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What are the Different Types of Immersion Heater?

Immersion heaters are vital for heating liquids in various applications, coming in three main types: flanged, screw-plug, and over-the-side. Each serves unique needs, from industrial tanks to residential water heaters. Flanged heaters offer robust performance for large volumes, screw-plug heaters provide easy installation for smaller systems, and over-the-side heaters ensure versatility for temporary heating. What type suits your needs best? Continue reading to find out.
Susan Zeller Dunn
Susan Zeller Dunn

An immersion heater is a mechanism that heats a variety of fluid types — including water, oil, solvents, salts, plating baths and acids — used in industrial applications. Immersion heaters come in three varieties — over the side, flanged, and screw plug — and are installed in a tank or other vessel. With the heating element immersed in the fluid it’s warming, all of the heat is generated within the liquid and the immersion heater becomes almost 100 percent energy efficient.

An over-the-side immersion heater is commonly used when the installation of a side immersion heater, such as a flanged or screw-plug unit, is inconvenient. Over-the-side units are installed through the top of the tank. Its heat source then rests along the side or on the bottom of the tank. This makes the unit easy to remove for cleaning and provides a generous amount of workspace within the tank itself.

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Over-the-side immersion heaters are constructed using an array of heating elements, including steel, copper, cast iron, titanium and the alloy Incoloy®. The natural flow of the liquid within the tank or vessel allows for an even distribution of the heat. Over-the-side units are available with different kilowatt ratings. They are built in different shapes and utilize different mounting methods, depending on the type of industrial application.

A flanged immersion heater consists of a tubular element that is bent into the shape of a hairpin and welded into a flange. A flange is a projecting disc-shaped rim that allows for one object to be strengthened and/or attached to another object. A flanged immersion heater is installed by attaching it to the matching flange welded to the side of the tank. Flanged immersion heaters utilize a standard pipe flange that ranges from 3 inches (7.6 cm) to 14 inches (about 35.6 cm) in diameter to support the high tank pressure of certain fluids.

Flanged units come in many sizes and kilowatt ratings. They are among the most commonly used methods of heating fluids, and they are designed for use in all tanks, irregularly shaped pressurized vessels, and vats. Flanged immersion heaters are easy to control and energy efficient.

A screw-plug immersion heater, also referred to as a bushing heater, is often used in industrial tanks and processing piping. Like the flanged unit, a screw-plug immersion heater consists of a tubular element bent into the shape of a hairpin. These units, however, are screwed directly into the tank wall through a threaded opening. They may also be screwed into a pipe coupling or welding flange. Screw plug units are available in a selection of sizes from 1/2-inch (1.27-cm) to 2.5-inch (6.35-cm) pipe threads.

Screw-plug immersion heaters also come in a number of kilowatt ratings and a variety of sheath materials. These compact heaters can be manufactured using different types of thermostats. They are ideally suited for freeze protection and process water heating.

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