01Start with the failure location
A broken lead at the exit, damage along the sheath and a heater that trips a protective device are different observations. Do not group them all under “burned out.” Record the elapsed operating time, visible damage, controller reading and the event immediately before the fault.
Electrical checks should be carried out by a qualified person with the equipment isolated. A resistance reading alone does not prove that insulation, grounding or hot operating behaviour is satisfactory. Do not repeatedly reset a protective device to keep production running.
02Separate the checks
| Observation | Checks worth recording |
|---|---|
| Repeated failure in one hole | Bore size and condition, block material, heated-length position and local heat removal |
| Damage at the lead exit | Repeated movement, sharp edges, strain relief, temperature and contamination |
| Block heats slowly | Actual supply, switching behaviour, sensor position and thermal contact |
| Trip after storage or cleaning | Moisture exposure, sealing arrangement and measured insulation condition |
03Watch what the controller is measuring
The displayed temperature is the sensor temperature, not necessarily the heater sheath temperature. A sensor far from the heated area can respond slowly. A disconnected or incorrectly configured sensor can also lead to an unsuitable control response. Review the sensor location and fault behaviour alongside the heater.
If several heaters share a block, compare the affected position with the others. Differences in bore condition, nearby cooling passages, material flow or loading may explain why one position fails more often. An investigation is stronger when it records the difference rather than just the failed rating.
04Protect the lead end without trapping heat
Route the leads so normal machine movement does not pull on the heater exit. Keep them clear of abrasion points and provide the specified bend allowance. Sleeving, braid or conduit must suit the temperature and movement at that location; adding protection does not remove the need for strain relief.
Record exposure to wash water, oil or process material. Do not assume that a metal sheath makes the lead exit waterproof. Where contamination is recurring, describe it to the supplier before selecting the termination and seal.
05Send a useful failure report
Include the approved drawing, supply voltage, control method, measured bore dimensions, operating temperature, a photograph of the failed part and one of its installed position. State whether the failure occurs at startup, during a long hold or after cleaning. Avoid assigning a service-life target until the operating conditions are agreed.
↗Technical references
Manufacturer references provide background. Use the approved drawing and instructions for the actual heater; the examples above are not purchase specifications.