A drum is a cylindrical container used for shipping bulk cargo. Drums can be made of steel, dense paperboard (commonly called a fiber drum), or plastics, and are generally used for the transportation and storage of liquids and powders. Drums are often certified for shipment of dangerous goods. The construction of drum needs to meet applicable regulations and is usually matched for compatibility with the specific product shipped. Drums are also called barrels in common usage.
It is common to hear a drum referred to as a barrel and the two terms are used nearly interchangeably. Many drums have a common nominal volume of 55 US gallons (46 imp gal; 208 L) and nominally measure just under 34.5 inches (880 mm) tall with a diameter just under 24 inches (610 mm) and differ by holding about thirteen gallons more than a Barrel of Crude Oil . In the US, 25-US-gallon (95 l; 21 imp gal) drums are also in common use and have the same height. This allows easy stacking of mixed pallets. Barrels can be constructed of plastic, laminated paperboard or steel.
The two common sub-types of drums are the open top and the welded top (with 2-inch (51 mm) NPS bung holes). The latter are almost universally called ‘barrels’ in preference to drums in the US. They cannot efficaciously either dispense or be filled with powdered goods, though they might store them very well, so are not used for such goods, being reserved for liquids transport and storage. Plastic drums are manufactured using injection blow moulding technology and have either a separate lid (similar to those on fiber drums) or a welded type top with the bung holes molded in. Metal drums are manufactured with steel hot-rolled into long pipe-like sections then forged on a stamping press while still red-hot into drum bodies. A welded rolled seam is then made for the drum bottom, or bottom and top both.
Some drums have reinforcing rings of thickened metal or plastic at four places: top, bottom, and one each a third of the way from each end ring. This sufficiently strengthens them so that they can readily be turned on their sides and rolled when filled with heavy materials, like liquids. Over short to medium distances, drums can be tipped and rolled on the bottom rim while being held at an angle, balanced, and rotated with a two-handed top grip that also supplies the torque (rotational or rolling force).