An alternate easy-to-use procedure is presented to draw n-compressor membrane cascades for gas separation applications with n greater than or equal to 1. First, a master cascade is created by inserting ’introduced’ membrane stages in a known membrane cascade containing a large number of compressors. Then an n-compressor cascade containing the maximum number of membrane stages is generated from the master cascade by eliminating the unwanted recycle-compressors and the membrane stages associated with these eliminated recycle-compressors. From the resulting n-compressor cascade, only the introduced membrane stages are then removed to yield an n-compressor cascade with the desired lower number of membrane stages. When substructures containing n-compressors are generated from a master cascade, equations are derived to provide information such as the maximum and the minimum number of membrane stages which can be present in these substructures, the number of substructure cascade schemes with a given number of membrane stages and the total number of feasible substructure cascade schemes.