Manufactured valves must undergo various performance tests, the most important of which is pressure testing. Pressure test is to test whether the pressure value that the valve can withstand meets the requirements of production regulations. In TWS, the soft seated butterfly valve, it must be carried high pressure seat tightness test. The pressure specified in 1.5 times of PN shall be applied to the test water.
Key words：Pressure Testing；Soft Seated Butterfly Valve; Pressure Seat Tightness Test
Generally, the pressure test of valves must comply with the following principles and precautions:
(1) In general, the valve is not subject to strength test, but the valve body and bonnet after repair or the valve body and bonnet with corrosion damage should be tested for strength. For the safety valve, its constant pressure, reseating pressure and other tests shall comply with the specifications of its instructions and relevant regulations.
(2) The strength and tightness test should be done before the valve is installed. 20% of the low-pressure valves are spot-checked, and 100% of them should be checked if they are unqualified; 100% of the medium and high-pressure valves should be checked.
(3) During the test, the installation position of the valve should be in the direction where inspection is easy.
(4) For valves in the form of welded connections, if the blind plate pressure test cannot be used, the conical seal or O-ring seal can be used for pressure test. (5) Exclude the valve air as much as possible during the hydraulic test.
(6) The pressure should be gradually increased during the test, and sharp and sudden pressurization is not allowed.
(7) The duration of the strength test and sealing type test is generally 2-3 minutes, and the important and special valves should last for 5 minutes. The test time for small-diameter valves can be correspondingly shorter, and the test time for large-diameter valves can be correspondingly longer. During the test, if in doubt, the test time can be extended. During the strength test, sweating or leakage of the valve body and bonnet is not allowed. The sealing test is only performed once for general valves, and twice for safety valves, high-pressure valves and other vital valves. During the test, a small amount of leakage is allowed for unimportant valves with low pressure and large diameter and valves with regulations to allow leakage; due to the different requirements for general valves, power station valves, marine valves and other valves, the leakage requirements should be as follows: Execute according to relevant regulations.
(8) The throttle valve is not subject to the tightness test of the closing part, but the strength test and the tightness test of the packing and gasket should be done. (9) During the pressure test, the closing force of the valve is only allowed to be closed by one person’s normal physical strength; it is not allowed to apply force with tools such as levers (except torque wrench). When the diameter of the handwheel is greater than or equal to 320mm, two people are allowed to work together. closure.
(10) For valves with an upper seal, the packing should be taken out for a tightness test. After the upper seal is closed, check for leakage. When using gas as a test, check with water in the stuffing box. When doing the packing tightness test, the upper seal is not allowed to be in the tight position.
(11) For any valve with a driving device, when testing its tightness, the driving device should be used to close the valve and carry out the tightness test. For the manually driven device, the sealing test of the manually closed valve shall also be carried out.
(12) After the strength test and tightness test, the bypass valve installed on the main valve shall be tested for strength and tightness at the main valve; when the closing part of the main valve is opened, it shall also be opened accordingly.
(13) During the strength test of cast iron valves, tap the valve body and valve cover with a copper bell to check for leakage.
(14) When the valve is tested, except for plug valves that allow the sealing surface to be oiled, other valves are not allowed to test the sealing surface with oil.
(15) During the pressure test of the valve, the pressing force of the blind plate on the valve should not be too large, so as to avoid deformation of the valve and affect the test effect (if the cast iron valve is pressed too tightly, it will be damaged).
(16) After the pressure test of the valve is completed, the accumulated water in the valve should be removed in time and wiped clean, and a test record should also be made.
In TWS Valve, regarding our main product, the soft seated butterfly valve, it must be carried high pressure seat tightness test. And the test medium are water or gas, and temperature of test medium is between 5℃~40℃.
And the following testing is tightness of shell and valve performance.
Its purpose is that the test shall confirm the leak tightness of the shell including operating mechanism sealing against internal pressure.
During the test procedure, we have to notice that the test fluid shall be water.
And the disc of the valve shall be in a partially open position.The end connections of the valve shall be blanked off and all cavities filled with the test water. The pressure specified in 1.5 times of PN shall be applied to the test water.
Post time: Apr-23-2023
