CPO CPO Hydraulic Systems & Controls 2 — Questions and Answers
Question 1: What type of hydraulic fluid is most commonly specified for concrete pump systems?
- Motor oil SAE 30
- Anti-wear hydraulic oil (AW-46) (Correct answer)
- Brake fluid DOT 4
- Gear oil GL-5
Correct answer: Anti-wear hydraulic oil (AW-46)
AW-46 anti-wear hydraulic oil is the most common specification for concrete pump hydraulic systems due to its viscosity and additive package.
Question 2: A sudden loss of boom movement during operation most likely indicates:
- Engine overspeed
- Hydraulic pump failure or loss of hydraulic pressure (Correct answer)
- Excessive concrete weight in the hopper
- Outrigger float failure
Correct answer: Hydraulic pump failure or loss of hydraulic pressure
Sudden loss of boom movement typically points to hydraulic pump failure, a burst hose, or a rapid pressure drop in the system.
Question 3: What is the function of a hydraulic accumulator on a concrete pump?
- To store and release hydraulic energy to dampen pressure spikes (Correct answer)
- To clean hydraulic fluid
- To generate additional engine torque
- To control outrigger extension speed
Correct answer: To store and release hydraulic energy to dampen pressure spikes
A hydraulic accumulator stores pressurized fluid and releases it to smooth out pressure fluctuations and assist during peak demand.
Question 4: What should an operator do immediately upon noticing a hydraulic hose leak under pressure?
- Continue pumping and flag the leak for later repair
- Shut down the pump and depressurize the system before inspection (Correct answer)
- Apply tape to the hose while the system is running
- Increase engine RPM to compensate for pressure loss
Correct answer: Shut down the pump and depressurize the system before inspection
A pressurized hydraulic leak is extremely dangerous; the operator must immediately shut down and depressurize before any inspection.
Question 5: Which hydraulic system component filters contaminants from the fluid?
- Hydraulic accumulator
- Flow divider
- Hydraulic filter/strainer (Correct answer)
- Directional control valve
Correct answer: Hydraulic filter/strainer
Hydraulic filters and strainers remove particulate contamination from the fluid, protecting pumps, valves, and cylinders from wear.
Question 6: What does a directional control valve do in a concrete pump's hydraulic circuit?
- Regulates the maximum system pressure
- Routes pressurized fluid to the correct actuator to control movement direction (Correct answer)
- Converts hydraulic pressure back to mechanical energy
- Measures the flow rate of hydraulic fluid
Correct answer: Routes pressurized fluid to the correct actuator to control movement direction
Directional control valves direct hydraulic fluid to the appropriate cylinder or motor to produce the desired movement.
CPO CPO Hydraulic Systems & Controls 2
What type of hydraulic fluid is most commonly specified for concrete pump systems?