1. When designing the structure of the weld joint, the joint must be welded thoroughly, and the harmful space for collecting dirt should be avoided. The correct welding method is to place the weld joint on the vacuum side and perform deep welding. Most of the wrong welds lead to dead space, so, some space should be blocked between the two weld joints and contain gas inside.
2. Weld joints should be welded well at one time to avoid causing dead space that does not support leak detection.
3. When the weld joint needs to be welded on both sides because of strength requirement, the internal weld joint should not leak. For the purpose of leak detection, drill plugs should be installed when performing external welds.
4. If the vessel needs to be structurally welded, the internal weld joints should not be continuous so that gas from any groove can be easily discharged, and the structural weld joint should not cross the sealed weld joint.
5. The welded components should be designed to make the maximum number of welds can be tested separately during the manufacturing stage and can be corrected before the final assembly.
6. The maximum allowable leak rate (for air) of welded seals is approximately 10-7 Pa·m3(s·m) on the weld length. If the leakage rate is relatively high, the weld joint should be worn off until the parent metal is exposed and then re-weld it. Remember not to perform two welds on place where the original leak occurred, because the repair welding is difficult to block the leak, and it is easy to produce stress to make new cracks.