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Study Questions > Fluid Power > Flashcards

Fluid Power Flashcards

0
Q

Name the components of a hydraulic reservoir.

A 
Reservoir tank
Clean out cover
Suction, return and drain lines
Oil level gauge
Filler/breather cap
Baffles
Filters, screens and strainers
Vent
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1
Q

Draw and label a typical hydraulic system schematic.

A

dk

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2
Q

What are the five steps for flushing a new hydraulic system?

A

1) Flush with light rust and oxidation inhibited oil
2) Operate system at maximum flow rate to generate turbulent flow
3) Check filters
4) Refill with operating charge
5) Reach operating temperature
6) Exercise activators
7) Drain and flush non-circulating zones

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3
Q

What are some advantages of oil mist lubrication?

A

Constant supply of fresh lubricant
Slight pressurization reduces contamination
No moving parts
Alarm systems monitor flow and oil level
Low lubricant consumption
Lower bearing temperatures due to lower internal friction
Prevents moisture intrusion

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4
Q

Name three types of positive displacement pumps.

A

Reciprocal (piston)
Rotary (vane, lobe, gear, rotary screw, blower)
Diaphragm

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5
Q

Name four sources (not types) of contamination in a hydraulic system.

A

1) Built into comments
2) Generated during assembly, break-in and operation
3) External ingression
4) Introduced during maintenance

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6
Q

Hydraulic systems generally required fluid to be filtered through ______ to _____ micron filters.

A

3 to 10 microns

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7
Q

Name three factors that favor hydrodynamic lubrication.

A

High speed
Light loads
Oil of high enough viscosity

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8
Q

Name four desirable properties of “dielectric” oils commonly used in aerial lift devices (also called cherry pickers or bucket trucks).

A

Dielectric strength is not a legitimate test for this application and was voted out of the ANSI standards. It is more important for the oil to be clean and dry, to have a high viscosity index, low pour point, good anti-wear performance, and to be non-detergent.

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9
Q

How is it possible to change the flow rate of a pump?

A

Change the position of the cam ring.

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10
Q

What are good locations for filters and strainers in a hydraulic system?

A

Pump strainers (coarse filter on end of suction line)
Filter on pump suction line
Fine mesh pressure filter
Return line filter

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11
Q

Name four types of fire resistant hydraulic fluids.

A 
Oil-in-water
Emulsion 
Water-in-oil Invert emulsion
Water-glycol
Phosphate ester
Polyolester
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12
Q

What elastomers are compatible with phosphate ester hydraulic fluids?

A 
Ethylene propylene (EPM, EPMD, EPR)
Butyl
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13
Q

Pumps work on the principle of ________ volume at suction side and _________ volume at pressure side.

A

Increasing

Decreasing

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14
Q

List three disadvantages of water-glycol FR fluids.

A

1) Can be used only for moderate pressures
2) Incompatible with other fluids
3) Viscosity may increase as water evaporates (Limited viscosity available)
4) Incompatibility with zinc, cadmium, and magnesium
5) Poor corrosion protection (Corrosion problem)
6) Higher maintenance of fluid during service
7) Poor high temperature performance - low viscosity

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15
Q

What is the hydraulic system schematic symbol for a pressure relief valve?

A

Dk

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16
Q

What is the most hydraulic system schematic symbol for two working lines that cross and connect?

A

dk

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17
Q

What is the hydraulic system schematic symbol for flexible lines?

A

dk

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18
Q

What is the hydraulic system schematic symbol for a pump?

A

dk

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19
Q

What is the hydraulic system schematic symbol for a filter or strainer?

A

dk

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20
Q

Which type of hydraulic pump produces the greatest pressure?

A

Piston (reciprocating) pumps

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21
Q

Name two types of hydraulic actuators and what type of motion they have.

A

Cylinders - linear motion

Motors - circular motion

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22
Q

What is the purpose of baffles in a hydraulic reservoir?

A

It allows the fluid time to cool, de aerate, and to settle out water and dirt.

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23
Q

Most centrifugal pumps have a _________ and a _______ bearing.

A

Radial and thrust

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24
Q

Name three types of hydraulic pumps?

A

Gear
Vane
Piston
Screw

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25
Q

Name three causes that lead to failure of hydraulic pumps?

A

Aeration Excessive heat
Cavitation Improper fluid
Contamination Over pressurization

26
Q

What are the three causes of aeration in hydraulic systems?

A

Leakage on suction side pump
Oil splashing return line above oil in reservoir
Low oil level – vortex around suction line

27
Q

Name three types of fire resistant hydraulic fluids?

A

Water/Glycol
Phosphate esters
Invert emulsions

28
Q

Which type of hydraulic pump is most tolerant to dirty/contaminated lubricant?

A

Gear Pumps

29
Q

The control valves in a hydraulic system regulate the _________ ___ ______ of the hydraulic fluid.

A

Direction of flow

30
Q

What is the main purpose of the pressure relief valve?

A

Protect system from over pressurization

31
Q

Name the two types of hydraulic actuators and what type of motion they have?

A

Cylinders – Produce linear motion

Motors – Produce circular motion

32
Q

How are filters rated, by what two designations and what do they mean?

A

Beta ration – Number of certain size particles upstream of filter divided by Number downstream particles
Micron size – Size of particles trapped by filter

33
Q

What are the three methods of removing water from hydraulic systems?

A

Drain water from bottom of reservoir
Pass through a coalescing filter
Centrifuge
Vacuum dehydration

34
Q

Name six things a hydraulic reservoir should contain?

A

Filtered air Suction line screen
Strainer in filler opening Clean out facility
Filler cap with filter Fluid level indicator
Water drain

35
Q

A simple hydraulic jack consists of a small pump driven piston used to apply pressure through a fluid to a large piston, which supports the load. How can size of the load that can be lifted by the jack be increased?

A

Increase the area of the large piston that sees the pressurized oil.

36
Q

What needs to be checked if a hydraulic system is running with no work being done, but the oil temperature is the reservoir continues to increases?

A

Oil is returning to reservoir through a pressure relief valve.

37
Q

When working on a hydraulic system, on once the pumps have locked out, what two things must be checked before breaking any lines?

A

Determine if load supported

If there is an accumulator that may be pressurized.

38
Q

Name four sources ( not types ) of contamination in a hydraulic system.

A
  1. Built into components of equipment
  2. Generated during assembly, break-in and operation
  3. External ingression
  4. Introduced during maintenance.
39
Q

The viscosity of circulating oil has increased. Name three reasons why this may occur, assuming no water is emulsified in the system.

A

The oil may have oxidized. Pressure could have increased. Temperature might have decreased. There may be contamination with a higher viscosity fluid. Evaporative losses of light oil fractions from high temperatures, glycol contamination, soot contamination.

40
Q

What needs to be checked if a hydraulic system is running with no work being done, but the oil temperature in the reservoir continues to increase?

A

Oil is returning to the reservoir through a pressure relief valve

41
Q

Clearance sized particles have what three effects on valves?

A 
Surface erosion
Solenoid burn-out
Spool jamming
Slow response/instability
Silt lock
Stiction
42
Q

What are eight component of a hydraulic system?

A

Reservoir Pump
Fluid conductors Fluid
Filters Directional valves
Actuator Pressure relief valve

43
Q

Why is it important to use a distilled water when adding water to a water-glycol system?

A

Minerals in the tap water can form soaps from additives.

44
Q

What is the operating temperature range of water-glycol fluids?

A

0° F – 140° F.

45
Q

Why place additional filters ahead of critical, sensitive components?

A

Extend component life, reduce wear, prevent valve stiction.

46
Q

What is a pressure head?

A

Pressure from the weight of the fluid.

47
Q

_______________ pressure is the point at which a hydraulic line yields.

A

Burst

48
Q

Name two functions of an accumulator.

A

It serves as a buffer to absorb impulses and allows rapid release of fluid flow.

49
Q

What is the typical range of the percent of water found in a water-glycol hydraulic fluid?

A

35-50%

50
Q

What is a Reynold’s number?

A

A dimensionless number that indicates the relative amount of turbulence of fluid flow. It is a function of fluid viscosity, velocity and density.

51
Q

Which type of hydraulic pump is most tolerant of dirt?

A

Gear pump

52
Q

The control valves in a hydraulic system regulate the ______ of the fluid.

A

Flow

53
Q

Name three root causes of hydraulic pump failures.

A

Contamination
Improper installation
Improper fluid

54
Q

What is a hydraulic pump? A device that converts mechanical energy of a prime mover (electric motor) into hydraulic, working energy (flow and pressure).

A

A device that converts mechanical energy of a prime mover (electric motor) into hydraulic, working energy (flow and pressure).

55
Q

What are four functions of a hydraulic fluid?

A 
Transmit power
Lubricate
Transfer heat
Seal clearances
Remove contaminants
Protect against rust and corrosion
56
Q

A red fire-resistant hydraulic fluid is generally what type?

A

Water glycol

57
Q

List three symptoms of pump cavitation.

A

Noise
Wear particles
Vibration

58
Q

What is a hydraulic motor?

A

A rotating hydraulic actuator

59
Q

What is an actuator?

A

Converts hydraulic energy into mechanical energy

60
Q

The main function of a hydraulic oil is to?

A

Transmit power

61
Q

A hydraulic system is making a sound like rattling marbles, what is it? What are some possible causes?

A 
Cavitation
Air leak inlet side of pump
Excessive foam
Excessive heat
Suction too high
Fluid level too low.
62
Q

What do you take into account when selecting a fluid for a new system?

A 
Type of pump
System operating temperature
Working pressure
Ambient temperatures
Start- up temp
63
Q

We have an emergency situation on a Sunday. A system has broken a hose and lost the hydraulic fluid. It was using an ISO AW 32 but there is none in stock. You have ISO 68 AW and SAE IOW motor oil. The system is the garbage compactor. Which fluid should you use?

A

SAE 10W

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