Studies to Theorize on the Minimum 100 years Lifetime of the Polyethylene Piping System for Water Supply

Session 7A
5:10 pm

Kenji Mizukawa, Sekisui Kanzai Technics Co., Ltd.

Since the Great Hanshin Earthquake occurred in January 1995, the quake-resistance standards of buildings and civil structures in Japan have been reviewed. Attention has been focused on the use of piping materials having excellent earthquake resistance in our lifeline utilities. In this process emerged Polyethylene Pipe for Water Supply (PE100, SDR11, Safety Factor = 2).

The Waterworks Vision publicized in 2004 by the Ministry of Health, Labour and Welfare of Japan, showing the future image of our water works after about 10 years, indicates that the earthquake resistance of our key pipelines should be aimed at 100%. (In Japan, earthquake resistance pipes are 1) ductile cast iron pipes equipped with earthquake-resistant fittings, 2) steel pipes equipped with welded fittings, and 3) polyethylene pipes for water supply equipped with heat-fusion fittings.) This has helped remarkable increase of the application of Polyethylene Pipes for Water Supply in recent years in Japan.

Now, the coverage of the water supply system exceeds 97% in Japan, and renewal of decrepit pipelines is an important issue. But, many of our water supply business units are facing financial difficulties and the renewal rate is as low as 1% on a nationwide average. In order to promote the renewal of the pipelines continually for the future, the pipelines having a minimum lifetime of 100 years are required now. Polyethylene Pipes for Water Supply are designed by using the 50 years creep strength. In order to meet the strong requests from the Japanese water business units, we, POLITEC, have commenced our studies to theorize on the minimum 100 years lifetime of Polyethylene Piping Systems for Water Supply.

With respect to the piping materials, we are setting points of view on their long-term creep test data, repeated fatigue test data and stress concentration scale-up factors, and continuing efforts to propose the appropriate numerical value for the total safety coefficient.

Takashi Kuriyama
Prof. Yamagata University, Japan (Adviser to POLITEC)　 　

Kenji Mizukawa
Project Leader

Hiroyuki Kurio
Project Manager　　

Hiroaki Sakamoto
Chairperson Engineering Committee