管道运行英文翻译.docx

1、管道运行英文翻译3 Third-party Damage Index Third-party Damage Index A. Minimum Depth of Cover 0-20 pts 20% B. Activity Level 0-20 pts 20% C. Aboveground Facilities 0-10 pts 10% D. Line Locating 0-15 pts 15% E. Public Education Programs 0-15 pts 15% F. Right-of-way Condition 0-5 pts 5%G. Patrol Frequency 0-1

2、5 pts 15% 0-100pts 100%This table lists some possible variables and weightings that could be used to assess the potential for third-party damages to a typical transmission pipeline (see Figures 3.1 and 3.2).BackgroundPipeline operators usually take steps to reduce the possibility of damage to their

3、facilities by others. The extent to which mitigating steps are necessary depends on how readily the system can be damaged and bow often the chance for damage occurs.Third-party damage, as the term is used here, refers to any accidental damage done to the pipe as a result of activities of personnel n

4、ot associated with the pipeline. This failure mode is also sometimes called outside force or external force, but those descriptions would presumably include damaging earth movements. We use third-party damage as the descriptor here to focus the analyses specifically on damage caused by people not as

5、sociated with the pipeline. Potential earth movement damage is addressed in the design index discussion of Chapter 5. Intentional damages are covered in the sabotage module (Chapter 9).Accidental damages done by pipeline personnel and contractors are covered in the incorrect operations index chapter

6、 (Chapter 6). U.S. Department of Transportation (DOT) pipeline accident statistics indicate that third-party intrusions are often the leading cause of pipeline failure. Some 20 to 40 percent of all pipeline failures in most time periods are attributed to third-party damages. In spite of these statis

7、tics, the potential for third-party damage is often one of the least considered aspects of pipeline hazard assessment. The good safety record of pipelines has been attributed in part to their initial installation in sparsely populated areas and their burial 2.5 to 3 feet deep. However, encroachments

8、 of population and land development activities are routinely threatening many pipelines today. In the period from 1983 through 1987, eight deaths, 25 injuries, and more than $14 million in property damage occurred in the hazardous liquid pipeline industry due solely to excavation damage by others. T

9、hese types of pipeline failures represent 259 accidents out of a total of 969 accidents from all causes. This means that 26.7% of all hazardous liquid pipeline accidents were caused by excavation damage 87. In the gas pipeline industry, a similar story emerges: 430 incidents from excavation damage w

10、ere reported in the 1984-1987 period. These accidents resulted in 26 deaths, 148 injuries, and more than $18 million in property damage. Excavation damage is thought to be responsible for 10.5% of incidents reported for distribution systems, 22.7% of incidents reported for transmission/gathering pip

11、elines, and 14.6%of all incidents in gas pipelines 87. European gas pipeline experience, based on almost 1.2 million mile-years of operations in nine Western European countries, shows that third-party interference represents approximately 50% of all pipeline failures 44.Figure 3.1 Basic risk assessm

12、ent model.Figure 3.2 Assessing third-party damage potential: sample of data used to score the third-party damage index.ExposureTo quantify the risk exposure from excavation damage, an estimate of the total number of excavations that present a chance for damage can be made. Reference64 discusses the

13、Gas Research Institutes (GRIs) 1995 study that makes an effort to determine risk exposure for the gas industry. The study surveyed 65 local distribution companies and 35 transmission companies regarding line hits. The accuracy of the analysis was limited by the response-less than half (41%) of the c

14、ompanies responded, and several major gas-producing states were poorly represented (only one respondent from Texas and one from Oklahoma). The GRI estimate was determined by extrapolation and may be subject to a large degree of error because the data sample was not representative. Based on survey re

15、sponses, however, GFU calculated an approximate magnitude of exposure. For those companies that responded, a total of 25,123 hits to gas lines were recorded in 1993; from that, the GRI estimated total U.S. pipeline hits in 1993 to be 104,128.For a rate of exposure, this number can be compared to pip

16、eline miles: For 1993, using a reported 1,778,600 miles of gas transmission, main, and service lines, the calculated exposure rate was 58 hits per 1000 line miles. Transmission lines had a substantially lower experience; a rate of 5.5 hits per 1000 miles, with distribution lines suffering 71 hits pe

17、r 1000 miles 64. All rates are based on limited data. Because the risk of excavation damage is associated with digging activity rather than system size, “hits per digs” is a useful measure of risk exposure. For the same year that GRI conducted its survey, one-call systems collectively received more

18、than an estimated 20 million calls from excavators. (These calls generated 300 million work-site notifications for participating members to mark many different types of underground systems.) Using GRIs estimate of hits, the risk exposure rate for 1993 was 5 hits per 1000 notifications to dig64.Risk

19、variablesMany mitigation measures are in place in most Western countries to reduce the threat of third-party damages to pipelines. Nonetheless, recent experience in most countries shows that this remains a major threat, despite often mandatory systems such as one-call systems. Reasons for continued

20、third-party damage, especially in urban areas, include Smaller contractors ignorant of permit or notification process No incentive for excavators to avoid damaging the lines when repair cost (to damaging party) is smaller than avoidance cost. Inaccurate maps/records Imprecise locations by operator.

21、Many of these situations are evaluated as variables in the suggested risk assessment model. The pipeline designer an4 perhaps to an even greater extent, the operator can affect the probability of damage from third-party activities. As an element of the total risk picture, the probability of accident

22、al third-party damage to a facility depends on. The ease with which the facility can be reached by a third party The frequency and type of third-party activities nearby. Possible offenders include Excavating equipment Projectiles Vehicular traffic Trains Farming equipment Seismic charges Fence posts

23、 Telephone posts Wildlife (cattle, elephants, birds, etc.) Anchors Dredges. Factors that affect the susceptibility of the facility include Depth of cover Nature of cover (earth, rock, concrete, paving, etc.) Man-made barriers (fences, barricades, levees, ditches. etc.) Natural barriers (trees, river

24、s, ditches, rocks, etc.) Presence of pipeline markers Condition of right of way (ROW) Frequency and thoroughness of patrolling Response time to reported threats. The activity level is often judged by items such as: Population density Construction activities nearby Proximity and volume of rail or veh

25、icular traffic Offshore anchoring areas Volume of one-call system reports Number of other buried utilities in the area. Serious damage to a pipeline is not limited to actual punctures of the line. A mere scratch on a coated steel pipeline damages the corrosion-resistant coating. Such damage can lead

26、 to accelerated corrosion and ultimately a corrosion failure perhaps years in the future. If the scratch is deep enough to have removed enough metal, a stress concentration area (see Chapter 5 ) could be formed, which again, perhaps years later, may lead to a failure from fatigue, either alone or in

27、 combination with some form of corrosion-accelerated cracking. This is one reason why public education plays such an important role in damage prevention. To the casual observer, a minor dent or scratch in a steel pipeline may appear insignificant-certainly not worthy of mention. A pipeline operator

28、knows the potential impact of any disturbance to the line. Communicating this to the general public increases pipeline safety. Several variables are thought to play a critical role in the threat of third-party damages. Measuring these variables can therefore provide an assessment of the overall thre

29、at. Note that in the approach described here, this index measures the potential for third-party damage-not the potential for pipeline failure from third-party damages. This is a subtle but important distinction. If the evaluator wishes to measure the latter in a single assessment, additional variabl

30、es such as pipe strength, operating stress level, and characteristics of the potential third-party intrusions (such as equipment type and strength) would need to be added to the assessment.Assessing third-party damage potentialA. Minimum depth of cover (weighting: 20%) The minimum depth of cover is

31、the amount of earth, or equivalent cover, over the pipeline that serves to protect the pipe from third-party activities. A schedule or simple formula can be developed to assign point values based on depth of cover. In this formula, increasing points indicate a safer condition; this convention is use

32、d throughout this book. A sample formula for depth of cover is as follows:Amount of cover in inches -3 =point value up to a maximum of 20 pointsFor instance, 42 in. of cover =42 +3 points = 14points24 in. of cover =24 + 3 points = 8points Points should be assessed based on the shallowest location within the section being evaluated. The evaluator should feel confident that the depth of cover data are current and accurate; otherwise, the point assessments should reflect the uncerta