1、 STP-PT-046 REVIEW OF SAFETY CONSIDERATIONS FOR NATURAL GAS PIPELINE BLOCK VALVE SPACING Prepared by: Robert J Eiber Consultant Inc and Kiefner and Associates M“E STANDARDS TECHNOLOGY, LLC Date of Issuance: September 12, 201 1 This report was prepared as an account of work sponsored by ASME Pressure
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9、8-0-7918-3379-7 Copyright 20 11 by ASME Standards Technology, LLC All Rights Reserved Review of Safety Considerations for Natural Gas Pipeline Block Valve Spacing STP-PT-046 TABLE OF CONTENTS Foreword v Abstract . vi Introduction I 2 LITERATURE REVIEW AND BACKGROUND INFORMATION . 2 2.1 Basis of ASME
10、 B31.8 Valve Spacing Requirements 2 2.2 Review of Prior Studies on Valve Types and Spacing 3 2.2.1 1995 Report on Remote and Automatic Main Line Valve Technology Assessment. 3 2.2.2 1997 Report on a Survey of Design Rationale for Valve Usage in Various Design Codes 4 2.2.3 2000 Report on Development
11、 of a Design Basis for Main Line Block Valve Spacing on Gas Transmission Pipelines . 4 2.2.4 2005 White Paper on Equivalent Safety for Alternative Valve Spacing 6 2.2.5 2006 Study on the Safety Impact of Valve Spacing in Natural Gas Pipelines . 6 2.2.6 Greenhouse Gas Emission Consideration Leading t
12、o Volume Limitations between Valves . 7 2.3 Conclusion of Literature Review . 8 3 REVIEW OF PHMSA INCIDENT DATA . 9 3.1 Proximity to the Public 9 3.2 Concentration of Gas Release . 11 3.3 Discussion . 12 4 REVIEW OF NATIONAL TRANSPORTATION SAFETY BOARD (NTSB) SERIOUS GAS TRANSMISSION INCIDENTS 16 4.
13、1 Mobil Oil Corp, High Pressure Natural Gas Incident, Houston, Texas, September 9, 1969 9 16 4.2 Michigan-Wisconsin Pipe Line Company, Monroe, Louisiana, March 2, 1974 1 0 . 17 4.3 Transcontinental Gas Pipe Line Corp 30 inch Gas Transmjssion Pipeline Failure, near Bealeton, Virginia, June 9, 1974 11
14、. . 18 4.4 Southern Union Gas Company Pipeline Failure near Farmington, New Mexico, March 15, 1974 12 . 18 4.5 United Gas Pipe Line Company, 20 inch Pipeline Rupture and Fire, Cartwright, Louisiana, August 9, 1976 13 . 19 4.6 Northern Natural Gas Company, Pipeline Puncture, Explosion and Fire, Hudso
15、n, Iowa, November 4, 1982 14 . 20 4.7 Mississippi River Transmission Corp. Natural Gas Flash Fire, Pine Bluff, Arkansas, October 1, 1982 15 . 20 4.8 Texas Eastern Transmission Corp. Natural Gas Pipeline Ruptures and Fires at Beaumont, Kentucky on April27, 1985 and Lancaster, Kentucky on February 2 1
16、, 1986 16 20 4.9 Texas Eastern Transmission Corp. Natural Gas Pipeline Explosion and Fire, Ellison, New Jersey, March 23, 1994 17 . . 21 4.1 0 Dredging ofTiger Pass, Louisiana, October 23, 1996 18 . 22 4. 11 Natural Gas Pipeline Rupture and Fire near Carlsbad, New Mexico, August 19, 2000 19 22 111 S
17、TP-PT-046 Review of Safety Considerations for Natural Gas Pjpeline Block Valve Spacing 4.12 NTSB investigation of Florida Gas Transmission Rupture alongside Florida Turnpike, May 4, 2009 20 . 23 4.13 Pacific Gas and Electric Company Natural Gas Transmission Pipeline Rupture and Fire, San Bruno, CA,
18、September 9, 2010 21 , 22) . 23 4.14 NTSB Conclusions 24 5 BLOWDOWN TIME RELATED TO VALVE SPACING . 25 6 CONCLUSIONS 27 References . 29 Acknowledgrnents . 31 LIST OF TABLES Table 1 -Summary ofPHMSA Incident Database Injuries and Fatalities from 2002 through 2009 . 1 0 Table 2- Class 1 Incidents with
19、 Total Costs $2.5 to $87.5 million 15 LIST OF FIGURES Figure 1 - Time to Make Safe versus Injuries and Fatalities in Class 1-3 Locations II Figure 2 -Fracture Propagation Lengths versus Injuries and Fatalities 11 Figure 3- Time to Make Area Safe versus Property Damage by Class Location 12 Figure 4-
20、Time to Make Area Safe versus Total Cost by Class Location l4 Figure 5 -Optimistic Blowdown Times for a 36 inch (914 mm) Diameter I 000 psig Pipeline with Valves Spaced from 1.4 to 20 miles (2.2. to 32 km) from the Rupture 26 IV Review of Safety Considerations for Natural Gas Pipeline Block Valve Sp
21、acing STP-PT-046 FOREWORD Block valves in pipelines have been used since pipelines were first constructed. They have been required in pipeline codes, such as ASME B3l.l.8 (predecessor to ASME B3l.8 Committee), since 1952. The quantity and spacing of sectionalizing block valves has a significant impa
22、ct on the construction cost of new pipeline. ASME B31.8 is considering alternative design rules with increased stress levels justified by better quality design and engineering, where different valve spacing allowances may be appropriate. Revisions to the ASME Code can serve as a model for evolution
23、of pipeline safety regulations in the U.S. Findings of this report will assist in defining the requirements for spacing and operator types for block valves in gas pipelines. Established in 1880, the American Society of Mechanical Engineers (ASME) is a professional not for-profit organization with mo
24、re than 127,000 members promoting the art, science and practice of mechanical and multidisciplinary engineering and allied sciences. ASME develops codes and standards that enhance public safety, and provides lifelong learning and technical exchange opportunities benefiting the engineering and techno
25、logy community. Visit www.asme.org for more information. The ASME Standards Technology, LLC (ASME ST -LLC) is a not-for-profit Limited Liability Company, with ASME as the sole member, formed in 2004 to carry out work rel.ated to newly commercialized technology. The ASME ST -LLC mission includes meet
26、ing the needs of industry and government by providing new standards-related products and services, which advance the application of emerging and newly commercialized science and technology and providing the research and technology development needed to establish and maintain the technical relevance
27、of codes and standards. Visit www.stllc.asme.org for more information. v STP-PT-046 Review of Safety Considerations for Natural Gas Pjpeline Block Valve Spacing ABSTRACT The goals of this report are I) to examine prior studies that have been conducted to define the relationship of block valves on ga
28、s transmission pipelines to public safety, 2) to assess the relationshjp of valve spacing and valve operator type on public safety and 3) to evaluate if valve spacing/valve operator type, or valve location can improve public safety. The presence, location and spacing of main line block valves were f
29、ound to have no impact on the likelihood of a failure and only a small reduction in the consequences of a failure on a natural gas transmission pipeline. Even if the valves are closed at the start of an incident, calculations and historical records confirm that natural gas pipelines require more tha
30、n an hour to depressurize. The most severe consequences to the public occur in RCAs in the first 30 seconds after incident initiation. The addition of automatic or remote closing valves was thought to potentially reduce the consequences of gas transmission incidents in about 20 percent of the seriou
31、s NTSB incidents reviewed. This review found that all of the prior research studies, the examination of the PRMSA incident database and the examination of NTSB gas transmission pipeline incidents indicate that main line block valve spacing on natural gas transmission pipelines is not related to publ
32、ic safety. Valves are useful for maintenance and line modification but they do not control or affect public safety as the injuries and fatalities on gas transmission pipelines generally occur during the first 30 seconds after gas has been released from a pipeline. The NTSB incidents reviewed indicat
33、ed that it took at least an hour after the rupture occurred for the natural gas to decompress and exhaust from the pipeline. This exists because a natural gas pipeline is not like a water pipe in a building where, when the valve is closed, the incompressible water stops flowing out of the pipe no ma
34、tter how far the valve is from the pipe opening. Natural gas is compressed to about 70 to 100 atrnospheresa for cross country transmission pipelines and it takes time for the decompression to occur. Calculations indicated that smaller diameter pipelines required longer decompression times; i.e., 12
35、inch (305 mm) diameter pipelines take about twice as long as a 36 inch (914 mm) diameter pipeline of the same length for a worst case full rupture condition due to wall friction effects. The review of the PHMSA incident database revealed that from 2002 to 2009 the total public damage cost does not c
36、orrelate with time to make the area safe (related to the depressurization time) or the concentration of the released gas. The public damage correlates to the proximity of the workers/public and whether the gas ignites, neither of which is controllable for the existing pipeline network The most serio
37、us incidents with large property damage and the potential for injuries and fatalities involved early ignition of the natural gas. The examination of the time to make an area safe revealed that the largest public damage costs were associated with an incident that had a 3.5 hour “time to make the area
38、 safe“ and a total public damage cost of $87.5 million due to the close proximity of a power plant that was damaged by the ignited gas. The longest “time to make the area safe“ was 116.8 hours and there was no public damage reported. Of the eleven highest total PHMSA incident costs, all but one had
39、a “time to make the area safe“ of less than 4 hours. The one exception had a “time to make the area safe“ of 11 hours and had total damage costs of $6.22 million with only $3000 of public damage and no injuries or fatalities. The review of fourteen NTSB incident reportsb on gas transmission pipeline
40、s indicated that the consequences of the incidents might have been reduced somewhat in 20 percent of the incidents, all of which occurred in RCAs, if the valves had been closed at the instant of gas release. In the incident with the closest spacing between valves (1.25 mjles 2km) twelve fatalities o
41、ccurred and had “ The gas pressure in service pipelines to a house is about 1110 of an aonospbere. b The other NTSB incident reports dealt with liquid pipelines, distribution pipelines, offshore pipelines, compressor stations and other miscellaneous situations. VI Review of Safety Considerations for
42、 Natural Gas Pipeline Block Valve Spacing STP-PT-046 the highest fatality count of all the NTSB incidents reviewed. This indicates that if the gas ignites as it is released, the flame will be present for the full time that it takes to blowdown the natural gas (fuel) in the pipeline. Valves are not s
43、afety items in that in 80% of the NTSB incidents, the injuries and fatalities occurred immediately or within 30 seconds after the first release of natural gas, due to either debris, suffocation or fire. This is based on the calculations indicating that the immediate closure of all block valves would
44、 still have allowed gas to escape for times up to one hour. When parallel pipelines are involved determining which pipeline has experienced the incident may be difficult. This occurred in 20 percent of the NTSB incidents reported. Such parallel pipelines are typically linked together with valves and
45、 open crossovers. The pressure drop on the ruptured line can be difficult to identify because all of the interconnected lines show a pressure decrease due to the open crossoversc. A methodology is needed to help quickly identify which pipeline ruptured when parallel lines exist. Overall, valve spaci
46、ng has not been identified as a safety issue. Valve spacing should be based on efficient operation and maintenance of the pipelines. Under some circumstances, early valve closure may result in some consequence mitigation by reducing the heat flux from a gas ignition and allow the emergency responder
47、s access for rescue in a more expeditious mrumer. This would result from the reduced potential for secondary fires and earlier admission of emergency responders to the affected area. Such earlier closure may be accomplished by automatic or remotely-controlled valves. As explained above, however, eve
48、n instantaneous closure will not prevent the incident or greatly mitigate its consequences. This review found that external force damage remains the primary cause of death and injury. Therefore, the most significant reduction in risk to the public can be achieved by operator application of an integr
49、ity management plan to their pipelines to prevent these third-party damage incidents from occurring. c These open crossover pipelines allow equalization across all (up to seven) parallel lines in the srune right of way. VII STP-PT-046 Review of Safety Considerations for Natural Gas Pjpeline Block Valve Spacing INTENTIONALLY LEFT BLANK V111 Review of Safety Considerations for Natural Gas Pipeline Block Valve Spacing STP-PT-046 1 INTRODUCTION The goal of this report is to: 1. Exam
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