What is a throttling valve?

Imagine water flowing through a garden hose. If you want the water to spray gently instead of gushing out, you can partially cover the end of the hose with your thumb. This limits the water flow, reducing the amount that comes out.

Throttling vs. On/Off:

1. Throttling Use:
   • The valve is intentionally positioned somewhere between fully open and fully closed.
   • The goal is to achieve a specific flow rate, pressure, or system behavior by creating a controlled restriction in the flow path.
2. On/Off Use:
   • The valve is either fully open, allowing unrestricted flow, or fully closed, completely stopping the flow.
   • There’s no intermediate control of the flow rate—just a binary state.

Example in Practice:

If you imagine a faucet, it can be used either way:

• Fully open or closed = On/Off Use.
• Partially open to control the water flow = Throttling Use.

What Makes a Valve Good for Throttling?

While some valves are specifically designed for throttling (like Globes or Butterfly valves), many valves can be used for throttling if their design tolerates the wear caused by partially restricting flow. However, not all valves are ideal for this purpose.

• Good for Throttling: Valves with gradual, controlled adjustments, like globe valves, are well-suited because their design minimizes turbulence and wear.
• Poor for Throttling: Gate valves or ball valves (unless specially designed) are better as on/off valves. Throttling them can lead to damage over time due to issues like vibration or cavitation.

Why This Matters:

Classifying a valve by how it's used emphasizes the function it performs in a system rather than its specific design. Understanding this distinction helps operators select and operate valves effectively, depending on whether they need precise flow control (throttling) or simple flow start/stop functionality (on/off).