Before welding, the aluminum heating tube can withstand the voltage with 2.0KV/0.5MA. However, some of the pressure resistance after brazing can not pass 1.2KV/0.5MA.S, which becomes a bad product. Except for the heating tube moisture absorption.There is another reason as below.
When the resistance of the heating tube is poor after brazing,it should test the insulation resistance of the heating tube firstly. If the insulation resistance is too small, less than 50MΩ, it means that the heating tube has absorbed moisture. When the insulation resistance is greater than 1000MΩ, take X-ray to check whether the heating wire and the lead rod are eccentric,
Reason analysis: The poor pressure resistance caused by the eccentricity of the heating wire cannot be detected before welding. Due to the high temperature thermal expansion and contraction during welding, the creepage distance may change, which eventually leads to poor pressure resistance.
Solution: If the equipment for making heating tube fashion powder is normal, the first inspection that is taking the X-ray to ensure that the heating wire is not eccentric.