What type of control valve closes during the up stroke?

In the context of control valves, recognizing the operational characteristics of different types is essential for effective system control.

A reverse acting control valve is designed to close as the control signal (usually a pneumatic or electrical signal) increases, particularly during the upstroke. This behavior is critical in applications where the valve is controlling the flow of fluids based on the pressure or flow requirements of the system. The reverse acting mechanism ensures that as more input is provided, the valve responds by closing, thereby reducing flow or pressure in the system. This design is particularly useful in processes where minimizing flow is necessary under specific conditions, ensuring system stability and safety.

In contrast, direct acting control valves operate in the exact opposite manner, where an increase in control signal results in increased flow or opening of the valve. Other options, such as a programmable logic controller, refer to a controller system rather than a physical valve type, and extra low voltage pertains to electrical standards rather than the operation of control valves.