In reactors, storage tanks, pipeline heat tracing, and water tank heating systems, flange-type electric heating tubes weld or expand multiple metal tubular heating elements onto a flange plate, connecting to the container opening via the flange to achieve centralized heating. A chemical enterprise storage tank with a volume of 8m³, using heat transfer oil as the medium, requires a heating rate of ≤2℃/min and an operating pressure of 0.6MPa. During design selection, flange specifications, power density, and medium characteristics must be comprehensively considered.
Compared with threaded heating tubes, the flange-type structure can carry more heating elements, with a single unit power reaching tens of kilowatts, suitable for high-power centralized installation. Threaded types are limited by interface size, typically with a single tube power not exceeding 9kW, offering easy replacement but limited expansion space. Immersion-type electric heaters are mostly used for online heating of flowing media, with flexible installation methods, but in high-viscosity or particle-containing media, the surface heat load distribution is uneven. Flange-type can use multiple U-shaped or W-shaped tubes to disperse the heat load and extend service life. During design selection, if the container opening size allows and greater heating power is required, the flange-type solution is more advantageous, but attention must be paid to matching the flange sealing surface form with medium corrosiveness.
Metal tubular heating elements can be customized for power, voltage, and expanded length according to usage conditions. Common voltages are 220V or 380V, and the power density is recommended not to exceed 3W/cm² (for heat transfer oil conditions). Flange standards can be selected from GB/T 9119, HG/T 20592, etc. The nominal pressure must cover the system's maximum operating pressure. Materials are commonly carbon steel, 304, or 316L stainless steel. The protection level is usually IP54 or IP65. The junction box forms are divided into ordinary and explosion-proof types, with the explosion-proof grade selected according to the environmental area. Design and selection personnel should combine medium temperature, flow rate, container volume, and insulation conditions to calculate the required total power, avoiding power overload leading to excessively high surface temperatures.
During installation, ensure that the heating elements are fully immersed in the medium to avoid dry burning. Flange bolts should be tightened evenly in a diagonal pattern to prevent uneven pressure on the sealing gasket. Regularly check the insulation resistance, which is recommended not to be lower than 1MΩ. If below this value, investigate whether the junction box is damp or the element insulation is aged. When replacing elements, record the original flange specifications, power, voltage, and arrangement to ensure spare parts interchangeability.
