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ST-T
AL
KS
: AS
SE
T M
AN
AG
EM
EN
T S
ER
IES
IN ASSOCIATION WITH
Pipeline Assets -Replacement and Augmentation Drivers -Risk
Based Inspection Approach
Aubrey Nxumalo (Pr.Eng)
26 June 2020
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ST-T
AL
KS
: A
SS
ET
MA
NA
GE
ME
NT
SE
RIE
S
• OVERVIEW: Bulk Water Pipeline
Network
• ASSET MANAGEMENT: Life Cycle
Management
• AUGMENTATION: Supply and Demand
Trends
• OVERVIEW: Bulk Water Pipeline Network
• LIFE CYCLE MANAGEMENT: End-of-Life
Triggers
• CAPACITY ASSESSMENT: Augmentation
• CONDITION ASSESSMENT: Renewal
• RBI: External Corrosion Direct Assessment
• ENGINEERING EVALUATION
• RISK ASSESSMENT
• RENEWAL TECHNIQUES
CONTENT
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OVERVIEW: Bulk Water Pipeline Network
Tshwane
Mp
um
alan
ga
Vaal River System
3500km bulk water Pipeline Network in Gauteng Steel pipelines ̴
94% and Pre-stressed Concrete Pipelines ̴ 6% The diameter and
pressure ranges :600mm to 3500mm and
5bar to 35bar respectively
The expected useful life of a pipeline depending largely on
material of construction. 65 -75 years - steel pipeline and 40 - 45
years – PCP
Estimated Asset Values Carrying Value :R 7,44billion Replacement
Value :R 75billion
0
1000
2000
3000
4000
65yrs 100+ Total Km
670
2060
520250
3500
KM
PER
AG
E P
RO
FILE
AGE PROFILE
RW BULK WATER PIPELINE AGE PROFILE: 2018
Sedibeng
West Rand
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ASSET LIFE CYCLE MANAGEMENT: End-of-Life Triggers
1.Renewal and augmentation is driven by the end-of-life
triggers.
Pre-Mature Failure Event
Point of initial degradation
Point of failure detection
Point of Functional Failure =
over 3% RAV
Maintenance Cost
2.The life cycle of an asset can be represented on a lifecycle
curve (condition over time) and bath tub curve (cost over time)
End of
Physical Life
Asset is physically
non-functioning or
become significantly
unreliable due to
overall poor
condition and/or
major/frequent
failures - Renewal
End of
Service Level Life
Asset can no longer
functionally achieve
what is expected of it
due to a significant
change in output
requirements
(excluding increased
volumetric water
demand) and/or a
change in incoming
conditions – for
example more
stringent turbidity
specifications for a
filter house, or higher
required chemical
dosages due to
deteriorating raw
water quality -
Internal factors –
Augmentation
End of
Supply Level Life
Asset’s volumetric
water demand
exceeds the
designed capacity
normally triggered
from a planning
perspective
(increased consumer
demand) -
External factors -
Augmentation
End of
Economic Life
Asset’s
recoverable value
is significantly less
than the carrying
value resulting in
substantial -
Impairment loss -
Renewal
“Cause and Effect”
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CAPACITY ASSESSMENT: Augmentation Strategy
SUPPLY & DEMAND TRENDS ARE THE MAIN DRIVERS FOR AUGMENTATION
1.In order to better forecast the impact of supply and demand
factors, the following key trends are considered:
Social trends
• Household size and population growth• Lifestyle issues and
preferences• Travel and improved mobility
Economic trends Environmental trends Technological trends
Advances in technology generally lead to more efficient and cost
effective service delivery, as well as alternativeservice
offerings.
global warming and the depletion of scarce natural
resources.
• Economic investment• Economic structuring, i.e.
corporatization, and workforce mobility
2.The demand profile dictates the nature, location, and extent
of futureinfrastructure Augmentation
700
800
900
1 000
1 100
1 200
1 300
1 400
1 500
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15
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35
20
36
AADD
PDD
System Capacity
Year
Dem
and
(M
l/d
)
Year
Dem
and
(M
l/d
)
Ass
et A
ugm
enta
tio
n.
A
Syst
em A
ugm
enta
tio
n: P
lan
t Le
vel.
Ass
et A
ugm
enta
tio
n.
Demand Profile Curve
Ass
et A
ugm
enta
tio
n.
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CONDITION ASSESSMENT: Renewal StrategyRISK BASED INSPECTION
FRAMEWORK:ECDA
Acoustic
Blockage
Pipe Condition
Pipe Wall DefectDetailed
Pipe Profiling
Insp
ecti
on
Re
so
luti
on
Relative Cost
HIGH
LOW
HIGHLOW
ZoomCamera
Manhole Inspection
No Contact with Flow: Contact with Flow:
Wastewater PipeCondition AssessmentApplications
Push Camera
CCTV
Overland
Pre Inspection
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1.Pipelines are long line static assets and exposed to different
ground condition along their entire length
2.It is important to conduct pipeline condition assessment to
predict failure mode and Risk exposure in different segments of the
servitude
3.The most common mode of failure is electrochemical
corrosion
CONDITION ASSESSMENT
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EXTERNAL CORROSION DIRECT ASSESSMENT: Indirect Inspection
External Corrosion Direct
Assessment is a four step process that combines different
techniques:
Pre-visual Inspection along the pipeline route
Indirect inspection using basic overland tools Soil Resistivity
(DCVG, CIPS,) Stray current Monitoring
Direct examination using advanced tool (GUL, C-SCAN) and
Engineering Evaluation computer added tools (PIMS, GIS)
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External Corrosion Direct Assessment: Indirect inspection
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Tim
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10
:29
:00
Po
ten
tial
(V)
Time
Pipe Next to Railway Line
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Engineering Evaluation
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Risk Assessment: Direct Inspection
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Pipe Renewal Techniques
Pipe Renewal
Once the pipe’s condition and performance is assessed, suitable
renewal technologies can be applied to improve the pipe’s
condition. Pipe renewal can be divided into three components:
Pipe Repair – wooden plug and/or coupling or metal sheet
Pipe Rehabilitation – Cured-In-Place Pipe lining or Close-fit
Liner or Grout-in-place Liner
Pipe Replacement – New steel pipe
These three components of renewal vary with the pipe condition
and the functions performed is explained in the following.
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Thank You for your time !!!
