What component is used to prevent the cylinder from retracting due to load?

What component is used to prevent the cylinder from retracting due to load?

• A. Unlockable check valve
• B. Pilot check valve
• C. Pressure relief valve
• D. Sequence valve

Answer: (A)

Blocking backflow to hold position under load is the key idea. An unlockable check valve acts as a one-way gate: it lets fluid flow to extend the cylinder but prevents it from flowing back to retract when a load tries to push the piston in. This keeps the cylinder in its extended position when the system isn’t actively driving it. You can unlock it to permit retraction when you want motion again, typically by applying a pilot signal. The other options don’t provide this load-holding, backflow-blocking function in the same straightforward way: a pilot check valve needs a pilot pressure to open but doesn’t inherently lock the cylinder against a load; a pressure relief valve protects against overpressure but doesn’t prevent backflow to hold position; a sequence valve controls movement order rather than holding an actuator in place against a load.

Blocking backflow to hold position under load is the key idea. An unlockable check valve acts as a one-way gate: it lets fluid flow to extend the cylinder but prevents it from flowing back to retract when a load tries to push the piston in. This keeps the cylinder in its extended position when the system isn’t actively driving it. You can unlock it to permit retraction when you want motion again, typically by applying a pilot signal.

The other options don’t provide this load-holding, backflow-blocking function in the same straightforward way: a pilot check valve needs a pilot pressure to open but doesn’t inherently lock the cylinder against a load; a pressure relief valve protects against overpressure but doesn’t prevent backflow to hold position; a sequence valve controls movement order rather than holding an actuator in place against a load.