Timothy R Gablehouse (303) 572-0050 (800) 818-0050 [email protected].
UKOPA-07-0050
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Report Number: 6957 Issue: 1.0
UKOPA PIPELINE FAULT DATABASE
Pipeline Product Loss Incidents
(1962 - 2006)
5th Report of the UKOPA Fault Database Management Group Comprising:
National Grid
BP Huntsman Shell UK E-ON UK
Wales and West Utilities Scotia Gas Networks
Northern Gas Networks Health and Safety Executive
Report prepared by G.Arunakumar Advantica for FDMG
Advantica Report Reference: 6957 August 2007
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Report Number: 6957 Issue: 1.0
Comments, questions and enquiries about this publication should be directed to the UKOPA Pipeline Fault Database Project Manager: Barry Authers Advantica Ashby Road Loughborough Leicestershire LE11 3GR e-mail: [email protected] Tel: 01509 282170
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Report Number: 6957 Issue: 1.0
Summary This report presents collaborative pipeline and product loss incident data from onshore Major Accident Hazard Pipelines (MAHPs) operated by National Grid, Scotia Gas Network, Northern Gas Network, Wales and West Utilities, Shell UK, BP, Huntsman and E-ON UK, covering operating experience up to the end of 2006. The data presented here cover reported incidents on pipelines within the public domain and not within a compound, where there was an unintentional loss of product from the pipeline. The overall failure frequency over the period 1962 to 2006 is 0.248 incidents per 1000 km.year, whilst in the previous report this figure was 0.263 incidents per 1000 km.year (covering the period from 1962 to 2004). The failure frequency over the last 5 years is 0.028 incidents per 1000 km.year, whilst in the previous report this figure was 0.028 incidents per 1000 km.year (covering the 5 year period up to the end of 2004).
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Report Number: 6957 Issue: 1.0
Contents
1 INTRODUCTION .............................................................................................................1
1.1 BACKGROUND ............................................................................................................1
1.2 PURPOSE OF THE DATABASE.....................................................................................1
1.3 KEY ADVANTAGES......................................................................................................1
2 Database Content..........................................................................................................3
2.1 PIPELINE SYSTEM DATA ............................................................................................3
2.1.1 Exposure ...................................................................................................................3
2.1.2 Transported Products ...............................................................................................4
2.2 PRODUCT LOSS INCIDENT DATA................................................................................4
2.2.1 Incident Ignition.................................................................................................5
2.2.2 Incident Frequency ............................................................................................6
2.2.3 Incident Frequency by Cause.............................................................................8
2.2.4 External Interference ......................................................................................11
2.2.5 External Corrosion ..........................................................................................14
2.2.6 Detection................................................................................................................18
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Report Number: 6957 Issue: 1.0
Page 1 of 18
1 INTRODUCTION
1.1 Background One of the key objectives of UKOPA is to develop a comprehensive view on risk assessment and risk criteria as they affect Land Use Planning aspects adjacent to high hazard pipelines. The main multiplier in pipeline risk assessments is the per unit length failure rate which directly relates to the extent of risk zones adjacent to the pipelines. Regulators and consultants who carry out risk assessments for UK pipelines have generally relied on US and European data to provide the basis for deriving failure rates due to the shortage of verified published data relating to UK pipelines. UKOPA published the first report in November 2000, presenting the first set of incident data for pipeline incidents resulting in the unintentional release of product up to the end of 1998. A full list of reports is listed in the table below.
Report Date Covering Incidents to end of
Report Number
Reference
2000 1998 1 R 4092
2002 2000 2 R 4798 2003 2002 3 R 6575
2005 2004 4 R 8099 2007 (this report) 2006 5 6597
1.2 Purpose of the Database The purpose of the database is to:
• estimate leak and pipeline rupture frequencies for UK pipelines, based directly on historical failure rate data for UK pipelines
• provide the means to estimate failure rates for UK pipelines for risk assessment purposes based on analysis of damage data for UK pipelines
• provide a more realistic and rigorous approach to the design and routing of pipelines
• provide the means to test design intentions and determine the effect of engineering changes (e.g. wall thickness of pipe, depth of burial, diameter, protection measures, inspection methods and frequencies, design factor etc).
1.3 Key Advantages
The database is designed to reflect the ways in which the UKOPA operators design, build, operate, inspect and maintain their pipeline systems. Although the pipeline and failure data are extensive, there are pipeline groups (e.g. large diameter, recently
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Report Number: 6957 Issue: 1.0
Page 2 of 18
constructed pipelines) on which no failures have occurred; however, it is unreasonable to assume that the failure frequency for these pipelines is zero. Similarly, further pipeline groups exist for which the historical failure data are not statistically significant.
Unlike its Europe-wide EGIG* counterpart, this UKOPA database contains extensive data on pipeline failures and on part-wall damage, allowing prediction of failure frequencies for pipelines for which inadequate failure data exist. Using Structural Reliability Analysis it is possible to determine the range of defect dimensions that will cause a specific pipeline to fail; analysis of the statistical distributions of actual defect dimensions from the part-wall defect data allows the probability of a critical defect to be determined and failure frequencies for any credible failure mechanism to be calculated. This approach has been used extensively and successfully by one of the contributing companies in recent pipeline uprating projects.
*European Gas Pipeline Incident Data Group (gas loss incidents in gas transmission pipelines operating above 15 bar).
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Report Number: 6957 Issue: 1.0
Page 3 of 18
2 DATABASE CONTENT
2.1 Pipeline System Data
2.1.1 Exposure
The total length of Major Accident Hazard Pipelines (MAHPs - see UK statutory legislation, The Pipelines Safety Regulations 1996 (PSR96), for their definition), above ground, below ground and elevated, in operation at the end of 2006 for all participating companies (National Grid, Scotia Gas Network, Northern Gas Network, Wales and West Utilities, BP, Shell UK, Huntsman and E-ON UK) is 21,882 km. The total exposure in the period 1952 to the end of 2006 is 700463.16 km.yr; the development of this exposure is illustrated in Figure 1. Exposure of Pipeline before first recorded incident in 1962 = 3740 km.yr (included in exposure and incident frequency calculations) Length of Pipeline which has unknown commissioning date = 46.0 km. (This has been ignored in the exposure calculations) Exposure to end 2006 of Elevated Pipeline = 25.8.0 km.yr (included in totals) Exposure to end 2006 of Above Ground Pipeline = 142.0 km.yr (included in totals)
Development of Pipeline Exposure
0
100000
200000
300000
400000
500000
600000
700000
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Year
Cu
mu
lati
ve E
xp
osu
re k
m.y
r
Figure 1
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2.1.2 Transported Products
The lengths of pipeline in operation at the end of 2006, by transported product, are (in km):
Butane 19.5 Hydrogen 14.14
Condensate 24.0 LPG 9.94
Crude Oil (Spiked) 212.6 Natural Gas (Dry) 20134.53
Ethane 38.1 Other 225.8
Ethylene 1141 Propane 19.5
Gasoline 6.5 Propylene 36.3
TOTAL PIPELINE LENGTH 21881.85
2.2 Product Loss Incident Data A product loss incident is defined in the context of this report as:
• an unintentional loss of product from the pipeline
• within the public domain and outside the fences of installations
• excluding associated equipment (e.g. valves, compressors) or parts other than the pipeline itself
A total of 174 product loss incidents were recorded over the period between 1962 and 2006. No product loss incidents were recorded prior to 1962. An annual breakdown of incidents is illustrated in Figure 2a. The cumulative number of incidents over the period 1962 to 2006 is shown in Figure 2b.
Annual Number of Product Loss Incidents
0
2
4
6
8
10
12
14
16
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
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1975
1976
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1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Year
Nu
mb
er
of
Incid
en
ts
Figure 2a
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Report Number: 6957 Issue: 1.0
Page 5 of 18
Differences between 2004 and 2006 product loss statistics
There was one product loss incident recorded during the year 2006.
Total Number of Product Loss Incidents (Cumulative)
0
20
40
60
80
100
120
140
160
180
200
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
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1980
1981
1982
1983
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1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Year
Nu
mb
er
of
Incid
en
ts
Figure 2b
2.2.1 Incident Ignition
There were 9 out of 174 (5.2%) product loss incidents that resulted in ignition. Table 1 below provides more detail:
Affected Component Cause Of Fault Hole Diameter Class
Pipe Seam Weld Defect 0-6 mm
Pipe Ground Movement Full Bore and Above (18” Diameter Pipe)
Pipe Girth Weld Defect 6-20 mm Pipe Unknown 6-20 mm Pipe Pipe Defect 0 – 6 mm Pipe Unknown 40 – 110 mm Pipe Lightning Strike 0-6 mm
Bend Internal Corrosion 0-6 mm Bend Pipe Defect 6-20 mm
Table 1 – Incidents that Resulted in Ignition
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Report Number: 6957 Issue: 1.0
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2.2.2 Incident Frequency
The incident frequency over eight consecutive 5-year periods up to the end of 2006 is shown in Table 2.
Period Number of Incidents
Total Exposure [km.yr]
Frequency [Incidents per 1000
km.yr]
1967 - 1971 29 41.104 0.706
1972 - 1976 19 66.139 0.287
1977 – 1981 28 80.241 0.349
1982 - 1986 43 88.883 0.484
1987 - 1991 27 94.150 0.287
1992 - 1996 7 100.878 0.069
1997 - 2001 11 104.195 0.106
2002 - 2006 3 108.836 0.028
Table 2 The overall incident frequency by hole size over the period 1962 - 2006 is shown in Table 3.
Hole Size Class Number of Incidents Frequency [Incidents per 1000 km.yr]
Full Bore* and Above 7 0.010 110mm – Full Bore* 3 0.004
40mm – 110mm 7 0.010 20mm – 40mm 21 0.031
6mm – 20mm 27 0.040 0 – 6mm 107 0.158
Table 3
* Full Bore ≡ diameter of pipeline Note that in addition to the incidents shown in Table 3 above, there are 2 incidents of unknown hole size.
The failure frequency over the last 5 years (2002-2006) is 0.028 incidents per 1000 km.yr as compared to the failure frequency during the period 1962-2006 which is 0.248 incidents per year per 1000 km.yr. An overview of the development of this failure frequency over the period 1962 to 2006 is shown in Figure 3.
In order to see the results over recent periods, without influence of the past, the moving average for each year is calculated with reference to the incidents from the previous 5 years (2002-2006, 2001-2005, 2000-2004 etc).
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Report Number: 6957 Issue: 1.0
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Development of Overall Incident Frequency
0
0.2
0.4
0.6
0.8
1
1.2
1.4
19
62
19
63
19
64
19
65
19
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19
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00
20
01
20
02
20
03
20
04
20
05
20
06
Year
Fre
qu
en
cy
per
10
00 k
m.y
r Overall Average up to Year
Moving 5-year Average
Figure 3
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2.2.3 Incident Frequency by Cause
The development of product loss incident frequency by cause is shown in Figure 4.
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
0.5
196
2
196
4
196
6
196
8
197
0
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4
200
6
Year
Fre
qu
en
cy p
er
100
0 k
m.y
r
External Corrosion External InterferenceGround Movement Internal CorrosionGirth Weld Defect OtherPipe Defect Seam Weld DefectUnknown
Figure 4
Cause = ‘Other’:
Table 4 – Product Loss Incidents by Cause
Product Loss Cause
No. of Incidents
Girth Weld Defect 33 External Interference 38 Internal Corrosion 2 External Corrosion 32
Unknown 8 Other 40 Pipe Defect 13 Ground Movement 5 Seam Weld Defect 3 Total 174
Other Cause Incidents
Internal cracking due to wet town gas 30
Pipe-Fitting Welds 4
Leaking Clamps 2
Lightning 1
Soil stress 1
Threaded Joint 1
Electric Cable Arc Strike 1
Total 40
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Report Number: 6957 Issue: 1.0
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Figure 5 shows the product loss incident frequency by cause over the period 1962-2006 compared with the frequency over only the last 5 years (2002-2006).
Historical and Recent Failure Frequencies
0
0.01
0.02
0.03
0.04
0.05
0.06
Exter
nal C
orrosi
on
Exter
nal In
terfer
ence
Gro
und Move
men
t
Inte
rnal
Corr
osion
Girt
h Wel
d Def
ect
Oth
er
Pipe
Def
ect
Seam
Wel
d Def
ect
Unkn
own
Cause
Fre
qu
en
cy p
er
100
0 k
m.y
r
1962 to 2006
2002 to 2006
Figure 5
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Report Number: 6957 Issue: 1.0
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An overview of the product loss incident frequency by cause and size of leak in the period 1962 to 2006 is shown in Figure 6.
Product Loss Incidents by Cause and Equivalent Hole Diameter
0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
Exter
nal C
orrosi
on
Exter
nal In
terfer
ence
Girt
h Wel
d Def
ect
Gro
und Move
men
t
Inte
rnal
Corr
osion
Const
ruct
ion/M
ater
ial
Oth
er/U
nknow
n
Cause
Fre
qu
en
cy
pe
r 1
000
km
.yr
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Construction/Material = Seam Weld Defect + Pipe Defect + Pipe Mill Defect + Damage During Original Construction
Figure 6
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Report Number: 6957 Issue: 1.0
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2.2.4 External Interference
Figure 6 shows that external interference is one of the main causes of product loss incident data.
2.2.4.1 External Interference by Diameter Class
Figure 7 shows the product loss incident frequencies associated with external interference by diameter class and by hole size.
Product Loss Incidents Caused by External Interference
Frequency by Pipe Diameter and Equivalent Hole Diameter
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
0 - 4 5 - 10 12 - 16 18 - 22 24 - 28 30 - 34 36 - 48
Diameter Class (inches)
Fre
qu
en
cy p
er
10
00 k
m.y
r
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 7
Diameter inches
Exposure km.yr Incidents
Frequency /1000km.yr
0-4 35996 5 0.139
5-10 147342 17 0.115
12-16 120225 9 0.075
18-22 105083 3 0.029
24-28 113585 3 0.026
30-34 33948 1 0.029
36-48 144285 0 0.000
Total 700463 38 0.054
Table 5 – Exposure by Diameter Class
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2.2.4.2 External Interference by Measured Wall Thickness Class
The relationship between product loss incidents caused by third party interference and wall thickness is shown in Figure 8.
Product Loss Incidents Caused by External Interference
Frequency by Wall Thickness and Equivalent Hole Diameter
0.00
0.05
0.10
0.15
0.20
0.25
0.30
<5 5 - 10 10 - 15 >15
Wall Thickness Class (mm)
Fre
qu
en
cy p
er
1000
km
.yr
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Note: Largest wall thickness for loss of product incident caused by external interference to date is 12.7mm.
Figure 8
Wall Thickness
mm Exposure
km.yr Incidents Frequency /1000 km.yr
<5 53099 12 0.226
5-10 340779 22 0.065
10-15 261400 4 0.015
>15 45185 0 0.000
Total 700463 38 0.054
Table 6 – Exposure by Wall Thickness Class
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2.2.4.3 External Interference by Area Classification
Product Loss Incidents Caused by External Interference
Frequency by Area Classification and Equivalent Hole Diameter
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Rural Suburban + Semi-Rural Urban
Area Classification
Fre
qu
en
cy p
er
100
0 k
m.y
r
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 9
Area Classification Exposure km.yr Incidents Frequency /1000 km.yr
Rural 597744 28 0.047
Suburban + Semi-Rural 64636 10 0.155
Urban 771 0 0.000
Total 663151 38 0.057
Table 7 – Exposure by Area Classification in km.yr
Note: Rural = population density < 2.5 persons per hectare Suburban and Semi-rural = population density > 2.5 persons per hectare and which may be extensively developed with residential properties Urban = Central areas of towns or cities with a high population density
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2.2.5 External Corrosion
2.2.5.1 External Corrosion by Wall Thickness Class
Product Loss Incidents Caused by External Corrosion
Frequency by Wall Thickness and Equivalent Hole Diameter
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
<5 5 - 10 10 - 15 >15
Wall Thickness Class (mm)
Fre
qu
en
cy
pe
r 1
000
km
.yr
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 10
Wall Thickness (mm) Exposure km.yr Incidents Frequency /1000 km.yr
<5 53099 16 0.301
5-10 340779 16 0.047
10-15 261400 0 0.000
>15 45185 0 0.000
Total 700463 32 0.046
Table 8 – Exposure by Wall Thickness Class
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2.2.5.2 External Corrosion by Year of Construction
Product Loss Incidents Caused by External Corrosion
Frequency by Year of Construction and Equivalent Hole Diameter
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Pre-1971 1972-1981 1982-1991 1992-2001 2002-2006
Year of Construction
Fre
qu
en
cy p
er
100
0 k
m.y
r
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 11
Construction Year
Exposure km.yr Incidents
Frequency /1000 km.yr
Pre-1971 481398 31 0.064
1972-1981 149117 1 0.007
1982-1991 44535 0 0.000
1992-2001 23655 0 0.000
2002-2006 1758 0 0.000
Total 700463 32 0.046
Table 9 – Exposure by Year of Construction
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2.2.5.3 External Corrosion by External Coating Type
Product Loss Incidents Caused by External Corrosion
Frequency by External Coating Type and Equivalent Hole Diameter
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
Bitu
men
Coal
Tar
Polyet
hylen
eFB
E
Oth
er/U
nknow
n
External Coating Type
Fre
qu
en
cy p
er
10
00 k
m.y
r
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 12
External Coating Exposure km.yr Incidents Frequency /1000
km.yr
Bitumen 31572 3 0.095
Coal Tar 543174 21 0.039
Polyethylene 46286 3 0.065
FBE 57964 0 0.000
Other/Unknown 30850 5 0.162
Total 709846 32 0.045
Table 10 – Exposure by External Coating Type
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2.2.5.4 External Corrosion by Type of Backfill
Product Loss Incidents Caused by External Corrosion
Frequency by Backfill Type and Equivalent Hole Diameter
0
5
10
15
20
25
30
35
40
Clay Gravel Heavy Soil Peat Sand Other
Backfill Type
% o
f to
tal In
cid
en
ts
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 13
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2.2.6 Detection
Detection of Product Loss Incidents by Equivalent Hole Diameter
0
5
10
15
20
25
30
35
40
Cip
s/Pea
rson
Gro
und Pat
rol
Landow
nerO
LI
Leak
Det
ectio
n
Police
Public
Site C
ontrac
tor
Oth
er/U
nknow
n
Detection Method
% o
f to
tal
Inc
ide
nts
0 - 6 mm
6 - 20 mm
20 - 40 mm
40 - 110 mm
110 mm - Full Bore
Full Bore and Above
Figure 14
Note: Leak detection and On-Line Inspection (OLI) are not applicable to all pipelines.