From Stainless Steel Ball Valves to Three-piece Ball Valves
1. Ball Valve Structure
A ball valve evolved from the plug valve. Its opening and closing parts are used as a sphere and the ball is turned 90 degrees around the axis of the stem to achieve the opening and closing effects.
2. Ball Valve Functions and Applications
Ball valves are mainly used in pipelines to cut off, distribute and change the flow direction of a medium. The valve with the designed V-shaped opening also enables a good flow regulation function.
Ball valve is not only simple in structure and good in sealing performance, but also performs well in a certain nominal range of small volume, light weight, less material consumption, small installation size, and small driving torque. On top of that, it is easy to operate, easy to achieve rapid opening and closing, and is one of the fastest developing valve varieties on the valve market in recent years. Ball valves are widely used especially in the developed countries such as USA, Britain, Japan, Germany, France, and Italy. There, the varieties and quantity of ball valves being used are still expanding. They continue to evolve to cope even better with high temperatures, high pressure, contain large port, high sealing, long life, and excellent regulating performance. Their reliability and other performance indicators have reached a high level and have partially replaced gate valves, stop valves and regulating valves.
With the development of the ball valve technology, it will be widely used in the foreseeable short time future. Especially in the oil and gas pipelines, refining and cracking units, and nuclear industry. In addition, ball valves will also become one of the leading valve types in large and medium-sized calibers and low- and medium-pressure fields in other industries.
3. Advantages of the Ball Valve Technology
- Ball valves have the lowest flow resistance (actually zero).
- Ball valves can be reliably applied to corrosive media and low boiling point liquids because they will not get stuck during operations (when/if there is no lubricant).
- Complete sealing can be achieved within a relatively large pressure and temperature range.
- Ball valves can realize fast opening and closing functions. The opening and closing time of some structures is only 0.05~0.1s to ensure that it can be used in the automation system of the test bench. There is no shock during the operation when opening and closing the valve quickly.
- The ball-shaped closing piece can be automatically positioned in position.
- The working medium is reliably sealed on both sides.
- When fully open and fully closed, the sealing surface of the ball and the valve seat is isolated from the medium. So the medium passing through the valve at high speed will not cause erosion of the sealing surface.
- With compact structure and light weight, the ball valve technology can be considered as the most reasonable valve structure for cryogenic media systems.
- The valve body is symmetrical, especially when the valve body structure is welded, which can well withstand the stress from the pipeline.
- The closing piece can withstand the high pressure difference when closing.
- The ball valve with a fully welded body can be directly buried in the ground, so that the internal parts of the valve are not corroded and the maximum service life can be up to 30 years. It is the most ideal valve for oil and natural gas pipelines.
4. Ball Valve Tightness
The most important seat sealing ring material for ball valves is polytetrafluoroethylene (PTFE), which is inert to almost all chemical substances and has a small friction coefficient, stable performance, excellent time durability, wide temperature application range and excellent tightness performance. However, the physical properties of PTFE, including high expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require the design of valve seat seals to focus on these characteristics. The plastic material of the valve seat seal also includes filled PTFE, nylon and many other materials. However, when the sealing material becomes hard, the reliability of the seal will be damaged, especially in the case of low pressure difference. In addition, synthetic rubber such as butyl rubber can also be used as a valve seat sealing material, but its applicable medium and temperature range drugs are limited. In addition, if the medium is not lubricated, the use of synthetic rubber is likely to jam the ball.
In order to meet the use requirements of industrial applications such as high temperature, high pressure, strong erosion, long life, etc., metal-sealed ball valves have been greatly developed in the past ten years. The structure of the ball valve has been continuously improved, with the emergence of full-welded body direct-buried ball valves, lifting ball valves, making ball valves more and more widely used in industrial fields such as long-distance pipelines, oil refining equipment, and large-diameter (3050mm), high-pressure (70MPa), wide temperature range (-196~815℃) ball valve, so that the technology of the ball valve reaches a whole new level.
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Besides several types of stainless steel ball valves, our manufacturing facilities in Shanghai and Taiwan also produce and export high quality and high-performance butterfly valves, safety valves, carbon steel valves, flanged swing check valves and a variety of other OEM valves on demand. Please visit our website and our valve product page for more information on our valves, Shanghai valve factory and Taiwan valve factory.
