Ball Valve

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Ball Valve

What is a Ball valve

A ball valve is a form of quarter-turn valve which uses a hollow, perforated and pivoting ball (called a "floating ball") to control flow through it. It is open when the ball's hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve's status.

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff applications, where they are often preferred to gates and globe valves, but they lack their fine control in throttling applications.

The ball valve's ease of operation, repair, and versatility lend it to extensive industrial use, supporting pressures up to 1000 bar andtemperatures up to 752°F (500°C), depending on design and materials used. Sizes typically range from 0.2 to 48 inches (0.5 cm to 121 cm). Valve bodies are made of metal, plastic, or metal with a ceramic; floating balls are often chrome plated for durability.

Types of Ball Valve

Types of Ball Valve

  • Duplex ball valve

There are five general body styles of ball valves: single body, three-piece body, split body, top entry, and welded. The difference is based on how the pieces of the valve—especially the casing that contains the ball itself are manufactured and assembled. The valve operation is the same in each case.

In addition, there are different styles related to the bore of the ball mechanism itself.

Ball valves in sizes up to 2 inch generally come in single piece, two or three piece designs. One piece ball valves are almost always reduced bore, are relatively inexpensive and generally are throw-away. Two piece ball valves are generally slightly reduced (or standard) bore, they can be either throw-away or repairable. The 3 piece design allows for the center part of the valve containing the ball, stem & seats to be easily removed from the pipeline. This facilitates efficient cleaning of deposited sediments, replacement of seats and gland packings, polishing out of small scratches on the ball, all this without removing the pipes from the valve body. The design concept of a three piece valve is for it to be repairable.

  • Full port

A full port or more commonly known full bore ball valve has an over-sized ball so that the hole in the ball is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted but the valve is larger and more expensive so this is only used where free flow is required, for example in pipelines which require pigging.

  • Reduced port

In Reduced port (more commonly known as reduced bore) ball valves, flow through the valve is one pipe size smaller than the valve's pipe size resulting in flow area being smaller than pipe. As the flow discharge remains constant and is equal to area of flow times velocity, the velocity increases with reduced area of flow.

  • V port

A V port ball valve has either a 'v' shaped ball or a 'v' shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. When the valve is in the closed position and opening is commenced the small end of the 'v' is opened first allowing stable flow control during this stage. This type of design requires a generally more robust construction due to higher velocities of the fluids, which might damage a standard valve. These can be referred to as a type of control valve but are not as accurate as a balancing valve, needle valve, globe valve, or pressure regulating valve.

  • Cavity filler

Many industries encounter problem with residues in the ball valve. Where the fluid is meant for human consumption, residues may also be health hazard, and when where the fluid changes from time to time contamination of one fluid with another may occur. Residues arise because in the half open position of the ball valve a gap is created between the ball bore and the body in which fluid can be trapped. To avoid the fluid getting into this cavity, the cavity has to be plugged, which can be done by extending the seats in such a manner that it is always in contact with the ball. This type of ball valve is known as Cavity Filler Ball Valve.

There are a few types of ball valves lateral movement of the ball:

  • Trunnion

A trunnion ball valve has additional mechanical anchoring of the ball at the top and the bottom, suitable for larger and higher pressure valves (say, above 10 cm and 40 bars).

  • A floating ball valve is one where the ball is not held in place by a trunnion. In normal operation, this will cause the ball to float downstream slightly. This causes the seating mechanism to compress under the ball pressing against it. Furthermore, in some types, in the event of some force causing the seat mechanism to dissipate (such as extreme heat from fire outside the valve), the ball will float all the way to metal body which is designed to seal against the ball providing a somewhat failsafe design.  

Manually operated ball valves can be closed quickly and thus there is a danger of water hammer. Some ball valves are equipped with an actuator that may be pneumatically, hydraulically or motor operated. These valves can be used either for on/off or flow control. A pneumatic flow control valve is also equipped with a positioner which transforms the control signal into actuator position and valve opening accordingly.

  • Multiport

    • Three- and four-way have an L- or T-shaped hole through the middle. The different combinations of flow are shown in the figure. It is easy to see that a T valve can connect any pair of ports, or all three, together, but the 45 degree position which might disconnect all three leaves no margin for error. The L valve can connect the center port to either side port, or disconnect all three, but it cannot connect the side ports together.

    • Multi-port ball valves with 4 ways, or more, are also commercially available, the inlet way often being orthogonal to the plane of the outlets. For special applications, such as driving air-powered motors from forward to reverse, the operation is performed by rotating a single lever four-way valve. The 4-way ball valve has two L-shaped ports in the ball that do not interconnect, sometimes referred to as an "×" port.

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Ball valves can be used in a variety of applications and markets, such as transmission and storage, gas processing, industrial, and many more. Ball Valves provide reliable leak protection which is especially beneficial in gas applications. Ball valves have low pressure drop and can open and close quickly. 

Chemical and Petrochemical Complexex

  • Low Differential Pressure Control

  • Emission Control

  • Handle Highly Viscous Fluids. Abrasive Slurries or Corrosive as well as non-corrosives in processes and Storing Facilities

Power Industry

 

  •     Boiler Feed Water Control

  •     Control abd Shot-off for Steam

  •     Burner Trip Valves

  •     Sluicing Valves for Feding Coal into Pressurised Combustore and for extracting fly ash

Gas and Oil Production

  •     Subsea Isolation and Shut-down

  •     Well-Head Isolation

  •     Piping Suege Control

  •     Secondary and Enhanced Oil Recovery

  •     Processing Separration

  •     Transmission and Distribution

  •     Storage Tang

Pulp and paper Industry

  •     Pulp Mill Diagesters

  •     Shut-off Valves

  •     Batch-Digester Blow Service

  •     Liquor Fill and Circulation

  •     Lime Mud (Slrry) Flow Contro

  •     Dilution Water Control

Other Common area for the application of ball valves include: Food Industry. Water supply and transport, Marine and soilds transport.

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Micro-resistance Ball Valve uses the rubber covered roller as the disc, which, under the action of the medium, can roll up and down along with the sliding path inside the valve so as to open or close it. And it features by the big flow, small flow-resistance loss, good tightness, silent close and reduced water shock wave. It can be mountable vertically or horizontally and used on the outlet of the water pump of the cold-water, hot-water, industrial and living sludge pipe networks to prevent the medium from going back.

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A ball valve is a device with a spherical closure unit that provides on/off control of flow. The sphere has a port, also known as a bore, through the center. When the valve is positioned such that the bore is aligned in the same direction as the pipeline, it is in open position and fluid can flow through it. When rotated 90 degrees, the bore becomes perpendicular to the flow path, meaning the valve is closed and the fluid cannot pass through.

The ball valve, along with butterfly and plug valves, is part of the quarter-turn valve family. Ball valves are known for reliable, bubble-tight sealing. Thus, they are a great choice for gas applications where tight shutoff is necessary. Due to the potential of constant wearing on the seats, ball valves are not ideal for throttling applications. The body of a ball valve usually is made of steel and can be made more durable with nickel plating. 

The most common ball valves are considered to be two-way, which allows flow to travel linearly from the inlet to the exit. Furthermore, the three-way and four-way ball valves allow for flow to travel in multiple directions, including 90-degree angles. 

There are four general body styles of ball valves: fully welded, three-piece body (also called side or end-entry), split-body, and top-entry. The difference is based on how the pieces of the valve are manufactured and assembled, but the valve operation is the same in each type. Each design has its benefits. For example, the design of the our Ball Valve fully welded ball valve gives it maximum strength at minimum weight, as well as maximum resistance, both to pipeline pressures and stresses. The compact, spherical design also eliminates body flanges, thus reducing overall size and leak paths.

Knowledge of the different parts of a ball valve will give you a generalized idea of how it will work during the entire span after it has been installed by your designated workforce.

While contemplating on the brand and type of ball valve to purchase for use in your shut off application or flow control system, be in the know of its various parts. Having an adept knowledge of its parts will give you an idea of how the valve entirely works when it is installed.

  • Body or Shell

This part is regarded as the principal part of a valve, regardless of its shape and type. It is the part that gives framework to the whole valve because it holds all the other parts intact. It also serves as the pressure boundary of the valve because it is the first line of resistance against the volume and pressure of the liquid flowing through all the pipes connected to it.

  • Bonnet

This part covers the opening in the valve’s body. It also serves as the second pressure boundary. Valve bonnets are usually bolted and screwed with the body. It is also usually made of the same material as the body to make the whole valve firmer and stronger.

  • Trim

This part is a collection of differentinternal valve parts such as disk, seat, stem and sleeves. Because of these internal parts, the valve can perform basic motions to provide flow control. The disk together with the seat is important in determining the performance of the valve system. In most designs, the disk serves as the third layer of pressure boundary. It can permit and prohibit fluid flow due to its pressure-retaining capacity.

The seat, also called as seals ring provides an interface to where the disk is seated. The seal rings can either be forged within the body by welding or by machine. The stem is responsible for positioning the disk. It connects the actuator and the disk usually though welded joints.

  • Actuator

This part works in conjunction with some internal parts located in the valve trim. This part is responsible for running the stem and disk. There are many types of actuator that are available in the market today. Some are handwheels, levers, motors, solenoids, pneumatic operators or hydraulic arms. Most valve manufacturers’ provide a design where the actuator is mounted with the bonnet through a yoke.

  • Packing

This part commonly prevents leaks from the space between the valve stem and bonnet. The valve packing can be made from fibrous materials like flax or some other materials like Teflon. Regardless of the valve packing composition, it should be able to form a seal between the internal parts and the outer valve environment where the stem extends from the valve body. The packing must be properly placed to prevent leaks that can cause further damages to the entire valve system. The packing must neither be too loose nor too tight.

In summary, knowledge of the different parts of a ball valve will give you a generalized idea of how it will work during the entire span after it has been installed by your designated workforce. It will also help you to have a rough estimate of the cost of implementing a flow control system with the use of a ball valve.

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