FIELD TRANSFERS: DRUMS
Field transfers of drummed materials are one of the most common mitigating procedures used in hazardous-materials response. The transfers generally involve the use of pumps, hoses, and a subassembly that extends to the bottom of one container or both containers. This part of the transfer system is referred to in industry as a dip tube. Dip tubes, which are used daily in plants throughout the chemical industry, occasionally are referred to as stingers by cleanup contractors.
Dip tubes are extensions of piping or hose systems that place the intake or discharge below the liquid level in a vessel. They are used to ensure that filming, vaporizing, or flammable liquids do not free-fall during filling operations. They also reduce air entrainment and foaming. All free-falling liquids, including water, develop static charges, which induce sparking.
Sparging is another use for dip tubes when a gas such as air for agitation or steam for heating a cold liquid is needed. Sparging an undesirable gas such as ammonia into water often will scrub the gas from the air stream.
All components of a field transfer such as dip tubes, hoses, pumps, and valves must be selected carefully to ensure proper materials of construction for the chemical involved. Industry case studies demonstrate that ignitions, explosions, and releases occur when this point is overlooked. Highresistance, nonconductive hoses that develop high-voltage static charges cause many incidents during flammable transfers.
Transfers of liquids that burn require several critical steps to reduce the risk of ignition.
- All drums, hoses, and pumps must be electrically bonded together and grounded at one point.
- Nitrogen should be used to inert the receiving drum before starting transfer and to make up the vapor space of the
- drum being pumped. Flow should be adjusted to minimize sweeping of vapors into the atmosphere.
- The transfer pump should be in a diked area to minimize secondary contamination.
- Fuming or toxic materials should be transferred in a closed system. If a closed system is used for a flammable, the
- receiving drum should be inerted before final connection of the vapor loop.
If no pump is available or if the liquid’s density is too high for the pump to transfer, a gravity assist or transfer can be used.
In an emergency, a rusted or damaged drum sometimes may be opened using a pry bar and halligan tool as a fulcrumand-punch assembly. Slow, steady pressure will punch the drum with very low risk of friction heat, but the first small hole will release any overpressure.
SAFETY PRECAUTIONS
Visually inspect the interior of all drums immediately prior to transfer. If the material to be transferred is violently reactive, test for the reactants (for example, water for sulfur trioxide, organics for oxidizers).
Use caution when opening drums; bungs occasionally will back completely out of the threaded openings in the head before releasing pressure. Wear full protective clothing for the products involved. At the very least this would be goggles and a face shield plus gloves. A dented drum has reduced vapor space and the liquid may be under greater pressure.
Gas pressure should not be used to make transfers from common flammable and corrosive drums such as DOT 17E and DOT 6C, which are not designed for such uses. However, certain special drums and cylinders are designed for pressure transfers. These can be identified by contact with a product safety specialist.
In general, transfers should be handled by cleanup contractors unless command determines that this action is part of the mitigation of an emergency situation as outlined in 29 CFR 1910.120 (q).
Warning: Neutralizations, also part of hazardous-materials response, are chemical reactions that generate heat and may release gases. Use extreme caution when drums are at the site. As a general rule, neutralizing materials never should be allowed near open or leaking drums. The violence of a runaway reaction in a drum almost is beyond description.
Remember, if it is just sitting there, take your time moving it. Don’t make it worse!*
