Hydraulic Systems Flashcards

A double-acting hydraulic cylinder extends slower than it retracts when the same flow rate is applied. Why?

Answer: The piston rod displaces fluid volume on the rod side, reducing effective area

On retraction, the rod-side annular area is smaller than the full bore area, so the same flow produces faster rod movement.

What is the primary function of a hydraulic reservoir beyond storing fluid?

Answer: Allowing heat dissipation and air separation from the fluid

The reservoir allows fluid to cool, release entrained air, and settle contaminants between circuits.

Which valve type automatically maintains a set downstream pressure regardless of flow variations?

Answer: Pressure-reducing valve

A pressure-reducing valve limits downstream pressure to a set maximum, protecting downstream components.

What does a Beta ratio (β) of 200 for a hydraulic filter indicate?

Answer: 200 particles upstream for every 1 that passes downstream at the rated micron size

Beta ratio compares upstream to downstream particle counts at a specific size; β₁₀=200 means 99.5% efficiency at 10 microns.

A technician notices the hydraulic fluid has a milky appearance. What is the most likely cause?

Answer: Water contamination

Water contamination causes hydraulic fluid to turn milky or cloudy as water emulsifies with the oil.

What is the purpose of a counterbalance valve in a vertical cylinder application?

Answer: Prevent uncontrolled descent of a load due to gravity

A counterbalance valve maintains back pressure on the rod side to prevent a suspended load from dropping uncontrollably.

In a hydraulic system, what is 'internal leakage' across a spool valve an indicator of?

Answer: Worn or damaged valve spool and bore clearances

Internal leakage across directional control valve spools increases as clearances wear, reducing actuator speed and efficiency.