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November 2017
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Alert 15-03: Considerations when stacking steel drums

Steel drums are the most widely used type of industrial packaging in the world and are manufactured with consistent strength and durability. Their standardized design and resistance to extreme temperature and humidity contribute to their overall strength and predictability when packaging various hazardous and non-hazardous materials. These properties also contribute to the excellent stacking strength of steel drums. The shippers and users of these containers have confirmed their capabilities with many years of field experience. 

There are many factors that can affect the safe storage and stacking of steel drums. The product packaged in the drum may vary in density which can result in different stack height determinations. For example, some products with a specific gravity of 1.8 are almost twice as heavy after filling than water. In order to provide the proper protection, users should take care to stack and unitize drums properly during both transportation and warehousing. 

Industry experience suggests steel drums used to contain hazardous materials can be safely stacked four-high as long as the specific gravity does not exceed 1.5. Stacking height should be restricted to three-high when the specific gravity of the lading exceeds 1.5 or when the ambient temperature is expected to exceed 30°C (86°F) for prolonged periods of time. These stacking suggestions assume proper drum handling, palletization and stacking recommendations are followed. All steel drums used for shipping and warehouse storage of hazardous materials are required to pass a stacking test in accordance with Title 49 of The Code of Federal Regulations (CFR) § 178.606. The drums are prepared as for shipment and subjected to a top load force equivalent to a 3-meter high stack (9.842 feet). The test is conducted for 24 hours at ambient temperature. The top load weight used during testing is based on the specific gravity of the intended lading.

Following these general guidelines will help prevent leakage of the drum’s contents and ensure the safe storage of filled steel drums. Your drum supplier can assist in determining the proper stacking array.

Recommended Best Practices
Drum closures must be fully installed and tightened to the prescribed torque as specified in the drum manufacturers’ closure instructions as required in Title 49 of the Code of Federal Regulations § 178.2(c).

Drums should be palletized on good quality pallets which provide full support and even contact for the bottom of the drum to minimize drum sag between pallet boards. Drum overhang over the edge of pallets is not recommended. Pallets should have uniform surfaces in contact with the ring on the top of the drum. The pallet should be inspected to insure the stringers are intact, nails do not protrude, no loose boards or excess space between deck boards. Do not use pallets with broken deck boards.

The recommended pallet size is 48” x 48” with 46” x 46” as a minimum to load four drums per pallet. The array of drums should not overhang the pallet. A four-way entry pallet type is recommended.  Pallet manufacturers can assist in pallet design and correct sizing.

If drums are stored directly on the floor, the storage area should be flat and in good condition. A concrete floor is preferable.

Drums should be stacked one-high per pallet with a maximum stacking height dependent on the specific gravity and other conditions.  

Select the proper steel drum for the lading being packaged; see ISDI alerts 14-0614-07 and 14-08 for more information. Drum manufacturers can assist with proper steel drum gauge selection based on the specific gravity and other characteristics of your lading. For solids, the allowed weight should not exceed the actual gross weight tested.

If using a hot filling method, allow the product to cool to ambient before tightening closures to recommended torque values. Do not stack the drums until the temperature has reached ambient and the closures tightened in place.

Do not store or stack drums filled drums in direct sunlight due to expansion of the lading from heating conditions. 

Special provisions must be followed to protect palletized drums filled with flammable and combustible materials. NFPA Code 30 prescribes the safety standards for storing flammable and combustible liquids. To take advantage of the steel drum’s superior safety and storage capabilities, the drums must be stored in a facility protected by a sprinkler system, palletized and equipped with pressure relieving fittings; see ISDI Alert 14-14 for further details

The following specific requirements also apply:

The ceiling or roof height must not exceed 33 feet.

    For three-high, the palletized stack height of the drums must not exceed 10 feet. For four-high, the palletized stack height of the drums must not exceed 13 feet, 9 inches. Steel drums must be equipped with relieving style plugs in the 2-inch and ¾-inch opening. The stack must be protected by a foam-water sprinkler system (also known as AFFF) capable of providing discharge density of .45 gpm/ft2 for stacks three-high and .60 gpm/ ft2 for stacks four-high. The sprinkler heads should be pendant, extra-large orifice (ELO). 

 
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