1 19/12/2017 1 Latest Practical Advances in Pressure Management North American Water Loss Conference 2017 SAN DIEGO - December 3-5, 2017 Allan Lambert, Water Loss Research & Analysis [email protected]Marco Fantozzi, Studio Marco Fantozzi, [email protected]Kobus van Zyl, University of Cape Town, Kobus Van Zyl, [email protected]Mark Shepherd, JOAT Consulting, South Africa, www.joat.co.za Julian Thornton, Thornton International, [email protected]
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119/12/2017 1
Latest Practical Advances in Pressure Management
North American Water Loss Conference 2017
SAN DIEGO - December 3-5, 2017
Allan Lambert, Water Loss Research & Analysis [email protected] Fantozzi, Studio Marco Fantozzi, [email protected] van Zyl, University of Cape Town, Kobus Van Zyl, [email protected] Shepherd, JOAT Consulting, South Africa, www.joat.co.zaJulian Thornton, Thornton International, [email protected]
Variable area leakage Leak area varies with PVelocity varies with P0.5
Leak flow varies with P1.5
includes background leakage at joints and fittings, and splits in
flexible pipe materials
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N1 Power Law approximation of FAVADLeak flow rate L varies with PN1
• Initial average pressure Po
• Initial leak flow rate Lo
• Assume Lo = A x PoN1 …(1)
• New average pressure P1
• New leak flow rate L1
• L1 = A x P1N1 ……………(2)
For small changes in pressure , assume A and N1 almost constant
• Divide 2nd eqn by 1st eqn
• ‘A’ cancels out
• L1/Lo = (P1/Po)N1
Numerous tests show that N1 usually lies within the range 0.5 to 1.5
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Experimentos - Relacao dentre Vazao e Pressao
0
50
100
150
200
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450
0:00
0:25
0:50
1:15
1:40
2:05
2:30
2:55
3:20
3:45
4:10
4:35
5:00
5:25
5:50
6:15
6:40
7:05
7:30
7:55
8:20
8:45
9:10
9:35
10:0
0
10:2
5
10:5
0
11:1
5
11:4
0
Hora
Vazao
M3/h
ora
0
5
10
15
20
25
30
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45
50
mca
Flowrate m3/hr Pressure m
AZNPo
AZNP1
AZNP2
Customer night use
LoL1 L2
A 2-step N1 Night Test on Zone Vila Maria, SABESP, Brazil (1998)
L1/L0 = (AZP1/AZP0)N1 so N1 = ln(L1/L0)/ln(P1/P0)
Zone inflow rate m3/hr Average Zone Night Pressure (m)
Increased inflow to roof storage tanks
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Current use of N1 by Practitioners
• Since 1994, the N1 power law FAVAD is being widely used by practitioners internationally
• Most users tend to assume a constant N1• 1.0 (linear), or 1.15 (Japan)
• Some users try to predict N1 using component analysis, or pipe materials and snapshot ILI
• Some consultants carry out N1 tests• but most practitioners have never done so
• and more systematic training is needed
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Pressure Control expands after 1995
• Thousands of pressure control schemes installed internationally since 1995 to reduce leakage; justified economically due to• better methods to predict reductions in leak flow rates (FAVAD,
simplified to N1 Power Law)• advanced pressure control with flow modulation • methods to predict reductions in new burst frequency on mains,
and services, and extend infrastructure life
• As a consequence many systems now are operating at lower and more variable pressures
• It became necessary to review concepts used for calculations
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Recent collaborative research on FAVAD
• By Prof. Kobus van Zyl, Allan Lambert, Amanda Cassa, Dr Richard Collins and post-grad University of Cape Town students• Leakage Numbers for lab tests on pipe samples:
• Leak Area vs pressure relationships
• Influence of low/negative pressure on leak flow rates
• Open Access paper on hydraulic analysis by van Zyl, Lambert and Collins ASCE Journal of Hydraulic Engineering / Vol 143 Issue 9 - Sept 2017 ( 1000+ downloads)• summarised in Presentation 2017S on LEAKSSuite
• Allan Lambert has now applied FAVAD concepts to N1 tests, to get fast-track methods for practitioners to use
Ratio of Average AZP/AZP at hour of Minimum Night Flow: AZPave/AZPmnf
Night Day Factor = CF x 24 x AZPave/AZPmnf
N1 at AZPave = 1.49
N1 at AZPave = 1.40
N1 at AZPave = 1.30
N1 at AZPave = 1.20
N1 at AZPave = 1.10
N1 at AZPave = 1.00
N1 at AZPave = 0.90
N1 at AZPave = 0.80
N1 at AZPave = 0.70
N1 at AZPave = 0.60
N1 at AZPave = 0.51
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Summary and Conclusions
• FAVAD concept remains best available, now hydraulically validated
• N1 Power Law simplified FAVAD, assuming constant N1 for small pressure range, but N1 decreases as pressures reduce
• Leakage Practitioner approach: use Fast-Track FAVAD to • quickly identify Fixed and Variable components from N1 night test • quickly calculate N1 vs AZP Type Curves, to check assumed N1s• quickly calculate Zonal L vs AZP equation derived from N1 test• derive continuous leak flow rate profile from recorded AZP pressures• split Zonal 15 minute inflows into leakage and consumption• check validity of Night-Day Factor calculations, improve where needed
• Combination of Academics and Practitioners is mutually beneficial if the different approaches, experiences and communication needs of both communities are recognised when disseminating the outcomes
• Additional free references are available at http://www.leakssuite.com/influences-of-pressure/
• John May, for laying the foundations of these studies 23 years ago
• Prof. Kobus van Zyl, Richard Collins and post-graduate students of University of Cape Town for reinvigorating Fixed and Variable Area concepts.
• Many other colleagues in the Pressure Management Team of the IWA Water Loss Specialist Group, for ongoing successful international promotion of the benefits of well targeted pressure management.
• The LEAKSSuite website for making so much material available, free to all; now over 26,000 users worldwide
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Latest Practical Advances in Pressure Management
North American Water Loss Conference 2017
SAN DIEGO - December 3-5, 2017
Allan Lambert: Water Loss Research & Analysis [email protected] Fantozzi, Studio Marco Fantozzi, [email protected] van Zyl, University of Cape Town, Kobus Van Zyl, [email protected] Shepherd, JOAT Consulting, South Africa, www.joat.co.zaJulian Thornton, Thornton International, [email protected]