How to check the solenoid valve?

The solenoid valve is a key actuator for achieving automated control, widely used to open, close, or switch the flow paths of liquids, gases, or oils. It converts electrical signals into mechanical actions and serves as the bridge between the control system and the actuating device. Regular inspection of solenoid valves is a necessary measure to ensure the system’s safe, efficient, and reliable operation. It helps prevent failures, reduce losses, and extend the overall equipment lifespan while improving production efficiency.

The inspection includes:

◆ Testing whether the valve operates normally
◆ Checking for air leaks or leakage
◆ Inspecting the solenoid coil for damage

◆ Testing if the control signal is properly received
◆ Testing whether the valve core switches sensitively
◆ Checking the valve body for damage or blockage

You need to conduct a detailed inspection of the soleoid valve according to the following testing steps, including appearance and performance.

Visual Inspection

Items to check:

• Whether the housing is damaged or deformed (e.g., due to impact or aging)
• Whether there is contamination from oil, water, or dust
• Whether the coil, connectors, or plugs are loose or detached
• Whether the label and model number are correct (to prevent misuse)

Precautions:
• Housing deformation may cause the coil or valve core to jam
• Loose plugs can cause the coil to lose power connection

Coil Test

Tools:
• Multimeter

Items to check:

1.  Measure resistance with a multimeter

Remove the coil and measure the resistance across its two terminals using the ohm setting

Normal resistance is usually between several tens to several hundred ohms (depending on the model)

Resistance = 0 ➜ short circuit; Resistance = infinity ➜ open circuit (coil is burnt out)

2.  Check if the coil actuates when powered

Listen for a “click” sound after powering the coil

If there is no action, possible causes include a faulty coil, incorrect power supply, or valve core stuck

Precautions:
• Pay attention to voltage rating (24VDC / 110VAC / 220VAC); applying wrong voltage may damage the coil
• Some solenoid valves with a manual test button can be manually operated to check if the valve core is functioning properly.

Electrical Signal

Items to check:
• Whether the voltage output from the controller or PLC is normal
• Whether the plugs and terminals are properly connected
• Whether the correct polarity of the DC power supply is used

Tools:
• Multimeter for voltage measurement
• Oscilloscope can be used to observe pulse control signals

Function Test

Items to check:
• Whether the valve switches the air (or liquid) path after power is applied
• Whether the actuator (e.g., cylinder) operates
• Whether there is delay, sticking, or abnormal noise

Methods:
• Observe whether the valve switches in the powered on/off state
• For pilot-operated valves, ensure the minimum working pressure is maintained
• If the action is sluggish, there may be internal dirt, insufficient lubrication, or wear

Leakage Check

Areas to inspect:
• Connection points (inlet/outlet/exhaust ports)
• Valve body joints
• Internal valve spool seals

Inspection methods:
• Apply soapy water to check for bubbles (gas leakage)
• Observe whether there is continuous exhaust or pressure leakage at the output
• Use a pressure gauge to check for abnormal pressure drop

Precautions:
• Common causes: aging O-rings, worn valve spools, foreign objects stuck on sealing surfaces.

Flow Path Check

Methods:
• Supply air in the powered state to confirm whether gas can pass through the valve smoothly
• Check whether it can fully close in the powered-off state
• Use a flow meter or pressure gauge for testing

Precautions:
• Some solenoid valves have internal filters or throttling orifices, which are prone to clogging by dust or oil residue.

Maintenance

The solenoid valve should be inspected before and during operation, followed by proper maintenance. Refer to the table below for maintenance guidelines.

Spare Parts

• Solenoid Coil 
• Valve Spool Assembly 
• Sealing Rings/O-Rings
• Plugs and Cables
• Springs 

Conclusion

Inspecting a solenoid valve involves comprehensively verifying whether it is energized, switches properly, maintains sealing integrity, and allows unobstructed flow, while systematically troubleshooting any abnormalities by integrating both electrical and pneumatic components. Regular maintenance is critical to ensuring its long-term stable operation.