Impact of Improving Design Factor over 0.72 on the Safety and Reliability of Gas Pipelines and Feasi

CHINESE JOURNAL OF MECHANICAL ENGINEERING●166.Vol. 25, No.1, 2012DOI: 10.3901/CME.2012.01.166, avilable onlie at wwrnerik com; w.cjmenet.com; www.cjmenet.com.cnImpact of Improving Design Factor over 0.72 on the Safety and Reliabilityof Gas Pipelines and Feasibility JustificationZHAO Xinwei+.2*, ZHANG Guangli', LUO Jinhengl-2, and ZHANG Hua',1 Tiubular Goods Research Institute of China National Petroleum Corporation, xi 'an 710065, China .2 Petroleum tubular engineering Key Laboratory of China National Petroleum Corporation, Xi 'an 710065, ChinaReceived January 21, 2011; revised August 1, 2011; acepted August 15, 2011Abstract: Many years experience of the operation of high stress (> 72% spefied minimum ;yild strength, SMYS) gas pipelines andstatistical analysis resuts of pipeline incidents showed that the operating pipelines at stress levels over 72% SMYS have not presentedproblems in USA and Canada, and design factor does not control incidents or the safety of pipelines. Enhancing pipeline safetymanagement level is most important for decreasing incident rate. The aplication history of higher design factors in the U.S and Canadawas reviewed. And the efect of higher factors to the crtial flaw size, puncture rsistance, change of rlibilitt with time, risk level andthe arest toughness requiremneats of pipeline were analyzed here. The comparison of pipelie failure rates and risk levels between twodesign factors (0.72 and 0.8) has shown that a change in design facor from 0.72 to 0.8 would bring ltte efet on failure rates and risklevels. On the basis of the analysis result, the aplication fesibilit of design factor of 0.8 in China was discussed and the relatedsugestions were proposed. When an operator wishes to apply design factor 0.8 to gas pipeline, the fllowing proces is rcommended:stes level of line pipe hydro test should be up to 100% SMYS, rliabiliy and risk asessment at the design fesibilitiy or conceptualstage should be cnducted, Charpy impact energy should meet the need of peline crack arest; and etabish and execute risk basedintegrity management plan. The technology of pipeline stel meallury, line pipe fbrication and pipeline construction, and line pipequality control level in China achieved tremendous progresses, and line pipe product standards and property indexes have come up tointemational advanced level. Furthermore, pipeline safty management has improved greatly in China. Consequently, the resarch forthe feasibility of application of design factor of0.8 in China has fundamental basis.Key words: gas pipeline, higher design factor, safety and rlibilil, risk itegrity managementthe design and construction process of gas pipeline. At1 Introductionpresent, there are two kinds of method to increase theAs a number of high pressure gas pipelines projectefficiency and reduce the cost in the world, one of them is torepresented by the West-East gas pipeline have been built,use high grade and large diameter line pipe, the other is tothe fast development period of high-pressure large -diameterimprove the design factor's 0. With the fast advancement ofgas pipeline is coming in China. Until the end of“Eleventhpipeline steel metallurgy and line pipe fabrication technology,Five-year Plan"， the total length of high-pressurehigh strength line pipe steels, for example, API X70 and APIlarge-diameter gas pipeline including the 2nd West-East gasX80，have been used extensively in the important gaspipeline，the Kazakhstan-China gas pipeline,pipeline projects such as West-East gas pipeline, theRussia-China gas pipeline, the Myanmar-China gasShaan-Jing Gas pipelie and the 2nd West-East gas pipeline,pipeline and Sichuan-East gas pipeline will close to 15 000increasing the fficiency and reducing the cost remarkably.km. And the gas pipeline network has becomes the mainImproving design factor means to increase the designartery supporting the energy requirement in China. Thefactor(DF) above 0.72 in location Class 1 area. Currently,safety and reliability of pipelines in construction andthe design factor of all of gas pipelines in Class 1 is 0.72 inoperation process has direct influence on the developmentChina!". However, 0.8 design factor was adopted inof the national economy and social stability1-2].Canadian gas pipeline design codes in the 1970s, and manyPipeline operators are invetigating to find ways to reducegas pipelines are operated at the stress of 80% SMYSthe cost of new pipelines, or increase their transportation(Specified minimum yield strength)8. From the 1950s, theefficiency without reduction of the reliability and safety indesign factor hewe 072 hos hcr _1sed in several ga:pipelines in中国煤化工apact of using higherdesign factYHC N M H Gudied. In 1990s, 0.8* Corresponding author. E-mail: zxwzyf@163.comdesign factor was adopted in the ASME B31.8 which is theThis project is supported by China National Petroleum Corporationgas pipeline design code in Americal9. Furthermore,Application Fundamental Research Foundation (Grant No. 07A40401)oChinese Mechanial Engineering Society and Springer-Verlag Berin Heidelber 2012England and some other Euro countries are currentlyZHAO Xinwei, et al: Impact of Improving Design Factor over 0.72 on the Safety and Reliability●168●of Gas Pipelines and Feasibility Justificationindicates that the incident rate can be reduced effectively by(1) Provided that the operating pressure and diameter ofstrengthening risk management.pipe will remain unchanged, applying higher design factorASME summarized the data from the OPS incident means the nominal thickness of pipe can be decreaseddatabase from 1984 to 2001 in which the failure stresses accordingly, and it will reduce the critical defect size. Thatwere calculated based on the available data, and analyzed means the safety margin of pipeline decreased. In this paper,the relation between the stress (has direct relation with the the 2nd West-East gas pipeline was taken as example,design factor) with incident rate of pipeline, as Fig. 2 shows. which has an outside diameter of 1 219 mm and a steelIt can be seen that the highest percentage of incidents grade of X80. The western portion of the mainline with aoccurred on pipelines where the design factor at failure was design pressure of 12 MPa, and the nominal wall thicknessless than 0.40. The incident rate for the design factor of equals to 18.4 mm based on a design of 0.72, and 16.6 mm0.60 to 0.72 is about 60 percent of that for the design factor based on a design of 0.8. And the corresponding criticalof 0.40. It is also significant that only 2 percent of the flaw size of corrosion defect at two kinds of design factorsincidents occurred on gas pipelines with design factor was evaluated based on the ASME B3 1G code, as shown inabove 0.72. These data indicates that design factor does not Fig. 3[14.control incidents or the safety of pipelines. And the furtheranalysis indicates that the third party damage is the main16.0-14.0. Design factor of0.80cause for the pipeline incident which accounts for 39%, the12.0-一-- Design factor of 0.72pipeline incident caused by the corrosion and construction10.0-and manufacture defect account for 24% and 14%respectively, the pipeline incident caused other causes6.0一accounts for 23%.4.0-2001000030400Axial flaw length L/mm三2(Fig. 3. Critical faw size at different design factorsIt can be seen from Fig. 3 that the critical flaw size of thepipeline containing corrosion defect decreases in certaindegree due to the reduction in the wall thickness for the<0.40.4-0.5 0.5-0.6 0.6-0.72 >0.72higher design factor.Design factor a(2) Reduction of nominal thickness with the using ofFig. 2. Percentage of OPS incidents versus design factorhigher design factor reduces the puncture resistance ofpipelinelsl. In this paper, the West-East gas pipeline and theFrom 1954 to 2004, the incident rate of gas pipeline in 2nd West-East gas peline were taken ass xmples, whichCanada is 2.0x 10+ per km-years with the same level in thehave an outer diameter of 1 016 mm and 1 219 mm, and aAmerica. Although the detailed record and survey about thesteel grade of X70 (SMYS= =485 MPa, SMTS=570 MPa)relation between design factors with incident rate in Canadaand X80 (SMYS=550 MPa, SMTS=625 MPa), with theis unavailable, there are no reports that the design faclor design pessre of 10 MPa and 12 MPa, rspectively, andhas an important influence to the safety of the pipeline.the puncture resistance of the pipeline were studied atdifferent design factors with a range of 0.72 to 0.8, as3 Impact of Improving Design Factor on theshown in Fig. 4.Safety and Reliability for Gas Pipeline1 0003.1 Main aspects affecting the safety and reliability800for gas pipeline improved design factorIn some circumstances, reliability-based methods can be600used to justify less conservative design factors, and as thebasis for evaluating various design and inspection optionsand remedial of safety and reliability, and to determine therisk with the design and operation with pipeline. These200-techniques can incorporate the effects of risk mitigatingactivities, suchas surveillance, inspection, anMAOPp中国煤化工1010110|101101(11-13])maintenanceSteelEK70|)X70|)X70 X70 X70Design faMHC N M H 6.210.7410.76|0.78 0.80The impact of improving design factor on the safety andreliability for gas pipelines includes the following severalDiameter D/ mm |i 2191 2191 2191 2191 2191 0161 0161 0161 0161 01aspects.Fig. 4. Puncture resistance of pipe at different design factorsCHINESE JOURNAL OF MECHANICAL ENGINEERING●169.It can be seen from Fig. 4 that the increase of the design factor will reduce the critical defect size and the puncturefactor decreases the puncture resistance of pipeline at the resistance of pipeline, hence made the failure probability ofsame operating pressure, line pipe grade and diameterpipeline increase. Taking the 2nd West-East as example inbecause of the reduction of nominal thickness for using of this section, the reliability of pipelines operated with thehigher design factor.design factor of 0.72 and 0.8 is calculated and analyzed.(3) The increase of design factor means the improvementTwo scenarios are taken into account of reliability analysis,of hoop stress of pipeline, and it raises the driving force of one is that pipeline is free of defects, and the other is thatcrack propagation. Consequently, it will be more difficult topipeline is containing defects. In Class 1 area, the 2ndcontrol the fracture of gas pipeline. It can be concluded that West-East has an outside diameter of 1219mm and athe requirement for the toughness of line pipe should benominal thickness of 18.4 and a steel grade of API X80,improved to arrest the ductile fracture, and to avoid the with a design pressure of 10 MPa.crack long-range propagation.Based on the Barlow equation and Stress-Resistance(4) In theory, the use of design factor improves the hoop interference theory, and supposed the ceofficient ofstress of pipeline, and it increases the sensitivity of stress variation (COV) of pressure equals to 0.1, the reliability ofcorrosion crack of pipeline to some extent. There are nearpipeline without defect operated with design factors of 0.72neutral soil stress corrosion cracking incidents that had and 0.8 are calculated, that are 10 -"1 and 10~4, respectivelyoccurred on 22 oil and gas transmission pipelines inon the basis of statistical result of X80 strength data.Canada, and the stress level of pipeline stress corrosionCorrespondingly, the reliability of pipeline is high enoughcracking is in the range of 46% to 77% SMYS. Research and beyond the target reliability of 0.999 in low risk areashowed that the stress corrosion crack threshold is below recommended in DNV RP F101. However, it is inevitable72% SMYS. From this point of view, the stess corrosion that there are defects and damages ocurred in pipelines,crack have the same sensitivity for the pipeline at 72%and it will be more realistic to analyze the reliability ofSMYS and 80% SMYS. Just because of this, the National pipeline containing defects in engineering.Energy Bureau (NEB) of Canada considered that theThe statistical results of the pipeline incidents indicatereduction in operating stress would not be an effective way that the corrosion and the equipment impact are the majorto avoid SCC in existing pipelines and the most effective failure threats for the pipeline. The failure probability ofway of addressing the issue of SCC would be 'through 2nd West-East gas pipeline operated with design factors ofcompany-specific SCC management programs' that require0.72 and 0.8 were analyzed due to the corrosion andthe specific application to specific pipelines of the equipment impact. For the failure probability analysis dueknowledge afer the survey for the stess crrosion crackof to corrosion, the moderate corrosion (0.04 mm/a) andpipeline in the end of the 1990s.corrosion (0.09 mm/a) were respectively taken into(5) The improvement of design factors could result inaccount. The failure probability due to equipment impactdecrease of nominal thickness and reduction of criticalwas evaluated as the probability (frequency) of impactdefect size for pipeline, and all these change increase thmultiplied by the failure probability resulted from a certainfailure probability and risk level of pipeline. However, theimpact. The probability of equipment impact wasengineering experience indicates that the failure probabilitycalculated using a fault tree model that incorporates theand the risk level can be controlled into the acceptablefrequency of excavation activity on the pipeline and typicalrange by implementing the risk based integrityequipment impact prevention measures to be implementedfor the 2nd West-East. The failure probability resulted frommanagement program.Although the improvement of design factor has somea certain impact was estimated with probability of punctureimpact on the safety and reliability of pipeline, theor dent-gouge. In addition, the periodical inspections forthe pipeline every ten years were incorporated in theapplication status of high design factor and survey resultsanalysis of the failure probability. The reliability analysisfor the incident rate of pipeline in America and Canadaconsiders two limit states, including ultimate limit stateindicate that design factor is not the control factor for the(ULS) and leakage limit state (LLS). Large leak with afailure probability of pipeline. And there are many leaking hole of more than 10 mm diameter and rupture areinfuence factors on the safety and incident rate of pipelines, considered as ULs. Small leak with a leaking hole of lesssuch as the thickness, the quality of manufacture and than 10 mm diameter is considered as LLs.construction, the depth of burial, the protection measures, The failure probabilities of pipeline due to corrosion andlocation Class, the pipeline patrol, and public awareness equipment impact versus operation time are ilustrated asalong the pipeline, the pipeline survillnce, the corrosion Fig. 5 and Fig. 6. The aceptable failure probabilities of thecontrol, the operating pressure control, the soil condition pipeline are 10 2 and 2.5x 10, respectively for LLS andand hydro test.ULS according中国煤化工beseenfromtheFig. 3 and FigC NMH G'ility of pipeline3.2 Comparison of the safety and reliability of pipeline operated with dhigher than thatwith design factors of0.72 and 0.8of the pipeline with design factor of 0.72. However, theAs the mentioned above, the improvement of design pipeline failure probabilties at 0.8 and 0.72 design factorZHAO Xinwei, et a!: Impact of Improving Design Factor over 0.72 on the Safety and Reliability●170.of Gas Pipelines and Feasibility Justifcationare all significantly lower than the allowable failure3.3 Requirement of higher design factor for the crackprobabilities. The sudden decreases in the failurearrest toughness of pipelineprobability at years 11, 21, 31, and 41 reflect the impact ofCrack propagation in gas pipelines is controlled byinspections and maintenances. It indicates that the integrityspecifying a toughness level for line pipe. The requirementsmanagement of pipeline is very important for assuring thefor the toughness of 2nd West-East gas pipelines operatedsafety of pipeline.with design factor of 0.72 and 0.8 were calculatedrespectively. And the 2nd West-East gas pipeline operatedwith design factors of 0.72 has a nominal wall thickness ofAllowable probability of failure0-5-a=0.8018.4 mm and with a design pressure of 10 MPa in eastern十a=0.72portion and 12 MPa in western portion. If the design factor0-6-increased up to 0.8, two kinds of technology route can beselected. One is to raise the design pressure up to 13.3 MPa,and another is to reduce the nominal wall thickness down to16.6 mm. The requirements for the crack arrest of 2nd0δ511520253035404550West-East gas pipeline operated with two design factors(0.72 and 0.8) were calculated based on the Battelle Two(a) Utimate limit stateCurve (BTC), and the modification factor of 1 .43 based onthe burst test data of X80 line pipes worldwide proving the。prediction value in theory was introduced. The compositionof gas considered for the calculation is listed in Table 1.- Allowable probability of failure0-4}”→a=0.72Table 1. Composition of gas for the calculation of cracko-6-arrest toughness of the 2nd West-Easto~8CompositionC12C3iC4Wt.%.50.40~05101520253035404550nC4iC5nC5C6YearWt%).40.2(b) Leakage limit stateC7CO20.10.5Fig. 5. Probability of failure due to moderate corrosionand equipment impactThe calculated results of 2nd West-East operated with0→rdifferent design factors were listed in Table 2. It can beseen from Table 2 that the requirement for the crack arresto-5+←d=0.72toughness of pipeline operated with design factor of0.8 is告50- 60 J higher than that of the pipelines operated with室106-design factor of 0.72. It means that the requirement for thecrack arrest toughness of pipeline increases for higher0-7-design factor. The statistical results of Charpy impactenergy (Charpy V Notch, CVN) test data of X80 line pipes10-8010were shown in Fig. 7. It can be seen that the Charpy impactenergy above 260 J accounts for more than 80%. The(a) Ultimate limit stateimpact toughness of the line pipes can meets the10-requirement of the gas pipeline operated with design factorg10of 0.8 by raising further the technological level of steel信10-llloypble poabilily of filuremetallurgy and line pipe fabrication.→a=0.72。10-Table 2. Comparison of crack arrest toughness of pipelinewith diferent design factors (15 C)旨10-CalculationDesignWall thickness CVNpressureMethot/mmC/J中国煤化工204C5CBTC wiMYHCNMH G .15.32031218.4215modificationFig. 6. Probability of failure due to severe corrosionfactor of 1.430.80116.626318.267CHINESE JOURNAL OF MECHANICAL ENGINEERING171●! 500r口Histogram ofCVN712factor of gas pipeline design codes worldwide are all based。2 000+ Cumulative distribution probabiliton 0.72 design factor recommended by pressure piping2000committee of the American Standard Association (ASA) in-0.8F 6581955. America and Canada own the most of the gas-0.6pipelines operated at stress levels above 72% SMYS. The寻1000F 035|I 11total length of gas pipeline operated with design factor-0.4above 0.72 is more than 10 000 km from 1953 to 1971 in00-589 1[ 4750.2 2America. In Canada, 0.8 design factor of gas pipeline has。8上219169.been applied since 1973， and the total length of ga:220 240 260 280 300 320 340 360 380 >400pipelines with above 0.72 design factor owned byCharpy impact energy of X80 E/JTransCanada Company is approximately 18 000 km. It canFig. 7. Charpy impact energy statistical histogram of X80be concluded from the statistical results of pipeline incidentrates and the operation experiences in America and Canadathat the improvement of design factor could increase the4 Impact of Higher Design Factor on theincident rates slightly, whereas the key to control pipelineRisk Level of Gas Pipelineincident rates is to advance the integrity management levelof pipelines. The analysis results of reliability and riskSince the 1909, the pipelie operators wordwide have indicated that the improvement of design factor couldbeen interested in risk asessment of oil and gas pipeline,increase the failure probabilities and risk level in certainand the most representative integrity management codes ofdegree, but they are still within the acceptable range.pipeline including ASME B31.8S (2001) and API 1160Starting from the Shaan-Jing gas pipeline project in(2001), take the risk assessment as the basis and main1990s, with completion of a number of high pressure gascontent'Risk assessment plays a very important rolepipeline projects, such as the West-East gas pipeline, thein the integrity management of oil and gas pipeline2nd Shaan-Jing gas pipeline and the 2nd West-East, thein-service and the safety pre-assessment of new pipeline.It can be concluded from the analysis above that thetechnology of pipeline steel metallurgy, line pipeimprovement of design factor increased the failurefabrication and quality control, and pipeline constructionprobability of pipeline and raise the risk level of pipelinehave made tremendous progresses in China, and line pipeundoubtedly. Taking the 2nd West-East gas pipeline as product standards and property indexes have come up to .example, the crresponding individual risk level of pipeline international advanced level. The stability of line pipewith design factors of 0.72 and 0.8 containing mechanicalfabrication quality has been greatly improved. For example,damage were studied. The calculation results were showed the minus deviation of the wall thickness of line pipein Fig. 8. Compared with design factor of 0.72, thedecreased from 12.5% in eatly stage to 5% 8% at present,individual risk of pipeline operated with design factor ofand that of the line pipes used in the West-East gas pipeline0.8 is a ltte higher. However, both the individual risks of is about 3%. The requirement for the impact energy of line0.72 and 0.8 design factors are significantly lower than thepipes is not less than 220 J in the 2nd West-East gasacceptable individual risk 10° per year which is recognized pipeline project, and the stistical results for the impactand applied worldwide.energy test data of X80 steel pipes after going into massproduction indicates that more than 90% of impact energy10rtest data are above 260 J. which operated with the design8. --- 0.80factors of 0.8, The key property indexes and product qualityof the domestic gas pipelines have reached to level ofAlliance pipeline and the Rockies express pipeline which三6are operated at stress up to 80% SMYS, even some indexesis more strict than those two pipelines. Besides, the safety4management level of pipelines has been improved greatlybecause of the implementation of integrity management.圣2All these advancements provide strong basis and conditionfor application of 0.8 design factor in gas pipelines in50150 200250 30China. The following four aspects should be taken carefullyDistance S/mif 0.8 design factor was adopted: (1) Mill hydro test stressFig. 8. Individual risk associated with mechanical damageof line pipe should be up to 100% SMYS; (2) The reliabilityat design factorsanalysis and中国煤化工arried out duringproject feasibilHCNMH(impact energy of5 Discussionline pipe shoulrack arrest ofgas pipeline; (4) The integrity management program basedIt can be seen from the analysis above that the designon the risk should be developed and implemented.ZHAO Xinwei, et al: Impact of Improving Design Factor over 0.72 on the Safety and Reliability●172●of Gas Pipelines and Feasibility Justifcation[6] MARTIN Mclamb, PHIL Hopkins, Mark Marley et al. A justification6 Conclusions and Suggestionsfor designing and operating pipelines up to stresses of 80SMYS[C/CD]. Proceedings of IPC 2002, 4th International PipelineConference. Calgary, Alberta, Canada, September 29 October3,(1) The design factors above 0.72 have been used inmany gas pipelines in America and Canada for many years,[7] Ministry of Construction of People's Republic of China. GBand the statistical results of the pipeline incident rates and50251-2003: Code for design of gas transmission pipelinethe operation experience indicate that the improvement ofengineering[S]. Beijing: China Planning Press, 2003.design factor would not result in increase of the incident[8] CSA Z662-2007: Oil and gas pipeline systems[S]. Canadianrate, and the most effective way to reduce the incident rate[9] ASME B31.8: Gas Transmission and distribution piping systems[S].Standards Association, 2007.is to improve the safety management of pipelines.The American Society of Mechanical Engineers, 2007.(2) The analysis results of reliability and risk of gas10] IGE/TD/1 Eition 3: Steel Pipelines for High Pressure Gaspipelines at different design factors indicated that theTransmission[S]. The Institution of Gas Engineers, 2001.improvement of design factor could increases the failure [11] ANDREW Francis, ALAN Edwards, RICHARD Espiner, et al. Anprobabilities and risk level, but they are still below theassessment procedure to justify operation of gas transmissionpipelines at design factors up to 0.8[C/CD]. 3rd Internationalacceptable threshold values.Pipeline Technology Conference Brugge, Belgium, 2000.(3) After more than 10-year fast development in gas[12] ANDREW Francis, ALAN Edwards, RICHARD Espiner. Reliabilitpipeline construction, the technology of pipeline steelbased approach to the operation of Gas Transmission Pipelines atmetallurgy, line pipe fabrication and quality control, andDesign Factors greater then 0.72[C/CD]. 17th Internationalpipeline construction have made tremendous progresses,Conference Offshore Mechanics and Arctic Engineering, Lisbon,Portugal, 1998and line pipe product standards and property index have[13] ZIMERMAN TJ E, HOPKINS P, SANDERSON N. Can limit statereached to international advanced level. In addition, thedesign be used to design a pipeline above 80% SMYS[C/CD] 17thsafety management level improved greatly because of theInternational Conference Ofshore Mechanics and Arcticimplementation of integrity management programs ofEngineering, Lisbon, Portugal. 1998.pipeline. All these advancement established strong basis[14] ASME B31G: Manual for determining the remaining strength ofcorroded pipelines[S]. The American National Standard, 2009.and condition fot application of design factor of 0.8 in the[15] DRIVER R G PLAYDON D K. Limit states design of pipelines forgas pipeline in China.accidental outside force[R]. Report to the National Energy Board,(4) The following four aspects should be noted if 0.81997.design factor was used: 1) mill hydro test stress of line pipe[16] ASME B31.8S: Managing system integrity of gas pipeline[SI. Theshould be up to 100% SMYS; 2) the reliability analysis andAmerican National Standard, 2001.risk asessment should be carried out during project [17] API 1160 Managing system. integrity for hardous liquidfeasibility research stage; 3) the impact energy of line pipepipeline[S]. American Petroleum Institute, 2001.should meet the requirements for crack arrest of gasBiographical notespipeline; 4) the integrity management program based on theZHAO Xinwei, bom in 1969, PhD, professorate senior engineer,risk should be developed and implemented.the Chief Expert at Tubular Goods Research Instiute of ChinaNational Petroleum Corporation and the vice director ofReferencesPetroleum Tubular Engineering Key Laboratory, China National[1] LI Helin, JI Lingkang, TIAN Wei. Several technique advancements Petroleum Corporation. His research fields include the riskin the West-East and the 2nd West-East gas pipeline engineering assessment and the integrity assessment of oil & gas pipeline.project[J]. Natural Gas Industry, 2010, 30(4): 84 -90.Tel: +86-29-88726151; E mail: zxwzyf@163.com[2] ZHAO Xinwei, LI Helin, LUO Jinheng, et al. Managcrial techniqucfor integrity of oil and gas pipeline and its progress[] China SafetyZHANG Guangli, born in 1980, engineer, his research field is theScience Journal, 2006, 16(1): 129- -135.integrity assessment of oil & gas pipeline.[3] PHIL Hopkins. High design factor pipelines: integrity issues[J]. Tel: +86-29-88726204; E-mail: zhangguangli@cnpc.com.cnJournal of Pipeline Integrity, 2005, 4(2): 69-97.[4] ROBERT J Eiber, HOPKINS P. Impact on operaional integrity and LUO Jinheng, born in 1972, PhD, senior engineer, director ofsafety of high design factors for new and upgraded pipelines[C/CD].Safety Assessment and Integrity Research Center of TubularInternational Seminar-Launch of the Public Comment Draft of the Goods Research Institute, China National Petroleum Corporation.Revision of AS 2885.1, APIA, Wollongong, Australia, Dec. 7-8, His research field is the risk assessment and the integrity2004.assessment of oil & gas pipeline.[5] GARY Senior, PHILL Jones. Justifying the updating of aTel: +86-29 -88726152; E-mail: luojh@cnpc.com.cntrasmission pipeline to a stress level of over 72% SMYS- aoperator's experience[CICD]. Proceedings of OMAE 99, 18th ZHANG Hua, borm in 1977, senior engineer, his research field isInternational Conference on fshore Mechanics and Arctic the risk asessment of oil & gas pipeline.Engineering. St. Johns, Newfoundland, Canada, July 11-16, 1999.Tel: +86-29-88726204; E-mail: zhanghua011@cnpc.com.cn中国煤化工MYHCNMHG