# 2010 Vancouver
Historically, polyethylene (PE) gas pipe systems in the United States have operated at service conditions for which the likelihood of a failure due to a rapid crack propagation (RCP) event has been nearly non-existent. The exceptional safety record for PE piping systems in this critical application has resulted in a more wide-spread use of these piping products and utilization of larger diameters and heavier walled pipe has become more prevalent. As the US gas distribution industry expands the use of PE piping systems, the need to understand and utilize responsible engineering design to minimize the potential for failure due to RCP has become more apparent. The discussion provides a very basic review of the nature of RCP, how it is measured using industry-accepted standardized test methods, and what it means in relationship to the design and use of polyethylene gas pipe. Two key properties, the critical temperature and the critical pressure, and their relationship to the potential for an RCP occurrence are reviewed as well as the various parameters that influence this relationship. From there, suggested design guidelines established by the US gas distribution industry to assist the designer, installer and operator in the safe and responsible use of tough, durable polyethylene gas distribution systems are reviewed. This paper then reviews the series of initiatives that have been undertaken within the United States to incorporate the use of RCP data in the responsible design of PE gas distribution piping systems. The discussion concludes with an understanding that to minimize the potential for an RCP occurrence the critical temperature should be lower than the system operating temperature, and the critical pressure should be greater than the system leak test pressure.