Early Warning Judgment Method for Aging Failure of Single-End Heating Rods in Operation

Most production firms choose the passive replacement mode of single-end heating rods, that is to say, the accessories can only be replaced after burnout and shutdown failure. This post-failure maintenance procedure will result in rapid production line closure, scrap of batch product and raise maintenance expense. In reality, single-end heating rods aging failure has clear early warning characteristics in the operation process, including temperature rise delay, power fluctuation, insulation resistance decline and abnormal terminal temperature rise. Mastering scientific aging early warning judgment approaches can achieve predictive maintenance, totally prevent sudden failures and increase the continuity of automated production.

The growth of temperature control hysteresis and the delay of temperature rise are the most intuitive early warning signals of aging. New high-quality heating rods offer a quick temperature rise speed, a sensitive temperature response and steady mold temperature conversion. In the long-term operation, the internal filling loosening, and the surface carbon deposition will limit the heat conduction, which will lead to the mold temperature rise being significantly sluggish, the time to reach the set temperature being longer, and the temperature control hysteresis being larger. It is clear that the production cycle is extended and the temperature increase efficiency is reduced by more than 15%. It shows that the heating rod has entered the medium term aging stage and has to be arranged for inspection and replacement in advance.

Typical early warning signs of electrical aging are an unstable operating current and power fluctuation. The resistance value of the heating rod new internal heating wire is stable, the operational current is balanced without fluctuation. During cold and hot cycle fatigue, the heating wire creates micro-fatigue and resistance drift, causing uneven current jump in operation. The frequent fluctuation of current will result in unstable output power of the heating rod, causing the mold temperature to fluctuate and the product quality to be inconsistent. The continuous current detection of electrical monitoring equipment may efficiently detect early aging concealed risks.

The gradual loss in insulation resistance is the basic precursor of breakdown failure. Insulation resistance is the most accurate metric for evaluating the aging of heating rods. The continuous decline of the insulation resistance value is due to high-temperature age buildup and loosening of the internal insulation medium. When the resistance declines from the initial value of 1000MΩ to less than 100MΩ, the heating rod is in a critical state of insulation breakdown, and electric leakage and short-circuit burnout may occur at any time. Regular insulation resistance detection is the most effective early warning assessment.

Abnormal heating and staining of wiring terminals for oxidation indicate failure of sealing age. The end of the wire of the aging heating rod will have visible high temperature discolouration, oxidation rust and local overheating. The sealing glue layer is yellowing, hardening, and has micro-cracks, the line insulation skin is carbonized and brittle. These events show that the external protective structure has been damaged, and oil mist and dust in the workshop begin to penetrate the interior, which will soon result in internal insulation damp and circuit failure .

The temperature overshoot is increasing and the PID adjustment is more frequent, which reflects the deterioration of the thermal performance. The heating system of new heating rods offers a reliable temperature control with a short overshoot range . After aging, the efficiency of heat conduction diminishes and the thermal inertia increases, which results in noticeable temperature overshoot and frequent power adjustment of the temperature controller. The continuous fluctuation of mold temperature field would directly influence the stability of batch production quality, which is an essential early warning signal and should not be neglected in daily process debugging.

Therefore, the establishment of a complete aging early warning mechanism can change the heating rod maintenance from passive emergency replacement to active predictive maintenance. By monitoring the temperature rise efficiency, electrical parameters, insulation performance and terminal state of electrical accessories, we can accurately judge the aging degree of accessories, arrange replacement during production gap periods, avoid the loss of sudden shutdown, and maximize the service life and economic value of single-end heating rods.