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Hydraulics > Final 12/19 > Flashcards

Final 12/19 Flashcards

1
Q

Non-positive displacement pumps are

A

Centrifugal

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2
Q

Positive displacement pumps are all

A

Fixed displacement
Or
Variable displacement

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3
Q

Why does a Variable displacement pressure compensated piston pump have a case drain on it?

A

To monitor pump life.
Too much flow over the case drain will cause the pump to go out.

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4
Q

What is cavitation?
What causes cavitation?

A

The formation and collapse of air bubbles.
Caused by too much vacuum on the inlet side of the pump. There is not enough vapor pressure to hold the 10% entrained air dissolved in the oil.

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5
Q

True pump cavitation stops where?

A

At the pump

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6
Q

What 2 things can cause true pump cavitation?

A

Restriction on the inlet side of the pump.
Oil temp too cold causing the fluid to be too thick.

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7
Q

Psudo-cavitation or false cavitation is caused by?

A

Extra air being drawn into the inlet side of the pump. This causes aeration of the fluid throughout the entire system.

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8
Q

What are two things that can cause pseudo cavitation?

A

1) A crack on the inlet piping
2) Fluid level being too low allowing air to be drawn into the inlet of the pump.

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9
Q

Definition of hydraulic fluid.

A

A substance used for transmitting energy from pump to actuator in a working hydraulic system.

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10
Q

List the 4 uses of hydraulic fluid in a fluid power system.

A

1) transmits power
2) lubricates parts
3) cools moving parts
4) seals clearances

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11
Q

When is hydraulic fluid most flammable?

A

When it’s atomized (sprayed in the air at high pressure)

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12
Q

What are the two types of hydraulic fluid?

A

Water based and synthetic

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13
Q

Water based hydraulic fluid 3 types

A

1) water-oil emulsion 60% water 40% oil
2) invert emulsion 40% water 60% oil
3) water glycol

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14
Q

Synthetic hydraulic fluid is

A

A) phosphate ester
Its very expensive and highly corrosive

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15
Q

Hydraulic fluid additives (4)

A

1) AW- Anti wear
2) WR- wear resistant
3) EP- extreme pressure
4) R&O rust and oxidation inhibitor

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16
Q

AW stands for

A

Anti wear

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17
Q

WR stands for

A

Wear resistant

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18
Q

EP stands for

A

Extreme pressure

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19
Q

R&O stands for

A

Rust and oxidation inhibitor

20
Q

Hydronic motors do what?

A

Convert working energy into rotary mechanical energy.

21
Q

3 Hydraulic motors

A

1) Vane
2) gear
3) piston

22
Q

How many positions can a DCV have?

A

2 or 3

23
Q

How many ways can a DCV have?

A

2,3 or 4

24
Q

4 ways DCVs are operated

A

Manual
Mechanical
Electrical
Pilot pressure

25
Q

3 kinds of or returned or held

A

Detent held
Spring returned on 2 position
Spring centered on 3 position

26
Q

Center conditions of DCVs

A

Float
Blocked
Open
Tandem

27
Q

Valve size by ports (4)

A

1) D03 smallest
2) D05
3) D08
4) D010 larger

28
Q

Check valves

A

Allow flow in only one direction

29
Q

What can check valves be used in applications such as..

A

By pass check
Isolation/back flow check

30
Q

What are accumulators charged with?

A

Nitrogen

31
Q

Types of accumulators (3)

A

Weight loaded
Spring loaded
Hydro-pneumatic

32
Q

What 3 things are accumulators used for?

A

Develop flow
Maintain pressure
Absorb shock

33
Q

Reservoir types (3)

A

Conventional
Overhead
L-Shaped

34
Q

Types of fluid coolers (2)

A

Air cooled
Water cooled

35
Q

Name the 2 types of flow controls

A

Fixed
Adjustable

36
Q

Locations of hydraulic filters (4)

A

1) sump strainer
2) suction filter
3) pressure filter
4) return filter

37
Q

Hydraulic cylinder types (4)

A

Single acting
Double acting
Single rod
Double rod

38
Q

Parts of a hydraulic cylinder (6)

A

Cylinder body
Piston with rings
Rod
Rod gland seals
Rod gland bushing
Ports

39
Q

What’s the purpose of cushion valves

A

Slows the rod speed at the very end of the stroke.
Helps eliminate hydraulic shock

40
Q

Relief valve
What’s it do and how does it work

A

Limits system pressure
Normally non passing
Pilot pressure before the valve opens the poppet to allow flow.

41
Q

Valve that allows one operation to happen before another.

A

Sequence valve

42
Q

4 features of a sequence valve

A

1) normally non passing
2) pilot pressure before valve opens the poppet to allow flow.
3) external bleed line vents to tank
4) to have reversible motion with using valve as a bypass check valve must be used in parallel.

43
Q

Valve that reduces down stream pressure after the valve.

A

Pressure reducing valve

44
Q

3 features of a pressure reducing valve

A

Normally passing valve
Reduces pressure by stopping the flow after the valve. So pressure does not build passed setting.
Bleed drains excess fluid back to tank if pressure overshoots set point.

45
Q

Valve that counteracts a heavy weight on an actuator.

A

Counterbalance valve

46
Q

Baffle plate purposes (4)

A

Creates quiet zone
Allows time for fluid to cool
Dirt to settle out
Entrained air time to escape

Hydraulics (1 decks)

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