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Heavy Equipment Technician Period 3 Alberta > 190301d Hydraulic actuator fun > Flashcards

190301d Hydraulic actuator fun Flashcards

1
Q

Hydraulic cylinders create what type of motion?

A

Linear/ straight line

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2
Q

Single acting cylinders are hydraulically actuated in two directions?

A

Nope

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3
Q

On a ram type cylinder, what are the basic components?

A

Piston Tube, Cylinder barrel, guide rings

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4
Q

How is retraction done on a ram type cylinder?

A

By connecting inlet and outlet ports to the reservoir

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5
Q

On a piston type single acting cylinder, if oil is coming out of the air vent what could be the cause?

A

a piston seal is leaking

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6
Q

What are two types of single acting cylinders?

A

piston or ram type

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7
Q

What causes a piston type cylinder to retract?

A

gravity/weight of the load

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8
Q

How should you adjust the packing nut on a ram type cylinder?

A

Until packing is tight enough to leave a thin film of oil on piston tube when cylinder extends

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9
Q

Why do we use telescoping single acting cylinders?

A

To obtain additional stroke length from a relatively compact retracted package

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10
Q

The first stage on a telescoping single acting cylinder is?

A

largest, develops greatest force, slowest speed

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11
Q

2nd stage and all after, what happens to speed and force

A

Force decreases, speed increases

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12
Q

Double acting cylinders do what?

A

both hydraulically extend and hydraulically retract, oil acts on both sides

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13
Q

In a double acting cylinder, rod end cap is attached to the??

A

Cylinder barrel to prevent external leakage. Threaded together

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14
Q

Double acting cylinder, O-rings and back up rings are used to seal?

A

The cap to the barrel

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15
Q

What are the moving parts in a double acting cylinder?

A

Piston and Piston Rod

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16
Q

Hydraulic cylinders are used to create?

A

Linear (straight) motion to perform work

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17
Q

Pistons are machine grooved in the outer circumference so the piston seals and?

A

Wear rings can be fitted

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18
Q

Seals are used for stopping what?

A

Internal and extend leakage

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19
Q

When selecting a seal you should consider?

A 
Operating pressures and temps
Fluid compatibility
cylinder speed
clearance to be sealed
internal friction
finish of the sealing surface
acceptable seal life
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20
Q

What materials are seals made of?

A

leather, polyurethan, nitrile or viton

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21
Q

What do wipers do for a cylinder?

A

prevent some contamination while cylinder retracts, allowing some leakage to lube seals

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22
Q

Bearings are used to do what in a cylinder?

A

support piston and piston rod

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23
Q

Bearings in a cylinder can be made from?

A

iron, brass, phenolic or composite material

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24
Q

Conventional cylinder, double acting, single rod cylinders are called?

A

Differential cylinders because difference between extension and retraction speed and the forces they produce

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25
Q

If the piston seal starts to leak on a differential cylinder, what will it cause?

A

reduce cylinder speed and cylinder drift in the hold position

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26
Q

Hold position blocks oil flow from?

A

Both rod and base end of the cylinder

Hydrostatic lock

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27
Q

If there is a leak in a double acting cylinder, what can happen?

A

Oil may flow from the rod end to the base end of the cylinder, may cause drift out to extension direction

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28
Q

Single acting cylinders are hydraulically actuated in?

A

One direction, need gravity or load to make them retract

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29
Q

Cylinder drift will only happen in what direction?

A

Extension

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30
Q

If your piston seals on a cylinder leaks where can you see the problem?

A

Direction control return line

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31
Q

Pressure required to support a load doubles when the piston seals are leaky is known as?

A

Pressure intensification

32
Q

Double acting, double rod cylinder (non-differential cylinder)

A

Has equal piston area and equal volume or both sides

33
Q

Telescoping cylinders can be?

A

Single acting or double acting, offers long working stroke from a compact retracted package

34
Q

Double acting telescoping cylinders are used in what applications?

A

Mining haul trucks, boxes that go over center

35
Q

What are some features that cylinders have?

A

Piston relief valve
cylinder cushions
quick drop valves

36
Q

When does the piston relief valves allow oil flow to bypass the piston?

A

When the piston reaches the end of its stroke

37
Q

Describe a piston relief valve.

A

Double check valves

38
Q

Cylinder cushions are used to stop a piston?

A

Nope, they slow down the hydraulically operated implement

39
Q

What creates a cylinder cushion effect?

A

the effect is accomplished by restricting the return oil from the cylinder, back pressures the piston and resists movement

40
Q

What two types of cylinder cushions are there?

A

Cushion plunger

Cylinder return drillings

41
Q

Quick drop valves use who’s principle?

A

Bernulli’s

42
Q

What do quick drop valves provide?

A

Faster lowering cycle times on implements

43
Q

The quick drop valve supplements pump flow to the base end of the cylinder with the oil flow from the rod end, what is this principle called?

A

Regeneration

44
Q

Are quick drop valves normally closed?

A

Yes

45
Q

Can a slower lowering speed be achieved with a quick drop valve?

A

Yes, if the operator feathers the direction control valve

46
Q

When does cavitation occur in a cylinder?

A

When the cylinder drops faster than the oil flows

47
Q

What is a sign of a failing quick drop valve?

A

No power down

No quick drop (lowering slower than normal

48
Q

What type of energy do hydraulic motors convert?

A

Hydraulic energy to mechanical energy

49
Q

What do hydraulic motors convert oil flow and pressure into?

A

Speed and torque

50
Q

What dictates the speed of the motor driveshaft?

A

The inlet flow rate and capacity of the motor

51
Q

If a motor with a given displacement is given a greater flow rate supply what happens to the driveshaft?

A

It will rotate faster

52
Q

Motor inlet pressure (max sys pressure) and motor displacement determine what in a hydraulic motor?

A

The amount of torque generated

53
Q

Motors can convert all hydraulic energy to mechanical energy correct?

A

No, some is loss to leakage and friction

54
Q

Why is internal leakage necessary?

A

For lubrication and cooling of moving parts

55
Q

If internal clearances increase (due to normal wear), will oil flow through the drain line increase?

A

Yes

56
Q

What are three basic types of hydraulic motors?

A

Gear, Vane and piston motors

57
Q

What are two types of gear motors?

A

External and gerotor (geroller) motors

58
Q

The gear in an external gear pump that is not connected to the drive shaft is considered?

A

An idler

59
Q

If you reverse the oil flow through an external gear motor what happens to the output shaft?

A

It will reverse shaft rotation

60
Q

Do external gears have a lot of working surface area?

A

No

61
Q

Are external gear pumps balanced or unbalanced?

A

Unbalanced

62
Q

Do gear pumps create a lot of torque?

A

Nope

63
Q

Gerotor motors are also know as?

A

Orbit motor

64
Q

Are gerotor motors low rpm and right torque?

A

Yeah

65
Q

Which component is splined to the output shaft of a gerotor motor?

A

Gerotor star, spool valve

66
Q

Does the gerotor star need to be timed?

A

Yup, must be timed

67
Q

What is different in a geroller motor compared to a gerotor motor?

A

Gerollers have roller inserts for better wear characteristics, disc type valves instead of spool valves

68
Q

Vane motors have what under the vanes to provide flow when starting up?

A

Springs

69
Q

Most vane motors are balanced or unbalanced?

A

Balanced

70
Q

In a balanced vane motor the inlet and outlet ports are located where?

A

180° from each other

71
Q

Do balanced vane motors operate at higher pressures compared to unbalanced vane motors?

A

Yes

72
Q

Can vane motors be driven in reverse with oil flow?

A

yes

73
Q

Are vane motors more volumetrically efficient than external gear motors?

A

Yes

74
Q

Are balanced vane motors good torque generators?

A

yes

75
Q

Are piston motors variable displacement?

A

They can be fixed or variable

76
Q

What are the three types of piston motors?

A

Axial, Bent Axis or Radial

Heavy Equipment Technician Period 3 Alberta (15 decks)

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