What Are Bellows Seal Globe Valves?

Bellows seal globe valves are specially engineered valves designed to provide exceptional sealing capabilities, particularly crucial in industries where even minute leaks can lead to severe consequences. These valves are critical in sectors dealing with hazardous substances, such as the chemical, petrochemical, and nuclear industries, where they help prevent leakages that could lead to explosions, health hazards, or environmental contamination.



How Do Bellows Seal Globe Valves Work?

Bellows seal globe valves operate by employing a unique sealing mechanism involving metal bellows. Here's a breakdown of their operation:

Sealing Mechanism:

The valve includes a metal bellows that is welded at its lower end to the valve stem. This design prevents the system fluid from corroding the stem.

The upper end of the bellows is affixed between the valve body and the cover, creating a hermetic seal that eliminates leaks.

This double-seal system ensures that even if the bellows fail, the secondary stem packing will prevent leakage, maintaining operational integrity.

Operating Efficiency:

The metal bellows are welded to the valve stem, which stabilizes the valve’s operation and minimizes the risk of stem vibration, ensuring reliable performance.

Key Components of Bellows Seal Globe Valves

The key components of a bellows seal globe valve include:

Metal Bellows: The bellows are the core feature, typically made from corrosion-resistant and temperature-tolerant materials like Inconel. They are formed by rolling a sheet into a tube and then shaping it into a bellows with rounded folds.

Stem and Lower End Assembly: The lower end of the bellows is welded to the valve stem, creating a secure and leak-proof connection.

Upper End and Connecting Plate: The upper end is welded to a connecting plate using a socket weld, ensuring a robust seal between the fluid and the environment.

Sealing Surface: The valve disc and structure are precision-ground to ensure a tight seal, and graphite packing is used to prevent leaks.

Industries Using Bellows Seal Globe Valves

Bellows seal globe valves are vital in industries requiring stringent sealing due to the handling of hazardous materials. Key industries include:

Petrochemical Industry: These valves are crucial for controlling the flow of flammable and hazardous substances, preventing leaks that could lead to accidents or environmental damage.

Nuclear Industry: Extensively used to manage radioactive materials, their double-seal design is essential to prevent any leakage of radioactive substances, ensuring plant safety.

Chemical Industry: Ideal for managing corrosive chemicals at high temperatures, ensuring leak-free operations in chemical production processes.

Electronics and Other Industries: Used in semiconductor manufacturing and in plants like power and water treatment facilities, where they control gas and liquid flows. The vacuum industry also utilizes these valves for maintaining high sealing under low pressure.

Advantages of Bellows Seal Globe Valves

Exceptional Sealing Performance: The double-seal design, comprising bellows and stem packing, ensures zero leakage, which is critical for handling hazardous substances.

Safety and Environmental Protection: By minimizing fluid loss, these valves enhance plant safety and prevent environmental pollution.

Energy Conservation: The elimination of leakage reduces energy losses, leading to cost savings and supporting environmental sustainability goals.

Durability and Cost Savings: Their robust design leads to reduced maintenance and longer valve life, resulting in significant cost savings.

Maintenance-Free Operation: The sturdy bellows seal ensures a leak-free stem, improving operational efficiency and reducing maintenance needs.

Types of Bellows Seal Globe Valves

Welded Ends Bellows Seal Globe Valve: Features welded ends for a leak-proof connection, suitable for high-pressure applications.

Flanged Bellows Seal Globe Valve: Has flanged ends for easy installation and removal, ideal for applications requiring regular maintenance.

Socket-Welded Bellows Seal Globe Valve: With socket-welded ends, it offers a strong connection, perfect for high-pressure scenarios.

Threaded Bellows Seal Globe Valve: Equipped with threaded ends for easy installation, suitable for low to medium pressure applications.

Extended Bellows Seal Globe Valve: Provides additional protection with an extended bellows seal, suitable for applications needing high sealing performance.

Y Pattern Bellows Seal Globe Valve: Features a Y pattern body for streamlined fluid flow, ideal for high flow rate applications.

How to Select the Right Bellows

Inner Diameter: Should be greater than the stem diameter, typically 115 mm, to allow free stem movement.

Outer Diameter: Selected based on the inner diameter, usually with an outer-to-inner diameter ratio between 113 and 115.

Wall Thickness, Number of Layers, Corrugations, and Length: Specifications should meet the requirements for pressure resistance, stroke, and cycle life, ensuring the bellows can handle operational pressures and temperatures.

Bellows Design: For higher pressures, a multiply design using 2 or 3 layers of metal is recommended.

In conclusion, bellows seal globe valves are indispensable in industries requiring high sealing standards to prevent hazardous leaks and ensure operational safety. Their robust design and versatile types make them suitable for a range of applications, ensuring efficient and reliable performance across various industrial settings.