What is difference between destructive and non destructive test of welding ?

Non- destructive tests

In order to guaranty the quality of a welded structure, it is indispensable to know what welding defects may or may not exist in the welds. For this purpose, a welded structure could be examined by using a destructive test after fabrication; however, the tested structure becomes out of use if it is fractured by the test.

Therefore, destructive tests are conducted with test specimens, not with a product (except for the sampling test for small products).

Since finished products should never be fractured by a test, it is important to examine the soundness of the welds of the products without breaking them. For this purpose, Non destructive tests are conducted.