Hydraulic & Pneumatic Systems Flashcards

When troubleshooting a hydraulic system with slow actuator movement, the FIRST parameter to check is:

Answer: System pressure and flow rate

Slow actuator movement indicates either insufficient pressure or inadequate flow; measuring both simultaneously identifies whether the pump, relief valve, or leakage is at fault.

A hydraulic system relief valve that chatters (opens and closes rapidly) most likely indicates:

Answer: System pressure set too close to load-induced pressure

Relief valve chatter occurs when system working pressure fluctuates around the relief setting, causing the valve to cycle rapidly between open and closed.

Hydraulic fluid that appears milky or foamy indicates:

Answer: Both water contamination and aeration are possible causes

Milky fluid suggests water contamination (emulsification), while foamy fluid often indicates aeration — both can produce a similar whitish appearance requiring different remedies.

What is the recommended maximum particle size contamination level (ISO cleanliness code) for servo valve hydraulic circuits?

Answer: ISO 15/13/10

Servo valves have very tight internal clearances (1–5 microns) and typically require ISO 15/13/10 or cleaner fluid to prevent wear and malfunction.

During pneumatic system maintenance, why should energy isolation (lockout/tagout) include bleeding downstream pressure?

Answer: To prevent stored energy release that could cause injury

Stored compressed air downstream of isolation valves can unexpectedly actuate cylinders or expel fittings, so bleeding pressure is required by OSHA 29 CFR 1910.147.

A hydraulic pump that produces excessive heat but normal pressure most likely has:

Answer: High internal leakage causing fluid to recirculate internally

Internal pump leakage causes fluid to slip from high-pressure to low-pressure passages inside the pump, converting hydraulic energy to heat without doing useful work.

The primary function of a hydraulic system case drain line from a motor or pump is to:

Answer: Return internal leakage fluid to the reservoir at low pressure

Case drain lines return bearing lubrication and internal seal leakage back to the reservoir, preventing housing pressure buildup that would damage shaft seals.