6
IOM-5400
SECTION VII
VII. VENT VALVE MAINTENANCE
Actuator Diaphragm Replacement:
a. Paint or embed a set of match marks
between upper case (118) and lower case
(114) across the case flange edge.
b. Loosen and remove nuts (120) and cap
screws (119).
c. Lift up and remove the upper case
(118) assy and set aside. Remove joint
tape (129) and diaphragm (117).
NOTE:
To continue with disassembly skip to
Pressure Pallet Diaphragm Replacement
below.
d. Replace with new parts (129 and
117). Position and align bolt holes in the
circumference of the diaphragm with the
holes in the lower case (114).
e. Reposition upper case assy (118) on
diaphragm (117). Align marks of a. above.
f. Install cap screws (119) and nuts (120)
and tighten.
g. Install pilot body assembly on nipple
(124) tight with CW rotation. Ensure
connector (126) of the pilot valve assembly
is directly above sensing tube connector
(125) of the main valve assembly.
h. Reconnect tubing (127) to fittings
(125),(126). Refer to Section IX for
Calibration and Testing.
Pressure Pallet Diaphragm replacement:
(Disassembly continues from c. above)
a. Paint or embed a set of match marks
between weatherhood (111) and body
(100).
b. Rotate jam nuts (122) CCW coming
down to rest against top of jack screw (121).
Rotate jack nuts (123) CCW coming down
to rest against nuts (122).
c. Rotate jack screw (121) CCW and
remove from threaded end of pallet guides
(109).
d. Grasp case assy (AA) (114/118) and lift
straight up to remove (AA) and weatherhood
assy (111) from pallet guides (109).
CAUTION
If the vent valve must be removed from the tank for
any reason, make sure that all pressure has been re-
leased before the flange fasteners are loosened. Refer
to your company procedures before venting the tank
pressure and when handling toxic or otherwise haz-
ardous materials. Observe all standard safety precau-
tions as specified on Material Safety Data Sheets for
the product(s) in the system while removing the valve
and during the repair.
A. General:
1. The Model 5400 POVV does not require
routine lubrication or adjustments. It should
be checked periodically, at least twice a
year, to confirm that the valve is functioning
properly and that the set point is correct.
2. The pilot valve is designed to function in
a fail-safe manner. The failure of a seal
or a diaphragm will cause pressure to be
vented to the atmosphere; the resulting
loss in pressure will cause the main valve
to open under rising pressure.
3. Periodic inspection for seat tightness
should be done to ensure compliance with
local air pollution control requirements. If
the valve relieves to the atmosphere, this
may be accomplished with a gas detector
calibrated for the principle product in the
system.
4. The vent valve will need to be periodically
removed from the tank for inspection of
diaphragms, gaskets and seals. When this
is done, the vent must be handled carefully
using the lifting brackets and the body.
5. The main and pilot valve housings, bodies,
pallet assembly and other components are
exposed to the process vapor.
B. Disassembly:
1.
Disconnect the tubing connections (pilot
to main valve) (127, 125 and 126) and
remove the pilot by rotating the pilot body
(01) assembly CCW from nipple (124).
