Cartridge heaters may fail prematurely if the heat generated by the internal resistance wire is not dissipated efficiently or if moisture or other substance seeps into the protective sheath. This can cause a short circuit. An inadequate heat dissipation can lead to an increase in internal temperature that can quickly cause damage to the heating element. This can happen when the tolerances of machine work are not within acceptable limits, or if the watt density exceeds a certain level, or if there is an error in the supply voltage.
Here are some tips to prolong the life of cartridge heating elements.
#1 Avoiding Contamination
- To ease the removal of a heater from its hold with a release agent such as Thermal Corporation’s Easy-Aid wait until the agent has dried completely before you insert the heater. The heater should be inserted into the hole before the agent has dried. This will cause some liquid to push towards the heater’s lead end, and then soak into it through the insulation, ceramic plug or lava. The heater will fail as soon the power is applied. The heater can be reduced by using a Teflon wire insulation or a Teflon plug, but it does not create a completely hermetic seal. It is recommended that the heater’s lead end be kept below 400 degrees F.
- The heater can become brittle from oil, moisture, or other liquids.
- At elevated temperatures, oil or any other organic material will cause the heater’s lead end cap to carbonize. This can result in a shortening of the leads from the sheath. Visit website to check How to Select Reliable cartridge heaters manufacturers.
#2 Avoid Over-Temperature
- The heater’s lifetime will be reduced if the cartridge heater is not properly fitted in its hole. This is because the heat generated by the heater cannot be transferred to the heated object or material efficiently, and the heater will need to operate at a higher temperature in order to transfer its energy. The heater’s life expectancy will decrease the higher the temperature at which it operates. The rule of thumb for fitting is to keep the hole’s diameter at.005 inches less than the heater’s.
- The lowest wattage heater should be chosen to maintain the required operating temperature and provide sufficient start-up time. A heater that is too powerful will cause the heater to be turned on and off more often than necessary. This will reduce the heater’s life expectancy.
- Important factors when using an immersion heater include the type of fluid used and the velocity at which it passes over the heater. A Thermal Applications Engineer can help you.
#3 Excessive Cycling
- Thermal Corporation uses the following method to evaluate the life expectancy of cartridge heaters. They cycle them from 150°F to 1400°F, and then count the number of failures. The oxide coating on the element wire is subject to rapid oxidization at higher temperatures. However, if the temperature is maintained above 150°F, it protects the wire from further corrosion. If the wire temperature drops significantly, the oxide coating will deteriorate due to contraction, which exposes new metal to further oxidation. The wire’s diameter will eventually decrease and the element’s resistance will increase to the point it is too hot. The element wire will either melt and break open the circuit or cause the insulation to corrode, resulting in a short circuit to the sheath.