How to check the sealing of the insulation layer of welded sealed straight stainless steel electric heating coil?

Check the sealing of the insulation layer of the welded sealed straight stainless steel electric heating coil by the following methods:
Appearance inspection
Directly observe the appearance of the weld to check whether the weld is continuous and uniform, and whether there are obvious defects such as pores, cracks, slag inclusions, etc. If the weld surface is smooth and flat, and there are no visible gaps or holes, it is preliminarily indicated that the sealing is good.
Check the connection between the insulation layer and the electric heating coil and other related components to see if there are gaps, detachment or missing sealing materials.
Pressure test
Air pressure test: Seal the electric heating coil in a closed space, pass a certain pressure of gas (such as air), and then use soap bubbles or special leak detection liquid to apply to the welding part and possible leak points. If bubbles are generated, it means there is a leak and the sealing is not good.
Water pressure test: For some electric heating coil systems that can withstand water pressure, they can be filled with water and a certain pressure can be applied to observe whether there is water seepage in the welding part and the surrounding area. The pressure of the water pressure test is generally determined according to the design requirements and use environment of the electric heating coil, which is usually slightly higher than the actual working pressure.
Helium mass spectrometry leak detection: This is a high-precision leak detection method suitable for occasions with high requirements for sealing. Place the electric heating coil in a sealed test chamber, fill it with a certain amount of helium, and then use a helium mass spectrometer leak detector to detect the concentration of helium in the surrounding environment. If helium leakage is detected, it means that there is a problem with the sealing of the insulation layer. This method can detect very small leaks with high sensitivity, but the equipment cost is relatively high.
Vacuum test: Place the electric heating coil in a vacuum environment and observe the changes in its internal pressure. If the pressure rises significantly within a certain period of time, it means that air or other gases have entered, that is, there is a sealing problem. A vacuum gauge can be used to accurately measure the pressure change to determine the quality of the sealing.