What is the selection criteria for a globe valve?

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Introduction:

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The globe valve, as the name suggests is a linear motion valve with a round globular shaped body which
is commonly known as a form of mechanism that is used mainly to impede or regulate the flow of gas or liquid within a pipe. It has a seat that is well structured right in the middle and in turn parallel towards the pipe which has the opening enclosed by using a disc. The globe valve has a plug that is connected to a stem that functions by means of a screw action in the manual valves.

Control Method:

The globe valve has a disk that opens completely or closes completely the flow path. This action is done in a perpendicular movement to that of the disk away from the seat. The circular space present between the disk and seat ring gradually changes in order to facilitate the fluid flow through the valve. When the fluid travels through the valve it changes the direction many times while increasing the pressure as well. Generally, these valves are fitted with a stem vertical while the fluid stream is connected to the side of the pipe above the disk which helps in maintaining a tighter seal when the valve is fully closed.

Functions:

Globe valves are used for the throttling systems because the change of gradual spacing between the disk and seat ring gives these valves a good throttling ability apart from this they are used as shut on/off valves. It can also be utilized in other applications due to its linear motion but only as long as the pressure and temperature limits remain under the control.

Media:

The globe valves are used for both liquid and gaseous systems, but these are not preferred for slurry or high purity systems. Here in this valve, the media flow rate is determined by the distance between the valve seat and the valve plug.

Selection Criteria:

Being mainly used as a block valve or for flow regulation, where the resistance to the flow is not of a positive or critical closing action. Having a winding action configuration which is typical of the closing method results in higher resistance to flow compared with other valves. Further, these valve types are made out of metallic alloys but there are few products that use synthetic materials which are utilized according to the temperature, pressure and controlled media properties. These valves can last longer once it gets treated with the process of erosive and corrosive steams that requires a proper materials selection and body coatings.

In order to know the ideal valve to use, here is a selection guide as suggested by a typical Globe Valves Supplier:

&#; While selection look for linear actuators that are directly coupled and have passed the quality control specifications i.e., UL FM approved valves and WARS approved valves which guarantees that the valve manufacturers were able to meet required and demanded quality.
&#; The coupled actuators should be structured in such a way that they are easy to mount and should be done without any need for any adjustments, adapters, linkages or brackets.
&#; Always select from among the models that will suit your need particularly give preference between water and steam control.
&#; The globe valves should be built based on the percentage of flow characteristics in accordance with water and characteristics of linear flow along with steam applications.
&#; The valve&#;s accurate positioning should be verified to ensure when in use they will provide proper temperature control.
&#; Search for the valve models that contain a pressure balance since it helps to obtain a higher closure.

Conclusion:

Now that the factors that need to be considered while selecting an ideal globe valve are known, we need to use them so as to ensure that we will be able to obtain a product that is of mint condition.

Fevisa, being one of the leading European valve manufacturers and valve stockist in USA, always ensure that the client is given with a proper valve solution and installation which is of primary importance to maximize it to the fullest simultaneously avoiding inconveniences on the course of the valve usage according to the industrial requirements. Our Valves are Europe Origin Valves and we are known are ex- stock valves.

1- Introduction

This article explores the crucial aspects of selection of valves especially ball and globe valves which are essential components in various industrial applications. Valves play a pivotal role in controlling fluid flow within systems, ensuring optimal performance and safety. The selection process involves evaluating key criteria such as valve type, material, size, pressure rating, and end connections.

This intention of this article is to provide an overview of the selection criteria for ball and globe valves, enabling engineers and professionals to make informed decisions in their valve procurement processes.

2- Key considerations for valve selection

Figure 2: Key considerations for valve selection

When selecting valves, several key considerations need to be considered to ensure optimal performance and compatibility with the intended application. The following are the key considerations:

2.1- Valve Type:

The choice between ball valves, globe valves, gate valves, butterfly valves, or other types depends on factors such as flow characteristics, pressure drop, tight shut-off requirements, and the need for throttling capabilities [1].

Each type of valve has its specific uses, advantages and disadvantages and the engineers are responsible for selection of correct type of valve based on the application requirements. For example, if tight shut off is required in an application, then ball valve would be a better option and if throttling or flow control is required then gate valve would be better suited choice.

2.2- Material Compatibility:

Valve materials must be compatible with the fluid being controlled and the operating conditions, including temperature, pressure, and corrosion resistance. Common materials include stainless steel, carbon steel, brass, bronze, and various alloys [2].

1. The metallurgical engineers evaluate the material of the valve based on the application. For example, if the valve is going to be used in food processing plant then stainless steel would be a better choice as compared to carbon steel because of its high corrosion resistance properties.
2. The temperature of process is also a driving factor in material selection of valves. Cryogenics, normal temperature and high temperature are different categories in which different materials are available for selection. Low temperature carbon steel such as ASTM A350 would a better suited material for cryogenics as compared to simple carbon steel.
3. The pressure of the medium also plays an important role in selection of valve materials. The internals including obturator of the valve should be strong enough to bear the maximum & design pressure of the medium.

2.3- Size and Flow Capacity:

Valve size should be selected based on the required flow rate, pipe size, and the desired level of pressure drop and turbulence. Proper sizing ensures efficient flow control and minimizes energy losses [3].

Each application has its desired flow rate and pressure which needs to be maintained.

The selection of the valve should be carried out based on the application requirements, for example, sudden pressure surges are expected when selecting a ball valve or any other tight shut off valves. If the pressure surge will cause detrimental issues then going with a different type of valve would be a suitable option. Similarly, sizing of the valve provides the pressure drop which the valve itself will cause during operation on required flow rate. This also needs to be considered during selection of valves.

For example, if a leak detection system is going to be installed on a pipeline then the pressure drop of the valve will play an important role in the leak detection and location capabilities of the system.

2.4- Pressure Rating:

Valves must have a pressure rating that matches or exceeds the maximum operating pressure of the system to ensure safe and reliable operation. The pressure rating is typically specified by the manufacturer and must conform to industry standards [4].

This parameter needs to be considered with 2.2 and 2.3. Flow rate, pressure and temperature of an application will determine the pressure rating of the valve which is required for that application. Selection should be made accordingly.

2.5- End Connections:

Compatibility between the valve's end connections and the existing piping system is crucial to ensure proper installation, prevent leakage, and facilitate maintenance. Common types of end connections include threaded, flanged, welded, and compression fittings [5].

1. Different type of end connections are required in different industrial applications and installation configurations. For example, if the valve is going to be installed in tubing then threaded connection is better suited as compared to flanged connection during installation between piping.
2. End connections are also interlinked with the pressure rating of the valve, hence this criteria needs to be considered with previous described criterion.

Figure 3: Threaded end connection and flanged end connection in valves

2.6- Industrial Standards and Certifications:

Valves should comply with relevant industry standards and certifications, such as those set by the American Petroleum Institute (API), International Organization for Standardization (ISO), and American Society of Mechanical Engineers (ASME). Adhering to these standards ensures quality, safety, and interoperability [6].

The requirements of the industrial standards will be defined by the process engineer and it is usually mentioned in the piping class or line class of the application.

2.7- Operational Requirements:

Considerations like the frequency of operation, automation requirements, ease of maintenance, life cycle costs and accessibility for repairs or replacements should also be evaluated to ensure the valve meets the specific operational needs of the system.

• For example, if a valve is going to be installed on an unmanned site then a remote control actuator would be suggested as compared to hand operated lever or wheel.

It is important to consult valve manufacturers, industry guidelines, and engineering references to obtain detailed information regarding the selection criteria for valves in specific applications.

3- Ball Valve

Ball valves are widely used in various industries for controlling fluid flow. They are quarter-turn valves with a spherical closure element, known as the ball, which rotates to control the flow passage. Ball valves offer several advantages, including reliable shut-off, excellent flow control, and low maintenance requirements. This article aims to provide insights into the selection of ball valves, highlighting their benefits, design considerations, and potential drawbacks.

Figure 4: Ball Valve Components

3.1- Characteristics of ball valves

1. Reliable Shut-off: Ball valves provide tight shut-off, minimizing leakage and preventing fluid loss when fully closed. The ball seals against resilient seats, ensuring a reliable seal under various operating conditions [7].
2. Excellent Flow Control: Ball valves offer precise flow control, thanks to their full or reduced bore design. In the fully open position, ball valves provide unobstructed flow, minimizing pressure drop and allowing for high flow rates [7]. Flow control of the valve is not to be confused with flow throttling of valve in which the user can adjust the flow rate as per the requirements.
3. Quick Operation: Ball valves have a quarter-turn operation, enabling rapid opening or closing with a simple 90-degree rotation of the lever or actuator. This quick operation is advantageous in applications where swift response is required for example during selection of emergency shut down valve in IOPPS (Instrumented Over pressure protection system) application [7].
4. Wide Range of Applications: Ball valves are versatile and suitable for a broad range of applications, including petrochemical, oil and gas, water treatment, pharmaceuticals, HVAC, and more. They can handle various types of fluids, including gases, liquids, and slurries.

3.2-Advantages of Ball Valves

Ball valves offer several advantages, making them a preferred choice in many applications:

1. Low Pressure Drop: Ball valves have a smooth flow path, resulting in minimal pressure drop across the valve. This characteristic is beneficial in systems where energy efficiency and reduced pumping costs are crucial. This makes ball valve a suitable choice for application like leak detection system or lines with high integral pressure drops or lines with inclination towards slack line flow conditions.
2. Bi-Directional Flow: Ball valves allow for bidirectional flow, enabling operation in either direction. This flexibility eliminates concerns about installation orientation and simplifies system design. This characteristic is suitable for application where reverse flow is envisaged.
3. Compact design: Ball valves have a compact design which uses lesser space as compared to other valves. Therefore, it can be a suitable choice in applications where spatial constraints are present.
4. Wide Temperature Range: Ball valves can withstand a broad temperature range, making them suitable for applications with high or low temperature conditions. Proper material selection ensures compatibility with the specific temperature requirements [7].

3.3- Limitations of Ball Valves

While ball valves offer numerous advantages, they also have a few limitations to consider:

1. Limited Throttling Capability: Compared to globe valves, ball valves have limited throttling capability due to their design. They are better suited for on/off applications rather than precise flow control in systems requiring fine adjustments.
2. Higher Torque Requirement: Depending on the valve size and pressure rating, ball valves may require higher torque for operation, which could affect actuator selection.
3. Potential for Cavitation: In high-pressure differentials, ball valves may be prone to cavitation, leading to flow disturbances and potential damage to the valve or the system. Proper sizing and consideration of system conditions can help mitigate this risk.

 

In conclusion, ball valves are versatile, reliable, and efficient flow control devices suitable for various applications. Their excellent shut-off capabilities, precise flow control, and quick operation make them a preferred choice in many industries.

By considering design and sizing guidelines and understanding their advantages and limitations, engineers can select the most appropriate ball valves for their specific applications.

4- Globe Valve

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Globe valves are widely used in various industries for controlling fluid flow. They are characterized by a spherical body with an internal baffle and a movable disk-like element known as the plug. Globe valves offer precise control over fluid flow, making them suitable for applications that require accurate regulation. This section aims to provide insights into the selection of globe valves, highlighting their benefits, design considerations, and potential limitations.

Figure 5: Globe Valve Components

4.1- Characteristics of globe valves

Globe valves offer several advantages that make them a suitable choice for many applications:

1. Precise Flow Control: Globe valves provide excellent flow control due to their linear motion design. The plug can be positioned at various degrees of opening, allowing for precise adjustment of flow rates and throttling capabilities.
2. Reliable Shut-off: Globe valves offer reliable shut-off capabilities, ensuring minimal leakage when fully closed. The plug is designed to provide a tight seal against the valve seat, preventing any unwanted flow.
3. Suitable for High-Pressure Applications: Globe valves are well-suited for high-pressure applications due to their sturdy construction and ability to withstand high fluid pressures. They can handle demanding operating conditions with ease.
4. Good Flow Characteristic: The flow characteristic of globe valves is generally linear, which means that the flow rate is directly proportional to the valve opening. This characteristic simplifies flow control and system design.

4.2- Advantages of Globe Valves

Globe valves offer several advantages, including the ones listed in the characteristics, that make them suitable for a wide range of applications:

1. Good for Throttling: Globe valves excel in applications that require fine adjustments and throttling capabilities, thanks to their linear flow characteristic.
2. Versatility: Globe valves can handle a variety of fluids, including liquids, gases, and steam, making them versatile for different industries and applications.

4.3- Disadvantages of Globe Valves

While globe valves offer numerous advantages, it is important to consider their potential limitations:

1. Slower operation: Globe valves have a slower response time compared to ball valves due to the linear motion required for operation.
2. Larger footprint: They tend to have a larger physical footprint compared to ball valve
3. Pressure Drop: Globe valves tend to have a higher-pressure drop compared to other valve types due to their design and the presence of the internal baffle. This characteristic can impact system efficiency and energy consumption.
4. Complex Design: Globe valves have a more complex design compared to some other valve types, which can make them costlier to manufacture and maintain.

 

In conclusion, globe valves offer precise flow control, reliable shut-off, and suitability for high-pressure applications. By considering design and sizing guidelines and understanding their advantages and limitations, engineers can select the most appropriate globe valves for their specific applications.

5- Case Studies

Figure 6: Ball Valve vs Globe Valve

5.1- Case Study 1: Selection of Ball Valve

5.1.1- Operating Conditions/Inputs:

• Application: Emergency shut down system for corrosive production fluid.
• Fluid: Corrosive production fluid.
• Flow Control: On/off operation.
• Pipe Size: 18 inches.
• Pressure Rating: Max 140 barg.
• Temperature Range: -40°C to 100°C.
• Maintenance Requirements: Minimal maintenance preferred.

5.1.2-Selection of Valve Type: Ball Valve

Considering the operating conditions and requirements of the industrial water supply system, a ball valve is the optimal choice. Here's the argument for selecting a ball valve:

1. Flow Control: Since the application requires on/off operation and does not necessitate fine flow regulation, a ball valve's quick quarter-turn operation is advantageous. It allows for efficient flow control with minimal effort.

2. Pressure Rating: With a maximum design pressure of 140 bar g, ball valves  with 900# rating are well-suited for this system. They can handle the required pressure without compromising their integrity.

3. Temperature Range: The temperature range of -40°C to 100°C falls within the standard operating range of ball valves, making them suitable for the application.

4. Maintenance: Ball valves are known for their low maintenance requirements. With minimal moving parts and a simple design, they offer long-term reliability and reduced downtime.

5. Material Compatibility: Generally Carbon steel valve are considered for such applications. But in this particular case of -40°C design temperature, the selected valve material would be LTCS (Low temperature carbon steel). Unless the OEM provides evidence the CS (Carbon Steel) would pass the impact test at -40°C as per ASME B31.3

6. Cost-effectiveness: Ball valves are generally cost-effective compared to other valve types, making them a suitable choice for industrial applications.

 

Considering the above factors, a ball valve provides efficient flow control, reliable shut-off, and minimal maintenance for the industrial water supply system in the manufacturing plant.

5.1.3- Conclusion:

In this case study, the selection of a ball valve is justified based on the on/off operation requirement, pressure rating, temperature range, low maintenance needs, material selection and cost-effectiveness. The ball valve's quick operation, reliability, and compatibility with the system's specifications make it an optimal choice for this application.

5.2- Case Study 2: Selection of Globe Valve

5.2.1- Operating Conditions/Inputs:

• Application: Emergency shut down system for corrosive production fluid.
• Fluid: Corrosive production fluid.
• Flow Control: line isolation.
• Pipe Size: 2 inches.
• Pressure Rating: Max 140 barg.
• Temperature Range: -40°C to 100°C.
• Maintenance Requirements: Regular maintenance is expected.

5.2.2- Selection of Valve Type: Globe Valve

Considering the operating conditions and requirements of the steam distribution system in the power plant, a globe valve is the optimal choice. Here's the argument for selecting a globe valve:

1. Flow Control: The requirement for line isolation and throttling capabilities in the system is well-suited for a globe valve. The linear motion design and adjustable plug allow for accurate regulation of flow rates and tight shut off during line isolation.

2. Pressure Rating: Globe valves are known for their ability to handle high-pressure applications. With a maximum design pressure of 140 barg and 2 inch line size, globe valves with # rating will provide the necessary strength and integrity for the system.

3. Temperature Range: The temperature range of -40°C to 100°C falls within the operating range of globe valves, making them suitable for the high-temperature steam in the power plant.

4. Maintenance: Regular maintenance schedules in place for the power plant allow for periodic inspection and servicing of the globe valves. Their design allows for easy access and maintenance of internal components.

5. Throttling Capability: Globe valves excel in applications that require fine adjustments and precise flow control, and line isolation. Making them suitable for required application.

 

Considering the above factors, a globe valve provides precise flow control, line isolation, reliable shut-off, and the necessary strength to handle high-pressure and high-temperature conditions in the system.

5.2.3- Case Study Conclusion:

In this case study, the selection of a globe valve for the system is justified based on the requirement for precise flow control, line isolation, high-pressure rating, compatibility with the temperature range, and the presence of regular maintenance schedules. The globe valve's ability to handle throttling, its robust construction, and its suitability for the system's specifications make it the optimal choice for this application.

6- Conclusion

In conclusion, the selection of ball and globe valves play a crucial role in ensuring the performance, reliability, and safety of these essential components in various industries. The choice between ball valves and globe valves depends on specific application requirements and operating conditions.

Ball valves offer advantages such as precise flow control, tight shut-off, and suitability for a wide range of pressures and temperatures. They are particularly well-suited for applications involving corrosive fluids, where their robust construction and sealing capabilities are essential.

On the other hand, globe valves excel in applications requiring precise throttling and flow control, along with reliable shut-off. They are commonly used in systems with high-pressure and high-temperature conditions, such as steam distribution systems.

By considering the operating conditions, requirements, and testing standards, manufacturers and end-users can make informed decisions regarding the selection of ball and globe valves.

Figure 7: Ball Valve vs Globe Valve Infographic

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7- References

[1] Emerson. (n.d.). Valve Selection Guide. Retrieved from https://www.emerson.com/documents/automation/valve-selection-guide-en-.pdf

[2] Valve Manufacturers Association of America. (). Valve Materials: A Comprehensive Guide. Retrieved from https://www.vma.org/page/ValveMaterials

[3] Neles. (n.d.). Valve Sizing and Selection. Retrieved from https://www.neles.com/handbook/valve-sizing-and-selection/

[4] American Society of Mechanical Engineers. (). ASME B16.34 - Valves, Flanged, Threaded, and Welding End. Retrieved from https://www.asme.org/codes-standards/find-codes-standards/b16-34-valves-flanged-threaded-and-welding-end

[5] Crane Fluid Systems. (n.d.). Valve Selection Guide. Retrieved from https://www.cranebsu.com/docs/default-source/crane-fluid-systems/literature---english/crane-valve-selection-guide.pdf

[6] American Petroleum Institute. (). API Specification 6D - Pipeline Valves. Retrieved from https://www.api.org/products-and-services/standards/api-monogram-licensing/valves/6d

[7] Emerson. (n.d.). Valve Selection Guide. Retrieved from https://www.emerson.com/documents/automation/valve-selection-guide-en-.pdf