The control valve's size should be selected so that it will operate somewhere between 60 and 80% open at the maximum required flow rate and whenever possible, not much less than 20% open at the minimum required flow rate.  The idea is to use as much of the valve's control range as possible while maintaining a reasonable, but not excessive, safety factor.

If the valve is too small, it will be obvious immediately, as it will not be able to pass the required flow. In actual practice, under sized valves are fairly uncommon. Commonly, the valve is too large. An oversized control valve will cost more than is necessary, but more importantly, an oversized valve will be very sensitive. Small changes in valve position will cause large changes in flow. This will make it difficult or even impossible for it to adjust exactly to the required flow. Any stickiness caused by friction will be amplified by the overly sensitive oversized valve, reducing the precision to which the flow can be controlled.


Cavitation

Liquid applications must always be evaluated for cavitation. Not only does cavitation cause high noise and vibration levels, it can result in very rapid damage to the valve's internals and/or the downstream piping. Especially with rotary valves, the prediction of damaging levels of cavitation is more complex than simply calculating the choked flow pressure drop. As a result of flow separation and the formation of eddies within the valve, localized areas of pressure reduction and recovery can cause damaging cavitation at pressure drops well below that which results in fully choked flow. One proven method for predicting cavitation damage in rotary control valves is based on a correlation between calculated sound pressure level and the potential for damage.

Noise

In addition to the fact that a noisy valve in liquid service will most likely suffer unacceptable rates of cavitation damage, high noise levels usually cause vibration that can damage piping, instruments and other equipment. Control valves in steam and gas service can generate noise levels well in excess of plant standards, even at moderate pressure drops, especially in sizes above 3 or 4 inches. As a result, the valve sizing and selection process must always include noise calculations.

Installed Flow Characteristic

In nearly all applications, a control valve should have a linear installed flow characteristic (the relationship between controller output and flow in the system). The control valve's inherent (published) flow characteristic interacts with the system's flow vs. pressure loss characteristic to yield the installed flow characteristic. If the installed characteristic deviates significantly from linear, it will be difficult or impossible to tune the loop for both accurate and stable control throughout the entire flow range. A computerized analysis of the installed characteristic should be part of the control valve sizing and selection process.

Actuator Sizing

Sizing actuators for on-off service is fairly straight forward, requiring only that an actuator be selected with a torque output slightly higher than the seating and unseating torque of the valve. The situation is more complex with control valves. The torque output of most rotary actuators changes with the angle of opening. At the same time, the valve's torque requirement depends both on the opening angle and the throttling pressure drop at that particular angle. To ensure adequate spare torque to guarantee smooth, accurate control, a computerized analysis is recommended.

Selecting Control Valve Style

The choice of control valve style (globe, ball, butterfly, etc.) is often based on tradition or plant preference. For example, a majority of the control valves in pulp and paper mills are usually ball or segmented ball valves. Petroleum refineries traditionally use a high percentage of globe valves, although the concern for fugitive emissions has caused users to look to rotary valves because it is often easier to obtain a long lasting stem seal with rotary valves.

Globe valves offer the widest range of options for flow characteristic, pressure, temperature, and noise and cavitation reduction. Globe valves also tend to be the most expensive. Segment ball valves tend to have a higher rangeability, and size for size, nearly twice the flow capacity of globe valves, while they are typically less expensive than globe valves. On the other hand, segment ball valves are limited in availability for extremes of temperature and pressure and are more prone to noise and cavitation problems than globe valves.

High performance butterfly valves are even less expensive than ball valves, especially in larger sizes (eight inches and larger). They also have less rangeability than the ball valves and are more prone to cavitation.

The eccentric rotary plug valve combines the features of rotary valves, such as high cycle life stem seals and compact construction, with the rugged construction of globe valves. Unlike the other rotary valves whose flow capacity is approximately double that of globe valves, the flow capacity of eccentric rotary plug valves is on par with globe valves.

While the selection of a valve style is highly subjective, in the absence of a specified valve or plant preference, the following approach can be used to select a control valve style for applications where the valve will be six inches or smaller:

- Considering pressure, pressure differential, temperature, required flow characteristic, cavitation and noise, will a segment ball valve work?

- If a segment ball valve is not suitable, select a globe valve. Keep in mind that cage guided globe valves are not suitable for dirty service.

- For applications where the valve will be 8 inches or larger, first investigate the applicability of a high performance butterfly valve because of the potential for significant savings on cost and weight.

Ensuring Accuracy

Today control valve sizing calculations are usually performed using a computer program. Most manufacturers of control valves offer control valve sizing software at no cost, though most are specific to that manufacture&#;s valves only. Metso&#;s Nelprof, however, includes a number of generic valves, such as globe valves, ball valves, plug valves and butterfly valves, to choose from. These generic selections permit the user to investigate the applicability of different valve styles and sizes to a particular application, without showing a preference to a particular valve manufacturer.

Selecting a properly sized control valve is essential to achieving the highest degree of process control for the liquid, gas or multi-phase fluid. To ensure accuracy, use the following information for control valve sizing:

- If a set of loop tuning parameters only works at one end of the control range and not the other, the valve&#;s flow characteristic is most likely the wrong one.

- If a system has a lot of pipe, use an equal percentage valve.

- If a system has very little pipe, use a linear valve.

- A control valve that is sized to operate around 60% to 80% open at the maximum required flow and not much less than 20% open at the minimum required flow will give the best control.

• Properly sized full ball, segment ball and high performance butterfly valves are usually two sizes smaller than the line.*
• Properly sized globe valves are usually one size smaller than the line.*

- Most people consider it poor piping practice to use a control valve that is less than ½ the line size or larger than the line size.

- Oversized control valves are very common.

*If you size a valve and it turns out to be different than these, it is a good idea to check your work. You may have made a mistake, or the person who sized the pipe may have made a mistake.

Jon Monsen, Ph.D., P.E., is a Control Valve Technology Specialist at Valin Corporation, specializing in technical training and assisting Valin&#;s customers in the proper application of control valves.

Article featured in

Here are links to white papers that may be of interest:

Pressure at the Vena Contracta with Liquid Flow in a Control Valve
Installed Gain as a Control Valve Sizing Criterion
Aerodynamic Noise in Control Valves
Valve Aerodynamic Noise Reduction Strategies
Determining the Pressure Drop to be Used in a Control Valve Sizing Calculation

The content of these white papers are just a small portion of what you will learn in Dr. Monsen's book:

Would you rather learn from Dr. Monsen directly and have the ability to ask him questions?  Take one or more of his webinars:

When control valve professionals talk about "control valve sizing," they really mean the entire process of selecting the valve that will do the best job of controlling the process. Selecting the right size valve is an important part of the process, but there are other equally important considerations as well.The control valve's size should be selected so that it will operate somewhere between 60 and 80% open at the maximum required flow rate and whenever possible, not much less than 20% open at the minimum required flow rate. The idea is to use as much of the valve's control range as possible while maintaining a reasonable, but not excessive, safety factor.If the valve is too small, it will be obvious immediately, as it will not be able to pass the required flow. In actual practice, under sized valves are fairly uncommon. Commonly, the valve is too large. An oversized control valve will cost more than is necessary, but more importantly, an oversized valve will be very sensitive. Small changes in valve position will cause large changes in flow. This will make it difficult or even impossible for it to adjust exactly to the required flow. Any stickiness caused by friction will be amplified by the overly sensitive oversized valve, reducing the precision to which the flow can be controlled.In the illustration above, assuming that both valves are capable of positioning within 1%, the properly sized 3 inch valve will be able to control flow within 8 gpm, while the oversized 6 inch valve will only be capable of controlling flow to within 20 gpm.Liquid applications must always be evaluated for cavitation. Not only does cavitation cause high noise and vibration levels, it can result in very rapid damage to the valve's internals and/or the downstream piping. Especially with rotary valves, the prediction of damaging levels of cavitation is more complex than simply calculating the choked flow pressure drop. As a result of flow separation and the formation of eddies within the valve, localized areas of pressure reduction and recovery can cause damaging cavitation at pressure drops well below that which results in fully choked flow. One proven method for predicting cavitation damage in rotary control valves is based on a correlation between calculated sound pressure level and the potential for damage.In addition to the fact that a noisy valve in liquid service will most likely suffer unacceptable rates of cavitation damage, high noise levels usually cause vibration that can damage piping, instruments and other equipment. Control valves in steam and gas service can generate noise levels well in excess of plant standards, even at moderate pressure drops, especially in sizes above 3 or 4 inches. As a result, the valve sizing and selection process must always include noise calculations.In nearly all applications, a control valve should have a linear installed flow characteristic (the relationship between controller output and flow in the system). The control valve's inherent (published) flow characteristic interacts with the system's flow vs. pressure loss characteristic to yield the installed flow characteristic. If the installed characteristic deviates significantly from linear, it will be difficult or impossible to tune the loop for both accurate and stable control throughout the entire flow range. A computerized analysis of the installed characteristic should be part of the control valve sizing and selection process.Sizing actuators for on-off service is fairly straight forward, requiring only that an actuator be selected with a torque output slightly higher than the seating and unseating torque of the valve. The situation is more complex with control valves. The torque output of most rotary actuators changes with the angle of opening. At the same time, the valve's torque requirement depends both on the opening angle and the throttling pressure drop at that particular angle. To ensure adequate spare torque to guarantee smooth, accurate control, a computerized analysis is recommended.The choice of control valve style (globe, ball, butterfly, etc.) is often based on tradition or plant preference. For example, a majority of the control valves in pulp and paper mills are usually ball or segmented ball valves. Petroleum refineries traditionally use a high percentage of globe valves, although the concern for fugitive emissions has caused users to look to rotary valves because it is often easier to obtain a long lasting stem seal with rotary valves.Globe valves offer the widest range of options for flow characteristic, pressure, temperature, and noise and cavitation reduction. Globe valves also tend to be the most expensive. Segment ball valves tend to have a higher rangeability, and size for size, nearly twice the flow capacity of globe valves, while they are typically less expensive than globe valves. On the other hand, segment ball valves are limited in availability for extremes of temperature and pressure and are more prone to noise and cavitation problems than globe valves.High performance butterfly valves are even less expensive than ball valves, especially in larger sizes (eight inches and larger). They also have less rangeability than the ball valves and are more prone to cavitation.The eccentric rotary plug valve combines the features of rotary valves, such as high cycle life stem seals and compact construction, with the rugged construction of globe valves. Unlike the other rotary valves whose flow capacity is approximately double that of globe valves, the flow capacity of eccentric rotary plug valves is on par with globe valves.While the selection of a valve style is highly subjective, in the absence of a specified valve or plant preference, the following approach can be used to select a control valve style for applications where the valve will be six inches or smaller:- Considering pressure, pressure differential, temperature, required flow characteristic, cavitation and noise, will a segment ball valve work?- If a segment ball valve is not suitable, select a globe valve. Keep in mind that cage guided globe valves are not suitable for dirty service.- For applications where the valve will be 8 inches or larger, first investigate the applicability of a high performance butterfly valve because of the potential for significant savings on cost and weight.Today control valve sizing calculations are usually performed using a computer program. Most manufacturers of control valves offer control valve sizing software at no cost, though most are specific to that manufacture&#;s valves only. Metso&#;s Nelprof, however, includes a number of generic valves, such as globe valves, ball valves, plug valves and butterfly valves, to choose from. These generic selections permit the user to investigate the applicability of different valve styles and sizes to a particular application, without showing a preference to a particular valve manufacturer.Selecting a properly sized control valve is essential to achieving the highest degree of process control for the liquid, gas or multi-phase fluid. To ensure accuracy, use the following information for control valve sizing:- If a set of loop tuning parameters only works at one end of the control range and not the other, the valve&#;s flow characteristic is most likely the wrong one.- If a system has a lot of pipe, use an equal percentage valve.- If a system has very little pipe, use a linear valve.- A control valve that is sized to operate around 60% to 80% open at the maximum required flow and not much less than 20% open at the minimum required flow will give the best control.- Most people consider it poor piping practice to use a control valve that is less than ½ the line size or larger than the line size.- Oversized control valves are very common.*If you size a valve and it turns out to be different than these, it is a good idea to check your work. You may have made a mistake, or the person who sized the pipe may have made a mistake.Jon Monsen, Ph.D., P.E., is a Control Valve Technology Specialist at Valin Corporation, specializing in technical training and assisting Valin&#;s customers in the proper application of control valves.Article featured in Valve Magazine The content of these white papers are just a small portion of what you will learn in Dr. Monsen's book: Control Valve Application Technology Would you rather learn from Dr. Monsen directly and have the ability to ask him questions? Take one or more of his webinars:

For more feeding ball valveinformation, please contact us. We will provide professional answers.

Ball Valve: A Comprehensive Guide to Understanding and Selecting the Perfect Valve for Your Needs

In the world of industrial processes and fluid control, the ball valve stands as a pivotal component, offering a reliable and efficient solution for regulating the flow of various fluids.

Whether you are an engineer, a business owner, or someone curious about the intricacies of fluid dynamics, understanding ball valves is essential. In this comprehensive guide, we will delve into the depths of ball valves, exploring their design, functionality, applications, and the factors to consider when choosing the ideal ball valve for your specific requirements.

What is a Ball Valve?

At its core, a ball valve is a mechanical device used to control the flow of fluids, primarily liquids and gases, through a pipeline or system. It derives its name from the ball-shaped obturator that rotates within the valve body, serving as the main flow control element. By turning the valve handle or actuator, the ball can be aligned in different positions, allowing or obstructing the fluid&#;s path. Ball valves are renowned for their quick on/off operation, durability, and ability to endure high-pressure environments.

Our Best Selling Ball Valves

Construction and Working Mechanism

1. Valve Body:

The valve body, typically made from materials like stainless steel, brass, or cast iron, serves as the primary framework that holds all the components together. It contains ports for fluid entry and exit and encases the ball and other internal parts securely.

2. Ball:

The heart of the ball valve is the spherical ball, usually made from materials like chrome-plated brass, stainless steel, or PVC. The ball features a hole (bore) through its center, which allows or obstructs fluid flow when aligned or rotated perpendicular to the pipeline.

3. Valve Stem:

The valve stem connects the ball to the external actuator or handle. It acts as a pivotal link, facilitating the movement of the ball within the valve body.

4. Seats and Seals:

To ensure a tight seal and prevent leakage, ball valves employ seats and seals around the ball&#;s surface. The materials used for these components depend on the fluid being handled and the temperature and pressure conditions.

5. Actuator:

The actuator serves as the external control mechanism for the ball valve. It can be in the form of a lever, handwheel, pneumatic actuator, or electric motor, allowing easy manipulation of the ball&#;s position.

6. End Connections:

Ball valves come with various end connections to suit different applications. Common types include threaded, flanged, or welded ends.

Utilizing a ball valve in conjunction with your water tank

Utilizing a ball valve in conjunction with your water tank and pump can offer efficient control over the water flow and contribute to the smooth operation of your system.

1. Filling and Emptying the Water Tank:

One of the primary uses of a ball valve in this setup is to regulate the flow of water into and out of the water tank. When you need to fill the tank with water from an external source, simply open the ball valve by turning the handle or actuator. This allows water to enter the tank, and you can monitor the filling process as needed.

Conversely, when it&#;s time to empty the tank, perhaps for maintenance or to supply water to various outlets, you can close the ball valve to stop the inflow and open it again to release the water. The quick on/off operation of the ball valve ensures efficient control without any delay.

2. Controlling Water Pressure:

In some instances, you might want to control the water pressure from the tank to match the requirements of your specific application. A ball valve placed downstream of the pump can be adjusted to regulate the flow rate, which, in turn, affects the water pressure.

By partially closing the ball valve, you reduce the flow, and consequently, the pressure increases. Conversely, opening the valve wider allows more water to pass through, resulting in reduced pressure. This simple adjustment can be crucial for applications where maintaining a consistent water pressure is essential.

3. System Isolation:

A ball valve is also useful for isolating the water tank and rainwater pump from the rest of the system. For instance, if you need to conduct maintenance on the pump or replace the tank, closing the ball valve will halt the water flow, preventing any water from entering or leaving the system during the maintenance process.

This isolation feature is especially valuable as it eliminates the need to shut off the entire water supply, enabling you to work on the specific components without disrupting the overall water distribution.

4. Emergency Shut-Off:

In the event of an emergency, such as a sudden leak or a malfunctioning pump, having a ball valve in place allows for a swift shut-off of water flow. The quick and reliable on/off operation ensures immediate response to mitigate potential damage or hazards.

5. Winterizing the System:

In regions where freezing temperatures are a concern, winterizing the water tank and pump becomes crucial. By closing the ball valve and draining the water from the system, you can prevent water from freezing and causing damage to pipes and components.

Remember that selecting the appropriate ball valve size, material, and pressure rating is vital to ensure it can handle the specific demands of your water tank and pump system. Regular maintenance and periodic inspections of the valve and its associated components will also help maintain its functionality and extend its service life.

Types of Ball Valves

1. Full Bore Ball Valve:

The full bore ball valve, also known as a full port ball valve, features a large ball with a bore diameter equal to the pipeline&#;s inner diameter. This design minimizes flow restrictions, resulting in reduced pressure drops across the valve.

Are you interested in learning more about petrochemical valve components? Contact us today to secure an expert consultation!

2. Reduced Bore Ball Valve:

The reduced bore ball valve, or reduced port ball valve, has a smaller ball bore diameter compared to the pipeline&#;s inner diameter. While it offers slightly higher resistance to flow, it is more compact and cost-effective.

3. Floating Ball Valve:

In a floating ball valve, the ball is not fixed to the valve stem. Instead, it is allowed to float slightly, relying on the pressure of the fluid to create a seal against the seats.

4. Trunnion-Mounted Ball Valve:

The trunnion-mounted ball valve utilizes additional mechanical support through a trunnion, which reduces the ball&#;s load on the seats. This design is preferred for larger and high-pressure valves.

5. V-Port Ball Valve:

The V-port ball valve features a V-shaped ball, which enables greater flow control accuracy. It finds applications in precise flow regulation processes.

6. Multi-Port Ball Valve:

A multi-port ball valve comes with multiple ports and ball configurations, allowing versatile flow patterns and diverting fluid in various directions.

Advantages of Ball Valves

Ball valves offer numerous advantages, making them a popular choice across various industries. Some key benefits include:

• Quick and Reliable Shut-off: Ball valves provide fast on/off operation, ensuring immediate shut-off when necessary, critical in emergencies.
• Low Pressure Drop: The streamlined design of ball valves minimizes pressure loss, making them energy-efficient.
• Durability and Longevity: High-quality materials and robust construction make ball valves resistant to wear and corrosion, contributing to their extended service life.
• Wide Temperature and Pressure Range: Ball valves can handle a broad range of temperatures and pressures, making them suitable for diverse applications.
• Bi-Directional Flow: Ball valves can control fluid flow in both directions, enhancing their versatility.

Applications of Ball Valves

The versatility and reliability of ball valves enable their use across numerous industries and applications:

1. Oil and Gas Industry:

Ball valves are prevalent in the oil and gas sector for their ability to control the flow of crude oil, natural gas, and various other hydrocarbons.

2. Petrochemical and Chemical Industry:

In chemical processing plants, ball valves play a crucial role in managing aggressive and corrosive fluids with precision.

3. Water and Wastewater Treatment:

Ball valves are widely used in water distribution networks, treatment plants, and wastewater management systems due to their efficiency and resilience.

4. HVAC Systems:

Ball valves regulate the flow of water and refrigerants in heating, ventilation, and air conditioning systems, aiding in temperature control.

5. Pharmaceutical and Food Processing:

In industries with stringent hygiene requirements, such as pharmaceuticals and food processing, ball valves offer smooth operation and ease of cleaning.

6. Marine and Shipbuilding:

Ball valves are essential components in shipbuilding and marine applications, providing reliable fluid control on vessels.

Selecting the Right Ball Valve

Choosing the appropriate ball valve for your specific needs requires consideration of several factors:

1. Valve Size and End Connections:

Select a valve size compatible with your pipeline, and ensure the end connections match your existing system.

2. Material Selection:

Evaluate the compatibility of valve materials with the fluid being handled and the environmental conditions.

3. Pressure and Temperature Ratings:

Ensure that the selected ball valve can withstand the pressure and temperature requirements of your application.

4. Flow Control Requirements:

Determine the degree of flow control precision needed and choose the appropriate ball valve type (full bore, V-port, etc.).

5. Actuation Type:

Consider the ease of operation and the required actuation mechanism (manual, electric, or pneumatic).

Summary

Ball valves, with their efficient design and robust functionality, have revolutionized fluid control in countless industries. Understanding their construction, working mechanisms, types, and applications is crucial for making informed decisions when selecting the right ball valve for your needs. Whether in oil and gas, chemical processing, water treatment, or various other sectors, the right ball valve can optimize operations, enhance efficiency, and ensure the smooth flow of fluids in your systems.

Contact us to discuss your requirements of pneumatic control valve from china manufacturer. Our experienced sales team can help you identify the options that best suit your needs.