MEOC Hydraulic Systems & Fluid Management 3

Question 1

Which type of hydraulic pump is most commonly found in mini excavators?

Accepted Answer

Gear pump or variable displacement piston pump, depending on the model and application

Answer

Centrifugal pump, due to its high flow rate at low pressure

Answer

Diaphragm pump, chosen for its contamination resistance

Answer

Vane pump exclusively, due to its quiet operation

Question 2

What is the hydrostatic drive system on a mini excavator?

Accepted Answer

A system where a hydraulic pump delivers pressurized fluid to hydraulic travel motors, replacing mechanical gears

Answer

A propulsion system powered by pressurized water stored on the machine

Answer

A mechanical gearbox lubricated with hydraulic fluid for corrosion protection

Answer

An emergency hydraulic braking system activated when the operator releases the controls

Question 3

What should an operator do when the hydraulic fluid temperature gauge exceeds the normal operating range?

Accepted Answer

Stop work, let the engine idle to allow the cooler to lower temperature, then identify and correct the cause

Answer

Continue working at reduced attachment force until the end of the shift

Answer

Pour cold water over the hydraulic reservoir to reduce temperature immediately

Answer

Increase engine RPM to full throttle to spin the cooling fan faster

Question 4

How do contaminated hydraulic lines typically affect mini excavator performance?

Accepted Answer

They cause restricted flow, reduced power output, accelerated component wear, and potential system failure

Answer

They temporarily improve hydraulic response speed before causing failure

Answer

Contamination only affects fluid chemistry and does not impair machine performance

Answer

They increase maximum bucket breakout force by raising system back-pressure

Question 5

Why is proper torque specification critical when replacing hydraulic fittings on a mini excavator?

Accepted Answer

Under-torquing causes fluid leaks; over-torquing cracks fittings or damages threads, also causing leaks or failures

Answer

Torque is not critical because hydraulic fittings self-seal under operating pressure

Answer

Maximum torque should always be applied to prevent fittings from loosening under vibration

Answer

Torque specifications apply only to metric fittings, not SAE or JIC fittings

Question 6

Why must used hydraulic fluid from a mini excavator be captured and disposed of properly?

Accepted Answer

Used hydraulic fluid is regulated as hazardous waste under EPA rules and must be recycled or disposed of at approved facilities

Answer

Used hydraulic fluid is highly flammable and must be incinerated on-site immediately

Answer

Old hydraulic fluid can be safely repurposed as engine crankcase lubricant after filtering

Answer

Proper disposal is only required in states that have adopted the California Environmental Code

Question 7

What is the correct action when an operator notices that a hydraulic cylinder is slowly drifting (retracting under load) on a mini excavator?

Accepted Answer

Stop operation immediately and have the cylinder seals or holding valve inspected and repaired before resuming work

Answer

Log the drift and monitor it over the next several shifts before scheduling a repair

Answer

Add hydraulic fluid to the reservoir to compensate for the internal bypass

Answer

Increase engine RPM to maintain higher system pressure and counteract the drift