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The following is a glossary of terms used in the website.

Fixed, Rod Elements - The rod element comprises of a resistance heating coil surrounded by compacted magnesium oxide powder enclosed in a tubular metal sheath. The element is brazed to the heater boss or flange.
If an element fails the entire heater must be replaced.

Glanded, Rod Elements - The rod element comprises of a resistance heating coil surrounded by compacted magnesium oxide powder enclosed in a tubular metal sheath. The element is brazed to glands that are bolted to the element flange.
If an element fails the individual element can be replaced, however, the vessel must be drained and the heater removed from the vessel.

Removable Core Elements - A removable core element comprises of resistance wire wound inside ceramic formers. Removable core elements are inserted into element tubes which are expanded, brazed or welded into the heater flange.
If an element fails the individual element can be replaced without draining or removing the heater from the vessel.


Element Materials:

The proper selection of element material is generally dependent on the corrosion resistance of the element material in the environment in which the heater is operating. Watts Density, in conjunction with element material, has a large effect on corrosion resistance.

The following is a list of commonly used element materials.

Rod Elements

Copper	Suitable for soft and normal waters. Generally only used in domestic immersion heaters.
Nicalloy 800	This is a high alloy stainless steel which has good temperature resisting and corrosion resisting properties. Recommended for air heating applications and for immersion heating applications in normal waters. This material can be subject to corrosion in waters containing chlorine.
Nicalloy 825	This is a high alloy stainless steel and has excellent corrosion resisting properties. Generally this material can be used in hard and aggressive waters and a range of chemical solutions.
Other Materials	Other materials which are available include stainless steel (321 and 309), titanium and cupro nickel.
Removable Core Element Tubes Because removable core elements operate at much lower watts densities compared to rod elements and have much heavier wall thicknesses the range of conditions that they can operate in is far wider.
Mild Steel	Suitable for oil heating and low concentration caustic (sodium hydroxide) solutions. Can also be used for water heating in closed systems. Integron mild steel tube has an increased surface area which allows the reduction of element lengths.
Stainless Steel 316	Generally suitable for hard water conditions and certain chemical solutions including caustic soda (sodium hydroxide). Not suitable for water or solutions containing chlorine.
Copper	Generally suitable for use in hard and aggressive water conditions, particularly waters with high chlorine concentrations such as desalinated water.

Element Watts Density:

Element watts density is defined as the amount of watts given out per unit surface area of element. High element watts density reduces the life of an element and increases significantly the effect of corrosion on the element sheath. High element watts density causes water to boil around the element and produces a noise similar to that of a boiling kettle. Where an immersion heater has been fitted close to sleeping accommodation it has been known for this noise to keep people awake at night.

Due to their design, removable core elements operate at low watts densities which generally allows them to operate with significantly less corrosion problems compared with rod elements. Generally removable core element watt densities are below 3.1W/cm² (20W/in²).

With the exception of domestic heaters and some light industrial heaters the standard watts density for rod element heaters is 9.3W/cm² (60W/in²). This is suitable for heating most types of water. Where water conditions are very hard or aggressive particularly in respect of desalinated water or where chemical solutions are being heated, please contact our technical department to obtain the correct element specification.