In on-site operation and maintenance, after an over-temperature alarm occurs in the explosion-proof electric heater of a thermal oil furnace, can it be directly reset and restarted? The answer to this question depends on the degree of matching between the heater and the system in terms of electrical protection, temperature monitoring, and mechanical structure. The following explains the design features of the BDR-420 explosion-proof electric heater from several comparison dimensions.
Ordinary electric heating tubes, when subjected to a 50Hz, 1000V sinusoidal AC voltage for 1 minute at operating temperature, should have no breakdown and no internal flashover; under humid conditions, they must withstand a 50Hz, 1250V sinusoidal AC voltage for 1 minute, also with no breakdown and no internal flashover. The BDR-420 explosion-proof electric heater performs the same electrical strength test items in factory inspection, and the leakage current at operating temperature is controlled at ≤0.75mA. For on-site operation and maintenance personnel, this means that under abnormal working conditions such as water contained in the thermal oil or damp insulation, the equipment can still maintain a basic level of electrical isolation, reducing the probability of protection misoperation caused by increased leakage current.
When open heating elements are used in explosion-proof areas, the creepage distance between different polarities must be ≥3.0mm and the electrical clearance ≥2.5mm; between live parts and the metal enclosure, the creepage distance must be ≥1.0mm and the electrical clearance must be ≥1.0mm. The BDR-420 explosion-proof electric heater controls internal wiring spacing according to these requirements to avoid short circuits caused by dust accumulation, condensation, or bridging by metal foreign objects. Compared with ordinary industrial heaters, this design is more suitable for on-site environments where flammable gas or dust exists, but during operation and maintenance it is still necessary to regularly check the sealing condition of the wiring cavity, and the structure itself cannot be relied upon to replace daily inspections.
The internal temperature of the junction box of an explosion-proof electric heater is an operation and maintenance indicator that is easily overlooked. The BDR-420 explosion-proof electric heater can control the internal temperature of the junction box within three ranges: <65°C, <85°C, or <100°C, depending on the power configuration and heat dissipation conditions. Compared with heating equipment that does not perform temperature zoning management, this design reduces the risk of accelerated oxidation of terminal blocks due to long-term high temperatures. On-site operation and maintenance personnel should, based on the actual operating temperature of the thermal oil, confirm that the junction box temperature range matches the cable temperature rating, so as to avoid premature aging of the cable insulation layer.
In the mechanical strength test, the BDR-420 explosion-proof electric heater should have no damage specified by the standard after the specified test, and no live parts should be exposed; the cold-state insulation resistance is ≥200MΩ. Compared with split-type heating systems, this structure reduces on-site pipeline connection points and flange sealing surfaces, lowering the possibility of thermal oil leaking into the electrical cavity. However, during operation and maintenance, attention should still be paid to coking on the surface of the heating tube, because coking will change heat transfer efficiency and indirectly affect the judgment of cold-state insulation test values. The rated voltage is 380V or 400V, and the input power deviation is controlled within the range of +5% or -10%.
The BDR-420 explosion-proof electric heater is suitable for thermal oil circulation heating scenarios, and the power and junction box temperature range can be selected according to the system heat load. When comparing similar solutions on site, it is recommended to first check the three data items: electrical strength test records, measured creepage distance values, and cold-state insulation resistance, and then combine thermal oil quality and circulation flow rate to determine whether the heater is in a reasonable working range. The above technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
