Valve production is a complex and simple process, the production of ordinary valves such as gate valve, ball valve, butterfly valve production cycle is generally three days, the production of good valves must go through a variety of performance tests, one of the most important test is Pressure test. Pressure test is the pressure valve in Sichuan can withstand the requirements of the production requirements, the general pressure test valve must comply with the following principles and precautions:
(1) Under normal circumstances, the valve does not make strength test, but after repair, the valve body and valve cover or corrosion damage valve body and valve cover shall be subjected to strength test. For safety valves, the constant pressure and back pressure and other tests should be consistent with the instructions and the relevant regulations.
(2) Akira valve installation should be made for strength and tightness test. Low-pressure valve checks 20%, such as failure should be 100% of the inspection; medium and high pressure valves should be 100% inspection.
(3) During the test, the installation position of the valve should be in the direction of easy inspection.
(4) Valves of welded connection type may be pressure-tested with conical seal or O-ring seal when pressure test is not performed with shutters.
(5) When the hydraulic test will try to exclude the valve air.
(6) test pressure to be gradually increased, does not allow rapid, sudden pressure.
(7) strength test and sealing test duration is generally 2--3min, important and special valve should last 5min. Small-caliber valve test time can be shorter, large-caliber valve test time may be longer. During the test, the test time may be extended if in doubt. Strength test, do not allow body and bonnet sweating or leakage phenomenon. Sealing test, the general valve only once, safety valve, high-pressure valve and other live to be carried out twice the valve. The test, the low pressure, large diameter of the valve does not matter as well as the provisions of the valve allows leakage to allow a trace of leakage; due to the general valve, power station valves, marine valves and other valves require different leakage requirements According to the relevant provisions of the implementation.
(8) Throttle valves shall not be tested for the tightness of the closing parts, but shall be subjected to the strength test and the tightness test at the packing and Gasket.
(9) During the pressure test, the closing force of the valve only allows one person's normal physical strength to close; the force shall not be applied by means of a lever or the like (except the torque wrench); when the diameter of the hand wheel is greater than or equal to 320mm, shut down.
(10) Valves with airtightness shall be taken out of packing for sealing test, checked for leaks after sealing. When testing with gas, check the water in the stuffing box. For packing sealing test, the upper seal is not allowed to be in close position.
(11) Where a valve with a driving device is used, the driving device shall be used to close the valve to seal the sealing test when testing its sealing property. On the manual drive, should also be closed with the valve seal test.
(12) After the strength test and the tightness test, a bypass valve fitted to the main valve 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) cast iron valve strength test, the use of copper hammer tap valve body and bonnet, check whether there is leakage.
(14) When the valve is tested, other valves shall not be allowed to be lubricated on the sealing surface unless the stopcock valve is specified to allow the sealing surface to be oiled.
(15) when the valve pressure test, the blind pressure on the valve should not be too large, so as to avoid valve deformation, affecting the test results (cast iron valve too tight if pressed, but also damaged).
(16) Valve pressure test is completed, the valve should be promptly ruled out water and wipe clean, should also make test records.
Valve pressure test is the factory must be carried out, which can ensure the safe operation of the valve. Valve manufacturers to remind the pressure test to protect their own safety, in recent years, the pressure test a lot of safety accidents, should pay attention to vigilance.
STAINLESS STEEL PRODUCTS
Stainless steel is a corrosion resistant steel alloy with a minimum of 10% chromium. There are different grades and surface finishes of stainless steel produced to accommodate the environment in which the material will be implemented. Unlike carbon steel, stainless steel does not rust when exposed to air and moisture due to the sufficient amount of chromium present. The chromium creates an invisible passive film of chromium oxide that will not let oxygen attack the surface and prevents rusting of the iron base.
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