Globe Valve - FCT Valve

Globe valves are used to regulate the flow of a fluid and to shut-off the fluid (even if for shut-off operations ball valves and gate valves shall always be preferred). Globe valves are bi-directional valves, differently from check valves, meaning that the fluid can flow either way within the valve.

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The image illustrates how the valve works and its main components: basically, the flow is managed via a disc that can be lifted (manually or via actuators) from the seat, thus regulating the volume of the allowed flow.

The key specifications for globe valves used for piping applications in the petrochemical industry are:

• BS : cast steel valves
• API 603: stainless steel valves
• API 602/BS : forged steel valves
• API 598 and BS EN -1: valves testing
• ASME B16.10: face to face dimensions for valves
• ASME B16.5 and ASME B16.47: flanged connections
• ASME B16.25: butt weld connections design
• ASME B16.34: pressure and temperature ratings by material grade

GLOBE VALVE ADVANTAGES AND DISADVANTAGES.

The advantages are:

• Good throttling and shut-off capabilities
• Easy to maintain and resurface the seats
• Can be used as a stop-check valve in case the disc is not attached to the stem

The main disadvantages are:

• the valve creates a pressure drop in the piping system (different from gate valves): this is due to the fact that the flow of the fluid is not linear inside the valve, which has an “S-shaped” passageway (see the image below)
• shut-off requires more torque than gate valves

GLOBE VALVE TYPES

The valve is available in three main types, considering the shape of the body:

• straight or “T” type
• angle or “90 degrees”
• Y pattern or “wye globe valve”

The globe valve symbol in P&ID diagrams is the following:  

GLOBE VALVE VS BALL VALVE

The key difference between a globe and a ball valve is that a ball valve is designed, mainly, for shut-off operations, whereas a globe valve is designed, mainly, to throttle fluids. These two valves are industry-standards respectively for shut-off (ball valve) and for regulation (globe valve) applications.

A globe valve does not fit shut-off operations, due to the pressure drop it creates in the piping system (a problem that does not exist for full bore ball valves).

Ball valves have a long service life even in case of continuous on-off operations; globe valves would deteriorate easily under this type of service.

GLOBE VALVE VS GATE VALVE

The main differences between these two valves are:

• fluid shut off is the main goal of gate valves, whereas flow throttling is the main goal of globe valves
• gate valves have poor, to none, fluid regulation capacity
• gate valves do not generate a pressure drop in the pipeline, globe valves do
• globe valves open faster than gate valves

Concluding on this topic: use a ball valve (or a gate valve) for shut-off operations; use a globe valve for regulation. Do not consider these valves as interchangeable.

GLOBE VALVE DIAGRAM

A general assembly drawing for globe valves is shown in the image:

Nonetheless, a large number of variations exist, depending on the following factors:

• body material: cast (BS ) and forged (API 602/BS )
• bonnet design: standard or pressure seal type (for high-pressure applications)
• bonnet to body connection: bolted or welded
• valve end connections type: flanged (as shown in the image), buttweld, socket weld/threaded (forged bodies)
• disc type
• stem type (rising/non-rising)
• seal type: conical or flat
• specification: BS, API, EN
• type of actuation: manual, with a gearbox, with an actuator

GLOBE VALVES DIMENSIONS

The tables show the dimensions and weights of BS valves, bolted bonnet type.

CLASS 150

Dimensions in inches (millimeters)

CLASS 300

Dimensions in inches (millimeters)

CLASS 600

Dimensions in inches (millimeters)

CLASS 900

Dimensions in inches (millimeters)

GLOBE VALVE DIMENSION CLASS

Dimensions in inches (millimeters)

GLOBE VALVE DIMENSION CLASS

Dimensions in inches (millimeters)

What is Cast Steel Globe Valves

Cast steel globe valves are a type of valve widely used in various industries for controlling flow within a pipeline. They consist of a globe-shaped body with an internal baffle and a movable disc or plug that regulates flow by raising or lowering in response to the position of the valve stem. This design allows precise control of flow rate and pressure, making cast steel globe valves suitable for applications requiring throttling or isolation. The cast steel construction provides durability and strength, making these valves capable of withstanding high pressures and temperatures.

Advantages of Cast Steel Globe Valves

01/

Excellent flow control
Cast steel globe valves offer precise flow control capabilities, allowing for accurate regulation of fluid flow rates and pressures across a wide range of operating conditions. Their design enables throttling of the flow by adjusting the position of the disc or plug, making them ideal for applications requiring fine-tuned control.

02/

Versatility in applications
These valves are highly versatile and suitable for various industries and applications. They can handle a wide range of fluids, including steam, water, oil, and gases, making them indispensable in industries such as oil and gas, petrochemical, power generation, HVAC, and water treatment.

03/

Robust construction
Cast steel globe valves are constructed from durable materials such as cast steel, which provides excellent strength, corrosion resistance, and durability. This robust construction allows the valves to withstand high-pressure and high-temperature environments, ensuring reliable performance and longevity in demanding applications.

04/

Bi-directional sealing
Unlike some other types of valves, cast steel globe valves offer bi-directional sealing, meaning they can effectively prevent backflow in both directions. This feature enhances system integrity and safety by ensuring that fluid flow is controlled and regulated as intended, minimizing the risk of leaks or contamination.

05/

Ease of maintenance
Cast steel globe valves are designed for ease of maintenance, with accessible internal components that can be easily inspected, repaired, or replaced as needed. Routine maintenance tasks such as lubrication, packing adjustments, and seal replacements can be performed efficiently, reducing downtime and maintenance costs.

06/

Wide range of sizes and pressure ratings
These valves are available in a wide range of sizes and pressure ratings to suit diverse application requirements. Whether for small-scale residential systems or large-scale industrial processes, cast steel globe valves can be selected in various sizes and pressure classes to meet specific flow rate and pressure control needs.

 

What Types of Fluids can Cast Steel Globe Valves Handle?
Cast steel globe valves are versatile and can handle a wide range of fluids, including liquids, gases, and steam. They are suitable for controlling the flow of various fluids, including water, oil, gas, steam, chemicals, and slurries. The robust construction of cast steel globe valves, along with their reliable sealing mechanisms, enables them to withstand different fluid properties and operating conditions, making them indispensable for fluid control applications across diverse industries.

 

How do Cast Steel Globe Valves Contribute to Flow Control in Pipelines?
Cast steel globe valves contribute to flow control in pipelines by providing precise regulation of fluid flow rates and pressures. Their design allows for throttling of the flow by adjusting the position of the disc or plug, enabling operators to finely control the flow according to system requirements. By raising or lowering the disc or plug, the valve can increase or decrease the flow area, thereby adjusting the flow rate. This capability is essential for maintaining optimal flow conditions, preventing pressure surges, and ensuring efficient operation of the pipeline system. Cast steel globe valves offer excellent sealing properties, minimizing leakage and ensuring reliable flow control over extended periods of operation.

 

What are The Pressure Ratings and Sizes Available for Cast Steel Globe Valves?
Pressure ratings typically range from ANSI Class 150 to Class or higher, allowing these valves to handle varying levels of pressure within industrial systems. As for sizes, cast steel globe valves come in a variety of diameters, ranging from small sizes suitable for residential or light industrial use to larger sizes used in heavy-duty industrial applications. The availability of different pressure ratings and sizes ensures that cast steel globe valves can be selected to match specific flow rate, pressure, and piping requirements, making them versatile and widely applicable across various industries.

 

Are Cast Steel Globe Valves Suitable for Both On/Off and Throttling Applications?
Cast steel globe valves are suitable for both on/off and throttling applications. Their versatile design allows for precise control of fluid flow rates and pressures, making them ideal for applications where throttling is required to regulate flow. Additionally, they can effectively shut off flow completely when fully closed, making them suitable for on/off applications where fluid isolation is necessary.

How to Choose Cast Steel Globe Valves

1

Fluid compatibility
Determine the type of fluid the valve will handle, including its temperature, pressure, and corrosiveness. Ensure that the materials of construction are compatible with the fluid to prevent corrosion and ensure long-term reliability.

2

Pressure and temperature ratings
Consider the maximum pressure and temperature of the fluid in the system. Select a valve with appropriate pressure and temperature ratings to ensure safe and reliable operation under the expected conditions.

3

Valve size
Determine the required valve size based on the flow rate and pipe diameter of the system. Ensure that the valve size matches the requirements of the application to facilitate efficient fluid flow and minimize pressure drop.

4

End connections
Choose the appropriate end connections for the valve based on the piping system configuration. Common end connection options include flanged, threaded, and welded connections. Ensure compatibility with existing piping infrastructure.

5

Valve design
Consider the specific design features required for the application, such as globe or angle pattern, bolted or pressure seal bonnet, and type of disc or plug. Select a valve design that best suits the flow control requirements and installation constraints.

6

Sealing material
Pay attention to the type of sealing material used in the valve, such as metal-to-metal, graphite, or soft sealing. Ensure that the sealing material is compatible with the fluid and operating conditions to prevent leakage and ensure tight shut-off.

7

Actuation method
Determine the preferred actuation method for the valve, such as manual, electric, pneumatic, or hydraulic actuation. Choose an actuation method that meets the automation and control needs of the system while ensuring ease of operation and reliability.

What is The Maximum Operating Temperature of Cast Steel Globe Valve?

Cast steel globe valves are suitable for handling temperatures ranging from -29°C to 425°C (-20°F to 800°F). However, this temperature range can vary depending on factors such as the type of fluid being controlled, the pressure rating of the valve, and any additional features or coatings applied to enhance temperature resistance.

What are Common Causes of Leaks in Cast Steel Globe Valves?

Common causes of leaks in cast steel globe valves can include issues such as damage or deterioration of sealing surfaces, worn or degraded valve components, improper installation, excessive pressure or temperature, corrosion or erosion of valve internals, and inadequate maintenance. These factors can compromise the integrity of the valve's sealing mechanism, allowing fluid to escape or leak through the valve when it should be fully closed. Regular inspection, maintenance, and prompt repair of damaged components are essential to prevent leaks and ensure the reliable performance of cast steel globe valves.

How do I Test a Cast Steel Globe Valve for Proper Operation?

1

Visual inspection
Start by visually inspecting the valve for any signs of damage, corrosion, or defects. Check the valve body, bonnet, stem, disc, and seating surfaces for any abnormalities that may affect performance.

2

Leak test
Perform a leak test to ensure that the valve provides a tight seal when closed. Close the valve and apply a test pressure to the inlet side while blocking the outlet side. Monitor for any signs of leakage at the valve body, bonnet, or packing gland. If leakage is detected, investigate and address the source of the leak before proceeding.

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Stroke test
Verify that the valve operates smoothly and opens and closes fully without sticking or binding. Open the valve fully, then close it completely, ensuring that the disc or plug moves freely throughout the stroke. Listen for any unusual noises that may indicate mechanical issues.

4

Flow test
If applicable, perform a flow test to verify that the valve provides the desired flow rate and pressure drop characteristics. Install the valve in the system and measure the flow rate and pressure differential across the valve at various operating conditions.

5

Sealing test
Test the sealing integrity of the valve by applying a test pressure to the outlet side while blocking the inlet side. Verify that the valve maintains a tight seal against backflow and does not allow leakage past the disc or plug.

6

Functional test
Finally, conduct a comprehensive functional test to ensure that the valve operates as intended under simulated operating conditions. Open and close the valve multiple times while monitoring for proper response, sealing, and performance.

 

What are the Differences Between Trim Designs in Cast Steel Globe Valves?
The differences between trim designs in cast steel globe valves primarily lie in the configuration and materials of the internal components, such as the disc, seat, and stem. Trim designs vary based on factors like the intended application, fluid characteristics, pressure, and temperature requirements. Common trim designs include single-seat, double-seat, and balanced plug configurations. Single-seat trim designs feature a single seating surface between the disc and seat, providing tight shut-off and reliable sealing. Double-seat trim designs incorporate two seating surfaces for improved sealing and reduced leakage. Balanced plug trim designs use a combination of disc and seat designs to minimize operating torque and enhance control performance.

 

How do I Replace The Seals or Seats in a Cast Steel Globe Valve?
First, the valve must be isolated and depressurized to ensure safety. Then, the valve bonnet is removed to access the internals. The old seals or seats are carefully removed, and any debris or deposits are cleaned from the valve body and components. New seals or seats are installed, ensuring proper alignment and fit. Finally, the valve is reassembled, and the bonnet is securely tightened to the specifications. Proper testing and inspection should be conducted to verify the integrity and functionality of the replaced seals or seats before returning the valve to service.

 

Material of Cast Steel Globe Valves
Cast steel globe valves are typically constructed using cast steel materials, known for their durability, strength, and resistance to corrosion. The cast steel used in these valves is usually composed of carbon steel, alloy steel, or stainless steel, depending on the specific application requirements and operating conditions. Carbon steel offers excellent mechanical properties and is suitable for general-purpose applications, while alloy steel provides enhanced strength and corrosion resistance, making it ideal for high-pressure and high-temperature environments. Stainless steel is preferred for applications requiring superior corrosion resistance and hygiene, such as in the food and pharmaceutical industries.

Application of Cast Steel Globe Valves

1

Oil and gas industry
Cast steel globe valves are used in upstream, midstream, and downstream operations for controlling the flow of crude oil, natural gas, and refined products. They are employed in pipelines, refineries, petrochemical plants, and drilling operations.

2

Power generation
In power plants, cast steel globe valves regulate the flow of steam, water, and other fluids in boiler systems, turbine bypass lines, feedwater systems, and cooling water circuits. They help maintain optimal operating conditions and ensure efficient power generation.

3

Chemical processing
Cast steel globe valves are vital in chemical processing plants for handling a wide range of corrosive, abrasive, and hazardous fluids. They are used in reactors, distillation columns, heat exchangers, and chemical storage facilities.

4

Water treatment
Municipal and industrial water treatment facilities utilize cast steel globe valves for controlling the flow of water, chemicals, and wastewater. They are employed in pumping stations, filtration systems, desalination plants, and wastewater treatment plants.

5

HVAC systems
Heating, ventilation, and air conditioning (HVAC) systems incorporate cast steel globe valves for regulating the flow of hot water, chilled water, and refrigerant. They help maintain indoor comfort conditions in commercial buildings, hospitals, hotels, and residential complexes.

6

Pulp and paper industry
In pulp and paper mills, cast steel globe valves regulate the flow of chemicals, steam, and pulp slurries in various processing stages. They are employed in digester systems, paper machines, recovery boilers, and wastewater treatment facilities.

7

Food and beverage
In the food and beverage industry, cast steel globe valves are employed for handling sanitary fluids, such as water, steam, and food-grade liquids. They are used in processing, packaging, and distribution facilities to ensure product quality and safety.

8

Pharmaceutical and biotech
Pharmaceutical and biotechnology companies rely on cast steel globe valves for controlling the flow of purified water, sterile fluids, and pharmaceutical ingredients in manufacturing processes. They are used in cleanroom environments and comply with stringent regulatory standards.

Components of Cast Steel Globe Valves

Cast steel globe valves consist of several key components, including the valve body, bonnet, disc or plug, stem, and seating surfaces. The valve body serves as the main housing, containing the internal components and providing connection points for piping. The bonnet encloses the valve internals and provides a seal against leakage. The disc or plug is a movable component that regulates flow by opening or closing against the seating surfaces. The stem connects the actuator to the disc or plug, allowing for manual or automated operation. Seating surfaces are precision-machined areas where the disc or plug makes contact to create a seal, preventing fluid leakage when the valve is closed.

What is The Difference Between a Bolted Bonnet and a Top Entry Cast Steel Globe Valve?

The main difference between a bolted bonnet and a top entry cast steel globe valve lies in their design and construction. In a bolted bonnet globe valve, the bonnet is attached to the valve body using bolts and nuts, allowing for easy removal of the bonnet for maintenance or repair. A top entry cast steel globe valve features a single-piece body with a top-mounted bonnet, which can be removed by unbolting it from the valve body. This design simplifies maintenance and inspection as the entire internals of the valve, including the disc, stem, and seating, can be accessed from the top without removing the valve from the pipeline. Top entry globe valves are often preferred for applications where frequent maintenance or inspection is required, as they offer quicker and easier access to internal components compared to bolted bonnet valves.

How to Maintain Cast Steel Globe Valves

What Should you Pay Attention to When Operating Cast Steel Globe Valves?

Valve position
Ensure that the valve is in the correct position for the desired flow direction. Globe valves typically have a stem that moves perpendicular to the flow direction to open or close the valve. Verify that the valve is fully open or fully closed as required for the intended operation.

Operating environment
Consider the operating environment, including temperature, pressure, and fluid characteristics. Cast steel globe valves are designed to withstand high pressures and temperatures, but it's essential to operate them within their specified limits to avoid damage or failure.

Smooth operation
Operate the valve smoothly and avoid excessive force when opening or closing it. Applying excessive force can damage internal components or cause the valve to malfunction. Use the valve handwheel or actuator as specified by the manufacturer for optimal operation.

Controlled flow
Globe valves are often used for throttling or regulating flow. When adjusting the flow rate, do so gradually and in small increments to avoid sudden changes in pressure or flow velocity, which can lead to water hammer, vibration, or cavitation.

Seal integrity
Check the sealing integrity of the valve regularly to ensure that it remains leak-tight. Inspect the valve seats, disc, and packing gland for signs of wear, corrosion, or damage. Replace any worn or damaged components promptly to maintain proper sealing and prevent leakage.

Working Principle of Cast Steel Globe Valves

The working principle of cast steel globe valves involves the regulation of fluid flow by the movement of a disc or plug within a globe-shaped body. When the valve is in the open position, fluid flows through the valve freely. However, when the valve is closed, the disc or plug is forced against the valve seat by the pressure of the fluid, effectively sealing off the flow. This design allows for precise control of flow rates by adjusting the position of the disc or plug relative to the seat, making cast steel globe valves ideal for applications requiring throttling or isolation. 

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FAQ

Q: What are cast steel globe valves used for?

A: Cast steel globe valves are used for controlling the flow of gases, liquids, and viscous fluids in various industrial applications. They provide precise throttling and shut-off capabilities.

Q: What materials are cast steel globe valves typically made from?

A: These valves are primarily made from carbon steel, stainless steel, alloy steels, or ductile iron, depending on the application's requirements for strength, corrosion resistance, and temperature tolerance.

Q: What is the working principle of a cast steel globe valve?

A: The valve operates by lifting the internal plug away from the seat to allow fluid passage. When the valve is closed, the plug presses against the seat, creating a seal to stop the flow.

Q: How do you select the right size of a cast steel globe valve?

A: Selecting the right size involves considering the flow rate, pressure, temperature, and the type of fluid being controlled. The valve size is usually determined by calculating the required CV (flow coefficient) value.

Q: What are the common applications of cast steel globe valves?

A: Common applications include oil and gas processing, chemical plants, power generation, water treatment facilities, and pulp and paper mills.

Q: What are the advantages of using a cast steel globe valve over a gate valve?

A: Globe valves offer better control over flow, can be used for throttling, and have a lower risk of erosion due to their internal design, whereas gate valves are mainly used for open-close operations and are not suitable for throttling.

Q: What are the different types of globe valves based on their construction?

A: There are three main types: angle globe valves, globe valves with a yoke, and globe valves with a union body. Each type has its own specific use and connection method.

Q: What is the difference between a cast steel globe valve and a forged steel globe valve?

A: Cast valves are made by pouring molten metal into a mold, while forged valves are formed by heating and then hammering or pressing metal into shape. Forged valves are generally stronger and more durable.

Q: Can cast steel globe valves be used in high-temperature applications?

A: Yes, they can be used in high-temperature applications, but the specific temperature limit depends on the material of construction and heat treatment of the valve.

Q: What is the typical pressure rating of cast steel globe valves?

A: The pressure rating can vary widely, from around 150 psi to several thousand psi, depending on the design and materials used in construction.

Q: How do you maintain cast steel globe valves?

A: Regular maintenance includes inspecting for corrosion, leaks, and wear. Valves should be cleaned, lubricated, and operated periodically to prevent seizure.

Q: What is the life expectancy of a cast steel globe valve?

A: The life expectancy can be several decades with proper maintenance and operation. It largely depends on the operating conditions and the quality of the materials used.

Q: Can cast steel globe valves be used for slurry applications?

A: Yes, but they must be designed with appropriate features such as hardened seats and sturdy construction to handle abrasive particles.

Q: Are cast steel globe valves suitable for cryogenic applications?

A: Specialized cast steel globe valves with materials and designs suitable for low temperatures can be used in cryogenic applications.

Q: What is the effect of vibration on cast steel globe valves?

A: Excessive vibration can damage the valve's internal components and reduce its service life, so it's important to ensure proper support and alignment.

Q: How do you determine the flow direction in a cast steel globe valve?

A: The flow direction is typically indicated by arrows on the valve body. It's crucial to install the valve in the correct orientation to ensure proper function.

Q: What is the importance of the seat material in a cast steel globe valve?

A: The seat material must be compatible with the process fluid to prevent corrosion and ensure a tight seal. Common seat materials include stainless steel, hardened metals, or soft materials like PTFE.

Q: What is the purpose of the stem extension in a cast steel globe valve?

A: The stem extension allows for easier access to the valve handwheel, especially in situations where the valve is located below ground or in a difficult-to-reach location.

Q: Can cast steel globe valves be automated?

A: Yes, they can be equipped with actuators for automation. Actuators can be electric, pneumatic, or hydraulic, depending on the system requirements.

Q: What are the common causes of valve failure in cast steel globe valves?

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A: The common causes include corrosion, erosion, mechanical wear, improper installation, and operational errors such as over-tightening or incorrect positioning.