What type of valve controls the direction of fluid flow in hydraulic systems?

The correct choice is the directional control valve, which is specifically designed to control the flow direction of hydraulic fluid within a system. This type of valve allows the operator to channel fluid to different actuators or components, enabling functions like lifting, lowering, or moving in different directions depending on the design of the hydraulic circuit. By manipulating the position of the directional control valve, you can effectively control the hydraulic movement of equipment such as forklifts.

Other types of valves serve different purposes: the pressure relief valve is responsible for protecting the system from excessive pressure by diverting fluid back to the tank when pressure exceeds a certain threshold. The flow control valve regulates the rate of fluid flow, affecting the speed of the actuators but not the direction. Meanwhile, the check valve allows fluid to flow in only one direction, preventing backflow, but does not direct the flow itself. Thus, the directional control valve is the fundamental component that facilitates the necessary directional changes in hydraulic systems.