Analysis of Common Faults in Electromagnetic Directional Valves and Solenoid Valves!

There are many varieties of electromagnetic reversing valves, which can be categorized based on the number of working positions and channels, such as two-way, three-way, and four-way types. They can also be classified by the return and positioning mechanism, including spring-return, steel-ball positioning, and non-return spring types. Furthermore, electromagnetic valves differ by the connection form between the valve body and the electromagnet, such as flange connection or thread connection. The distribution magnets come in dry and wet types, and these valves can be powered by AC or DC with various required power supply voltages, leading to significant structural differences.

Electromagnetic Directional Valve:
The electromagnetic directional valve uses an electromagnet to control the on/off function, pushing the valve core to control the oil port connectivity.

In the normal operation of electromagnetic directional valves, wear and tear can lead to failure. When wear reaches a certain extent, the valve will cease functioning. This article discusses the common faults and solutions for electromagnetic directional valves.

1. Electromagnet Damage (Burnout)

Electromagnet burnout is a common failure in electromagnetic directional valves. One of the main causes is poor quality, such as improper processing of the iron core or using wire with a diameter too small, which makes it prone to overheating. Failures due to quality issues usually become evident within hours after the electromagnetic reversing valve is powered on. For coils that fail after extended use, environmental factors are usually to blame.

2. Fatigued or Broken Reset Spring

This failure is related to the material used for the spring. Electromagnetic directional valves often use harmonica-style steel wire springs with good elasticity and fatigue resistance. Surface treatment processes enhance the springs' corrosion resistance and extend their service life. When this type of failure occurs, both springs must be replaced simultaneously, and their length should match the design specifications of the electromagnetic reversing valve.

3. Spool Outer Diameter Wear

This is similar to the wear of the bore in the valve body. Oil with large impurities can exacerbate the wear of the solenoid valve spool. While it is impossible to completely avoid such wear, regular checks on the cleanliness of hydraulic oil are essential to prolong the solenoid directional valve's life. If excessive pollution is found, it should be addressed promptly. The three-wing solenoid directional valve spool uses a unique material with hardness reaching HRC60 or higher, providing better wear resistance compared to standard spools.

4. Valve Body Inner Hole Wear

The repeated movement of the spool within the valve body hole, even though the spool design includes an oil groove to reduce friction, inevitably leads to wear. While this wear can't be fully avoided, the valve body material—ductile iron—helps delay wear and deformation. Replacing or repairing worn valve body holes is necessary. When replacing, it's essential to ensure compatibility between the new valve body and other components like electromagnetic tubes and sealing rings.

5. Wear of the Electromagnetic Tube Push Rod

The push rod inside the solenoid tube is responsible for moving the valve core when the armature is activated. Since the push rod and spool are separate, wear is inevitable with constant contact. High-frequency switching can cause the push rod to shorten, affecting the valve core's movement. Replacing the push rod with one of the same size will resolve the issue.

6. Other Uncommon Issues

Besides the common faults mentioned above, there are also rare issues like voltage or current instability, or significant impact fluctuations, which can lead to burnout. In such cases, the solenoid valve core may become stuck, preventing the armature from moving, which can cause the coil temperature to rise sharply, potentially burning the coil. In maintenance, always check for spool blockages before replacing the coil. Ensure the new coil matches the original product’s specifications in diameter and length.

Troubleshooting Solenoid Valve Failure

Solenoid valve failure can directly impact the switching and regulating valve operations. Common faults include the solenoid valve not operating. Troubleshooting should consider the following:

1. Loose Connector or Wire Disconnection: If the solenoid valve isn't receiving power, check the wire connector and tighten it.
2. Burnt Solenoid Coil: Remove the solenoid valve wiring and measure with a multimeter. If the coil is open, the coil has burned out. This could be due to moisture causing poor insulation, magnetic leakage, or excessive current. To prevent such failures, keep the solenoid valve dry. Overly strong springs, insufficient coil turns, and inadequate suction can also lead to coil burnout.
3. Stuck Solenoid Valve: The solenoid valve sleeve and spool have a small gap, typically less than 0.008mm. Mechanical impurities or insufficient oil can cause the valve to stick. A temporary fix is to use steel wire to spring it back. The fundamental solution is to remove the solenoid valve, clean the spool and sleeve with CCI4, and reassemble them correctly.
4. Air Leakage: Air leakage can reduce air pressure, making it difficult to open or close the valve. This is typically caused by damaged sealing gaskets or worn slide valves. When addressing solenoid valve issues in the switching system, perform maintenance during a switching gap, if possible.