Screw plug and flanged immersion heaters (courtesy of Durex) |
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 electric heating system (courtesy of Durex) |
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 (courtesy of Durex) |
Over the side heater (courtesy of Durex) |
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.