Solenoid valves are responsible for controlling the flow rates of either liquid or air and can be found in most power tools as well as other mechanical systems. Their diversity makes them able to perform many tasks, both easy and complex. For this reason, they are found in a wide variety of items including but not limited to dishwashers and hydraulic pumps. Solenoids can be customised for your specific needs to control mediums such as air, gas, steam, oil or electricity.

The most common version is the two-way valve. It has two ports whereas more advanced options offer three or more. The various numbers of ports needed will depend on what is needed. Since each version has different operating techniques, the right one needs to be selected for your equipment. All of these come under two major categories; direct acting valve or pilot operated valve.

The information below was sourced from and Wikipedia.

Direct Acting Valves

With this type, the coil mechanism opens the valve up through direct magnetic attraction. This lifts the shaft and seat without needing any external pressure.
Full power is required for these when they are opening, but they can hold this position, even when operating under low power.

Pilot Operated Valves

With a different operating technique, the plunger opening up the pilot and built up pressure pushing it open and closed. Electrical engineers say that “These do not need as much electrical power to work, however for them to remain open, they need to maintain full power.” Their overall performance is slower than their more direct counterpart.

Two-Way Valves

Both ports on these alternate and permit or stop flow. They are usually defined as either normally open or normally closed. When normally open, it remains this way unless some form of current is applied, forcing it to close. Once power ceases, it will automatically re-open to its original state. The normally closed option is the more common of the two, and functions the exact opposite way, remaining closed until a power surge forces it to open.

Three-Way Valves

These solenoids have three ports and are most often used when both alternate and exhaustive pressure is required. “Typical uses for this type of operation is found in regular household items such as dishwashers and coffee machines” notes CGIS.

Four-Way Valves

With four or more ports, these solenoid valves are typically used alongside an actuator. Two of the ports will supply the pressure while the other ports deliver exhaust pressure. Four-Way choices are often specified as normally open, normally closed or universal.

Before you set out to buy a solenoid, it is a good idea to learn about the different types. With so many options you want to make sure you get the right fit for your project. You need to consider the type of fluid that will be used as well as the system specifications and requirements. You also need to know what kind of material would be best for the seals. Regardless of the medium used by your equipment be it air, gas, steam or oil, efficient operation will require the right choice.

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