T3 Flashcards

1
Q

What is sludge?

A

A thick gel-like two-phase substance composed of liquid and solid particles

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2
Q

Two situations where fluid temperature increases

A

-Increases during operation due to pressurization of the oil
-Increases when the fluid expands as it leaves the pressure relief valve

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3
Q

State the main difference between absorbent and adsorbent depth-type filters.

A

-Absorbent filters mechanically trap contaminants in oil
-Adsorbent filters mechanically trap contaminants and chemically remove them

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4
Q

Why are absorbent filters not used in hydraulic systems?

A

They may remove important additives from oil

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5
Q

What are filter condition indicators?

A

They sense the pressure difference between the filter inlet and outlet.

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6
Q

Where are filters placed in a hydraulic circuit?

A

-Pump inlet
-Working lines between pump and actuator
-On the return line before entering the reservoir

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7
Q

What is the main difference between sump strainers and suction filters in terms of their location?

A

-Sump strainers are installed at the pump inlet
-Suction filters are installed above the fluid level in the tank.

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8
Q

Why should suction filters be carefully inspected and replaced once clogged?

A

The clogged filter causes more reduction to the vacuum pressure at the pump inlet.

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9
Q

List 3 types of heat exchangers used in a hydraulic system.

A

-Radiators and finned conductors
-Shell and tube
-Immersion heat exchangers

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10
Q

How is the housing of working line filters different from return line filters?

A

The housing of working line filters are designed to stand the high working fluid pressure.

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11
Q

What is the purpose of fins on some types of heat exchangers?

A

The fins increase the exposed surface area for more heat transfer.

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12
Q

Which is more efficient in transferring heat: Liquid to liquid or air to liquid heat exchangers?

A

Liquid to liquid

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13
Q

Why are immersed electric heaters equipped with thermostats?

A

To limit the amount of heat delivered to the fluid. This helps avoid overheating.

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14
Q

What are two ways by which contaminants enter the system during operation?

A
  1. Dust may enter the system during rod retraction
  2. Dust and moisture could enter through the tank breather
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15
Q

What should be done to the system to ensure an adiabatic process?

A

The system should be perfectly insulated so no heat transfer is allowed.

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16
Q

What are the four main processes required for conditioning air?

A

-Removing entrapped dirt
-Removing water vapour
-Removing thermal energy
-Adding oil for component lubrication

17
Q

Which carries less humidity; warmer or cooler air

A

Cooler air

18
Q

What happens to excess amounts of water if the humidity is at 100%?

A

The excess amount of water condenses as water droplets

19
Q

Should the lubricating oil be introduced between the compressor and the receiver?

A

No, it should be introduced before entering the working station

20
Q

What is an isothermal process?

A

If heat is removed during the compression, temperature stays constant

21
Q

What is an adiabatic process?

A

The process in which heat is not exchanged with the system.

22
Q

5 main layers of the atmosphere

A

-Exosphere
-Thermosphere
-Mesosphere
-Stratosphere
-Troposphere

23
Q

What is the approximate percentage of nitrogen and oxygen by volume at the sea level in the atmosphere?

A

78% Nitrogen
21% Oxygen

24
Q

What is the main difference between a pressure relief valve and a sequence valve in terms of drain?

A

Sequence valves always have an external drain line.

25
Q

What are the most common types of shutoff valves?

A

-Globe
-Gate
-Ball
-Spool and needle

26
Q

What are the two most common types of check valves?

A

In line and right angle

27
Q

List the two types of flow control devices

A

Restrictor and bypass control

28
Q

3 Types of gas charged accumulators

A

-Piston
-Bladder
-Diaphragm

29
Q

Why should only inert gas be used in gas charged accumulators?

A

Because they do not react to the rubber layer or oil if exposed to the oil

30
Q

List the 5 most common center positions in a four way three position

A

-Closed center
-Open center
-Tandem center
-Floating center
-Regenerative center

31
Q

Two functions the stored energy in accumulators could be used in

A

-Maintain system pressure
-Supplying fluid to other secondary circuits when a pump is down

32
Q

What are three parameters that characterize accumulators?

A

-Weight loaded
-Spring loaded
-Gas charged

33
Q

Why is a spring loaded poppet is installed at the oil port in bladder accumulators?

A

To prevent the bladder from moving into the poil port if the gas pressure excessively surpasses oil pressure

34
Q

How would temperature change with rapid charging of gas accumulators?

A

It causes the gas molecules to have more friction, leading to increased temperature

35
Q

Classify DCV’s based on how the flow is directed

A

-Shutoff valves
-Check valves
-Three way valves
-Four way valves