Valve products are worth a penny, the price advantage is generally from the material, body size, valve weight on the brains, which led to many 'non-standard' products on the market and low material, such as 301 304. Even a valve with no material appears. Proposing to purchase first considers prequalification. The price difference between manufacturers of different levels is relatively large. Of course, it is also necessary to pay attention to the ratio of the three companies and the quality ratio to prevent the occurrence of ‘profiteering’.
There are many methods of valve acceptance: the common one is the material inspection (sampling analysis, conditional self-prepared hand-held spectrometer), inspection body weight (such as flange surface thickness, valve body thickness), disassembly inspection (check valve stem, sealing surface, etc.) And test pressure.
1: Pneumatic test: The test pressure of the inner pressure steel pipe and non-ferrous metal pipe should be 1.15 times of the design pressure, and the test pressure of the vacuum pipe should be 0.2 MPa. When the design pressure of the pipeline is greater than 0.6 MPa, it must be specified in the design documents or With the consent of the construction unit, gas pressure tests can be performed.
2: Leak test (hermetic test):
Piping that transports highly toxic fluids, toxic fluids, and combustible fluids must be tested for leaks. Leakage tests should be conducted according to the following regulations:
Leakage test should be carried out after passing the pressure test. The test medium should use air.
Leakage test pressure should be design pressure.
Leakage tests can be combined with commissioning work.
Leakage tests should focus on inspection of valve stuffing boxes, flanges or threaded connections, vent valves, vent valves, and drain valves. The foaming agent does not leak as a qualified test.
The pipeline that passes the air pressure test and has not been disassembled after the test may not leak