AWWA Manual M77, Condition Assessment of Water Mains

Transcription

1 AWWA Manual M77, Condition Assessment of Water Mains Dan Ellison, PE Senior Professional Associate This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

2 Agenda» Why is condition assessment useful?» What needs to be considered in selecting an assessment method?» How are distribution mains commonly assessed?» How do I begin? What resources are available?

3 Every pipe infrastructure presentation has pictures like this Photo: Bill O Leary, Washington Post

4 .and like this Photo: Al Seib, LA Times

5 Life expectancies are vital for knowing what to replace and when Graphic: AWWA Buried No Longer

6 How to do condition assessment?» Please don t dig» Please don t put something in the pipe» Please don t interrupt operations» Please don t disrupt community activities» Make it very, very, very cheap» and also please tell us about every defect Photo by Bettmann/Corbis

7 The perfect assessment is infinitely expensive» Need to balance Access Customer service Costs / Benefits Other alternatives» Best to adopt multiple methods No single method finds all defects Most methods are blind in some areas

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9 PROBABILITY Low Med High Desk Top Analysis = Risk Prioritzation Repair on Failure Assess Proactively TAKE ACTION! Repair on Failure Actively Monitor Assess Proactively Repair on Failure Monitor Monitor Low Med High CONSEQUENCE

10 BY ITSELF, AGE IS A POOR PREDICTOR OF PIPE CONDITION» Yes, pipe failures increase with age» No, pipe lives are not found in a book

11 Break Rates Determine Pipe Life Expectancies for Small Mains» Break Rates are a Function of the Pipes Reactions to its Environment

12 Traditional Assessment Assessment Tools» Pit gauges» Ultrasonic gauges» Electro-magnetic scanning» Magnetic flux scanning» Potentiometer» Grit blast + visual Corrosion Survey External Direct Assessment

13 Leak Detection Has Also Been Used for Generations Difficult leaks to detect:» Large diameter pipes» Concrete pipes» Long distances between access points» Small leaks Now New & Improved! In-Pipe Tools Continuously monitoring methods Helium, Satellite, Electrical Photos: Intact Plumbing & Heating H2O Building Services

14 Acoustic velocity testing» Non-Invasive. Pipe access using existing appurtenances or vacuum-excavated keyholes.» Provides average thickness between transducers» Limitations: Does not detect isolated pitting Graphics: Echologics Photos: HDR

15 Enhanced Leak Detection and Video» In-pipe tools enable detection of very small leaks» Up to 5000 feet from 2-inch entry port» Video Lining Assessment» Free Swimming Tools also available Graphics: Pure Technolgies

16 Broadband Electromagnetic» External scanning using vacuum-excavated keyhole

17 Magnetic Flux Leakage» Widely used for oil and gas pipelines» High resolution scanning» Several technology providers» Has been used with success by SFPUC and SDWA» Limitations: Linings and scales may interfere Mortar-lining presents difficulties Tools are not well articulated Graphics: Pure Technologies Photo: SFPUC

18 Remote field electromagnetic scanning» Introduced in 1992 AwwaRF Study» Pros High resolution reporting of pipe wall defects Long runs possible Proven over two decades» Cons Must provide pipe access Graphics and Photos: PICA

19 NDE is rarely used for water mains, because» Cost: Money is better spent on renewal» Risk: Something could go wrong» Misunderstanding: Old mains have no value» Uncertainty: What do the data indicate?

20 Because NDE is seldom used for water mains..» Relatively strong mains are discarded because they are perceived to be weak» Unnecessary breaks occur because some weak mains are left in service too long» Renewal methods are not always appropriate for the condition of the host main

21 21 Water Research Foundation Projects Project 4471: Leveraging NDE» Use NDE to sample» Employ where easy Project 4473: Assess and Fix» Perform NDE with rehab» Tailor rehab using NDE

22 What about nonmetallic pipes?

23 Everything you ever wanted to know about AC pipe» Statistical analysis breaks caused by: Ground movement Pressure Age» Condition assessment nothing works really well Samples from failures often exceed minimum crush and burst strengths» Median longevity Type I (pre-1950) ~ 100 years Type II (post-1950) ~ 90 to 250 years

24 We Found that Stain Loss Calcium Loss Little Ca loss Major Ca Loss External Stain Loss Often was Carbonation

25 How do you find defects in PVC?» You generally don t they find you

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27 Coming Soon to an AWWA Bookstore Near You!

28 Coming Soon to an AWWA Bookstore Near You!

29 QUESTIONS? Dan Ellison, PE Senior Professional Associate Condition Assessment for Distribution Pipelines