What is a ball valve? Structure and operation of a ball valve
I. What is a ball valve?
Ball valve is a mechanical device that uses a rotation angle of less than or equal to 90 ° to open and close, regulating the flow of fluid in the pipeline system. The valve disc is a metal or plastic ball perforated through the center. The valve opens fully when the direction of the hole is parallel to the flow of fluid, and closes completely when the hole is perpendicular to the flow of fluid. The lever is mounted on the top of the valve shaft. We can open and close the valve by turning the lever to a 90 ° angle.
II. Structure and operation of ball valves.
The construction of a ball valve consists of the following main components:
• Body valve: usually made from copper, stainless steel, cast iron, steel ,which Is the main component to assemble the components of the ball valve.
• Ball : spherical and perforated with perforations, usually made of stainless steel with high hardness and low corrosion, which Is the main detail in the valve opening and closing. The ball is fixed by the sealing gasket and the shaft.
• Shaft of ball valve: the shaft is connecting and transmitting force from the lever,( handwheel), which makes the ball open or close.Ball Valve shafts are made of hard alloy that is less likely to corrode.
• Gaskets: including sealing gaskets for valve shafts, these gaskets and seals are made from teflong (PTFE) or bearing rubber or soft materials,which has the effect of sealing the components of the valve
• Handle lever:which is a part used to close, open the valve, made of steel or cast iron. The lever can be replaced by a gearbox andhandwheel when using valves in large-sized and high-pressure pipelines, pneumatic actuators (pneumatic control sets), pneumatic actuators. electricity (electric controller) when used in automation systems.
Depending on the fluid, pressure, temperature and purpose, we choose the material, the transmission device to suit the needs of use.
2. Operating principle
To know the principle of operation and construction of the ball valve we watch the video below.
II. Classification of ball valves.
Ball valves are divided into several categories based on the structure of the valve body, the ball and the moving part.
a. Full port type.
This type of ball hole has a diameter equal to the diameter of the tube, resulting in the minimum friction between fluid and valve, no pressure drop, does not affect the flow. But the valve design is bigger and more expensive, the valve is used when the maximum flow is needed. For example, in case of using high pressure and large flow to dredge, clean pipes.
b. Reduced port type
This form of hole of a ball is smaller than the diameter of the tube. In this case, the flow of the flow decreases, the velocity of the flow increases.
c. V port type.
The hole of the ball is a "V" shape. This allows the valve to open and close in a more controlled and consistent manner with linear flow. Can be used as a damper but not as accurate as balancing valves, globe valves and throttle valves.
Normally, the ball valve has only one upper pin (both shaft and latch) in this form, the valve has an additional bottom pin to better fix the ball, usually used in high pressure and large pipe.
f. Multi-port type
As the valve has many reclining (gates) and serves the purpose of dividing, diverting the flow, three-way ball valve is the most popular valve type today. There are two types of three-way ball valves: "T" and "L".
3. Some types of ball valve control.
a. Pneumatic control ball valve.
This type of ball valve is equipped with a pneumatic actuator (pneumatic controller), using compressed air to open and close the valve, so a high level of safety is often used for gas, gasoline and gas systems. burn ...
b. Electric ball valve
The ball valve is fitted with an electric actuator (electric controller), which uses an electric motor to open and close the valve. Commonly used on pipe systems and automation systems.
• Copper ball valves
• PVC ball valve
• Flanged ball valve
• 3-way ball valve
• Stainless steel ball valve 60
• Mini ball valve
• 2PC, 3PC ball valves
• Ball check valve
• Ball valve DN15, DN20, DN25, DN32. DN40, DN50, DN65, DN80, DN100, DN150.
III. Advantages and disadvantages of ball valves.
The great advantage of the ball valve is that it opens and closes quickly, the overall structure withstands high pressure, when opened completely does not cause much pressure and does not change the direction of the flow of fluid. Durable, still works well after many cycles of opening and closing and after long periods of non-use.
Easy to repair and replace, Withstands large pressures up to 1000 bar and temperatures up to 500 ° C, high corrosion resistance, depending on the design, material used and manufacturer. Low price.
The ball valve does not regulate the flow as expected as the throttle valve. Retain an amount of liquid in the hole when the valve is fully picked up and may cause the ball to crack when that portion of the liquid freezes.
It is unusable in the fluid flow due to the ball slip on the sealing gasket. After a period of working time, there are often round-shaped scratches surrounding the body of the ball leading to the valve not fully closed. Ball valve has a large torque compared to the general force due to the friction between the ball body and the sealing ring is quite large.