UFC 3-460-03
21 JANUARY 2003
11.9. Emptying the Tank.
11.9.1. Once the operators have removed as much of the petroleum product as possible using existing
installed pumps, remove all remaining fuel with portable pumps. Pump or drain fuel to the lowest
possible level through the pump-out connection or water draw-off line.
11.9.2. Use air-operated, double-diaphragm-type pumps to remove sludge and excess water and or
fuel effluent from the work site. Do not use equipment powered by an internal combustion engine
unless it is equipped with a flame arrestor and a protected ignition system. If used, locate gasoline-
driven engines and electric explosion-proof motors upwind at least 15.2 meters (50 feet) from an
open manhole or vent, or locate it just outside the dike.
11.9.3. Store remaining on-specification fuel in accordance with instructions from the FMF. Dispose
of waste products in accordance with BCE environmental coordinator requirements.
11.10. Isolating the Tank.
11.10.1. Lockout and blind or blank all valves and drain lines, and bypass pressure relief lines to
prevent any product from entering the tank.
11.10.2. Lockout/tagout all electrical equipment and necessary valves. Isolate all piping by removing
valves and installing blind flanges, or by installing spectacle blinds or skillet flanges to prevent fuel
or vapors returning to the tank.
11.10.3. Blind and spectacle flanges must be able to withstand any system pressure to which they
may be subjected. If spectacle blinds are used, insert them between the tank valve and the flange
nearest the tank.
11.10.4. A DBB valve may be used in lieu of blind or spectacle flanges if it can be chained or locked
closed and the cavity bleed valve is opened and observable.
11.10.5. CAUTION: Do not remove valves or disconnect piping from any equipment components
until it is certain that the line has been emptied of fuel and a bonding cable has been installed between
pipe flanges.
11.11. Vapor Freeing.
11.11.1. Ventilate the tank using air-operated eductors, such as COPIS or Lamb air movers. Remove
the roof and shell manhole covers to allow air to circulate freely. Use natural ventilation to aid in
removing vapors. Do not use air movers that blow into the tank.
11.11.2. Fuel vapors are heavier than air, and usually accumulate in the bottom of tanks. Blowing air
into a tank can dilute the vapors, but it may take longer for the vapor-air ratio to drop to an acceptable
level. Eductor-type air movers with a flexible oil-proof hose inserted near the bottom of the tank will
educt vapors in a shorter period of time.
11.11.3. Consider local conditions when placing ventilating equipment. Usually, it is preferable to
exhaust the vapors through roof manholes. This ensures the maximum diffusion of vapors into the
surrounding air and reduces the possibility of a flammable mixture concentrating at ground level.
Regardless of the method used, eliminate sources of ignition in the path of vapors.
11.11.4. Continue ventilation until the tank is essentially vapor-free or the fuel vapors are replaced
with fresh air. The principal consideration for vapor freeing is to help the removal and disposal of
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