Hydraulic Systems & Fluid Management Flashcards

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

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

Mini excavators typically use gear pumps for cost-effective simplicity or variable displacement piston pumps for greater efficiency and flow control.

What is the hydrostatic drive system on a mini excavator?

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

Hydrostatic drive eliminates mechanical gear trains by using a variable-displacement pump and hydraulic motors to provide infinitely variable, smooth track speed in both directions.

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

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

Idling allows the oil cooler to reduce fluid temperature without adding further heat from work; the root cause must be found before resuming normal operation.

How do contaminated hydraulic lines typically affect mini excavator performance?

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

Contaminants restrict orifices, abrade precision pump and valve surfaces, reduce efficiency, and can cause catastrophic failure of hydraulic components.

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

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

Hydraulic fittings must be torqued to spec because both under- and over-torquing destroy the seal interface, creating high-pressure fluid leaks.

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

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

Used hydraulic fluid contains heavy metals and additives that make it a regulated hazardous waste; EPA regulations require collection and recycling or disposal at licensed facilities.

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

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

Cylinder drift indicates failed internal seals or a malfunctioning counterbalance/holding valve, creating an uncontrolled movement hazard that requires repair before further operation.