A Study on Long-Term Durability of Polybutene Pipes Used in Hot Water Systems

Abstract

Thermoplastics pipes are gaining importance in pipe applications such as for hot water supply systems. This paper presents the pressure test results of polybutene hot-water pipe, diffusion analysis, and the new accelerated method to evaluate the effect of the environmental conditions. The pressure tests have been performed using water as the internal media and air as the external medium at temperature in a range of 80 to 120℃ over 60000 hours. The transition from the failure by crazing (Stage II) to the failure by oxidation (Stage III) was evaluated and the design stress was discussed using Stage III failure time. The migration of the antioxidant from pipe to the surrounding media was analyzed using the antioxidant -profile data. It was found that the environmental effects on Stage III failure could be discussed through Biot number. Finally, it was shown that the accelerated method using the thin film was fruitful.