I need your urgent help please .............
I'm making study about NG distributing system , I need some guide for design

and the case as follows :

I have industrial area consist of 12 factories , the distance between the first and last factory 12 Km .........
Also for the sub lines (from the main pipeline to the factory ) should I consider launcher and receiver for each sub line or Just blow them with air ....
the diameter of these sub lines varried from 3 inch to 6 inch ..........


Thanks all