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Valve pressure test should comply with the 16 principles and precautions


Valve production is a complex and simple process, the production of ordinary valves such as gate valves, ball valves, globe valves, butterfly valves, check valve production cycle is generally three days, the production of manufactured valves must go through a variety of performance testing, one of the most important test is pressure test. Pressure test is to test whether the pressure value that the valve can withstand meets the requirements of production regulations. General valve pressure test must comply with the following principles and precautions:


(1) Under normal circumstances, the valve does not have a strength test, but the valve body and bonnet after repair or corrosion damage of the valve body and bonnet should be strength test. For the safety valve, the constant pressure and back seat pressure and other tests shall comply with the specifications and relevant regulations.


(2) The strength and tightness test shall be made for the installation of the valve. Low pressure valve spot check 20%, such as 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) welding connection form of the valve, with blind plate pressure test can not be conical seal or O-ring seal pressure test.


(5) the hydraulic test when the valve air as far as possible to exclude.


(6) During the test, the pressure should be gradually increased, and sharp or sudden pressurization is not allowed.


(7) The duration of strength test and tightness test is generally 2-3min, and important and special valves should last 5min. Small diameter valve test time can be correspondingly shorter, large diameter valve test time can be correspondingly longer. During the test, if there is any doubt, the test time can be extended. During the strength test, the valve body and bonnet are not allowed to sweat or leak. Sealing test, the general valve only once, safety valve, high pressure valve and other raw valves need to be carried out twice. During the test, small amount of leakage is allowed for unimportant valves with low pressure and large diameter and valves with stipulated leakage; due to different requirements for general valves, power station valves, marine valves and other valves, the leakage requirements shall be implemented according to relevant regulations.


(8) The throttle valve shall not be tested for the tightness of the closing parts, but shall be tested for the strength and the tightness of the packing and gasket.


(9) During the pressure test, the valve closing force only allows one person's normal physical strength to close; Do not use tools such as levers to apply force (except torque wrenches). When the diameter of the handwheel is greater than 320mm, two people are allowed to close together.


(10) The valve with upper seal should take out the packing for sealing test. After the upper seal is closed, check for leakage. When testing with gas, check with water in the stuffing box. When the packing tightness test is carried out, the upper seal is not allowed to be in a tight position.


(11) For valves with driving devices, the sealing test shall be conducted by closing the valves with driving devices. For the manual driving device, the sealing test of the valve with dynamic closing shall also be carried out.


(12) strength test and sealing test installed on the main valve after the bypass valve, the main valve strength and sealing test; the main valve closed parts open, should also be opened.


(13) cast iron valve strength test, the application of copper hammer tap the valve body and valve cover, check whether there is leakage.


(14) valve test, in addition to the plug valve has provisions to allow the sealing surface oiling, other valves are not allowed in the sealing surface oiling test.


(15) when the valve pressure test, 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 effect (if the cast iron valve is pressed too tightly, it will be damaged).


(16) After the valve pressure test is completed, the water in the valve should be drained and wiped clean in time, and test records should be made.