repeat steam cleaning for one hour. Continue steaming
4-102. Inspecting and Cleaning Tank Interior
until 20% LEL or less is obtained.
(7) After the tank has been freed of combustible
vapors, it is ready to repair, clean, paint, store, change
material, or ship.
Explosive meter check must be made before
entering tank. Air personnel required to be
inside of tank must be equipped with fresh air
(1) Blower/air supply to be used with this
respirators, lifelines, rubber boots, and
procedure shall bean explosion-proof blower conforming
rubber gloves. An observer must be
to MIL-B-7619 or MIL-H-27507. If these blowers are not
stationed at the manhole opening so that
available, local safety personnel may authorize the use of
assistance may be summoned in the event of
another type blower.
(2) After draining tank, leave all valves and drain
(1) Remove manhole lid and enter tank. An
points open, and grounded drain containers in place to
explosion-proof light, flashlight, or electric lantern with
catch fuel during the purging operation. This is to
lens approved for use in hazardous areas must be used for
facilitate maximum air circulation.
(3) Place blower/air supply SO-feet upwind of
(2) Inspect for sediment, solid deposits, or
semitrailer. Ground the blower to the static ground and
foreign matter of any kind. Inspect for corrosion and signs
connect duct to outlet side of blower.
of bad welds.
(4) Start blower BEFORE inserting duct into
manhole opening. This will prevent fuel vapors from
entering duct and going into blower.
(5) Ground duct to the vehicle.
Metal tools, steel wool, steel brushes, or any
(6) Install duct in manhole. Secure with tape or
abrasive cleaning powders must not be used
tie to semitrailer.
to clean tank interiors. Their use would
destroy the thin oxidation film.
(7) Purge tank for two hours. During purging
operation, observe that air is being expelled at all valves
(1) General. Stainless steel obtains its corrosion
and drain points. Trapped fuel may prevent air from being
resistance from a thin film of oxidation that forms on the
circulated through all valves and drains. In the event air is
surface when exposed to air. Care must be taken not to
not coming out of a valve or drain, temporarily close all
damage this film.
other valves and drains and observe if trapped fuel is
expelled. Reopen valves and drains.
(2) Cleaning. Use a lint-free rag (item 24,
to wipe off any sediment
or foreign matter
(8) Remove duct from manhole opening.
any kind that may adhere to the inside of the tank. A
bristle brush can be used to remove solid deposits. Mild
(9) Shut off air supply. Wait 10 minutes.
household powder or soap may be used for removal of
(10) Measure explosive vapor level of tank. Take
readings in several areas of the tank. Reading should be
20% LEL or less. If reading is above 20% LEL, resume
purging operation following instruct ions above.
Compressed air used for drying or cleaning
purposes must not exceed 30 psi (207 kPa).
(11) Purge for one hour AFTER a safe reading is
Wear protective clothing (goggles and
gloves) and use caution to avoid injury to
(12) Remove duct from manhole opening
BEFORE shutting off blower.
(3) Rinsing and Drying. Rinse entire interior with
warm water. Rinse off all soap with warm water. Dry
(13) Close all valves and drains. Leave manhole
entire interior thoroughly. Compressed air or centrifugal
cover open. Tank is now ready to repair, clean, paint, store,
blowers maybe used to speed up drying.
change material, or ship.