Any NDT required for all castings should be confirmed with the factory before order or prior to production. Non-destructive testing (NDT) should be arranged for castings before machining (blank state), not for semi-finished or finished products. If do NDT with blank state, found that the casting defects can adopt the way of weld repair qualified, and then to do heat treatment, precision machining is can't to do the repair after treatment, the reason is that after weld repairs will produce deformation of castings, so even if the finished product to make Non -Destructive testing, qualified one time, of course, is the best, but finding defects can't do the repair, because after repair will affect the valve size accuracy, the valve will leak happen, or can not be assembled successfully, the valve finally useless, there is no way to solve.  Therefore, after the completion of the casting valve does not take non-destructive testing