BS-8010

PD 8010-3:2009Licensed Copy: x x, Mott Macdonald, 10/06/2010 06:22, Uncontrolled Copy, (c) BSI BSI British Standards PUBLISHED DOCUMENT Code of practice for pipelines – Part 3: Steel pipelines on land – Guide to the application of pipeline risk assessment to proposed developments in the vicinity of major accident hazard pipelines containing flammables – Supplement to PD 8010‑1:2004 This publication is not to be regarded as a British Standard. See Foreword for further information. NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW raising standards worldwide™ PD 8010-3:2009 Publishing and copyright information PuBliSheD DocumenT The BSi copyright notice displayed in this document indicates when the document was last issued. Licensed Copy: x x, Mott Macdonald, 10/06/2010 06:22, Uncontrolled Copy, (c) BSI © BSi 2008 iSBn 978 0 580 61732 4 icS 23.040.10, 75.200 The following BSi references relate to the work on this standard: committee reference PSe/17/2 Draft for comment 07/30138021 Dc Publication history First published December 2008 Amendments issued since publication Date Text affected PuBliSheD DocumenT PD 8010-3:2009 Contents Licensed Copy: x x, Mott Macdonald, 10/06/2010 06:22, Uncontrolled Copy, (c) BSI Foreword iii introduction 1 1 Scope 3 2 normative references 3 3 Abbreviations 3 4 Risk assessment of buried pipelines – overview 4 5 Failure of hazardous gas or liquid pipelines 5 6 individual risk assessment 13 7 Societal risk assessment 15 8 Factors affecting risk levels 19 Annexes Annex A (informative) Summary of hSe methodology for provision of advice on planning developments in the vicinity of major accident hazard pipelines in the uK 28 Annex B (informative) Failure frequencies for uK pipelines 33 Annex c (informative) example of a site-specific risk assessment 47 Bibliography 53 List of figures Figure 1 – overview of PD 8010-3 2 Figure 2 – event tree for the failure of a hazardous pipeline 6 Figure 3 – Risk calculation flowchart for flammable substances 8 Figure 4 – calculation of pipeline length affecting an individual in the vicinity of a pipeline 14 Figure 5 – Framework for the tolerability of individual risk 15 Figure 6 – Societal risk FN criterion line applicable to 1 km of pipeline 17 Figure 7 – Site-specific pipeline interaction distance 18 Figure 8 – Reduction in external interference total failure frequency due to design factor 22 Figure 9 – Reduction in external interference total failure frequency due to wall thickness 23 Figure 10 – Reduction in external interference total failure frequency due to depth of cover 24 Figure 11 – indicative reduction in external interference total failure frequency due to surveillance frequency (dependent on frequency and duration of unauthorized excavations) 24 Figure A.1 – Planning application process and need for site-specific risk assessment 30 Figure B.1 – Generic predicted pipeline failure frequencies for third-party interference 35 Figure B.2 – FFReQ predictions of total external interference failure frequency for uKoPA pipe cases 39 Figure B.3 – FFReQ predictions of external interference rupture frequency for uKoPA pipe cases 40 Figure B.4 – FFReQ predictions for external interference rupture and leak frequencies for specific diameter and wall thickness cases (per 1 000 km·y) 41 Figure c.1 – Proposed development 47 Figure c.2 – Risk for outside exposure 50 Figure c.3 Societal risk FN curves and PD 8010-3 FN criterion line – proposed development before and after slabbing 50 © BSI 2008 • i an inside back cover and a back cover. and reduction factor due to wall thickness.5 – comparison of external interference failure frequency estimates for example 2 with FFReQ predictions 37 Table B.11 – comparison of external interference failure frequency estimates for example 5 with FFReQ predictions 43 Table B.4 – comparison of external interference failure frequency estimates for example 1 with FFReQ predictions 36 Table B.1 – Failure rates for uK pipelines based on uKoPA data 33 Table B. Rp. ii • © BSI 2008 .72 44 Table B. Rdf.7 – uKoPA pipe cases 38 Table B. Rwt 23 Table 2 – Failure frequency reduction factors. spiked crude and natural gas liquids (nGls) 31 Table B.7 (per 1 000 km·y) 40 Table B.7 (per 1 000 km·y) 41 Table B.8 – FFReQ predictions for total external interference failure frequency for pipe cases defined in Table B.1 – Typical (1 × 10−6) and (0.10 – FFReQ predictions for external interference rupture and leak frequencies for pipe cases defined in Table B. Uncontrolled Copy. for pipeline protection 25 Table A.3 × 10−6) risk distances for ethylene. pages 1 to 56. wall thickness 34 Table B.2 – Failure frequency due to external interference vs.12 – critical defect lengths and equivalent hole diameters for uKoPA pipeline cases operating at a design factor of 0. diameter 34 Table B.13 – Failure frequency due to external corrosion 44 Table B. 10/06/2010 06:22. Mott Macdonald. pages i to iv.15 – Pipeline rupture failure frequency due to due to ground movement caused by natural landsliding 46 Licensed Copy: x x. wall thickness 45 Table B. (c) BSI Summary of pages This document comprises a front cover.3 – Failure frequency due to external interference vs.7 (per 1 000 km·y) 39 Table B.14 – material and construction failure frequency vs.PD 8010-3:2009 PuBliSheD DocumenT List of tables Table 1 – Range of applicability of reduction factor for design factor.6 – comparison of external interference failure frequency estimates for example 3 with FFReQ predictions 37 Table B. an inside front cover.9 – FFReQ predictions for external interference rupture frequency for pipe cases defined in Table B. A list of organizations represented on this committee can be obtained on request to its secretary. explanation and general informative material is presented in smaller italic type. and it is essential that the assessor is able to justify every key assumption made in the assessment and that these assumptions are documented as part of the assessment. © BSI 2008 • iii . judgement has to be employed by the risk assessor at all stages of the assessment. Relationship with other publications PD 8010-3 is a new part of the PD 8010 series. Use of this document As a code of practice. Materials and equipment for petroleum. upright) type. As with any risk assessment. under the authority of Technical committee PSe/17. it should not be quoted as if it were a specification and particular care should be taken to ensure that claims of compliance are not misleading. Mott Macdonald. 10/06/2010 06:22. this part of PD 8010 takes the form of guidance and recommendations. Information about this document This part of PD 8010 includes worked examples and benchmark solutions that can be used as a basis for specific studies. Commentary.e.PuBliSheD DocumenT PD 8010-3:2009 Foreword Publishing information Licensed Copy: x x. Part 3: Steel pipelines on land – Guide to the application of pipeline risk assessment to proposed developments in the vicinity of major accident hazard pipelines containing flammables – Supplement to PD 8010‑1:2004. This part of PD 8010 is intended to support the application of expert judgement. (c) BSI This part of PD 8010 was published by BSi and came into effect on 1 January 2009. and should be read in conjunction with PD 8010-1. Presentational conventions The provisions in this Published Document are presented in roman (i. and does not constitute a normative element. Pipeline transportation systems. Uncontrolled Copy. The final responsibility for the risk assessment lies with the assessor. Any user claiming compliance with this part of PD 8010 is expected to be able to justify any course of action that deviates from its recommendations. it was prepared by Subcommittee PSe/17/2. its recommendations are expressed in sentences in which the principal auxiliary verb is “should”. Part 2: Subsea pipelines. The series comprises: • • • Part 1: Steel pipelines on land. Licensed Copy: x x.PD 8010-3:2009 Contractual and legal considerations PuBliSheD DocumenT This publication does not purport to include all the necessary provisions of a contract. in particular: • • the health and Safety at Work etc Act 1974 [2]. (c) BSI Compliance with a Published Document cannot confer immunity from legal obligations. 10/06/2010 06:22. iv • © BSI 2008 . amended 1999 [3]. Mott Macdonald. the management of health & Safety at Work Regulations 1992. users are responsible for its correct application. Attention is particularly drawn to the Pipelines Safety Regulations 1996 [1] and to the requirements for risk assessments in uK health and safety legislation. Uncontrolled Copy. 10/06/2010 06:22. clause 5 and Annex F provide guidance on the route selection and location of new pipelines in populated areas in terms of the acceptable proximity to significant inhabited areas. risk reduction factors to be applied for mitigation methods. developers and any person involved in the risk assessment of developments in the vicinity of existing major accident hazard pipelines. This part of PD 8010 provides guidance for the risk assessment of developments in the vicinity of major hazard pipelines containing flammable substances notified under the Pipelines Safety Regulations 1996 [1]. conducting site-specific risk assessments. but the principles of the risk calculation are generally applicable. Uncontrolled Copy. benchmark results for individual and societal risk levels. clause 5 classifies locations adjacent to pipelines into location classes 1. it is based on the established best practice methodology for pipeline risk assessment. and is intended to be applied by competent risk assessment practitioners. The general approach to the risk assessment process follows the stages outlined in PD 8010-1:2004. 2 and 3 according to population density and/or nature of the immediate surrounding area. The guidance is specific to the calculation of safety risks posed to developments in the vicinity of uK major accident hazard pipelines. The present part of PD 8010 includes recommendations for: • • • • • • determining failure frequencies. An overview of the document content is given in Figure 1. © BSI 2008 • 1 . standard assumptions to be applied in the risk assessment methodology for land use planning zones. For significant developments or infringements the pipeline operator might wish to carry out risk assessment using societal risk analysis for comparison with suitable risk criteria to allow the operator to assess whether the risks remain within acceptable limits. The guidance in this part of PD 8010 is provided for the benefit of pipeline operators.PuBliSheD DocumenT PD 8010-3:2009 Introduction Licensed Copy: x x. (c) BSI PD 8010-1:2004. The use of such risk assessments to determine the acceptability of developments in accordance with land use planning applied in Great Britain is discussed in Annex A. clause 7 describes the application of societal risk. Annex e. and includes a recommended FN criterion line. The guidance does not cover environmental risks. consequence modelling. local planning authorities. it does not cover toxic substances which are also notified under these Regulations. Mott Macdonald. PD 8010-3:2009 Figure 1 Overview of PD 8010-3 Scope Safety risks caused by flammable substances only Clause 1 PuBliSheD DocumenT Licensed Copy: x x, Mott Macdonald, 10/06/2010 06:22, Uncontrolled Copy, (c) BSI Risk assessment of buried pipelines Clause 4 Consequences: Prediction Probability of ignition Thermal radiation and effects 5.3 5.4 Failure of a gas or liquid pipeline Event tree Prediction of failure frequency 5.1 5.2, 8.2 Annex B 5.5 Calculation of risk and risk criteria Individual Societal Clause 6 Clause 7 Factors affecting risk levels Failure frequency Failure frequency reduction factors Implementation of risk mitigation measures Clause 8 8.1 8.2, Annex B 8.3 Supporting annexes: Summary of HSE methodology for the provision of land use planning advice in the vicinity of UK MAHPs Failure frequencies for UK pipelines Example of a site-specific risk assessment Annex A Annex B Annex C 2 • © BSI 2008 PuBliSheD DocumenT PD 8010-3:2009 1 Scope Licensed Copy: x x, Mott Macdonald, 10/06/2010 06:22, Uncontrolled Copy, (c) BSI This part of PD 8010 provides a recommended framework for carrying out an assessment of the acute safety risks associated with a major accident hazard pipeline (mAhP) containing flammable substances. it provides guidance on the selection of pipeline failure frequencies and the modelling of failure consequences for the prediction of individual and societal risks. The principles of this part of PD 8010 are based on best practice for the quantified risk analysis of new pipelines and existing pipelines. it is not intended to replace or duplicate existing risk analysis methodology, but is intended to support the application of the methodology and provide recommendations for its use. This part of PD 8010 is applicable to buried pipelines on land that can be used to carry category D and category e substances that are hazardous by nature, being flammable and therefore liable to cause harm to persons. The guidance does not cover environmental risks. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. PD 8010-1:2004, Code of practice for pipelines – Part 1: Steel pipelines on land iGe/TD/1 edition 4:2001, Steel pipelines for high pressure gas transmission1) 3 Abbreviations For the purposes of this part of PD 8010, the following abbreviations apply. AlARP FFReQ hSe lFG as low as reasonably practicable methodology recommended by uKoPA for prediction of pipeline failure frequencies due to external interference health and Safety executive liquefied flammable gases, including liquefied petroleum gases (lPG), liquefied natural gas (lnG), and natural gas liquids (nGl) major accident hazard pipeline maximum allowable operating pressure minimum distance to occupied building probability of failure specified minimum yield strength mAhP mAoP mDoB PoF SmYS 1) institution of Gas engineers and managers (formerly institution of Gas engineers) (iGe) standards are available from the institution of Gas engineers and managers, charnwood Wing, holywell Park, Ashby Road, loughborough, leicestershire le11 3Gh. © BSI 2008 • 3 PD 8010-3:2009 Tdu TS Vce thermal dose units tensile strength vapour cloud explosion PuBliSheD DocumenT uKoPA united Kingdom onshore Pipeline operators Association Licensed Copy: x x, Mott Macdonald, 10/06/2010 06:22, Uncontrolled Copy, (c) BSI 4 Risk assessment of buried pipelines – Overview The failure of a pipeline containing a flammable substance (which can be a gas, a liquid, a dense-phase supercritical fluid or a two- or three-phase fluid) has the potential to cause serious damage to the surrounding population, property and the environment. Failure can occur due to a range of potential causes, including accidental damage, corrosion, fatigue and ground movement. The acute safety consequences of such a failure are primarily due to the thermal radiation from an ignited release, whether directly (from the main release) or indirectly (from secondary fires). Quantified risk assessment applied to a pipeline involves the numerical estimation of risk by calculation resulting from the frequencies and consequences of a complete and representative set of credible accident scenarios. in general terms, a quantified risk assessment of a hazardous gas or liquid pipeline consists of the following stages: a) b) c) gathering data (pipeline and its location, meteorological conditions, physical properties of the substance, population) (5.1); prediction of the frequency of the failures to be considered in the assessment (5.2); prediction of the consequences for the various failure scenarios (5.3), including: • • • • • d) calculation of release flow rate; estimation of dispersion of flammable vapours; determination of ignition probability; calculation of the thermal radiation emitted by fire in an ignited release; quantification of the effects of thermal radiation on the surrounding population; estimation of individual risk (clause 6); estimation of societal risk (clause 7); calculation of risks and assessment against criteria: • • e) identification of site-specific risk reduction measures (clause 8). Pipeline failure frequency is usually expressed in failures per kilometre year or per 1 000 kilometre years (km·y). Failure frequency should be predicted using verified failure models and predictive methodologies [4, 5, 6, 7], or otherwise derived from historical incidents that have occurred in large populations of existing pipelines that are representative of the population under consideration, as recorded in recognized, published pipeline data. Various factors may then be taken 4 • © BSI 2008 Uncontrolled Copy. and predictive models based on operational data are available [4. fatigue and ground movement. leaks are defined as fluid loss through a stable defect. corrosion. Pipelines present an extended source of hazard. In the UK.1 General Failure of a hazardous gas or liquid pipeline has the potential to cause damage to the surrounding population.PuBliSheD DocumenT PD 8010-3:2009 into account for the specific pipeline design and operating conditions to obtain the failure rate to be applied. ruptures are defined as fluid loss through an unstable defect which extends during failure. so the release area is normally equivalent to two open ends. the full length over which a pipeline failure could affect the population or part of the population should be taken into account in the risk assessment. and can pose a risk to developments at different locations along their route. third‑party interference is the dominant mode. The consequences of failure are primarily due to the thermal radiation that is produced if the release ignites. including accidental damage. This can be caused directly. NOTE Predictive models can be generated for all damage types and failure modes depending on the data available. Typical event trees for the failure of gas and liquid pipelines are shown in Figure 2. NOTE 1 For detailed explanation of some of the consequence models which have been applied by HSE to derive existing Land Use Planning zones. 5 Failure of hazardous gas or liquid pipelines 5. © BSI 2008 • 5 . 6. NOTE 2 Spray fire is equivalent to a jet fire from a liquid line. Fireballs are technically not possible but vapour cloud explosions (VCEs) can occur where the liquid in the pipeline produces heavier‑than‑air vapour. 9. the results validated using experimental data at various scales up to full or comparison with recognized solutions. This should take into account people both outdoors and indoors. Mott Macdonald. failure frequency due to other damage types is derived using historical data [8. as well as comparison of model predictions with the recorded consequences of real incidents. property and the environment. Failure can occur due to a range of potential causes. 10/06/2010 06:22. 10]. see [11] to [14]. resulting in a fireball. or indirectly by igniting secondary fires. The escaping fluid can ignite. Licensed Copy: x x. The results of a consequence analysis should take into account all feasible events. Where a length of pipeline over which a location-specific accident scenario could affect the population is associated with a specific development. 7]. crater fire or jet fire which generates thermal radiation. In general. (c) BSI The consequences of pipeline failures should be predicted using verified mathematical models. in terms of the effect distance (radius) over which people are likely to become casualties. Failure of a high pressure pipeline can occur as a leak or rupture. This length is known as the interaction distance (see clause 6 and clause 7). illustrative event trees for the failure of a hazardous pipeline are shown in Figure 2. 5. PD 8010-3:2009 Figure 2 Event tree for the failure of a hazardous pipeline Immediate ignition Delayed local ignition Delayed remote ignition PuBliSheD DocumenT Licensed Copy: x x. if the vapour cloud could engulf any confined or congested region. Uncontrolled Copy. only credible for heavier than air gases. e) F) c) 6 • © BSI 2008 . D) There will be a limited flash fire which is not normally considered separately. F) Flash fires B). 10/06/2010 06:22. Mott Macdonald. E) + crater fire No ignition Fireball + jet fires F) Jet fires D). extent/distance will depend on ground permeability. it is also possible for the release from one pipe end is obstructed and the other unobstructed. E) + jet fires No ignition Impacted jet (crater) fire Impacted jet (crater) fire D) No ignition N N Puncture Y Y N Jet fire Jet fire No ignition N N b) event tree for a gas pipeline failure A) B) Ground/water pollution is also likely to occur. (c) BSI Y Rupture N Pipe failure Y Puncture N Y Y N N Y Y N N Fireball + spray + pool fire Pool fire A) B) VCE or flash fire Running fires C) VCE B) or flash fire Ground/water pollution C) Spray + pool fire Pool fire A) Running fire C) Ground/water pollutionC) a) event tree for a liquid pipeline failure Release obstructed Immediate ignition Y Y Y N Rupture Y N N Y Y N Pipe failure Y Y Y N Y N N Delayed local ignition Delayed remote ignition Fireball + crater fire Crater fire D) Flash fire B). the possibility of a Vce should be considered. NOTE 4 In the case of natural gas. NOTE 3 For large diameter pipelines (i. determination of ignition probability. population). (c) BSI if immediate ignition of a fluid release occurs. calculation of thermal radiation emitted by fire in an ignited release. The extent of such gas clouds depends on prevailing weather conditions at the time of release. as the release has a large momentum flux at the source and this normally has a significant vertical component. calculation of risks. it is normally assumed that the ends of the failed pipe remain aligned in the crater and the jets of fluid interact. then the sensitivity of the location to directional releases reviewed. it is possible. for one or both pipe ends to become misaligned and produce one or two jets which are directed out of the crater and are unobstructed. meteorological conditions. prediction of consequences: • • • • d) calculation of release flow rate.g. >300 mm) this is a standard assumption. the standard case would normally be assessed. quantification of the effects of thermal radiation on the surrounding population. the transition to a low momentum (passive) release does not occur until the released natural gas has dispersed (is diluted) below the lower flammability limit. e. in general terms. at a location close to a bend or for a small diameter pipeline.PuBliSheD DocumenT PD 8010-3:2009 For the assessment of a rupture release of a gaseous fluid. © BSI 2008 • 7 . and areas of congestion or confinement. 10/06/2010 06:22. the location of possible sources of ignition. For gases or vapours that are heavier than air.e. Mott Macdonald. the possibility of a flash fire or Vce should be taken into account. For the duration of the release relevant to the risk analysis. Where such a location or pipe is being assessed. A more detailed assessment might then be required which would go beyond the standard methodology described in this part of PD 8010. making their assessment more complex. The modelling of the consequences and effects of Vces are not discussed in detail in this part of PD 8010. this scenario is not usually considered. Such releases can produce directional effects. a fireball can be produced which lasts for up to 30 s and is followed by a crater fire. a quantified risk assessment of a hazardous gas or liquid pipeline consists of four stages: a) b) c) input of data (pipeline and its location. prediction of failure mode and frequency. physical properties of the substance. if ignition is delayed by 30 s or more. The stages of pipeline risk assessment are represented in Figure 3. or form cold heavier-than-air gas clouds when released. it is assumed that only a crater fire (jet obstructed) or a jet fire (jet unobstructed) will occur. Uncontrolled Copy. Licensed Copy: x x. pipeline operational parameters – maximum allowable operating pressure. wall thickness. and any other data required to apply a fracture mechanics model or to calculate the design factor. location details. toughness (or charpy impact value).PD 8010-3:2009 Figure 3 Risk calculation flowchart for flammable substances PuBliSheD DocumenT Licensed Copy: x x. material properties. location of drainage channels and ditches). The data should be obtained from engineering records. location classification (class 1. depth of cover. grade (SmYS. the pipeline operating limits in the pipeline notification and an examination of the pipeline surroundings. operational parameters Location details (area category. protection etc) Population details Fluid properties Meteorological conditions Determine failure rate data for leaks and ruptures due to: External interference + Corrosion + construction + defects Material & Ground movement + Other Failure frequency Release rate Calculate failure frequency Determine consequences based on: + Dispersion + Ignition + Type of fire Consequences Thermal radiation Individual risk Risk calculations Effects of thermal radiation Societal risk The first stage of the risk assessment process is to gather the required data to characterize the pipeline. 10/06/2010 06:22. pipeline material properties – e. ground slope direction.g. Uncontrolled Copy. (c) BSI Input data Pipe geometry. topographical information in any region of interest (e. class 2). operating data. Mott Macdonald. • • • 8 • © BSI 2008 . including: • • length and route of the pipeline to be assessed.g. its contents and the surrounding environment. pipeline shutdown period. TS). temperature. These data are used at various stages of the analysis. The principal input data required for a pipeline quantified risk analysis are: • • pipeline geometry – outside diameter. 10/06/2010 06:22. including stress corrosion cracking (Scc) and alternating current (Ac)/direct current (Dc) induced corrosion]. information about wind speeds and directions. from vapour to liquid (or vice versa). information about the density and viscosity of the fluid as a function of pressure. operational errors etc. details about ambient temperatures and pressures at the location of interest. information to characterize any phase change within the fluid. temperature. and justifications for any additional assumptions to be applied locally should be documented. such as fatigue. including: • • • atmospheric conditions.g. from thermodynamic charts.g. Where additional pipeline protection such as slabbing is to be taken into account. the design and installation should be assessed to ensure that additional loading is not imposed upon the pipeline. Uncontrolled Copy. concrete slabbing). (c) BSI physical properties of the material being transported. Licensed Copy: x x. and direct contact should be maintained between the pipe coating and the surrounding soil. A key parameter in setting the boundary between a leak of a stable size and a rupture is the critical defect length. atmospheric humidity. other causes. including traffic density. e. ground movement. road/rail crossing details. in the case of depth of cover.PuBliSheD DocumenT • • • • • • • • • depth of cover. tables or rigorous equations of state). Mott Macdonald. © BSI 2008 • 9 .g. population and occupancy levels within the consequence range of the pipeline. • • • The failure modes that should be assessed include leaks of various sizes (punctures) and line breaks (ruptures). development and building categories in the vicinity and their distance from the pipeline.and below-ground pipeline marking. corrosion [internal and external. or to bound the dense phase region. site-specific depths should be taken into account. material or construction defects. river crossings. information to characterize the pressure. 5. details of any above. for example: • • • Any site-specific variations in the data should be assessed.2 Prediction of failure frequency Failure of a pipeline can occur due to a number of different causes such as: • • external interference. volume and temperature behaviour of the fluid throughout the range of conditions relevant to the analysis (e. PD 8010-3:2009 additional protection measures for the pipeline (e. fluid properties (in particular the compressibility) and operating pressure. depending on the release direction and degree • • 10 • © BSI 2008 . outflow from holes is calculated using conventional sharp-edged orifice equations for gas or liquid using a suitable discharge coefficient [13]. the equivalent hole sizes which relate to such defects do not apply to rounded punctures. and by any response to the failure). The release is typically assumed to make a crater into which product is released from both ends of pipe. The critical defect length is significant for external interference. NOTE 3 The maximum possible hole size in high pressure gas pipelines is limited according to the critical defect size. The following aspects should be taken into account: • outflow as a function of time (influenced by failure location. the likelihood of each failure scenario is evaluated and expressed in terms of failure frequency and pipeline unit length. the radiation field produced and the effects of the radiation on people and buildings nearby. Jet fires that are unobstructed can have considerable jet momentum. Uncontrolled Copy. spray or pool fire).e. in a risk assessment. consequence models are needed to predict the transient gas or liquid release rate. This is primarily dependent on the pipeline diameter. where long. 5. and therefore thermal radiation effects which can be greater in the middle and far field distance. material properties.3 Prediction of consequences in the context of pipelines carrying flammable substances. jet. Mott Macdonald. thermal radiation from jet and crater fires. pipeline rupture outflow requires complex calculations involving pressure reduction in the pipeline or two-phase flow for flashing liquids [15. crater. the ignition probabilities.PD 8010-3:2009 PuBliSheD DocumenT The critical defect length is the axial length of a through-wall defect which becomes unstable at the specific pipeline conditions. these should be documented. A rupture release is typically represented by a full bore. resulting in a “lift-off” distance before the flame occurs. (c) BSI leak sizes can range from pinholes up to a hole size equivalent to the critical defect size for the pipeline for external interference failures. wall thickness. for releases that ignite causing immediate hazards to people and property. double-ended break. the characteristics of the resulting fire (i. 16]. NOTE 2 In most cases the risk will be dominated by the rupture scenario. Typical critical hole sizes for high pressure gas pipelines are given in Annex B. Where other data sources are used. thermal radiation from the initial and reducing flow into the fireball if the release is ignited immediately. narrow crack-like defects can occur. and above which a defect will continue to propagate along the pipeline until the defect size becomes equivalent to a rupture. NOTE 1 Critical defect length and equivalent hole diameter applies to external interference where axial. in such cases. Typical failure frequencies for uK mAhPs are given in Annex B. crack‑like defects can occur. the crack opening area through which the fluid release occurs is transposed into an equivalent hole size which can be used for release calculations. fireball. upstream and downstream boundary conditions. Licensed Copy: x x. 10/06/2010 06:22. or stable holes due to corrosion or material and construction defects. flash. Additional aspects to be taken into account for pressurized liquid releases include: • • • spray fires. • • There is considerable evidence from actual events and research work that immediate ignition events involving sudden large releases of flammable gases can cause a fireball to occur. spillage rate and duration of release from a liquid pipeline affecting the local area and possibly causing a spray or pool fire. For generic calculations. • other consequences that are generally found to have a negligible effect on risk compared to fire effects include: • • • release of pressure energy from the initial fractured section. • Licensed Copy: x x. the type of ground environment. crater fires can be modelled as large cylindrical flames starting at ground level having thermal radiation effects progressively reducing through near. and flammable liquids containing lFGs such as spiked crude oil. immediate and delayed ignition pool fires. middle and far distance. In the UK. wind speed. with pressure being maintained from the upstream compressor. This calculation requires an estimate of the initial and steady state release rates and an estimate of the inventory of the pipeline network which is discharging to the release point. When modelling either crater fires or unobstructed jet fires following a rupture. release of flammable liquids into water courses and the potential for running fires. the transient nature of the release should be modelled. NOTE Weather category. and possible ignition points in downwind areas. as well as wind speed. Mott Macdonald. can also cause a fireball to occur. because this affects the crater fire and jet fire tilt and extent of the flash fire and hence the resulting radiation effects downwind. the conventional assumption is that night‑time weather is modelled as Pasquill Category F and windspeed 2 m/s. humidity – this affects the proportion of thermal radiation absorbed by the atmosphere. pump or © BSI 2008 • 11 . including topography where appropriate. into which a liquid is released. Uncontrolled Copy. missiles generated from overlying soil or from pipe fragments. The consequence model should also take into account: • • wind direction – required for a site-specific risk assessment where wind direction will affect the populated area non-symmetrically around the location of the fire. Typical fireball burn times are 10 s to 30 s depending on pipeline diameter and pressure.PuBliSheD DocumenT PD 8010-3:2009 of wind tilt. large releases of liquefied flammable gases. and daytime as Category D and windspeed 5 m/s. 10/06/2010 06:22. pressure generated from combustion during the initial phase if the release is ignited immediately. (c) BSI extent of the area covered by a flammable gas cloud causing a possible flash fire downwind of the release. the typical assumption made is that the break occurs half-way between compressor or pump stations (or pressure regulating station). also affects gas dispersion for flash fire prediction. the effects are dependent on direct thermal radiation from the flame to the exposed person or building. class 2. and drain-down of adjacent sections of the pipeline. There are two main methods of calculation in use: the view factor method. outside the flame envelope. The amount released from a liquid pipeline is a function of the time taken to stop pumping. The consequences predicted by such models are increased directionally.] are available for deriving probability of ignition for various situations (class 1. The probability of flash fires is considered low. more elaborate models are possible with different angles of flame. The various ignition possibilities such as immediate. which assumes a surface emissive power from the flame. 14. A vapour cloud can drift further in night-time conditions (category F2) than daytime (category D5). being dependent on the release source and the distribution of ignition sources in the vicinity of a pipeline.). Small to medium holes can cause sprays and the hazard distance from spray fires can be significant. roads. Probabilities used by hSe are discussed in Annex A. and whether ignition occurs immediately or is delayed. the release can be considered to be steady state. The ignition causes the fire to flash back to the source of release and then to cause a jet. When modelling jet fires from punctures. the release rate is often dictated by the pumping rate at the point of release. are drawn out logically on an event tree (see Figure 2) to obtain overall probabilities. large holes (>50 mm) in high pressure pipelines are likely to release the full pumping rate. 12 • © BSI 2008 . For non-flashing liquid releases from pipelines. which assumes that all the energy is emitted from one (or several) point sources within the flame. depending on hole size. delayed and obstructed or unobstructed. The consequence model usually assumes a vertical wind-blown jet flame. and the point source method. Spray releases occur when a flammable liquid is released at high velocity through a punctured pipeline. depressurization of the pipeline.PD 8010-3:2009 PuBliSheD DocumenT pressure reduction station and no reverse flow (with depressurization) occurring at the downstream check valve or regulator. railways etc. so the consequences of large holes are similar to pipeline rupture. Thermal radiation is calculated from the energy of the burning material. Flash fires occur when a plume of unignited heavier-than-air gas or vapour drifts downwind before finding a source of ignition. crater or pool fire. 5. it is usually assumed that immediate ignition occurs within 30 s.5 Thermal radiation and effects Fatal injury effects are assumed for cases where people in the open air or in buildings are located within the flame envelope. urban. The energy from the fireball pulse is usually calculated using the view factor method. and delayed ignition occurs after 30 s. Licensed Copy: x x. but the conditional probability is reduced. (c) BSI 5. extensive references [12.4 Probability of ignition The risks from a pipeline containing a flammable fluid depend critically on whether a release is ignited. Mott Macdonald. 10/06/2010 06:22. Uncontrolled Copy. Generic values for ignition probability can be obtained from data from historical incidents and these are product-specific. for example. The prediction of the thermal radiation effects is required to be summed through the event. The risks from the various failure scenarios should be collated and the individual risk profile at various distances plotted on a graph. a number of factors should be taken into account. The cumulative thermal dose is then calculated. 10/06/2010 06:22. location and types of buildings. try to escape. and indoors within the piloted ignition distance.PuBliSheD DocumenT PD 8010-3:2009 The thermal radiation effect at distances from the failure. a value of 1% lethality. operating pressure. is summed through the complete fire event to determine the effect on people and property in terms of the piloted ignition distance for buildings. From © BSI 2008 • 13 . and the distance for which escape to safe shelter is possible. The thermal dose unit (tdu). individual risk contours for pipelines of given geometry. etc. 1 kW/m2 is reached. including escape speed for people outside running away from the fire. NOTE 2 Due to the uncertainties in the effects of thermal radiation. experimental and other data indicate that thermal radiation dose levels can have differing effects on a population depending on individual tolerance to such effects. is sometimes associated with such predictions (see Annex A). The distance from the pipeline at which a particular level of risk occurs depends upon the pipeline diameter. daytime or night-time. in kilowatts per square metre (kW/m2). (c) BSI NOTE 1 W is not independent of time for a transient release. and is normally summed over exposure until safe shelter. calculated as the radiation dose. The variation of effects has been estimated from burn data for human beings which suggests that the radiation level causing a significant likelihood of fatal injury in an average population is 1 800 tdu. The thermal radiation effect from crater fires and jet fires is generally calculated by assuming that all persons outdoors. frequency of failure and failure mode. the dose limit or a cut‑off thermal radiation level of. Mott Macdonald. This level of thermal dose is often used in risk assessments. the escape distance for people out of doors. populations indoors and outdoors. in order to assess safe escape distance. The progression of a fire through the different stages of the event can be complex. in seconds (s). equivalent to 1 000 tdu to 1 050 tdu as a threshold of dangerous dose or worse. and the distance from the fire at which escape is possible without exceeding a threshold dose. Licensed Copy: x x. Uncontrolled Copy. is defined as: tdu = W 4/3t where: t W is time. is the intensity of thermal radiation. hence the event might need to be subdivided into its stages and the effects summed later. 6 Individual risk assessment individual risk is a measure of the frequency at which an individual at a specified distance from the pipeline is expected to sustain a specified level of harm from the realization of specific hazards. material properties and operating conditions form lines parallel to the pipeline axis. This can prove difficult to achieve in a continuous way. radius R Pipeline interaction distance for observer at location 1 R2 − D2 criteria for individual risk levels have been determined by the hSe in the uK. the risk levels are known as the risk transect. including high-pressure pipelines transporting defined hazardous substances based on individual risk levels. Mott Macdonald.PD 8010-3:2009 PuBliSheD DocumenT this plot it is possible to identify the risk of a specified effect (e. 10/06/2010 06:22. land use planning zones applied to major accident hazard pipelines in the uK defined by hSe are discussed in Annex A. the consequences are circular. the interaction distance (see clause 4) is calculated as shown in Figure 4. The interaction distance shown can be multiplied by the pipeline failure frequency. (c) BSI For a simple model where windspeed conditions are zero. at distance D from the pipeline circular effect distance/consequence distance. Uncontrolled Copy. fatality or dangerous dose) to an individual at a given distance from the pipeline. Figure 4 Calculation of pipeline length affecting an individual in the vicinity of a pipeline 1 2 3 4 1 2 4 a) interaction distance = 2 × radius of circle = length of pipeline that could affect observer R D R 4 b) interaction distance = 2 × Key 1 2 3 4 location of observer. Shown in cross-section perpendicular to the pipeline. is shown in Figure 5.g. hSe sets land use planning zones for major hazard sites. 14 • © BSI 2008 . the probability of ignition and the probability of effect to obtain the risk at any distance from the point of release. The framework for the tolerability of risk which gives individual risk values for the defined regions. Licensed Copy: x x. published by hSe [17]. in which a constant distributed population in the vicinity of a pipeline is assumed. workplaces such as call centres. hospitals and old people’s homes are classed as sensitive developments because of the increased vulnerability of the population groups involved to harm from thermal radiation hazards and the increased difficulty in achieving an effective response (e. or site-specific. Societal risk is of particular significance to pipeline operators because the location of pipelines might be close to populated areas. 10/06/2010 06:22. Site-specific assessments are needed for housing developments. The original routing of the pipeline is expected to have taken into account the population along the © BSI 2008 • 15 . Mott Macdonald. and any developments involving sensitive populations. (c) BSI Increasing individual risks and societal concerns 1 x 10 (Worker) 1 x 10 (Public) -4 -3 Tolerable if ALARP region 1 x 10 (All) -6 Broadly acceptable region 7 Societal risk assessment Societal risk is the relationship between the frequency of the realization of a hazard and the resultant number of casualties. so the impact of multiple fatality accidents on people and society in general should be taken into account. rapid evacuation) to mitigate the consequences of an event such as a pipeline fire.g. and therefore it is more appropriate that societal risk is used to assess the acceptability of pipeline risk. commercial and leisure developments. The hazards associated with pipelines tend to be high consequence low frequency events. building layouts and population distributions are taken into account. in which the details of particular developments.PuBliSheD DocumenT Figure 5 Framework for the tolerability of individual risk Unacceptable region PD 8010-3:2009 Licensed Copy: x x. Developments such as schools. Societal risk can be generic. industrial premises. The calculation is carried out by assessing the frequency and consequences of all of the various accident scenarios which could occur along a specified length of pipeline. Uncontrolled Copy. 5 persons per hectare) adjacent to each 1 km length of pipeline. up to 2. A typical medium-sized comAh site might typically have a perimeter exposing risk to the public outside the site of 2 km. The “tolerable if AlARP” region lies between these two lines. For application to pipelines. Societal risk assessment allows these developments to be assessed against the original routing criteria where a location class 1 area has a population density of up to 2. based on the following which enables criteria for case societal risk to be defined for the FN diagram. Uncontrolled Copy. so the equivalent length of pipeline exposing the same risk to the public is 1 km. in effect the FN criterion line represents the upper limit of the cumulative frequency of multiple fatality accidents in any 1 km section of a pipeline route assumed to be acceptable as implied by conformity to PD 8010-1. but infill and incremental developments might increase the population in some sections of the route. Licensed Copy: x x. the −1 slope line (see Figure 6). and parallel to. Developing criteria for tolerability for hazards giving risk to societal concerns is not straightforward. in the assessment of societal risk. logN plot. it is therefore suggested that the FN criterion line given in Figure 6 should be used to assess societal risk due to mAhPs. This allows the assessment of the residual risk from a specific pipeline to be compared with the risk from the average class 1 pipeline population density (i. extending out to the hazard distance of the worst case event from the pipeline.e. it is necessary to specify a length over which the frequency and consequences of all accident scenarios are collated. Subsequently hSe’s hazardous installations Directorate have proposed [18] criteria for major hazard sites in the context of the control of major Accident hazards Regulations 1999 [19] (comAh). (c) BSI 16 • © BSI 2008 . in the absence of product-specific risk curves. equivalent to a significant likelihood of causing fatality. 10/06/2010 06:22.PD 8010-3:2009 PuBliSheD DocumenT route. showing the cumulative frequency F (usually per year) of accidents causing N or more casualties. Reference [17] describes the derivation of a societal risk limit from a study of canvey island and subsequently endorsed by the hSc’s Advisory committee on Dangerous Substances in the context of major hazards transport. hSe proposed that the risk of an accident causing the death of 50 people or more in a single event should be regarded as intolerable if the frequency is estimated to be more than one in five thousand per annum [17]. When the societal risk has increased significantly. Therefore the same FN risk curves could be applied to 1 km of pipeline. The criterion for societal risk is expressed graphically as an FN criterion line. where the population is assumed to be located in a strip centred on the pipeline from the mDoB. the methodology applied should be consistent with the risk limit in terms of the length of pipeline considered. From this. the pipeline operator might then need to consider justifiable mitigation measures to reduce the risk. The unacceptable region is taken as the region above the line of slope −1 through the defined point on the logF v. and the broadly acceptable region is taken as the region below a line two orders of magnitude below.5 persons per hectare. Mott Macdonald. The FN criterion line shown here is applicable to assessments carried out using 1 800 tdu. Assessment of the societal risk in accordance with the FN criterion line might still allow such variations to be classified as an acceptable situation not requiring any upgrading of the pipeline to reduce the risk. An example of this is the FN envelope presented in IGE/TD/1:2001. The methodology for assessing risk scenarios.2) Licensed Copy: x x.E-03 1. This is defined as the site interaction distance.PuBliSheD DocumenT PD 8010-3:2009 NOTE 1 The areas below the FN criterion line in Figure 6 represent broadly acceptable risk levels and therefore relevant good practice in both location classes 1 and 2. Figure 20 for natural gas. with clusters of population at some locations.E-04 1.E-10 1 10 Number of casualties B A 100 1 000 Key A B Broadly acceptable Tolerable if AlARP Population density tends to vary along a pipeline route. 10/06/2010 06:22. location classification and/or demonstration of AlARP.E-09 1. e. the maximum distance over which the worst case event could affect the population in the vicinity should be determined.E-05 1.g. This envelope curve represents the boundary for a series of curves applying to numerous different pipeline cases which are acceptable in accordance with IGE/TD/1. Mott Macdonald. Figure 6 Societal risk FN criterion line applicable to 1 km of pipeline 1. (c) BSI NOTE 2 In some cases. a product‑specific criterion line might be available for assessing societal risk tolerability. failure cases. 2) operators can apply this approach as part of demonstration of ongoing compliance with the recommendations given in PD 8010-1 for population density.E-07 1. © BSI 2008 • 17 .E-02 Frequency (per year) of N or more casualties 1. Uncontrolled Copy. which is based on the application of previous editions of IGE/TD/1.E-06 1. the site length combined with the maximum hazard range within which the population is to be assessed (see Figure 7). To carry out a site-specific societal risk assessment.E-08 1. failure frequencies and consequences is similar to that used to obtain individual risk levels. Mott Macdonald. 18 • © BSI 2008 . Uncontrolled Copy. giving a site-specific FN curve. for heavier‑than‑air gases and liquids. Licensed Copy: x x. The frequency. The FN criterion line given in Figure 6 represents broadly acceptable risk levels for pipeline operation. Alternatively. the topography. As the Fn criterion line relates to a 1 km length of pipeline. then further mitigation might be required to reduce risks to acceptable/negligible levels if this is economically justifiable in terms of the requirement to demonstrate that the risks are AlARP. 10/06/2010 06:22. N. of N or more people being affected is determined. f. the proposed development might be deemed unacceptable in that the societal risk levels are too high. which are then ordered with respect to increasing number of casualties. and the number of people. if the calculated site-specific FN curve falls below the FN criterion line. if the site-specific FN curve is close to or above the FN criterion line. the presence of directional effects and. is determined for each scenario at each specific location. and effect area for each accident scenario should then be assessed along the site interaction distance. (c) BSI Figure 7 Site-specific pipeline interaction distance 1 2 Key 1 2 3 3 maximum hazard range within which population is to be assessed Pipeline Site interaction distance existing buildings new buildings NOTE 3 The shape and dimensions of the site‑specific hazard range is dependent upon the characteristics of the released fluid. the site-specific FN curve is obtained by factoring risk values by a factor equal to 1 km divided by the site interaction distance. the risk levels to the adjacent population are considered broadly acceptable. who would be affected. and the actual population density within the area defined by the pipeline section and the interaction distance (see Figure 7) determined. N. This provides a number of fN pairs. and the cumulative frequency. The site-specific FN curve should be compared with the FN criterion line in Figure 6.PD 8010-3:2009 PuBliSheD DocumenT The accident scenarios which are relevant for the pipeline section within the site interaction distance should be listed. F. and these have the greatest effect on risk from pipelines. landslide) or artificial (excavation. When calculating the overall risk it is necessary to combine the individual FN pairs from each assessment.1 Individual factors influencing pipeline failure frequency All the key damage mechanisms should be taken into account when carrying out a risk assessment. Uncontrolled Copy. corrosion. due to overpressure. When assessing multiple pipelines. Assessment of pipeline failure databases shows that external interference and ground movement dominate pipeline rupture rates. The failure rate for external interference is influenced by a number of parameters. • if pipeline interaction is considered likely then expert opinion should be obtained on how to model the combined failure frequencies and product outflow. inspection. including the pipeline wall thickness.g. The pipelines should be individually assessed and the risk from each summed to obtain overall individual risk transects and societal risk FN curves. the risk from this pipeline should be included in the assessment if it is considered that: • Licensed Copy: x x. This data should then be factored by a value equal to 1 km divided by the sum of the interaction lengths for each pipeline considered. maintenance and operational controls in accordance with PD 8010-1:2004. The failure rate for natural ground movement and for artificial ground movement depends upon the susceptibility to landsliding or © BSI 2008 • 19 . and compared to the FN criterion line. the development site under consideration is within the interaction distances of more than one major accident pipeline in the specified area. operational. (c) BSI the pipelines could interact such that a failure on one pipeline would lead to the failure of the other pipeline. 10/06/2010 06:22. ground movement. FN data should be obtained for each pipeline assessed. clause 13. the pipeline depth of cover and the local installation of pipeline protection such as slabbing. 8 Factors affecting risk levels 8. either natural (e. Typical causes classified in databases include: a) b) c) d) e) external interference. The failure rates due to other damage mechanisms can be managed and controlled by competent pipeline operators through testing. design factor and material properties. mechanical failure. fatigue or operation outside design limits. as well as the location class. Mott Macdonald. either internal or external.PuBliSheD DocumenT PD 8010-3:2009 if the specified area of interest includes another pipeline. mining). including material or weld defects created when the pipe was manufactured or constructed. 2 Factors for reduction of the external interference failure frequency for use in site-specific risk assessments NOTE 1 An example of a site‑specific risk assessment is given in Annex C. Licensed Copy: x x.e. and justifications for any additional assumptions to be applied locally should be documented. the potential for stress corrosion cracking (Scc) or alternating current (Ac)/direct current (Dc) induced corrosion. the failure frequency in a class 2 area is four times that in a class 1 area. depth of cover. the design and installation should be assessed to ensure that additional loading is not imposed upon the pipeline. Procedural measures rely upon management systems and can be subject to change over time. Generic failure data might not be applicable to specific cases. Risk mitigation measures fall into two categories: physical and procedural. 10/06/2010 06:22. in some cases other causes might need to be considered in specific locations. The failure rates obtained from database records or predictive models should be justified for application to a site-specific case.1. information is given in Annex B. Where additional pipeline protection such as slabbing is to be taken into account. steel type and properties. i. in the case of depth of cover. The risk analysis requires the principal input data described in 5. site-specific depths should be taken into account. These should be installed prior to the completion and use of any new development within the pipeline consultation zone. pipe wall thickness. Mott Macdonald. 9. or predictive models validated using such data. Examples of typical benchmark solutions are given in Annex B. it is recommended that the damage incidence rate for location class 2 areas should be assumed to be higher than for class 1 areas. Data relating to class 1 and 2 incident rates for uK mAhPs is provided by uKoPA [9]. in determining the external interference failure frequency. such as the quality of girth welds. Typically.PD 8010-3:2009 PuBliSheD DocumenT subsidence at the specific location. including: • • • • • • pipeline diameter. The determination of failure rate data requires several parameters to be taken into account. 10]. Risk mitigation measures are identified and agreed as necessary by the statutory authority or relevant stakeholder. The primary residual risk for existing pipelines is that due to external interference. 8. (c) BSI The failure frequency associated with each damage mechanism should be determined using published operational data sources [8. the factor applied is approximately four times that for location class 1 areas. design factor. 20 • © BSI 2008 . Uncontrolled Copy. location class (1 or 2). and therefore might only be applicable for short-term risk control. Any site-specific variations should be assessed. Typical failure frequencies for uK mAhPs based on uKoPA data are given in Annex B. and that cathodic protection is maintained. not just the pipeline itself. Uncontrolled Copy. i/oe is the damage incidence rate. depth of cover. depth of cover. PD 8010-3:2009 Licensed Copy: x x. 10/06/2010 06:22. design factor. additional surveillance. Pipeline failure frequencies derived from published operational data sources are given in Annex B. given in Figure 10. © BSI 2008 • 21 . The pipeline failure frequency due to external interference is obtained as follows: F = (PoF × I) / oe where: F I oe is the pipeline failure frequency. Rwt – reduction factor for wall thickness. given in Table 2. Rdc – reduction factor for depth of cover. Rs – reduction factor for surveillance frequency. given in Figure 9 and Table 1. Rp – reduction factor for protection measures. given in Figure 11. or to obtain a failure frequency prediction for a given pipeline. Appropriate factors can be applied cumulatively to the base failure frequency for the particular pipe diameter as shown in Annex B. A number of factors which describe the specific effects of wall thickness. given in Figure 8 and Table 1. additional high visibility pipeline marker posts. These factors can be used to assess the effect of individual measures on a known or existing unadjusted pipeline failure frequency for a particular pipeline. the parameters listed above should be taken into account. slabbing. The influence of specific parameters on the predicted pipeline failure frequencies is given as reduction factors as follows: • • • • • Rdf – reduction factor for design factor. surveillance frequency and damage prevention measures (slabbing and marker tapes) are described in the present subclause.PuBliSheD DocumenT Physical measures include: • • • • • • wall thickness and design factor. When predicting site-specific pipeline failure frequencies for external interference. in kilometre years (km·y). and should document justification of any assumptions applied following assessment of these details. Mott Macdonald. and the operational exposure. NOTE 2 The number of external interference events causing damage . is the number of external interference events causing damage in a given pipeline population. is the operational exposure of the pipeline population. (c) BSI Procedural measures include: A site-specific risk assessment should take into account relevant details of the pipeline. relate to the population that the pipeline is part of. additional liaison visits. 4 0. 22] carried out using models which describe the failure of a pipeline due to gouge and dent-gouge damage [23. which are applied either to a predicted pipeline PoF or to a failure frequency predicted for a specific pipeline using a specific damage incidence rate.8 Design factor NOTE Figure 8 relates to a pipe wall thickness of 5 mm.72) 0. Mott Macdonald.PD 8010-3:2009 PuBliSheD DocumenT Figure 8 Reduction in external interference total failure frequency due to design factor 1. (c) BSI 0.3 0. 10/06/2010 06:22. 21. 22 • © BSI 2008 .97 (f -0. and can be used to assess the influence of design factor on failure frequencies due to external interference for pipelines with wall thickness equal to or greater than 5 mm. They may be applied separately to modify existing risk assessment results (i. The range of pipeline parameters over which the reduction factors are applicable is given in Table 1. and damage statistics for such damage derived from the uKoPA pipeline database [9].4 0.7 0. 25].2 0.6 0.0 0. Further details are given in Annex B.8 Reduction factor 0. These two reduction factors have been derived from the results of comprehensive parametric studies [20.2 = e 0. The reduction factors given in Figures 8 and 9 are based on a conservative interpretation of the parametric study results. Uncontrolled Copy.5 0. using both reduction factors in conjunction with the generic failure frequency curve in Annex B as an alternative to using more complex structural reliability based methods. or may be used more comprehensively to estimate the failure frequency in screening risk assessments. Figures 8 and 9 show simple reduction factors for design factor and wall thickness which can be used in estimating the failure frequency due to external interference.6 0.1 0.0 Licensed Copy: x x. The reduction factors take the form of a factor for the design factor and a factor for wall thickness.e. to modify existing risk assessment results taking into account local changes in wall thickness). 24. Rdf. This reduction factor has been derived from the results of published studies [26].6 e -0.2 0.8 Reduction factor 0. Table 1 Range of applicability of reduction factor for design factor.0 4 6 8 10 12 14 16 18 20 Wall thickness (mm) NOTE Figure 9 relates to design factors of 0.3 0. 0.39 (t-5) f = 0.3 and can be used to assess the influence of wall thickness on failure frequency due to external interference for pipelines with design factor less than or equal to these values.4). 10/06/2010 06:22.0 mm GX65 219.24 (t-5) f = 0. © BSI 2008 • 23 .PuBliSheD DocumenT PD 8010-3:2009 Figure 9 Reduction in external interference total failure frequency due to wall thickness 1. and reduction factor due to wall thickness.5 e -0.72 = e -0.4 mm H24 J (average) Figure 10 shows a simple reduction factor for depth of cover which can be used to assess the reduction in damage incidence rate in the estimation of the failure frequency due to external interference.0 Licensed Copy: x x.3. Uncontrolled Copy.72 H5. Rwt Parameter Design factor Wall thickness material grade Diameter charpy energy Range of applicability of Rdf and Rwt G0. (c) BSI 0.31 (t-5) f = 0. Mott Macdonald.1 mm to 914.72. use of this reduction factor places a requirement on the pipeline operator to carry out and document periodic checks to confirm that the depth of cover is being maintained (see 8.4 0.5 and 0. Mott Macdonald.6 Licensed Copy: x x.4 0.8 0.5 1.8 0.4 1. (c) BSI 1.2 Risk reduction factor 1. 10/06/2010 06:22. Figure 11 Indicative reduction in external interference total failure frequency due to surveillance frequency (dependent on frequency and duration of unauthorized excavations) 1.2 Reduction factor 1.5 2. 24 • © BSI 2008 .2 0 0 0.5 Depth of cover (m) Figure 11 shows a simple reduction factor for a surveillance interval which can be used to assess the reduction in damage incidence rate in the estimation of the failure frequency due to external interference.0 0.0 1.4 1.4 0. which can be used to assess the reduction in damage incidence rate in the estimation of the failure frequency due to external interference.0 3. These factors are based on expert studies [28].0 2.PD 8010-3:2009 PuBliSheD DocumenT Figure 10 Reduction in external interference total failure frequency due to depth of cover 1.6 0. Uncontrolled Copy.6 0.2 0 0 5 10 15 Surveillance interval (days) 20 25 30 Table 2 gives reduction factors that apply to pipeline protection measures.5 3.0 0. This reduction factor has been derived from the results of studies carried out by uKoPA relating infringement incidence data to damage incidence data [27]. © BSI 2008 • 25 . when used in conjunction with the base pipeline failure frequencies given in Annex B.). Rlv might only be applicable for short term/temporary developments only (e. and Rwt is derived for a constant design factor of 0. Rwt (reduction factor for wall thickness). the physical barrier mitigation measures should apply to the whole pipeline interaction length for every failure that has to be considered. determined using the recommended reduction factors given in this subclause for: • • Rdf (reduction factor for design factor).72. The reduction factors given in Figure 8 and Figure 9 affect the pipeline tolerance to defects and therefore the PoF. NOTE 2 In order to use the reduction factor. whereas the reduction factors given in Figure 10. I/OE. Rmp (reduction factor for additional high visibility marker posts). These reduction factors can be applied together within the limits of applicability given in Table 1.g. RiR. Mott Macdonald.1 [28]. b) the factor reduction on number of incidents (or incident rate). NOTE 4 With respect to control of risk to developments in the vicinity of pipelines. For site-specific risk assessments. RPoF. the main factors affecting failure frequency should be given careful consideration and the appropriate reduction factor applied as follows: a) probability of failure.05 PD 8010-3:2009 Licensed Copy: x x. Rp. determined using the recommended reduction factors given in this subclause for: • • Rdc (reduction factor for depth of cover). (c) BSI installation of concrete slab protection plus visible warning NOTE 1 Concrete slabbing with high visibility marker tapes has been shown to achieve significant risk reduction factors below 0. e. temporary construction sites etc. Rp [reduction factor for protection (slabbing and marking)]. for pipeline protection Measure installation of concrete slab protection Reduction factor Rp 0. Uncontrolled Copy.16 0. No recommendations are made here for values of Rlv and Rmp. NOTE 3 Rdf and Rwt have been derived from a parametric study in which Rdf is derived for a constant wall thickness of 5 mm.PuBliSheD DocumenT Table 2 Failure frequency reduction factors. 10/06/2010 06:22. using reduction factors assessed by the risk analyst for specific situations: • • • Rs (reduction factor for surveillance frequency). fairs. Factors for risk control measures along the pipeline route to reduce the number of incidents may be applied as follows for other mitigation measures. the application of Rs .g. Rlv (reduction factor for additional liaison visits). Assessment should be carried out for specific cases. Figure 11 and Table 2 affect the damage incident rate. festivals. 3 8. The installation of concrete slabbing over the pipeline can restrict access to the pipeline in the event of coating deterioration or corrosion damage.3. constructed in accordance with PD 8010-1:2004. A full survey of the actual depth of cover over the full interaction distance at the location under consideration should be carried out in order to record the depth of cover. 8.3. clause 9. and tested in accordance with PD 8010-1:2004. selection of the wall thickness to achieve an acceptable pipeline PoF.3 Laying slabbing over the pipeline installation of slabbing to provide impact protection to the pipeline should be carried out in accordance with PD 8010-1:2004. 10/06/2010 06:22. A justification of the permanence of the depth of cover should 26 • © BSI 2008 .3.2 to 8.PD 8010-3:2009 8. 8.4 Taking account of increased depth of cover increased depth of cover at the location under consideration may be taken into account where this exceeds the recommendations given in PD 8010-1:2004. Settlement at the tie-in points with the existing pipeline should be avoided. Uncontrolled Copy.g. selection of design factor and wall thickness based on AlARP calculations.3.2 Relaying the pipeline in increased wall thickness The pipeline should be designed in accordance with PD 8010-1:2004. Licensed Copy: x x. 6. and that the functionality and integrity of the cathodic protection system is confirmed before and after installation of the slabbing. clause 10. The rationale for the design of the new pipeline section should be specified and justified in relation to the need for risk reduction. 6.3.: • • • • design factor specified as 0.9. that the results of previous in-line inspection are assessed to determine whether there are any indications of corrosion in the length of pipeline to be slabbed that might need assessment and/or repair prior to slabbing.7 and in accordance with details specified in iGe/TD/1. it is therefore recommended that a coating survey is carried out prior to the installation of slabbing. clause 11. Particular care is required where the consolidation of the pipeline trench bed is disturbed allowing settlement.3 to reduce pipeline PoF at operating conditions. The structural loads imposed on the pipeline by the slabbing should be taken into account. e.8.5. (c) BSI 8. 6 and 8.3. Mott Macdonald. clauses 5.3.1 PuBliSheD DocumenT Implementation of risk mitigation measures General The implementation of risk mitigation measures should be carried out in accordance with PD 8010-1 and the recommendations given in 8. selection of wall thickness in relation to risks to new planned development. The function and integrity of pipeline corrosion protection across the new section and at the points of connection with the existing pipeline should be confirmed to be adequate and fit for purpose in accordance with PD 8010-1:2004. 3. providing further information on contacts and emergency telephone numbers. 13.3. Where route inspections are carried out at two-weekly intervals.3. the susceptibility to land sliding and the current and future land use.5 Installing additional pipeline markers PD 8010-1:2004. Such checks should be carried out at intervals not exceeding 4 years.3. high visibility pipeline markers. Mott Macdonald.9. Uncontrolled Copy. The depth of cover should be rechecked at specified locations during pipeline route inspections carried out in accordance with PD 8010-1:2004. 13.) 8. in addition. 13. The surveillance frequency may be increased using walking or vantage point surveys at specific locations as a risk mitigation measure. including the reason for the increased depth of cover.2 recommends that pipeline route inspections should be carried out. at all crossings and. the type of soil. can be installed as an additional risk mitigation measure.14 recommends that pipeline markers be installed at field boundaries. 10. increasing the surveillance frequency will increase the likelihood of detection of activities that could damage the pipeline.6 Increasing surveillance frequency PD 8010-1:2004.3.2 and E. where practicable. (See PD 8010-1:2004. Full details of any additional mitigation measures installed or implemented should be recorded in the pipeline records systems or included in the major accident prevention document (mAPD) for the pipeline. at changes in pipeline direction.PuBliSheD DocumenT PD 8010-3:2009 be prepared. (c) BSI 8. Licensed Copy: x x. 10/06/2010 06:22. © BSI 2008 • 27 .2 to detect factors that could affect the safety and operation of the pipeline. 1 The zone boundaries are determined by hSe using a process for calculating individual risk levels. which applies to significant development. A. or whether additional risk reduction measures (risk mitigation) can be applied at that location. local planning authorities in Great Britain are responsible for land use planning decisions under the Town and country Planning Act 1990 [30]. which is immediately adjacent to the pipeline. land use planning zones notified to local planning authorities by hSe are based on pipeline details provided in the operator’s pipeline notification. land use planning zones are used by hSe for mAhPs as defined by Regulation 18 and Schedule 2 of the Pipeline Safety Regulations 1996 [1]. to allow the planned development to proceed. Detailed guidance defining the hSe advice (“advise against” or “do not advise against”) for various types of development is contained in a comprehensive document available from the hSe website entitled Planning advice for developments near hazardous installations (PADHI+) [31]. and do not cover local variations. middle zone. within which the risk implications of proposed developments that significantly increase the population density have to be considered by the local authority. which applies to vulnerable or very large populations.PD 8010-3:2009 PuBliSheD DocumenT Annex A (informative) Licensed Copy: x x. outer zone. Where local pipeline details differ from the notified conditions. including high-pressure pipelines transporting defined hazardous substances. so that it can provide advice to the local planning authorities on the risks posed by major hazards to people in the surrounding area. and hSe is a statutory consultee with responsibility to provide advice with respect to public safety for any developments planned within or which straddle the consultation zone. middle and outer zone distances to local planning authorities.g. thicker walled pipe or slabbing3)] 3) The risk reduction factors given in 8. 28 • © BSI 2008 . and to pipelines that were notified under the notification of installations handling hazardous Substances Regulations 1982 [29] before the enactment of the Pipeline Safety Regulations 1996. (c) BSI Summary of HSE methodology for provision of advice on planning developments in the vicinity of major accident hazard pipelines in the UK Land use planning zones The health and Safety executive (hSe) sets land use planning zones for major hazard sites. Mott Macdonald. land use planning zones define three areas: • • • inner zone. The outer zone distance is also called the consultation zone. Risk reduction factors associated with slabbing are currently under review by hSe. Uncontrolled Copy. hSe then notifies the inner.2 are not currently used in the hSe methodology. based on information provided to hSe by the pipeline operator. including whether the pipeline has additional protection [e. 10/06/2010 06:22. A developer or local planning authority might wish to seek further information to see whether the risk at the specific development location is different from the generalized land use planning zone notified by hSe. it is recommended that the methodology be used for the prediction of site-specific risk levels for consideration in the reassessment of land use planning developments. © BSI 2008 • 29 . middle and outer. so that specific local conditions can be taken into account. where risk calculations show levels lower than (0. a detailed risk assessment is carried out by hSe to assess any change to zone boundaries. Mott Macdonald. The guidance in this part of PD 8010 is provided for use by pipeline operators. old people’s homes) is restricted to the outer zone (see also Clause 7). especially if it involves an increase in population within 1 mDoB. At the time when the pipeline operator becomes aware of the possibility of a development near a pipeline. (c) BSI NOTE 1 Because of the low levels of risk. NOTE 2 In the past.3 × 10−6) per year. NOTE 4 The location of very large sensitive developments (e. c) NOTE 3 In cases where the calculation of risks indicates risk levels are lower than (1 × 10−6) per year and therefore there is no middle zone. the inner and middle zones are made equal to the MDOB.3 × 10−6) per year of dangerous dose or worse to the average householder. or the pipeline mDoB. boundary between outer zone and no restrictions – the lesser of: 1) 2) an individual risk of (0. HSE has used a consequence‑based approach for calculating this distance. some MAHPs will not have an inner zone based on an individual risk level of (1 × 10−5) per year. there is a need to reassess the impact of site-specific details on the risk levels within the interaction zone using an established risk assessment methodology. This distance is calculated using the equation and substance factors given in PD 8010‑1:2004. an inner zone equivalent to the MDOB has been applied by HSE to MAHPs. Licensed Copy: x x. very large hospitals. Similarly. Uncontrolled Copy. However. before deciding whether to object to the proposed development. in these cases. b) boundary between middle zone and outer zone – an individual risk of (1 × 10−6) per year of dangerous dose or worse to the average householder. defining the levels of risk at each boundary as follows: a) boundary between inner and middle zone – based on the greater of: 1) 2) an individual risk of (1 × 10−5) per year of dangerous dose or worse to the average householder.3). inner. they need to assess the population increase against the original routing parameters. 10/06/2010 06:22. all three zones. it is based on the established best practice methodology for pipeline risk assessment. hSe has adopted a risk-based approach for calculating the distances to the zone boundaries from the pipeline. are made equal to the MDOB (PD 8010‑1:2004.5. notified outer zone distance. schools.g. The process is shown in Figure A. 5. developers and any person involved in the risk assessment of developments in the vicinity of existing mAhPs.5.3. local planning authorities. in some cases they might decide to initiate a full societal risk assessment to define acceptability or otherwise of the development against the FN risk curve presented in Figure 6.1. 5.PuBliSheD DocumenT PD 8010-3:2009 near the proposed development). the pipeline operator might need to carry out a societal risk assessment to allow comparison with the societal risk criteria in Figure 6.1 Planning application process and need for site-specific risk assessment Application for Planning Permission submitted to Local Planning Authority Licensed Copy: x x. the pipeline operator needs to consider the impact of increased population within the consultation zone and the effect on the original routing decisions made for the pipeline. 30 • © BSI 2008 . Uncontrolled Copy. the pipeline operator might consider objecting to the proposed development. the land use planning individual risk assessment and the pipeline operator’s societal risk assessment need to be carried out in parallel. especially if the development is within 1 MDOB. Mott Macdonald. 10/06/2010 06:22. so that a common understanding using the same data and risk assessment assumptions allows the effectiveness of the mitigation to be agreed.PD 8010-3:2009 PuBliSheD DocumenT Figure A. (c) BSI PADHI + assessment applied by Local Planning Authority No safety or risk issues for LPA to consider with this Planning Application Do not Advise Against NOTE 1 Planning decision result? Advise Against HSE Advise Against letter may prompt developer to request further information from the pipeline operator on the pipeline design in the vicinity of the development Pipeline design different from notified details Pipeline details as notified HSE reassess risks which may revise LUP zone distances Developer may request Pipeline Operator to consider further risk reduction / mitigation measures in vicinity of proposed development NOTE 2 HSE reassess risks which may change advice Risk reduction / mitigation measures proposed and evaluated Cost effective risk reduction may not be possible. If unfavourable results are obtained from the societal risk assessment. If significant population increase is likely to occur if the planning development goes ahead. Results of risk assessment can be given to LPA for consideration Do not Advise Against NOTE 1 Planning decision result? Advise Against Improvements agreed and implementation planned Do not Advise Against NOTE 1 Planning decision result? Advise Against NOTE 1 In all cases where the PADHI+ decision is “do not advise against”. NOTE 2 In cases where risk mitigation measures are being considered. © BSI 2008 • 31 .3 × 10−6) risk contours for ethylene.PuBliSheD DocumenT PD 8010-3:2009 mDoBs are given in PD 8010-1:2004.2 Distances to risk zones current hSe land use planning distances to (1 × 10−6) and (0.5. then HSE risk assessors might be willing to reconsider the case using the details relevant to the pipeline near the development. spiked crude and natural gas liquids (NGLs) Content of pipeline Distances to risk zones MAOP Diameter Wall thickness mm 7.56 9. Table A.52 X42 X52 X52 X65 X52 −6 MaterialA) Distance to (1 × 10−6) risk contour m 150 190 240 380 432 −6 Distance to (0. so that the effect can be quantified. spiked crude and natural gas liquids (nGls) are given in Table A. Licensed Copy: x x.1 as (1 × 10 ) and (0.3 × 10−6) risk contour m 200 230 320 435 485 bar ethylene ethylene ethylene Spiked crude nGl 95 95 99 64 69 mm 219 273 273 914 508 NOTE The land use planning zones defined in Table A. A) As specified in iSo 3183-2:1996. Zone distances based on these risk levels notified to the local planning authorities are as calculated by hSe. (c) BSI Dangerous dose is defined by hSe as a dose of thermal radiation that would cause: 1) 2) 3) 4) severe distress to almost everyone in the area. it might be appropriate to take into account proportions when calculating this distance.3. Normally.1 Typical (1 × 10−6) and (0. specific assumptions made by hSe are given in this document.09 5. 10/06/2010 06:22. a substantial fraction of the exposed population requiring medical attention. PADHI+ uses the three zones set by HSE that are based on the details given in the pipeline notification. any highly susceptible/sensitive people being killed. Uncontrolled Copy. In cases where local pipeline details differ from notified details. Where possible. NOTE 5 Due to the uncertainties associated with such predictions. requiring prolonged treatment. These criteria are based on the assumption that the exposed people are typical householders and indoors most of the time.3 × 10 ) risk distances were calculated by HSE using historical rupture frequency data. where the pipelines have sections with additional protection measures. A. some people being seriously injured. Mott Macdonald. including developments near pipelines. a dangerous dose for thermal radiation is defined as 1 050 tdu.03 7. in the case of mixtures.3 × 10−6) risk distances for ethylene. and therefore might differ from equivalent risk levels calculated using other methodologies. There are a number of aspects of the HSE land use planning and major hazards work that PADHI+ [31] does not deal with.1. the “dangerous dose” concept is used by HSE to define land use planning zones. 5.52 9. Uncontrolled Copy. For people inside buildings that are beyond the distance to piloted ignition. then the typical person is deemed to have received a dangerous dose. but are then assumed to try to escape from the building and to be subject to the thermal radiation effects from the crater fire. if the cumulative thermal dose exceeds 1 050 tdu.3 PuBliSheD DocumenT Specific HSE methods and assumptions NOTE Specific methods applied and assumptions made by HSE are given in this Annex so that the impact on calculated risk values can be considered. The methodology used by hSe calculates the distance to the spontaneous ignition of wood. and people inside buildings within this distance are assumed to become fatalities. A. People inside buildings outside the distance to the spontaneous ignition but within the distance to the piloted ignition of wood are assumed to survive the fireball. 32 • © BSI 2008 . when the two times are equal. Mott Macdonald. Licensed Copy: x x. The proportion of time the average householder spends indoors during the day is 90%. delayed ignition resulting in a flash fire followed by a jet fire: 0. other than natural gas.5. hSe calculates the reducing release rate with time and so obtains the cumulative amount released.PD 8010-3:2009 A. (c) BSI A. People inside buildings engulfed by pool fires or spray fires are assumed not to escape. delayed ignition resulting in a jet fire: 0.512.128.2 Probability of ignition Typical overall probabilities for flammable gases. 10/06/2010 06:22. NOTE Other probabilities are observed in historical data.16.2. 15. For further details of hSe’s consequence models. hSe assumes that the average householder is present 100% of the time. used by hSe are: • • • • immediate ignition resulting in a fireball followed by jet fire: 0. The time required to release the cumulative amount is then compared with the burn time of a fireball containing the cumulative amount released. the largest fireball is obtained. 33].3. 14.3. NOTE Uncertainties relating to the near field consequence analysis are accommodated through the application of an inner zone based on the MDOB.3 Thermal radiation and effects hSe assumes that the typical person will move away from the fire at a speed of 2. and the proportion at night is 99%. see [11. the building is assumed to provide full protection.3. which is calculated using the formula and substance factors given in PD 8010‑1:2004.3. 5. 32. provided that the thermal radiation dose they receive does not exceed 1 050 tdu. A.1 Prediction of consequences in predicting consequences. no ignition: 0.5 m/s and will find shelter at a distance of 75 m in a class 1 environment or at a distance of 50 m in a class 2 environment. material properties. The data given in Table B.003 0.013 0. © BSI 2008 • 33 .1 Failure frequencies for UK pipelines General in deriving the failure frequency for a specific pipeline. and is not intended to be applied to specific pipelines.2 — % hole 70.004 0.0 — % rupture 19. Mott Macdonald.5 76.046 0. it is presented to enable general comparison of the datasets only. Licensed Copy: x x.2 All damage mechanisms Pipeline failure frequencies for the population of uK major accident hazard pipelines derived from uK data collated since 1962 and published by uKoPA are given in Table B.003 0.1. diameter.04 0. (c) BSI B.011 0 0 0 0.8 for failure frequency for the different damage mechanisms apply to uK mAhPs. Further information is available in the uKoPA pipeline fault database report [9]. 10/06/2010 06:22. Uncontrolled Copy.006 0.057 0. all credible damage mechanisms and location specific factors that can influence the frequency of failure due to each individual mechanism need to be assessed.1 44. equivalent diameter greater than 6 mm but less than pipe diameter.009 0.002 0.052 — HoleB) 0.2 23.3 71. environment and pipeline operator management practices.7 — equivalent diameter up to 6 mm.3 to B.035 0.1 100.2 2.019 — Rupturec) 0. equivalent diameter equal to or greater than pipe diameter. Table B.9 0 17. pressure.063 0.076 0. NOTE Application of pipeline failure rates in a site‑specific risk assessment requires careful consideration of local details.4 26.9 33.011 0 0. location. account needs to be taken of pipeline-specific factors such as wall thickness. the data and examples given in B.PuBliSheD DocumenT PD 8010-3:2009 Annex B (informative) B.002 — Total 0.003 0.1 Failure rates for UK pipelines based on UKOPA data units in failures per 1 000 km·y Damage mechanism external interference external corrosion internal corrosion material and construction Ground movement other Total A) B) c) PinA) 0. Based on an analysis of the data given in Table B.1 represents the overall averaged set of failure frequencies applied to the whole pipeline population included in the database.0 82.3 0 0 0 22.264 % pin 10.1.073 0. in order to apply the above data in a pipeline risk assessment. 016 0 See Table B.03 0.149 0.004 0 Total 0. Licensed Copy: x x.049 0.022 0 0.031 0 Total 0.006 0. and as operational failure data is sparse. B. Table B.2 and B.03 0.01 0 0.028 0 0 RuptureA) 0. (c) BSI Table B. operational data relating to failure frequency due to external interference is presented in Tables B.3.4.116 0.3 Failure frequency due to external interference vs.4 Generic pipeline failure frequency curve for external interference General A generic pipeline failure frequency curve for external interference which can be used with the failure frequency reduction factors for design factor and wall thickness given in Figure 8 and Figure 9 respectively is derived by predicting the failure frequency for pipelines B.2 Failure frequency due to external interference vs. NOTE Failure frequency predictions based on assessment of current operational fault and failure data are published by UKOPA [9].01 0 0 0 HoleA) 0.079 0. Uncontrolled Copy. These models allow the prediction of failure frequencies taking into account pipeline diameter.162 0.072 0.079 0. recognized engineering practice requires that a predictive model is used to calculate failure frequencies for specific pipelines.061 0. wall thickness units in failure frequency per 1 000 km·y Wall thickness (mm) <5 5 to 10 >10 to 15 >15 A) PinA) 0 0.PD 8010-3:2009 B. Mott Macdonald.1 for definitions. wall thickness.119 0.3 PuBliSheD DocumenT Prediction of pipeline failure frequency due to external interference Pipeline damage due to external (third-party) interference is random in nature.031 0 See Table B.012 0 RuptureA) 0.1 34 • © BSI 2008 .022 0 0.067 0. material properties and pressure.01 0.223 0. diameter units in failure frequency per 1 000 km·y Diameter (mm) 100 250 400 560 700 860 1 200 A) PinA) 0 0.012 0 0 HoleA) 0. 10/06/2010 06:22.028 0.1 for definitions. 1 can be conservatively applied to pipelines with material grades of X65 and lower.72. a constant wall thickness of 5 mm and a material grade of X65.7.1). NOTE 2 The generic curve given in Figure B. i. a pipeline specific analysis needs to be carried out using a recognised failure frequency prediction tool. © BSI 2008 • 35 .21 0. (c) BSI Figure B.0 1 000. Failure frequencies for pipelines in S areas can be derived by multiplying the R area failure frequency by a factor of 4.2. 10/06/2010 06:22.1 Generic predicted pipeline failure frequencies for third-party interference 0.PuBliSheD DocumenT PD 8010-3:2009 of varying diameter with a constant design factor of 0.e.7 is conservative. the leak/rupture failure mode is dependent upon the critical length of an axial defect.0 400. The generic failure frequency curve has been generated using probabilities of failure produced using the original dent-gouge model [23. This curve is shown in Figure B.205 0.0 200. Mott Macdonald. NOTE 1 Predicted failure frequencies due to external or third‑party interference increase with material grade due to the consequent reduction in wall thickness. The failure frequency prediction tool recommended by uKoPA is FFReQ (see B. 25]. and the estimated values are compared with FFReQ predictions for the equivalent pipeline case.225 Total failure frequency per 1 000 km . for leaks and ruptures.2. Uncontrolled Copy.195 0.1 provides failure frequencies for pipelines in R areas.5 can be used to select a more representative value.5. which is dependent upon both the diameter and the wall thickness. The data presented in B. and predicts the total probability of through wall failure.0 800.y 0. A conservative assumption for the proportion of ruptures which can be applied to the generic failure frequency curve is 0. The failure model is two-dimensional. Licensed Copy: x x.22 0. example calculations of failure frequency using the generic failure frequency curve and the design factor and wall thickness failure frequency reduction factors are given in B.215 0. as recommended in 8.0 600. so the proportion of ruptures of 0. in cases where risk levels are critical.0 Diameter (mm) use of the generic failure frequency curve with a fixed proportion of ruptures of 0. so the generic curve given in Figure B. however.4.2 0.1. 24.7 needs to be treated as an upper bound. for a design factor of 0.5 The reduction factor.6 mm wall thickness × 0. so the rupture frequency is: 0.013 × 0. for a wall thickness of 7.076 Estimated rupture frequency 0.6 mm wall thickness pipeline operating at a design factor of 0.1.1. is assumed to be 0.208 × 0.67 × 0. is: Rdf = 0. estimated from the generic total failure frequency curve in Figure B.87 The total failure frequency (TFF) for a 219 mm diameter pipeline. Rdf.81 The reduction factor.72.9 mm wall thickness pipeline operating at a design factor of 0. Mott Macdonald.2 Example 2: Estimation of external interference failure frequency for 609 mm diameter.024 219 mm diameter × 5.130 per 1 000 km·y The proportion of ruptures.5 The total failure frequency (TFF) for a 609 mm diameter pipeline.2 PuBliSheD DocumenT Estimation of pipeline external interference failure frequency using the generic failure frequency curve Example 1: Estimation of external interference failure frequency for 219 mm diameter.72.4.1 Licensed Copy: x x.2.13 FFREQ prediction 0. 10/06/2010 06:22.084 per 1 000 km·y 36 • © BSI 2008 . taken from Figure 9.PD 8010-3:2009 B. taken from Figure 8.3 at wall thickness 5 mm. 7. so the failure frequency for this pipeline is: TFF = 0.091 per 1 000 km·y The above estimates are compared with FFReQ predictions (per 1 000 km·y) in Table B. estimated from the generic total failure frequency curve in Figure B. (c) BSI Table B.3 The reduction factor. 5.9 mm at a design factor of 0. taken from Figure 9. Uncontrolled Copy. is: Rwt = 0.7.87 = 0.2. is: Rwt = 0.6 mm at a design factor of 0.7 = 0.091 FFREQ prediction 0. Rwt.4. taken from Figure 8. is 0. Rwt. Rdf.5 at wall thickness 5 mm. for a design factor of 0.223 × 0. B. RF.208 per 1 000 km·y. is: Rdf = 0. for a wall thickness of 5. is 0.5 = 0.81 × 0.3 design factor B.4.4.67 The reduction factor.4 Comparison of external interference failure frequency estimates for example 1 with FFREQ predictions Pipe case Estimated total failure frequency 0. so the failure frequency for this pipeline is: TFF = 0.223 per 1 000 km·y. 34 The total failure frequency (TFF) for a 914 mm diameter pipeline. so the rupture frequency is: 0. for a design factor of 0.039 per 1 000 km·y The above estimates are compared with FFReQ predictions (per 1 000 km·y) in Table B.5 mm wall thickness pipeline operating at a design factor of 0.5. taken from Figure 9. is: Rdf = 0.043 Estimated rupture frequency 0.084 FFREQ prediction 0.3 Example 3: Estimation of external interference failure frequency for 914 mm diameter.5 Comparison of external interference failure frequency estimates for example 2 with FFREQ predictions Pipe case Estimated total failure frequency 0. so the rupture frequency is: 0. estimated from the generic total failure frequency curve in Figure B. Table B.199 × 0.2. Licensed Copy: x x.059 FFREQ prediction 0. 9.81 The reduction factor. 10/06/2010 06:22.5 at wall thickness 5 mm.7.061 Estimated rupture frequency 0.059 per 1 000 km·y The above estimates are compared with FFReQ predictions (per 1 000 km·y) in Table B. so the failure frequency for this pipeline is: TFF = 0. Uncontrolled Copy.5 The reduction factor. is assumed to be 0.055 FFREQ prediction 0.5 design factor © BSI 2008 • 37 .039 FFREQ prediction 0.9 mm wall thickness × 0. Mott Macdonald.4.7.020 609 mm diameter × 7. taken from Figure 8.72. for a wall thickness of 9.055 × 0.7 = 0. (c) BSI Table B.055 per 1 000 km·y The proportion of ruptures. Rdf.6 Comparison of external interference failure frequency estimates for example 3 with FFREQ predictions Pipe case Estimated total failure frequency 0.PuBliSheD DocumenT PD 8010-3:2009 The proportion of ruptures. Rwt.084 × 0. is: Rwt = 0.5 design factor B. RF.5 mm at a design factor of 0.6. RF1. is assumed to be 0.1.008 914 mm diameter × 9.34 = 0.199 per 1 000 km·y.5 mm wall thickness × 0.7 = 0.81 × 0. is 0. 5 PuBliSheD DocumenT Pipeline external interference failure frequency predictions for specific pipe cases FFREQ external interference failure frequency predictions for specific pipe cases The use of a generic failure frequency curve for external interference as described in B. Licensed Copy: x x.9 9. B.6 7.6 5.3 219. The FFReQ failure frequency predictions given in Tables B.9 7. and where possible. the approach is approximate. 38 • © BSI 2008 . and Figures B.4 allows conservative failure frequency estimates for specific pipeline cases to be readily estimated. 10/06/2010 06:22.1 Table B. predictions for the specific pipe case under consideration need to be carried out using a recognized failure frequency prediction model. Detailed predictions.2. Mott Macdonald.9 406.7 UKOPA pipe cases Outside diameter mm 168. The current tool for the prediction of pipeline failure frequency due to external interference recommended by uKoPA is FFReQ.8. B.5 X42 X46 X52 X52 X52 X52 X60 X60 X65 Material grade NOTE The wall thickness values in Table B.5.6 5. (c) BSI B.PD 8010-3:2009 B.10.7 represent a lower bound of pipeline wall thickness data in the UKOPA database. are published on the uKoPA website.4 508 609 762 914 Wall thickness mm 5.9 7. are for pipelines located in R areas. however.3 and B. Failure frequency predictions generated using FFReQ for pipe cases selected to represent the range of pipe parameters in the uKoPA database given in Table B.9 7.1 273 323. These values are generally below the minimum recommended wall thicknesses given in IGE/TD/1. Uncontrolled Copy.9 and B.7 are given in this subclause for reference and application.6 5.4. including results for pipelines located in S areas. 04 0.063 0. Uncontrolled Copy.082 0.042 0.020 Licensed Copy: x x.030 0.109 0.068 0.143 0.142 0.088 0.188 0.061 0.059 273A) 0.200 Total failure frequency per 1 000 km .067 406.80 © BSI 2008 • 39 .029 762A) 0.02 0.PuBliSheD DocumenT PD 8010-3:2009 Table B.7 (per 1 000 km·y) Design factor 0.185 0.097 0. in millimetres (mm).027 609A) 0.140 0.076 0.4 0.103 0.095 0.186 0.022 508A) 0.08 0.046 0.4A) 0.071 0.2 A) Total failure frequency 168.068 0.1A) 0.0 0.137 0.115 0.086 0.160 0.138 0.2 FFREQ predictions of total external interference failure frequency for UKOPA pipe cases 0.20 0.073 0. y 168 219 273 323 406 508 609 762 914 0.044 0.06 0.065 0.3 0.103 0.107 0.082 0.40 Design factor 0.100 0.189 0.056 0.3A) 0.040 0.9A) 0.6 0. (c) BSI Diameter.100 0.180 0.5 0.112 0. Figure B. 10/06/2010 06:22.031 914A) 0.72 0.037 0.8 FFREQ predictions for total external interference failure frequency for pipe cases defined in Table B.60 0.059 0. Mott Macdonald.090 0.051 0.054 0.0 0.039 0.056 219.120 0.044 0.050 0.061 0.064 323.026 0. 021 0. Uncontrolled Copy.024 0.1A) 0.013 219.9 FFREQ predictions for external interference rupture frequency for pipe cases defined in Table B.006 0.023 0.8 168 219 273 323 406 508 609 762 914 40 • © BSI 2008 .3A) 0.064 0.04 0.138 0.017 0.020 0.064 0.060 0.12 0. (c) BSI Diameter.139 0.001 762A) 0.PD 8010-3:2009 PuBliSheD DocumenT Table B.011 273A) 0.2 A) Rupture frequency 168.9A) 0.042 0.031 0.4 Design factor 0.005 0.135 0.08 0.022 0.065 0.049 0.001 609A) 0.089 0.06 0. in millimetres (mm).1 0.009 406.014 0.026 0.6 0.130 0.060 0.012 0.3 0.029 0.039 0.002 508A) 0.008 0.062 0.7 (per 1 000 km·y) Design factor 0.4A) 0.16 0.010 323.3 FFREQ predictions of external interference rupture frequency for UKOPA pipe cases Rupture failure frequency per 1 000 km . Mott Macdonald. 10/06/2010 06:22.093 0.004 0.028 0.004 0.011 0.14 0.047 0.72 0.030 0.022 0.5 0.001 0.011 0.091 0.043 0.4 0.2 0.027 0.y 0.004 0.041 0.010 0.001 914A) 0.000 Licensed Copy: x x.6 0.02 0 0 0. Figure B.087 0. 091 0.7 (per 1 000 km·y) Design factor 0.008 0.002 A) 219.019 0.5 wt leaks 219 dia x 5.024 0.8 406 dia x 7.046 0.6 0.035 0.6 wt ruptures 219 dia x 5.052 0.9 wt leaks 914 dia 9. in millimetres (mm).y 0.138 0.1 0.12 0.4A) 0.030 0.4 Design factor 0.021 914A) 0.9 wt ruptures 406 dia x 7.4 0.16 Failure frequency per 1 000 km . (c) BSI 406.7 0.1 0.028 0.014 0.4 0.06 0.72 0.043 0.02 0 0 0. Mott Macdonald.036 0.004 0. Uncontrolled Copy.030 0.022 0.14 0.041 0.064 0.024 0.031 0.064 0.037 0.048 0.047 0.6 0.5 0.042 0.2 0.PuBliSheD DocumenT Table B.001 0.006 0.1A) 0.3 0.5 0.039 0.025 0.000 Diameter.08 0.10 PD 8010-3:2009 FFREQ predictions for external interference rupture and leak frequencies for pipe cases defined in Table B. Figure B.04 0. 10/06/2010 06:22.1 0.4 FFREQ predictions for external interference rupture and leak frequencies for specific diameter and wall thickness cases (per 1 000 km·y) 0.2 A) Rupture frequency 219.012 0.011 A) Leak frequency 914 A) Licensed Copy: x x.027 0.3 0.5 wt ruptures 914 dia 9.6 wt leaks © BSI 2008 • 41 .048 406. 2.187 per 1 000 km·y. 10/06/2010 06:22.72.48. the wall thickness reduction factor for a 5. the design factor reduction factor for a design factor of 0. (c) BSI B.6 is 0.48 = 0.2 Example 4: Modification of an existing external interference failure frequency for a 219.2.2.5.4 is 0. Rdf.10 and Figure B.4 is 0.6.79/0. to that for a pipeline of wall thickness of 7.5.9 mm wall thickness is 0. The reduction factor. the proportion of ruptures for a 219.PD 8010-3:2009 B. Licensed Copy: x x.6 mm wall thickness.9 mm and design factor of 0. The revised rupture frequency is therefore: 0.3 Example 5: Modification of an existing external interference failure frequency for a 762 mm diameter pipeline of 5. 42 • © BSI 2008 .5.073 per 1 000 km·y From Table B.5. The reduction factor.918 × 0. operating at a design factor of 0.2 and B.1 mm diameter pipeline of 5. Rwt.6 mm wall thickness is 0.3.575 The revised total failure frequency (TFF) is therefore: TFF = 0. the existing failure frequency for a 219 mm diameter pipeline of 5.5/0.575 = 0.89 = 0. Uncontrolled Copy.89.1 provide more realistic failure frequency predictions than the conservative estimates given in B.79.5.2 PuBliSheD DocumenT Estimation of external interference failure frequencies using FFREQ predictions and reduction factors for design factor and wall thickness General The FFReQ predictions in B.8.2.4 for specific pipe cases. operating at a design factor of 0. to that for a pipeline of wall thickness 7.035 per 1 000 km·y B. for wall thickness to be applied in this case is therefore: Rwt = 0.918 From Figure 9.88.4 The existing failure frequency for a 762 mm diameter pipeline of 5.9 mm and design factor of 0.86 = 0. Mott Macdonald. From Figure 8.073 × 0. example calculations are given in B.1 mm diameter pipe operating at a design factor of 0.4 From Table B.5. for design factor to be applied in this case is therefore: Rdf = 0.138 per 1 000 km·y. The FFReQ failure frequencies can be modified to produce estimates for further pipe cases using the reduction factors for design factor and wall thickness given in Figures 8 and 9 respectively.4.2.5. the wall thickness reduction factor for a 7. the design factor reduction factor for a design factor of 0.72 is given as 0.5.138 × 0. From Figure 8.6 is 0. From Figure 9.6 mm wall thickness.1 B.6 mm wall thickness operating at a design factor of 0.6 mm wall thickness operating at a design factor of 0. 11 Comparison of external interference failure frequency estimates for example 5 with FFREQ predictions Pipe case Estimated total failure frequency 0. For high-pressure gas releases (in which the energy of the depressurizing gas does not decay immediately).6 mm is 0.5. Typical values of the equivalent hole diameter for critical defect lengths for pipelines operating at a design factor of 0.10 and Figure B.12. the proportion of ruptures for a 406 mm diameter pipe operating at a design factor of 0. for wall thickness to be applied in this case is therefore: Rwt = 0.9 mm wall thickness pipe.81 = 0.PuBliSheD DocumenT PD 8010-3:2009 From Figure 8. From Table B.9 mm is 0. the design factor reduction factor for a design factor of 0. Rwt. the critical size of a crack-like defect at which the failure mode changes from leak to rupture. The maximum area through which the high pressure gas escapes at the critical length is usually determined as an equivalent hole size in order to calculate the maximum leak release rate [34]. the wall thickness reduction factor for a wall thickness of 7. Uncontrolled Copy.e.01 762 mm diameter × 7. so it is conservative to assume that the proportion of ruptures for a 762 mm diameter × 7. The reduction factor.286 = 0.087 × 0.4 is 0.75 × 0. needs to be taken into account. (c) BSI From Figure 9.4 in Table B.81.286.9 mm wall thickness pipe is equivalent to that for a 406 mm diameter × 7. Licensed Copy: x x. Table B. 10/06/2010 06:22.72 are given in Table B.617 The revised total failure frequency (TFF) is therefore: TFF = 0.9 mm wall thickness × 0.5. From Figure 9.11.087 FFREQ prediction 0. © BSI 2008 • 43 . Mott Macdonald. The revised rupture frequency is therefore: 0.5/0.059 Estimated rupture frequency 0.025 per 1 000 km·y The above estimates are compared with FFReQ predictions for a 762 mm diameter × 7.617 = 0.4.087 per 1 000 km·y The proportion of ruptures reduces as the diameter and wall thickness increase. the wall thickness reduction factor for a wall thickness of 5. and are modelled as crack-like defects. when the critical length is exceeded.4 is 0.75.3 Critical defect size Damage caused by external interference typically includes gouges. i.4 design factor B.025 FFREQ prediction 0.187 × 0.9 mm wall thickness pipe operating at a design factor of 0. which are of a narrow slot shape. 10/06/2010 06:22. the corrosion failure frequency rate can be assumed to reduce by a factor of 10.04 0.302 0.015 0 0 RuptureA) 0 0 0 0 Total 0.6 5. it is expected that the corrosion rates in Table B.9 406. for pipelines of wall thickness up to 15 mm commissioned after 1980 and with corrosion control procedures applied. Mott Macdonald.92 53.9 9.1 273 323.9 7. The failure frequency due to external corrosion in the uK is dependent upon the year of construction and hence the age and applicable coating.3 219.05 5.99 64.09 36. For pipelines of any age with wall thicknesses 44 • © BSI 2008 .6 5.52 9.72 85.6 5.98 3.13.09 6.53 57.03 47.72 Dimensions in millimetres (mm) Diameter Wall thickness Material grade Critical defect length 28.41 2.1 Pipeline failure frequency due to corrosion External corrosion uKoPA data for external corrosion is given in Table B. Table B. (c) BSI 168. corrosion control procedures for external corrosion include: • • • monitored and controlled cP.72 33. regular in-line inspection. The data shows that to date there is no operational experience of rupture failure due to corrosion in the uK. For pipelines commissioned pre-1980.73 Licensed Copy: x x. Uncontrolled Copy.PD 8010-3:2009 PuBliSheD DocumenT Table B.031 0 0 HoleA) 0.13 Failure frequency due to external corrosion units in failure frequency per 1 000 km·y Wall thickness (mm) <5 5 to 10 >10 to 15 >15 A) PinA) 0. Based on analysis of uKoPA pipeline fault and failure data [35].9 7.12 Critical defect lengths and equivalent hole diameters for UKOPA pipeline cases operating at a design factor of 0.9 7.42 4.6.38 12.1 for definitions.262 0.91 Critical hole diameter limit rupture/leak 2. corrosion protection design standards and corrosion control procedures.5 X42 X46 X52 X52 X52 X52 X60 X60 X65 B.4 508 609 762 914 5.97 31.35 7. and defect assessment and remedial action.046 0 0 See Table B.6 7.13 will be applicable unless corrosion control procedures have been used.6 B. and that no ruptures have been recorded to date in the uK.7 Pipeline failure frequency due to material and construction defects uKoPA data for the failure frequency due to material and construction defects is given in Table B.004 Analysis of the uKoPA pipeline fault and failure data [35] shows that failure frequency due to material and construction defects in the uK is dependent upon the year of construction and hence the age.8 B. The failure frequency of a specific pipeline due to ground movement is dependent upon the susceptibility to natural landsliding along the route. (c) BSI B. B.064 0. The uKoPA data indicates that corrosion failures occur as leaks. B. and this needs to be assessed on a location specific basis.1 Pipeline failure frequency due to ground movement General There is insufficient historical data to establish a relationship between ground movement failure data and individual pipeline parameters. Mott Macdonald. design and construction standards. For pipelines commissioned after 1980. © BSI 2008 • 45 .031 0.6.14 Material and construction failure frequency vs. The uKoPA data indicates that material and construction failures occur as leaks. Table B. and the failure frequency needs to be assessed taking into account corrosion control procedures and use and frequency of in-line inspection. Uncontrolled Copy. in particular the material selection controls and welding inspection standards applied. the corrosion failure frequency can be assumed to be negligible.2 Internal corrosion Review of uKoPA data confirms that the incidence of internal corrosion in mAhPs in the uK to date is low.046 0. the material and construction failure frequency rate can be assumed to reduce by a factor of 5.PuBliSheD DocumenT PD 8010-3:2009 greater than 15 mm and with corrosion control procedures in place.8. The likelihood of occurrence of internal corrosion depends upon the fluid transported.007 0. and needs to be assessed on a pipeline specific basis.14. 10/06/2010 06:22. this shows that the failure frequency reduces as the wall thickness increases.505 0. wall thickness Wall thickness range mm <5 5 to 8 >8 to 10 >10 to 12 >12 to 15 >15 Wall thickness value assigned to range mm 5 8 10 12 15 17 Failure frequency per 1 000 km·y 0. and that no ruptures have been recorded to date. Licensed Copy: x x. constructed and operated in accordance with current pipeline standards. fatigue etc.8. Table B. where the local susceptibility to landsliding and the associated likelihood of slope instability has been assessed. uKoPA has concluded that the predicted background rupture failure rate of (2. the likelihood of failure of the pipeline needs to be assessed on a case-specific basis. Such activities are location-specific and time-limited.8.2 PuBliSheD DocumenT Natural landsliding Based on a detailed assessment of pipeline failure frequency due to natural landsliding in the uK. Where and when activities that might result in artificial ground movement occur in the vicinity of a pipeline.1 to B.3 Artificial ground movement Artificial ground movement can be induced through activities such as mining. however.9 Pipeline failure frequency due to other causes Pipeline failure rates due to causes other than those outlined in B..5% of the incidents recorded in this category relate to pre‑1970 pipelines.0 × 10−4) B. Mott Macdonald. The UKOPA pipeline fault data report [9] confirms that 62. 46 • © BSI 2008 . B. or is present and might occur in future Slope instability is likely and site specific assessment is required Pipeline rupture rate per 1 000 km·y 0 to (9 × 10−5) Licensed Copy: x x. and the associated risks need to be assessed and managed by the pipeline operator through notification and surveillance activities. the rupture rate due to ground movement caused by natural landsliding can be obtained from Table B. adjacent construction work etc.8 need to be assessed on a pipeline-specific basis. (c) BSI (1 × 10−4) to (2. but might be affected by slope movement on adjacent areas Slope instability might have occurred in the past or might occur in future. Derivation of a failure rate based on this data is therefore not recommended.14 × 10−4) >(3. Relevant causes can include overpressure. and are not relevant to pipelines designed. Uncontrolled Copy. 10/06/2010 06:22. and will vary according to the operating regime and/or location of the pipeline or pipeline section.15.PD 8010-3:2009 B.1 × 10−4) per 1 000 km·y due to natural landsliding is applicable to all uK mAhPs. NOTE The UKOPA product loss data in Table B. quarrying.15 Pipeline rupture failure frequency due to due to ground movement caused by natural landsliding Description Slope instability is negligible or unlikely to occur. and procedures for safe working in the vicinity of pipelines.1 indicates that other causes account for approximately 28% of the total failure rate. Licensed Copy: x x. and discovers that for a larger development of more than 30 dwelling units.2 Risk assessment The developer commissions a risk assessor to review the land use planning zones and possible mitigation that could be applied. The developer then contacts the pipeline operator to see whether there are any special conditions associated with the pipeline that could affect the planning application. Details are shown in Figure c. on checking their records. wall thickness: 7. pipeline diameter: 219 mm.1 Example of a site-specific risk assessment Scenario A planning application for a housing estate consisting of 38 houses in a green field rural area near a village has been lodged with the local planning authority.03 mm. the planning authority finds that there is an ethylene pipeline located near the proposed site which has land use planning zones.1 Proposed development Proposed housing development Outer zone 200 m Middle zone 150 m Inner zone 70 m Pipeline The planning authority checks pipeline risk zones against advice from hSe. 10/06/2010 06:22. © BSI 2008 • 47 . Mott Macdonald.1. the developer is able to confirm that the pipeline design conditions are as notified to hSe and therefore the only possibility would be to apply mitigating factors to reduce the risk zones. Uncontrolled Copy.PuBliSheD DocumenT PD 8010-3:2009 Annex C (informative) C. The closest house is 75 m from the pipeline. C. hSe advises against allowing this development to proceed. The following details are confirmed: • • • product: ethylene (dense phase). After discussion with the operator. The planning authority therefore informs the developer that they will refuse planning permission on safety grounds. if more than 10% of the development is in the middle zone. (c) BSI Figure c. the maximum leak hole size (see Table B.156 2 per 1 000 km·y. Uncontrolled Copy. Applying reduction factors given in Figures 8 and 9: • • • • • b) reduction factor for design factor of 0. The total failure rate due to third-party interference is therefore: The rupture failure rate due to third-party interference is: The critical hole diameter for this pipeline to be used to determine the release rate for leaks [i. fireball duration: 7. the total failure rate for a 219 mm diameter pipeline with 5 mm wall thickness at a design factor of 0. For this pipeline.03 mm = 0.5.72 is 0. the above assessment indicates that third-party interference accounts for 45% of failures. (c) BSI From this the design factor is calculated as 0. Ground movement: failure frequency due to ruptures = 2. PuBliSheD DocumenT maximum allowable operating pressure: 95 bar.046 per 1 000 km·y.PD 8010-3:2009 • • • • steel: X42.223 1 per 1 000 km·y. fireball radius: 50 m.201 per 1 000 km·y. area classification: class 1 (rural).51 = 0.137 2 per 1 000 km·y. external corrosion: failure frequency due to leaks (Table B.5 s.1 × 10−4 per 1 000 km·y.32 mm. therefore. total failure frequency rate = 0. The rupture rate assuming 70% ruptures is 0.063 6 per 1 000 km·y. rupture failure rate = 0.e. 10/06/2010 06:22. reduction factor for wall thickness 7. the leak rate is 0.7 × total failure rate = 0. material and construction: failure frequency due to leaks (Table B. total failure rate = 0.223 × 0.14) = 0. Mott Macdonald. the total failure frequency rate for this pipeline is therefore determined as follows: • • • failure frequency due to leaks = 0.13) = 0.027 per 1 000 km·y. 48 • © BSI 2008 . The risk assessor is therefore able to simulate risks from the following main calculation steps: • • • • minimum distance to occupied buildings (mDoB): 45 m.12)] is calculated as 6. obtaining failure rates from Annex B: a) Failure rate due to third-party interference: From Figure B.1. c) d) e) From a) to d) above. depth of cover: 1 100 mm.81 × 0.064 per 1 000 km·y.090 8. failure frequency due to ruptures = 0.5 = 0.063 8 per 1 000 km·y. Licensed Copy: x x. fireball spontaneous ignition distance: 67 m.51.81. 3 C. The re-calculated risk distances are: • • This can reduce the middle zone so that most of the new development is outside the middle zone. rupture 30 s jet flame escape distance: 86 m.006 6 per 1 000 km·y. Uncontrolled Copy. the concrete slabbing would be defined by the effect on the planning decision and an AlARP assessment. re-lay pipeline in heavy-wall pipe.3. 10/06/2010 06:22. The new failure rates are therefore: • • rupture failure rate: (0. subject to formal acceptance that concrete slabbing reduces the risk. © BSI 2008 • 49 .3.2.2 and C.119 per 1 000 km·y.3 respectively. (3 × 10−7) per year individual risk: 275 m.1 + 0.2 Installing concrete slabbing and marker tape over the pipeline This is conservatively assumed to reduce the third-party failure frequency by a factor of 0. which are: • • • inner zone: 70 m (as originally notified by hSe). however. 10−6 per year individual risk: 125 m. (c) BSI These risk levels correspond well to hSe land use planning zones. outer zone: 200 m (as originally notified by hSe).064 × 0. C.090 8 × 0. Mott Macdonald.3. These measures are discussed in C. total failure rate: (0. PD 8010-3:2009 From this.064 + 2.1 × 10−4) = 0.1 in this case. The distance adjacent to the proposed housing over which slabbing and marker tape is required is the interaction distance as shown in Figure c. middle zone: 150 m.1 Mitigation measures Possible measures The following possible mitigation measures are proposed for risk reduction: a) b) install concrete slabbing and marker tape over the pipeline. (3 × 10−7) per year individual risk: 120 m.PuBliSheD DocumenT • • • • fireball 1 000 tdu in open air distance: 95 m. if this was accepted.1 × 10−4) = 0. 10−6 per year individual risk: 80 m. C.1 + 2.3. the distance to risk levels are calculated as follows: Licensed Copy: x x.046 + 0. 3.3 Societal risk FN curves and PD 8010-3 FN criterion line – proposed development before and after slabbing 1. 10/06/2010 06:22. The resulting graph is shown in Figure c.05 D C 1. Mott Macdonald.2 Risk for outside exposure PuBliSheD DocumenT Licensed Copy: x x.06 1.00E .00E .07 1 10 100 1 000 A Key A B c D number of casualties Frequency (per year) of N or more casualties Broadly acceptable Tolerable if AlARP PD 8010-3 risk criterion line Proposed development before slabbing Proposed development after slabbing 50 • © BSI 2008 .04 B 1.00E .PD 8010-3:2009 Figure c.00E . Uncontrolled Copy. Figure c.00E . (c) BSI Fireball outdoor hazard distance 95 m Fireball outdoor hazard distance 95 m Closest house 75 m Pipeline Interaction distance 117 m The operator also requests a societal risk assessment for the situation before slabbing and after slabbing to be able to assess the risk reduction achieved.03 1. 034 0 per 1 000 km·y. reduction factor for wall thickness 11. 10/06/2010 06:22. whereas after slabbing the risk has reduced so that all risks are within the “broadly acceptable” region. For this pipeline. © BSI 2008 • 51 . total failure frequency rate = 0.007 2 per 1 000 km·y.64 × 0.067 = 0. Mott Macdonald. and are therefore considered to be AlARP. The rupture rate assuming 70% ruptures is 0.007 per 1 000 km·y. the total failure frequency rate for this pipeline is therefore determined as follows: • • • failure frequency due to leaks = 0. Uncontrolled Copy.3. therefore. material and construction: failure frequency due to leaks (Table B. which in this case is equal to the length of the proposed development plus twice the maximum hazard range). the leak rate is 0.0 per 1 000 km·y. total failure rate = 0. the total failure rate for a 219 mm diameter pipeline with 5 mm wall thickness at a design factor of 0. rupture failure rate = 0.14) = 0.3 Re-laying the pipeline section in thick-wall pipe The effect on risk of re-laying the pipeline adjacent to the proposed new development in 11.PuBliSheD DocumenT PD 8010-3:2009 measured against the 1 km societal risk criterion for an interaction distance of 450 m (the site interaction length. the above assessment indicates that third-party interference accounts for 24% of failures.068.1 × 10−4) per 1 000 km·y. and applying the thermal radiation level of 1 800 tdu for comparison with this criterion.031 per 1 000 km·y. a) Failure rate due to third-party interference: From Figure B. thick wall pipe will have a lower proportion of ruptures.72 is 0. this indicates that the proposed development was above the “negligible/tolerable” risk criterion line. failure frequency due to ruptures = 0. Licensed Copy: x x.3: • • • reduction factor for design factor of 0.91 mm and design factor 0. Applying reduction factors given in Figures 8 and 9 for a wall thickness of 11.67.1.91 mm thick pipe is assessed.223 × 0.7 × total failure rate = 0.003 per 1 000 km·y. Ground movement: failure frequency due to ruptures = (2.156 per 1 000 km·y. however. more detailed assessment methods need to be applied to obtain the proportion of ruptures.13) = 0.91 mm = 0. From a) to d) above.041 per 1 000 km·y. The total failure rate due to third-party interference is therefore: The rupture failure rate due to third-party interference is: • • b) c) d) external corrosion: failure frequency due to leaks (Table B.223 per 1 000 km·y.3 = 0. (c) BSI C.001 0 per 1 000 km·y. and would again need to be justified by AlARP considerations. Mott Macdonald. (c) BSI This can reduce the middle zone so that all the new development is outside the middle zone.PD 8010-3:2009 The re-calculated risk distances are: • • 10−6 per year individual risk: 55 m. Licensed Copy: x x. 10/06/2010 06:22. Uncontrolled Copy. or expectation value achieved by the mitigation measures [18]. The judgement based on the results needs to take account of: • • • the uncertainty in the data and models used in the assessment. societal concerns including aversion. 52 • © BSI 2008 . PuBliSheD DocumenT (3 × 10−7) per year individual risk: 100 m. AlARP considerations would include cost benefit considerations based on the reduction in total loss. criteria specific to the individual pipeline operating company. D. uK. Western European cross country oil pipelines 30 year performance statistics.. london: hmSo. hASWell. Brussels: concAWe. © BSI 2008 • 53 . lYonS. canada. A methodology for the prediction of pipeline failure frequency due to external interference.co. elliS. The application of risk techniques to the design and operation of pipelines. T. 30 September – 3 october 2008. D.. eastbourne.uk/publications. amended 1999. 113-125. institute of Gas engineers 129th Annual General meeting and Spring conference. Proceedings of international conference on Pressure Systems: operation and Risk management. Pipeline design using risk based criteria. 29 September – 3 october 2002. FeARnehouGh. c. G. R. Recent developments in the design and application of the PIPESAFE risk assessment package for gas transmission pipelines. and JAGeR. e.6) [5] [6] [7] [8] [9] 4) 5) 6) Available from uKoPA. uKoPA PiPeline FAulT DATABASe... R. (c) BSI For dated references. i. August 2007. london: hmSo.org. Available for downloading at http://www. GReAT BRiTAin. PP.V. GReAT BRiTAin.PuBliSheD DocumenT PD 8010-3:2009 Bibliography Licensed Copy: x x. and KnoTT. and JAcKSon. BAlDWin.. health and Safety at Work etc. london: institution of mechanical engineers. loughborough: Advantica. Standards publications PD 8010-2. Petroleum and natural gas industries – Steel pipe for pipelines – Technical delivery conditions – Part 2: Pipes of requirements class B Other publications [1] [2] [3] [4] GReAT BRiTAin. may 1992. london: hmSo. the latest edition of the referenced document (including any amendments) applies. Act 1974.5) ARunAKumAR. 10/06/2010 06:22. international Pipeline conference.concawe.n. communication 1492. Code of practice for pipelines – Part 2: Subsea pipelines iSo 3183-2:1996. october 1995. J. Uncontrolled Copy. hoPKinS. c502/016/95. Report 1/02. Available for downloading at http://www. calgary. Paper no. February 2002. lYonS. calgary. For undated references. only the edition cited applies. coRDeR. management of health & Safety at Work Regulations 1992. Pipelines Safety Regulations 1996. Mott Macdonald. canada.R.. i. m. n.4) AcTon. G. coRDeR.ukopa. P. Pipeline product loss incidents 1962‑2006 – 5th report of the UKOPA Fault Data Management Group. international Pipeline conference. Advantica Report 6957. Mott Macdonald. 1997.uk/~ucecm01/pipe-tech. Second edition. (c) BSI [11] SPenceR. P. miShAP – hSe’s pipeline risk assessment methodology. c. mAReWSKi. canada. london: W. Volume ii. eGiG 05 R.10) [22] coShAm.10) [23] RooVeRS. london: W. F. hAZARDouS inSTAllATionS DiRecToRATe. ePRG methods for assessing the tolerance and resistance of pipelines to external damage. u. BooD. protecting people – HSE’s decision‑making process. Pipeline technology. Atkins for the hSe. issue 1.. HID’s approach to ‘As Low As Reasonably Practicable’ (ALARP) decisions. J. Belgium. GAlli. n. 10/06/2010 06:22. london: Butterworths-heinemann.ac. Failure frequency reduction factors for design factor and wall thickness. Reducing risks. P.uk/comah/circular/perm09.S.J. and ReW. 1996. R. Details at http://www. Available from uKoPA. July-August 1997. international Pipeline conference. PipeTech – Pipeline rupture computational fluid dynamics simulator. 54 • © BSI 2008 . [15] Bilo. european member States: eGiG. Pie/2005/R104. 14 September 2007. london: hSe Books. h. PP. Atkins for the hSe. control of major Accident hazards Regulations 1999. J. Uncontrolled Copy.0002. Pie/07/Tn051 V0. 2001.gov. Gas pipeline incidents – 6th report of the European Gas Pipeline Incident Data Group 1970‑2004. [18] heAlTh AnD SAFeTY eXecuTiVe.uk/research/rrhtm/. Proceedings of the Third international Pipeline Technology conference (ed. 30 September – 3 october 2008. m.V.P. A model for ignition probability of flammable gases. Pipes and Pipelines International.0. h. and JAcKSon. 7) 8) 9) 10) Available for downloading at http://www..V.ucl. iSBn 0 7506 1547 8. 2007. P. contract Research Report cRR203/1997.gov. [16] mAhGeReFTeh.. m. R.. Loss prevention in the process industries.. h. Brugge. hASWell. 1997. 405-425.htm.PD 8010-3:2009 PuBliSheD DocumenT [10] euRoPeAn GAS PiPeline inciDenT DATA GRouP. m. P.10) [21] hASWell. and KinSmAn. DAYcocK. [13] leeS. December 2005. and KinSmAn. Risk calculation for pipelines applied within the miShAP hSe computer program.7) Licensed Copy: x x. and hASWell. J. 2000. calgary. [20] lYonS. P.hse. london: university college. contract Research Report cRR146/1997. october 2005.8) [17] heAlTh AnD SAFeTY eXecuTiVe. and ZARÉA. london: health and Safety executive. A.hse. Denys).html. and ReW. J. Ignition probability of flammable gases.homepages. march-April 1998.S.9) [19] GReAT BRiTAin. iSBn 0 7176 2151 0. Available for downloading at http://www. [14] Bilo. Reduction factors for estimating the probability of failure of mechanical damage due to external interference. Pipes and Pipelines International. m. m.7) [12] SPenceR.. STeineR. london: The Stationery office.J. The influence of pipe design factor and geometry on the failure of pipelines subject to 3rd party damage. February 2007. no. R. [27] mcconnell. and chATAin. 1979.12) [32] Bilo. 2001.m. Planning advice for developments near hazardous installations (PADHI+). This document does not carry a publication date.gov. Aspects of risk assessment for hazardous pipelines containing flammable substances. Effect of surveillance frequency on 3rd party excavation rate. Journal of Loss Prevention in the Process Industries. Uncontrolled Copy. The effectiveness of slabbing in preventing pipeline damage due to third party interference. G. october 2005. P. and KinSmAn. m. Licensed Copy: x x.11) [28] ToeS. Proceeding of the ePRG/PRc 10th Biennial Joint Technical meeting on line Pipe Research.htm. london: hmSo.hse. march 2006. issue 1. london: W.uk/landuseplanning/index. m.. UK pipeline failure frequencies. 4. Volume 4. [33] cARTeR. and hASWell. Journal of Mechanical Engineering Science. Pie/06/R0131. and TReVeS. [30] GReAT BRiTAin. EPRG recommendations for the assessment of the resistance of pipelines to external damage. c. The application of fitness for purpose methods to defects detected in offshore transmission pipelines. BlAcKmoRe. J.11) [29] GReAT BRiTAin.11) 11) 12) Available from uKoPA. c. 10/06/2010 06:22.A. P. Atkins for the hSe. london. [34] BAum. london: health and Safety executive. (c) BSI [25] coRDeR. [26] mATheR.S.V. Thermal radiation criteria used in pipeline risk assessment. Volume 21. © BSI 2008 • 55 . cambridge. uK. April 1995. J. J. [31] heAlTh AnD SAFeTY eXecuTiVe. Briefing paper to uKoPA RAWG. D. london: hmSo.PuBliSheD DocumenT PD 8010-3:2009 [24] hoPKinS. An assessment of measures in use for gas pipelines to mitigate against damage caused by third party activity. Pipes and Pipelines International. January 1991. i..0. contract Research Report 372/2001. notification of installations handling hazardous Substances Regulations 1982 and subsequent amendments.. it is available for downloading at http://www. Mott Macdonald. Town and country Planning Act 1990. 1992. Advantica Report 8904. PeTRie. [35] lYonS. Studies of the depressurisation of gas pressurised pipes during rupture. A. november-December 1997. conference on Welding and Weld Performance in the Process industry. and BuTTeRFielD. P. c. london: institution of mechanical engineers. Uncontrolled Copy. (c) BSI PD 8010-3:2009 This page deliberately left blank PuBliSheD DocumenT . 10/06/2010 06:22.Licensed Copy: x x. Mott Macdonald. Uncontrolled Copy. (c) BSI This page deliberately left blank .Licensed Copy: x x. 10/06/2010 06:22. Mott Macdonald. com Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards. 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