A ball valve is a device that controls the flow open or closed with a spherical valve and has two inlet and outlet ducts in its center. Ball valves are among the valves that are used to cut off and connect the flow with 90 degree rotation and the reasons for their use are their long life, high durability and very good and acceptable sealing. The function of these valves is to guide and regulate different fluids, and they do this by opening the ball that is located in the middle of them. In fact, it can be said that a ball valve or a valve is a kind of quarter-round valve that is used to cut off and connect the flow using the rotation of a spherical ball and opens and closes the flow path. Therefore, it is better to say that wing valves are valves with rotational motion. If the valve is open, the hole is in the direction of the flow, and if the hole is perpendicular to the flow path, the reason is that the valve is closed. Therefore, when the valve handle is in the direction of the path, it indicates that the valve is open, and when its handle is perpendicular to the flow path, it indicates that the valve is closed. The durability of these valves is very high and they are highly reliable even when not in use. The characteristics mentioned in ball valves have caused them to surpass other valves in many cases, including gate valves and spherical valves. The applications and features that exist in these valves have led to widespread industrial applications and can be used for pressures up to 1000 bar and temperatures up to 400 ° C. The characteristics mentioned in ball valves have caused them to surpass other valves in many cases, including gate valves and spherical valves. The applications and features that exist in these valves have led to widespread industrial applications and can be used for pressures up to 1000 bar and temperatures up to 400 ° C. The characteristics mentioned in ball valves have caused them to surpass other valves in many cases, including gate valves and spherical valves. The applications and features that exist in these valves have led to widespread industrial applications and can be used for pressures up to 1000 bar and temperatures up to 400 ° C.
When the position of the valve is open, ie the position indicator indicates that it is open, in this case, the valve ball hole is located along the pipeline path, and this causes the flow to pass through them.
When the indicator indicates the position of the valve is closed, the reason is that the valve is closed, and if the valve ball rotates 90 degrees, it means that its duct is perpendicular to the direction of flow and there is no possibility for the flow to pass through them. Does not exist.
These valves are simple shut-off devices that use a bullet to stop and start the fluid flow downstream of the valve. By rotating the valve stem, it rotates towards the opening position of the ball, and the hole that is installed in the middle of it is placed in the direction of fluid entry and exit, and as a result, the fluid passes through the valve. When the ball rotates so that its hole is perpendicular to the fluid path, the fluid flow stops. Most ball valves operate quickly and require a 90-degree rotation of the actuator lever to open or close the valve. When the ball is in the semi-open position, a turbulent flow occurs in the valve. This feature limits the use of the ball valve. Such valves should only be used in fully open or fully closed applications due to turbulence and friction currents in the semi-open state. These valves should not be used to control fluid flow.
Ball valves used in process systems may use different actuators for direct or remote control of the valve. The most common of these actuators are either manual or powered by a motor. Manual valves have a hand wheel or lever that connects either directly or via a gearbox to the valve stem, which opens or closes by moving the valve stem by a 90-degree arc. Valves controlled by a motor use a motor with less than one horsepower instead of a cart, which can also be controlled remotely. The operation of the motor actuator is exactly the same as that of the manual actuator. In most wing valves, valve operation occurs when the valve handle rotates 90 degrees. Some wing valves have actuators that act as solar gears.
Applications of ball valve
Ball valves are also used in water and sewage systems, ships, chemical industries, firefighting, automotive, textile, metal, plastic and pharmaceutical.
Ball valve structure
Ball valves are in the category of shut-off valves, and when they are half open, they face problems and suffer a lot of damage. The task of opening and closing the valve is the responsibility of the blocking member of the flow channel and its 90 degree movement is done by the valve stem. If the fluid passage through the pipeline area is smaller, it is called a Reduce Bore. In other words, the design inside the body and the size of the passageway is such that if it is open, it will cause a lot of pressure drop in the path. Also, if the same reduction in area in the flow channel is designed completely incorrectly, it will lead to turbulence and turbulence in the fluid flow. Now if the area of the fluid passage is equal to the area of the pipeline, it is called Full Bore.
Types of ball valves
Ball valves can be classified according to different criteria:
- In terms of design: Floating or flotation, Thronion and Double Block and Bleed or Double Block and Bleed
- Number of ports: Standard with 2 ports that have one input and one output and 3-way that has one input and 2 outputs or vice versa.
- Duct size: Full and V-shaped duct
- Body assembly: integrated and 2 or 3 pieces
- Ball entrance: side entrance or upper entrance
- Type of seat: metal or soft
Floating or floating ball valves
In this type of valve, the ball is suspended in the liquid in the flow state. The shaft is located on top of the ball, which allows the ball valve to be changed from open to closed by a quarter-circular motion or 90 degrees. This is a very light and economical design with a duct size of up to 10 inches, which can not be safe and efficient if the duct is larger. These valves also provide two-way flow.
Trunnion ball valves
In these valves, the ball, retaining cylinder and shaft bear the heavy loads produced by large balls and can actually be said to act as a single assembly. Thronion valves are also highly flexible and also have less torque than flotation valves.
Ball valves are usually divided into one-piece, three-piece, multi-piece, welded body, inlet from top and bottom according to how the body is made. In this section, we give a brief description:
- One-piece ball valves : This model is one of the cheapest models of ball valves. Its structure is integrated and the two parts that surround the ball are welded or pressed. This model is also used for less troublesome applications and can not be opened as a repair or cleaning.
- Three-piece ball valves : Valves that are more expensive are usually three-piece and their components are connected to each other by screws. In these valves, the service is performed without all the valves coming out of the pipeline.
- Multi-piece ball valves : The body of these valves is one, two or three pieces and their parts are connected to each other through a temporary connection and their parts are assembled from above or from the side. The advantages of this model include its low price, very simple assembly and disassembly, easy and simple repair.
- Ball valves with welding body: The body of this model of ball valves are connected to each other by welding and create an integrated structure. Repair in these valves is impossible and difficult, and the ability to bury in them is one of its advantages, which is due to the lack of bolt connections. Their advantages include the ability to be used in underground transmission lines, high pressures and their very long service life.
Types of ball valves in terms of gender
Ball valves are classified into four types in terms of material and body material: steel, stainless steel, polymer and brass, each of which has a special application according to the passing fluid and are as follows:
Brass ball milk
The use of this type of valves in fluids such as city gas in which the pressure and temperature are lower and are inactive in terms of corrosion is very high. The color of these valves is golden and their body is in one piece and because they are widely used in gas transmission and distribution lines, they are called gas valves. Silver brass ball valves, one-piece body, are used to cut off and connect the flow of water, and are also used for low temperature and pressure range.
Steel and stainless steel ball valve
These valves are used in high temperature and pressure ranges and all industrial cases, corrosive fluids, food industry, cut-off and connection of flow in manual type by gas handle.
Polymer ball valve
These valves are used for agriculture, irrigation and corrosive fluids such as acids and are produced from different materials UPVC, PVC, TUP and PP.
Benefits of using ball valve
- These valves are easier and less expensive to maintain than other valves.
- It is lighter than other valves and very easy to install.
- The pressure drop in the ball valves is almost zero.
- In the open state the fluid flow is completely uniform and in the closed state the fluid flow is completely cut off.
- In semi-open mode, it can be used 1/4.
- No need for a lubrication system
- A multi-way valve is used to change the flow direction.
Disadvantages of ball valve (wing valve )
One of the main disadvantages of ball valves is that when the valve is in the semi-open position, a uniform flow is not established when the fluid passes and the flow is disturbed. Now, if the valve is in the semi-open position, its seat, which is also made of very soft material, will be damaged and will lead to the ball colliding inside the valve or moving the seat. Therefore, it can be said that the ball valve will not be suitable at all when there is a need for pressure drop in the line and is only suitable for completely disconnecting and connecting the flow of fluid passing in the line.
Other disadvantages of this valve are its poor ability to adjust and control because this valve is designed to cut off flow and blockage and its design is not suitable for adjustment. Flow control leads to the site being exposed to erosion, which occurs due to the high speed and pressure in the flow, which eventually causes the valves to leak.
The ball valve has no use for passing the liquid-solid mixture and they can not be used in these cases because the suspended particles that accumulate and remain cause the valve to leak and these particles in the vicinity of the wing and seat in Cavities become solid and hard.
Fluid entry route to the valve :
The fluid entry path to these valves is as follows:
- In the form of Venturi
- As a reduction in cross section
- In the form of a completely open path
When fully open, these valves have a hole the size of the inside diameter of the pipe.
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