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Millwright Third Year 2018 > Hydraulic Pumps And Actuators Exam Review > Flashcards

Hydraulic Pumps And Actuators Exam Review Flashcards

1
Q

List the three (3) main styles of pumps (based on pumping elements)?

A
  • Piston Pump
  • Vane Pump
  • Gear Pump
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2
Q

What is required at the pump inlet in order for oil to flow into the inlet port?

A

Pressure Differential.

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3
Q

Explain why hydraulic pumps are required to be positive displacement pumps?

A

To maintain pressure by positive sealing, inlet to discharge. (eliminating backpressure)

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4
Q

Explain the difference between a pressure compensation and load sensing in a pump. And Which one is more efficient?

A

Pressure Compensation Pump: Is to reduce flow, but maintain self operating pressure.

Load Compensating Pump: It adjust pump stroke to maintain only required flow and required pressure drop. plus (200 to 400 psi)

Load Compensating is more efficient.

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5
Q

Explain the difference in Operation between an in-line axial piston pump and a bent-axis piston pump?

A

An in-line piston pump has a swash plates which can be adjusted to an operating degree. The bent-axis has a bent shaft and can be adjusted by a block.

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6
Q

Explain the difference in operation between a radial piston pump and a rotary piston pump?

A

The difference is that the rotary piston pump the pistons are rotating

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7
Q

What is the purpose of the intra-vane in a pump? And in what type of vane pump would you find one in?

A
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8
Q

Explain the difference between a balanced cam pump and an unbalanced vane pump?

A
  • Balance Cam Pump: is more compact and has an eccentric cam.
  • Unbalanced Vane Pump: Is a variable pump.
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9
Q

Explain the differences between an internal gear pump and an external gear pump?

A
  • External Gear Pumps: They have two (2) meshing gears together.
  • Internal Gear Pumps: Internal has a crescent seal.
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10
Q

Gerotor gear pumps do not have seals. What is required for Gerotor pumps to be a positive displacement pump and where are they found?

A
  • Sliding Creates sealing

* They are found on charged pumps

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11
Q

Explain the operation of a cylinder cushion?

A

It’s purpose is to provide cushion when it hits the end of stroke.

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12
Q

Explain the factors that affect torque and speed in hydraulic motors?

A

======

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13
Q

Why should dynamic seals have some leakage?

A

For Lubrication

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14
Q

How can you determine the proper torque value when you are assembling a hydraulic component?

A

Consult the service manual.

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15
Q

What type of sealant should be used on tapered pipe threads in hydraulic systems?

A

Liquid PTFE (Teflon)

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16
Q

When static O-ring gaskets are used, what percentage must they project from the mating surface?

A

10%

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17
Q

What method is used to ensure that you have achieved your target cleanliness code for a hydraulic system?

A

Use a particle counter

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18
Q

Which filter must be rated at the relief valve pressure of the system?

A

Pressure line filter.

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19
Q

What is the recommended micron size filter for a reservoir breather?

A

3 Microns

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20
Q

What is the efficiency of a filter with a Beta Ratio of 10?

A

90%

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21
Q

what is the main purpose of an accumulator?

A

To store pressurized hydraulic fluids.

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22
Q

What extra safety precaution must be taken when working on a system with an accumulator?

A

Completely depressurize and block out accumulator.

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23
Q

Which type of gas could be used in a gas accumulator?

A

Nitrogen.

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24
Q

What is the main disadvantage of a spring type accumulator?

A

Cannot maintain a constant pressure as they discharge.

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25
Q

What component in a reservoir reduces turbulence, aids in cooling, and promotes settling of contaminants?

A

The Baffle

26
Q

The oxidation rate of petroleum based hydraulic oil doubles every 10°C above?

A

60°C

27
Q

What condition can occur should the inlet strainer on a pump be clogged?

A

Cavitation

28
Q

What size is an open circuit reservoir when compared to the capacity of the pump?

A

2 - 3 times larger

29
Q

What condition can occur should the pump shaft seal fail?

A

Aeration

30
Q

In addition to transmitting power, what are the other functions must hydraulic fluid must do?

A
  • Lubricate
  • Cool
  • Seal
  • Clean
31
Q

Viscosity Index (VI) of oil is defined as?

A

Stability of an oil viscosity over a temperature range.

32
Q

Built in contamination in a hydraulic system can happen when?

A

When the components are assembled and repaired.

33
Q

What is the main cause of oxidation in a hydraulic fluid?

A

*Heat

34
Q

Which filter location is the most efficient in a hydraulic system?

A

Permanent off-line

35
Q

A rotating mechanical seal that allows controlled leakage for flushing and cooling purposes would be classified as?

A

Positive/Dynamic

36
Q

What is the proper accumulator Pre-charge if used for shock absorption purposes?

A

75% of normal working pressure

37
Q

Cavitation can be the result of?

A

Running a pump at too high a speed.

38
Q

An example of dynamic pump would be

A

Impeller

39
Q

A cylinder which is extended by force and retracted by spring or gravity is known as

A

Single Acting

40
Q

The flow produced by a pressure compensated pump during cylinder extension is at

A

Load Pressure

41
Q

The flow produced by a pressure compensated pump at the end of stroke is at

A

No flow produced

42
Q

The purpose of a cylinder cushion is to?

A

Reduce mechanical shock

43
Q

The pump in a hydraulic system produces?

A

Fluid Flow

44
Q

An unbalanced vane pump can be identified by its?

A

Off-Centre cam ring

45
Q

Variable displacement vane pumps control fluid flow by?

A

Shifting the cam ring

46
Q

The vanes of a pump maintain contact with the cam ring by?

A

Centrifugal Force / Fluid Pressure

47
Q

A balanced vane pump would have?

A

Sets of inlet and outlet ports opposing each other

48
Q

The displacement of a bent-axis piston pump can be varied by?

A

Pivoting the cylinder block to change angle to shaft

49
Q

The torque of hydraulic motor is dependent upon?

A

Inlet pressure, surface area and radius of rotation

50
Q

If a cylinder had internal leakage it would affect?

A

Speed

51
Q

Hydraulic motors are driven by?

A

Fluid flow and pressure

52
Q

Which component prevents contamination from entering a cylinder?

A

Rod Wiper

53
Q

Which type of cylinder accelerates during extension?

A

Telescopic

54
Q

Balanced vane motors maintain vane contact by?

A

Fluid Pressure / Springs

55
Q

In an in-line axial piston motor, speed can be increased by

A

Decreasing swash plate angle

56
Q

The purpose of a stop tube is?

A

Reduce side load when extended

57
Q

In a rotary piston pump the fluid is ported in and out of cylinders through the?

A

Pintle

58
Q

The output flow of gear pumps can be adjusted by

A

Changing RPM of prime mover

59
Q

A radial piston motor can be classed as?

A

Low Speed / High Torque

60
Q

O-ring boss port connections have which type of threads?

A

Straight

Millwright Third Year 2018 (15 decks)

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