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8/13/2019 University of NewCastle- Pipeline Risk
1/19
Universityof
NewcastleuponTyne
Pipelines Safety - Risk Quantification
This lecture will cover the following aspects:-
MSc in Pipelines Engineering
How are pipeline failure risks quantified?
What pipeline databases exist for failure rates?
What are typical failure rates for pipelines
How is Consequence Analysis carried out?
Which Risk Criteria are applied for pipelines?
UniversityofNewcastleuponTyne
How are pipeline failure risks quantified?Risk Assessment Studies
Risk Tolerability
- i s i t OK?
- how bad?
Consequence Analysis
- how often?
Frequency Analysis
- what can happen?
Hazard Identification
Incident Data - Historical
Fault data - extrapolation
Predictive Modelling, FractureMechanics
Release - leak rate, rain out
Dispersion
Effects
External Impact, Corrosion
Mechanical defect, Natural
Other, Rupture, Puncture, Pinhole
Gas jet / plume
Pool Evaporation
Wind/ Weather
Individual Risk / Transects/ Societal Risk
Criteria / Land Use Planning Zones
Fire Radiation
Explosion Overpressure
Toxic Effects
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
How are pipeline failure risks quantified?
Usual measure is
frequency of specific incidentsuch as pinhole or puncture or rupture
Per 1000 kilometres per year ( per km.yrs)
which is equivalent to
Per metre per million years ( x 10-6 per year)
or
Per kilometre per thousand years ( x 10-3 per year)
UniversityofNewcastleuponTyne
s What pipeline databases exist for failure rates?
1 European Gas Pipeline Incident Data Group
(EGIG)
Objectives
To demonstrate the high safety level of European gas transmissionpipelines
To provide non-EGIG members with the best available failure dataon gas pipeline incidents
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
Objectives
To demonstrate the high safety level of Europe
an gas transmission pipelines
To provide non-EGIG members with the best
available failure data on gas pipeline incidents
Scope
Only pipeline incidents with an unintentional
gas release
Only onshore gas transmission pipelines
steel pipelines
design pressure > 15 bar
outside fences of installations
excluding associated equipment(e.g. valves, compressors) or parts other
than the pipeline itself
European Gas Pipeline Incident Data Group
UniversityofNewcastleuponTyne
Participants
Dansk Gasteknisk Center a/s represented by
DONG (Denmark)
ENAGAS, S.A. (Spain)
Gaz de France (France)
N.V. Nederlandse Gasunie (The Netherlands)Ruhrgas AG (Germany)
Distrigas n.v. (Belgium)
SNAM S.p.A. (Italy)
SWISSGAS (Switzerland)
Transco (part of BG), represented by
BG Technology (England)
European Gas Pipeline Incident Data Group
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
An extensive analysis on collected information has lead to thefollowing results:
Over the period 1970 - 1998 there has been no fatal accidentinvolving inhabitants.
The overall incident frequency with an unintentional gas release overthe period 1970 to 1998 is 0,480 incidents per year per 1000 km pipeline.However, the figure over the past 5 years is significantly lower:0,211 incidents per year per 1000 km pipeline.
External interference remains the main cause of gas pipeline incidentsinvolving gas leakage; an average of 0,239 incidents per year per1000 km pipeline for the period 1970 to 1998.
An improvement in the incident frequency has been observed inrecent years; over the past 5 years the figure is 0,087 incidents per yearper 1000 km pipeline.
For the incident causes 'corrosion' and 'construction defects/material failures no ageing could be demonstrated.
Summary 4th EGIG report 1999
UniversityofNewcastleuponTyne
EGIG - Failure frequency trend 1970-98
8/13/2019 University of NewCastle- Pipeline Risk
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2 CONCAWE - the oil companies study groupfor Conservation of Clean Air and Water - Europe
UniversityofNewcastleuponTyne
The latest in a series of annual issues, this report reviews the performance in
2000 of 30,870 km of on-shore oil pipelines in Western Europe with regards tohydrocarbon spillage. Incidents are analysed by cause and the effectivenessof the clean-up is recorded. Direct repair and clean-up costs are reported.
Performance in 2000 was markedly better than the long-term average,third party activities remaining the main cause of spillage incidents.
The report also gives the annual pigging inspection statistics.Some 3000 km of pipeline were internally inspected in 2000.
75% of the pipeline inventory has now been inspected with such tools.
Performance of cross-country oil pipelines in Western Europe
Statistical summary of reported spillages 2000
CONCAWE Database
8/13/2019 University of NewCastle- Pipeline Risk
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NewcastleuponTyne
Sixty-six companies and other bodies operating oil pipelines inWestern Europe currently provide statistics for the CONCAWE
annual report on the performance of cross-country oil pipelines.
These organisations operate some 250 different service pipelineswhich at the end of 2000 had a combined length of 30,780 km,an increase of 860 km since 1999.
Volume transported in 2000 was 672 Mm3 of crude oil and refinedproducts, which is 1.5 Mm3 less than in 1999.
Total traffic volume in 2000 amounted to 126 x 109 m3 x km,1% higher than in 1999.There were 6 reported oil spillages from pipelines during 2000
(12.6 per year on average since 1971).There were no associated fires or injuries.
The net oil loss into the environment amounted to 84 m3,equivalent to 0.1 parts per million (ppm) of the total volume transported.
The gross spillage was 360 m3, which is 0.5 ppm.A total of 276 m3, i.e., 77% of the spillage was recovered.
CONCAWE Database
UniversityofNewcastleuponTyne
The causes of the oil spillages are attributed to:
? Mechanical failure 1 incident
? Operational 0 incidents
? Corrosion 1 incident
? Natural hazard 0 incidents
? Third party activity 4 incidents
CONCAWE Database
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NewcastleuponTyne
CONCAWE Database
UniversityofNewcastleuponTyne
CONCAWE Database
Typical failure rate data for Crude Oil pipelines < 202 mm diameter:-
Pinhole Puncture Rupture Total
Third party 0.313 0.537 0.359 1.209
Mechanical 0.106 0.091 0.106 0.303
Natural 0.003 0.073 0.227 0.303
Total 0.412 0.701 0.692 1.815
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
UKOPA Database
for UK Gas Pipeline Data
Pipeline and product loss incident data from onshore Major Accident
Hazard Pipelines (MAHPs) operated by Transco, Shell UK, BP, Huntsman
and Powergen UK, covering operating experience up to the end of 2000.
United Kingdom Onshore Pipelines
Operators Association 14 major UK pipeline operators
includes gas and oil pipelines operators
covered by Pipelines Safety Regulations 1996
5 Companies have pooled Fault and Leak
Data covering 96% of Major Accident Hazard
Gas and Liquid Pipelines in the UK
UniversityofNewcastleuponTyne
The overall failure frequency overthe period 1961 to 2000 is 0.289incidents per 1000 km.year.
The failure frequency over the last 5 years is 0.093incidents per 1000 km.year.
A further report will cover predicted failurefrequencies based on models of the growth ofpart-wall defects where no product loss hasoccurred, in order to provide failure frequencies
for pipeline groups where historical failure dataare sparse.
UKOPA Database
for UK Gas Pipeline Data
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
Butane 19.5 Propylene 36.3CO 36.3 LPG 9.6
Condensate 24.0 Natural Gas (Dry) 19,947.7Crude Oil (Spiked) 212.6 Other 318.3
Ethane 38.1 Propane 19.5
Ethylene 1,198.5 TOTAL 21,860
Period Number of
Incidents
Total
Exposure[km.yr]
Frequency
[Incidents per 1000km.yr]961 - 1965 6 10,261 0.585966 - 1970 21 35,115 0.598971 - 1975 25 65,411 0.382
976 - 1980 27 80,322 0.336981 - 1985 40 90,497 0.442986 - 1990 33 96,728 0.341991 - 1995 9 103,672 0.087996 - 2000 10 107,508 0.093
Hole SizeClass
Number ofIncidents
Frequency[Incidents per 1000
km.yr]
Full Bore* 7 0.012
50mm 16 0.02720mm 36 0.061
6mm 63 0.106
0 Full Bore 171 0.289
UKOPA Database
for UK GasPipeline Data
UniversityofNewcastleuponTyne
UKOPA Database
for UK Gas Pipeline Data
Development of Overall Incident Frequency
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1962
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
Year
Frequencyper1000km.yr Overall Average up to Year
Moving 5-year Average
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Universityof
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Development of Incident Frequency by Cause
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
19
60
19
62
19
64
19
66
19
68
19
70
19
72
19
74
19
76
19
78
19
80
19
82
19
84
19
86
19
88
19
90
19
92
19
94
19
96
19
98
20
00
Year
Frequencyper1000km.yr
External Corrosion External InterferenceGround Movement Internal CorrosionGirth Weld Defect Other Pipe Defect Seam Weld DefectUnknown
UKOPA Database
for UK Gas Pipeline Data
UniversityofNewcastleuponTyne
Historical and Recent Failure Frequencies
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Extern
alCorrosion
ExternalIn
terference
Ground
Movem
ent
Intern
alCo
rrosio
n
GirthWe
ldDefe
ct Other
PipeD
efect
Seam
Weld
Defect
Unkn
own
Cause
Frequency
per1000km.yr
1960-2000
1996-2000
UKOPA Database
for UK Gas Pipeline Data
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NewcastleuponTyne
Product Loss Incidents Caused by External Interference
Frequency by Wall Thickness and Hole Equiv. Diameter
0
0.05
0.1
0.15
0.2
0.25
0.3
15Wall Thickness Class (mm)
Frequencyper1000km.yr
0 - 6
6 - 20
20 - 50
50+
Full Bore
UKOPA Database
for UK Gas Pipeline Data
UniversityofNewcastleuponTyne
Assimilate failure rate data into diameter ranges:-
Diameter
range mm
EGIG 1000-km-
year
BG 1000-km-year
0-100 0.719 0.239
125-250 0.429 0.168300-400 0.163 0.086
450-550 0.067 0.046
600-700 0.027 0.025750-850 0.011 0.014
900-1000 0.005 0.0071000+ 0.002 0.005
Adjust failure rate for mitigation factors:-
Depth of cover Normalised Failure Reduction
(Inflation) factor1.22 m 0.7
s What are typical failure rates for pipelines
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
Pipeline Location Normalised Failure Reduction
(Inflation) factorRural 1.0
Suburban 3.9Town 23.1
Mitigation measure Normalised FailureReduction (Inflation)
factorMarker posts 1.0
All other measuresSlabbing, concreteetc (under review)
0.9
Diameter Min wall
thickness
Normalised wall thickness failure frequency factor
4.8,
6.4,7.99.5
1504509001050 12.7 XXX XXX XXX XXX XXX
UniversityofNewcastleuponTyne
What do you do if no failures have
occurred for a pipeline diameter range?
- use Predictive Models
1 Linear regression Analysis - EGIG Data
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
Linear Regression Analysis
Log to base 10 of failure frequency
Diameter midpoints as X- values
Parameters calculated for known datasets giving
Y = MX + C equation = -0.00258X + 0.11456
UniversityofNewcastleuponTyne
Linear Regression Analysis
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Universityof
NewcastleuponTyne
Alternatively, Use Fault Data to predict
Failure Rate
UKOPA Fault Database
Structural Reliability Analysis combines theoretical and
empirical structural mechanics with uncertainty analysisof structural parameters in order to determine failure
probabilities
Uses parameters for which statistically significant numbers of
measured values are often available (e.g. wall thickness and
yield strength) in predictive models (limit state functions) in
order to predict the uncertainty in parameters for which
statistically significant databases are unavailable
(e.g. leak & rupture incidents).
UniversityofNewcastleuponTyne
Assess Zones affected by each failure:
- pinhole - small area - ignored
- puncture
- rupture - most significant affect
Consequence Analysis carried out for
- fireball - circular area affected by thermal radiation
from fireball formed by up to 30 seconds
release from the ruptured pipeline
- flammable fluid - ignition / no ignition probability
How is Consequence Analysis carried out?
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
- flash fire - directional ellipse area affected
Complex geometric calculation to
assess probability of being affected
at a specific distance from the pipeline
- jet fire - directional dependent of whether jet is
free and unobstructed or there is
interference with crater
- often modelled as worst-case circular effect
- explosion - directional dependent on source of
overpressure and location of source of
ignition
- not usually modelled for Natural gas
Probabilities of each OUTCOME calculated from an
EVENT TREE:-
UniversityofNewcastleuponTyne
MISHAP Event Tree for Gas Release
Immediate Release Delayed Delayed
Ignition Obstructed Local Remote Ignition Ignition
0.25 Yes Fireball+jetfire
0.2 0.2
0.8 Daytime
0.75 No 0.5 Yes 0.25 Yes Jetfire
Gas Release 0.6 0.3 0.075 0.075
0.75 No No ignition
0.225 0.225
0.5 No 0.25 Yes Jetfire
0.3 0.075 0.075
0 .75 No 0.1 Yes Flahfire+jetfire
0.225 0.0225 0.0225
0.9 No No ign ition
0.2025 0.2025
0.25 Yes Fireball+jetfire
0.05 0.05
0.2 Nightime
0.75 No 0.5 Yes 0.25 Yes Jetfire
0.15 0.075 0.01875 0.01875
TOTALS0.75 No No ignition
Fireball + jetfire 0.25 0.05625 0.05625
Jetfire 0.1875
Flashfire + jetfir 0.0281 0.5 No 0.25 Yes Jetfire
No Ignition 0.5344 0.075 0.01875 0.01875
total 10. 75 No 0.1 Yes Flahfire+jetfire
0.05625 0.0056 0.005625
0.9 No No ign ition
0.0506 0.050625
8/13/2019 University of NewCastle- Pipeline Risk
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Universityof
NewcastleuponTyne
Important to calculate the length of pipeline
which can affect someone at various distances
from a pipeline:-
Interaction distance = 2 x radius of circle= length of pipeline which could affect you
Pipeline
Fireball
If you are standing here
Interaction
distance
If you are standing here
Interaction
distance
Fireball RR
D
Int Dist
Interaction distance = 2 x (R2-D2)
UniversityofNewcastleuponTyne
Risk = frequency of rupture incidents / metre per 10-6 years
x number of metres of pipeline which can affect individual
(interaction distance)
= effect per 10-6 years
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Universityof
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Frequency and Consequences of each event
are assessed to give the RISK TRANSECT:-
Risk
Pipeline
50 100 150 200200 150 100 50
FireballFlashfire
Jetfire
Total
Risk
UniversityofNewcastleuponTyne
Typical Risk Transect from IG/TD/1
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innerzon
e
inner zone
- no housing at all allowed
- calculated from fireball radius full bore rupture
(NOT risk based)
- typically 85 metres for 10.75 " (270mm) 100 bar
ethylene pipeline
Risk Criteria - Land Use Planning
UniversityofNewcastleuponTyne
middlezo
ne pipeline
middle zone
- only a small increase in population allowed
- calculated from risk to 1 in a million (10-6 per year)
- typically 240 metres for 10.75 " (270mm) 100 bar
ethylene pipeline
Risk Criteria - Land Use Planning
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Universityof
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outerz
one
pipeline
outer zone
- no vulnerable population allowed
- calculated from risk to 0.3 in a million (3 X 10-7 per year
- typically 320 metres for 10.75 " (270mm) 100 bar
Risk Criteria - Land Use Planning
UniversityofNewcastleuponTyne
Typical Societal
Risk Curve from
IG/TD/1