Always use a relief valve with fixed-displacement hydraulic
pumps. Pressure-compensated pump circuits also may use a relief
valve for certain applications. Think of a relief valve in a
hydraulic system as a fuse or circuit breaker in an electric
circuit. An electric circuit never blows a fuse unless it
overloads. When an electric circuit overloads, it is inoperable
until reset. Usually the person responsible for resetting the
fuse looks for the reason it blew and fixes the problem before
restarting the machine. Many hydraulic circuits allow the relief
valve to dump some or all pump flow to tank all or part of the
time. The extra power to produce that unused flow is expensive.
Also, heat generation from excess flow requires larger heat
exchangers that are expensive to buy and operate. Protecting the
pump and the system from excess pressure is the only valid
function for a relief valve. At no time should the relief valve
be used to pass excess pressure fluid to tank. When excess pump
flow goes to tank, it gener