433A Hydraulic Systems 3 — Questions and Answers
Question 1: What is the function of a check valve in a hydraulic system?
- To regulate pressure
- To allow flow in one direction only and block flow in the reverse direction (Correct answer)
- To measure flow rate
- To filter the hydraulic fluid
Correct answer: To allow flow in one direction only and block flow in the reverse direction
A check valve is a one-way valve that allows free flow in one direction and automatically closes to prevent flow in the opposite direction. It protects components and maintains pressure in specific parts of the circuit.
Question 2: What is the primary advantage of a piston-type hydraulic pump over a gear-type pump?
- Lower cost
- Higher pressure capability and better efficiency (Correct answer)
- Simpler design
- Does not require a reservoir
Correct answer: Higher pressure capability and better efficiency
Piston pumps can operate at significantly higher pressures (up to 6,000+ PSI) and maintain higher volumetric efficiency than gear pumps, making them suitable for demanding industrial and mobile hydraulic applications.
Question 3: In a hydraulic schematic, what does a diamond symbol typically represent?
- A pump
- A filter or conditioning component (Correct answer)
- A cylinder
- A check valve
Correct answer: A filter or conditioning component
In ISO hydraulic schematics, a diamond (rhombus) shape typically represents a fluid conditioning component such as a filter, strainer, heat exchanger, or separator.
Question 4: What causes hydraulic fluid to overheat?
- Using the correct fluid viscosity
- Excess pressure drop across restrictions, internal leakage, relief valve bypass, or inadequate cooling (Correct answer)
- Operating at the correct flow rate
- Keeping the reservoir full
Correct answer: Excess pressure drop across restrictions, internal leakage, relief valve bypass, or inadequate cooling
Hydraulic fluid overheats when energy is converted to heat faster than it can be dissipated. Common causes include relief valves constantly bypassing, excessive pressure drops across restrictions, internal component leakage, and insufficient cooler capacity.
Question 5: What is the function of a flow divider valve?
- To increase total system flow
- To split a single flow stream into two or more proportional flows regardless of varying load pressures (Correct answer)
- To reduce system pressure
- To combine flows from two pumps
Correct answer: To split a single flow stream into two or more proportional flows regardless of varying load pressures
A flow divider valve splits a single pump flow into two or more equal or proportional output streams. It maintains the flow ratio even when downstream loads have different pressures, ensuring synchronized actuator movement.
Question 6: Why is it important to pre-charge a bladder-type hydraulic accumulator with dry nitrogen?
- Nitrogen increases the fluid pressure
- Nitrogen is an inert gas that provides the gas precharge needed for energy storage without risk of explosion (Correct answer)
- Nitrogen cools the hydraulic fluid
- Nitrogen lubricates the bladder
Correct answer: Nitrogen is an inert gas that provides the gas precharge needed for energy storage without risk of explosion
Dry nitrogen is used for accumulator pre-charging because it is inert (non-combustible), preventing the explosion risk that would exist with compressed air/oxygen in contact with hydraulic fluid under high pressure. The gas precharge stores energy by compression.
433A Hydraulic Systems 3
What is the function of a check valve in a hydraulic system?