General Procedures.
Selection of personnel. Only component personnel should be selected for tank cleaning.
Medical certification. All personnel should be cleared by the medics to ensure they are physically fit to
work with the hazards involved.
Training program. All personnel should be required to attend training on the hazards involved and any
special hazards pertaining to a particular tank.
Job assignments. Job assignments should be controlled by the supervisor. This prevents personnel from
overexposure to the hazards.
Preparation. The area surrounding the tank should be inspected for:
Low places where vapors could collect.
Any fire hazards such as electrical equipment, hot work, or open flames.
Entrance to the area. The entrance to the area should be posted with warning signs and guards to keep
unauthorized personnel from entering the area.
The tank should also be inspected for the type and amount of sludge to be removed. The type and amount
of equipment required will depend on the condition of the tank and the amount of sludge to be removed.
Emergency first aid should be available in the immediate area.
Vacuum trucks.
Safety set. The safety set will include such items as fresh air masks, boots, gloves, and hard hats.
Shower and washing facilities will be available for all personnel.
Firefighting equipment.
PART E - EMPTYING, BLANKING OFF THE TANK LINES, AND VAPOR
FREEING
Blanking Off of Tank Lines. Before the tank is opened, all the product should be pumped or drained
to the lowest point. In a situation where a contractor is to clean a tank, a statement should be written stating
that all product recovered is the property of the US government. Blanking off is accomplished by first closing
all the valves nearest the tank, then breaking the connections and placing blinds in all the lines. The clean
out door is then removed, allowing access to the interior of the tank.
Vapor Freeing. There are several means of vapor freeing tanks; however, the best method may not be
the one you use because of environmental considerations. The most commonly used is by forced
ventilation.
Mechanical ventilation. Electric fans are used in this method. All wiring and connections must be
vaporproof.
Natural ventilation. The top of the tank is opened and air is allowed to circulate through the tank until all
vapors are removed.
Steam ventilation. Steam is one of the most effective methods of vapor freeing tanks, but because of
their size, it is not effective on large diameter tanks. Steam is effective on tank trucks and railcars.
During the vapor freeing stages of the operation, have a well-trained man to test the vapors. A variety of
instruments are used to check for vapors.
Explosimeter. Used to indicate the concentration of vapors as a percent of the lower combustible limit,
and not as a percent of vapor by volume. A reading of 100 percent on the explosimeter means that the
tank atmosphere is 100 percent explosive or that a vapor concentration of at least 1 percent by volume is
present. If the tank being readied for cleaning has contained leaded product, the tester may enter the
tank with respiratory equipment when readings on the explosimeter show less than 100 percent of the
lower limit. Inside vapor readings should be taken about one foot above the sludge. If the tank has not
contained lead, it is safe to enter without respiratory equipment when the readings are between 0 percent
and 4 percent of the lower limit.
Hydrogen sulfide detector. The hydrogen sulfide detector consists of a suction bulb, a glass detector
tube, and a frame with a scale. To use the detector, break off the ends of the glass detector tube. The
reading on the scale is shown in percent.
1-5
QM 5096
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