Compressed Air - Maximum Velocity

http://www.chemicalprocessing.com/articles/2005/12.html

1. Zero, whereupon the head loss will also be zero.

2. Yes, although a cheapo gate valve will be even more cost effective (in the short run).

1. dear sir i m talking about operating system

2. if we go for threaded ball valve , then there will be some leakage problem hw we can handle it

2. Use good "pipe dope," also known as pipe joint compound. There are several brand names and formulations, so you need to check whether they are suitable for your service.

A bit OT now, but one of the most interesting of these is "X-pando", a gray powder that is mixed with a small quantity of water. It is an industry standby for ammonia connections. This family company is (or was) headed by D. Keith Mano, who wrote popular short stories, many in "Playboy." Google for more info.

1. You asked to minimize pressure drop, which would be zero, instead of asking for a range of suitable (economical) pressure drops versus pipe size. I don't do that much air, but as a wild guess, I might pick 20 feet per second, but it will depend on the pressure; in particular what pressure is available from the compressor versus what the appliance needs. For compressible gas flow, the ASHRAE 15-2007 formula used for relief valve discharge piping calculations might be the best. The Industrial Refrigeration Consortium (Univ. of Wisconsin) has a down-loadable calculator for this. Google again.