Hydraulic test
Products with a nominal inner diameter of 300mm or less are sampled once a quarter. Products with a nominal inner diameter of 350mm-1000mm are inspected once every six months. Products with a nominal internal diameter of 1200mm or more are inspected once a year. Two samples of one specification and one type are selected for each sampling. If one of the test results is unqualified, two more samples are taken from the product for retesting. If there is still one failure, the batch of products shall be judged as unqualified.
