What Is Solenoid Valve? (Common Faults and Solutions)

The rated voltage of solenoid valve coil is DC12V, DC24V, AC24V (50/60 Hz), AC110V (50/60 Hz), AC220V (50/60 Hz), AC380V (50/60 Hz).

Generally, AC220V is used in the electrical design because it does not need switching power supply, with low cost, simple circuit and easy maintenance; or DC24V is used because of its commonly used safety voltage and the switching power supply/solenoid valve coil are easy to repair and replace.

What Is Solenoid Valve

1. The method of testing the quality of the solenoid valve

First, the solenoid valve is connected with the controlled medium (liquid with pressure, gas such as air, the pressure value is the middle value of the pressure range of the solenoid valve), then the solenoid coil is energized.

If the controlled medium changes from on to off or from off to on, the solenoid valve is good, otherwise there is a problem.

2. Common faults of the solenoid valve

2.1 Short circuit or circuit break of coil

Detection method:

A multimeter first used to measure its on-off, if the resistance tends to zero or infinity, it means that the coil is short circuit or circuit break.

If the measured resistance is normal (about tens of Ω), it does not mean that the coil must be good (I once measured that the resistance of a solenoid valve coil is about 50 Ω, but the solenoid valve can not act, and everything is normal after replacing the coil), please carry out the following final test.

Find a small screwdriver and put it near the metal rod in the solenoid valve coil, and then power on the solenoid valve.

If it feels magnetic, then the solenoid valve coil is good, otherwise it is broken.

Solution: replace the solenoid valve coil.

2.2 Problems of the plug/socket

Fault phenomenon:

If the solenoid valve has a plug/socket, there may be problems with the metal spring of the socket, the wiring of the plug (for example, the power line is connected to the ground wire), so the power can not be sent to the coil.

It is better to form a habit: After the plug is inserted into the socket, screw on the fixing screw, and after the valve core rod, screw on the fixing nut on the coil.

If the plug of the solenoid valve coil is equipped with LED power indicator, the DC power supply should be used to drive the solenoid valve, otherwise the indicator will not be on.

In addition, the power plugs with LED power indication of different voltage levels can not be replaced, because it will cause that the LED is burnt out/the power supply (replace the low voltage plug) is short-circuited or the LED light is very weak (replace the high voltage plug).

If there is no power indicator, the solenoid valve coil does not need to distinguish the polarity (unlike the transistor time relay with DC coil voltage and the intermediate relay with DC coil voltage of diode/resistor leakage circuit in parallel on the coil <this kind of intermediate relay is mainly from Japan>, which needs to distinguish the polarity).

Solution: correct wiring error, repair or replace plug and socket.

2.3 Problems of the valve core

Fault phenomenon 1:

When the medium pressure of the solenoid valve is normal, pressing the red manual button of the solenoid valve, if the solenoid valve has no response (the pressure medium has no change of on-off), the valve core must be broken.

Solution: check whether there are problems in the medium, such as whether there is a lot of water in the compressed air (sometimes the oil-water separator does not play a very important role, there will be plenty of water in the compressed air to the solenoid valve when the pipeline design is poor), and whether there are many impurities in the liquid medium.

Then remove the water or impurities in the solenoid valve and pipeline.

If not, please repair or replace the valve core, or simply replace the entire solenoid valve.

Fault phenomenon 2:

After inspection, the coil is the original coil, and the magnetism of the coil is normal when it is powered on, but the solenoid valve still does not act (at this time, the function of the manual button of the solenoid valve may be normal), indicating that the valve core is broken.

Solution: repair or replace the valve core, or simply replace the entire solenoid valve.

But for the maintenance of solenoid valve body, there are too many kinds of maintenance methods, so here it is just ignored.

3. Troubleshooting of solenoid valve

3.1 The solenoid valve does not work when it is energized

  • Check whether the power wiring is bad → rewire and connect the connector
  • Check whether the power supply voltage is in ± working range → adjust to normal position range
  • Is the coil desoldered → rewelded
  • Coil short circuit → replace coil
  • Whether the working pressure difference is not appropriate → adjust the pressure difference → replace the corresponding solenoid valve
  • Fluid temperature is too high → replace appropriate solenoid valve
  • Impurities make the main valve core and moving iron core of the solenoid valve stuck → clean, and 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 service life is up → replace the product

3.2 The solenoid valve cannot be closed

  • The seal of the main valve core or iron moving core is damaged → replace the seal
  • Whether the fluid temperature and viscosity are too high → Replace the corresponding solenoid valve
  • Impurities enter the valve core or moving iron core of solenoid valve → cleaning
  • The life of spring has reached or deformed → replace
  • Throttle balance hole blocked → cleaning in time
  • Working frequency is too high or the service life has reached → change the product or update the product

3.3 Other circumstances

  • Internal leakage → check whether the seal is damaged and whether the spring is poorly assembled
  • External leakage → loose joint or damaged seal → tighten the screw or replace the seal
  • There is noise when power is on → the fastener on the head is loose and tightened.
  • If the voltage fluctuation is not within the allowable range, the voltage needs to be adjusted.
  • If the iron core suction surface has impurities or is uneven, it should timely be cleaned or replaced.

4. Quick judgment method of solenoid valve on site

4.1 First, check whether the solenoid coil of the solenoid valve is faulty.

On the DCS, an on or off signal on the two-position valve is given.

Then check whether the solenoid valve is powered on or off.

Generally, listening to the sound on site is fine.

If not, there must be something wrong with the coil.

If there is something wrong with the solenoid valve itself, the explanation is given as followed.

If there is a problem with the solenoid, first check the wiring.

Then check whether there is virtual connection or short circuit.

If there is no problem with the circuit, the solenoid valve coil is burnt out.

Remove the wiring of the solenoid valve and measure it with a multimeter.

If there is an open circuit, the solenoid valve coil is burnt out.

The reason is that the coil is damp that causes poor insulation and magnetic leakage, causing excessive current in the coil and burning, so it is necessary to prevent rainwater from entering the solenoid valve.

In addition, when the spring is too hard, the reaction force is too large, the coil turns are too few, if the suction force is not enough, the coil can be burned.

4.2 If the hot wire coil is good, the solenoid valve itself has problems.

Generally, it can be adjusted 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 coil problem, and changing the coil can solve.

If it cannot be opened, remove the solenoid valve to see if the valve core is stuck or there is debris blockage.

CCL4 should be used for correct cleaning.

However, if there is not any equipment on site, gasoline or water can be used.

After cleaning, the field instrument can be blown dry with gas.

When dismantling, the sequence of each part must be remembered.

If do not pay attention, it is easy to make mistakes when installing.

If the sequence is wrong, it can not be opened after cleaning or turning on the solenoid valve!

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