4-72. PRECHECK SYSTEM MAINTENANCE (Con't).
f. INSTALLATION OF CHECK VALVE
When working inside tank, always provide adequate forced air ventilation
at the manhole opening with air directed into compartment where work
is being performed. Forced air ventilation allows for removal of any ex-
plosive quantities and contaminants resulting from the type of work be-
ing done, and serves to prevent oxygen deficiency. Failure to follow this
warning may result in death to personnel.
NEVER work alone inside a tank: a second person must be stationed at
the manhole opening. The person inside the tank must have a safety line
and harness on in case of emergency for rescue operations. in the event
a rescue operation is required, summon assistance IMMEDIATELY. DO
NOT attempt a rescue until assistance has arrived.
All male threads of elbow (19), bushings (25 and 27), and nipple (22) should
be coated with antiseize tape if not already factory-coated with an antiseize
Install nipple (22) and bushing (25) to coupling (24) welded to tank floor (23).
Ensure that check valve (26) is installed in proper direction. An improperly
installed check valve will cause malfunction of precheck system.
Install bushing (27) to check valve (26). Install bushing and check valve as an assembly to
bushing (25). Ensure that check valve is installed with arrow pointing to inside of tank.
Hold bushing (27) and install elbow (19).
Connect tubing (21) to elbow (19) and tighten nut (20).