Which valve type allows flow, stops flow, or returns oil to the tank in hydraulic systems?

In hydraulic systems, a valve that allows flow, stops flow, or returns oil to the tank is essential for controlling the operation of hydraulic machinery. A 3-way valve is designed to have three ports, allowing it to direct fluid to different paths based on its position. This means it can either allow fluid to flow to an actuator, stop the fluid for maintenance or safe operation, or divert the fluid back to the tank when the actuator is not in use.

The versatility of the 3-way valve makes it particularly important in hydraulic applications where different functions are required depending on the system's operation. For example, it can be used to control a cylinder's extend and retract functions by directing the hydraulic fluid appropriately.

In contrast, other valve types have different configurations and functionalities. A 2-way valve, for instance, is typically used for on/off control but does not provide the ability to return fluid to the tank. A 4-way valve has additional capabilities to control multiple cylinders and can direct fluid in different ways, usually accommodating more complex operations than just fluid return. Thus, the specific functionality of a 3-way valve makes it the correct choice for allowing flow, stopping flow, and returning oil in hydraulic systems.