A solenoid, direct-acting, three-position, spring-centered, directional control valve is used in a hydraulic system to control a linear actuator. With the actuator under load there is no movement. However, when the load is removed the actuator can be cycled in both directions, although slower than normal. Which of the statements listed is the probable cause?
• Behavior of a spring-centered, three-position directional control valve in neutral and actuated positions • Effect of pump speed and output flow on actuator movement under load vs no load • Symptoms of open solenoid coil vs mechanical damage to pump coupling
• Ask what condition would allow the actuator to move in both directions with NO load, but not move at all when the normal load is applied. • Consider which fault would affect overall flow and pressure to the entire system, not just one direction or solenoid. • Think about what happens to actuator speed if the pump cannot reach its rated speed. How would that show up in the operation you see described?
• Compare which options would prevent any movement regardless of load, versus those that mainly reduce available power/flow. • For each choice, decide: would this fault likely affect both directions of travel equally, as described? • Verify which component—valve, solenoids, or pump coupling—could cause the actuator to work only when the load is removed and to move more slowly than normal.
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