Fluid Power Final Flashcards
Most common type of non positive displacement pump?
Centrifugal
2 types of positive displacement pumps?
Fixed and variable displacement
Types of fixed displacement pumps
Gear pumps, vane pumps, piston pumps, diaphragm pumps
Types of variable displacement pumps?
Piston pump and vane pump
Without a change in volume in a pump….
No fluid will flow through
Definition of a pumps capacity?
The amount of fluid a pump can move in a given time
What is a pumps flow measured in?
GPM (gallons per minute)
What 3 things determine a pumps capacity?
- Size of pumping element
- Viscosity of fluid
- Rpm
What are 2 ways pressure can be controlled?
- At the pump (pressure compensator)
- Deviate off unneeded flow (relief valve)
How to know which side is the Inlet and outlet of the pump?
Inlet is the bigger size and the outlet is the smaller size
Definition of pump cavitation?
The formation and collapse of air bubbles
What are some things that would make a pump cavitate?
Blockage on the Inlet or the viscosity of fluid in the pump
What is the other type of pump cavitation?
Pseudo cavitation
If pseudo cavitation is taking place, how may the system be running?
Spongey
Reasons for pseudo cavitation?
Leak on the Inlet side of the pump, excess air in the system, tank level too low
What would be a good indicator of pseudo cavitation?
The fluid in the tank would be foamy
4 ways valves are actuated?
- Manually
- Mechanically
- Electrically
- Pilot pressure
4 center conditions for DCV’s?
- Blocked
- Tandem
- Float
- Open
3 uses for an accumulator?
- Absorb shock
- Maintain pressure
- Establish flow
What does cracking pressure mean?
When a valve opens prematurely
What does a sequence valve do?
Allows one thing to happen before the other. To have reverse flow you must have a bypass check valve.
What does a pressure reducing value do?
Normally passing, once downstream flow reaches the valve pressure, the valve become non passing and fluid stops flowing
What does a counter balance valve do?
Counter acts a weight on a cylinder
What is the job of a relief valve and how do you trouble shoot it?
To limit system pressure and to make sure it starts flowing at the set point
What percentage of hydraulic fluid is air?
10% air by volume
