Knowledge

16 principles and precautions to be observed in valve pressure testing



The production of valves is a complicated and simple process. The production period of ordinary valves such as gate valves, ball valves, globe valves, butterfly valves and check valves is generally within three days. The valves produced must undergo various performance tests. The most important test is test pressure. The test pressure is to test whether the pressure value that the valve can bear meets the requirements of the production regulations. The general valve test pressure must comply with the following principles and precautions:

(1) Under normal circumstances, the valve shall not be subjected to strength tests. However, after the repair, the valve body and valve cover or corrosion damage of the valve body and valve cover shall be tested for strength. For safety valves, their constant pressure and seatback pressure and other tests shall comply with the specifications of their instructions and related procedures.

(2) The valve installation should be tested for strength and tightness. Low-pressure valve checks 20%, if unqualified should be 100% inspection; medium and high pressure valves should be 100% inspection.

(3) During the test, the valve installation position should be in the direction of easy inspection.

(4) Valves in the form of welded joints may be tested by taper seals or O-ring seals when the pressure test is not possible with a sampan plate.

(5) The valve air should be excluded as much as possible during the hydraulic test.

(6) The pressure during the test should be gradually increased and it is not allowed to pressurize suddenly and abruptly.

(7) The duration of the strength test and seal test is generally 2-3 minutes, and the important and special valves should last 5 minutes. Small-diameter valve test time can be correspondingly shorter, large-diameter valve test time can be longer. During the test, the test time can be extended if in doubt. In the strength test, the valve body and valve cover are not allowed to sweat or leak. Sealing test, the general valve only once, safety valve, high pressure valve and other raw materials need to be carried out twice. During the test, for the low-pressure, large-diameter non-essential valves and the valves that are permitted to leak, slight leaks are allowed; due to the requirements of general-purpose valves, power station valves, marine valves, and other valves, leakage requirements should be met. Follow relevant regulations.

(8) Throttle valves are not to be tested for sealability of the closure but strength tests and sealing tests at the packing and gaskets are to be made.

(9) In the pressure test, the closing force of the valve allows only one person's normal physical strength to close; it must not be forced by means of levers or the like (except torque wrenches). When the diameter of the handwheel is greater than 320 mm, the two are allowed to work together. shut down.

(10) The valve with the upper seal should be removed for the sealability test. After sealing the seal, check for leaks. When using the gas as a test, check the water in the stuffing box. For the packing sealability test, the upper seal is not allowed to be in the dense position.

(11) Where a valve is provided with a drive device, the use of a drive device to close the valve may be used to test the leak tightness of the valve. For manual drive devices, sealing tests should also be performed to close the valve.

(12) The bypass valve installed on the main valve after the strength test and sealability test shall be tested for strength and tightness at the main valve; the main valve closing member shall also be opened when it is opened.

(13) When the cast iron valve is tested for strength, apply a copper hammer and tap the valve body and valve cover to check for leakage.

(14) When the valve is tested, except for the provisions of the plug valve that allow the sealing surface to be oiled, other valves are not allowed to be oil-coated on the sealing surface.

(15) When the valve is pressure tested, the pressure of the blind plate on the valve should not be too large, so as to avoid deformation of the valve and affect the test results (If the cast iron valve is too tight, it will be damaged).

(16) After the pressure test of the valve is completed, the water in the valve shall be promptly removed and wiped clean, and a test record shall also be made.

Shanghai KS Flow Control Equipments Co.,Ltd is a valve manufacture with more than 30 years of valve manufacturing experience, which set up in 1984,specializing in Ball Valve,Gate Valve, Globe Valve, Check Valve and Butterfly Valve.

The company has advanced processing and manufacturing equipment, more than 70 CNC machine tools and machining centers, three spray lines. The company has established a complete physical and chemical laboratories, with direct reading spectrometer, spectrum alloy analyzer, helium mass spectrometer leak detector, electronic universal testing machine, coordinate measuring instrument, nondestructive testing, torque life test, high and low temperature comprehensive performance test device Etc.