Brake valves are used on the discharge of hydraulic motors to:

Brake valves are crucial components in hydraulic systems that help in controlling the operation of hydraulic motors. Their primary functions include preventing overspeed and managing pressure during deceleration or stopping of loads.

When an overrunning load is applied, such as when a heavy load or high inertia equipment begins to turn the motor faster than its intended speed, the brake valve engages to prevent overspeed. This is essential for maintaining the safety and integrity of the system, as excessive speeds can lead to mechanical failure or hazardous situations.

Additionally, when a load needs to be decelerated or stopped, the brake valve helps prevent excessive pressure buildup that can occur in the hydraulic system due to the sudden change in speed. By regulating the flow of hydraulic fluid, the valve ensures that the pressure does not rise to a dangerous level, safeguarding the components of the hydraulic system.

Thus, the correct answer encompasses both the prevention of overspeed when an overrunning load is applied and the prevention of excessive pressure buildup during deceleration or stopping. This highlights the dual role of brake valves in enhancing both safety and operational reliability in hydraulic systems.