Drum (container) - Background

Background

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 USgal (200 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).

The open-top sub-type is sealed by a mechanical ring clamp (concave inwards) that exerts sufficient pressure to hold many non-volatile liquids and make an airtight seal against a gasket, as it exerts force inward and downward when tightened by a normal three-quarter inch wrench or rachet wrench. Tops exist with bung holes as above, and these hybrid drums with lid can be used to ship many non-volatile liquids as well as industrial powders. Many drums are used to ship and store powdered products as well as liquids, such as plastic beads for injection moulding, extrusion, and purified industrial grade powders like cleansers (e.g., fertilizers, and powdered aluminum). If used to transport dangerous goods across international boundaries, they may need to have UN certification. In general, drum usage is limited to wholesale distribution of bulk products, which are then further processed or sub-divided in a factory.

These metal drums have two openings with flanges (2" NPS and 3/4" NPS). Once the drums are filled, the plugs (bungs) are screwed in the flanges using pneumatic or hand operated bung tightener (plug wrench). Now to secure the contents of the drums against theft and adulteration during shipment, cap-seals made of metal and other types like metal+plastic are used. These cap-seals sit on top of the flanges and are 'crimped' using drum cap-seal crimping tools (also called drum cap sealers). Once cap-seals are crimped, the plugs can be unscrewed only by breaking these cap-seals. Pneumatic and hand-operated cap-seal crimping tools are available. Pneumatic ones are used in production lines for high production.

The Fiber drums referred to above will easily hold 400–600 pounds (180–270 kg), and are usually coated internally with a urethane or plastic protective coating. They have steel reinforcement rims at their ends, and are sufficiently strong that this is the only type of drum that is not reinforced in the middle third, but that is almost certainly due to the difficulty in creating a 'Vee' rib in a paper layer that essentially spirals out from a single end seam.