In industrial piping systems, there is a distinct difference between stopping flow and regulating it. While "on-off" control is straightforward, throttling—the process of regulating the volume or pressure of the fluid passing through the system—requires specific valve geometry to avoid damaging your equipment.
Choosing the wrong valve for throttling can lead to poor system performance, rapid erosion of valve components, and the damaging phenomenon known as cavitation. In this guide, we break down the most common valve types used for flow regulation and how to choose the right one for your specific application.
When engineers ask about the best valve for throttling, the answer is almost invariably the Globe Valve. Unlike other designs, the internal structure of a globe valve forces the fluid to change direction, passing through a linear motion plug and seat.
This design provides a proportional relationship between the valve opening size and the flow rate, allowing for highly precise adjustments. If your system requires frequent fine-tuning of pressure or flow volume, the High Performance Throttling Globe Valve is often the superior choice.
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A common search query we see is regarding ball valve throttling. Standard ball valves are designed primarily for shut-off services. When a standard ball valve is partially closed, the high-velocity flow impinges directly on the exposed edge of the ball and the soft seat, leading to rapid wear and potential leakage.
However, technology has evolved. While a standard Stainless Steel Two Piece Ball Valve should generally be used for on/off applications, specialized V-port ball valves or trunnion-mounted designs are engineered to handle throttling duties better than their floating ball counterparts.
If you are using ball valves, ensure they are specified for high-pressure control, such as our High Pressure Trunnion Mounted Ball Valve, which offers greater stability under varying pressure conditions.
For large-diameter pipes where a globe valve would be too heavy and expensive, Butterfly Valves are a viable throttling solution. They are particularly effective in water treatment and HVAC applications where linear flow characteristics are not strictly required.
A Lug Style Butterfly Valve allows for flow regulation, typically between 15% and 75% open. Opening them less than 15% can cause turbulent flow and damage the seal, while opening them past 75% offers little additional flow control compared to fully open.
For automated systems, pairing these with an actuator, such as a High Performance Electric Actuated Butterfly Valve, can provide consistent modulation without manual intervention.
When selecting a throttling valve, consider the following:
For a deeper technical dive into valve sizing and flow coefficients (Cv), resources like the International Society of Automation (ISA) provide extensive standards and guidelines for control valve engineering.
Q: Can I use a Gate Valve for throttling? A: generally, no. Gate valves, such as the Forged Carbon Steel Gate Valve, are designed to be fully open or fully closed. Using them for throttling causes "wire drawing" (erosion) of the seat and vibration (chatter) that ruins the valve.
Q: What causes cavitation in throttling valves? A: Cavitation occurs when the pressure drops below the fluid's vapor pressure, forming bubbles that collapse violently. This is common when throttling high-pressure lines. Using appropriate Globe Valves designed for severe service helps mitigate this.
Q: What is a "V-Port" ball valve? A: It is a ball valve where the ball has a "V" shaped opening rather than a round hole. This allows for a more linear flow characteristic, making it suitable for throttling applications where standard ball valves fail.