Filters, Hoses, Coolers

Question 0

Why should hydraulic oils never be mixed?

Answer 0

The additive of the oils may be different

Question 1

What are 4 main properties of hydraulic oil?

Answer 1

Transmit Power
Lubricate
Seal
Cool

Question 2

What is viscosity index?

Answer 2

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

Question 3

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

Answer 3

Viscosity changes very little over a wide temperature range.

Question 4

Viscosity Index is indicated how?

Answer 4

On a scale of 0-100.

The greater the number the more stable oil is.

Question 5

Hydraulic oil should have a VI of what?

Answer 5

At least 90

Question 6

What is pour point?

Answer 6

The lowest temperature at which the oil will will flow

Question 7

The pour point of hydraulic oil should be what?

Answer 7

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

Question 8

How is lubrication accomplished in hyd. System?

Answer 8

A film of oil that occupies the clearance between moving parts

Question 9

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

Answer 9

Oxidation
Corrosion and rust
Foaming and emulsion

Question 10

What are three ways to measure viscosity?

Answer 10

Absolute viscosity
Kinematic viscosity
Relative viscosity

Question 11

What are 3 major functions preformed by hydraulic reservoir?

Answer 11

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

Question 12

What is considered ideal oil reservoir size?

Answer 12

2-3 times the rated flow of the pump

Question 13

The rule of thumb for reservoirs on mobile equipment is:

Answer 13

Must be able to keep inlet line submerged.

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

Question 14

How does a hydraulic reservoir cool the oil?

Answer 14

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

Question 15

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

Answer 15

De-aeration

Question 16

What is sedimentation?

Answer 16

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

Question 17

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

Answer 17

1. Vented or atmospheric

2. Pressurized or closed

Question 18

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

Answer 18

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

Question 19

What pressure is used in a pressurized reservoir?

Answer 19

Usually 10-15 PSI

Question 20

What are most common methods of checking oil level?

Answer 20

Dipstick

Sight glass

Question 21

Lines entering the hydraulic reservoir must:

Answer 21

Terminate below the fluid level

Question 22

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

Answer 22

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

Question 23

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

Answer 23

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

Question 24

What is the clearance in a low pressure hydraulic system?

Answer 24

About 10-20 microns

Question 25

What is clearance of high pressure components?

Answer 25

Up to 5 microns

Question 26

Solid contaminants interfere by:

Answer 26

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

Question 27

What are 3 sources of contamination in HYD. oil?

Answer 27

1. Built-in contamination 2. Ingressed contamination 3. Internally generated contamination

Question 28

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

Answer 28

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

Question 29

How are filtering devices rated?

Answer 29

Their degree of filtration

Question 30

What is most common filter media used for fine filtration

Answer 30

Pleated paper

Question 31

What is extremely fine filter media usually made of?

Answer 31

Mass of very small diameter synthetic fibres

Question 32

Absolute rating?

Answer 32

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

Question 33

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

Answer 33

The higher the better

Question 34

How does beta rating work?

Answer 34

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

Question 35

Where is most common location for filter?

Answer 35

In return line. | However can have high pressure filter down of pump

Question 36

What does the term hydraulic conductors refer to?

Answer 36

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

Question 37

What are the three most commonly used conductors?

Answer 37

1. Steel pipe 2. Steel tubing 3. Hydraulic hose

Question 38

Pipe sizing

Answer 38

NPT: Schedule Nominal size I.D.

Question 39

Tube sizing

Answer 39

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

Question 40

Hyd. Hose sizing

Answer 40

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

Question 41

Most common flare angles

Answer 41

JIC-37* | SAE-45*

Question 42

What is ORB

Answer 42

O-ring boss. | Use O-ring to seal rather then sealant

Question 43

What are 2 types of hydraulic hose connectors?

Answer 43

1. Permanent | 2. Reusable

Question 44

The amount of heat is hyd. System depends on:

Answer 44

1. System efficiency | 2. System duty cycle

Question 45

What is most common type of hyd. oil cooler?

Answer 45

Oil-to-air cooler. | Commonly connected in series in return system and place in front of engine radiator

Question 46

Boundary lubrication refers to a condition where:

Answer 46

Minute imperfections on the surfaces of moving parts are in contact