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Electronic Valve Actuation Types Explained

Valve actuation is what shifts the valve from one position to another and there are two popular types that need to be considered in selecting the proper valve for any application. The actuation can be any of the functions or porting discussed above and is another valve characteristic that is important to understand.

Direct Acting

Direct acting valves are simple in design since the actuation of the valve directly translates into the change of the position. This is typically achieved by moving the valve element via a magnetic coil. All of the Clippard EV Series valves are direct acting since energizing the coil directly lifts the spider (a flat armature spring) to change the flow state. The benefits of direct acting valves are that they have no minimum pressure requirements, fast response time, and long life due to few moving parts. The lack of pressure requirements makes the valve design ideal for universally ported functions. Clippard's EVO-3-12 is a great example of a universally ported valve. The EVO-3-12 can be used with 80 psig on the normally-open inlet port, vacuum on the normally-open exhaust and select between them for an output.

Pressure Assisted

Pressure assisted valves are the most common valves used in automation applications. They rely on the pressure supplied to the valve to assist with actuation. The amount of force available from pressurized air to shift a valve is far greater than the force that can be generated from a magnetic coil on a direct acting valve with similar flow and pressure ratings. Once the internal pilot valve opens the pressure will assist the valve in shifting. This allows the ports to open and the valve to flow at high flow and/or pressures.

The benefit of pressure assisted valves is that they can take little electrical power because they are using the power of pressurized media. This allows for a smaller overall size for the given flow rates and port size. The drawbacks can be that they require a minimum pressure and don’t allow universal porting options unless the pilot pressure is from an external force.

Pressure assisted valves are generally engineered for specific applications to achieve the maximum flow and pressure ranges while using the smallest amount of electrical power possible. Other pressure assisted valves that do not have internal pilots are balanced and tuned so that pressure works in conjunction with spring forces and the coil to lift the seat and allow for flow. An example of a pressure assisted valve is the Clippard Maximatic MME-41PES-D012. Energizing the coil on the MME-41PES-D012 applies pressure to a piston to shift the spool in the valve.

For help selecting the best valve for your application, call 877-245-6247 or contact your local distributor.

By Mike Kettering • Technical Sales Specialist • Clippard