A Useful Guide to Troubleshooting Failed Cartridge Heaters

A Useful Guide to Troubleshooting Failed Cartridge Heaters

A factory line comes to a halt. A malfunctioning heater is removed, replaced, and the machine is restarted by the maintenance crew. The same queue stops once more after three weeks. The heating location has not worked. The team switches brands, but the tendency persists. The cycle will go on forever if we don't know why the heater failed. The ability to troubleshoot malfunctioning heaters can save money, time, and frustration.


Examining the failed heater closely is the first step in any failure study. Don't just throw it away. Examine the sheath's condition, its colour, whether there are any cracks or bulging, and the lead wires' state. The physical look of the malfunctioning component can often reveal the underlying problem to an expert eye.

The initial indications come from discolouration of the sheath. An Incoloy600 single head electric tube heater that has run at moderate temperatures typically has a consistent light brown or golden tint. The heater has been running at temperatures greater than planned if it has a dark grey or black sheath. This may be the result of dry firing, operating the heater above its authorised temperature, a loose fit in the hole, or an excessive watt density. A greenish or bluish tint on the sheath indicates exposure to certain chemical conditions, including sulphur compounds or chlorides.

A significant finding is swelling of the sheath. The water transforms into steam when the heater is activated and the internal MgO insulation absorbs moisture. The sheath may bulge as a result of the internal pressure created by the expanding steam. Moisture seeping through a broken seal or split sheath is nearly invariably the cause of swelling. The replacement heater should have improved moisture protection if swelling is present, such as a longer cold zone to relocate the seal away from the heated area or a better seal at the lead exit.

Sheath cracking is a sign of mechanical or thermal stress. The heater's longitudinal cracks indicate that the sheath's strength was outweighed by the internal pressure caused by steam or thermal expansion. Thermal fatigue, in which the metal fractures at the point of greatest stress due to repeated cycles of heating and cooling, is more commonly associated with circumferential cracks. Both kinds of cracking indicate that the heater's design limitations are being exceeded by the operating conditions. Even though the Incoloy600 single head electric tube heater is made to withstand heat fatigue, this alloy has its limitations. Improving the fit or lowering the watt density can be beneficial.

Mechanical interference or uneven installation are nearly often the source of localised damage, such as a flat spot, a dent, or a burn mark on just one side of the sheath. It's possible that the heater was pushed into an uneven hole or that dirt or a burr in the hole pressed up against the sheath. In certain instances, a localised stress point was created when the heater was bent during installation. The remedy is to make sure the heater is installed straight and to thoroughly examine and clean the bore before installation.

There could be a number of reasons for a total electrical failure without any obvious sheath damage. It's possible that the high watt density caused the internal resistance wire to burn open. It's possible that vibration or temperature cycling caused the resistance wire and lead pin connection to break. Alternatively, an internal short circuit might have happened due to the degradation of the MgO insulating. Information can be obtained by measuring the resistance between the lead wires and the sheath. An infinite resistance to ground indicates that the heater was operating in an open circuit. A short is indicated by low resistance to ground.

Examining the heater's resistance before to installation is another helpful diagnosis. The resistance of a brand-new, room-temperature heater can be computed using the voltage and wattage (Resistance = Voltage² / Wattage). The resistance wire may have partially burnt, increasing the resistance, if the measured resistance is much higher than the calculated value. There can be an internal short if the resistance is much lower. In only a few seconds, this pre-installation inspection might find production flaws or damage from handling or storage.

What happens to heaters that consistently malfunction in the same application position? This is a clear sign of a systemic problem. Document the operating temperature, the measured bore diameter, the watt density, the cycle frequency, and the environmental conditions. Compare these parameters to the guidelines provided by the manufacturer. Frequently, the issue is that the bore has worn over time, increasing the clearance, or the watt density is too high for the application. In one documented case, repeated failures in a plastic injection molding application were traced to a bore that had worn from 6.35 mm to 6.42 mm over five years of operation. The heaters overheated because of the insulating air gap induced by the increased clearance. The issue was resolved by reaming the bore to 6.45 mm and ordering a replacement with a diameter of 6.43 mm.

Voltage mismatch is a less evident reason for recurring failures. The power output will be four times the rated wattage if the heater is operating at 480V even if it is rated for 240V. The heater would frequently overheat and fail in a matter of minutes. On the other hand, running a 480V heater at 240V will only use 25% of its rated power, which could result in a delayed heat-up and inadequate temperature. Make that the supply voltage is equal to the heater rating at all times.

Heater failure may result from a malfunctioning temperature controller in applications. The heater will run uncontrolled if the temperature sensor malfunctions or the controller remains in the on position. Until the heater burns out or a safety limit is reached, the temperature will increase. When debugging repeated failures, it's crucial to use a multimeter to check the controller's output and make sure the temperature sensor is reading appropriately.

Despite its exceptional performance, the Incoloy600 single head electric tube heater is not impervious to damage. Examining a failed heater yields crucial information. In most cases, the root cause can be found using a methodical approach that includes inspecting the sheath, measuring the bore, checking the voltage, reviewing the operating circumstances, and confirming the controller operation. The remedy is evident once the cause is identified. Different solutions are needed for different heating applications. Ordering the same replacement again won't have the same impact as a root cause investigation that results in a design modification or an improved installation. The best heater setup for any application can be suggested by engineering assistance, which can also help with complex problems.