SACA Pneumatic and Hydraulic Systems 5

Question 1

A double-acting hydraulic cylinder is not extending fully under load. Which diagnostic check should be performed first?

Accepted Answer

Check system pressure at the cylinder port against the load requirement

Answer

Verifying that system pressure at the cylinder port meets the calculated load requirement is the first diagnostic step to identify whether the issue is pressure, flow, or mechanical.

Question 2

What is the primary advantage of using pneumatics over hydraulics for high-speed, light-load applications in automation?

Accepted Answer

Air is compressible, allowing faster actuator response and simpler exhaust handling

Answer

Compressed air's compressibility and the ability to exhaust directly to atmosphere make pneumatics ideal for high-cycle, fast-response, light-duty automation tasks.

Question 3

In a hydraulic proportional valve system, what is hysteresis and why does it matter for closed-loop control?

Accepted Answer

The difference in output when the same input is approached from increasing versus decreasing directions, affecting positioning accuracy

Answer

Hysteresis is the output difference when a valve is approached from opposite directions, and in closed-loop systems it creates a deadband that limits positioning accuracy and must be compensated in the controller.

Question 4

Which hydraulic circuit configuration is most energy-efficient for a system where multiple actuators rarely operate simultaneously?

Accepted Answer

Closed-center circuit with a pressure-compensated variable-displacement pump

Answer

A closed-center circuit with a pressure-compensated variable-displacement pump reduces flow to near-zero when actuators are idle, minimizing heat generation and energy waste.

Question 5

A pneumatic cylinder fails to hold position when the directional valve is centered. What is the most likely cause?

Accepted Answer

Internal piston seal leakage allowing air to bypass from one chamber to the other

Answer

Internal piston seal leakage allows pressurized air to bypass the piston between chambers, causing the cylinder to drift from its position when the valve is in neutral.

SACA - Smart Automation Certification Alliance Practice Test

SACA - Smart Automation Certification Alliance Practice Test

SACA Pneumatic and Hydraulic Systems 5