The United Kingdom Onshore Pipeline Operators Association (UKOPA) was formed by UK pipeline operators to provide a common forum for representing operators interests in the safe management of pipelines. This includes providing historical failure statistics for use in pipeline quantitative risk assessment and UKOPA maintain a database to record this data. The UKOPA database holds data on product loss failures of UK major accident hazard pipelines from 1962 onwards and currently has a total length of 22,370 km of pipelines reporting. Overall exposure from 1952 to 2010 is of over 785,000 km years of operating experience with a total of 184 product loss incidents during this period. The low number of failures means that the historical failure rate for pipelines of some specific diameters, wall thicknesses and material grades is zero or statistically insignificant. It is unreasonable to assume that the failure rate for these pipelines is actually zero. However, unlike the European Gas Incident data Group (EGIG) database, which also includes the UK gas transmission pipeline data, the UKOPA database contains extensive data on measured part wall damage that did not cause product loss. The data on damage to pipelines caused by external interference can be assessed to derive statistical distribution parameters describing the expected gouge length, gouge depth and dent depth resulting from an incident. Overall 3rd party interference incident rates for different class locations can also be determined. These distributions and incident rates can be used in structural reliability based techniques to predict the failure frequency due to 3rd party damage for a given set of pipeline parameters. The UKOPA recommended methodology for the assessment of pipeline failure frequency due to 3rd party damage is implemented in the FFREQ software. The distributions of 3rd party damage currently used in FFREQ date from the mid-1990s. This paper describes the work involved in updating the analysis of the damage database and presents the updated distribution parameters. A comparison of predictions using the old and new distributions is also presented.

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There are a number of methods that are commonly used for the assessment of a girth weld containing a ‘fabrication’ defect. These range from the more generic workmanship limits through to more complex pipeline specific Engineering Critical Assessment (ECA) methodologies. The workmanship limits stipulated in pipeline design codes can be very conservative, resulting in un-necessary and costly repairs. The ECA approach is being increasingly used to derive girth weld defect acceptance limits specific to a pipeline. These limits have been derived using either semi-analytical methods or from the results of large-scale tests conducted on pipeline girth welds. However, at present there is no one standardized method. The guidance produced by the European Pipeline Research Group (EPRG) is an example of an established methodology based on the results of large-scale tests, while commonly used pipeline specific semi-analytical assessment methods include API 1104 and CSA Z662. Other commonly used analytical methods, which are more generic in application, include BS 7910 and API 579-1/ASME FFS-1. Application of these methods to girth welds in grade X100 pipelines has not yet been validated. The US Department of Transportation, Pipeline and Hazardous Materials Safety Administration (PHMSA) commissioned Electricore, Inc and GL Noble Denton to investigate the applicability of these ‘commonly used’ girth weld assessment procedures to grade X100 pipelines. To facilitate this project, BP provided 10 girth welds from a full-scale operational trial of two grade X100 48in diameter pipeline test sections, following completion of the trial at GL Noble Denton’s Spadeadam test facility, Cumbria, UK. The girth welds were selected to enable the effects of material variability between abutting pipes, different heats and different manufacturers (pipe was sourced from two world class pipe mills, with the plate supply for one mill coming from two sources) to be investigated. A substantial test program has been undertaken to fully characterize the mechanical properties of each girth weld, comprising curved wide plate (CWP), tensile, Charpy impact and fracture mechanics tests. The results from the CWP tests have been analyzed using the procedures given in API 1104 (Option 2), EPRG, CSA Z662, BS 7910 and API 579-1/ASME FFS-1. This paper presents an overview of the tests undertaken and a comparison of the actual test results with the predictions from the assessment methods.

Early consideration of geotechnical conditions in coating selection and backfill design could prove technically, economically and environmentally beneficial. In addition, bedding, padding and backfilling requirements are not specified on a project specific basis and the current methodology for design, engineering and construction does not allow optimisation of the coating and backfill system. This paper is intended to review the financial and technical issues that need to be considered when selecting external coating systems for the corrosion protection of high-pressure transmission pipelines.

The Central Area Transmission System (CATS) in the UK sector of t he North Sea del ivers natural gas t hrough a 404 km pipeline from the CATS riser plat form to the North East coast of England. During the summer of 2007 this 36 inch diameter natural gas pi peline was dam aged by a vessel anchor. The anchor lifted the pi peline from under t he seabed, dragged i t across t he seabed, bendi ng t he pi pe and locally deforming it. This event resulted in a sig nificant in spection, assessment an d repair program me before t he pi peline co uld safely retu rn to operation. This paper descri bes t he det ailed st ructural assessm ent of the damaged pipeline and the inspection and repair operations. Following inspection of the pipeline by divers, the damage was assessed using the "Pipeline Defect Assessment Manual" (PDAM). The m anual was prepar ed from research prim arily for onshore pi pelines: t his paper di scusses t he strengths and weaknesses of PDAM and key differences in defect assessment for onshore and offshore pipelines. The paper highlights several very important lessons learnt from this incident, including: • the com plex st resses devel oped i n a pipeline that is pulled and moved by an anchor; • the need for dam age assessm ent m ethods for pi pe containing hi gh com pressive st resses and ' locked-in' stresses; • the safety aspects and com plexity of inspecting a pressurised and damaged subsea pipeline. These lessons learnt ar e then translated into recommendations for t he i ndustry, and advi ce t o ot her subsea pipeline operators.