What kind of valve should not be used for throttling purposes?

The gate valve is not suitable for throttling purposes due to its design and functionality. These valves are specifically intended to be fully opened or closed, providing minimal resistance to flow when in the fully open position. The mechanism involved in a gate valve consists of a wedge that moves up or down to either allow or prevent flow, leading to significant turbulence and potential damage to the valve if used to regulate flow.

When attempting to throttle flow with a gate valve, the valve does not effectively control the flow rate. This can cause excessive pressure loss and reduce the valve’s lifespan, as it is not designed to be operated in a partially open state. Thus, while it's great for isolation, it lacks the precision necessary for tasks requiring fine flow adjustments, making it unsuitable for throttling applications.

In contrast, other types of valves, such as globe valves, are constructed to allow for better flow regulation and can handle throttling applications more effectively, providing more precise control over flow rates. Ball valves and check valves also serve specific purposes that align better with their operational capacities.