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Common Faults And Solutions Of Solenoid Valves

The rated voltages of solenoid valve coils are DC12V, DC24V, AC24V (50/60Hz), AC110V (50/60Hz), AC220V (50/60Hz), AC380V (50/60Hz). Generally in electrical design, either AC220V (no switching power supply required, low cost, simple wiring and easy to maintain), or DC24V (commonly used safety voltage, switching power supply/solenoid valve coils are easy to repair and replace).
The method to detect the quality of the solenoid valve: first pass the controlled medium (pressured liquid, gas , the pressure value is the middle value of the pressure range of the solenoid valve) to the solenoid valve, and then energize the solenoid valve coil. If the controlled medium changes from on to off or from off to on, then the solenoid valve is good, otherwise there is a problem.

Common faults of solenoid valves are

1. The coil is short-circuited or disconnected:
Detection method: first use a multimeter to measure its continuity, and the resistance value is close to zero or infinity, that means the coil is short-circuited or disconnected. If the resistance measured is normal (about tens of ohms), it still does not mean that the coil must be good (I once measured a solenoid valve coil with a resistance of about 50 ohms, but the solenoid valve could not work. After replacing the coil, everything is normal. ), please carry out the following final test: find a small screwdriver and place it near the metal rod that penetrates the solenoid valve coil, and then energize the solenoid valve. If magnetism is felt, then the solenoid valve coil is good, otherwise it is bad .
Solution: Replace the solenoid valve coil.
2. There is a problem with the plug/socket:
Trouble phenomenon:
If the solenoid valve has a plug/socket, there may be problems with the metal reed of the socket (the author has encountered it), wiring problems on the plug (such as connecting the power cord to the grounding wire) and other reasons. The power is sent to the coil. It is best to develop a habit: screw the fixing screw on after the plug is inserted into the socket, and screw the fixing nut on the coil after the valve core rod.
If the plug of the solenoid valve coil is equipped with a light-emitting diode power indicator, then it must be connected when the solenoid valve is driven by a DC power supply, otherwise the indicator will not light up. In addition, do not exchange the power plugs with LED power indications of different voltage levels. This will cause the LEDs to be burned/the power supply (replace the plug with a low voltage level) to short-circuit or the light-emitting diodes are very weak (switch to use High-voltage plug).
If there is no power indicator light, the solenoid valve coil does not need to distinguish the polarity (unlike the transistor time relay whose coil voltage is DC and the intermediate relay whose coil voltage is DC with a diode/resistor leakage loop connected in parallel. Most of the original small Japan>, need to distinguish the polarity).
Treatment method: correct wiring errors, repair or replace plugs and sockets.
3. Spool problem:
Trouble phenomenon 1: When the pressure of the medium through the solenoid valve is normal, press the red manual button of the solenoid valve, and the solenoid valve has no response (the pressure medium does not change on and off), indicating that the spool must be broken.
Solution: Check whether there is a problem with the medium, such as whether there is a lot of water in the compressed air (sometimes the oil-water separator does not play a big role, especially when the pipeline design is poor, the compressed air to the solenoid valve will have a lot of accumulation. Water), whether there are many impurities in the liquid medium. Then remove the water or impurities in the solenoid valve and pipeline. If it doesn’t work anymore, please repair it.
Fault phenomenon 2: After inspection, the coil is the original coil and the magnetism is normal when the coil is energized, but the solenoid valve still does not operate (the function of the solenoid valve manual button may be normal at this time), indicating that the spool is broken.
Solution: Please repair or replace the valve core, or simply replace the entire solenoid valve.
As for the maintenance of the solenoid valve body, because there are too many types, I can’t say a lot about the various maintenance methods, so I won’t repeat them here.

Solenoid valve troubleshooting and troubleshooting

1. The solenoid valve does not work after it is energized
Check whether the power wiring is bad → rewire and connect the connector
Check whether the power supply voltage is within the ± working range-→ adjust to the normal position range
Whether the coil is unsoldered → re-soldered
Coil short circuit → replace the coil
Whether the working pressure difference is not appropriate → adjust the pressure difference → or replace the commensurate solenoid valve
The fluid temperature is too high → replace the commensurate solenoid valve
Impurities cause the main valve core and moving iron core of the solenoid valve to jam → clean, if the seal is damaged, replace the seal and install the filter
The viscosity of the liquid is too high, the frequency is too high, and the life is reached → replace the product
2. The solenoid valve cannot be closed
The seal of the main spool or the iron core is damaged → replace the seal
Whether the fluid temperature and viscosity are too high → replace the solenoid valve of the corresponding port
Impurities enter the valve core or moving iron core produced by the solenoid valve → clean
The life of the spring is reached or deformed → replace
Orifice balance hole is blocked → clean in time
The working frequency is too high or the service life has come → change the product or update the product
3. Other situations
Internal leakage → check whether the seal is damaged, whether the spring is poorly assembled
External leakage → loose connection or bad seal → tighten the screw or replace the seal
There is noise when energized → The solid parts on the head are loose, tighten them. If the voltage fluctuation is not within the allowable range, adjust the voltage. If there is impurities or unevenness on the suction surface of the iron core, clean or replace in time.

How to quickly judge the quality of solenoid valves on site

1. Check if the solenoid coil of the solenoid valve is faulty?
Give the two-position valve an open or close signal on the DCS, and then see if the solenoid valve is gaining or losing power. Generally, just listen to the sound on site.
If you can’t hear it, there must be a problem with the coil. As for the solenoid valve itself, is there a problem? (explained below)
If there is a problem with the solenoid coil, first check the wiring to see if there is a virtual connection or a short circuit. If there is no problem on the wiring, the solenoid valve coil is burned out. You can remove the solenoid valve wiring and measure with a multimeter. If it is open, the solenoid The valve coil is burnt out. The reason is that the coil is damp, causing poor insulation and magnetic leakage, causing excessive current in the coil and burning. Therefore, it is necessary to prevent rainwater from entering the solenoid valve. In addition, if the spring is too hard, the reaction force is too large, the number of turns of the coil is too few, and the suction force is not enough to cause the coil to burn out.
2. If the coil is good, it is the problem of the solenoid valve itself.
Generally, you can adjust the valve from 1 to 0 in the manual adjustment position to open the valve. If it can be opened, it means that it is indeed a problem with the coil. You can change the coil. If it does not open, remove the solenoid valve. It is not that the spool is stuck or there is clogged particles. CCL4 should be used for correct cleaning. However, considering that there are no conditions on the site, gasoline can be used. It is also possible without water. After cleaning, you can use on-site instrument air to blow dry. Be sure to remember the order of the components. If you don’t pay attention, it is easy to make mistakes when installing. If you remember the order incorrectly, even if you clean the solenoid valve, it will not open even if the solenoid valve is already open!

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