What is the function of sealing the electric heating tube?

The final step in making electric heating tubes is sealing. Many customers ask, what is the purpose of sealing electric heating tubes? Today, we'll explain.

In the structure of electric heating tubes, the space between the resistance wire and the metal sheath is tightly packed with a powdered filler (Feiyu normally uses high-temperature magnesium oxide powder). When dry and dense, this filler offers excellent thermal conductivity and insulation.

However, its performance drawback is its hygroscopicity. Once the filler material exposed at both ends of the tube absorbs moisture, its electrical insulation performance will be significantly reduced. This will cause electrical conductivity on the surface of the electric heating tube, posing a safety hazard.

Furthermore, when the magnesium oxide powder absorbs moisture, some of it will hydrate (especially in areas with poor or incomplete crystallization).

For electric heating tubes, the tube opening absorbs the most moisture and is the most prone to caking. Once caking occurs at the tube opening, it becomes more difficult for moisture absorbed into the filler material further away from the tube opening to escape. This can cause the electric heating tube to fail to recover its insulation even when powered on and generating heat. In fact, moisture in the tube can even vaporize and expand due to heat, causing the tube wall to bulge or crack.

Insulation decreases when exposed to moisture, and the coarsening of molecular particles after hydration affects the recovery of electrical insulation resistance. For these two reasons, the ends of the electric heating tube must be sealed.