Troubleshooting Hydraulic Solenoid Valves

Hydraulic solenoid spool valves are a critical component in many industrial machines. These valves help control the directional flow of hydraulic fluid and ensure precise movement via electrical signals. However, when solenoid valves encounter issues, machine performance and productivity can grind to a halt. The two most common issues with solenoid valves fall into two categories—hydraulic and electrical.

Common Hydraulic Issues with Solenoid Valves

1. Oil Condition and Contamination
One frequent cause of hydraulic issues is contamination in the oil or the solenoid valve. Contaminants can originate in the reservoir. It is possibly due to the breakdown of a pump that is beginning to fail, or accidentally dropping metal particles into the tank when filling oil due to dirty environmental conditions, or even a failed machine device. These contaminants will eventually make their way into the solenoid valve when the pump picks them up. This can cause contaminants to lodge into and damage the spool, which shifts when the coils are activated to change the oil path. That movement makes a cylinder move in or out, or a gear motor turn clockwise or counterclockwise.

How to Diagnose Contamination

Inspect the oil reservoir and filter for dirt or particulate buildup.
Check the solenoid valve’s two posts where the coils are located. Each post has a plunger that controls the solenoid spool movement for manual movement. Depress each plunger manually to test for contamination. If a chip is lodged in the spool, it will not move because it is jammed.

2. Causes of Sticking Solenoids

Coils that are on the valve control movement get hot, and when they are bad you will be able to manually move the spool, but when the voltage is sent to the valve, and it does not move, this will indicate a potentially bad coil.

How to Fix Hydraulic Issues
If you’ve identified contamination as the cause of your solenoid issues, follow these steps to resolve the problem:

Drain the Old Oil: Dispose of the used hydraulic oil properly. Should be done annually.
Inspect and Clean the Reservoir: Remove any residual contaminant buildup from the reservoir.
Replace the Oil Filter: This prevents further contaminants from entering the tank from the machine.

Run a System Flush (if necessary): Use a cleaning agent designed for hydraulic systems and allow the machine to run. This process cleans and purges the entire hydraulic circuit to flush out contaminants.

Why Replacing Solenoids is Better Than Cleaning

While some may attempt to clean solenoids to save time or money, this is often a temporary fix. Cleaning instead of replacing can lead to future malfunctions. For a long-term solution, we highly recommend replacing compromised solenoids entirely.

Cross Referencing
When troubleshooting a solenoid valve, it’s crucial to ensure the components you use are of high quality and meet the machine tool manufacturer’s specifications. Valves can be crossed to another manufacturer. What is important is that it is crossed correctly to ensure the operation will function properly. If you have questions, All World’s customer service team can assist.

High-quality components are essential because solenoids in machine tools generally play a critical role. These coils control the solenoid's operation, switching it on and off hundreds of times as the machine operates. Reliability is vital, as the solenoid's performance directly impacts the overall efficiency and operation of the machine.

Using quality components ensures the durability and functionality required for such demanding tasks, helping the machine operate smoothly and maintain its performance standards.

How to Replace Solenoids

Remove the Old Solenoid: Unscrew the electrical connections to the valve. Note which wires were wired to which coil for reassembly. Also, note the way the valve is mounted and mount the new valve the same way. If you look at the casting, or main body of the valve, all valves are marked on one side with a “T” and on the other side with an “A,P,B.” That indicates the port closes to that letter for correct orientation.
Use an Allen key to remove the four mounting screws and detach the solenoid.

Install the New Solenoid: Make sure the T and P lines of the manifold are aligned correctly to the manifold and install the 4 mounting screws.
Reinstall the electrical wiring to the valve, confirming that the correct wires go to the correct coil connection.

Common Electrical Issues with Solenoid Valves

Inspecting the Solenoid Coil: Inspecting the solenoid coil is essential when addressing electrical issues. Here's what to look for:

Visual Inspection: Remove the coil cover cap and check for cracks, discoloration, or other visible damage.
Wire Condition: Look for brittle or cracked coil wires and wires going to the coil terminals. Damaged wires can lead to direct shorts where exposed wires touch and create electrical faults.

Using a Multimeter for Electrical Troubleshooting: to pinpoint electrical issues, use a multimeter to measure the coil resistance and voltage:

Check Coil Resistance: Power off the machine and measure the coil's ohms. Ensure the resistance falls within the specified range for your system. Most valves have two coils, so you can compare one from another, and they should be within a few ohms of each other.
Measure Control Voltage: Turn the machine back on and check the control voltage at the coil. Different solenoids may use varying voltage levels, such as 24V DC or 100V AC. Although 99% of newer machinery have gone towards 24 VDC coils, since most control functions are now 24 VDC.

Repairing or Replacing Damaged Components

Fixing Broken Wires: If the coil wires show visible damage, disconnect the coil and trim or repair the affected portion of the cable.
Replacing Entire Cables: If the damage is extensive, replace the entire cable to ensure reliable performance.

Wrapping it Up
Hydraulic solenoid valves often face two primary issues—hydraulic failures and electrical malfunctions. Common causes include contamination, wire damage, or coil failure. Addressing these problems promptly is key to restoring your system's full functionality.
Feeling unsure about how to troubleshoot or fix these issues? The expert team at All World is ready to assist! Whether you need help selecting the right hydraulic valve replacement (available for same-day shipping) or require a skilled technician to service your machine, we've got you covered. Just give us a call, and we’ll have your machine up and running in no time.