We all know that purchasing legal copies of gas industry standards, for that matter all technical standards, is a pricey affair on individual level. But that doesn’t mean that there are no free lunches…there are…:)
You may visit the following link to download legal copies of some free standards from IGEM (Institute of Gas Engineers & Managers).
http://igemshop.helixsoftware.co.uk/category/68-show-all.aspx?orderby=10
I am sure you will find these useful, specially, IGEM/G/4 ‘Definitions for the gas industry’.