Drum heaters can take a variety of different forms, though they are all designed to increase the temperature of liquids that are held inside standardized metal containers. There are a few basic categories that these devices fit into. A drum heater will typically be able to warm either many containers at once or just one at a time. Since drums are available in a wide variety of sizes, drum heaters are also created in a number of different configurations. Some drum heaters are meant to decrease viscosity to facilitate pouring or mixing, while others are intended to simply keep the liquid from freezing.
The largest type of drum heater is sometimes known as a drum oven. Mobile versions can fit a single drum or about four barrels on a pallet, though large, heated room-sized units can often hold several dozen drums. These heating rooms can warm up a large number of barrels at once and keep them at a desired temperature for long periods of time, though they are typically also expensive and use a great amount of electricity. The mobile drum heater ovens and devices that only warm one barrel at a time tend to be more efficient.
A band drum heater is a device which is essentially a heating element that wraps around the circumference of a drum to warm it up. These units typically consist of a heating element sandwiched between glass mats and is coated with silicone or other materials. When a band heater is coated with silicone, it can typically be used to warm up metal drums. Plastic drums can also use band heaters, though these units will usually be coated in materials such as polyester.
Another type of drum heater that can warm one drum at a time is the base heater. Many of these units are designed to heat a single drum, though some can fit three or four. One common variant is the induction heater, which can only be used with steel drums. These electric heaters use a magnetic field to create eddy currents, known as Foucault currents, in the metal walls, base, and lid of the drum.
Heating jackets are sometimes also used to warm up drums. These act as sleeves that are drawn tightly over the barrel and heat at the same time that they insulate. Since the heated barrel cannot radiate its warmth back to the atmosphere, these devices tend to be energy efficient. Insulating jackets are also sometimes combined with other heating methods to improve efficiency.