EVT EVT Hydraulic Systems & Aerial Apparatus

Question 1

What is the primary function of a hydraulic relief valve in an aerial apparatus system?

Accepted Answer

To prevent system overpressure by diverting excess fluid

Answer

A hydraulic relief valve protects the system by diverting excess fluid back to the reservoir when pressure exceeds a set limit.

Question 2

Which type of hydraulic pump is most commonly used in aerial ladder apparatus due to its ability to deliver constant flow?

Accepted Answer

Piston pump

Answer

Piston pumps are preferred in aerial apparatus because they provide high-pressure, constant-flow output needed for reliable aerial operations.

Question 3

According to NFPA 1901, aerial devices must be tested at what percentage above their rated working load?

Accepted Answer

150%

Answer

NFPA 1901 requires aerial devices to be proof-tested at 150% of their rated working load during annual certification.

Question 4

What condition is indicated when a hydraulic cylinder drifts under load with no control input?

Accepted Answer

Internal cylinder seal leakage

Answer

Cylinder drift under load indicates internal seal leakage, allowing fluid to bypass the piston and causing unintended movement.

Question 5

What is the purpose of a hydraulic accumulator on an aerial apparatus?

Accepted Answer

Store pressurized fluid for emergency operations

Answer

A hydraulic accumulator stores pressurized fluid to provide emergency power for retracting the aerial if the primary pump fails.

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