The production of valves is a complex and simple process. The production cycle of ordinary valves, such as gate valves, ball valves, cut-off valves, butterfly valves and check valves, is generally three days. The production and manufacture of valves must be tested by various performance tests, the most important of which is test pressure. Pressure test is to test whether the pressure value that the valve can bear is in line with the production requirements. The general valve pressure test must comply with the following principles and matters needing attention:

(1) normally, valves are not tested for strength. However, strength tests should be made after the body and bonnet or corroded damaged valve bodies and bonnets are repaired. For the safety valve, its constant pressure and backseat pressure and other tests shall conform to the specifications and relevant regulations.

(2) valve installation shall be tested for strength and tightness. Low pressure valve spot check 20%, if unqualified should be 100% of the check; medium and high pressure valves should be 100% of the inspection.

(3) when testing, valve installation should be in the direction of easy inspection.

(4) valves with welded connections can be tested with conical seals or O ring seals when the test fails.

(5) eliminate the valve's air as much as possible during the hydraulic test.

(6) the pressure should be increased gradually during the test, and no sudden and sudden supercharging will be allowed.

(7) strength test and sealing test duration are generally 2 to 3min. Important and special valves should be 5min. The test time of the small caliber valve can be correspondingly shorter, and the test time of the large caliber valve can be correspondingly longer. During the test, if there is doubt, the test time can be extended. No sweat or leakage can be allowed on valve body and valve cover during strength test. Sealing test, general valve only once, safety valve, high pressure valve and other valve to be two times. In the test, minor leakage is allowed for low pressure, large diameter unimportant valves and valves with specified percolation, and the requirements for leakage should be carried out in accordance with the requirements of general valves, power station valves, marine valves and other valves.

(8) throttle valve is not closed for sealing test, but strength test and tightness test of filler and gasket should be carried out.

(9) in the test pressure, the closing force of the valve is only allowed to close one person's normal physical strength; no lever, such as a torque wrench (except the torque wrench), is allowed to be closed when the diameter of the handwheel is greater than that of 320mm.

(10) valve with upper seal should be removed and sealed for sealing test. When gas is used for testing, water is checked in the stuffing box. When packing tightness test is not allowed, the sealing is in a tight position.

(11) valves with actuating devices are tested for sealing when they are tested. For manual driving devices, we should also carry out the sealing test with the closing valve.

(12) the bypass valve installed on the main valve after strength test and sealing test, strength and sealing test in the main valve; when the main valve closes are opened, it should also be opened.

(13) when the cast iron valve is strength tested, the copper hammer is used to tap the valve body and the valve cover to check whether there is any leakage.

(14) when the valve is tested, other valves are not allowed to grease the sealing surface except for the regulation of the stopcock which allows the sealing surface to be oiled.

(15) when the valve is pressed, the compression force of the blind plate should not be too large, so as