Causes of premature square cartridge heater failure
Premature failure of the box heater occurs when the heat generated in the internal resistance wire is not dissipated efficiently, or when moisture or foreign matter seeps into the inside of the protective sleeve and causes a short circuit. Insufficient heat dissipation will lead to an increase in internal temperature, which will lead to rapid aging of heating elements. This can occur when machining tolerances exceed acceptable limits, the power density is too high, or is powered by the wrong supply voltage.
1.Improper fitting:Improper installation is the most common cause of premature cartridge heater failure. It must be inserted into the borehole to maintain a strict tolerance. Cartridge heaters with high power density are more sensitive because the temperature inside the heater can rise rapidly and endanger the life of the heating element. To ensure adequate heat dissipation, it is recommended that the aperture not exceed the nominal diameter of the heater by 0.002 inches.
2.The typical allowable power density of forged drum heaters is based on fit and operating temperature.
3.Moisture or invasion: Even when drum heaters have helically welded end caps, they are prone to failure if the air around the heater contains high amounts of impurities or moisture and the heater wires are not adequately sealed. This is due to the nature of the MgO insulation: it is a highly hygroscopic white powdery mineral that forms a vacuum when the heater is in thermal circulation and absorbs water or other contaminants (such as oil), which can cause an internal short circuit.
4.Incorrect wattage density: The power density of a heater is critical to its performance. This is a measure of thermal power density, and the higher the watt density, the greater the need for heat dissipation. When heat dissipation requirements are not met, high power densities can lead to premature failure, as the heater's internal temperature will exceed the limit of the resistive heating element.
