PNA2 Flashcards
Why is an orb fitting preferable to as a tapper thread fitting
It causes less stress and distortion
Should you normally instal a cylinder with the ports at the top or the bottom
Why
Top
Allows for bleeding out after installation
Why is it important to align a cylinder to the load to which it is attached
To avoid wear on walls and on seals
What is the most costly result of leaks in a cylinder
Dirt and air
What is the operating principle of any hydraulic motor
Fluid pushes to turn the drive shaft
What does a decrease in mechanical in mechanical efficiency indicate
Increase in internal friction
What does a decrease in volumetric efficinecy indicate
Internal leakage
What type of gear motor requires timing
Orbiting gear
What is found in a vane motor that is not in a vane pump
Springs under the vanes
How can you change the displacement of a cam type radial piston motor
Change cam ring to a different size
By shutting off the cushion valve at the rod end of a cylinder with a load pulling what danger could occurs
Pressure intensification
What happends if you dont time a radial piston motor correctly
It runs in revers
Do pumps create pressure or flow?
Flow
Why are positive displacement pumps used for hydraulics
More acurate flow control
Does the volume of the pumping chamber expand or contract at the inlet
Expand at inlet
Three methods of changing the output of a pump
Built in flow controls
drive speed change
Variable displacement
Wish swash plate control, regulates the flow to suit any given load
Limits the maximum pressure in the system
Load sensing compensator
Pressure limiting compensator
When you install a load sensing pump what must the load sensor be set at to bring the bias piston back to full stroke
200-400 psi
Does the space between the vanes increase or decrease at the inlet
Increase
How is output flow increased on an unbalanced vane pump
By moving the cam further off Center
What is the rotation of a factory built vane pump
Right hand
On a gear pump do gears go into or come out of mesh at inlet
Come out of mesh
Fro what end of the pump is the rotation defined
Drive end
How do you change the direction of rotation in a balanced vane pump
Flip over cam ring, rotor and flex plate assembly
What pump is more compact balance or Unbalanced vane
Balance vane
Pumping chambers increase or decrease in volume at inlet and then increase or decrease as they push out fluid at discharge
Increase volume at inlet, decrease at discharge
How is fluid ported in and out of a radial piston pump
Through check valves in the Pistons
What’s more efficient gear pump or piston pump
Piston pump
Does an internal gear pump have the same number of teeth as the outside or should it have fewer
Fewer
Why is a very close fit necessary between the teeth the casing on a gear pump.
To prevent bypassing back to inlet
Which is the best pump to use if you have to locate it above the surface of the fluid: an in-line axial pump or a bent axis
Bent axis
What is the purpose of a bias piston in a in line axis piston pump
To move the swash play to the maximum angle
What provides more force to keep the vane in a vane pump against the cam ring
intra-vane
Cartage style -= high efficiency, high pressure
Positive seals and non positive seals differ how
Positive seals are designed for zero leakage
Non positive seals allow controlled leakage
How do static and dynamic seals differ
Static is for stationary parts
Dynamic Is for moving parts
What 2 seal types are used to deal against the case pressure in a hydraulic pump or motor
High pressure lip seals or mechanical seals
What seals are used for pressures over 150 psi
Mechanical seals
What are 3 accumulator applications
Compensate for lag
Emergency power
Makeup fluid for leakage
Four types of piston motors
Inline axial piston
Bent piston
Radial piston
Cam type radial piston
Maximum angle in an inline axial motor has what speed and what torque
Low speed
High toque
