Hydraulic Systems and Schematics Flashcards
6 cards from real Millwright Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Hydraulic Systems and Schematics flashcards as text
In a hydraulic schematic, what does a spring-centered, three-position, four-way directional control valve default to when de-energized?
Answer: It depends on the center condition shown in the symbol
The center condition of a three-position valve varies by design: it could be open center, closed center, tandem center, or float center, as indicated by the lines drawn in the center box of the schematic symbol.
What is the primary cause of cavitation in a hydraulic pump?
Answer: Restriction or air leak in the pump inlet line causing low suction pressure
Cavitation occurs when the pump inlet pressure drops below the fluid's vapor pressure, causing dissolved gas to form bubbles that collapse violently when compressed, eroding internal pump surfaces.
How does a pressure-compensated variable displacement pump improve hydraulic system efficiency?
Answer: It reduces output flow when system pressure rises, minimizing wasted energy
A pressure-compensated pump automatically reduces its displacement (and therefore flow output) when system pressure approaches the compensator setting, so it only pumps the flow needed, reducing heat generation and energy waste.
What hydraulic fluid property is most critical to monitor for system health?
Answer: Contamination level (particle count and water content)
Contamination, both particulate and water, is the leading cause of hydraulic component failure, making regular fluid analysis the most important monitoring practice for system health.
What is the function of a pilot-operated check valve in a hydraulic circuit?
Answer: To allow reverse flow only when a pilot signal is applied
A pilot-operated check valve allows free flow in one direction like a standard check valve, but can also be opened in the reverse direction by an external pilot pressure signal, enabling controlled load lowering.
When troubleshooting a hydraulic system that has no pressure, what should be checked first?
Answer: The fluid level, pump rotation, and relief valve setting
No system pressure starts with the basics: verify adequate fluid level, confirm the pump is rotating in the correct direction and at proper speed, and check that the relief valve is not stuck open or set to zero.