement
) to obtain new valves. Use the following procedures when
replacing any of the four valves.
Replacing the Pressure Relief Valve
The Pressure Relief Valve (PRV) is part of an all metal, nickel plated brass assembly shown in
The valve acts as a guard against excessive pressure within the enclosure and releases the internal pressure when
it exceeds a nominal level of 15 PSI.
The assembly consists of an adapter that screws into a brass fitting located in the bottom of the base plate and the
PRV valve itself which screws into this adapter. The adapter has two O-rings that are required to create an airtight
seal. One is located on its outer threaded stem that connects to the brass fitting; the other is located at the base of
its inner well where it seals the PRV to the adapter.
To remove and replace the PRV proceed as follows:
1
Grip the adapter nut with a
3
/
4
-inch wrench and the PRV with a
1
/
2
-inch wrench.
2
While holding the adapter nut steady (it should not be moved), loosen the PRV by turning it counterclockwise
then remove the PRV by hand. If the adapter nut becomes loose, tighten it to a torque of 60 inch-pounds.
3
Check that the O-ring in the adapter’s inner well has remained in place. If not, reseat it.
4
Thread the new PRV into the adapter. Do not crossthread.
5
Grip the adapter nut with a
3
/
4
-inch wrench and the PRV with a
1
/
2
-inch wrench and tighten the PRV to 120
inch-pounds of torque. Do not overtighten. Excessive torque does not improve the seal and may damage the
PCV.
6
Pressurize the chamber and check the entire assembly for leaks.
