Replacement Project of Aged Pipes in Tokyo

Transcription

1 Replacement Project of Aged Pipes in Tokyo IWA World Water Congress VIENNA 2008 Waterworks Bureau of Tokyo Metropolitan Government Rights Reserved. 1

2 Table of Contents 1.Outline of Services in Tokyo Waterworks 2.Research of aged-pipe s damage 3.Customer s research 4.Effect of pipes replacement 5.Plan of pipes replacement Rights Reserved. 2

3 Outline of Tokyo Waterworks Table 1 : Service area etc. Population served 12,224,600(people) Service area km 2 Rate of service pervasion 100% Number of service connections Total length of distribution pipes Total production capacity 6,550,000(cases) 25,262km 6,860,000(m 3 /day) Total annual water supply volume 1,610,600(10 3 m 3 ) Max. daily water supply volume Av. daily water supply volume 4,960,000(m 3 /day) 4,380,000(m 3 /day) (as of Mar. 2006) Rights Reserved. 3

4 Pipe length by kind Kind Length(Km) Propotion Build year Cast-iron % ~1969 Early Ductile (mixed with iron) 2,312 9 % 1969~1973 Ductile 22, % 1973~present Steel % PVC 33 0 % total 25, % Rights Reserved. 4

5 Character of early ductile pipes Straight pipes are ductile but bending pipes are cast-iron Bending pipes are easy to rust because they aren t coated Bending pipes are easy to pull out by earthquakes Not covered with polyethylene sleeves to prevent from corrosion Rights Reserved. 5

6 Items of research Item Outside research Inside research Soil research Content corrosion of pipes and bolts, depth of pitting etc. exfoliation of seal-coating, neutralization of mortar lining, thickness of scale, depth of pitting etc. Soil quality, moisture, specific resistance, ph, sulfide etc. Rights Reserved. 6

7 Corrosion inside of a pipe (without mortar lining) Maximum scale is 45.0mm thick 曲 管 on 45 φ Bending pipe 最 大 (diameter:100mm) スケール 厚 45.0mm Photo 2 Corrosion inside of a pipe Figure Copyright 3.4 Corrosion 2008 Bureau inside of Waterworks, of pipe Rights Reserved. 7

8 Neutralization of mortar lining Neutralization ratio (%) y=0.0469x x x:time after buried(years) y:neutralization ratio (%) Researched sub-main pipe Researched main pipe Time after buried (years) Figure 3.3 Neutralization of mortar lining Rights Reserved. 8

9 Mmaximum pitting is 4.6mm 直 管 φ150 最 大 孔 食 4.6mm in straight Pipe (diameter:150mm) Figure 3.1 Picture of corrosion outside pipe Rights Reserved. 9

10 Figure 3.2 Corrosion of bolt Corrosion of a bolt Rights Reserved. 10

11 2 Soil types in Tokyo JR Keihin 京 浜 -Touhoku 東 北 線 line Arakawa River Soil type 1 地 盤 Ⅰ (Black soil) 1300km Early ductile pipes 地 Soil 盤 type Ⅱ 2 (Clay) 1200km Early ductile pipes Tamagawa River 図 7 Rights Reserved. 11 地 盤 分 布 図 Figure 3.7 Map of Tokyo 23 Wards

12 Covered with polyethylene sleeves Rights Reserved. 12

13 Result of customers survey How much do customers expect us to prepare for accidental breaks, leakage and earthquakes? Can't answer Not expect No answer Strongly expect Expect A little expect 14.7 Rights Reserved. 13

14 Benefit Cost Performance of project Table 4.1 Benefit Cost performance (Unit:billion yen) Cost (C) Benefit(B) At the time of earthquake 5.8 At normal time Total Benefit Cost performance (B/C) 1.37 Rights Reserved. 14

15 Project of pipe s replacement Object : Early ductile pipes Distance : 1200km(in the clay) Cost : US$ 1.2billion Terms : 10years Rights Reserved. 15

16 Advantages of project 1. Prevention of leakage 2. Improvement of earthquake-resistance 3. Prevention of muddy water 4. Reply to customer s need Rights Reserved. 16