If the exhaust is to be piped to the main valve exhaust or
remotely vented, remove the vent assembly and install
tubing or piping into the 1/4 NPT pilot exhaust connection.
Protect the open end of the exhaust pipe by installing a
screened vent cap.
6. The Type PRX/182 pilot spring case vent (key 12, Figure 7)
must be kept open to atmospheric pressure. Protect the
vent assembly from icing, moisture or debris that may cause
blockage, as required. To change the vent orientation, twist
the vent assembly in the spring case.
7. The Type PRX pilot connections are 1/4 NPT. Connect
the inlet control (sense) line from the “A” port, Figure 6
(key 47) on the bottom of the PRX
Series pilot to a straight
run of pipe 6 to 10 pipe diameters from the relief valve or
backpressure regulator inlet as shown in Figure
3 using
3/8 in. / 9.5 mm or larger outside diameter tubing. If such a
distance is not practical, connect the control line away from
elbows, swages, nipples or any area where abnormal flow
velocities occur.
Startup and Shutdown
CaUTiOn
If pressure is introduced first to the main
valve before the pilot, the main valve may
go wide-open and subject the downstream
system to full inlet pressure.
note
The maximum inlet pressure for specific
constructions are given in Specifications
section. Use a pressure gauge to monitor
inlet pressure during startup.
relief installation (Figure 6)
Startup
1. Close vent valve (not shown).
2. Slowly open block valve and hand valve, if installed.
3. Adjust the pilot as needed.
Shutdown
1. Close block valve and hand valve, if installed.
2. Slowly open vent valve (not shown).
Backpressure installation
Startup
1. Close upstream and downstream vent valves
(not shown).
2. Slowly open upstream block valve first and then slowly
open downstream block valve.
1. Only personnel qualified through training and
experience should install, operate and maintain a relief
valve or backpressure regulator. Before installation,
make sure that there is no damage to or debris in the
main valve body or pilot. Also, make sure that all tubing
and piping are clean and unobstructed.
CaUTiOn
When installing Type EZH trim in an existing
Fisher™ E-body, damage can result if flow is
not in the correct direction. Look at the body
web to confirm that flow is in the correct
direction—up through the center of the cage
and down through the cage slots. Change the
existing flow arrow if necessary.
after assembly, check for shutoff and leakage
to atmosphere.
2. A Type EZH relief valve or backpressure regulator may
be installed in any orientation, as long as flow through it
matches the direction of the arrow on the main valve body.
3. Apply pipe compound to the external pipeline threads
before installing a relief valve or backpressure regulator
with threaded NPT end connections. Use gaskets between
pipeline and relief valve or backpressure regulator flanges
when installing a relief valve or backpressure regulator
with flanged end connections. When installing butt weld
end connections, remove trim before welding and make
sure to use approved welding practices. Use approved
piping procedures when installing the relief valve or
backpressure regulator.
!
Warning
When used in relief valve service, the Type EZH
main valve and pilot both exhaust gas. in
hazardous or flammable gas service, personal
injury, death or property damage may occur
due to fire or explosion of vented gas that
has accumulated. To prevent such injury or
damage, provide piping or tubing to vent the
gas to a safe location. The exhaust piping must
be designed and installed to guard against
excessive flow restriction. This piping must be
protected against condensation or debris that
could clog it.
For safety during shutdown, vent valves
are required immediately upstream
and downstream of the main valve on a
backpressure or bypass installation.
4. If system operation during maintenance is required, install
isolating and vent valves as needed.
5. For the Type PRX/182 pilot, if the vent assembly (key 12,
Figure 7) remains in the pilot body (key 1, Figure 7), then
it must be pointed down if possible or otherwise protected.
4
Type EZH Relief
