Valve products are worth every penny, those with an advantage in price generally use their minds in terms of material, valve body size, and valve weight, which leads to the emergence of many ‘non-standard’ products on the market and low-quality products, such as 301 instead of 304, and even valves without materials Appear. It is recommended to consider prequalification first when purchasing, as the prices of different levels of manufacturers are quite different. Of course, we must also pay attention to comparing the quality and price of many companies to prevent the emergence of “profiteering”.
There are many methods for valve acceptance: the common ones are material inspection (sampling analysis, self-provided handheld spectrometer if possible), body weight (such as flange surface thickness, valve body thickness), disassembly inspection (check valve stem, sealing surface, etc.) , and pressure test.
Air Pressure Test
The test pressure of steel pipes and non-ferrous metal pipes under internal pressure should be 1.15 times the design pressure, and the test pressure of vacuum pipes should be 0.2MPa. When the design pressure of the pipeline is greater than 0.6MPa, it must be specified in the design documents or approved by the construction unit before the pressure test can be carried out with gas.
Leakage Test (Air tightness test)
Leakage test must be carried out for pipelines transporting highly toxic fluids, toxic fluids and flammable fluids. The leakage test shall be carried out in accordance with the following provisions:
- The leakage test shall be carried out after passing the pressure test. The test medium should be air.
- The leakage test pressure shall be the design pressure.
- The leakage test can be combined with the commissioning work and carried out at the same time.
- The leakage test should focus on checking the valve packing gland, flange or threaded connection, vent valve, exhaust valve, drain valve, etc. It is qualified if the foaming agent does not leak.
- Leakage test is not required for pipelines that have passed the air pressure test and have not been disassembled after the test.