Valves are typically sized based on how much air they can move. The flow coefficient or 'Cv of the valve' is critical to determining if a cylinder or other actuator can move with sufficient speed for the application. A valve with a higher Cv can move more air. To account for various losses in all pneumatic systems, remember to oversize by at least 25%. Here is an interactive timing chart showing actual Cv values for Nitra® valves and bore sizes for Nitra® cylinders.
The formula below can be used to calculate the MINIMUM Cv or 'coefficient of velocity' required for operating a particular size air cylinder in a specific time period. There are many other factors that affect cylinder speed, such as tubing size and length; fitting size and shape (ninety-degree bends are especially disruptive to air flow), etc. This formula should be used as a guideline ONLY to determine a MINIMUM Cv for a given system.
Here is an interactive timing chart showing actual CV values for Nitra® valves and bore sizes for Nitra® cylinders.