Globe Valves Explained

What is a globe valve?

Globe valves obtained their name due to the shape of their spherical valve body, but this is slightly deceptive as globe valves are not the only type of valve with this body shape.

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Globe Valve (globe shaped body)

Globe valves are some of the most common valves currently employed. Other common types include the plug, butterfly, ball and gate type valves.

 

Globe Valve Designs

Globe valves are linear actuated valves and have four main designs:

• Straight Flow - Z-shaped body. Most common type.

Straight Flow

• Angle Flow - r-shaped body. Lower pressure drop than Z-type due to less right angle flow turns.
• Cross Flow - T-shaped body.
• Oblique Flow - Y-shaped body. Lower pressure drop than Z-type. Suitable for higher pressures.

Straight, angle, cross and Y-Flow Globe Valves

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Globe Valve Discs

Globe valve discs utilise three basic disc designs:

• Ball Disc &#; suitable for low temperatures and low pressures. Ideal for start and stop operations. Ill-suited for flow regulation.

Ball Disc

• Composition Disc &#; composites by definition consist of several components. The disc is almost always manufactured from metal whilst a non-metallic ring is mounted onto the disc to form the seating area. The non-metallic ring material is chosen to have good corrosion and erosion characteristics and may be custom made to ensure it is fit for purpose. If the non-metallic ring is chosen correctly, it should allow for better sealing. Composite discs are often employed for steam system applications.

Composition Disc

• Plug Disc &#; plug discs have a long and tapered shape. The shape of the plug disc makes it much more suitable to throttling than the composite and ball disc type designs.

Plug Disc

Globe valves can be mounted so that system pressure is exerted on either side of the disc when the valve is closed, however, usually it is more desirable to keep the system pressure boundary restricted to the valve body and disc when the valve is closed and not on the other side of the disc where the boundary includes the bonnet and packing.

Depending upon which side the system pressure is acting, the globe valve will be either hindered or helped by the system pressure. For example, more force is required to open a globe valve with the system pressure pressing the disc onto the seat than if the system pressure was applied on the underside of the disc where the pressure would &#;help&#; the valve to lift the disc off the seat.

For steam systems, globe valves should be orientated so that steam does not lift the valve disc as it cools (creates a negative pressure).  

 

What are the main parts of a globe valve?

The main parts of a globe valve are the actuator, stem, body, disc, seat, bonnet and some form of sealing arrangement (packing).

The disc seats at a right angle on the seat surfaces and this generally yields a better sealing arrangement compared to gate valves. As the disc is lowered and raised, it is guided by guide vanes, a piston, or the stem.

Packing is installed between the stem and bonnet to ensure the valve does not leak.

Some globe valves connect the stem directly to the disc, but some designs do not. A screw-down non-return (SDNR) valve is one such design where the stem does not connect to the disc. SDNR valves are used for safety critical systems such as ship bilge water systems and boiler feed water systems.

Flanges are installed on the suction and discharge side of the valve so that piping can be easily connected.

 

How do globe valves work?

The below video is an extract from our Introduction to Valves Online Video Course.

A circular shaped disc attached to the main valve stem is lowered and raised in order to open and close the valve. When the valve is closed, the disc sits upon the valve seat with both parts being machined in order to obtain a tight seal; the sealing surface can be flat or mitred. When the valve is opened, the flowing medium flows between the disc and seat.

 

What are the advantages of globe valves?

Due to the circular shape of the disc and seat, uneven wear across machined area is unusual.

Globe valves can be used for throttling (flow control), but the valve does not give a great degree of control due to the large circular shape of the disc. If fine flow adjustments are needed, the globe valve design is probably not the best option.

An angled globe valve has one less right angle turn than a straight globe valve, this leads to a lower pressure drop.

 

What are the disadvantages of globe valves?

Globe valves suffer from a high pressure drop when the valve is throttled and this can lead to damage of the valve&#;s components.

Globe valves are often jammed open due to incorrect operation. Globe valves should be opened fully then the handle should be rotated 180 degrees in the reverse direction to again close the valve slightly. If this &#;winding back&#; procedure does not occur, the valve may seize in the open position and this makes it difficult for operators to ascertain the valve&#;s position; this leads to operators trying to open an already fully open valve and this can lead to the stem breaking/fracturing.

Note: A tell-tale sign that the valve stem is broken, is that the valve handle will rotate much more easily. The handle rotates easily because the disc is no longer connected to the stem.

 

3D Model Components

This 3D model contains all common parts of a globe valve, these include:

• Stem
• Bonnet
• Disc
• Seat
• Packing
• Body

 

Additional Resources

https://en.wikipedia.org/wiki/Globe_valve

http://www.wermac.org/valves/valves_globe-valves_linear-motion-valve.html

In the realm of fluid control systems, precision and reliability are paramount. Among the array of valves available, angle type globe valves stand out as versatile and essential components. In this comprehensive guide, we delve into the intricacies of angle type globe valves, exploring their functionality, components, applications, working principles, and the importance of selecting the right valve for specific needs.

 

What is an Angle Type Globe Valve?

 

An angle type globe valve is a specialized variation of the conventional globe valve, designed with the inlet and outlet ports at an angle to the valve body. This unique configuration enables the valve to be installed in tight spaces or piping systems where straight-through flow is not feasible. Angle type globe valves retain the essential features of globe valves, including a globe-shaped body and a movable disk or plug that controls the flow of fluid through the valve.

 

Components of an Angle Type Globe Valve

 

A typical angle type globe valve comprises several key components, each playing a crucial role in its operation:

 

1. Body: The main housing of the valve, usually made of durable materials such as cast iron, carbon steel, or stainless steel, provides structural integrity and houses the internal components.




2. Disk or Plug: The movable disk or plug controls the flow of fluid through the valve by positioning itself relative to the seat. This component is typically guided by a stem connected to the valve actuator.




3. Seat: The seat forms a seal with the disk or plug when the valve is closed, preventing fluid leakage and ensuring tight shut-off.




4. Actuator: Angle type globe valves are equipped with actuators, such as pneumatic, electric, or hydraulic actuators, which drive the movement of the disk or plug to regulate flow rates based on input signals from control systems.

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   Bonnet: The bonnet forms a seal with the valve body, enclosing the stem and providing access for maintenance and repair operations.




6. Connections: Inlet and outlet connections are positioned at an angle to the valve body, allowing for installation in tight spaces or piping systems with non-linear flow paths.

 

What is an Angle Type Globe Valve Used For?

 

Angle type globe valves find applications in various industries and processes where precise fluid control is essential:

 

1. Limited Space Installations: Angle type globe valves are ideal for installations where space constraints or piping configurations make it impractical to use straight-through valves.

 

2. High Pressure Drop Systems: The design of angle type globe valves allows for efficient flow regulation in high-pressure drop applications, such as boiler feedwater systems and steam distribution networks.

 

3. Process Control: Angle type globe valves are used to modulate flow rates, pressure levels, and process variables in chemical processing, petrochemical, and refining industries.

 

4. Water and Wastewater Treatment: Angle type globe valves are employed in water treatment plants, pumping stations, and distribution networks to regulate flow rates and control process variables during treatment and distribution processes.

 

How Does an Angle Type Globe Valve Work?

 

The operation of an angle type globe valve is similar to that of a conventional globe valve, with some variations due to its angled inlet and outlet ports. The process typically unfolds as follows:

 

1. Opening: When the actuator receives a signal to open the valve, it exerts force on the valve stem, lifting the disk or plug away from the seat. This creates a flow path for the fluid to pass through the valve at an angle to the valve body.

 

2. Modulation: As the actuator adjusts the position of the disk or plug, the flow area between the disk or plug and the seat changes, resulting in a proportional modulation of flow rates. This allows for precise control of fluid flow within the system, even in limited space installations.

 

3. Closing: When the actuator receives a signal to close the valve, it moves the disk or plug towards the seat, gradually reducing the flow area until the valve is fully closed, stopping the flow of fluid through the system.

 

Why Use an Angle Type Globe Valve?

 

Angle type globe valves offer several advantages that make them the preferred choice for specific applications:

 

1. Space Efficiency: The angled inlet and outlet ports of angle type globe valves allow for compact installation in tight spaces or piping systems with non-linear flow paths, maximizing space efficiency.

 

2. High Pressure Drop Capability: The design of angle type globe valves makes them suitable for applications with high-pressure drops, providing efficient flow regulation and control.

 

3. Versatility: Angle type globe valves retain the versatility of conventional globe valves, making them suitable for a wide range of fluid control applications across various industries.

 

4. Reduced Pressure Loss: The angled flow path of angle type globe valves reduces pressure loss compared to straight-through valves, improving system efficiency and performance.

 

5. Reliability: Engineered with robust materials and precision manufacturing techniques, angle type globe valves offer reliable performance even in demanding operating conditions, ensuring uninterrupted operation and minimal downtime.

 

Technical Difficulties of Producing an Angle Type Globe Valve

 

While angle type globe valves offer numerous benefits, their production presents several technical challenges:

 

1. Complex Design: The unique design of angle type globe valves requires precision engineering and machining to ensure proper alignment of the angled inlet and outlet ports, as well as the disk or plug and seat components.

 

2. Sealing Technology: Developing effective sealing solutions to prevent leakage and ensure a tight shut-off, particularly in high-pressure applications, demands advanced sealing materials and design considerations.

 

3. Actuator Integration: Integrating actuators with angle type globe valves while maintaining compatibility with control systems and ensuring reliable operation under varying conditions requires meticulous engineering and testing.

 

4. Material Selection: Choosing materials that can withstand high-pressure, high-temperature, and corrosive environments is critical to the performance and longevity of angle type globe valves, necessitating careful material selection and testing.

 

5. Quality Control: Ensuring dimensional accuracy, surface finish, and tight tolerances during manufacturing is essential to the performance and reliability of angle type globe valves, requiring rigorous quality control measures throughout the production process.

 

How to Choose the Right Angle Type Globe Valve

 

Selecting the appropriate angle type globe valve for a specific application involves considering several key factors:

 

1. Space Constraints: Evaluate the available space and piping configuration to determine the appropriate angle type globe valve size and orientation for optimal installation and operation.

 

2. Flow Requirements: Consider the flow rates, pressure levels, and fluid properties to select an angle type globe valve with the appropriate flow capacity and pressure rating to meet the application requirements.

 

3. Actuation Method: Choose the actuation method (pneumatic, electric, hydraulic) based on control system compatibility, operational requirements, and environmental conditions.

 

4. Material Compatibility: Verify that the selected angle type globe valve materials are compatible with the fluid being controlled and can withstand the operating conditions, including temperature, pressure, and chemical exposure.

 

5. Reliability and Maintenance: Select angle type globe valves from reputable suppliers like Athena Engineering S.R.L, known for their reliability, durability, and ease of maintenance, to minimize downtime and ensure long-term performance.

 

6. Regulatory Compliance: Ensure that the selected angle type globe valve complies with relevant industry standards, regulations, and certification requirements, particularly in safety-critical applications or regulated industries.

 

Leaders in Industrial Solutions - Athena Engineering S.R.L

 

Before delving into the specifics of angle type globe valves, it's essential to introduce Athena Engineering S.R.L, a prominent supplier of industrial products and engineering services. Headquartered in Italy, Athena Engineering has evolved from a regional valve & level gauge manufacturer to a global conglomerate, owing to years of relentless exploration and innovation. With subsidiaries such as brand Athena for valve & level gauge systems, brand GE-STAR for pumps, brand ROSITATECH for controlling instruments, and brand ASAPHTECH for filtration systems, Athena Engineering caters to various industries worldwide, offering comprehensive solutions for power generation, oil & gas, pulp & paper, water & wastewater management, mining & metallurgy, food & beverage production, process control, and automation in the chemical industry.

 

Conclusion

 

In conclusion, angle type globe valves offer a versatile and efficient solution for fluid control applications in industries where space constraints, high-pressure drops, or complex piping configurations pose challenges. As a leading supplier of industrial products and engineering services, Athena Engineering S.R.L stands at the forefront of innovation and quality in the realm of angle type globe valves. By understanding the components, applications, working principles, technical challenges, and selection criteria outlined in this guide, industrial operators can make informed decisions and choose the right angle type globe valve to meet their specific requirements, ensuring optimal performance, efficiency, and reliability across diverse industries and applications.

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