DURABILITY EVALUATION TO RESIDUAL CHLORINE ON PLASTIC PIPES FOR HOT WATER SUPPLY - THIRD REPORT

摘要

Recently, the polymer electrolyte fuel cells (PEFC) cogeneration systems with plastic pipes for hot water supply has been commercialized in Japan. The pipes for hot water supply are installed with bending from the polymer electrolyte fuel cell to inside a house without using fittings. However, it is expensive and hard to replace these plastic pipes. These pipes which installed with bending were not evaluated in the residual chlorine solutions for long term. Accordingly, it is important to evaluate the durability and to predict the lifetime of these bent pipes. This study intended to evaluate the bent pipes in the residual chlorine solutions early. The residual chlorine solution immersion test for the bent polybutylene (PB) pipes and the bent double-layer crosslinked polyethylene pipes (PEX2) was conducted at 80 °C, 90 °C and 98 °C. In the residual chlorine solution immersion test, the concentration of the residual choline solution is 5 ppm and 10 ppm for 80 °C, 5 ppm for 90 °C and 5 ppm for 98 °C. As a result, it took much time to get the results back from this immersion test beyond expectation. It was found that the bent polybutylene (PB) pipes had the cracks over for 36,000 hours at 5 ppm in 90 °C, over for 40,000 hours at 10 ppm in 80 °C and over for 44,000 hours at 5 ppm in 80 °C. On the other hand, the bent double-layer crosslinked polyethylene pipes (PEX2) in the residual chlorine solution immersion test did not have the crack at all over for 47,000 hours.