Amazon Maintenance Technician Hydraulics & Pneumatics Systems 2 — Questions and Answers
Question 1: What condition is indicated by milky or cloudy hydraulic fluid?
- High oil temperature
- Water or air contamination in the fluid (Correct answer)
- Correct fluid viscosity
- Low additive concentration
Correct answer: Water or air contamination in the fluid
Milky or cloudy hydraulic fluid indicates water contamination or aeration, both of which reduce lubrication and can cause cavitation.
Question 2: What is cavitation in a hydraulic pump, and what typically causes it?
- Overheating caused by high ambient temperature
- Formation and collapse of vapor bubbles caused by low inlet pressure (Correct answer)
- Seal failure due to high pressure
- Contamination from metal particles
Correct answer: Formation and collapse of vapor bubbles caused by low inlet pressure
Cavitation occurs when inlet pressure drops below the fluid's vapor pressure, forming bubbles that collapse violently and erode pump components.
Question 3: In a pneumatic system, what is the purpose of the lubricator in the FRL unit?
- Remove moisture from compressed air
- Regulate downstream pressure
- Inject oil mist to lubricate downstream components (Correct answer)
- Filter particulates above 5 microns
Correct answer: Inject oil mist to lubricate downstream components
The lubricator in the Filter-Regulator-Lubricator unit injects a fine oil mist into the air stream to lubricate valves, cylinders, and other pneumatic components.
Question 4: Which type of hydraulic cylinder produces force in one direction and relies on gravity or a spring for the return stroke?
- Double-acting cylinder
- Single-acting cylinder (Correct answer)
- Telescoping cylinder
- Tandem cylinder
Correct answer: Single-acting cylinder
A single-acting cylinder applies hydraulic force in one direction only; the return is accomplished by spring tension or gravity.
Question 5: What OSHA standard governs the lockout/tagout of hydraulic energy sources before maintenance?
- 29 CFR 1910.147 (Correct answer)
- 29 CFR 1910.178
- 29 CFR 1926.502
- 29 CFR 1910.303
Correct answer: 29 CFR 1910.147
OSHA 29 CFR 1910.147, the Control of Hazardous Energy standard, requires hydraulic systems to be de-energized and depressurized before maintenance work begins.
Question 6: A solenoid-operated pneumatic valve hums but does not shift. What is the most likely cause?
- Broken return spring
- Spool sticking due to contamination or insufficient voltage to fully shift the spool (Correct answer)
- Blocked exhaust port
- Incorrect pipe size
Correct answer: Spool sticking due to contamination or insufficient voltage to fully shift the spool
Humming indicates the solenoid coil is energized but insufficient voltage or a sticky spool prevents the valve from fully shifting.
Amazon Maintenance Technician Hydraulics & Pneumatics Systems 2
What condition is indicated by milky or cloudy hydraulic fluid?