Covers the minimum requirements for dry and flooded helical lobe rotary compressors used for vacuum or pressure or both in petroleum, chemical, and gas industry services. It is primarily intended for compressors that are in special purpose applications, and does not cover portable air compressors, liquid ring compressors, and vane-type compressors. This edition also includes a new Inspector's Checklist and new schematics for general purpose and typical oil systems.