What type of valve requires five full turns of its handwheel to be fully open or closed?

The choice of a slow opening valve is correct because slow opening valves are designed to control flow gradually and require multiple turns of their handwheel to fully open or close. This design allows for a smooth start and stop of flow, which is particularly important in preventing sudden pressure changes that could damage piping systems or equipment.

Typically, slow opening valves are employed in systems where precise control of flow is necessary, such as in cooling water systems or in certain process applications. The five full turns of the handwheel indicate that the valve mechanism is geared for detailed adjustments, as opposed to rapid operation.

In contrast, quick opening valves are designed for faster actuation, often used in applications where immediate flow is needed. Multi-turn valves also refer to a category that embodies allowing for multiple turns, but the context of five full turns specifically points more accurately to a slow opening valve due to its design focus on gradual flow control. A stop valve typically operates as a simple on/off mechanism rather than emphasizing gradual transitions in flow.