Advantages and disadvantages of globe valve

Definition of Globe Valve

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A globe valve is defined as a valve that has an opening and closing member (valve disk) driven by the valve stem, which moves linearly along the axis of the valve seat (sealing surface).

Typically, a globe valve consists of essential components such as a handwheel, valve stem, valve body, valve cover, valve disk (closure), packing assembly, and other major parts. The handwheel is connected to the valve stem, which in turn drives the valve disk. This mechanism allows the disk to move reciprocally along the valve seat axis, thereby opening or closing the pipeline.

Globe valves are widely utilized in high-pressure and smaller caliber applications, generally made for sizes up to DN400 (NPS 16). Larger diameter specifications are produced only for special pipelines. For example, in large oxygen pipelines, a significant risk of static fire due to friction with other valves necessitates the use of a large-diameter stainless steel globe valve.

The Working Principle of Globe Valves

Globe valves typically perform a rotary lifting movement, with the handwheel fixed at the top of the stem. Rotating the handwheel clockwise causes the stem threads to rotate downwards, resulting in the valve sealing surface making contact with the valve seat sealing surface, thus closing the valve. Conversely, rotating the handwheel counterclockwise allows the stem threads to rotate upwards, disengaging the sealing surfaces and opening the valve.

Advantages of Globe Valves:

• Compared to gate valves, globe valves have a simpler structure, usually featuring only one sealing surface on the valve body and disk. This results in a small sealing area, conserving valuable materials and reducing costs.
• The sealing surface experiences minimal wear, leading to good sealing performance and durability, as there is no relative sliding except for conical sealing surfaces.
• Globe valves typically require a small opening height, generally only 1/4 of the diameter of the valve seat channel, which aids in saving installation space.
• They allow for precise flow control, making them ideal for applications requiring accurate fluid flow regulation.
• Globe valves have a high-pressure rating, suitable for applications where pressure is a critical concern.
• They possess excellent shutoff capability, ensuring tight closure to prevent fluid flow in both directions.
• Globe valves are versatile, accommodating a wide range of fluids including gases, liquids, and slurries, and find use across various industries.
• With proper maintenance, globe valves exhibit a long lifespan and are less prone to leakage, preventing potential damage.

Disadvantages of Globe Valves:

• Globe valves are known for creating significant pressure drops across the valve when fully opened, potentially reducing system efficiency and necessitating additional energy input.
• Their size and weight make globe valves bulkier compared to other valve types, complicating installation and requiring more robust support structures.
• Due to the manufacturing complexity, globe valves can be more expensive than other valve types.
• The presence of multiple internal components increases the likelihood of wear or damage over time, necessitating more frequent maintenance.
• In high-flow applications, globe valves may experience cavitation and erosion, limiting their suitability.

Classes of Globe Valves:

• Based on design: T-pattern, Y-pattern, and angle pattern globe valves, each with unique characteristics for flow control.
• Based on material: Available in stainless steel, carbon steel, bronze, brass, and cast iron, the choice depends on the type of fluid, pressure, temperature, and durability requirements.
• Based on the valve stem: Types include rising stem, non-rising stem, and rotary stem.
• Based on the number of ports: Includes single-port and double-port options, allowing for varied flow path configurations.
• Based on the operating mechanism: Options include manual, electric, pneumatic, hydraulic, or solenoid-operated valves.

Suitable Application Conditions for Globe Valves:

• High-pressure applications where risk of fluid escape is a concern.
• Precise flow control in various process fluids.
• High-temperature applications resistant to other valve types.
• Corrosive or abrasive fluids, with materials compatible with the process.
• Liquid services such as in water treatment or chemical processing.
• Effective control in essential process conditions like pressure and flow.
• Ability to handle high-viscosity fluids like slurries with precision.

Overall, globe valves are ideal for applications requiring precise control, reliable shutoff capability, and adaptable flow rates. They provide precise adjustments in fluid flow and are dependable for controlling pressure and temperature in piping systems.