The most basic load-lock circuit uses a single ____________ in one of the cylinder lines to resist the movement of the cylinder by the load.

The most basic load-lock circuit uses a single ____________ in one of the cylinder lines to resist the movement of the cylinder by the load.

• A. Needle valve
• B. Flow control valve
• C. DCV
• D. POC

Answer: (D)

A load-lock function relies on preventing fluid from flowing back from the cylinder when the drive pressure is removed, so the load cannot push the piston and move the cylinder. A pilot-operated check valve in one line does exactly that: it acts as a one-way barrier that blocks backflow under load, effectively locking the cylinder in place. The pilot signal keeps the check valve closed to hold the position, and only when you apply pilot pressure to release it can movement occur. This single device provides a simple, robust hold without needing additional valves or complicated circuitry. A needle valve or a standard flow-control valve would only throttle the flow, not truly lock the cylinder against the load—there will still be leakage paths that can allow movement. A directional control valve (DCV) introduces extra paths and complexity, which isn’t needed for the basic lock function.

A load-lock function relies on preventing fluid from flowing back from the cylinder when the drive pressure is removed, so the load cannot push the piston and move the cylinder. A pilot-operated check valve in one line does exactly that: it acts as a one-way barrier that blocks backflow under load, effectively locking the cylinder in place. The pilot signal keeps the check valve closed to hold the position, and only when you apply pilot pressure to release it can movement occur. This single device provides a simple, robust hold without needing additional valves or complicated circuitry.

A needle valve or a standard flow-control valve would only throttle the flow, not truly lock the cylinder against the load—there will still be leakage paths that can allow movement. A directional control valve (DCV) introduces extra paths and complexity, which isn’t needed for the basic lock function.