Punps 2 Flashcards
What is cavitation?
Formation and collapse of air bubbles.
Describe cavitation.
When there is not enough vapor pressure to hold air and oil together.
What is cavitation caused by?
A great restriction on the inlet side of pump. Real Cavitation stops at the pump.
What is sudo-cavitation?
Extra air in oil.
What is sudo-cavitation caused by?
When you introduce extra air on inlet side of pump. Ex. Low fluid in tank. Crack on pipe on inlet side of pump.
What happens to machines during sudo-cavitation?
Can cause sponginess. Fluid will be milky.
Definition of a pump?
Draws fluid into largest volume area and moves to smallest volume area. Must be turned by a prime mover.
Two types of pumps?
Fixed displacement - puts out a set volume of fluid.
Variable displacement- does not have a set volume pump can change its volume with the squash plate.
What do you have to have with a fixed displacement pump to limit system pressure?
You have to have a relief valve.
Will fluid move without a difference of volume?
No.
Have to have a bigger supply (inlet) then demand (outlet)
Different styles of pumps?
Vane
Gear
Piston
Two types of vane pumps?
Balanced and unbalanced
Advantage of balanced vane pump?
Last longer
Easy rebuild
Quick change cartridge
Disadvantage of unbalanced vane pump?
Puts too much side load on the shaft.
What do you have to have on pump case to keep case from cracking or destroying pump?
Case drain.
Major difference between pumps and motors?
All motors can be pumps but not all pumps can be motors.
What do motors have that allow them to be pumps but pumps don’t have to be motors?
High pressure seal on the shaft.
What is a motor.
Pressurized fluids forced into smallest area and expands into largest volume area creating rotary motion.
What are advantages of hydraulic motors over Electric motors?
Instant reversing of motor shaft.
Stalling for indefinite periods without damage.
Dynamic breaking easily accomplished throughout operating speeds.
Torque control throughout operating speeds.
