CPT CPT Fluid Systems & Hydraulics 1 — Questions and Answers
Question 1: What is the primary function of a check valve in a hydraulic system?
- Allow bidirectional flow
- Allow flow in one direction only (Correct answer)
- Regulate system pressure
- Filter contaminants
Correct answer: Allow flow in one direction only
A check valve permits fluid flow in only one direction, preventing backflow that could damage pumps or cause system malfunction.
Question 2: Which unit is used to express hydraulic pressure in industrial process systems in the US?
- GPM
- PSI (Correct answer)
- RPM
- CFM
Correct answer: PSI
PSI (pounds per square inch) is the standard US unit for measuring hydraulic pressure in industrial systems.
Question 3: What does cavitation in a hydraulic pump indicate?
- Excessive back pressure
- Insufficient fluid supply or trapped air causing vapor bubbles (Correct answer)
- High fluid viscosity
- Filter bypass condition
Correct answer: Insufficient fluid supply or trapped air causing vapor bubbles
Cavitation occurs when the pump inlet is starved of fluid or contains air, forming vapor bubbles that collapse violently and damage pump components.
Question 4: A relief valve in a hydraulic circuit is set to open at 2,000 PSI. What happens when system pressure reaches 2,500 PSI?
- The pump shuts down automatically
- The relief valve opens and diverts fluid back to the reservoir (Correct answer)
- The actuator extends at maximum speed
- A pressure switch triggers an alarm only
Correct answer: The relief valve opens and diverts fluid back to the reservoir
When pressure exceeds the relief valve setpoint, the valve opens and bypasses fluid to the reservoir, protecting the circuit from overpressure damage.
Question 5: Which type of hydraulic pump delivers a fixed volume of fluid per revolution regardless of outlet pressure?
- Variable displacement pump
- Fixed displacement pump (Correct answer)
- Centrifugal pump
- Peristaltic pump
Correct answer: Fixed displacement pump
A fixed displacement pump outputs a constant volume per revolution; output flow changes only with shaft speed, not system pressure.
Question 6: What is the purpose of a hydraulic accumulator in a process system?
- To filter hydraulic oil
- To store pressurized fluid for emergency or supplemental flow (Correct answer)
- To cool hydraulic fluid
- To measure flow rate
Correct answer: To store pressurized fluid for emergency or supplemental flow
An accumulator stores pressurized hydraulic fluid (using gas pre-charge or springs) to supply additional flow during peak demand or maintain pressure during pump shutdown.
CPT CPT Fluid Systems & Hydraulics 1
What is the primary function of a check valve in a hydraulic system?