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Hydraulics > Hydraulic System Circuit > Flashcards

Hydraulic System Circuit Flashcards

1
Q

What is hydrodynamics?

A

The use of fluids at high speeds ‘on impact’ to supply power.

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2
Q

What is hydrostatics?

A

The use of fluids at relatively low speeds, but at high pressures, to supply power.

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3
Q

True or False: A cylinder with a larger bore diameter will cycle faster at a given fluid flow rate than a smaller bore diameter cylinder.

A

False

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4
Q

What happens to fluid velocity as it flows from a large pipe to a smaller pipe?

A

Fluid velocity will increase.

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5
Q

True or False: When oil flows through an orifice, a restriction to flow is created, producing pressure on the downstream side.

A

True

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6
Q

What is the speed at which a fluid moves through a confined circuit called?

A

Velocity

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7
Q

What is flow rate?

A

The volume of fluid which flows through a pipe during a specified unit of time.

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8
Q

Fill in the blank: The _______ creates flow, while the load and actuator size determines operating pressure.

A

pump

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9
Q

What are the main types of hydraulic system circuits used in mobile plant?

A

Open centred and Closed centred.

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10
Q

What does a series circuit in hydraulics allow?

A

One path of fluid to flow.

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11
Q

What is the characteristic of a parallel hydraulic circuit?

A

Components are connected in parallel, allowing fluid to flow to multiple valves concurrently.

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12
Q

What determines the flow rate of oil in a hydraulic circuit?

A

The pump output.

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13
Q

What is the formula to calculate flow rate in litres per minute?

A

L/min = cc/rev x rpm / 1000

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14
Q

What happens to circuit pressure in a series circuit?

A

The total resistance is the sum of each individual component’s resistance to flow.

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15
Q

What is one advantage of an open centre constant flow circuit?

A

It has a relatively low-cost option for simple function control.

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16
Q

What is a disadvantage of an open centre constant flow circuit?

A

Efficiency is poor when only partial flow is required at high pressure.

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17
Q

What is the function of a closed centre load sensing circuit?

A

It connects the directional valves in parallel.

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18
Q

List the components of a basic hydraulic system.

A
  • Pump
  • Valve
  • Accumulator
  • Filter
  • Motor
  • Reservoir/Tank
  • Cylinder/Actuator
  • Conductors & Connectors
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19
Q

What are the safe work practices specific to hydraulic system circuits?

A

List and understand safe work practices.

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20
Q

What is the main purpose of a relief valve in a hydraulic system?

A

To protect the hydraulic system by diverting flow when pressure exceeds a set limit.

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21
Q

What is the role of pressure in hydraulic systems?

A

Pressure makes things move.

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22
Q

True or False: The pump can be destroked during operation in a closed centre system.

A

True

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23
Q

What is the impact of restrictions on oil flow in hydraulic circuits?

A

Restrictions encountered by oil flow will affect the amount of pressure in a circuit.

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24
Q

What is the primary characteristic of a closed centred hydraulic system?

A

The pump can rest when flow is not required to move an actuator.

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25
Q

Fill in the blank: The _______ is a common circuit type where a constant flow of oil is generated by a fixed-displacement pump.

A

Open Centre Constant Flow Circuit

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26
Q

What does the term ‘priority’ refer to in a series hydraulic circuit?

A

The valve that receives the flow first has priority.

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27
Q

What is a disadvantage of the open centre variable flow circuit?

A

Poor resilience to contamination in the system.

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28
Q

What does Pascal’s Law describe?

A

Pressure applied to a confined fluid is transmitted undiminished in all directions.

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29
Q

What is Bernoulli’s Principle related to?

A

The relationship between pressure and velocity in fluid dynamics.

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30
Q

What does the term ‘cavitation’ refer to in hydraulic systems?

A

The formation of vapor cavities in a liquid.

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31
Q

What can excessive noise in a hydraulic system indicate?

A

Possible issues such as cavitation or a worn pump.

32
Q

What is the significance of the actuator in a hydraulic circuit?

A

The actuator converts hydraulic energy into mechanical energy.

33
Q

What happens when a large rock is encountered while digging?

A

The hydraulics react by slowing down or stopping the arm movement

The operator must move the lever further to increase power to overcome the obstacle.

34
Q

What is a Closed Centre Load Sensing Circuit?

A

A circuit that connects directional valves in parallel

It efficiently supplies hydraulic movement to various machines.

35
Q

List applications of Closed Centre Load Sensing Circuit.

A
  • Forklift
  • Truck
  • Loader
  • Crane
  • Telehandler
  • Backhoe
  • Loading Shovel
  • Dump Truck
  • Excavator
  • Dozer
  • Skid Steer Loader
36
Q

What is an advantage of the Closed Centre Load Sensing Circuit?

A

Power is more efficiently used due to variable load sensing pump

This supplies flow and pressure to meet system demand.

37
Q

What is a disadvantage of the Closed Centre Load Sensing Circuit?

A

Complex and expensive components

It also has poor resilience to contamination.

38
Q

What occurs in a Closed Centre Constant Pressure Circuit when the valve is in a neutral position?

A

The directional valve blocks the flow of oil from the pump port to the tank port.

39
Q

List applications of Closed Centre Constant Pressure Circuit.

A
  • Loader
  • Crane
  • Backhoe
  • Dump Truck
  • Excavator
  • Dozer
  • Skid Steer Loader
40
Q

What is an advantage of the Closed Centre Constant Pressure Circuit?

A

Amplifies operator movements, reducing fatigue

It also removes the need for cables and linkages.

41
Q

What is a disadvantage of the Closed Centre Constant Pressure Circuit?

A

Poor resilience to contamination, with pilot valves being the most sensitive component.

42
Q

What is the primary difference between open loop and closed loop hydrostatic systems?

A

The way the oil is managed after it leaves the motor.

43
Q

List applications of Closed Loop Hydrostatic Circuit.

A
  • Forklift
  • Loader
  • Telehandler
  • Loading Shovel
  • Drum and Road Roller
  • Dump Truck
  • Excavator
  • Dozer
  • Skid Steer Loader
44
Q

What is an advantage of the Closed Loop Hydrostatic Circuit?

A

Variable transmission drive and direction change without operating clutches or brakes.

45
Q

What is a disadvantage of the Closed Loop Hydrostatic Circuit?

A

Poor overall efficiency in comparison to alternative mechanical drives.

46
Q

What safety practices should be followed when working with hydraulic systems?

A
  • Support raised equipment
  • Ensure discharge of stored energy
  • Lock out must be engaged
  • Isolate all energy sources
47
Q

What are some chemical hazards associated with hydraulic systems?

A
  • Hydraulic oil
  • Fuel
  • Fire suppressant
  • Engine oil
48
Q

What are the steps for troubleshooting and diagnosing faults in hydraulic systems?

A
  • Know the systems
  • Refer to appropriate resources
  • Ask the operator
  • Inspect the machine
  • Operate the machine to test
  • List the problem and possible causes
  • Reach a conclusion and plan action
  • Test and confirm results
49
Q

Fill in the blank: The __________ is used to monitor the level of contaminates in a kidney loop machine.

A

[particle counter]

50
Q

What should be checked when inspecting the oil reservoir?

A
  • Oil aeration
  • Change in oil level
  • Milky oil
51
Q

What are common faults in hydraulic circuit components?

A
  • Leaks on the low pressure side
  • Leaks on the high pressure side
  • Restrictions from pinched lines
52
Q

What is the purpose of a flow tester in hydraulic systems?

A

To determine whether the pump is producing its specified output.

53
Q

What does the term ‘PM’ stand for in hydraulic system maintenance?

A

[Preventative maintenance]

54
Q

What indicators suggest that a hydraulic system should be drained and flushed?

A
  • Sludging oil
  • Solid deposits
  • Varnishing on components
55
Q

What is the purpose of an oil cooler in a hydraulic circuit?

A

To check the oil cooler fins for plugging and test system valve operation. Wear can cause internal leakage.

56
Q

What components should be checked in a hydraulic circuit?

A
  • Valves
  • Cylinders
  • Pumps
  • Motors
57
Q

What should be monitored to prevent motors from overheating?

A

Ensure that the oil supply is adequate and that the oil cooler is functioning properly.

58
Q

What does a flow tester determine in a hydraulic circuit?

A

Whether the pump is producing its specified output.

59
Q

What are the components of a typical flow tester?

A
  • Pressure gauge(s)
  • Flow meter
  • Variable flow control valve
  • Thermometer
60
Q

Why is oil temperature important in hydraulic testing?

A

System pressure and flow specifications are calculated with the system at operating temperature.

61
Q

What is the function of cycle times in hydraulic systems?

A

They measure independent implement speeds calculated from specific flow and pressure rates.

62
Q

What is the recommended procedure for recording test results?

A

Observe the OEM test cycle and record results of each test step.

63
Q

What is the maximum pressure requirement for a pump according to OEM specifications?

A

At least 75% of the pump flow measured at zero pressure.

64
Q

What indicates a leaking hydraulic circuit?

A

When pressure drops off before full load.

65
Q

How can you determine if a leak is in the control valve or cylinder?

A

Disconnect the cylinder return hose and check for oil leakage.

66
Q

True or False: A relief valve should open before system maximum pressure is achieved.

A

False

67
Q

What should be done first in troubleshooting a noisy pump with slow implement cycle time?

A

Gather the correct schematic using machine serial number, model number, and/or arrangement number.

68
Q

What is a flow chart used for in troubleshooting?

A

To visually represent the process of narrowing down faults.

69
Q

What are the three ways hydraulic components can be connected?

A
  • Series
  • Parallel
  • Combination of both
70
Q

What is the significance of pump oil flow in a hydraulic system?

A

It flows the path of least resistance.

71
Q

Fill in the blank: Hydrostatic systems can be either __________ or closed loop systems.

A

open loop

72
Q

What is essential for effective troubleshooting in hydraulic systems?

A

A logical, systematic approach.

73
Q

What should be adhered to when working on hydraulic systems?

A

Safety instructions and requirements specific to the equipment.

74
Q

What tools can be helpful in the troubleshooting process?

A
  • Flowcharts
  • Fault charts
75
Q

What are the basic steps to take when servicing and maintaining a hydraulic system?

A
  • Understand the function of each circuit
  • Test and record your diagnosis
  • Follow safety protocols
76
Q

What is the goal of the upcoming session after this training?

A

Carrying out an introduction level of testing and adjusting system pressures to the OEM specifications.

Hydraulics (3 decks)

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