The sheath material directly affects the service life of the electric heater in a specific medium. Carbon steel sheaths are suitable for weakly corrosive media such as neutral water and mineral oil, with lower cost; 304 stainless steel can handle weak acid and alkali environments and some organic solvents; 316L stainless steel is suitable for occasions with high chloride ion content, such as certain chemical reactor jacket heating. If the medium is a strong acid or strong alkali, titanium or PTFE sheaths should be selected. Design and selection personnel need to make a comprehensive judgment based on medium composition, concentration, and temperature, and may request material compatibility data from suppliers when necessary.
Surface load refers to the electrical power carried per unit area of the sheath, in W/cm². Excessive load accelerates sheath oxidation and medium coking, while too low a load results in insufficient heating efficiency. For static air heating, it is recommended that the surface load not exceed 2.5 W/cm²; water heating can be controlled at 4–6 W/cm²; oil heating should preferably be 1.5–2.5 W/cm². The DJR-18 sheathed electric heater adopts a low surface load design, and the sheath temperature is controllable under rated power, making it suitable for long-term continuous operation in heat tracing and insulation scenarios.
Electrical interfaces usually come in two forms: threaded and flanged. Threaded installation is suitable for medium and small power applications and tanks with thinner walls, commonly using G1" and G1¼" pipe threads; flanged installation is suitable for high-power conditions or those requiring frequent disassembly, and the flange specifications must match the equipment interface. Mechanically, the insertion depth must be confirmed to ensure that the heating section is fully immersed in the medium to avoid dry burning. The junction box should be kept away from high-temperature areas, and the protection rating should be selected as IP54 or IP65 according to the on-site environment.
Power configuration depends on medium mass, specific heat capacity, heating time, and heat loss. For preliminary estimation, design and selection personnel can use the empirical formula: Power (kW) = medium mass (kg) × specific heat capacity (kJ/kg·°C) × temperature difference (°C) / (heating time (s) × efficiency). Efficiency is generally taken as 0.8–0.9. For insulation scenarios with heat loss, an additional 20%–30% margin must be added. The DJR-18 sheathed electric heater offers multiple power options to suit heat tracing needs for tanks and pipelines of different volumes.
Regularly check the sheath surface for scaling, corrosion, or mechanical damage. When scaling is severe, shut down and clean to avoid local overheating. Measure insulation resistance; in the cold state it should not be lower than 1 MΩ. If it is lower than this value, investigate moisture in the junction box or aging of the insulation layer. Check whether the wiring terminals are loose to prevent excessive contact resistance from causing heat. For electric heaters in long-term operation, it is recommended to conduct a comprehensive inspection every quarter and record the operating current, comparing it with the rated value to judge the condition of the element.
