Hydraulic Systems Flashcards

What ISO cleanliness code reading of 18/16/13 means in a hydraulic system?

Answer: Particle count levels per milliliter at 4, 6, and 14 micron size ranges

Each ISO 4406 number represents a range of particle counts per milliliter at 4µm, 6µm, and 14µm respectively.

A hydraulic motor stalls under load even though system pressure is adequate. What is the most likely cause?

Answer: Excessive internal leakage within the motor

Worn motor components allow internal bypass of fluid, reducing torque output even when supply pressure is sufficient.

Which hydraulic fitting connection type is least prone to leakage under high-pressure pulsating conditions?

Answer: O-ring face seal (ORFS)

ORFS fittings use an elastomeric O-ring on a flat face, providing a positive seal unaffected by pressure pulses.

What does the term 'pump volumetric efficiency' measure?

Answer: Actual flow output compared to theoretical flow based on displacement and speed

Volumetric efficiency accounts for internal pump leakage; a new pump may be 95%+ efficient while a worn pump drops significantly.

When troubleshooting a hydraulic system with no actuator movement, which component should typically be checked first?

Answer: Fluid level and pump output

Confirm the pump is producing flow and pressure before suspecting downstream components in a no-movement diagnosis.

What is the effect of increasing hydraulic fluid viscosity beyond the recommended range in cold weather?

Answer: Increased pressure drop, sluggish operation, and possible pump cavitation

Excessively viscous fluid resists flow, causing high pressure drops in lines, slow actuation, and pump starvation.

A proportional hydraulic valve differs from a standard directional control valve in that it:

Answer: Provides variable flow and direction control proportional to an electrical input signal

Proportional valves use a variable-force solenoid to position the spool proportionally, enabling precise speed and direction control.