Solenoid coils are the heart of control systems in power hydraulics. They are responsible for switching solenoid valves, and thus for the direction, pressure, and flow of hydraulic oil in the machine. Although it is a relatively small component, its failure usually means one thing: an immediate and costly shutdown of the production line or construction machine.
When a coil burns out, quick replacement is a priority. However, how can you avoid mistakes when choosing a replacement and what parameters should you pay attention to so that the new coil works flawlessly for years?
4 key parameters when choosing a coil
For the new component to work with your directional valve or valve, you need to verify several basic values. You will usually find them engraved or printed on the casing of the old coil.
1. Voltage and current type (V)
This is an absolute basic. Coils operate at different supply voltages. Connecting a 12V coil to a 24V installation will burn it out in a fraction of a second, while a 24V coil in a 12V installation will not generate a strong enough magnetic field to move the valve spool.
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Typical DC (direct current) values: 12V, 24V (most popular in mobile power hydraulics and agricultural machinery).
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Typical AC (alternating current) values: 110V, 230V (common in stationary industrial applications).
2. Internal diameter and length (Mechanical dimensions)
Even if the electrical parameters match, the coil must physically fit onto the valve stem (sleeve). Measure precisely with a caliper:
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The diameter of the inner bore (e.g., 13 mm, 18 mm, 22 mm).
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The total length of the coil, so that the fastening nut can securely catch the thread at the end of the stem.
3. Power (W)
The coil's power directly translates into the force with which the valve core is attracted. In systems with high operating pressure or with thick oil, higher power coils are required to overcome the resistance of the spool. When replacing, the replacement should have power equal to or slightly higher than the original.
4. Type of electrical connection (Plug)
The method of connection to the machine's installation must be compatible to ensure tightness (often IP65/IP67 protection class). The most popular standards include:
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DIN 43650 (EN 175301-803) plugs – type A (wide), type B (narrow),
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AMP Junior Timer – very popular in automotive and mobile machinery,
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Deutsch DT04 – connectors with increased resistance to harsh conditions,
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Loose cables (Flying leads).
Why do hydraulic coils burn out? Problem diagnosis
Simply installing a new coil from the catalog is often treating the symptoms, not the cause. Solenoids most often fail for two reasons:
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Mechanical blockage of the valve spool: If the oil in the system is contaminated, dirt can block the spool. The coil receives a signal and current, tries to move the blocked core, which causes it to immediately overheat and melt the insulation of the copper winding. Before installing a new coil, make sure the valve stem moves freely!
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Continuous operation above parameters (ED): Each coil has a defined duty cycle, the so-called ED factor (usually ED 100%, which means continuous operation is possible). Poor valve cooling or operation in extremely high ambient temperatures drastically shortens its lifespan.
Summary
Choosing a coil does not have to be complicated if you carefully check the voltage, bore dimensions, and plug type. Remember to always diagnose the cause of the old component's failure before installing a new one – this will save you time and money.
In the BRhydraulic.eu store, you will find a wide selection of solenoid coils for the most popular valves and directional valves on the market. If you have any doubts about which model will fit your machine – please contact us. Our technical department will help you quickly choose the right replacement.