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Use of Pipeline Operational Data

The operational data collected by UKOPA allows:

1. Quantification of various mitigating effects

Particular examples are the effect of wall thickness, steel type, operating pressure, depth of cover, physical protection such as concrete slabbing, frequency of surveillance to prevent 3rd party damage. Extensive data collected for over 40 years for leak and damage events which have occurred on UK pipelines allows the effects to be assessed, and the relative risk reduction measures to be derived.

2. Predictive models for 3rd party failure rate to be developed

One major advantage of the damage data collected by UKOPA members is that the effect of 3rd party damage can be estimated for any combination of pipeline design factors. Analysis of this data and the effects the damage has had on the pipelines involved (depth of dents and gouges resulting from the damage) allows damage curves to be produced showing the limiting case for assessing pipeline failure. Combined with the frequency at which the damage has occurred (the hit rate), it is possible to apply fracture mechanics theory in such a way that the failure frequency can be predicted for all combinations of design parameters, even for cases where no failures have yet occurred.

3. Extensive analysis of leak and damage data to demonstrate the reducing failure rate trends, and identification of the reasons

The RAWG has sponsored extensive studies on the various failure mechanisms affecting cross-country pipelines. These demonstrate the reducing failure rate trends, particularly for mechanical defects and corrosion failure mechanisms.

In addition, and using the work carried out by the RAWG and FDMG, UKOPA has:

4. Sponsored derivation of Risk Reduction Factors for mitigation measures

Sometimes risk reduction measures are required when population encroachment has occurred during the lifetime of a pipeline. The original routing of the pipeline may have been well away from populated areas, but as time goes by, housing and other developments are sometimes constructed closer that the original design codes would have permitted. In such cases, risk reduction (mitigation) measures may be required. Quantification of the risk reduction effect of such measures is important to assess whether acceptable levels of safety can be achieved, even with these higher population levels.

The RAWG has sponsored studies to examine risk reduction measures such as concrete slabbing, thicker wall pipe, increased surveillance, and depth of cover, and published the findings in the risk codes IGEM/TD/2 and PD 8010 Part3.

5. The development of IGEM/TD/2 and PD 8010 Part 3

During 2005 UKOPA identified the need to formally publish pipeline risk assessment methodologies to provide transparency and consistency when undertaking these assessments, and this resulted in the publication of two new codes in January 2009:-

i. IGEM/TD/2 Application of pipeline risk assessment to proposed developments in the vicinity of high pressure Natural Gas pipelines

and

ii. PD 8010 Parts 3 – Code of Practice for Pipelines, Guide to the Application of Risk Assessment to proposed developments in the vicinity of major accident hazard pipelines containing flammables – Supplement to PD 8010 Part 1 2004

These Standards provide guidance for the risk assessment of developments in the vicinity of major hazard pipelines and are specific to the calculation of safety risks posed to developments in the vicinity of pipelines in the United Kingdom (UK) classed as major accident hazard pipelines, but the principles of the risk calculation are generally applicable to risk assessment carried out for other purposes. The guidance does not cover environmental risks.

The guidance in these standards are provided for the benefit of pipeline operators, local planning authorities, developers and any person involved in the risk assessment of proposed new developments in the vicinity of existing major accident hazard pipelines. They are based on the established best practice methodology for pipeline risk assessment, and are intended to be applied by competent risk assessment practitioners.

6. Integrity related aspects of pipeline operations

A number of sub-groups have been formed to investigate a number of pipeline integrity related issues. These include a group reviewing the effects of dents on pipeline operation, particularly where pressure-cycling may causes fatigue. This has produced best practice guidance with the aim of advising operators on how to assess dents (depth, location, severity etc.) and to further assess potential fatigue effects based on pressure cycling.

A further sub-group is examining best practice guidance relating to sleeves installed around pipeline sections at various locations such as road or rail crossings. Guidance on prioritising the assessment of the condition of sleeves, and techniques for repair or replacement, are being considered by this group.

Recent developments of wind farms has resulted in cases where plans to locate wind turbines close to pipelines have been proposed. A sub-group has considered recommended separation distances between pipelines and the location of wind turbines, and UKOPA has published guidelines based on these recommendations.