Cashco 5400 - Manual (Page 6)

6 IOM-5400
SECTION VII
VII. VENT VALVE MAINTENANCE
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 confi rm that the valve is
functioning properly and that the set point
is correct.
2. The pilot valve is designed to function in a
failsafe manner. The failure of a seal or a
diaphragm will cause pressure to be vent-
ed 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
maybe accomplished with a gas detector
calibrated for the principle product in the
system.
4. The vent will need to be periodically re-
moved from the tank for inspection of dia-
phragms, gaskets and seals. When this is
done, the vent must be handled carefully
using the lifting lugs and the body.
5. The main and pilot valve housings, bodies,
pallet assemblies and other components
are exposed to the process vapor.
B. Disassembly:
1. Disconnect the tubing connections (pilot to
main Valve) (48, 57 and 244) and remove
the pilot by rotating the pilot body (201) as-
sembly CCW from nipple (53).
Actuator Diaphragm Replacement:
a. Paint or embed a match mark between
upper case (33) and lower case (32) along
fl anged area.
b. Loosen and remove nuts (35), lock
washer (37), fl at washer (36) and cap
screw (34).
c. Lift up and remove the upper case (33)
assy and set aside.
d. Remove diaphragm (41) and replace
with new diaphragm. Position and align
bolt holes in the circumference of the dia-
phragm with the holes in the lower case
(32).
e. Reposition upper case assy (33) on di-
aphrgm (41). Align marks of a. above.
f. Install cap screws (34), fl at washer
(36), lock washer (37) and nuts (35) and
tighten.
g. Install pilot body assembly on nipple
(53) tight with CW rotation. Ensure straight
connector (244) of the pilot valve assembly
is directly above sensing tube connector
(48) of the main valve assembly.
h. Reconnect tubing (243) to fi ttings
(232), (234) and tubing (57) to fi ttings
(48),(244). Refer to Section IX for Calibra-
tion and Testing.
Pressure Pallet Diaphragm replacement:
a. Paint or embed a match mark between
weatherhood (17) and body (1) along
fl anged area.
b. Rotate jam nuts (55) CCW coming to
rest against top of jack screw (7). Rotate
jack nuts (54) CCW coming to rest against
nuts (55).
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 fl ange 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 specifi ed on Material Safety Data Sheets for
the product(s) in the system while removing the valve
and during the repair.