The analysis results of long-distance oil and gas pipeline failures are important for the industry and can be the basis of risk analysis, integrity assessment, and management improvement for pipeline operators. Through analysis and comparison of the statistical results of the United States, Europe, the UK, and PetroChina in pipeline failure frequencies, causes, consequences, similarities, and differences of pipeline management, focusing points and management effectiveness are given. Suggestions on long-distance pipeline safety technology and management in China are proposed.
It is important to maintain high-pressure oil and gas pipeline systems safety and reliability, because the products are hazardous and may result in fire, explosion, and poisoning and lead to significant economic losses, casualties, and environmental pollution [
Statistical results of the US, Europe, the UK, and PetroChina in pipeline failure frequencies, causes, and consequences are comparatively analyzed. Similarities and differences of pipeline management are given. Suggestions on long-distance pipeline safety technology and management in China are proposed.
Failure statistical results of PHMSA in the US [
Mediums included in the statistical data.
NO. | Organization/Company | Pipeline Medium | ||
---|---|---|---|---|
Crude Oil | Product Oil | Natural Gas | ||
1 | PHMSA | ✓ | ✓ | ✓ |
2 | EGIG | ✓ | ||
3 | UKOPA | ✓ | ||
4 | PNGPC | ✓ | ✓ | ✓ |
Failure data of all pipelines in the US is updated to show the recent 20 years’ statistical results and detailed information by PHMSA. Significant incidents of onshore pipelines (for liquid, only crude oil and refined and/or petroleum product are involved; for gas, only transmission line is involved) are filtered from the database and calculated for the failure frequencies in this paper. Significant incidents are those including any of the following conditions: Fatality or injury requiring in-patient hospitalization. $50,000 or more in total costs, measured in 1984 dollars. Highly volatile liquid releases of 5 barrels or more or other liquid releases of 50 barrels or more. Liquid releases resulting in an unintentional fire or explosion.
Figure
Mileage and failure frequency for oil pipelines.
Mileage and failure frequency for gas pipelines.
Based on the statistical results from 2010 to 2015, which includes 432 oil pipeline failures and 238 gas pipeline failures, all of which are flagged as significant incidents in the database, the top 3 causes for oil pipeline failures are corrosion, pipe/weld material failure, and equipment failure, while those of gas pipeline failures are pipe/weld material failure, excavation damag, and corrosion (see Figures
Oil pipelines causes.
Gas pipelines causes.
Table
Causes and sub-cause categried by PHMSA.
NO. | Causes | Sub-causes |
---|---|---|
1 | Corrosion | |
External Corrosion | Galvanic Corrosion, Stray Corrosion, Microbiological Corrosion, Selective Seam Corrosion, … | |
Internal Corrosion | Corrosive Commodity, Acid Water, Microbiological Corrosion, Erosion, … | |
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||
2 | Pipe/Weld Material Failure | |
Construction, Installation or Fabrication Related | Weld Quality, Mechanical Damage in the Field, … | |
Original Manufacturing Related | Weld Quality, Manufacturing Defect, … | |
Environmental Related | Stress Corrosion Cracking, Deformation Related Cracking, … | |
|
||
3 | Excavation Damage | |
Operator’s Contractor (Second Party) | Excavation Practices not Sufficient, Locating Practices not Sufficient, Previous Damage, … | |
Third Party | Excavation Practices not Sufficient, Locating Practices not Sufficient, One-call Notification Practices not Sufficient, One-call Notification Center Error, … | |
Previous Damage due to Excavation Activity | One-call Notification Practices not Sufficient, Previous Damage, … | |
|
||
4 | Natural Force Damage | Earth Movement, Heavy Rains/Floods, Lighting, Temperature, … |
|
||
5 | Incorrect Operation | Damage by Operator or Operator’s Contractor, Pipeline or Equipment Overpressure, Equipment not Installed Properly, … |
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||
6 | Other Outside Force Damage | Damage by Cars, Boats, Nearby Industry or Fire/Explosion, … |
During 2004 to 2015, numbers of casualties and property loss caused by pipeline accidents in the US did not vary significantly, except the peak value in 2010 (see Figure
Failure consequences in the US reported by PHMSA.
The property loss includes estimated cost of public and nonoperator private property damage, product released intentionally or unintentionally, operator’s property damage and repairs, operator’s emergency response, and environmental remediation.
Up to 2013, the total length of EGIG gas pipeline becomes 144 kkm. The objective of EGIG is to collect and present data on loss of gas incidents in order to present the safety performance of the European gas transmission network to the general public and authorities.
The required criteria for an incident to be recorded in the EGIG database are the following: The incident must lead to an unintentional gas release. The pipeline must fulfil the following conditions: to be made of steel, to be onshore, to have a maximum operating pressure higher than 15 bar, to be located outside the fences of the gas installations.
From 1970 to 2013, the primary failure frequencies for the entire period (up to the year) per cause keep decreasing (See Figure
Failure frequencies of different causes by EGIG.
In 2013, the primary failure frequency over the entire period (1970–2013) was equal to 0.33 per kkm·yr. This is slightly lower than the failure frequency of 0.35 per kkm·yr reported in the 8th EGIG report (1970–2010). The primary failure frequency over the last five years was equal to 0.16 per kkm·yr, showing an improved performance over recent years.
Top 3 causes for gas pipeline failures in EGIG are external interference, corrosion, and construction defects/material failure (see Figure
Failure causes by EGIG.
According to statistical results, in period of 1970–2013, only 5.0% of the gas releases recorded in the EGIG database ignited. Gas releases from large diameter pipelines at high pressure have ignited more frequently than smaller diameter pipelines at lower pressure (see Figure
Ignited failures analysis by EGIG.
The highest fatality and injury rate can be found among the people who are directly involved in causing the incident. Eight cases (0.61%, total 1309) caused fatalities among the people causing the incident (see Figure
Casualties’ analysis by EGIG.
Up to 2014, the total length of UKOPA pipeline becomes 22.4 kkm. 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.
From 1962 to 2014, altogether 192 leakages have been recorded. The overall failure frequency over the period 1962 to 2014 is 0.219 incidents per kkm·yr, while in the previous report this figure was 0.223 incidents per kkm·yr (covering the period from 1962 to 2013). The overall trend continues to show a reduction in failure frequency (see Figure
Average failure frequencies by UKOPA.
The top 3 failure causes of UKOPA are external corrosion, external interference, and girth weld defects (see Figure
Failure causes by UKOPA.
There were 9 out of 192 (4.7%) product loss incidents that resulted in ignition. However, there is no obvious conclusion, as shown in Table
Ignited failures analysis by UKOPA.
Affected Component | Cause Of Fault | Hole Diameter Class |
---|---|---|
Pipe | Seam Weld Defect | 0–6 mm |
Pipe | Ground Movement | Full Bore and Above |
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 |
Up to 2015, the total length of PNGPC long-distance pipeline becomes 53 kkm. Failure data were filtered in order to be comparable with other countries. Only unintentional leakages for crude oil, refined oil, and natural gas for transmission lines are counted here.
Failure frequency has increased before 2011 and decreased in recent 5 years (see Figures
Mileage and failure numbers for PNGPC pipelines.
Average failure frequencies by PNGPC.
During 2006 to 2015, altogether 134 leakages have been recorded, among which, illegal tap, manufacturing defects, and construction quality are the top 3 causes (see Figure
Failure causes by PNGPC.
Investigation and referring to foreign related failure statistics can provide good experience for domestic pipeline operators, while figuring out their own management level for continuous improvement.
Compared with the failure frequencies (5 years’ moving average) at home and abroad in the past 10 years, the value of PNGPC’s oil pipelines is higher than that of the US, while that of PNGPC’s gas pipeline is roughly at the same level compared to the US and slightly lower than the European (see Figures
Compared failure frequencies for oil pipelines.
Compared failure frequencies for gas pipelines.
Compared with foreign countries, failure consequence data is quite deficient in China. Only the consequences of serious pipeline accidents will be recorded, including casualties, economic losses, and leakage.
As for the concern from government and public on pipeline safety in China, management has been significantly improved by operators. Consequently, frequency of pipeline failures is decreasing. According to the statistical results, PNGPC is not very far compared with foreign countries. There are still some aspects both in technology and in management that should be improved, such as quality of manufacture and construction of pipeline and third party monitoring.
Pipeline and Hazardous Materials Safety Administration
European Gas Pipeline Incident Data Group
United Kingdom Onshore Pipeline Operators’ Association
PetroChina Natural Gas & Pipeline Company.
The authors declare that there are no conflicts of interest regarding the publication of this paper.
Preparation of this paper was supported by the PNGPC; this is gratefully acknowledged by coauthors Dongpo Wang, Ting Wang, Qingshan Feng, and Xinqi Yang. Thanks are also due to numerous past and present colleagues for insights and helpful discussions.