cogging
movement occurring in short, jerky increments
atmospheric pressure
29.92” Hg at sealevel
atmospheric pressure is used to:
- bring fluid into the pump
- accelerate fluid inside rotating mechanism
cavitation
if there’s not enough pressure to accelerate a fluid, air bubbles form in pump and implosions occur (ruins the pump)
implosions
occur because of high pressure as well as low pressure = changes of pressure
causes and remedies of real cavitation
- dirty suction strainer (filter)
- undersized or too long of hose on inlet side
- high altitude applications = less atmospheric pressure = move pump inside reservoir (“Flooded Suction”)
- increase rpm of electric motor to increase gpm will cause cavitation
- fluid viscosity is too high = pump starvation = oil is too thick
pseudo cavitation
- same effect as real cavitation
- no vacuum, outside air is sucked into the pump
causes of pseudo cavitation
- leaking pump shaft seal
- suction hose is not inside of fluid (fill up reservoir) = just sucking up air
motor
driven by fluid while a pump delivers flow
braking method
want to stop motor but this will create shock = insert braking valve that will sense this pressure and send fluid to tank
prevent cavitation
- one way to prevent cavitation is the motor centered spool DCV = if flow suddenly stops, motor can suck fluid from tank
- another way = make up check valves
cross over relief valve circuit
prevents shock and cavitation
over center pump
has a swashplate that can change the direction of the flow
two devices that convert linear motion to rotary motion
skotch yokes and the rack and pinion actuator (what we use in lab)
oscillating actuators
vane rotary actuators (single and double vane)
