EVT EVT Hydraulic Systems & Aerial Apparatus 2 — Questions and Answers
Question 1: When inspecting aerial apparatus outriggers, what must be verified before extending the aerial device?
- Engine oil level
- Outriggers are fully deployed and pads on solid ground (Correct answer)
- Hydraulic fluid color
- Tire pressure on all axles
Correct answer: Outriggers are fully deployed and pads on solid ground
Outriggers must be fully deployed and support pads placed on solid, level ground to provide the required stability before aerial operations.
Question 2: Which hydraulic fluid property is most critical for proper operation of aerial apparatus in cold climates?
- Color
- Viscosity index (Correct answer)
- Flash point
- pH level
Correct answer: Viscosity index
Viscosity index indicates how much a fluid's viscosity changes with temperature, which is critical for consistent performance in cold climates.
Question 3: What is the correct procedure when aerial apparatus hydraulic fluid appears milky or foamy?
- Continue operation and monitor
- Change fluid and inspect for water contamination source (Correct answer)
- Add more hydraulic fluid
- Increase system pressure
Correct answer: Change fluid and inspect for water contamination source
Milky or foamy hydraulic fluid indicates water contamination, requiring immediate fluid replacement and identification of the water source.
Question 4: During an aerial ladder annual service test, how long must the aerial withstand the rated load test without retraction or lowering?
- 1 minute
- 2 minutes
- 5 minutes (Correct answer)
- 10 minutes
Correct answer: 5 minutes
NFPA 1901 requires aerial devices to hold the rated load at the worst-case position for 5 minutes without measurable drift or lowering.
Question 5: What type of hydraulic fitting is preferred for aerial apparatus high-pressure lines due to its leak-free performance?
- NPT pipe thread
- SAE O-ring face seal (ORFS) (Correct answer)
- Compression fitting
- Barb fitting
Correct answer: SAE O-ring face seal (ORFS)
SAE O-ring face seal (ORFS) fittings are preferred for high-pressure hydraulic lines because the O-ring provides a reliable, leak-free metal-to-metal seal.
Question 6: What is the recommended method for bleeding air from an aerial apparatus hydraulic system after a component replacement?
- Run the engine at high RPM for 30 minutes
- Cycle the hydraulic actuators slowly through full range multiple times (Correct answer)
- Add a bleed screw to each cylinder
- Replace all hydraulic fluid immediately
Correct answer: Cycle the hydraulic actuators slowly through full range multiple times
Slowly cycling hydraulic actuators through their full range of motion multiple times forces air bubbles to migrate back to the reservoir where they can escape.
EVT EVT Hydraulic Systems & Aerial Apparatus 2
When inspecting aerial apparatus outriggers, what must be verified before extending the aerial device?