During on-site inspections, if oil seepage is found on the sealing surface of the heating element's terminal enclosure, local discoloration of the housing, or the temperature at the explosion-proof cable gland is noticeably higher than that of adjacent pipelines, it usually indicates that the heating element has been operating long-term under conditions close to the upper limit of its temperature class, or that the seals have entered their aging cycle. Such signs do not affect short-term operation, but should be added to the checklist for the next shutdown maintenance.
The cover bolts of the terminal enclosure should be tightened in diagonal sequence in several passes to avoid excessive flameproof joint clearance caused by one-sided stress; the cable outer diameter must match the cable gland specification, and the cable must not loosen when gently pulled after tightening. The portion of the heating element immersed in the medium should be fully covered by liquid; it must not be put into operation when the liquid level is below the heating section, to prevent surface temperature overrun caused by dry firing.
Daily inspections can focus on recording three data items: the surface temperature of the terminal enclosure, the fluctuation range of the medium outlet temperature, and the sealing condition at the connection between the heating element flange and the cylinder body. In heat transfer oil systems, low circulation pump flow will cause the local temperature of the heating section to rise; when the difference between outlet temperature and return oil temperature increases abnormally, flow should be checked first rather than directly adjusting the power setting.
The heating element can work with control loops for parameters such as outlet temperature, flow, and pressure to achieve automatic regulation, and supports networking with a supervisory monitoring system. In on-site operation and maintenance, it is recommended to retain the manual output limiting function to limit output power when the sensor fails, avoiding continuous full-power operation. Fast thermal response and high temperature control accuracy are common characteristics of such components in circulating heating systems.
It is recommended to check the corrosion of the flameproof surfaces, the elasticity of the sealing rings, and the tightness of the wiring terminals in conjunction with the shutdown plan; before restarting after long-term shutdown, the insulation resistance of the heating element to ground should be measured. When replacing seals, use materials consistent with the original specifications and do not substitute them arbitrarily.
