Hydraulics Flashcards
How is a gerotor pump recognized?
Internal gear has one less tooth than external female gear
What does an unloading valve do?
Returns fluid back to tank after system pressure is reached
In a fluid system what is used to maintain a constant pressure?
Regulator
What is the maximum load in pounds that can be moved with a setting of 1500 PSI and a cylinder bore of 3”?
10600 lbs ( pi R² )
If a non positive centrifugal pump delivers lower than required flow, what is the most likely cause?
The inlet is restricted
A pressure gauge reads 0 in a hydraulic system. What is the reason?
Tandem center DCV
How are filters sized?
Microns
What is a type of hydraulic valve that is normally open?
Pressure reducing valve
What is the principal function of a positive displacement pump?
To create a partial vacuum on the inlet.
What type of valve controls a system GPM (gallons per minute)?
Flow control valve
Fluid power actuators convert fluid into what?
Motion
With a pressure of 950 PSI and a load of 7.5 tons, what must the bore of the cylinder be if we add a 10% safety factor?
5” (FPA Triangle)
Determine the maximum pressure required using a 2” diameter cylinder moving a load of 5000 lbs?
1592 psi
In fluid power, how is pressure created?
A resistance to flow
Solid filled equilateral triangles on a schematic indicate what?
Flow
An external gear pump resembles what shape?
Figure 8 shape
The eternal seal of an internal gear pump is driven using what?
Driven using timing gears
Pumping chambers in a gerotor pump are created by?
Odd number of forms between both elements
Some pistons have grooves cut in the diameter with no lead. The function of these grooves are what?
Increases oiling system for better efficiency
If a swash plate in an axle piston pump is not adjustable, the pump is what?
Fixed displacement
If a new pump will not deliver flow, what is the 1st thing to check?
Pump not primed
The term meter out means that the flow control valve is located where?
Immediately after the actuator
If a pilot orifice is plugged what will happen?
Valve will not open
What is the function of a sequence valve?
It allows one operation to occur before another
If a pump has worn impellor tips, what is the cause?
Debree in oil
A closed hydraulic tank starts to cave in. What will cause the condition?
Completely plugged vent
What causes vibration to occur on the inlet line of a pump?
Cavitation
How many cubic inches are in one gallon of oil?
231
How do you choose hydraulic tubing?
Material, OD, wall thickness
What type of valve allows one operation to occur before another?
Sequence Valve
What is the principal function of a positive displacement pump?
To create a partial vacuum on the inlet
What type of hydraulic valve is used to control the GPM (Gallons per minute) of a pump?
a flow control valve
What type of hydraulic pump is used to handle high viscosity fluids?
A radial piston pump
What type of hydraulic pump has a swash plate?
An axial piston pump
For fluid to properly function over long periods of time, it must be what?
Always be kept clean
The function of a baffle plate in a hydraulic tank is what?
To prevent the returning fluid from directly entering the pump inlet
Fluid power actuators convert fluid force into what?
Motion
Calculate the retract speed of a cylinder with a 2.5” bore and a rod diameter of 1” with a supply of 15 GPM
841 in/min
Pascals law States that when pressure is applied to fluid at rest in a confined space, force is transmitted how?
Equally in all directions at right angles to the containing service
In a fluid power directional control valve symbol, the squares are called what?
Envelopes
The gear teeth on an external gear pump are what type?
Spur
The gears of an internal gear pump rotate in what direction?
In the same direction
Lobe pump rotors must be driven by?
Driven using timing gears
The difference between an unbalanced and a balanced vane pump is what?
The shape of the cam ring surface
The most efficient way to maintain contact of vanes to the cam ring surface is by what?
Centrifugal force
The amount of pressure available to create a volume of delivery from a positive displacement pump is what?
14.7 PSIA
What function does a MPRV serve?
Safeguard for the pump, will not allow pressure to exceed the setting.
Hydraulic fittings are sized with what?
Micron rating
What determines the length of a flare on a hydraulic fitting?
Nut ID
What is the last valve to open when starting a pump?
Discharge valve
A cylinder hammers back to the bottom on retract. How is this condition fixed?
Adjust cushion
A hydraulic pump is severely worn out. What is the most likely cause?
There is Aeration present
What causes Aeration?
Leaking inlet
Erratic and excessive noise in a lobe pump is caused by what?
Cavitation
What type of directional control valve center holds a load and dumps fluid back to the tank?
Tandem center
A cylinder creeps slowly what is the cause?
Spool of DCV is leaking
How many cubic inches are in an Imperial gallon?
277
