Monday, October 13, 2014

Industrial Electric Immersion Heaters

electric immersion heaters
Screw plug and flanged
immersion heaters
(courtesy of Durex)
Electric immersion heaters are used in a myriad of industrial applications. From drying industrial gasses, to freeze protecting cooling tower sumps, to heating acids in plating applications, the versatility of electric heating element can save time, energy and space.

Industrial immersion heaters are used to directly heat a standing or moving fluid by using electric heating elements. There are three primary types of industrial electric immersion heaters; screw-plug heaters, flanged immersion heater, and over-the-side heaters.

At the heart of industrial immersion heaters are the individual heating elements, normally constructed from a stainless steel or Inconel tube containing a magnesium oxide filler and a nichrome resistance wire. Current is applied to the wire which produces the heat, while the compacted magnesium oxide powder provides the electrical insulation, and the metallic tube provides the physical protection.


skid mounted heater
Skid mounted electric heating system
(courtesy of Durex)
Depending on the power requirements of the process, a number of "U" shaped elements are grouped together and welded in to a screw plug or a flange fastener, thus the name of that type of heater.

A variation of the flanged or screw plug heater is the "circulation heater". A circulation heater is a screw plug or flanged heaters fitted in to an accompanying heat exchanger shell (vessel) where fluids are heated while passing through a turbulent flow path. Many times circulation heaters are mounted on skids along with pumps and controls to facilitate the heating of a complete process loop.

duct heater
Duct heater
(courtesy of Durex)
Another variation of the industrial immersion heater is the "duct heater" which is used to heat flowing gases moving though a duct. In this variation, heating elements are bundled in to a square flange intended for mounting through the side of metal duct work.

over the side heater
Over the side heater
(courtesy of Durex)
An "over the side heater" is an electric immersion heater used on open top vessels or baths. Over the side heaters typically have a horizontal bundle of heating elements with a vertical "cold leg" extending out of the process with it electrical housing located safely away from the fluid being heated.

Industrial electric heating elements are available in a wide range of voltages and power densities. Common voltages are 120 volt, 240 volt (single and three phase) and 480 volt (single and three phase). Immersion heater wattages are calculated based upon process requirements (power needed), process media (max. allowable watt densities), and space available.

Options for immersion heaters include integral thermostats, thermo wells, RTDs, thermocouples and high-limit sensors.

Selecting immersion heaters requires experience and application know-how. Consultation with someone experienced in the application and selection of industrial heaters is strongly suggested.