The reason why the electric heating tube port should not be sealed

To prevent insulation damage from moisture absorption at both ends of electric heating tubes, they are typically sealed, also known as "sealing." However, sealing the ends of electric heating tubes is not recommended because they "breathe" during operation.

During the manufacturing process, when fused crystallized magnesium oxide or other fillers are placed between the tube and the heating wire, the space between them cannot be completely filled, resulting in trapped air. While this trapped air can be partially removed during subsequent steps such as shrinking, annealing, and bending, it is never completely eliminated.

When the electric heating tube is powered on and generates heat, the trapped air expands, generating significant pressure within the tube. The magnitude of this pressure depends on the amount of residual moisture and crystallized water within the tube, as well as the temperature. Relying on this strong pressure, some of the gas inside the electric heating tube will be released through the tube end, forming "exhalation". When the electric heating tube stops heating or cools down, the air remaining in the tube shrinks due to cooling, forming a negative pressure in the tube, or causing a partial vacuum. Relying on this negative pressure, some air will be sucked in from the outside through the tube end, forming "inhalation". The existence of this breathing process of tubular electric heating elements puts forward special requirements on the performance of the sealing material, that is, it needs to be sealed but not sealed, unless the residual air, moisture and crystal water content in the electric heating tube are ensured to be sufficiently small. When the maximum pressure is formed inside after heating, the metal shell has sufficient strength and will not burst under working conditions, otherwise, there will be huge potential danger.