A thermocouple or RTD is often used within the bundle of elements to maintain the desired target temperature. Extra wiring boxes to make electrical connections are provided with it. Tubing known as a thermowell is used to protect thermocouples and heating elements. Different alloys and materials can be used to suit specific applications. For instance, steel flanges are used for deionized water, lubricant oils, heavy and light oils, waxes as well as mildly corrosive liquids and low flow gas and water tank heating. Stainless steel flanged heating elements are used with mild and severe corrosive solutions and military applications. The sheath materials used can be steel, stainless steel, copper as well as exotic alloys such as incoloy.
Some of the precautions to be taken while designing and selecting an Immersion heater are

• • Selection of the right material for the wet parts to avoid potential corrosion from the fluid to be heated.
• • Proper cold length & active length ratio to avoid hot spots & dry heating.
• • Element skin temperature within the flash point limit of the fluid to avoid any hazard. A Proper thermal design is very much necessary whenever heating a flammable fluid or in hazardous area installation.
• • Fixing method & support for the bundle considering the turbulence during the in & outflow.
• • Control system for both element skin & fluid temperature.