Knowing your poppets from your spools

Andy Parker-Bates, Product Manager for pneumatics at Festo, said: “Production demands have led to an extension of the range of available technologies and valve types, models, and their properties, so choosing the best fit for your application has become increasingly complex in recent years. We felt it was time to share our expertise and help our customers to choose the best valve for the job.”

Included in the guidance are descriptions of poppet and piston spool valves (the most commonly used valves in pneumatic applications), their operation and respective pros and cons. For example, poppet valves are lower cost and offer good switching times, but provide lower flow and can be noisier than other alternatives. Hard-sealed spool valves will also experience leakage and lower flow rates but are more durable and do not stick after long periods of inactivity.

Soft-sealed spool valves have traditionally been relatively expensive due to seal wear, but now normally come with a cartridge which holds the gaskets and sealing rings. This greatly reduces wear and increases their working life, as well as enabling the valve to operate at up to 16 bar and with vacuum. If you are looking for a valve with low leakage, the option of vacuum and ejector pulse, or if you require higher operating pressures, the most suitable option is probably a piston spool valve with cartridge sealing technology.

In addition to valve operation, Festo’s guidance also covers associated topics such as connectivity, mounting and correct sizing of valves.

“Oversizing valves can lead to connectors, tubing and sometimes actuators being larger than necessary, which adds additional component cost as well as using more air and therefore energy,” said Parker-Bates. “Undersized valves on the other hand cause restrictions in the circuit and can seriously impair the performance of the system.”

Festo’s guidance is available free online in a number of formats, including a series of short videos and, for those seeking more in-depth information, a white paper giving a technical comparison of available solenoid valves.