1, the valve body internal and external surfaces have no sand holes, cracks and other defects.
2, the valve seat and the valve body joint is firm, the valve spool and the valve seat whether match, the sealing surface has no defects.
3, the valve stem and spool connection is flexible and reliable, the valve stem has no bending, threads have no damage, corrosion.
4, packing, gaskets, whether aging damage, whether the valve is flexible to open.
5, the valve body should have a nameplate, the valve body and the nameplate should include: manufacturer's name, the name of the valve, nominal pressure, nominal diameter and other identification.
6, the valve should be transported open and closed position in accordance with the following requirements:
(a) gate valves, globe valves, throttle valves, butterfly valves, bottom valves, regulating valves and other valves should be in full closed position.
(b) Plug valves, ball valves should be in full open position.
(c) Diaphragm valve should be in the closed position, do not close too tight to prevent damage to the diaphragm valve.
(d) Check valve flap should be closed and be fixed.
7, spring-loaded safety valves should have a seal, lever-type safety valves should have a heavy hammer positioning device.
8,Check valve flap or spool action should be flexible and accurate, no eccentricity, displacement or skew phenomenon.
9, rubber-lined, enamel-lined and plastic-lined valves should be flat and smooth inner surface, lining layer and the substrate combined firmly, without cracks, bubbles and other defects.
10, the flange sealing surface should meet the requirements of radial scratches.
11, the valve shall not have damage, lack of parts, corrosion, nameplate off and other phenomena, and the valve body shall not be dirty.
12, the valve should be protected at both ends of the protective cover, handle or handwheel operation should be flexible, there shall be no jams.
13, the valve quality certificate should contain the following content:
(a) the name of the manufacturer and factory date.
(b) product name, model and specifications.
(c) nominal pressure, nominal diameter, applicable media and applicable temperature.
(d) Based on the standards, test conclusions and test date.
(e) Factory number, inspector and responsible inspector's signature.
Valve can be regarded as a pressurised container, solid need to meet the requirements to withstand the pressure of the medium without leakage, so the valve body, bonnet and other parts of the blank should not have an impact on the strength of the cracks, loose pores, slag and other defects.
Strength test is generally carried out after assembly. The test is usually carried out at room temperature, in order to ensure the safety of use, the test pressure P is generally 1.25-1.5 times the nominal pressure PN. During the test, the valve is open, one end is closed, and the medium is injected and pressure is applied from the other end. Check the shell (body, cover) exposed surfaces, required in the specified test duration (generally not less than 10 minutes) within the no leakage, the valve strength test can be considered qualified. In order to ensure the reliability of the test, the strength test should be carried out before the valve is painted, with water as the medium should be the inner cavity of the air exhaust.