Instrument Air Pipe Sizing - Dumb Question

Hi guys,

Since instrument air systems are pressure-based and not flow-based, how are the line sizes calculated? There typically is little/no flow loss for the operation of valves.

For preliminary pipe size calculations, Pie are squared is used, n'est-ce pas?

Given good fail-safe design (all control elements default to a non-nasty natural state) how is a proper IA system sized?

Some other piping/control/valve terminology: air to open, air to close, fail open, fail closed. I used to vaguely understand all this but my brain has gone soft with all this computer stuff.

It'd be nice if someone could summarize since I tried to explain it to a intermediate-level piping design modeller and found myself wondering if I had it right. I told him I'd get a definitive answer so I'm appealing to you guys - I don't want to steer him in the wrong direction due to my own possible ignorance.

Paul "I are not an engineer" Bowers Received on Fri Jan 28 22:02:00 2005