The influence when the electric heating tube is not sealed at the port

In the structure of the electric heating tube, a dense powder-like filler is filled between the spiral heating wire and the metal tube shell. The filler has good thermal conductivity and insulation performance when it is dry and compact. But they all have different degrees of hygroscopicity. The filler exposed at both ends of the heating tube will greatly reduce its electrical insulation performance once it absorbs moisture. When the end of the heating tube is not sealed, the moisture absorption of the filler has a great influence on the insulation performance of the heating tube.

On the other hand, when magnesium oxide absorbs moisture, a part of magnesium oxide (especially the part with poor or imperfect crystalline state) will undergo hydration. The hydrated magnesium oxide will increase its molecular size and agglomerate. For the electric heating tube, the nozzle absorbs the most moisture, so the agglomeration is also serious. Once the nozzle is agglomerated, the moisture absorbed by the filler deeper from the nozzle is more difficult to discharge, so that the electric heating tube cannot restore the insulation when it is energized and heats itself, and even the water in the heating tube is heated and vaporized and expanded. The wall of the false heating tube is protruding and bursting.

The insulation decreases when wet, and the molecular size increases after hydration affects the recovery of the insulation resistance of the heating tube. For these two points, the electric heating tube needs to be sealed at the port.