- Drum (container)
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 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 one hears about (the quoted price thereof) in the daily financial news reports. In the US, 25-US-gallon (95 l; 21 imp gal) drums are also in common use and have the same height. This sameness 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.
A 55-gallon drum (known as a 44-gallon drum in the United Kingdom, Canada, Ireland, Australia, New Zealand, South Africa and other former British dependencies, even though all those countries now officially use the metric system and the drums are filled to 200 litres) is a cylindrical container drum with a nominal capacity of 55 US gallons (46 imp gal; 208 L). The exact capacity varies with wall thickness and other factors. Standard drums are 22.5 inches (572 mm) in diameter and 33.5 inches (851 mm) high (these dimensions yield a total volume of ~218 L). Exact dimensions are specified in ANSI MH2.
The drums are typically made of steel with a welded top and ribbed outer wall to improve rigidity and durability. They are commonly used for transporting oils and fuels, but can be used for storing various chemicals as well. The construction and performance of drums used for shipment of dangerous goods or hazardous materials are strictly governed by UN, country, and carrier regulations.
The 55-gallon drum will fit handily four to a standard wooden shipping pallet, and so ease handling by a fork truck and shipping. The drum's size, shape, and weight distribution lends itself to being moved about readily on the loading dock or factory floor with a two-wheeled hand truck. They can also be moved by hand short distances on firm surfaces by tilting and then rolling along the base, which is designed especially for that purpose.
Today's 55-gallon drum resulted from military shipping requirements in World War II, the first war in which trucks, cold rolled steel, stamp or pattern forging machinery and welding were widely available. The drums helped win the Battle of Guadalcanal in the first U.S. offensive in the South Pacific Theater. The U.S. Navy could not maintain control of the seas long enough to offload aviation fuel for U.S. aircraft ashore, so the drums were often transported to the island on fast ships such as destroyers and shoved over the sides (or, time permitting, lowered in cargo nets). Aviation fuel is lighter than seawater, so the drums floated, and Navy Seabees in small craft corralled the drums.
Closed-head steel barrels and drums used for shipment of chemicals and petroleum products have a standardised bunghole arrangement, with one 2-inch (50.8 mm) NPT and one 3⁄4-inch (19 mm) NPT threaded bunghole on opposite sides of the top head. This arrangement is echoed in many plastic drums in the same size. Various components can be mounted to the drum, such as drum pumps and bung mixers.
In the past, hazardous waste was often placed in drums of this size and stored in open fields or buried. Over time, some drums would corrode and leak. As a result, these drums have become iconic of pollution problems, even though they have numerous uses and are ubiquitous in commerce. Drums are often re-conditioned and then later used for storing different liquids. Shipping in reconditioned drums is one of the safest ways to remove hazardous waste.
Until the 1990s many state highway departments reused 55-gallon drums as barricades to protect construction workers from oncoming traffic. Once empty, the drums were painted orange and white and placed along roadways where construction and repairs were occurring. Today, construction crews more likely use plastic drums that resemble their steel predecessors in both size and shape. Also alongside the highways now are groups of specially engineered plastic drum-like containers arrayed in front of vulnerable locations such as large sign supports or bridge abutments, to protect errant motorists who otherwise might collide with these rigid structures. These "Fitch Barriers" often contain sand-filled compartments that break apart on impact, absorbing some of the energy of the collision, often saving lives.
General references, further reading
- Performance tests of selected plastic drums, National Research Council Canada, February 2005. TP 14396E, Transport Canada, 
- Drop tests of selected steel drums, InNOVAcorp, 2003. TP 14093E, Transport Canada, 
- Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002, ISBN 1-930268-25-4
- Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6
Wikimedia Foundation. 2010.