During winter operation of heat transfer oil pipelines, the outlet temperature is often lower than the set value, while the heater surface temperature is relatively high. Upon disassembly and inspection, it was found that the heating wire inside the sheath had local overheating and the magnesium oxide powder had absorbed moisture. Such phenomena are mostly related to failure to calculate the surface heating power during model selection and mismatch between sheath material and medium. The SRY7-380/12 sheathed electric heater addresses the above working conditions by providing solutions in three aspects: sheath material, heating power density, and wiring method.
This model uses a No. 10 steel metal tube sheath, suitable for media such as heat transfer oil and asphalt. Compared with stainless steel sheaths, No. 10 steel has stable oxidation resistance during long-term operation in heat transfer oil, and the cost is controllable. The sheath surface is rust-proofed to reduce the risk of corrosion during storage and shutdown. For water or weakly corrosive media, a 304 stainless steel sheath can be customized; the specific choice needs to be calculated based on medium corrosiveness, working temperature, and sheath length.
Rated voltage 380V, rated power 12kW, three-phase star connection. The surface heating power is recommended not to exceed 3W/cm²; the actual value needs to be calculated according to medium flow rate, sheath length, and installation method. Under natural convection conditions of heat transfer oil, it is recommended to control the power density below 2.5W/cm² to reduce the tendency of coking on the sheath surface. When the element is used in air, it should be arranged in a crosswise and uniform manner to ensure that the passing air can be fully heated and to avoid local overheating.
The heater should be installed horizontally or vertically on the side wall of a pipeline or container, ensuring that the effective heating section of the sheath is fully immersed in the medium. The wiring cavity adopts a waterproof structure, suitable for outdoor or humid environments. The three-phase power supply needs to be equipped with a matching contactor and thermal relay, and it is recommended to add an over-temperature protection circuit. Regularly check the tightness of the wiring terminals and clean the sheath surface to maintain heat dissipation efficiency.
Suitable for auxiliary heating of heat transfer oil circulation systems, insulation of asphalt storage tanks, preheating of hydraulic oil, and other occasions. In sections where the outlet temperature of the heat transfer oil furnace is insufficient or pipeline heat loss is large, it can be used as a supplementary heating unit. Not suitable for strongly corrosive liquids or high-flow-rate scouring environments. When selecting, the medium name, working temperature, and installation space dimensions need to be provided.
