Wenzhou Unique Valve Co., Ltd.
Dos and Don'ts for Valve Pressure Tests (Part One)
Dec 28, 2020
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The production cycle of common valves, such as gate valves, ball valves and butterfly valves, is generally three days. Various performance tests shall be done for the manufactured valves. And the most important test is the pressure test. The pressure test refers to whether the pressure value that the valve can bear meets the production requirements. The following are some dos and don'ts for pressure tests of valves.
(1) Under normal circumstances, the valve shall not be tested for strength, but the valve body and the bonnet shall be tested after repair and corrosion damage. For safety valves, constant pressure tests, reseating pressure tests and other tests shall comply with the specifications and relevant regulations.
(2) Before installation, the valve shall be tested for strength and tightness. 20 percent of low-pressure valves shall be randomly inspected, and if they are unqualified, all shall be inspected. All middle and high pressure valves shall be checked.
(3) During the test, the valve should be installed in a position where it is easy to be checked.
(4) For valves with welded connections, if their pressure tests can't be done with the blind disk, cone seals or O-ring seals can be used for the test.
(5) The air in the valve shall be excluded as far as possible during the hydraulic pressure test.
(6) During the test, the pressure should be increased gradually. Sharp pressurization is not allowed.
(7) The time of the strength test and the leakage test generally last for 2 to 3 minutes, and the time of important and special valves should last for 5 minutes. The test time of small-diameter valves can be shorter and that of large-diameter valves can be longer. During the test, if in doubt, the test time can be extended. Sweating or leakage of the valve body and the bonnet is not allowed during the strength test. In general, the leakage test is only done once for valves. But it should be done twice for safety valves, high-pressure valves and other important valves. During the test, slight leakage is allowed for unimportant valves with low pressure and a large diameter and for valves allowed leakage. Because of the different requirements of general valves, power station valves, marine valves and other valves, their leakage requirements shall be implemented according to relevant regulations.
(1) Under normal circumstances, the valve shall not be tested for strength, but the valve body and the bonnet shall be tested after repair and corrosion damage. For safety valves, constant pressure tests, reseating pressure tests and other tests shall comply with the specifications and relevant regulations.
(2) Before installation, the valve shall be tested for strength and tightness. 20 percent of low-pressure valves shall be randomly inspected, and if they are unqualified, all shall be inspected. All middle and high pressure valves shall be checked.
(3) During the test, the valve should be installed in a position where it is easy to be checked.
(4) For valves with welded connections, if their pressure tests can't be done with the blind disk, cone seals or O-ring seals can be used for the test.
(5) The air in the valve shall be excluded as far as possible during the hydraulic pressure test.
(6) During the test, the pressure should be increased gradually. Sharp pressurization is not allowed.
(7) The time of the strength test and the leakage test generally last for 2 to 3 minutes, and the time of important and special valves should last for 5 minutes. The test time of small-diameter valves can be shorter and that of large-diameter valves can be longer. During the test, if in doubt, the test time can be extended. Sweating or leakage of the valve body and the bonnet is not allowed during the strength test. In general, the leakage test is only done once for valves. But it should be done twice for safety valves, high-pressure valves and other important valves. During the test, slight leakage is allowed for unimportant valves with low pressure and a large diameter and for valves allowed leakage. Because of the different requirements of general valves, power station valves, marine valves and other valves, their leakage requirements shall be implemented according to relevant regulations.
