A solenoid valve is one of the key components used in many hydraulic lifting systems. It may look like a relatively small component, but it plays an important role in controlling hydraulic oil flow.
In our hydraulic lift systems, solenoid valves are commonly used to control the lowering function of the lift.
How Does a Hydraulic Solenoid Valve Work?
The working principle of a solenoid valve is relatively simple.
When electrical power is supplied to the solenoid coil, the coil generates a magnetic field. This magnetic force moves the internal valve spool and changes the hydraulic oil passage.
When the electrical power is removed, the solenoid is de-energized and the valve returns to its normal position.
A typical sequence is:
24V DC ON → Solenoid energized → Valve spool moves → Oil passage opens
The voltage does not have to be 24V in every application. Different solenoid valves can use different coil voltages, so the coil voltage must always match the electrical control system and the manufacturer's specifications.
How Does the Solenoid Valve Make a Hydraulic Lift Descend?
On many hydraulic lift power units, the solenoid valve controls the hydraulic oil return circuit.
When the lift is holding its position, the corresponding oil passage remains closed.
When the operator presses the DOWN button, the control box sends an electrical signal to the solenoid valve.
The sequence is:
DOWN signal → 24V DC output → Solenoid valve operates → Return passage opens → Hydraulic oil flows back to the tank → Lift descends
Once the hydraulic oil can return to the tank, the platform can descend under the effect of gravity and the load acting on the lifting system.
When the DOWN signal is removed, the solenoid is de-energized and the valve returns to its normal position.
How Is a 24V Solenoid Valve Wired?
A commonly used 24V DC solenoid valve is relatively simple to connect.
The two coil terminals are connected to the corresponding control wires from the electrical control box.
For a solenoid connector with an indicator light, the light provides a useful visual indication of whether the coil is receiving electrical power.
When the DOWN command is activated:
24V ON → Indicator light ON → Solenoid energized
When the DOWN command stops:
24V OFF → Indicator light OFF → Solenoid de-energized
This simple indicator can be very useful during installation and troubleshooting.
What Is the Ground/Earth Terminal?
Some solenoid valve connectors also include a protective earth/ground terminal.
This terminal is different from the two coil terminals. The coil terminals supply power to operate the solenoid, while the protective earth connection is intended for electrical safety.
Whether the protective earth terminal should be connected depends on the specific valve, connector, electrical system, manufacturer instructions, and applicable electrical standards.
Therefore, the manufacturer's wiring diagram and applicable electrical regulations should always be followed.
How to Troubleshoot a Hydraulic Lift That Will Not Descend
If a hydraulic lift does not descend, the solenoid valve is one of the components worth checking.
First, check whether the DOWN command is being received by the control system.
Next, use a multimeter to check whether the expected voltage is being supplied to the solenoid coil when the DOWN command is active.
If the solenoid connector has an indicator light, check whether it turns on.
If there is no indicator light and no voltage, the problem may be related to the control signal, PLC output, relay, wiring, fuse, or power supply.
If the correct voltage is present but the solenoid does not operate, the solenoid coil or valve itself may need to be inspected.
If the solenoid operates normally but the lift still does not descend, the problem may be somewhere else in the hydraulic circuit, such as the valve spool, return passage, hydraulic pressure, or another hydraulic component.
Final Thoughts
A hydraulic solenoid valve is a small component with an important job.
By converting an electrical control signal into mechanical valve movement, it allows the electrical control system to control hydraulic oil flow.
For a typical hydraulic lift:
Electrical signal → Solenoid valve → Hydraulic oil passage → Oil returns to tank → Lift descends
Understanding this basic process makes installation, commissioning, and troubleshooting of hydraulic lifting equipment much easier.
For hydraulic lift manufacturers and users, knowing how to check the solenoid valve, its electrical signal, and the hydraulic circuit can significantly reduce troubleshooting time.
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