The factory quality inspection of valve products should be carried out in accordance with the standards of relevant countries and industry standards. If relevant certificates are required, please indicate it when placing an order. Relevant fees will be charged according to the content of the test.
1 The factory inspection of valves usually includes the following three contents:
● Check whether the material, blank, machining and assembly of the valve meet the technical standards;
● Performance test: The basic performance of the valve includes five aspects: strength, sealing, flow resistance, action and service life. Strength test and sealing performance test must be carried out before the valve product leaves the factory. For some particularly important valves, samples should be drawn from the batch for performance tests in terms of flow resistance, action and service life. For safety valves, opening pressure, return seat pressure and displacement tests should also be carried out; for pressure reducing valves, sensitivity tests should be carried out; for steam traps, drainage tests should be carried out;
● Check whether the markings and identification spray paint, packaging and other aspects meet the relevant regulations, and whether the technical documents such as product certificates and product instructions are complete.
● Dimension inspection: Control the connection end size and the distance between the surfaces.
2 Introduction to important inspection items during the manufacturing process
●Chemical composition
Before casting, each furnace is subjected to a spectrometer composition analysis, and casting is performed only when the composition is qualified
●Metallography, mechanical performance parameters, hardness
◆After heat treatment (solution treatment for austenitic stainless steel CF8, CF8M, CF3M, etc.; normalizing treatment for carbon steel), metallographic analysis is performed, and metallographic photos are retained; unqualified products will not be transferred
◆During casting, each furnace has 2 standard test bars and 2 test pieces with the furnace (with the same furnace number as the products in the same furnace for traceability control). After heat treatment:
①Take one of the test bars and use a tensile testing machine to perform a tensile test to obtain mechanical performance related parameters: tensile strength, yield strength, elongation, and cross-sectional shrinkage
②Take one of the test pieces and use a Brinell hardness tester to perform a hardness test to obtain the hardness HB value; if necessary, cut it into an impact test piece and use an impact testing machine to perform an impact test to obtain the impact value
③The remaining 1 test bar and 1 test piece are used as spares, together with 1 test bar and test piece that have been tested and damaged Bundle together with the furnace material analysis test blocks of the same furnace, and put them in the test rod storage rack for two years
●Static test
After the valve is assembled and before the pressure test, in a dry state, use a multimeter to pass 12 volts of DC to test the resistance. According to API608, the resistance is ≤10 ohms (Note: The fluid passes through the pipeline at high speed, and friction is easy to generate static electricity. Because the soft valve seat such as PTFE is an electrical insulator, the valve ball is insulated from the valve body pipeline, causing local static electricity to rise or concentrate, which is easy to be dangerous when encountering sparks. Therefore, there must be a conductive design of an anti-static concentration device. API608 stipulates that the conductor resistance between the valve body and the valve stem must be less than 10Ω)
●Torque value
After the valve is tested with 6Kg/cm2 air pressure, a torque test is performed with a torque meter in a clean and oil-free state to obtain the torque value of the valve
●Life test
For each new product developed, or the structural dimensions of the valve body, valve cover, valve seat, valve stem and its stuffing box are changed, or the material of the valve seat and stuffing is changed, a life test machine will be used to perform a life test