new festo valves

[Tristan Lall]

If I were inspecting your robot, I'd be inclined to reject the Pneuaire chart you linked.

The C_v of a valve depends on its internal geometry, measured at a given set of working fluid conditions. Relating the port diameter to C_v is not even remotely accurate—especially when it isn't clear whether those are actual diameters, or nominal NPT diameters. Also, despite a similar-looking valve being pictured (to the 2009-and-earlier Festo valves), there's no model number or manufacturer specified.

Now, with regard to C_v and that Festo valve, you can derive it from the flow rating in standard cubic feet per minute (SCFM), which is given on the specification sheet (as "cfm"). The conversion process is documented here (for example).

Since FIRST hasn't specified the pressure at which the 0.32 C_v rating applies, you might rightly wonder how to calculate the C_v properly. Manufacturers often provide C_v at the maximum operating pressure (usually around 120 lb/in², but varying considerably depending on the parts). By contrast, FIRST established this limit based on the flow of the 2010 KOP Festo valve at 60 lb/in²,* but never specified this in the rules.

My calculations for the 2009 KOP Festo valve (unofficially) yield C_v = 0.395 at 25°C and 60 lb/in², and C_v = 0.177 at the same temperature and 120 lb/in². To be absolutely sure, contact Festo using the phone number listed on the datasheet and get the maximum pressure rating, operating pressure rating and C_v (and the pressure and temperature at which that C_v is valid).

Of course, you can also run multiple valves in parallel, and increase the flow of the entire system.

*According to the explanation that was provided to robot inspectors by FIRST staff.