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Fluid Power > T2 > Flashcards

T2 Flashcards

1
Q

What causes oil temperature to increase when it leaves the PRV’s?

A

Pressure decreases while temperature increases

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2
Q

Why should inside the surface of a control valve be smooth?

A

To reduce pressure drops inside the valve

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3
Q

List the 2 types of internal forces used to control the internal elements of a control valve.

A

Springs & pilot pressure

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4
Q

3 basic functions of springs in control valves

A
  1. Moving the spool in a DCV
  2. Setting maximum pressure in a PCV
  3. Serving as a biasing device in pressure compensated control valves
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5
Q

Are pressure reducing valves normally open or normally closed?

A

Normally open

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6
Q

What is an internally drained system

A

Oil is allowed to drain back to the return line

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7
Q

What is an externally drained system

A

Fluid is allowed to drain directly to the reservoir and seperate from the supply line

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8
Q

Two functions performed by pressure in control valves

A
  1. Control the force
    2 Protect the system from damage
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9
Q

What is cracking pressure

A

The minimum required pressure to provide non zero volume flow rate

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10
Q

Define full flow pressure

A

The maximum pressure reached by the springs setting to allow maximum volume flow rate

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11
Q

What is override pressure

A

The difference between full flow and cracking pressure

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12
Q

Are pressure relief valves normally open or normally closed?

A

Normally closed

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13
Q

What are sequence valves

A

Valves that allow the operation of actuators in specified order

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14
Q

What are the two internal modes of operation for PCVs

A
  1. Direct operated valves
  2. Balancing piston valves
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15
Q

What is lubricity

A

A measure of friction reduction between moving parts

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16
Q

How does liquids and gases viscosity change with increasing temperatures

A

Liquids viscosity decreases
Gases viscosity increases

17
Q

What is pour point of a fluid

A

Pour point is the temperature below which the fluid loses its flow characterisitics

18
Q

How would fluids viscosity be an advantage in a hydraulic system

A

Viscosity contributes to pressure drop along piping and in different components.

19
Q

Why should mechanical couplers be aligned between prime movers and the pump

A

To reduce noise and inefficiency in transmitting power

20
Q

Why is a strainer installed in a hydraulic tank

A

To screen out large objects before the fluid enters the pump

21
Q

Why do shafts in an unbalanced vane pump require radial bearings

A

The pressure difference between the higher and lower pressure chambers create radial force on the rotors shaft

22
Q

What is foaming in oil

A

Air bubbles in oil

23
Q

What causes foaming in oil

A

Too much movement in the tank and if the return line is above the fluid level

24
Q

5 main functions of a reservoir in a hydraulic system

A
  1. Storage
  2. Filtration
  3. Removes excess thermal energy
  4. Releases air trapped in fluid
  5. Remove water from fluid
25
Q

Which has higher flow speeds: conductor or inside the tank

A

Conductors

26
Q

4 functions of a baffle plate

A
  1. Absorbs heat
  2. Causes bubbles to stick to it
  3. Creates a longer path for the oil so the water and particles can settle
  4. Stops direct flow
27
Q

Why is there a breather on top of hydraulic tanks

A

For air exchange to compensate for change in oil volume duting fluid circulation

28
Q

Why should the tank be above pump level

A

1.Keeps the pump primed
2. More pressure at the pump inlet
3. Minimizes the chances for cavitation to occur

29
Q

What is shock pressure

A

A sudden increase in fluid pressure

30
Q

Two reasons shock pressure could develop

A
  1. An actuator is overloaded
  2. DCV is centered or reversed
31
Q

What is effective piston cross section area

A

Piston area minus rod area

32
Q

L/m conversion

A

L/m ÷ 60,000 m3/s

33
Q

Pa from Psi

A

psi × 6897.2

= Pa

34
Q

Single acting cylinder vs double acting

A

Single allows for pressurized oil to enter from only one sidr of the cylinder. Double allows it to enter from both sides of the piston

35
Q

Piston rod area

A

m²

36
Q

Force

A

N

37
Q

What is corrosion

A

The process by which damage is caused to metals and non metals

38
Q

What is rust

A

Oxidation that occurs only to metals. Rust requires water + oxygen

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