Electric heating can be any process where electrical energy is converted to heat. A perfect example is an electric heater. It has various applications that include water and oil heating, cooking and space heating, and it is widely used in industrial processes. An electric heater works on the principle of Joule heating, which is a process where an electric current, when passed through a conductor, gets converted into heat.
Tubular electric heater technology has been in practice for more than 30 years, but more recently, its use in chemical and petrochemical industries has
increased. Improvements in safety features, control schemes and product design have given this technology an advantage over other means of heat.
A basic tubular heating element consists of nickel-chromium (Ni-Cr) wire that provides resistance to electricity generating heat. Compact magnesium oxide (MgO) insulation and a metal sheath surround the Ni-Cr wire (figure 1). Cold pins, or metal conductors, are used to make electrical connections to the resistance wire, and electric termination can be made in various forms. Because MgO is hydroscopic, it is sealed to prevent moisture from entering.
The tubular elements are welded into a flange, making an immersion heater assembly. Normally, an immersion heater assembly consists of heating elements, flange or tube sheet, thermocouples and its housing and bussing for element circuit. To heat a fluid or gas directly, this heater assembly can be bolted into the tank or mounted into a pressure vessel.
Detailed information about the application is required for most applications in the petrochemical industry to ensure successful heater performance. Some of the information required includes: