Recent Developments in Pressure Management

Transcription

1 Water Loss June 06-09, 2010 São Paulo/SP Recent Developments in Pressure Management Marco Fantozzi, MIYA Allan Lambert, ILMSS Ltd

2 The Renaissance in Pressure Management 2001: IWA International Report:Water Loss Management & Techniques only 10 of 22 countries used Pressure Management to manage water loss 2003: IWA Water Loss Task Force creates Pressure Management Group 22 practitioners, consultants, researchers from 10 countries starts to publish articles, case studies, research into concepts. Water 21, Oct 2003: Managing leakage by managing pressure Water 21, Dec 2006: Managing pressures to reduce new breaks papers at IWA Water Loss Conferences 2005, : IWA Water Loss Conference, Cape Town 450 delegates from 30 countries, 144 presentations many papers and case studies of pressure management all saying how pressure management reduces leak flow rates, burst frequencies, and other benefits

3 Pressure Management: IWA Water Loss Task Force Definition The practice of managing system pressures to the optimum levels of service ensuring sufficient and efficient supply to legitimate uses and consumers, while: reducing unnecessary or excess pressures eliminating transients and faulty level controls all of which cause the distribution system to leak unnecessarily

4 Basic, Intermediate and Advanced Pressure Management Basic: identify and reduce transients and surges achieve continuous supply (24/7 policy), even if at low pressure strategic sectorisation of system separate transmission system from distribution system monitor pressures, flows, bursts/leaks/repairs, complaints control of service reservoir levels to avoid overflows Intermediate: create smaller sub-sectors (Pressure Managed Areas or Zones) reduce pressure using fixed outlet PRVs or intelligent pumping Advanced: introduce time or flow modulation for valves and pumps

5 Pressure management benefits 1. Reduction of leak flow rates 2. Reduction of numbers of new burst and leaks reduces repair costs 3. Reduction of rate of rise of unreported leaks reduces costs of active leakage control 4. Deferment of infrastructure renewal costs extends infrastructure asset life 5. Reduction of some components of consumption 6. Improved customer service fewer interruptions, less damage to plumbing To make a financial case for pressure management, we need practical methods to predict these benefits This rest of this presentation will be an overview of concepts and prediction methods what we use now methods that are being improved important topics that need more research

6 Not only leakage management, but also. Demand management (conservation benefits) Water Utility: Asset Management, Cost reduction Customer benefits

7 Pressure Management Management Unavoidable Annual Real Losses Speed Active and Quality Leakage of Repairs Control Current Annual Real Losses Speed Active and quality of Leakage repairs Control Pipeline and Pipe Assets Materials Management: Management: selection, Selection, installation, maintenance, Installation, Maintenance, renewal, replacement Renewal, Replacement

8 1. Predicting changes in Leak Flow Rates Use Fixed and Variable Area Discharges (FAVAD) concept Leak flow rate L varies with average pressure P N1 N1 = 0.5 for Fixed Area leaks N1 = 1.5 for Variable Area leaks (area varies with pressure) Average N1 = 1.0 for many large systems Key prediction parameters are the RATIO of average pressures and the predicted N1 value Leaks on rigid pipes are usually Fixed Area (N1= 0.5) Undetectable background leaks and splits on flexible pipes are Variable Area (N1=1.5) An equation (in paper) can be used to predict N1 for distribution Systems and zones

9 N1 varies with pipe material and type of leak Fixed area leaks: N1 = 0.5 Variable area leaks: N1 = 1.5 Ring cracks, corrosion holes. Longitudinal splits in rigid pipes. Circular holes drilled in pipe (irrespective of pipe material) Undetectable small background leaks at joints Splits in flexible pipe Acknowledgement: van Zyl Acknowledgement: Tardelhi Filho - SABESP

10 2. Predicting changes in numbers of bursts, leaks and repairs 1995: UK data suggests relationship between pressure and mains bursts 2003: influence of pressure on bursts not generally recognised UK analysis of grouped bursts vs pressure shows no clear relationships only a few individual case studies: Australia, Italy, New Zealand, UK 2004: Gold Coast (Australia) Case Studies effective graphical presentation of monthly data, before and after WLTF members (Australia, Brazil, Italy, UK) collect 50 data sets 2005 Water Loss Conference : Paper by Pearson, Fantozzi, Soares, Waldron on the 50 data sets simple FAVAD equation (bursts vary with P N2 ) does not explain data but paper suggests ideas for a conceptual approach to problem 2006: Water 21 Article (Thornton & Lambert): 110 examples, 10 countries average % reduction in bursts = 1.4 x % reduction in pressure conceptual approach to explain how pressure and other factors affect bursts

11 UK evidence of pressure: bursts relationships ( ) UK: 16 District Metered Areas Mains burst frequencies/1000 conns/year UK : 10 large regions Mains burst frequencies per 100 km per year Bursts per 1000 properties per year Average Pressure (metres) MAINS BURST FREQUENCY/100 Km/ YEAR AVERAGE PRESSURE (METRES) Source: John May (1994) Source: Welsh Water (1995) Mains burst frequency varies with P 3?

12 2. Predicting changes in numbers of bursts, leaks and repairs 1995: UK data suggests relationship between pressure and mains bursts 2003: influence of pressure on bursts still not generally recognised UK analysis of grouped bursts vs pressure showed no clear relationships only a few individual case studies: Australia, Italy, New Zealand, UK 2004: Gold Coast (Australia) Case Studies effective graphical presentation of monthly data, before and after WLTF members (Australia, Brazil, Italy, UK) collect 50 data sets 2005 Water Loss Conference : Paper by Pearson, Fantozzi, Soares, Waldron on the 50 data sets simple FAVAD equation (bursts vary with P N2 ) does not explain data but paper suggests ideas for a conceptual approach to problem 2006: Water 21 Article (Thornton & Lambert): 110 examples, 10 countries average % reduction in bursts = 1.4 x % reduction in pressure conceptual approach to explain how pressure and other factors affect bursts

13 Pressure management, results achieved in Turin : Comparison of 6 years periods Source: SMAT, Italy (average values in previous 6 years) Volumes not measured QUINTINO SELLA (average values in last 6 years period) 23,3 % 21,7 % difference - 1,6 % Number of bursts % Electric Energy 87,3 Millions kwh 84,9 Millions kwh -2,4 Millions kwh Average Pressure 4,5 bar 4,1 bar - 0,4 bar -9% Production 178,6 Millions mc 177,5 Millions mc -1,1 Millions mc

14 2. Predicting changes in numbers of bursts, leaks and repairs 1995: UK data suggests relationship between pressure and mains bursts 2003: influence of pressure on bursts not generally recognised UK analysis of grouped bursts vs pressure showed no clear relationships only a few individual case studies: Australia, Italy, New Zealand, UK 2004: Gold Coast (Australia) Case Studies effective graphical presentation of monthly data, before and after WLTF members (Australia, Brazil, Italy, UK) collect 50 data sets 2005 Water Loss Conference : Paper by Pearson, Fantozzi, Soares, Waldron on the 50 data sets simple FAVAD equation (bursts vary with P N2 ) does not explain data but paper suggests ideas for a conceptual approach to problem 2006: Water 21 Article (Thornton & Lambert): 110 examples, 10 countries average % reduction in bursts = 1.4 x % reduction in pressure conceptual approach to explain how pressure and other factors affect bursts

15 2004: Gold Coast, Burleigh Heads Pilot Scheme: Gravity System, 3300 services, Inlet pressure reduced by 30% (72 metres to 50 metres) Night flow reduced from 6 litres/sec to 3 litres/sec Mains repairs reduced by 71% Service pipe repairs reduced by 75%

16 2. Predicting changes in numbers of bursts, leaks and repairs 1995: UK data suggests relationship between pressure and mains bursts 2003: influence of pressure on bursts not generally recognised UK analysis of grouped bursts vs pressure showed no clear relationships only a few individual case studies: Australia, Italy, New Zealand, UK 2004: Gold Coast (Australia) Case Studies effective graphical presentation of monthly data, before and after WLTF members (Australia, Brazil, Italy, UK) collect 50 data sets 2005 Water Loss Conference : Paper by Pearson, Fantozzi, Soares, Waldron on the 50 data sets simple FAVAD equation (bursts vary with P N2 ) does not fully explain data but paper suggests ideas for a conceptual approach to problem 2006: Water 21 Article (Thornton & Lambert): 110 examples, 10 countries average % reduction in bursts = 1.4 x % reduction in pressure conceptual approach to explain how pressure and other factors affect bursts

17 Predicting changes in burst frequency after pressure management (112 data sets) Overview of data average % reduction in bursts = 1.4 x % reduction in max. pressure can be higher (2.8 x) or lower (0.7 x), sometimes zero mains and services may respond differently, make separate predictions Plus Conceptual approach If initial failure rate close to low failure rate, % reduction in bursts will be small or zero (blue circle to green circle) Low failure rate If initial failure rate is high, large % reductions in burst frequency appear likely for reductions in maximum pressure (red circle to blue circle) Source of data: Thornton & Lambert (2007)

18 Low failure rates Failure rates used in the Unavoidable Annual Real Losses (UARL) formula for calculating Infrastructure Leakage Index (ILI) are shown below They can also be used as initial estimates of Low failure rates for predictions of changes in burst frequency after pressure management

19 3. Predicting changes in annual costs of Active Leakage Control (using Rate of Rise) Before Pressure Management After Pressure Management Level of Leakage Reported Leaks and Bursts Unreported Leakage Background Leakage Unreported Leakage Frequency and flowrates of reported leaks reduce Rate of rise of unreported leakage reduces Frequency and cost of economic intervention reduces Background leakage reduces Annual Real Losses Unreported Leakage Background Leakage Unreported Leakage 0,5 1 1,5 2 TIME (years) 2,5 3 3,5 4 4,5 Source of data: Fantozzi & Lambert (2007)

20 3. Predicted change in active leakage control costs At present, this is based on a theoretical calculation RR = Rate of Rise of Unreported Leakage Suppose that a 10% pressure reduction changes: leak flow rates by 10% number of unreported leaks by 10% Rate of Rise RR will reduce by (1-0.9 x 0.9) = (1 0.81) = 19% Annual cost of economic ALC interventions varies with RR 0.5 so annual cost of ALC reduces by 1 (0.81) 0.5 = 10% So perhaps predicted % reduction in annual cost of Active Leakage Control = % reduction in average pressure I would like to check this theoretical calculation if anyone has reliable data Pressure reduction does NOT mean that active leakage control can be stopped

21 4. Predicted change in deferment of mains and services renewals, and extension of asset life If a Utility has a policy replace pipes if more than X repairs in Y years, typical benefits can be assessed as schemes are implemented, bursts reduce and number of such renewals reduces average life of AC pipes increases as maximum pressure reduces does similar information exist for other pipe materials? Deferment of renewals and extension of infrastructure life will have the largest financial benefits; we are now taking the first steps to try to develop practical prediction methods Source: John Black

22 5. Predicting changes in Consumption Use the FAVAD concept, Consumption C varies with Pressure P N3 Estimate the percentage of consumption outside OC% Suggested exponent N3o for Outside consumption is 0.45 Suggested exponent N3i for In-house consumption is 0.00 for houses with private storage tanks 0.04 for direct pressure systems Quick method to estimate weighted exponent N3 Fix the In-house N3i value on the left side Y axis (0.04) Fix the Outside N3o value on the left side Y axis (0.45) Draw a line between them Enter an estimated C0% on the X-axis (25%) Read the weighted N3 from the left side Y axis (N3 = 0.14)

23 5. Predicting changes in outside Consumption: results of field tests in Australia Rigid Orifice Devices, N3o = 0.5 Pop-up Sprinklers Non-Rigid Orifice Devices, N3o = 0.75 Soaker Hose Spray Riser Network Oscillating Sprinkler Weeper Hose Tri-arm sled

24 5. Predicting changes in In-house consumption: some examples of recent tests in Australia Comparisons of metered consumption in Zones before and after pressure management: data adjusted for changes in consumption in control Zones Bench testing of toilet cisterns with leaking valves leaking outlet valve, N3 = 0; leaking inlet valve, N3 = 0.5

25 Fewer 6. Improved Customer Service bursts > fewer complaints Source: Bristol Water, UK Less damage to customers plumbing Australian plumbing standards now require maximum 50 metres pressure to avoid reducing the life of customers appliances (taps and fittings) and excessive noise.

26 Summary All of the 6 benefits described can contribute to the financial justification of pressure management but for some of them, prediction methods need to be improved The IWA WLTF Pressure Management Team is preparing Guidelines for publication in 2011 if you have data, information or comments to contribute, please contact allan.lambert@leakssuite.com or marco.fantozzi@ .it

27 Thanks! Recent Developments in Pressure Management Marco Fantozzi, MIYA Allan Lambert, ILMSS Ltd