Hydraulic Valves A Flashcards
Relieves maximum pressure in a system in case of an overload
maximum pressure valve
Relives all pressure under normal operation
unloading valve
relief valve to handle small flows, accurate control of pressure is not important, quick acting
direct acting or simple relief valve
the difference between full flow pressure and cracking pressure
pressure overide
what is the pressure override if cracking pressure and full flow pressure is the same
0
relief valve for pressures above 500 psi, energy effiecient by minimizing pressure override, 20 psi light spring
pilot operated relief valve
unloading valve used in accumulator circuits
unloading relief valve
unloading valve installed in pressure line from the accumulator can serve to unload the system when the pump is shut down
on/off valve
unloading valves provides a means of unloading hydraulic system from remote location
vented relief valve
unloading valve used in high and low volume pump system. both pumps work to clamp workpiece and low pump maintains flow to develop high pressure for clamping
pilot operated unloading valve
valve used when one needs to operate only one branch of a circuit below the setting of the maximum pressure relief valve
pressure reducing valve
the sequence valve needs to be set higher or lower than the clamping pressure
lower
the sequence valve needs to be set higher or lower then the second cylinder
higher
drain type on counterbalance valve
internal
drain type on sequence valve
external
counterbalance valve are set higher or lower than pressure needed to hold load
higher
valve installed on discharge of motor to prevent overspeeding when an overruning load is applied
brake valve
internal/external pilot on brake valve allows oil to pass to start the load
internal
internal/external pilot on brake valve stops the load from overruning
external
flow path on DCV are called
ways
valve position used for single acting cylinder, also to divert flow
3 way, 2 position
DCV used to operate flows above 20-25 GPM
pilot operated DCV, or piggy back DCV
pilot operated valve direct fluid to main valve at this PSI
75-100
spool center locks cylinder but also allows pump to supply other valves
tandem center
spool center shuts off pump flow but allows motors to coast freely without stopping it suddenly
float center or motor center
check valve poppet used to handle higher flows
poppet style
check valve poppet used to handler smaller flows
ball style
check valve able to handle 3 times the flow
right angle check valve
check valve commonly used to ensure accumulator is depressurized when pump is shut down
pilot to close
3 flow control methods
meter in
meter out
bleed off
metering method best used to push a load
meter in
metering method best used to provide positive control for runnaway loads
meter out
metering method most energy effiencient, does not provide accurate control or control for runaway loads
bleed off
pressure compensators are also called
hydrostat
2 types of pressure compensator
bypass
restrictor
pressure compensator used in meter in only
can replace main relief valve
bypass compensator
pressure compensator able to be used in meter in and meter out application
restrictor pressure
