How many complete turns are needed for a slow opening valve to go from fully closed to fully open?

A slow opening valve typically requires multiple full turns to transition from a closed to an open position. This design allows for precise control over the flow of fluid through the valve.

In the case of a valve needing five complete 360° turns to open fully, it indicates that the valve's mechanism is engineered for gradual adjustment, ensuring that changes in flow can be closely monitored and controlled. This can be crucial in high-pressure systems where sudden changes in pressure can lead to unsafe conditions.

The other options suggest fewer turns, which may not provide the necessary control or could indicate a valve type not suited for high-pressure applications. It's essential in these systems to maintain steady and controlled operation, which is best achieved through a valve requiring multiple turns to reach its fully open state.