How to correct acceptance of pneumatic valve products?

you get what you pay for pneumatic valve products, the price has the advantages of general tend to come from weight on the material, the size of the pneumatic valve, pneumatic valve, this leads to a lot of 'non-standard' of products on the market and low material, such as instead. Don't even strip quality pneumatic valves. Advice when purchasing first consider prequalification, price difference is bigger, different levels of manufacturer, of course, also have to pay attention to the price than three, mass than three prevent 'profits.
many ways of pneumatic valve acceptance: common is test material ( Sample analysis, conditional self-provided handheld spectrometer) , check body weight ( Such as the thickness of the flange surface, pneumatic valve body thickness) , the collapse of the checking ( Check the pneumatic valve stem and sealing surface, etc. ) And pressure test.
: pressure test: test under internal pressure steel and nonferrous metal pipe pressure shall be the design pressure. Times, vacuum pipe test pressure should be. MPa, when the pipeline pressure is greater than the design. MPa, there must be subject to consent by the construction unit, the design documents or available gas pressure experiment was carried out.
: leak test ( Air tightness test) :
poisonous liquid, toxic, flammable fluid pipeline leak test must be conducted. Appropriate USES air test medium.
leak test pressure shall be the design pressure.
the leakage test can be combined with work, together.
the leak test should be the key test of pneumatic valve stuffing box, flanged or threaded joints, pneumatic valve, pneumatic valve, exhaust drainage object completely valve, etc. Qualified for foaming agent inspection does not leak.
upon passing the pressure test, and after the test without remove the piping is not to leak test.