Table Of ContentReport No. #DTRS 56-94-C-0006 PIPELINE ACCIDENT EFFECTS FOR NATURAL GAS TRANSMISSION PIPELINES Eugene Golub, Ph.D., P.E. Joshua Greenfeld, Ph.D., L.S. Robert Dresnack, Ph.D., P.E. F.H. Bud Griffis, Ph.D., P.E. Louis J. Pignataro, Ph.D., P.E. NEW JERSEY INSTITUTE OF TECHNOLOGY Institute for Transportation 323 Martin Luther King Boulevard Newark, NJ 07102 FINAL REPORT This document is avaiIab~e through the National Technical Information Service, Springfield, Virginia 22161 Prepared for U.S. DEPARTMENT OF TRANSPORTATION Research and Special Programs Administration Office of Pipeline Safety Washington, DC 20590AUGUST 1996
NOTICEThis document is disseminated under the sponsorshipof the Department of Transportation in the interest ofinformation exchange. The United States Governmentassumes no liability for the contents or use thereof.
Technical Report Documentation Page1. Report No. 2. Government Accession No.DTRS56-94-C-0006-33. Recipient's Catalog No.4. Title and SubtitlePIPELINE ACCIDENT EFFECTS FOR NATURAL GAS TRANSMISSION PIPELINES5. Report DateAugust 19966. Performing Organization CodeDOT/RSPA/OPS No.7. AuthorsEugene Golub; Joshua Greenfeld; Robert Dresnack; F.H. Bud Griffis;Louis J. Pignataro8. Performing Organization Report . Unit No.9. Performing Organization Name and AddressNEW JERSEY INSTITUTE OF TECHNOLOGYInstitute for Transportation323 Martin Luther King Blvd.Newark, NJ 0710210.11. Contract or Grant No.DTRS 56-94-C-000612. Sponsoring Agency Name and AddressU.S. DEPARTMENT OF TRANSPORTATIONResearch and Special Programs Administration/Office of Pipeline Safety400 7th St. S.W., Rm. 2335Washington, D.C. 2059013. Type of Report and PeriodFinal Report14. Sponsoring AgencyOPS15. Supplementary Notes 16. AbstractFrom an analysis of incident and annual data filed with the Office of Pipeline Safety OPS, the project team identified thefactors that effect accidents on gas pipelines. Since the normalizing of the data was not always possible, the authors ofthis report used indirect and inferential approaches in the analysis. The ALTRN database, the incident database from1970 to 1981, while older and having many errors, was used extensively in this report because it contains much moreinformation than the later PIP and TLEAK database, the incident databases from 1982 to 1994. Also, because theproperty damage threshold for reporting incidents was an order of magnitude lower in ALTRN than in TLEAK, the numberof incidents reported was also an order of magnitude larger. The larger database facilitated the analysis because therewas always a significant number of records to examine containing any of the variables considered.It was found that pipe wall thickness, depth of cover and pipe manufacture are important factors in the occurrence ofincidents.17. Key WordsU.S. and Foreign Pipeline Regulations, Rehabilitation,Retrofitting, Repair, Gas, Hazardous Liquids, Pipeline,Safety, Maintenance, Transmission Lines, Operator,Corrosion, Welding, Urban Areas, Siting, Land Use,Environmental Impact.18. Distribution Statement19. Security Classification of this report 20. Security Classification of this page 21. No. of Pages 22. PriceUnclassified Unclassified 229Form DOT F 1700.7 8-72Reproduction of form and completed page is authorized
TABLE OF CONTENTS1.0 EXECUTIVE SUMMARY.........................................................................1 1 .1 OBsERVATIONS & CONCLUSIONS..........................................................1 1.2 REcoMMENDATIONS.....................................................................22.0 INTRODUCTION..............................................................................2 2.1 RSPNOPS DATABASE DESCRIPTION........................................................3 2.2 GAS TRANSMISSION PIPELINE DATABASE..................................................3 2.2.1 Incident Reports Description..................................................3 2.2.2 Annual Reports Definition.....................................................3 2.2.3 Annual Reports Description....................................................4 2.3 ACCURACY OFTHE DATABASE.............................................................4 2.4 NORMALIZING DATA IN THE DATABASE....................................................53.0 INCIDENT RATES BY YEAR AND CAUSE..........................................................6 3.1 ORIGINAL OPS DATABASE...............................................................6 3.2 DATA NORMALIZED TO MINIMUM $50,000 PROPERTY DAMAGE IN 1984..........................94.0 INCIDENT RATES - CORROSION................................................................11 4.1 CORROSION INCIDENT RATES FOR PIPE THAT IS NOT PROTECTED CATH0DIcALLY..............13 4.2 CORROSION INCIDENT RATES FOR UNCOATED PIPE........................................14 4.3 CORROSION INCIDENT RATES WITH UNPR0TECTED & UNCOATED WRAPPED PIPE...............165.0 INCIDENTS BY CAUSE AND COVER DEPTH........................................................19 5.1 ALTRN DATABASE 1970-1 981...........................................................19 5.2 DISTRIBUTION OF INCIDENTS BY CAUSE VS. DEPTH OF COVER...............................21 5.3 YEAR OF INSTALLATION OF THE PIPELINE AS RELATED TO DEPTH .OF COVER..................236.0 INCIDENTS AS RELATED TO LAND USE..........................................................24 6.1 ALTRN DATABASE......................................................................24 6.1 .1 Land Use at the Time of Installation of the Pipeline.........................24 6.1.2 Land Use at the Time of the Incident..........................................26 6.2 PIPDATABASE--1982-1984..............................................................27 6.2.1 Incidents by Land Use Near Pipelines..........................................27 6.2.2. Analysis of Database With Regard to Completeness of Records at Time of Incident...........................................................30 6.2.3 Incidents vs. Land Use at Time of Incident....................................31 6.3 TLEAK DATABASE 1984-1 993...........................................................32 6.3.1 Incidents vs. Class Location..................................................32 6.3.2 Property Damage vs. Class Location............................................33 6.3.3. Property Damage vs. Land Use at the Time of Installation of the Pipeline.....347.0 METHOD OF MANUFACTURE OF STEEL PIPE.......................................................36 7.1 PIPE MANUFACTURE VS. TYPE OF MATERIAL FAILURE.......................................448.0 INCIDENTS VS. YEARS OF OPERATION..........................................................469.0 RELATIONSHIP BETWEEN AGE, CORROSION AND INCIDENT RATES....................................49
10.0 PIPE DIAMETER & WALL THICKNESS VS. INCIDENT RATES.............................53 10.1 ALTRN DATABASE 1970-1982...................................................53 10.1.1 Incident Rate vs. Pipe Thickness and Pipe Diameter...................55 10.1.2 Pipe Diameter vs. Incident Rates.....................................56 10.2 TLEAK DATABASE 1984-1993...................................................5811.0 OPERATING AND MAOP vs. INCIDENT RATES.........................................60APPENDIX A: ANALYSIS OF THE NATURAL GAS TRANSMISSION PIPELINE DATABASES INTRODUCTION Al DETAILED CONTENTS OF THE NATURAL GAS PIPELINE DATABASE...............Al-i Introduction........................................................Al-i Analysis of the Incident Databases..................................Al-i Details of the Incident Databases...................................Ai-2 ALTRN Database......................................................A12 PIP Database.......................................................Ai44 TLEAK Database.....................................................Al 57 A2 ERRORS IN THE NATURAL GAS PIPELINE DATABASE..........................A2-l Introduction........................................................A21 Changes in the Information Maintained in the Database Over the Period of the Record.......................................................A2-i Gas Transmission Pipeline Database..................................A2-2 Incident Report Forms...............................................A2-2 Annual Report Forms.................................................A2-6 Data Reported by Operators - Not Entered Into the Database by RSPNOPS A2-28 Duplicate Records That Became Part of the Database Because Duplicate Reports were filed or Data Processing Resulted in the Duplicate Records in the Database....................................................A2~29 Different Values Being Used to Represent the Same Information for a Particular Field in the Database...................................A2-31 "Real" Fields Being Entered Into An Incorrect Position in the Data Field Resulting in an Incorrect Value in the Database....................A2-35 Typographic Errors in Entering the Data Into the Database..........A2-38 Incorrect Documentation of the Database............................A2-45 A3 NoRMALIzING DATA IN THE NATURAL GAS PIPELINE DATABASE................A3-i Introduction........................................................A3-l Specific Areas Where Normalizing Data is Lacking To Draw Statistically Significant Inferences................................A3-i Normalizing Data....................................................A3-i Incident & Annual Report Databases..................................A3-2 Questionnaires for Additional Data for Sample Group of Operators....A3-8APPENDIX B: Bi RSPNOPS INCIDENT & ANNUAL REPORT FORMS...............................Bl-l B2 DEFINITION OF TERMS IN THE RSPNOPS DATABASE..........................B2-l ALTRN...............................................................B2-l PIP.................................................................B2-3 TLEAK...............................................................B2-7
1.0 EXECUTIVE SUMMARYThis report has been produced as part of a study to analyze the United States Department ofTransportation USDOT Research and Special Programs Administration RSPA - Oftice ofPipeline Safety OPS database on gas transmission pipeline incidents to determine the factorsthat are important in the occurrence of those incidents. The study also included the analysis ofa second OPS database of annual reports submitted by all natural gas transmission pipelineoperators.The report contains the analyses performed and the resulting observations, conclusions andrecommendations based on the study. The databases were ~lso studied in detail. Errors andproblems found in the databases are identified in Appendix A2 of this report.The major observations, conclusions and recommendations are summarized in Section 1.1,below, by topic area.1.1 OBSERVATIONS AND CONCLUSIONSINCIDENT CAUSE. The primary cause of incidents, as reported from 1970 to 1993, is "outsideforce". This is followed by "construction defect-material failure". In the most recent years ofreporting, the "other" category is the second largest category and almost as large as damageby outside force.CORROSION. Coating and cathodic protection are very important in reducing corrosion incidentrates. The average incident rates for the period of record 1970 to 1993 are 0.14 and 0.59 inci-dents/i ,000 mi-yr respectively for coated and uncoated pipe. The average incident rates for theperiod of record 1970 to 1993 are 0.17 and 0.40 incidents/i ,000 mi-yr respectively for protectedand unprotected pipe.DEPTH OF COVER. Inadequate depth of cover is a primary factor in outside force incidents.LAND USE VS. INCIDENTS. Where undeveloped land use becomes rural, the dominant cause ofincidents is outside force. The total number of incidents in the group under study is limited;however, there is a clear trend that outside force becomes the dominant cause of incidents.When the land use near a pipeline is more intense, the dominant source of incidents is outsideforce. This leads to the conclusion that the system becomes more vulnerable to third partydamage when development encroaches on a pipeline.PIPELINE MANUFACTURE. Although complete normalization of the data is not possible, it is clearthat electric resistance welded pipe installed in the 1940's and the 1970's has a high rate ofmaterial failure. -I
PIPELINE AGE VS; INCIDENTS Th~ age of a pipeline has a relationship to the cause and numberof incidents of transmission pipelines.PIPE WALL THICKNESS. Pipe wall thickness is a key factor in pipeline safety and reduced inci-dent rates.INCIDENT PRESSURE. The material defect cause of incidents displays sensitivity to the incidentpressure as a percent of MAOP. As the incident pressure increases as a percent of MAOP,material defect increases as the percent cause to a point where it reaches 82% at incidentpressure equal to MAOP.1.2 RECOMMENDATIONSINCIDENT CAUSE. The number of categories used to classify the cause of the incident on thegas transmission incident form should be increased to generate more informative and usefulresponses by the operators.DEPTH OF COVER. The industry should be alert to an increased risk of outside force incidentsfor older pipelines installed at depths that would not satisfy the pipeline safety standards in49CFR Part 192. The current incident form should be modified to include depth of cover infor-mation.DATABASE INTEGRITY. The original written reports submitted to RSPAJOPS should be investi-gated to ensure that if data was entered on the form they should also have been entered in thedatabase. Missing data in the database suggest that some of the data entered in the reportswere not entered into the computer database. The original incident data forms should be re-viewed and the databases corrected accordingly.PIPELINE MANUFACTURE. It is recommended that the total miles of pipe by type of manufacturebe determined in order to normalize the data. In this way one could determine the effective-ness of each type of manufacture in resisting incidents caused by construction or material de-fect.2.0 INTRODUCTIONThe purpose of this report is to analyze the various factors that contribute to the rate of occur-rence of incidents in gas transmission pipelines. As part of the analysis performed, factorswere considered by their importance in causing incidents. The analysis was performed on theResearch and Special Programs Administration RSPA - Office of Pipeline.Safety OPS data-base 2
2.1 RSPNOPS DATABASE DESCRIPTIONThe incident reports database was initiated in 1970 and consists of two separate components.The first component is the compilation of incident reports tiled by operators whenever an inci-dent as defined by OPS takes place. The second component, also filed by the operators, is anannual report that summarizes the system for the past year. The contents of each componenthave changed several times during the period from 1970 to the present. The two databasesare further divided into several separate databases reflecting changes in the reporting require-ments over the years. A summary of the databases is presented below:2.2 GAS TRANSMISSION PIPELINE DATABASE2.2.1 INcIDENT REPORTS DESCRIPTIONFILENAMERSPAFORMRSPA FORM TITLEFORMDATERECORDSFROM -TOALTRN7100.2Leak or Test Failure ReportGas Transmission & Gathering Systems1-70`70 --- `81PIP7100.2Leak or Test Failure ReportGas Transmission & Gathering Systems1-70`82 --- `84TLEAK7100.2Incident ReportGas Transmission & Gathering Systems3-84`84 --- `93FILE NAMEALTRN Detailed incident reports required. The minimum property damage criteria is $5,000. The database is very large, has many fields, and contains many rec- ords.PIP Detailed incident reports required. The minimum property damage criteria is $5,000. The database is very similar to ALTRN but not identical and therefore the two cannot be directly combined.TLEAK This incident reports database contains a fraction of the number of fields in ALTRN and has many fewer records because of the minimum property damage criteria which was raised to $50,000.2.2.2 ANNUAL REPORTS DEFINITIONFILE INAME IRSPAFORMRSPA FORM - TITLEFORM 1DATE ~RECORDSFROM - TOA1707971 00.2-1Annual Report for Calendar Year1 9__Gas Transmission Gathering_Systems10-70`70 --- `79AT808171 00.2-1 *Annual Report for Calendar Year.1 9__Gas Transmission Gathering_Systems11-82`80 --- `813
FILENAMERSPAFORM 1RSPA FORM - TITLE ~FORMDATERECORDSFROM - TOAT82837100.2-1Annual Report for Calendar Year19_Gas Transmission & Gathering Systems11-82`82 --- `83TRANS71 00.2-1Annual Report for Calendar Year19_Gas Transmission & Gathering Systems11-85`84 --- `94 2.2.3 ANNuAL REPORTS DEscRIPTION FILE NAME AT7079 Reports are very detailed. AT8081 Reports are identical to AT7079 and have been combined with same. AT8283 Reports are similar to AT7079 but only the total fields are entered. The majority of the information in the earlier annual reports is not entered. TRANS - The database covers many of the same topics as the earlier databases but not in the same detail, and therefore does not easily combine with the earlier data- bases. In summary, there are three separate incident and three separate annual report databases. The forms used for all databases may be found in Appendix Bi of this report. 2.3 ACCURACYOFTHE DATABASE One of the issues with regard to the databases is the incompleteness of the records. Often, in an individual incident record, one or more fields may be left blank. This may surface from time to time as an anomaly in the analysis. As an example of this phenomenon, consider the corro- sion data for 1972. It was found that 93 incidents occurred that year where the cause as speci- fied in the incident report was cited as corrosion. It was also found that 42 incidents occurred in coated pipe and 51 in uncoated pipe, also totaling 93 incidents. For the same data it was found that 67 of those incidents were on pipe that was cathodically protected while 25 were on non protected pipe, for a total of 92 incidents. One incident is missing. This anomaly occurred be- cause the field in the database that carries the information as to whether the pipe is protected or not was blank. The field could be blank for one of two reasons: it was not entered on the written incident report filed by the operator or it was not entered into the database by the "keypunch" operator. This type of anomaly occurs frequently. Therefore, it is understood that all values in the docu- ment represent incident rate/i ,000 mi-yr for the data reported and present in the database. The missing data should not effect the accuracy or reliability of the analysis. A detailed analysis of the database may be found in Appendix Al. 4
2.4 NORMALIZING DATA IN THE DATABASEIn order to rank the various factors considered, it would be necessary to express the incidentrate for a particular factor in terms of incidents per 1,000 mile-year. If this were done, rankingwould be from the highest to the lowest incident rate.It was not possible to express incident rates for alIfactors considered in this "normalized" fash-ion because the data to do so were not available in the OPS or other databases. To illustratethis point on normalized data, consider the following example: Assume that one wishes to compute the normalized incident rates caused by corrosion for 1970 where the pipe is either coated or not coated. Assume that there are 91 inci- dents in gas pipelines that year where 44 of the pipe were coated and 47 were not coated. Based upon this raw count of incidents, one would assume that the rates for coated and uncoated pipe were essentially the same. Consider now that there were approximately 37,500 miles of uncoated pipe and 212,500 miles of coated pipe in the system for that year. The normalized incident rates may now be computed as: Rate for Coated Pipe: 44 incidents / 212,500 miles x 1,000 = 0.21 incidents/i ,000 mi-yr of coated pipe Rate for Uncoated Pipe: 47 incidents / 37,500 miles x 1,000 = 1.25 incidents/i ,000 mi-yr of uncoated pipe In normalized form, it is seen that the incident rate for uncoated pipe is approximately six times greater than for coated pipe.The type of information used to normalize the incident rates in the example above, e.g., miles ofcoated and uncoated pipe in the system, is not available for many of the factors that are impor-tant to incident rates and therefore considered in this study.Even if normalizing information were available, the analysis would still be more complex thanjust producing normalized rates. Consider again the example cited above: It is also known that there were 61 incidents in 1970 caused by corrosion where the pipe was cathodically protected and 30 incidents where the pipe was not protected. Also, there were approximately 212,800 miles of pipeline that were cathodically protected that year while there were 37,100 miles that were not protected in the total system. This produces normalized incident rates of: 0.29 incidents/i ,000 mi-yr of cathodically protected pipe 0.81 incidents/i ,000 mi-yr of non-cathodically protected pipe 5
Description:The ALTRN database, the incident database from1970 to 1981, w . Pipe wall thickness is a key factor in pipeline safety and reduced inci-dent rates. Often, in an individual incident record, one or more fields may be left blank.
