Foreword: Ball valve came out in the 1950s. With the rapid development of science and technology, the continuous improvement of production technology and product structure, it has rapidly developed into a major valve type in just 50 years. In developed western countries, the use of ball valves is increasing year by year.
The ball valve is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. It only needs to be rotated 90 degrees and a small torque can be closed tightly. The ball valve is most suitable for use as a switch and a shut-off valve.
Since the ball valve usually uses rubber, nylon and polytetrafluoroethylene as the material of the seat seal, its operating temperature is limited by the material of the seat seal. The cut-off function of the ball valve is accomplished by pressing the metal ball against the plastic valve seat under the action of the medium (floating ball valve). Under the action of a certain contact pressure, the valve seat sealing ring undergoes elastic-plastic deformation in local areas. This deformation can compensate the manufacturing accuracy and surface roughness of the ball, and ensure the sealing performance of the ball valve.
And because the valve seat sealing ring of the ball valve is usually made of plastic, when choosing the structure and performance of the ball valve, the fire resistance and fire resistance of the ball valve should be considered, especially in the petroleum, chemical, metallurgical and other departments, in flammable and explosive media. If ball valves are used in the equipment and pipeline systems, more attention should be paid to fire resistance and fire protection.
Ball valve features
1. Has the lowest flow resistance (actually zero). 2. It will not get stuck when working without lubricant, so it can be reliably applied to corrosive media and low boiling point liquids. 3. It can achieve 100% sealing in a large pressure and temperature range. 4. It can realize ultra-fast opening and closing, and the opening and closing time of some structures is only 0.05~0.1s, so as to ensure that it can be used in the automation system of the test bench. When the valve is opened and closed quickly, there is no shock in operation. 5. The spherical closure can be automatically positioned in position. 6. The working medium is reliably sealed on both sides. 7. When fully open and fully closed, the sealing surfaces of the ball and valve seat are isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface. 8. With compact structure and light weight, it can be considered as the most reasonable valve structure suitable for low temperature medium system. 9. The valve body is symmetrical, especially when the valve body structure is welded, which can well withstand the stress from the pipeline. 10. The closing piece can withstand the high pressure difference when closing. 11. The ball valve with fully welded valve body can be directly buried in the ground, so that the valve internals are not eroded, and the maximum service life can reach 30 years. It is the most ideal valve for oil and natural gas pipelines.
Application of ball valve
The many unique characteristics of ball valves determine that the use of ball valves is relatively wide. Usually, in two-position adjustment, strict sealing performance, mud, wear, shrinking channels, rapid opening and closing actions (1/4 turn opening and closing), high pressure cut-off ( Ball valves are recommended for pipeline systems with large pressure difference), low noise, cavitation and gasification, a small amount of leakage to the atmosphere, small operating torque, and small fluid resistance.
The ball valve is also suitable for the pipeline system of light structure, low pressure cut-off (small pressure difference) and corrosive medium. Ball valves can also be used in cryogenic (cryogenic) installations and piping systems. In the oxygen pipeline system in the metallurgical industry, ball valves that have undergone strict degreasing treatment are required. When the main line in the oil pipeline and the gas pipeline needs to be buried underground, a full-bore welded ball valve should be used. When the adjustment performance is required, a ball valve with a special structure with a V-shaped opening should be selected. In petroleum, petrochemical, chemical, electric power, and urban construction, metal-to-metal sealing ball valves can be selected for pipeline systems with a working temperature above 200 degrees.
Application principle of ball valve
Oil and natural gas transmission main lines, pipelines that need to be cleaned, and buried underground, choose a ball valve with all-passage and all-welded structure; buried in the ground, choose a ball valve with all-passage welded connection or flange connection; branch pipe , choose flange connection, welded connection, full through or reduced diameter ball valve. The pipelines and storage equipment of refined oil use flanged ball valves. On the pipeline of city gas and natural gas, the floating ball valve with flange connection and internal thread connection is selected. In the oxygen pipeline system in the metallurgical system, it is advisable to use a fixed ball valve that has undergone strict degreasing treatment and is flanged. In the pipeline system and device of low temperature medium, the low temperature ball valve with valve cover should be selected. On the pipeline system of the catalytic cracking unit of the oil refining unit, the lifting rod type ball valve can be selected. In the devices and pipeline systems of corrosive media such as acid and alkali in chemical systems, all stainless steel ball valves made of austenitic stainless steel and PTFE as the valve seat sealing ring should be selected. Metal-to-metal sealing ball valves can be used in pipeline systems or devices of high temperature medium in metallurgical systems, power systems, petrochemical plants, and urban heating systems. When flow adjustment is required, a worm gear driven, pneumatic or electric regulating ball valve with V-shaped opening can be selected.
Summary: The use of ball valves is very extensive, the variety and quantity of use are still expanding, and they are developing in the direction of high pressure, high temperature, large diameter, high sealing performance, long life, excellent adjustment performance and multi-function of one valve. Its reliability and other The performance indicators have reached a high level, and have partially replaced gate valves, globe valves, and regulating valves. With the technical progress of ball valves, it will be more widely used in the foreseeable short term, especially in oil and gas pipelines, crackers in oil refining and in the nuclear industry. In addition, ball valves will also become one of the dominant valve types in the fields of large and medium caliber, medium and low pressures in other industries.
Post time: Apr-01-2022