The port of the heating tube is not completely sealed. It is placed in a relatively humid environment for a long time. The magnesium oxide powder in the heating tube absorbs moisture and is damp, because the magnesium oxide powder conducts heat conduction in the heating tube. The electric heating tube does not heat up.
1. Measure the electric heating tube with an electric resistance meter to see if there is any resistance value, and it is not broken;
2. If there is a resistance value, then look at the leakage current. Now measure the insulation resistance value with a megohmmeter (insulation resistance meter). (The larger the insulation resistance value, the better the insulation.) If the insulation resistance value is relatively small, it indicates that the magnesium oxide powder in the electric heating tube may be damp and the insulation of the electric heating tube becomes weak!