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RJ Hydraulics > Filters, Hoses, Coolers > Flashcards

Filters, Hoses, Coolers Flashcards

0
Q

Why should hydraulic oils never be mixed?

A

The additive of the oils may be different

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1
Q

What are 4 main properties of hydraulic oil?

A

Transmit Power
Lubricate
Seal
Cool

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2
Q

What is viscosity index?

A

A measure of the amount of viscosity change oil will experience as ambient temperature changes.

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3
Q

What does a it mean when an oil has a high viscosity index (VI)?

A

Viscosity changes very little over a wide temperature range.

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4
Q

Viscosity Index is indicated how?

A

On a scale of 0-100.

The greater the number the more stable oil is.

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5
Q

Hydraulic oil should have a VI of what?

A

At least 90

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6
Q

What is pour point?

A

The lowest temperature at which the oil will will flow

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7
Q

The pour point of hydraulic oil should be what?

A

At least 11.1C (20F) below the lowest temperature it will be exposed to?

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8
Q

How is lubrication accomplished in hyd. System?

A

A film of oil that occupies the clearance between moving parts

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9
Q

What must be prevented to extend the life of hydraulic oil?

A

Oxidation
Corrosion and rust
Foaming and emulsion

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10
Q

What are three ways to measure viscosity?

A

Absolute viscosity
Kinematic viscosity
Relative viscosity

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11
Q

What are 3 major functions preformed by hydraulic reservoir?

A
  1. Hold the system oil supply
  2. Cool oil
  3. allow air and contamination to separate from the oil
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12
Q

What is considered ideal oil reservoir size?

A

2-3 times the rated flow of the pump

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13
Q

The rule of thumb for reservoirs on mobile equipment is:

A

Must be able to keep inlet line submerged.

Hold all of the oil that will drain back into reservoir by gravity flow

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14
Q

How does a hydraulic reservoir cool the oil?

A

Heat is transferred to the walls, it is radiated from walls to atmosphere.

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15
Q

When air separates from the oil in the reservoir it is known as?

A

De-aeration

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16
Q

What is sedimentation?

A

The process of allowing the solid contamination to settle out of the oil

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17
Q

What are 2 most common types of reservoirs used on mobile equipment?

A
  1. Vented or atmospheric

2. Pressurized or closed

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18
Q

In vented reservoir, what can happen if there is reduced pressure in reservoir?

A

The reduced pressure at pump inlet could cause cavitation damage to the pump

19
Q

What pressure is used in a pressurized reservoir?

A

Usually 10-15 PSI

20
Q

What are most common methods of checking oil level?

A

Dipstick

Sight glass

21
Q

Lines entering the hydraulic reservoir must:

A

Terminate below the fluid level

22
Q

Why should the return line be cut at a 45* angle?

A

To direct hot oil towards the wall and away from the inlet line

23
Q

What are the 3 main purposes of a baffle plate inside of a reservoir?

A
  1. Forces return oil to flow along the reservoir walls, help dissipate heat.
  2. Slows velocity of return oil so it has time for air and contamination to settle out.
  3. Prevents sloshing
24
Q

What is the clearance in a low pressure hydraulic system?

A

About 10-20 microns

25
Q

What is clearance of high pressure components?

A

Up to 5 microns

26
Q

Solid contaminants interfere by:

A

Restricting or plugging orifices, forming sludge, affects lubricating ability- results in damage to precision surfaces

27
Q

What are 3 sources of contamination in HYD. oil?

A
  1. Built-in contamination
  2. Ingressed contamination
  3. Internally generated contamination
28
Q

What is each source of contamination made up of?
Built-in
Ingressed
Internally generated

A

Contamination from factory assembly.
Contamination from being serviced.
Parts in system wearing from time, cavitation, surface fatigue

29
Q

How are filtering devices rated?

A

Their degree of filtration

30
Q

What is most common filter media used for fine filtration

A

Pleated paper

31
Q

What is extremely fine filter media usually made of?

A

Mass of very small diameter synthetic fibres

32
Q

Absolute rating?

A

Refers to the smallest particle that a filter will completely remove from the oil flow.

33
Q

Is it better to have a beta rating that is higher or lower?

A

The higher the better

34
Q

How does beta rating work?

A

Rating for particular size= 100% - #particles down stream filter/ #particles upstream filter
Ex. 50 up, 1 down = 98%

35
Q

Where is most common location for filter?

A

In return line.

However can have high pressure filter down of pump

36
Q

What does the term hydraulic conductors refer to?

A

The pipes, tubing, hoses, and related fittings that carry oil

37
Q

What are the three most commonly used conductors?

A
  1. Steel pipe
  2. Steel tubing
  3. Hydraulic hose
38
Q

Pipe sizing

A

NPT:
Schedule
Nominal size
I.D.

39
Q

Tube sizing

A

O.D.
Dash #
Each dash is 1/16 in

40
Q

Hyd. Hose sizing

A

I.D.
Dash # system
Each dash is 1/16 in

41
Q

Most common flare angles

A

JIC-37*

SAE-45*

42
Q

What is ORB

A

O-ring boss.

Use O-ring to seal rather then sealant

43
Q

What are 2 types of hydraulic hose connectors?

A
  1. Permanent

2. Reusable

44
Q

The amount of heat is hyd. System depends on:

A
  1. System efficiency

2. System duty cycle

45
Q

What is most common type of hyd. oil cooler?

A

Oil-to-air cooler.

Commonly connected in series in return system and place in front of engine radiator

46
Q

Boundary lubrication refers to a condition where:

A

Minute imperfections on the surfaces of moving parts are in contact

RJ Hydraulics (3 decks)

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