Before operation, you must first disconnect the control power supply, close the upstream medium valve, and completely release the residual pressure in the
pipeline. It is strictly forbidden to disassemble the valve body with electricity and under pressure, so as to avoid electric shock or injury caused by medium splashing.
By troubleshooting in the sequence of "from the easy to the difficult, prioritizing electrical checks before mechanical inspections", 90% of power-on non-functional
faults can be quickly identified and resolved.
Step 1: Troubleshoot Power Supply and Control Signals
Use a multimeter to directly measure the actual voltage at the solenoid valve's wiring terminals, confirm that the voltage falls within ±10% of the rated value marked
on the valve nameplate, and do not rely solely on the indicator lights of the control cabinet for judgment.
Check the circuit for broken wires, loose connections, and oxidized terminals, verify that the relay/transistor contacts in the control circuit have no ablation or sticking,
and ensure that the action signals from controllers such as PLCs are output normally.
If the solenoid valve is equipped with a manual test button, press the button after powering off and releasing pressure, and observe whether the spool can act normally
normal action indicates the fault is on the electrical side, while failed action points to mechanical jamming.
Step 2: Inspect the Solenoid Valve Coil
Power off and unplug the coil connector, use the resistance range of the multimeter to measure the resistance across the two ends of the coil: an infinite resistance read
ing indicates an open circuit in the coil, while a resistance value approaching zero indicates a short circuit in the coil. Both conditions require replacing the coil with one
of the exact same specifications.
If the resistance is within the normal range (tens of ohms to thousands of ohms, depending on the model), you can temporarily power on the coil, bring a small
screwdriver close to the metal rod at the center of the coil, and feel if there is obvious magnetic attraction. No magnetic attraction indicates the coil has an inter-turn
short circuit fault.
When installing a new replacement coil, you must ensure that its voltage rating, AC/DC type, and installation dimensions are completely consistent with those of the
original coil. Tighten the terminals after wiring to avoid loose connections.
Step 3: Troubleshoot Mechanical and Flow Path Jamming
Disassemble the valve body, take out the spool, return spring and seals, thoroughly remove impurities such as iron filings, limescale, and oil stains on the spool surface
and inside the valve chamber, scrub them with a clean cleaning agent, then blow dry with compressed air.
Check whether the return spring is deformed, broken or has lost elasticity; replace it directly with a spring of identical specifications if it fails. Inspect seals such as
O-rings and diaphragms for aging or damage, and any scratched seals must be replaced as a complete set.
Clean the pilot throttle orifice and damping orifice of the pilot-operated solenoid valve. These tiny holes are extremely prone to being blocked by dust, which will
prevent the rear air chamber from releasing pressure normally and cause the spool to stop acting completely.
