Water UK Annual Leakage Conference 2012
18th October 2012, Coventry
Relationships between pressure,
bursts and infrastructure life
– an international perspective.
Allan Lambert,
Water Loss Research & Analysis Ltd
Leader, 1st IWA Water Loss Task Force 1995-99
IWA Water Loss Specialist Group Management Team
Audience Participation!
Do you believe that pressure management has
an important role in Asset Management?
•
influencing burst frequency on mains?
•
influencing burst frequency on services?
•
extending residual infrastructure life?
IWA Water Loss Task Forces
(1995 – 2009) and Specialist Group
•
International workshops
– 2003: Anaheim and Oregon (USA)
– 2004: Ferrara (Italy) and Marrakech (Morocco)
– 2005: Australia, Santiago (Chile), UK
– 2006: Italy, Beijing (China), Macedonia
•
Water Loss Conferences
– Lemesos, Cyprus, October 2002
– Halifax, Nova Scotia, September 2005
Hundreds of freely available articles,
papers, Guidelines using
internationally applicable practical
concepts and terminology
– Bucharest, Romania, September 2007
– CapeTown, S. Africa, April 2009
– Sao Paolo, Brasil, June 2010
– Manila, Philippines, February 2012
– Ferrara, Italy, May 2012
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 distribution systems to leak
unnecessarily
UK evidence of pressure: bursts
relationships (1994-95)
John May 1994: 16 District Metered Areas
Mains burst frequencies/1000 conns/year
M A IN S B U R S T F R E Q U E N C Y /1 0 0 K m / Y E A R
B
u
r
s
t
s
p
e
r
1
0
0
0
p ro p e rtie s p e r y e a r
40
10
8
6
4
2
0
0
Morrison & Lambert 1995: 10 large regions
Mains burst frequencies per 100 km per year
30
20
10
0
20
40
60
80
Average Pressure (metres)
100
0
20
40
60
AVERAGE PRESSURE (METRES)
80
100
International Pressure Management
2001: IWA International Report: Water Loss Management & Techniques
– only 10 of 22 countries used Pressure Management to manage water loss
– only 1 mentioned influence of high pressure on ‘damages’
2003: IWA Water Loss Task Force creates Pressure Management Group
–
–
–
–
practitioners, consultants, researchers from 10 countries
starts to publish articles, case studies, research into concepts….
Water 21 articles: Oct 2003, Dec 2006, April 2011
Papers at IWA Water Loss Conferences 2005, 2007, 2009, 2010, 2011
2012: IWA ‘Water Loss’ Conference, Manila
– 525 delegates from 50 countries, 121 presentations
– many papers and case studies of pressure management
– all saying how pressure management reduces leak flow rates, burst
frequencies, and other benefits
2004: Gold Coast, Burleigh Heads Pilot Scheme:
Gravity System, 3300 services
Inlet pressure reduced by 30% (72 metres to 50 metres)
Source: Wide Bay Water/ Gold Coast Water
Reduction of Excess Pressure: 2005 UK example
Source:
David
Pearson
Retrospective analysis – effect not identified when PMZ set up in 2001
Country
Australia
Brisbane
Number of
Pressure
Managed
Sectors in
study
1
Assessed
initial
maximum
pressure
(metres)
100
Gold Coast
10
60-90
Water Utility or
System
4
100
7
39
3
50
Caesb
2
70
Sabesp ROP
1
40
Sabesp MO
1
58
Sabesp MS
1
23
SANASA
1
50
Sanepar
7
45
Halifax
1
56
Armenia
25
100
Palmira
Bogotá
5
2
80
55
Lemesos
7
52.5
Bristol Water
21
62
United Utilities
10
47.6
1
1
1
112
Maximum
Minimum
Median
Average
Average
Average
69
130
199
Yarra Valley
Bahamas New Providence
Bosnia
Gracanica
Herzegovin
Brazil
Canada
Colombia
Cyprus
England
Torino
Italy
Umbra
American Water
USA
Total number of systems
199
23
57
71
Average % Average
reduction
%
Mains (M) or
in
reduction
Services (S)
maximum
in new
breaks
pressure
35%
28%
M,S
60%
M
50%
70%
S
30%
28%
M
34%
40%
M,S
59%
M
20%
72%
S
58%
M
33%
24%
S
30%
38%
M
80%
M
65%
29%
S
64%
M
30%
64%
S
50%
M
70%
50%
S
30%
M
30%
70%
S
23%
M
18%
23%
S
50%
M
33%
50%
S
75%
94%
M,S
30%
31%
S
45%
M
32%
40%
S
25%
M
39%
45%
S
72%
M
32%
75%
S
10%
45%
M,S
39%
71%
M,S
36%
50%
M
75%
10%
33.0%
38.0%
36.5%
37.1%
94%
23%
50.0%
52.5%
48.8%
49.5%
All data
All data
All data
M&S together
Mains only
Services only
Water 21, 2006
pressure: breaks
data analysis
10 countries,
112 systems
On average, 38%
reduction in Pmax
produced 53%
reduction in bursts
Source: Thornton & Lambert
Water 21, Dec 2006
FAILURE
RATE
COMBINATION OF FACTORS
CAUSES INCREASED
FAILURE RATE
Operating range
TEM
PER
ATU
RE
GR
OU
ND
MO
VEM
TRA
ENT
FFI
C L
OAD
ING
AGE
+C
OR
RO
SIO
N
WLTF pressure:bursts initial concepts
and prediction methods, in 2006/07
The ‘straw that
breaks the
camel’s back’
concept
PRESSURE
For Zones with high
initial Burst frequency
assume average
Slope S (based on
112 PMZs data) = 1.4
On average, a 30% reduction in maximum pressure produces a 42% reduction in bursts
Sources: Thornton & Lambert, Water 21 Dec 2006; IWA Water Loss Bucharest, Sep 2007
SIMPLE 2006 APPROACH TO IDENTIFY ZONES
WITH GOOD POTENTIAL FOR REDUCTION OF
BURSTS ON MAINS, AND ON SERVICES
DON’T mix mains and services data – each can respond differently
FAILURE
RATE
UARL reference burst frequencies for
infrastructure in good condition:
Mains 13 per 100 km/year
Comm. pipes 3 per 1000 conns/year
Supply pipes 2 per 1000 conns/year
PRESSURE
Source: Thornton & Lambert, IWA Water Loss Bucharest, Sep 2007
Applying the basic IWA concept – Scheme
prioritisation, Bristol Water (2008)
A UK Water Company with 285 District Metered Areas
Initial Burst mains frequency ratio , using Maximum pressure
Burst frequency ratio (Actual break frequency/UARL
break frequenct)
6.0
Initial burst mains
frequency ratio > 3
used in pressure
control scheme
prioritisation, in
conjunction with
service burst
frequency ratio, Real
Losses reduction and
Consumption impact.
5.5
5.0
4.5
4.0
3.5
3.0
2.5
Average max
pressure = 50 metres
2.0
1.5
Average Mains Break
ratio = 1.5
1.0
0.5
0.0
0
20
40
60
Maximum pressure mH
Source: F van der Kleij, Bristol Water
80
100
120
Australian WSAA PPS-3 Asset Management Project 2008-11
Framework for targeting Leakage and Pressure Management
•
•
•
Conservation benefits: Demand management
Water Utility benefits: Asset Management, Opex/Capex reduction
Customer benefits: better managed delivery of service
PRESSURE MANAGEMENT: REDUCTION OF EXCESS AVERAGE AND MAXIMUM PRESSURES
CONSERVATION BENEFITS
REDUCED FLOW RATES
WATER UTILITY BENEFITS
REDUCED FREQUENCY OF BURSTS AND LEAKS
DEFERRED
REDUCED FLOW REDUCED
RENEWALS
RATES OF
REDUCED
REPAIR
AND
LEAKS AND
CONSUMPTION
COSTS, MAINS
EXTENDED
BURSTS
& SERVICES
ASSET LIFE
Source: WSAA/
WLR&A/Wide Bay Water
CUSTOMER BENEFITS
REDUCED
COST OF
ACTIVE
LEAKAGE
CONTROL
FEWER
FEWER
PROBLEMS ON
CUSTOMER
CUSTOMER
COMPLAINTS PLUMBING &
APPLIANCES
3 phases over 3 years, 3 reports, 10 Guidelines,
3 customised national software, 6 Case Studies
2011 IWA pressure:bursts equation
Anytow n PMZs, Changes in Service Connection Burst
Frequency due to Pressure Managem ent
Before pressure
management
Po, BFo
100
Burst frequency BF
Service burst frequency/1000 service
conns/year
120
80
60
40
20
0
0
10
20
30 40 50 60 70 80
Pmax at AZP Point (metres)
90 100
BFnpd
NPD
Linear
After pressure
management
P1, BF1
Power
Burst frequency
component that
varies wholly or
partly with
pressure
Px
Burst frequency component that is
independent of changes in pressure
UARL service conn burst frequency
Non Pressure-dependent burst frequency BFnpd if N2 = 3
•
•
•
Maximum AZP Pressure Pmax
Not two straight lines, but a power law
Burst frequency BF = BFnpd + A x PmaxN2
BFnpd = non pressure dependent burst frequency
Source: Thornton and Lambert, IWA Manila, 2012
Example: CICL mains (Sydney Water, large zones)
Substantial
reductions in
burst frequency
have been
achieved for
CICL mains
The improved 2012
prediction equation
gives better
predictions in
individual zones,
and overall
Sources: Sydney
Water, WLR&A
Brief comparison of IWA and UKWIR conclusions (2011)
Source: WLR&A study for JOAT Consulting
Assessing value of extension of asset life of AC
mains following pressure management
NPV benefit of extending mains residual life by pressure
management; Interest Rate i = 3%, Discount Rate r = 9%
NPV benefit as % of current
mains replacement cost RCo
45%
40%
Extension EP
NPV benefit as % of RCo
= 100 x KRL x (1 - KEP),
where K = (1+i%)/(1+r%)
35%
30%
10 years
8 years
25%
6 years
20%
4 years
15%
2 years
10%
1 year
5%
0%
0
5
10
15 20 25 30 35 40
Residual Life RL (years)
45
50
55
General relationship between
• existing Residual Life RL years
• extension of residual life EP
years, after pressure reduction
• Interest rate i%
• Discount rate r%
• Net Present Value benefit as %
of current replacement cost
Calculations use LAPMETCalcs
Software, WSAA PPS-3 Project
Cumulative NPV benefit in a PMZ
can be assessed for expected AC
mains replacements in future years.
This example, for AC mains in a
2500 property PMZ subject to
20 metres reduction in max.AZP
pressure, shows NPV benefits
of $256k over 25 years
Sources: WSAA, WLR&A, ILMSS, Wide Bay Water
Summary
•
burst reduction by pressure management for mains, and for services, is
now well established and predictable for individual zones
•
even small reductions of just a few metres can give significant benefits
•
zone-specific benefits and savings for mains, and for services, can be
quickly predicted using IWA best practice methods with the right data
•
extension of residual asset life is a further large benefit, and can now be
predicted for AC mains –NPV benefits on CI mains are next to be studied
•
these considerations will have major implications for asset management,
selection criteria for PMZs and DMAs, and future operation and design of
distribution systems
•
UKWIR has been slow in recognising pressure:bursts relationships, and
even now only acknowledges some of the early (2006) IWA advances
For more information, go to www.leakssuite.com in January 2013