Hydraulic Valve Operation and Adjustment

Hydraulic Valve Operation and Adjustment

Why Valves Matter

A hydraulic elevator moves by controlling the flow of hydraulic fluid between the power unit and the jack. Every performance characteristic you experience as a passenger—smooth starts, steady travel speed, accurate floor leveling, and gentle stops—is shaped by valves. As a pre-apprentice, your ability to read valve settings, make precise adjustments, and document the results is a core competency that NEIEP/IUEC and NAEC CET evaluators look for.

The Control Valve Assembly

The control valve is the central component that manages fluid flow in both directions. It typically contains several sub-valves working together:

• Up-speed needle valve — restricts fluid flow from the pump to the jack during the up-travel phase, setting how fast the car rises.
• Down-speed (lowering) needle valve — controls fluid returning from the jack to the tank during descent, setting how fast the car lowers.
• Leveling valve — a slower, reduced-flow circuit that creeps the car into precise floor-level position at the end of a run, typically operating at a fraction of full travel speed.
• Pressure-relief valve — a safety device that opens automatically when system pressure exceeds a set maximum, bypassing fluid back to the tank and preventing overload of the jack, pump, and piping.

Each valve is adjusted independently. Small changes have real effects, so adjustments are always made in small increments—usually a quarter-turn or less at a time.

Pressure-Relief Valve Adjustment

The pressure-relief valve protects the entire hydraulic circuit. Its set pressure must be high enough to lift a fully loaded car but low enough to provide meaningful overload protection. The adjustment procedure follows a consistent sequence:

1. Connect a calibrated pressure gauge to the test port on the valve or power unit.

2. Start the pump and allow the system to reach operating temperature.

3. Record the baseline relief pressure while the car is held against the top travel limit (pressure peaks here).

4. Using the correct tool—a slotted screwdriver or hex key depending on the valve manufacturer—turn the relief screw clockwise to increase pressure, counterclockwise to decrease it.

5. Make one small increment, wait for pressure to stabilize, and re-read the gauge.

6. Record before-and-after values in your valve-adjustment log with a timestamp.

Never adjust relief pressure beyond the value specified on the manufacturer's data plate or the authority having jurisdiction (AHJ) approval documents. Exceeding rated pressure can damage seals, piping, and the jack.

Up-Speed and Down-Speed Adjustment

Car speed is verified by measuring travel time over a known distance and calculating the result. The target speed is listed on the lab sheet or the manufacturer's specification sheet. Adjust the appropriate needle valve in small increments, re-run the car, and measure again until the speed is within the acceptable tolerance.

Needle valves are sensitive. A common mistake is over-adjusting—turning too far and having to work back. Discipline yourself to quarter-turns, then test.

Leveling Valve Adjustment

Accurate leveling is essential for accessibility and passenger safety. A car that levels more than a small fraction of an inch above or below the floor sill creates a tripping hazard and may violate ASME A17.1, the Safety Code for Elevators and Escalators. The leveling circuit slows the car as it approaches the floor and stops it at sill level. If the car consistently overshoots or undershoots, the leveling valve flow rate or the position of the leveling sensors may need adjustment.

Manual Emergency Lowering Valve

In a power failure, trapped passengers must be lowered to the nearest landing and evacuated. The manual emergency lowering valve allows controlled release of fluid from the jack back to the tank using gravity alone—no pump power is needed.

Critical safety step: Before operating the manual lowering valve in any training or field scenario, the power unit must be locked out and tagged out (LOTO) in strict accordance with OSHA lockout/tagout requirements. Verify zero energy state before proceeding.

To lower the car, open the manual valve slowly. The car descends under its own weight. Open the valve too far and the car drops too fast; keep movements small and deliberate. When the car reaches the bottom landing, close the valve, open the doors following emergency procedures, and assist passengers. After restoring power, check the fluid level in the tank because the jack cylinder now holds more fluid than it did when the car was elevated.

Safety Points for This Lab

• PPE required: Safety glasses and appropriate footwear whenever the power unit is running or fluid lines are under pressure.
• Pinch and crush hazards: Keep hands clear of the moving car platform and guide rails at all times.
• Hydraulic fluid under pressure: Never loosen fittings or gauges while the system is pressurized. Confirm gauge connections are tight before starting the pump.
• LOTO: Required every time before manually operating the emergency lowering valve or reaching into any area near moving components.
• Spill response: Know the location of absorbent spill materials. Hydraulic fluid on the floor is a slip hazard.
• Documentation: Every reading, adjustment, and result must be recorded immediately—not reconstructed from memory. Accurate logs are both a training standard and a professional habit.

Documentation Standards

Your valve-adjustment log must include the valve name, initial reading or time, adjustment direction and increment, resulting reading or time, timestamp, and your initials. The pass mark for this lab is 80% of data entries accurate, and car speeds must be within ±10% of the target specification.