For hydraulic systems or hydraulic equipment, hydraulic solenoids are the basic components that generate forces that pull the spool to control the direction, pressure and flow of hydraulic fluid. Hydraulic solenoids, also known as solenoid valves for hydraulic valves.


In the hydraulic control system, the hydraulic solenoid is the connection between the front and the back. The main function of the hydraulic solenoid valve is to convert electrical energy into mechanical energy to drive the action of the hydraulic valve. To be precise, the hydraulic solenoid consists of two parts, an electromagnetic coil and an armature moving element. In the hydraulic solenoid valve market, these two components are sold as a full set. One of the common sources of damage in real engineering machinery maintenance practices is the burning of the solenoid. Therefore, in the following, we will focus on the maintenance of hydraulic solenoids.


NACHI Hydraulic Solenoid Basic

Common types of hydraulic solenoid valves are switch solenoid valves and proportional solenoid valves. Switch solenoid valves are typically mounted on hydraulic directional valves to control the direction shifting of hydraulic valves and the unloading and uploading of hydraulic systems. Proportional solenoid valves are typically installed on a type of hydraulic proportional valve to control the direction, pressure and flow of hydraulic fluid. In addition, a large number of hydraulic proportional pressure valves are installed on the electric variable displacement pump to control the flow and direction of the pump.


Unlike a normal disconnect solenoid valve, the magnetic force of the proportional solenoid valve remains constant during the working stroke of the proportional solenoid. This attractive characteristic is formed by the special shape of the hydraulic working gas gap and the magnetic force of the magnetizer. The difference between a switch solenoid valve and a proportional solenoid valve does not depend entirely on the solenoid valve itself. When the proportional solenoid valve reaches its high current, the proportional solenoid valve acts like a disconnect solenoid valve. If we use different currents to energize the switch solenoid, closing the solenoid will also produce different thrusts.


NACHI hydraulic solenoid valve performance indicators

Hydraulic solenoid performance indicators include rated voltage, rated force, rated stroke and so on.


According to different voltages, the hydraulic solenoid valve can be divided into 12V DC electromagnet, 24V DC electromagnet, 110V AC electromagnet, 220V AC electromagnet and so on. The hydraulic solenoid valve NG6 is commonly rated at 20N - 70N and is typically rated at 3 - 7mm. If you suspect that the hydraulic solenoid valve is blocked or the solenoid is burnt out, flip the hydraulic valve and see if its rated stroke is within the common stroke range.


The external characteristic of a hydraulic solenoid is resistance. The common 24V hydraulic solenoid valve NG6 maintains a resistance range of 16 - 26 Ω. The 24V hydraulic solenoid valve of the cartridge valve has a resistance range of 20-38 Ω. The 24V proportional electromagnet has a resistance range of 21 - 26 Ω. In theory, the electromagnetic force is proportional to the square of the current, so the resistance of the 12V solenoid valve is about a quarter of the 24V hydraulic solenoid valve resistance.


For proportional solenoid valves, the current must reach a certain range. For example, a Rexroth 24V proportional valve proportional solenoid valve requires a current range of 200 - 600 mA, and a 12V proportional solenoid valve for Rexroth valves requires a current between 400 - 1200 mA.


Gregg Maintenance Advice for A&S Solenoid Valve Co., Ltd. Pre-sales Service Engineer

When the hydraulic valve is inoperative, the resistance between the hydraulic solenoid connector 1 and 2 can be measured. If the resistance value is infinite, it means that the internal circuit has been cut off. If the resistance value is small, it indicates an internal short circuit fault, so the hydraulic solenoid valve must be replaced. Circuit breaks and short-circuit faults are caused by overheating of the solenoid. To reduce the clogging of hydraulic valves, many hydraulic solenoid manufacturers will reduce the resistance of the solenoid to increase thrust. But in that case, the problem of overheating of the electromagnetic coil has also increased. After a few minutes of constant current, the internal temperature of the hydraulic solenoid valve may exceed 100 °C. Therefore, in the actual application process, we must not only pay attention to the heat dissipation of the hydraulic valve, but also cut off the power time. Hydraulic solenoids have high power frequencies and are more prone to burnout.