These unloading valves are used to unload pumps, to tank when pressure in a separate part of the circuit reaches a pre-set level. The valves will close, causing the circuit to reload, when the pressure drops to approximately 85% of the unload pressure. The most common application is to maintain pressure in an accumulator to be used in emergency to operate essential hydraulic functions (eg. a brake circuit). The PUL valve has a drain port to ensure correct valve function while allowing the bypassed oil to be used for auxiliary circuits.