4-72. PRECHECK SYSTEM MAINTENANCE (Con't).
e. REMOVAL 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.
From inside tank, loosen nut (20)
and disconnect tubing (21) from
Hold bushing (27) and remove el-
Hold bushing (25) and remove
check valve (26) and bushing
(27) as an assembly. Separate
bushing from check valve.
Remove bushing (25) and nipple
(22) from coupling (24) welded to
tank floor (23).