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Class 6 AAP > Hydraulic Final > Flashcards

Hydraulic Final Flashcards

(98 cards)

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1
Q

What is hydraulic fluid?

A

The substance used for transmitting energy from the pump actuator in a hydraulics system.

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2
Q

What is lubrication?

A

The process of reducing friction between relatively moving surfaces which are in contact.

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3
Q

What are the 4 things hydraulic fluid does?

A
  1. Transmit Power
  2. Lubrication
  3. Cools Moving Parts
  4. Seals Clearances
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4
Q

What is a fluid film?

A

The coating of hydraulic fluid which prevents contact between moving parts in a hydraulic system

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5
Q

What is lubricity?

A

A liquids ability to form a durable fluid film.

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6
Q

What are the 2 factors which relate to lubricity?

A
  1. A fluids natural film thickness
  2. A fluids tendency to adhere to a surface
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7
Q

What are 2 primary causes for cavitation?

A
  1. Cold/Thick hydraulic fluid
  2. Obstruction of the inlet
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8
Q

What is auto ignition temperature?

A

Temperature at which hydraulic fluid ignites without a flame or spark. (Spontaneous combustion)

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9
Q

What are the 7 steps to set the pressure compensator and relief valve?

A
  1. Block flow to system
  2. Set relief valve to 150PSI
  3. Run compensator all the way in
  4. Set relief valve to specified pressure (250 above)
  5. Set pump compensator to specified pressure
  6. Lock down jam nuts
  7. Open flow to circuit
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10
Q

What are the 2 types of fire resistant hydraulic fluids?

A
  1. Water Based
  2. Synthetic
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11
Q

What is water-oil emulsion?

A

Oil is broken down and encapsulated by water using an emulsifier. Typically 60% water to 40% oil.

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12
Q

What is inverted emulsion?

A

Water is broken down and encapsulated by oil using an emulsifier. Typically 60% oil to 40% water. (Also known as Morg Oil)

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13
Q

What is a problem with Phosphate Ester?

A

Corrosion

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14
Q

What are the 2 problems specific to invert emulsion?

A
  1. Phase Separation
  2. Bacteria Formation
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15
Q

What is water glycol?

A

A water based fire resistant hydraulic fluid which consists of 60% glycol and 40% water. (Since glycol is similar to antifreeze, this works at low temperatures)

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16
Q

How should hydraulic fluid be stored?

A

Inside. Barrels on the side or with covers to prevent contamination.

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17
Q

Which pumps have a set volume?

A

Fixed displacement pumps

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18
Q

Which pumps change volume?

A

Variable displacement pumps

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19
Q

What do vanes pumps do?

A

Generate a pumping action by causing vanes to track along a ring

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20
Q

How do vanes pumps operate?

A

As the rotor turns, vanes are thrown out. These vanes track along a stationary ring, causing a positive seal.

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21
Q

What are the 3 styles of vanes pumps?

A
  1. Unbalanced
  2. Balanced
  3. Cartridge
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22
Q

What is the problem with unbalanced vane bearings?

A

Susceptible to side loading. Require thrust bearing.

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23
Q

How do balanced vane pumps prevent issues associated with unbalanced?

A

Pressure on both sides of the shaft, preventing thrust load.

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24
Q

What is a cartridge vane pump?

A

Vane pump in which the vanes and housing are contained in a cartridge assembly, which can be easily replaced.

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25
What must happen before a vane pump can operate properly?
A positive seal must exist between vane tip and cam ring.
26
Can all hydraulic motors be pumps?
Yes
27
Can all pumps be hydraulic motors?
No
28
What must a pump have in order to be used as a hydraulic motor?
High pressure seal.
29
What are the 4 DCV center conditions in hydraulics?
•Open Center •Tandem Center •Block Center •Float Center
30
What are the characteristics of Open Center DCVs?
Zero pressure, can't stop motion
31
What are the characteristics of Tandem Center DCVs?
Zero pressure, can stop motion
32
What are the characteristics of Block Center DCVs?
System pressure, can stop motion. Should not be used to hold load.
33
What are the characteristics of Float Center DCVs?
System pressure, can't stop motion
34
Why shouldn't you use a Block Center DCV to hold a load?
Seal can begin to wear, allowing leakage through the DCV. Can lead to drifting.
35
What are the 3 most common DCV Mounting styles?
DO3, DO5, and DO8
36
How can you stop motion with a Float Center DCV?
Piloted Check Valve
37
Why would we use piloted check valves?
Allow free flow in 1 direction, and some flow in the other direction, when pilot pressure is achieved.
38
Why would we use Pilot Operated, Solenoid Controlled DCVs?
Pilot Pressure helps the Solenoid shift spools which require more pressure to shift.
39
What are chokes used for?
Create a delay in spool shifting in order to eliminate shock.
40
Do chokes control cylinder speed?
No
41
What are the 3 types of accumulators?
Weight Loaded, Spring Loaded, and Hydro Pneumatic
42
What is the most common accumulator type?
Hydro Pneumatic
43
How are accumulators charged?
Nitrogen
44
What are accumulators for?
Maintain pressure, supplement flow, and absorb/reduce shock.
45
What is the minimum an accumulator should be set at?
1/4 of system pressure
46
What percentage of the pressure needed to lift the load should you use to set the accumulator?
0.9
47
What percentage of system pressure should you set the accumulator at for shock absorption?
0.5
48
What components in a hydraulic system are connected directly to the main system pressure and do not create a full flow path?
•Accumulator •Pressure Switches •Pressure Gauges
49
What is 1 con to weight loaded accumulators?
Can generate shock
50
What are Sequence Valves used for?
Casuing 1 operation to occur before another.
51
What are the characteristics of Sequence Valves?
•Normally Non Passing •In 1 •Out 2 •3 port vented back to tank •Requires check valve for back flow
52
How is a Sequence Valve set?
PSI, using pressure gauge
53
What are Counter Balance Valves used for?
Control flow from the vertical cylinder to prevent drift and cavitation. (Pressure controlled flow control valve)
54
What are the characteristics of a Counterbalance Valve?
•Normally Non Passing •In 1 •Out 2 •3 goes to rod end of cylinder
55
How is a Counterbalance Valve set?
Adjusted while observing cylinder drift.
56
What are Simple Relief Valves for?
System pressure relief valve which allows flow back to tank once a certain pressure is achieved.
57
What are the characteristics of a Simple Relief Valve?
•Normally Non Passing •In 1, tee into system •Out to tank from 2
58
How are Simple Pressure Relief Valves set?
Set using pressure gauge, adjusting the gauge, and the pump displacement on an adjustable pump.
59
What are Pressure Reducing Valves used for?
Used to reduce downstream pressure in order to soften the pressure exerted by a cylinder or other hydraulic device.
60
What are the characteristics of Pressure Reducing Valves?
•Normally Passing •In 2 •Out 1 •3 port connected back to tank
61
How are Pressure Reducing Valves set?
Adjusting the knob while using a pressure gauge
62
Which valve is more precise, simple relief valve, or direct relief valve?
Simple.
63
Which valve is more precise, pilot operated relief valve , or direct relief valve?
Pilot operated (Far more)
64
Which valve is the only one which is normally passing?
Pressure Reducing
65
Which valve requires a check valve for back flow?
Sequence Valve
66
Where is a Simple Relief Valve typically placed in a system?
Directly after the pump.
67
Where is a Counter Balance Valve typically placed in a system?
Directly after/before the vertical cylinder.
68
What is required if you want to put a sequence valve in a system 2 cylinders to extend 1 at a time, but retract simultaneously?
Bypass Check Valve
69
A fixed displacement pump must have what to limit system pressure?
Relief valve
70
Purpose of a relief valve?
Limits system pressure
71
How are packing rings supposed to be cut?
At an angle leaving no gaps in the ring.
72
One of the oldest and most widely used seal is what?
Stuffing box/Gland Packing
73
Where does the lantern ring need To be positioned?
Directly under the Inlet port
74
2 types of seals?
Compression packing and mechanical seal
75
3 types of impeller styles?
Enclosed, semi open and open
76
What are the components of a stuffing box seal system?
Stuffing Box Gland follower Rings of packing Lantern ring
77
What is the meaning of head?
Height of a liquid
78
3 things that determine the capacity of a pump?
1. Size of impeller 2. Speed of impeller 3. Viscosity of liquid
79
A positive pressure at the pump Inlet?
Positive head
80
The distance which the pump lifts the liquid
Total head
81
Distance that the liquid must be lifted to the pump?
Negative head
82
What is the definition of pumps?
Lifts liquids against gravity or exhausts gasses.
83
What unit are industrial pumps rated in?
GPM (Gallons Per Minute)
84
What 3 things determine pumps capacity?
RPM of pump Viscosity of liquid Impeller size
85
What is a pumps capacity?
Amount of fluid a pump can move in a given time
86
What is discharge head?
The pressure at discharge
87
What do vanes do?
Guide liquid to outside of the housing
88
What are the 2 common case designs?
Split Case and Endsuction
89
What is the disadvantage of endsuction pumps?
Create thrust load, which causes the need for better bearings
90
How do split casing pumps avoid thrust load?
Liquid is on both sides of impeller
91
What are the rings on either side of the impeller in a split casing pump?
Wear Rings
92
What is the purpose of wear rings?
Wear out before other pump components
93
What is pressure?
Force Per Unit Area or lbs/sq in
94
What is Suction Head?
Positive Head (Pressure created from fluid coming from above pump inlet)
95
What is Suction Lift?
Negative Head (Pressure created from fluid coming from below pump inlet, needs primed)
96
How do positive displacement pumps operate?
Volume changes from maximum to minimum during cycles.
97
Is the total head higher or lower typically on a pump with positive head?
Higher
98
Is the total head higher or lower typically on a pump with nagative head?
Lower

Class 6 AAP (31 decks)

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