What is a Cartridge Heater and How Do They Work?

A cartridge heater refers to a cylindrical tubular device that is used while heating in order to provide accurate and compressed heating for several distinct forms of equipment, machinery and materials. When set side by side with an immersion heater, in terms of furnishing internal radiant heat, a cartridge heater is usually inserted inside a hole that is already provided in the item that is undergoing heating. They are required for providing precisely directed localised heating for a wide range of manufacturing processes.

Cartridge heaters make the task of installation pretty simple and straight-forward while also offering an even heat pattern in order to meet the requirements that have been already preset in the application. To simplify the process of installation, heaters are designed with a slightly smaller diameter in comparison with the hole into which they are going to be placed or installed so that it gives a snug tight fit.

The cartridge heaters are widely used to heat up the metal blocks from the inside at a predetermined wattage so that the requirements or demands of the application can be met. During the process of heating metal blocks, taking the measurement of a diameter to be faintly larger than the size of the cartridge heater, a hole is drilled into the piece.

How a Cartridge Heater Works

It is possible for operating wattage in terms of cartridge heaters to be either low, medium, or high. They are made or designed in such a manner that they can easily endure temperatures of up to 760° C / 1400° F. Cartridge heaters have immense usability as they are adequately concentrated and provide localised heat precisely in order to meet the requirements of a wide range of manufacturing applications.

Insertion Point

To start using the cartridge heater it first needs to be inserted into the point of insertion.  An insertion point or port is made available on the device going to be subjected to heat when using heavy duty cartridge heaters. Similarly, holes are drilled when using metal blocks and metal molds.

In case of heating objects that are uniform in shape, a hole is drilled in the cartridge heater in order to provide the most radiant heat. When it comes to complex molds and other equally complex machinery, the placement of the hole seems to get a notch more complicated and could require precise planning ahead of time.

Cartridge Heater Diameter

A very important thing to keep in mind while considering the placement of a cartridge heater is that it mainly depends on the diameter of the hole that it is going to be placed in. To avoid further confusion, it is advised to follow a basic rule that the diameter of the heater is undersized (by 0.004 inches) when speaking about its relation with the hole where it is being placed.

Heated Length

The heated length means the length of the cartridge heater excluding the portion that remains unheated. It is important to note that the length that is heated must be the same as the length of the item that is being heated if achieving optimal performance is on your mind. Any part that is left unheated will initially result in hot spots and may eventually cause the entire heater to fail. The standard that is used for optimal efficiency in terms of high-density cartridge heaters is 6 mm towards the disc end and around 10 mm towards the lead end. A heater that has an overall length of 152 mm would have around 136.5 mm of its length heated.


The application for which the cartridge heater is being used is the deciding factor for the temperature at which a cartridge heater would be operated. There are several factors that may have an influence on the operating temperature, like, thermal conductivity, its ability to tightly fit inside the hole, along with watt density of the material that is being subjected to heat. There is a requirement for a special electrical terminal, in cases when cartridge heaters are being used at high temperatures.

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