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Tank and Equipment Cleaning and Repairs
(see MCA Safety Guide SD-10, "Recommended Safe Practices and Procedures-Entering Tanks and Other Enclosed Spaces")
Preparation of Tanks and Equipment
Equipment and tank cleaning and repair should be under the direction of throughly trained personnel who are fully familiar with all hazards and the safeguards necessary for the safe performance of the work. All precautions pertaining to education, protective equipment and health and fire hazards should be reviewed and understood.
Tank or Equipment Cleaning
Tanks and equipment, pumps, lines, and valves should always be drained and thoroughly cleaned before being repaired. Workmen should never be allowed to repair equipment while it is in operation and the lines in service. Pipelines into or out of the tank should be disconnected, preferably by removing a small section of line and blanking.
Post danger signs prominently to prohibit smoking, use of spark generating
tools or equipment, flames or any sort, or any other source of ignition and
the presence of unauthorized personnel in the area where tank or equipment
is to be cleaned.
The preferred method of cleaning a tank consists of draining the tank as
completely as possible, filling with water, draining, steaming thoroughly,
and ending with an additional water fill (for cooling) and drain. The
number of water rinses and steaming time required will vary considerably
with the particular process involved (e.g., the presence of solids with
absorbed liquid) and will have to be determined by experience. Cleaning
can be accomplished by water alone, but the time required can be long;
steaming should be used except where other factors prohibit its use (e.g.,
insulation which might be overheated).
Note: The following precautions should be taken:
- The effluent water and steam will almost certainly contain enough
residual epichlorohydrin to present a breathing hazard in the nearby areas.
Therefore, appropriate warnings and respiratory equipment should be used.
Effluent waters must be drained into waste chemical system.
- Epichlorohydrin will likely be trapped under scale or absorbed in any
solids present. This possibility must be carefully checked.
The tank or equipment should then be purged with fresh air and atmosphere within it
should be tested for epichlorohydrin vapors and oxygen content.
Preparing for Tank Entry and Work Within Tank
Special ventilation and a continuous fresh air supply are required during
the entire time men are cleaning, inspecting, or repairing the tank. A
satisfactory method of ventilation is the use of an "air mover" which pulls
fresh air through the tank by induction. Care must be taken to assure that
the air source is not contaminated. Connect ground wire on air mover to
keep static electricity from accumulating.
No workman should enter a tank or vessel that does not have a manhole
opening large enough to admit him while wearing his safety harness,
lifeline, and respiratory protective equipment. It should be ascertained
that the tank or vessel can be left by the original entrance. At least one
other person should be observing
operations from outside the tank at all times.
Proper personal protective clothing and equipment should be worn by anyone
entering a tank for inspection, cleaning, or repairs.
Danger signs should be suitably placed to indicate when workmen are in the
tank.
Lock electrical switches in the off position, remove drive belts, and
otherwise completely safeguard against accidentally starting the agitation
equipment or other moving parts located inside the tank or adjacent to the
entrance.
The portable electric lights and power tools should be in good condition
and the metal noncurrent carrying parts should be electrically bonded to
ground.
It should be ascertained that all sources of ignition have been eliminated
from the vicinity of the tank and that vapor flow from tank is controlled.
In addition to protecting the workmen actually engaged in cleaning and
repairing the tank, attention should be paid to the protection of workers
in nearby areas.
During the course of the work, frequent tests should be made to determine
that the vapor level in the tank is being maintained within safe range.
This precaution is necessary because residues not completely removed by
washing may recontaminate the tank atmosphere.
Emergency Rescue
A supplied-air respirator (hose mask) or self-contained breathing apparatus, together with rescue harness and lifeline should always be located outside the tank entrance for rescue purposes, regardless of type
of respiratory equipment or air supply which is provided for employees
inside the tanks. If compressors are used, the air intake should draw only
uncontaminated air.
One person stationed on the outside of the tank should keep workers in the
tank under observation and another person should be nearby and instantly
available with self-contained breathing apparatus and necessary equipment
to aid in the rescue if a person in the tank is overcome. Protective
clothing should be worn by those entering the tank.
Under no circumstances should a rescuer enter a tank to remove a victim of
overexposure without proper respiratory protection, a safety harness and an
attached lifeline. The free end of the lifeline should be manned by an
attendant located outside the tank. Another attendant should be in view of the outside attendant at all time or in constant communication with him.
If a tank cleaner or maintenance worker is overcome by fumes, he should be removed to fresh air immediately. Artificial respiration should be applied if breathing has
stopped, and physician summoned at once. The rescuer must wear proper
respiratory equipment and protective clothing.
Repairs to Tanks or Equipment
Repairs to interiors or exteriors of tanks or equipment, should be
permitted only after thorough cleaning and testing of the tank to make sure
it is free of vapors and after a work permit has been issued by an
authorized person.
In all cases, if repair work is interrupted, the tank atmosphere should be
checked thoroughly and a new work permit issued before resumption of work.
Waste Disposal
State and local regulations regarding health and environmental pollution must be observed. The agency concerned should be contacted for advice.
All quantities of epichlorohydrin or waste material contaminated with it should be removed to disposal area and burned under supervised conditions. Burning of epichlorohydrin produces hydrogen chloride, and under certain conditions phosgene and carbon monoxide gases which are lethal in high concentrations. Tests should be conducted at operating conditions for hazardous gas emissions.
Water contaminated with epichlorohydrin should be drained to a controlled area. If this is not possible, contaminated water must be diluted with copious amounts of water.
Epichlorohydrin is toxic to fish and other marine life. Ifs TLM24* toward goldfish was found to be 23 milligrams per liter of water.
When a waste disposal problem arises as a result of a major spill or equipment rupture, only properly protected and trained personnel should remain in the area. Notify authorities immediately if epichlorohydrin enters into any surface waters and any water courses or sewers entering or leading to surface waters. The National Response Center,s number for notifying the U.S. Coast Guard or EPA is (800) 424-8202.
TLM24* = Concentration at which 50 percent of the test animals survive a 24-hour exposure.
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