The ball valve is evolved from a cock. Its opening and closing member acts as a ball, which is opened and closed by rotating the ball 90 degrees around the axis of the valve stem. The ball valve is mainly used to cut, distribute and change the flow direction of the medium on the pipeline. The ball valve designed as a V-shaped opening also has a good flow regulation function.
The ball valve not only has a simple structure and good sealing performance, but also has a small volume, a light weight, a small material consumption, a small installation size, a small driving torque, a simple operation, and an easy opening and closing in a certain nominal diameter range. Developed one of the varieties of Zui's fast regulating valve for more than ten years...
First, the application of the ball valve:
Since ball valves typically use rubber, nylon, and Teflon as the seat seal material, their service temperature is limited by the material of the seat seal. The cut-off function of the ball valve is achieved by the metal balls being pressed against each other under the action of the medium (floating ball valve). The valve seat seal is deformed by elastic deformation in a local area under a certain contact pressure. This deformation can compensate for the manufacturing precision and surface roughness of the sphere and ensure the sealing performance of the ball valve. Since the valve seat seal of the ball valve is usually made of plastic, the fire resistance and fireproof of the ball valve should be considered in selecting the structure and performance of the ball valve, especially in the petroleum, chemical, metallurgical and other departments.
Second, the selection principle of the ball valve:
1. The main line for the transportation of oil and natural gas, the pipe that needs to be cleaned, and the underground pipe, the ball valve with full-diameter and all-welded structure; the ball valve buried in the ground and selected for full-diameter welding or flange connection ; branch pipe, flange connection, welded connection, full diameter or reduced diameter ball valve.
2. The conveying pipeline and storage equipment of the refined oil are selected from flanged ball valves.
3. On the pipeline of city gas and natural gas, use the floating ball valve with flange connection and internal thread connection...
The ball valve product is evolved from the plug valve. The ball valve consists of an integral ball as the valve opening and closing member (spool). The ball is rotated 90 degrees around the axis of the valve stem to achieve the opening and closing of the valve. The ball valve is mainly used to cut, distribute and change the flow direction of the medium on the conveying pipe. The ball valve designed as a V-shaped open valve core also has a good flow regulating function.
The ball valve not only has a simple structure and good sealing performance, but also has a small volume, a light weight, a small consumption of raw materials, a small installation size, a small driving torque, a simple operation, and an easy opening and closing in a certain nominal diameter range. One of the varieties of valve that has developed zui for more than ten years. The use of ball valves is very extensive, the variety and quantity of use are still increasing, and the development of high temperature, high pressure, large mouth, high sealing, long life, excellent regulation performance and multi-valve function, its Other performance indicators have reached a high level, and have partially replaced the use of gate valves, globe valves, and throttle valves. With the continuous development of ball valve technology, it will be more widely used in the foreseeable short-term, especially on oil and gas pipelines, refinery crackers and nuclear industry. In addition, in the large and medium-sized, medium and low pressure areas of other industries, ball valves will also become one of the leading valve types.
Third, the preparation of the ball valve before installation:
(1) The pipeline before and after the ball valve is ready. The front and rear pipes should be coaxial and the two flange sealing surfaces should be parallel. The pipe should be able to withstand the weight of the ball valve, otherwise the pipe must be equipped with appropriate support.
(2) Purge the front and rear lines of the valve to remove oil, welding slag and all other impurities from the pipe.
(3) Check the sign of the ball valve and find out that the ball valve is intact. The valve was fully opened and closed several times to confirm that it was working properly.
(4) Remove the protective parts on the connecting flanges at both ends of the ball valve.
(5) Check the valve hole to remove possible dirt and then clean the valve hole. Even small particles of foreign matter between the seat and the ball may damage the seat sealing surface.
Fourth, the ball valve installation:
(1) Install the valve on the pipeline. Any end of the valve can be mounted on the upstream end. Valves driven by the handle can be mounted anywhere on the pipe. However, ball valves with gearboxes or pneumatic drives should be mounted upright, ie on horizontal pipes, with the drive above the pipe.
(2) A gasket is installed between the valve flange and the pipeline flange according to the piping design requirements.
(3) The bolts on the flange should be tightened symmetrically, successively and evenly.
(4) Connect the pneumatic line (when using a pneumatic drive).
5. Inspection after installation of the ball valve:
(1) Operate the drive to open and close the ball valve several times, and it should be flexible and without stagnation, and confirm that it works normally.
(2) Check the sealing performance of the flange joint between the pipe and the ball valve according to the pipeline design requirements.
6. Airtightness test of ball valve: air tightness test on the removed ball valve
(1) Put the valve in a half open state. Seal the ends of the ball with a flanged cap with a fitting.
(2) Introduce the test medium to one end. The test medium is clean nitrogen or air. The other end of the pipe joint is blocked. After gradually increasing the pressure to 5.6 bar, close the intake valve to stop the intake.
(3) Turn the ball a few times and close the ball valve (operating the drive)
(4) Open the pipe joint plug at the other end (not introducing the test gas end) to reduce the pressure of the chamber to atmospheric pressure.
(5) Under the test pressure (5.6 bar), the pressure in the inlet chamber must not decrease for more than 5 minutes. The pressure gauge used should be 0.4 and the range is 10 bar.
(6) At the same time, use soapy water to check the external leakage of each connecting flange part and packing part, and there shall be no ever-increasing air bubbles.
(7) The test medium was then introduced from the other end and the above test was repeated.
(8) After passing the test, blow off the soapy water residue with compressed air. Remove the flange caps at both ends and remove the seal residue on the sealing surfaces at both ends of the ball valve. If any residue enters the valve hole, it should be removed and wiped clean.
Seven, ball valve online sealing test:
(1) It is ascertained that the shut-off valve on the upstream and downstream of the ball valve under test has been closed.
(2) Put the ball valve under test in a half-open state.
(3) Introduce the test medium to the pipe before the test ball valve. The test medium is cleaned and the nitrogen gas is gradually pressurized to 5.6 bar, then the intake valve is closed to stop the intake.
(4) Turn the ball a few times and then close the ball valve (operate the drive).
(5) Open the bleed valve on the pipe downstream of the ball valve under test to make the ball valve out of the mouth pressure to atmospheric pressure.
(6) Under the test pressure (5.6 bar), the inlet pressure should not drop within 15 min. The pressure gauge used should be 0.4 and the range is 10 bar.
(7) At the same time, use soapy water to check the external leakage of each connecting flange part and packing part, and there shall be no ever-increasing air bubbles.
(8) The test medium is then introduced into the pipe behind the ball valve to be tested, and the above test is repeated.
(9) After passing the test, blow off the soapy water residue with compressed air.
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