The Working Principle of a Globe Valve

           A globe valve, commonly referred to in Chinese as a “截止阀,” is one of the most widely used types of valves in industrial piping systems. Its primary function is to regulate, start, and stop the flow of fluid within a pipeline. Unlike other valve types such as gate valves or ball valves, a globe valve is especially suited for applications where precise throttling and frequent operation are required. To fully understand its importance, it is useful to explore its structure, working mechanism, and operational advantages.

Basic Structure

           The globe valve derives its name from its generally spherical body shape. Although modern designs may vary, the internal structure still follows the same functional concept. A typical globe valve consists of several key components: the valve body, bonnet, stem, disc (or plug), and seat.

• Valve body: This is the main pressure boundary of the valve, typically manufactured from steel, stainless steel, or other alloys suitable for the working fluid.
• Bonnet: Attached to the valve body, the bonnet encloses the stem and provides a sealing surface.
• Stem: The stem connects the handwheel or actuator to the disc, transferring motion to control the fluid flow.
• Disc or plug: This component moves vertically in relation to the seat, enabling the regulation of fluid passage.
• Seat: The disc presses against the seat to achieve complete shutoff.

              The flow path within a globe valve is not straight but rather changes direction, usually by 90 degrees, as it passes through the valve chamber. This unique design is central to the valve’s working principle.

Working Mechanism

              The operation of a globe valve is relatively simple but highly effective. When the operator turns the handwheel, the stem moves in a linear motion due to its threaded connection. This linear movement raises or lowers the disc relative to the seat.

• When the valve is fully open, the disc is lifted completely away from the seat, allowing fluid to pass through the valve body. However, because the flow path changes direction inside the valve, there is always some resistance, resulting in a higher pressure drop compared with straight-through valves like gate or ball valves.
• When the valve is fully closed, the disc is pressed tightly against the seat, preventing any flow. This tight seal is one of the reasons why globe valves are preferred in applications requiring reliable shutoff.
• When the valve is partially open, the gap between the disc and seat allows for controlled fluid flow. This feature makes globe valves ideal for throttling and regulating purposes. Operators can fine-tune the position of the disc to achieve the desired flow rate, which is particularly valuable in process industries.

The linear motion of the disc, combined with the angled flow path, ensures that adjustments can be made with accuracy and repeatability.

Flow Characteristics

            One of the distinguishing characteristics of a globe valve is its linear flow relationship. This means that the flow rate is approximately proportional to the disc lift. For operators and engineers, this predictable behavior simplifies process control. Unlike gate valves, which are primarily suited for on–off functions, globe valves allow intermediate positions that correspond to stable flow rates.

            However, because the fluid must change direction inside the valve, turbulence is created. This results in a higher pressure drop compared to other valve types. While this may be considered a disadvantage in some cases, the trade-off is the superior throttling ability.

Advantages of Globe Valves

1. Excellent throttling capability: Globe valves are particularly effective in regulating flow, making them suitable for applications where precision is critical.
2. Reliable sealing performance: The perpendicular movement of the disc onto the seat ensures a tight shutoff.
3. Ease of maintenance: The seat and disc can often be repaired or replaced without removing the valve body from the pipeline.
4. Durability: When constructed from the right materials, globe valves can handle high pressure, high temperature, and corrosive fluids.

Limitations

         Despite their many advantages, globe valves also have limitations:

• Higher pressure drop: The tortuous flow path creates resistance and energy loss.
• Greater operating torque: More force is required to open or close the valve compared to gate or ball valves of similar size.
• Size limitations: Globe valves are generally less economical for large-diameter pipelines because of the pressure drop and operating torque.

Applications

           Globe valves are widely used across industries such as power generation, oil and gas, chemical processing, and water treatment. Common applications include cooling water systems, fuel oil systems, steam lines, and process control loops. They are especially favored where precise flow regulation is necessary, or where frequent operation of the valve is expected.

Conclusion

            The globe valve, or 截止阀, remains a cornerstone of modern fluid control systems. Its working principle—based on the linear movement of a disc against a seat and a deliberately angled flow path—offers both reliable shutoff and precise throttling capability. While it introduces a higher pressure drop than other valve types, its reliability, accuracy, and ease of maintenance outweigh the drawbacks in many applications. For industries where precision and safety are paramount, the globe valve continues to be an indispensable choice.