Preventing Heater Failure
Understanding the causes of heater failure will extend the life of your heater and ensure that it is working as efficiently as possible. There are three main culprits to be on guard for: physical abuse, application issues, and excessive temperature, any one of which can cause your heater to quickly fail.
Physical abuse can easily occur during the shipping and handling of a heater. Mishandling the heater can lead to damaged screw terminals or lead wires, so it is essential to take care in unpacking and installing your heater. A damaged lead wire can result in the heater element shorting out, arcing, or the heater failing very rapidly once power is supplied to it.
Application issues can develop when the heater is not used with the ideal specifications or the lead wire is damaged due to movement, such as cycling back and forth. You can avoid damage, such as lead wires being pulled from their connections, by making sure all of the components fit properly. Another common application issue is contamination from water, oil, or molten material like plastics. Corrosive material landing on the heater, especially where the lead wires connect to it, can quickly lead to heater failure.
All heaters have an upper temperature limit. Excessive temperature will shorten the heater’s life. Cartridge and band heaters are designed for conductive heat transfer. When conduction is limited, heat will be transferred using convection or radiation, which is not as efficient as conduction. If heat cannot move away from the heater quickly enough, the heater will continue to get hotter, leading to the oxidation of heater components. When oxidation builds up on wires and tubing or on the inside of the sheath in a band heater, one of two things happens: the conductor inside the oxidation fails as an open circuit or the oxide layers meet causing an arc or short resulting in heater failure. To extend the life of a heater, it is vital to create an environment where as much heat as possible is transferred through conduction. If a cartridge heater fits loosely in a hole, there will be a lack of conduction and the heater might as well be operating in open air. A band heater that is not installed snugly around a barrel or retightened after heating up will achieve less heat transfer through conduction, resulting in poor performance and ultimately a shorter life.
In order to achieve optimal results from a cartridge or band heater, follow the handling instructions, install the heater with care into the proper application environment, and ensure the heater is achieving the maximum heat transfer through conduction.