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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
Fill in the blank: The _______ is a common circuit type where a constant flow of oil is generated by a fixed-displacement pump.
Open Centre Constant Flow Circuit
26
What does the term 'priority' refer to in a series hydraulic circuit?
The valve that receives the flow first has priority.
27
What is a disadvantage of the open centre variable flow circuit?
Poor resilience to contamination in the system.
28
What does Pascal's Law describe?
Pressure applied to a confined fluid is transmitted undiminished in all directions.
29
What is Bernoulli’s Principle related to?
The relationship between pressure and velocity in fluid dynamics.
30
What does the term 'cavitation' refer to in hydraulic systems?
The formation of vapor cavities in a liquid.
31
What can excessive noise in a hydraulic system indicate?
Possible issues such as cavitation or a worn pump.
32
What is the significance of the actuator in a hydraulic circuit?
The actuator converts hydraulic energy into mechanical energy.
33
What happens when a large rock is encountered while digging?
The hydraulics react by slowing down or stopping the arm movement ## Footnote The operator must move the lever further to increase power to overcome the obstacle.
34
What is a Closed Centre Load Sensing Circuit?
A circuit that connects directional valves in parallel ## Footnote It efficiently supplies hydraulic movement to various machines.
35
List applications of Closed Centre Load Sensing Circuit.
* Forklift * Truck * Loader * Crane * Telehandler * Backhoe * Loading Shovel * Dump Truck * Excavator * Dozer * Skid Steer Loader
36
What is an advantage of the Closed Centre Load Sensing Circuit?
Power is more efficiently used due to variable load sensing pump ## Footnote This supplies flow and pressure to meet system demand.
37
What is a disadvantage of the Closed Centre Load Sensing Circuit?
Complex and expensive components ## Footnote It also has poor resilience to contamination.
38
What occurs in a Closed Centre Constant Pressure Circuit when the valve is in a neutral position?
The directional valve blocks the flow of oil from the pump port to the tank port.
39
List applications of Closed Centre Constant Pressure Circuit.
* Loader * Crane * Backhoe * Dump Truck * Excavator * Dozer * Skid Steer Loader
40
What is an advantage of the Closed Centre Constant Pressure Circuit?
Amplifies operator movements, reducing fatigue ## Footnote It also removes the need for cables and linkages.
41
What is a disadvantage of the Closed Centre Constant Pressure Circuit?
Poor resilience to contamination, with pilot valves being the most sensitive component.
42
What is the primary difference between open loop and closed loop hydrostatic systems?
The way the oil is managed after it leaves the motor.
43
List applications of Closed Loop Hydrostatic Circuit.
* Forklift * Loader * Telehandler * Loading Shovel * Drum and Road Roller * Dump Truck * Excavator * Dozer * Skid Steer Loader
44
What is an advantage of the Closed Loop Hydrostatic Circuit?
Variable transmission drive and direction change without operating clutches or brakes.
45
What is a disadvantage of the Closed Loop Hydrostatic Circuit?
Poor overall efficiency in comparison to alternative mechanical drives.
46
What safety practices should be followed when working with hydraulic systems?
* Support raised equipment * Ensure discharge of stored energy * Lock out must be engaged * Isolate all energy sources
47
What are some chemical hazards associated with hydraulic systems?
* Hydraulic oil * Fuel * Fire suppressant * Engine oil
48
What are the steps for troubleshooting and diagnosing faults in hydraulic systems?
* 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
Fill in the blank: The __________ is used to monitor the level of contaminates in a kidney loop machine.
[particle counter]
50
What should be checked when inspecting the oil reservoir?
* Oil aeration * Change in oil level * Milky oil
51
What are common faults in hydraulic circuit components?
* Leaks on the low pressure side * Leaks on the high pressure side * Restrictions from pinched lines
52
What is the purpose of a flow tester in hydraulic systems?
To determine whether the pump is producing its specified output.
53
What does the term 'PM' stand for in hydraulic system maintenance?
[Preventative maintenance]
54
What indicators suggest that a hydraulic system should be drained and flushed?
* Sludging oil * Solid deposits * Varnishing on components
55
What is the purpose of an oil cooler in a hydraulic circuit?
To check the oil cooler fins for plugging and test system valve operation. Wear can cause internal leakage.
56
What components should be checked in a hydraulic circuit?
* Valves * Cylinders * Pumps * Motors
57
What should be monitored to prevent motors from overheating?
Ensure that the oil supply is adequate and that the oil cooler is functioning properly.
58
What does a flow tester determine in a hydraulic circuit?
Whether the pump is producing its specified output.
59
What are the components of a typical flow tester?
* Pressure gauge(s) * Flow meter * Variable flow control valve * Thermometer
60
Why is oil temperature important in hydraulic testing?
System pressure and flow specifications are calculated with the system at operating temperature.
61
What is the function of cycle times in hydraulic systems?
They measure independent implement speeds calculated from specific flow and pressure rates.
62
What is the recommended procedure for recording test results?
Observe the OEM test cycle and record results of each test step.
63
What is the maximum pressure requirement for a pump according to OEM specifications?
At least 75% of the pump flow measured at zero pressure.
64
What indicates a leaking hydraulic circuit?
When pressure drops off before full load.
65
How can you determine if a leak is in the control valve or cylinder?
Disconnect the cylinder return hose and check for oil leakage.
66
True or False: A relief valve should open before system maximum pressure is achieved.
False
67
What should be done first in troubleshooting a noisy pump with slow implement cycle time?
Gather the correct schematic using machine serial number, model number, and/or arrangement number.
68
What is a flow chart used for in troubleshooting?
To visually represent the process of narrowing down faults.
69
What are the three ways hydraulic components can be connected?
* Series * Parallel * Combination of both
70
What is the significance of pump oil flow in a hydraulic system?
It flows the path of least resistance.
71
Fill in the blank: Hydrostatic systems can be either __________ or closed loop systems.
open loop
72
What is essential for effective troubleshooting in hydraulic systems?
A logical, systematic approach.
73
What should be adhered to when working on hydraulic systems?
Safety instructions and requirements specific to the equipment.
74
What tools can be helpful in the troubleshooting process?
* Flowcharts * Fault charts
75
What are the basic steps to take when servicing and maintaining a hydraulic system?
* Understand the function of each circuit * Test and record your diagnosis * Follow safety protocols
76
What is the goal of the upcoming session after this training?
Carrying out an introduction level of testing and adjusting system pressures to the OEM specifications.

Hydraulics (3 decks)

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