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A rubber return line keeps breaking. What are the possible causes?

Incompatibility of the rubber to the fluid, heat, substandard material, incorrectly sized.

1

A machine operator complains of dermatitis. What are some causes and possible remedies?

Over exposure to a chemical or petroleum product. Minimize exposure to the product by removing the person from the area or by using gloves and/or protective clothing. Use good personal hygiene. Wash on a regular basis, keep clean, and use barrier creams properly as necessary.

2

An engine oil has thickened considerably. Oil analysis shows elevated levels of sodium and potassium. What has happened?

Probably contamination with coolant has accelerated oxidation of the oil.

3

A strainer blows out in a hydraulic system. What are some reasons why?

Most likely it is sabotage where someone wanted to increase flow rate and poked a hole in it, but it may also be due to improper installation. If it is an inlet strainer, it’s possible, although unlikely, that it may have plugged and collapsed.

4

The viscosity of circulating oil has decreased. Name three reasons why this may occur.

Contamination with a lower viscosity oil, air entrainment, thermal cracking, shear of the VI improver, contamination with very large amounts of water.

5

The viscosity of circulating oil has increased. Name three reasons why this may occur, assuming no water is emulsified in the system.

The oil may be oxidized. There may be contamination with a higher viscosity fluid. Also, if the viscosity increases while the oil is circulating, it might be a result of lower temperatures or much higher pressure.

6

A bearing has failed. After it is removed and cleaned, it was noticed that the cage was dark blue. What conclusions can you make from the observation?

The bearing overheated.

7

What are five indicators that a bearing has failed or is getting ready to fail?

Increase in heat
Noise
Vibration
Odor
Discoloration
Wear metals in oil analysis

8

As you enter an area where a piece of machinery is being used, what kind of information can be gathered with the use of your hands, ears, and nose?

Feel for vibration, heat. Listen for unusual noises, i.e. vibration and metal to metal. Notice unusual odors. Look for leakage, oil level, oil consistency and color.

9

What two things can cause a lubricant to appear milky?

Water and entrained air are the most common; also polymers and other contaminants.

10

Name three factors that can accelerate degradation of a lube oil in service.

High temperatures, aeration, additive depletion, mixing of lubricants, presence of contaminants such as water, presence of copper or other catalytic metals.

11

Name three causes of excessive foaming in a circulating oil or hydraulic system.

Contamination
Mechanical causes
Insufficient reservoir settling time

12

A simple hydraulic jack consists of a small pump-driven piston used to apply pressure through a fluid to a large piston that supports a load. How can the size of the load that can be lifted by the jack be increased?

Change the pump for a high pressure, higher capacity pump. Increase the size of the piston.

13

What needs to be checked if a hydraulic system is running with no work being done, but the oil temperature in the reservoir continues to increase?

Oil is returning to the reservoir through a pressure relief valve. Check the system pressure relief valve. It may be set too low.

14

When working on a hydraulic system, once the pumps have locked out, what two things must be checked before breaking any lines?

Electrical tag-out
Accumulator bled off
No load supported

15

Oil is received with a cloudy appearance. When it was loaded it was bright and clear. What could have happened?

The oil could have been loaded at a high temperature location and shipped to a low temperature location. As the oil cooled in transit, dissolved water came out of solution.

16

What are the questions you should ask when investigating a foaming problem?

How long has the foam been a problem?
How bad is the foam?
Are there signs of air entrainment?
Does it dissipate rapidly?
Are you maintaining proper oil level?
Is there possible contamination?

17

A sample of diesel engine oil appears black. What are the two most likely causes?

Soot and oxidation

18

Inadequate lubrication may be due to:

Plugged filters

19

The oil analysis report for a piece of equipment shows wear. Other than changing the viscosity of the lubricant what can be done?

Use oil with higher VI
Decrease temperature
Increase speed
Check for mechanical problems
Increase lubricant flow rate

20

A customer calls to advise that the discharge line from his reciprocating compressor has a series of holes 3’ to 4’ apart. What questions do you ask?

Where are the holes, tops, sides or bottom?
How old are the lines?
What gas is being compressed?
Was there anything leaning against or supporting the lines?
Did it look like the holes were the result of abrasion, rust or corrosion? Was the compressor generating a harmonic vibration?

21

Oil starts spewing out of an expansion tank of a heat transfer system as it is brought up to temperature. What probably happened?

The oil was contaminated with water. As the temperature reached 100°C, the oil started to boil off taking the oil with it.

22

The following oil analysis data indicates what likely contaminant in hydraulic oil? High calcium, magnesium, zinc and phosphorous

Engine oil contamination

23

If you were trying to replace grease in a bearing in a high water environment, what three tests would you run to predict better performance?

Water washout
Water spray off
Rust

24

What are three things to look for if a water-soluble hydraulic fluid filter plugs?

Soap scum
Fungus or mold
Dirt and debris
Ice if cold temperatures

25

You have been notified that an engine has failed prematurely. What five pieces of information can help determine the cause of the failure?

Maintenance history of engine
Operating environment
Historical and current oil analysis reports
Operator’s report about unusual noises, fuel consumption, oil consumption what was noticed just prior to failure
Engine components for failure analysis

26

What are three causes of aeration in hydraulic systems?

Leak on suction line
Fluid returning above fluid level in reservoir
Inadequate dwell time
Contaminants

27

One grease line plugs and the rest quit working, why?

The system is a series progressive system with performance monitoring designed to shut down until the line is repaired.

28

What is cavitation?

The sudden formation and collapse of low-pressure bubbles.

29

How can you tell if cavitation is occurring?

Vibration
Loss of pressure or inconsistent pressure noise from the pump (sounds like marbles).