1、API/EI Research Report 545-AVerification of lightning protectionrequirements for above ground hydrocarbon storage tanksFirst edition, October 2009API/EI Research Report 545-AVerification of lightning protection requirements for above ground hydrocarbon storage tanksFirst editionOctober 2009Published
2、 jointly byAPI and ENERGY INSTITUTE LONDONThe Energy Institute is a professional membership body incorporated by Royal Charter 2003Registered charity number 1097899Copyright 2009 by API, andThe Energy Institute, London:The Energy Institute is a professional membership body incorporated by Royal Char
3、ter 2003.Registered charity number 1097899, EnglandAll rights reserved.No part of this book may be reproduced by any means, or transmitted or translated into a machine language without the written permission of the publisher.ISBN 978 0 85293 376 3Published by the Energy InstituteThe information cont
4、ained in this publication is provided as guidance only and while every reasonable care has been taken to ensure the accuracy of its contents, the Energy Institute cannot accept any responsibility for any action taken, or not taken, on the basis of this information. The Energy Institute shall not be
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6、ortland-orGlobal Engineering Documents at (800) 854-7179 or (303) 397-7956w: Electronic access to EI publications is available via our website, www.energyinstpubs.org.uk.Documents can be purchased online as downloadable pdfs or on an annual subscription for single users and companies.For more inform
7、ation, contact the EI Publications Team e: pubsenergyinst.orgVERIFICATION OF LIGHTNING PROTECTION REQUIREMENTS FOR ABOVE GROUND HYDROCARBON STORAGE TANKS: PHASE 1Phase 1:iiiCONTENTS OVERVIEWPageLegal notices and disclaimers ivForeword vPHASE 1Acknowledgements iExecutive summary.iiCul/LT-0234 Review
8、of lightning phenomena and the interaction with above ground storage tanks 1Cul/LT-0235 Review of tank base earthing and test current recommendations43EI-EN2-04 Lightning tests to tank shell/shunt samples55EI-Vis1-01 Visit to oil refinery A 73EI-Vis2-02 Visit to oil refinery B.83EI-TN1-03 Review of
9、burn-through and hot-spot effects on metallic tank skins from lightning strikes . . 93PHASE 2Acknowledgments . i Executive Summary iiCul/LT-0373 Lightning simulation testing to determine the required characteristics for roof bonding cables on external floating roof above ground storage tanks 1Cul/LT
10、-0401 Investigative tests on the lightning protection of submerged shunts with parallel roof bonding cables 31VERIFICATION OF LIGHTNING PROTECTION REQUIREMENTS FOR ABOVE GROUND HYDROCARBON STORAGE TANKS: PHASE 1Phase 1:ivLEGAL NOTICES AND DISCLAIMERSThe information contained in this publication is p
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19、g anyone against liability for infringement of letters patent.No reference made in this publication to any specific product or service constitutes or implies an endorsement, recommendation, or warranty thereof by API or EI.API, EI, AND THEIR AFFILIATES, REPRESENTATIVES, CONSULTANTS, AND CONTRACTORS
20、AND THEIR RESPECTIVE PARENTS, SUBSIDIARIES, AFFILIATES, CONSULTANTS, OFFICERS, DIRECTORS, EMPLOYEES, REPRESENTATIVES, AND MEMBERS SHALL HAVE NO LIABILITY WHATSOEVER FOR, AND SHALL BE HELD HARMLESS AGAINST, ANY LIABILITY FOR ANY INJURIES, LOSSES OR DAMAGES OF ANY KIND, INCLUDING DIRECT, INDIRECT, INC
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22、AGE TANKS: PHASE 1Phase 1:vFOREWORDThis publication has been produced at the request of the API RP 545 Task Force and the EI Electrical Committee. It collates a number of research reports produced by Culham Electromagnetics and Lightning Limited (Culham) who were commissioned to investigate the ligh
23、tning phenomena and the adequacy of lightning protection measures on above ground hydrocarbon storage tanks.Currently international, British and United States standards contain requirements relating to lighting protection; however, these have not been verified through practical, scientific testing.
24、As a result of the work commissioned by the API and EI, a new Recommended Practice (RP) is being developed which will incorporate the results of this investigation.Suggested revisions are invited and should be submitted to the director of standards, API, 1220 L Street, N.W., Washington, D.C. 20005 o
25、r The Technical Department, Energy Institute, 61 New Cavendish Street, London, W1G 7AR. API/EI RESEARCH REPORTVERIFICATION OF LIGHTNING PROTECTION REQUIREMENTSFOR ABOVE GROUND HYDROCARBON STORAGE TANKSPHASE 1VERIFICATION OF LIGHTNING PROTECTION REQUIREMENTS FOR ABOVE GROUND HYDROCARBON STORAGE TANKS
26、: PHASE 1Phase 1:ii EXECUTIVE SUMMARYCUL/LT-0234 REVIEW OF LIGHTNING PHENOMENA AND THE INTERACTION WITH ABOVE GROUND STORAGE TANKSThis document describes the phenomena of lightning, and how it is expected to interact with various types of tank designs, in particular with respect to the problems of h
27、ydrocarbon fires. It draws on the experience of refinery and tank farm visits by the author, including those reported in EI-Vis1-01 Visit to oil refinery A and EI-Vis2-02 Visit to oil refinery B, and other sources. The likely strike points on all types of tanks are described, and the current routes
28、over tanks are shown for the fast and slow lightning components. The shunt/rim seal region for an open top FRT is shown to be the most susceptible to ignitions. Aluminium roof geodesic tanks appear to be the most likely type to suffer hot spots and burn through. The electrical properties of steel as
29、 a material for tanks is described along with descriptions of thermal and voltage sparking. Protection strategies for open FRTs, for roofed over tanks, and LPG tanks are described. Comments are made on the problems associated with petroleum product within the pontoons or on the surface of a floating
30、 roof. An analysis of the operation of the shunt/shell bonding cable suggests that it would play a vital part in suppressing sparking from the continuing current component of lightning, although it would play only a minor role in suppressing sparking from the fast component. The principal USA/UK lig
31、htning protection and oil industry documents are reviewed for their content on lightning protection of tanks.CUL/LT-0235 REVIEW OF TANK BASE EARTHING AND TEST CURRENT RECOMMENDATIONSThe earthing of a storage tank may have important considerations for safety, and protection of instrumentation on the
32、tank, but in practice the tank is likely to be intrinsically well earthed simply by its construction. Even so earthing rods should be (and are) generally used as recommended by international standards. Quality of earthing has little or no significance in storage tank fire protection. The document al
33、so discusses the likely currents which shunts may have to carry (up to 11 kA).EI-EN2-04 LIGHTNING TESTS TO TANK SHELL/SHUNT SAMPLESTests at Culham replicated shunt/shell interfaces and subjected them to conducted lightning-type currents. Even clean steel shunt/shell interfaces sparked. Fast current
34、components produce relatively small sparks, whereas long duration currents produce copious spark showers that are believed to be more hazardous. (In practice good protection against the latter currents can be achieved using a roof bonding cable.) Different shunt materials could also present less of
35、a hazard. Currents in immersed shunts tended to cause an eruption of fluid, due to the arc pressure.VERIFICATION OF LIGHTNING PROTECTION REQUIREMENTS FOR ABOVE GROUND HYDROCARBON STORAGE TANKS: PHASE 1Phase 1:iiiEI-VIS1-01 EI-VIS2-02 VISIT TO OIL REFINERY A VISIT TO OIL REFINERY B Describe the featu
36、res seen during two visits to refineries. Some of the practical difficulties of providing and maintaining lightning protection in the field and over many years are observed and discussed, and some photographs are included.EI-TN1-03 REVIEW OF BURN-THROUGH AND HOT-SPOT EFFECTS ON METALLIC TANK SKINS F
37、ROM LIGHTNING STRIKES Discusses the threat of lightning strikes puncturing steel or aluminium tanks, or of causing internal hot-spots. Aluminium is easily punctured, and so geodesic roofs which use aluminium skins Flashes km yrMean annual flash density (1989-1996)VERIFICATION OF LIGHTNING PROTECTION
38、 REQUIREMENTS FOR ABOVE GROUND HYDROCARBON STORAGE TANKS: PHASE 1Phase 1:4However, in the absence of such data, Equation 1 can be used to give an approximate value. Knowing Ng, the local strike rate, the risk of a strike to any oil processing or storage tanks can be established, essentially as a sim
39、ple calculation of the ground surface area of the plant multiplied by Ng. (There are a few refinements to put into this calculation to allow for ground topology, height of structures etc, but this is the basis of the calculation of strike risk.)Thus the likelihood of lightning damage varies very wid
40、ely all over the world being highest in humid tropical areas, (10 strikes/km/year) and very low in very dry and very cold areas (150 m) those objects have no influence on the occurrence of lightning in the area. The lightning leader on its way down from the cloud is not affected by ground objects un
41、til it is very close to them, say 100 m or less. That is, lightning occurs because of natural processes in the cloud which are virtually unaffected by the ground nature (unless it is mountainous or has very high structures as above). Therefore, in calculating the risk, the presence of the refinery,
42、tank farm etc. makes no difference to the strike rate to that region, so simplifying the risk calculations.Furthermore, lightning conductors only have a very limited range of attractiveness (normally represented as a 45 right circular cone around the conductor, see Figure 3) and although many attemp
43、ts have been made to improve the attractiveness of lightning conductors, none has been shown unequivocally to be more effective than the plain lightning conductor, often called a franklin rod. For example, radioactive rods were once promoted as having extra attractive properties, but the claimed sup
44、er-attractiveness has been discredited (it has been shown by extensive comparative tests and by reference to the physics of radioactive emitters that the devices have no influence on the path of lightning leaders). Radioactive rods have been banned in many countries because the attractiveness is no
45、better than a franklin rod, and because of the potential for causing environmental pollution and health hazards.Figure 3 Cone of protection principle for lightning protection. Objects within the cone shaped volume beneath the dashed lines, all around the vertical pole are within the cone of protecti
46、on, and are at much lower risk from direct strike attachments.45 Ground level 45 1.5 THE LIGHTNING CLOUD APPROACH, INDUCTION CHARGING, AND SPACE CHARGESNormally under fine weather conditions there is a steady but weak vertical electric field at the earths surface. This field is quite weak and very s
47、teady. No actual potential differences can be measured between grounded objects, except those which are electrically isolated (floating in electrical engineering terminology), because the current flow is zero and all VERIFICATION OF LIGHTNING PROTECTION REQUIREMENTS FOR ABOVE GROUND HYDROCARBON STOR
48、AGE TANKS: PHASE 1Phase 1:7objects are grounded i.e. joined together. The charge is distributed all over the ground itself and over grounded objects in a way depending on their shape. Horizontal flat surfaces have a very uniform charge distribution (i.e. a similar surface charge density everywhere).
49、 The highest surface charge occurs on thin pointed objects like church spires, tops of aerials, tops of lightning rods etc. Where the surface charge is highest the local electric field is the highest (and is the point from which an upward ground streamer could rise to meet the descending leader, described in 1.7).Thus in fine weather, a static condition prevails with a steady vertical electric field, virtually no ground currents and a small distributed charge on the ground and on grounded objects and structures. This gives way to a di
