What is the expansion of the tube body of an electric heating tube?
Tube body expansion means that after the electric heating tube is transferred at high temperature or energized, the pipe diameter becomes significantly thicker due to heating, and the normal pipe diameter cannot be restored after cooling, and even the pipe body bursts.
Example: Analysis of the causes of solid expansion of SUS304 stainless steel pipe pipe.
SUS304 stainless steel linear expansion coefficient α (10-6/°C) is related to temperature (°C), divided into 5 temperature segments:
(1) The linear expansion coefficient is 16.0 at 20~100 °C;
(2) The linear expansion coefficient is 16.8 at 20~200 °C;
(3) The linear expansion coefficient is 17.5 at 20~300 °C;
(4) The linear expansion coefficient is 18.1 at 20~400 °C;
(5) The linear expansion coefficient is 19.0 at 20~800 °C.
The pipe diameter expansion calculation formula of stainless steel pipe is
∆d=α×d0×（t1-t0）
where ∆d --- diameter expansion, mm;
α---304 stainless steel coefficient of linear expansion;
d0--- initial tube diameter, mm;
t0 an initial temperature, °C;
t a change in temperature, °C.
When the electric heating tube with a pipe diameter of 6.6mm is energized to reach the working temperature, the temperature of the tube surface can reach about 800 °C, and the corresponding parameters are substituted into the formula
∆d=19.0×10-6×6.6× (800-20)=0.097812mm
According to this calculation result, when the surface temperature of the tube reaches 800 °C, if it is a SUS304 pipe, it is normal for the pipe diameter to expand from 6.6mm to about 6.7mm. However, if it is not a pure SUS304 pipe, containing metal elements with a high coefficient of linear expansion, then there will be greater expansion, and even expand the metal pipe, and after dissection, it will be found that the pipe wall and the insulation layer of magnesium oxide have a clear gap. The quality of the pipe is unqualified, the wall thickness is uneven, the weld of the weld pipe has impurities, there are virtual welding, missing welding joints, etc., and it cannot withstand the heat expansion after heating, resulting in the expansion and bursting of the pipe body.
