ITMC Hydraulic Systems 3 — Questions and Answers
Question 1: A double-acting hydraulic cylinder extends slower than it retracts when the same flow rate is applied. Why?
- The piston rod displaces fluid volume on the rod side, reducing effective area (Correct answer)
- The cylinder seals are worn on the cap end
- The pump pressure drops during extension
- The return line check valve is partially closed
Correct 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.
Question 2: What is the primary function of a hydraulic reservoir beyond storing fluid?
- Allowing heat dissipation and air separation from the fluid (Correct answer)
- Providing backup pressure during pump failure
- Filtering particulates above 10 microns
- Regulating fluid viscosity automatically
Correct answer: Allowing heat dissipation and air separation from the fluid
The reservoir allows fluid to cool, release entrained air, and settle contaminants between circuits.
Question 3: Which valve type automatically maintains a set downstream pressure regardless of flow variations?
- Pressure-reducing valve (Correct answer)
- Pressure relief valve
- Check valve
- Counterbalance valve
Correct answer: Pressure-reducing valve
A pressure-reducing valve limits downstream pressure to a set maximum, protecting downstream components.
Question 4: What does a Beta ratio (β) of 200 for a hydraulic filter indicate?
- 200 particles upstream for every 1 that passes downstream at the rated micron size (Correct answer)
- The filter captures 200 micron particles
- The filter has a 200 PSI pressure drop rating
- The filter holds 200 cubic inches of contaminant
Correct 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.
Question 5: A technician notices the hydraulic fluid has a milky appearance. What is the most likely cause?
- Water contamination (Correct answer)
- Air entrainment only
- Excessive heat degradation
- Mixing of two different fluid types
Correct answer: Water contamination
Water contamination causes hydraulic fluid to turn milky or cloudy as water emulsifies with the oil.
Question 6: What is the purpose of a counterbalance valve in a vertical cylinder application?
- Prevent uncontrolled descent of a load due to gravity (Correct answer)
- Increase lifting force of the cylinder
- Reduce pump pressure during extension
- Allow free-flow in both directions
Correct 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.
Question 7: In a hydraulic system, what is 'internal leakage' across a spool valve an indicator of?
- Worn or damaged valve spool and bore clearances (Correct answer)
- Excessive pump output pressure
- Blocked tank return line
- Incorrect fluid viscosity causing cavitation
Correct 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.
ITMC Hydraulic Systems 3
A double-acting hydraulic cylinder extends slower than it retracts when the same flow rate is applied.
Why?