1. Casting quality
The shape and size of the castings should comply with the requirements of the technical drawings or the requirements of the purchaser. The minimum wall thickness, structural length deviation, and gate wear displacement allowance of each part of the valve must not be less than the requirements of the relevant technical standards or product drawings of the product. There should be no cracks, cold shuts, sand inclusions, pores and other defects on the surface of the valve and the finished pressure shell of the valve. The sand, gates, risers and oxide scale on the surface of the casting should be removed. The typeface should be clear. The chemical composition and mechanical properties of castings are in accordance with the requirements of GB/T 12225, GB/T 12226, GB/T 12227, GB/T 12229, and GB/T 12230.
2. Test pressure
The pressure test is the most basic test for valves. Each valve needs to undergo a pressure test before leaving the factory. The test pressure and duration are in accordance with the GB/T13927 standard. The test items include shell test and sealing test. When the valve has an upper sealing structure, an upper sealing test is also required. During the test, no external force shall be applied to the valve that may affect the test results. The test pressure should remain unchanged during the holding and testing periods. When using liquid as the test medium, the air in the valve body should be eliminated. The valve should be closed in the manner given by the design. Relevant standards for testing include GB/T 13927, MSS SP61, ISO 5208, DIN 3230, AP1598, NFM 872401, ANSI B16134, JIS B2003, BS 5417 and BS 6755, etc.
