We can describe solenoid valves as electrically controlled valves that are used to regulate fluid flow. They are available in very many types each having a specific application but with similar operating principles.
We are going to focus specifically on the Hydraulic Solenoid valves and get to know every detail about them.
What Is A Hydraulic Solenoid Valve
This is a directional valve that is mostly applied in a hydraulic system. It is controlled using a solenoid and is used to either open, close, or alter the flow direction of the liquid medium used.
The solenoid that controls it is an electric coil having a ferromagnetic core in the middle of it with windings around the core. It is designed with several chambers or ports which have a spool inside.
This spool is thrust into action using the solenoid that slides it inside the valve therefore closing or opening the ports for fluid flow.
Benefits Of Hydraulic Solenoid Valve
Hydraulic Solenoid Valves offer you a number of benefits when used in your application. Some of them include:
These valves are available in many models serving a wide range of applications. They can be designed to fit into a variety of hydraulic systems with various uses.
Fast and Efficient
The response of the valve is usually very fast after being energized. Remember, the solenoid valve can respond in just several milliseconds with the pilot valve reacting within tens of milliseconds.
A well-designed Hydraulic Solenoid Valve consumes very little power therefore saving a lot of energy. After energization, the valve position is switched automatically, and maintaining that position does not require any additional power.
Easy Leakage Control
Both internal and external leakages tend to compromise the safety and efficiency of valves. In other valves, the valve stem is controlled using either electrically or pneumatically meaning leakages on their dynamic seal.
The hydraulic solenoid valve uses electromagnetic force to exert pressure on the iron core. The dynamic seal does not exist in them meaning you can easily block any external leakage.
Simple And Easy To Use
This valve has a very simple structure that you can easily install and maintain. Their prices are also relatively cheaper compared to other regulating valves.
They usually act as an automatic control system that is triggered using a switch signal. This means that you can easily incorporate it with an industrial control computer.
Because they have very few movable parts, hydraulic solenoid valves do not need a lot of maintenance since they are less likely to break down. This simple design means that you can repair and clean them very easily therefore reducing downtime.
Components Of A Hydraulic Solenoid Valve
- Valve Body: contains various enclosed mechanisms and components that run the valve.
- Solenoid: it contains a coil within it that is energized to either open or close the ports for oil flow.
- Slide Valve: this controls the entry and exit of the hydraulic oil in the hydraulic solenoid valve
- Reset Spring: it is used to reset the valve back to its original resting position when the valve is de-energized
- Fault Check Button: used to test whether the hydraulic valve is functioning properly or not
How A Hydraulic Solenoid Valve Works
The Hydraulic Solenoid Valve has a valve body that contains several cavities or ports on it. All these ports have been connected to specific pipes carrying oil.
Usually, the piston is located in the middle of the cavity with two electromagnets positioned at either side of the valve. These electromagnets have solenoid coils that are energized to push the spool that opens or closes the different ports.
Remember, the inlet port is ever open therefore the hydraulic oil easily enters any drain pipe that is open under pressure. This oil pressure pushes the piston rod which in turn drives the mechanical device.
This means that you can control this mechanical movement by altering the electric current supplied to the solenoid.
Types of Solenoids Used In Hydraulic Solenoid Valve
For starters, the function of the hydraulic solenoid is very similar to that of a normal solenoid. The major difference between the two is in their design construction and their end function.
We have two basic types of Hydraulic solenoids distinguished by their designs. Let us have a brief look at their description:
This solenoid comes with a full solenoid unit designed as one component which offers the best performance. However, when you want to replace the solenoid, you must depressurize the whole hydraulic system.
Removable Coil Design
The design of this solenoid is in such a way that a separate tube is first installed and then the coil is later slid over it. Normally, the coil is then tightly secured into place using a nut.
The upside of this is that you can easily replace the coil without necessarily removing the tube. This means that the application will be constantly pressurized even with a coil breakdown.
Detent Mechanism In Hydraulic Solenoid Valve
In layman’s terms, we can describe the Detent mechanism as any mechanical/magnetic catch that hinders spool motion. This is the same mechanism applied in many hydraulic valves during de-energization to maintain the spool in a closed or open position.
During energization, the spool is immediately discharged and assumes its initial neutral position. In the case of a 2-position valve, the detention makes it possible for the spool to assume either position.
The same applies to the 3-position valve. After detention, the spool can be positioned in any of the three modes.
Choosing The Right Hydraulic Solenoid Valve
When you are going for a Hydraulic Solenoid Valve for your application, you need to settle for the best. This simple consideration will significantly help you settle for the most appropriate one:
Oil Flow Rate
The quantity of oil flow in your application largely determines what size of valve you are going to use. You should also factor in the pressure drop of the flow medium across the valve in addition to its flow rate.
The material used in making the valve should have qualities that are compatible with the hydraulic oil. Additionally, the properties of the material should not in any way react with the flowing media.
The valve you settle for must be strong enough to shoulder the most extreme pressure that your application can offer. It should be able to function optimally in such conditions otherwise it will be a safety hazard.
Ensure that your valve can operate efficiently within the maximum and minimum temperatures of your application. This is because temperature will also affect how viscous your flowing media will be and its flow rate.
Number of Ports
The number of ports is determined basically by your application requirements. This will also tell how these ports are positioned on the hydraulic valve.
More ports on your valve simply means increased chances for your selection flexibility. The manifolds in the solenoid valves are capable of sustaining many positions within a single valve.
This is also determined by the method by which your application operates. After de-energization, some applications will require the spool to remain in place while others will need it to return to the center.
Troubleshooting Hydraulic Solenoid Valve
A Hydraulic Solenoid is usually the directional type with regular malfunctions. Let us have a critical look at some of its parts that may normally pose an operational challenge and how you can go about fixing them.
Damaged Solenoid Coil
The major damage done on the coil is usually burning. They are majorly brought about by the quality of the coil in terms of a poorly processed core or a very thin wire diameter that overheats easily.
You can easily notice coil failures after the hydraulic valve has worked for a short period of time. The operating environment of the valve such as humidity can also lead to the solenoid coil getting damaged.
Push Rod Wear In The Solenoid Tube
The function of the push rod is to displace the spool based on the armature motion. Since the spool and the push rod are not fixed together, they are always in constant contact leading to wear.
The effect of this long-term contact at high frequency from the wear is the shortening of the push rod. This means that the valve spool will not be positioned at the correct place thus affecting the valve operation.
The easy fix is you replace the push rod to resolve this. Keep in mind that you should go for a replacement that has the original size measurement.
Valve Spool Outer Diameter Wear
We can mention this defect in the same breath as the valve house hole wearing out. If the oil being pumped has excess impurities, it will tend to hasten the degradation of the outer part of the spool.
You cannot totally avoid this kind of wear and tear though regularly the purity of the hydraulic oil used reduces it. Ensure that contamination of the hydraulic oil is at its minimum always to extend the valve’s service life.
Valve House Hole Wear
The valve core is always in motion and its movement reciprocates with that of the hole found in the valve house. The design of this valve contains an oil grove filled with oil to minimize this friction.
However, this does not completely eliminate the hole wear in the housing because of the solenoids working nature. Another countermeasure is having the valve house made of ductile iron.
This metal is strong thus reinforcing the house casing hardness. This will in turn reduce the rate at which the valve house hole deforms and wears off.
Reset Spring Breaking
This type of problem falls squarely on the type of material that is used to make the reset spring. The most suitable material is the high steel metal which is resistant to fatigue and has a very good elasticity.
When such a fault occurs, you should replace the two strings simultaneously even if just one has a problem. You should ensure that the length of the springs is the same as that of the replaced ones.
Industry Applications of Hydraulic Solenoid Valve
This type of valve is utilized in a wide range of industries that regularly use hydraulic systems in their operations. Let us have a look at the most common of them:
- Turbine systems for generating power
- Water supply and treatment systems
- Gas lines and Fuel supply plants
- Process Control applied in manufacturing and processing firm
- Hydraulic motors, hydraulic braking systems, and hydraulic pumps used in the automotive sector
- Various agricultural machinery
Clearly, hydraulic solenoid valves play an important role in modern hydraulic systems. At Target Hydraulics, we will help you get quality valves at affordable prices.
Solenoid Valve – Source: Wikipedia
Hydraulic Power Pack – Source: TARGET HYDRAULICS