Between the metal tube shell and the alloy heating wire, magnesium oxide powder is usually filled as the insulating medium. High-purity magnesium oxide has excellent alkali resistance and electrical insulation at high temperatures, and its thermal expansion coefficient and thermal conductivity are also very high. High-purity magnesium oxide used as a ceramic substrate has a thermal conductivity more than twice that of alumina, and the loss of electrolyte is only 1/10 of alumina. However, magnesium oxide powder has strong hygroscopicity. If the sealing of the electric heating tube is improperly processed or the modification of the magnesium oxide powder is insufficient, and the product is aging, the leakage current may easily exceed the standard.
The excellent performance of ceramic electric heating element in electrical insulation performance may provide a reference for the improvement of electric heating tube performance. For example, even if the silicon nitride ceramic heating element breaks due to improper use during use, the exposed heating wire section will immediately produce an insulating protective layer, forming a hydroelectric separation to eliminate hydroelectric contact and no leakage current. The leakage current in water under breaking conditions is not more than 10mA, which will not cause harm to human body. In addition, structural improvements can also obtain good insulation effects. The double-layer insulated single-head electric heating tube has a double-layer structure. Both the inner and outer layers adopt seamless metal tubes. The high-temperature magnesium oxide layer is filled between the inner and outer metal tubes, and the inner-layer metal tubes are filled with medium-temperature oxidation The magnesium layer, and the heating wire and the lead rod are embedded in the middle temperature magnesium oxide layer. When the outer layer of stainless steel pipe seeps water, the inner layer can also play a protective role, without affecting the normal operation of the heating pipe. In addition, due to the different temperature of the filled insulating material, the outer layer filled insulating material has better temperature resistance than the inner layer. Once the inner insulating layer is damaged, the outer layer can still maintain good insulation, thus making the heating tube have double insulation The protective measures can effectively prevent the bursting and leakage of the electric heating tube sheath.