PIPELINE PURGING PRINCIPLES AND PRACTICE

Gas purging, a process of displacing one gas by another gas, occurs on a routine basis in the natural gas industry when pipelines are purged into and out of service. In a project sponsored by the Gas Research I nstitute and in cooperation with the American Gas Association (A.G.A.) , the purging practices as outlined in the A.G.A.'s pipeline purging o perations occur under conditions not addressed directly in the manual. The program focus is on the purging procedures outlined in Chapter 8 of the manual entitled ''Gas Transmission and Distribution Pipes.'' Th e technical objective of the project was to develop an understanding o f the scientific principles upon which safe, practical purging practic es can be based. Direct displacement and inert gas slug purging operat ions are explained in terms of dispersion and mixing parameters and th eir relationship to the gas velocity. Field data compared to the resul ts of an analytical mixing model. Computer software for planning safe and cost-effective pipeline purges has been developed. Finally, recomm endations for revising Chapter 8 of the A.G.A. manual are presented.