Development of the UKOPA Strategy for the Management of Ageing Pipelines

Abstract

The United Kingdom Onshore Pipeline Operators Association (UKOPA) was formed by UK pipeline operators in 1996 to provide a common forum for representing pipeline operators’ interests in the safe management of pipelines. This includes ensuring that UK pipeline codes include good practice, and that there is a common view in terms of compliance with these codes. To achieve this UKOPA has carried out a number of technical initiatives and studies to establish good practice requirements for UK operators which aim to ensure pipeline integrity is managed such that the risks posed by pipelines are as low as reasonably practicable (ALARP) in accordance with UK goal-setting safety legislation. UKOPA has developed Quantitative Risk Assessment (QRA) methodology which is published in UK standards and detailed guidance on the derivation of pipeline specific external interference failure frequencies, which have previously been published at IPC. The external interference frequency model is based on an analysis of data recorded in the UKOPA fault database which records product loss and damage data for UK major accident hazard pipelines from 1962 onwards. The database currently has a total length of 22,158 km of pipelines with over 877,598 km years of operating experience. The failure data is sparse, with only 192 product loss incidents, so where possible damage data and engineering failure models are used to develop reliable pipeline failure rates. To date this work has concentrated on the random failure causes of external interference and ground movement, which generate the major residual risk posed by pipelines in the UK. The majority of the UK pipeline population is now older than the original 40 years target design life. Consequently, the current UKOPA strategy is focused on the issues which affect the integrity and risk management of ageing pipelines. This requires the investigation of potential damage mechanisms which may affect older pipelines, including the impact of degradation of components which are no longer allowed by current standards, such as pipeline sleeves (casings), the degradation of damage which occurred during original construction and the assessment of the impact of material and weld quality standards typical of older pipelines. The work currently being undertaken by UKOPA involves first the assessment of the impact on integrity, then the development of engineering failure models, and finally the application of the models to the UK pipeline population to predict failure frequencies which are then compared with recorded data. This paper describes the assessment of the UKOPA damage data to identify indications of age related damage and deterioration trends, the development of practical integrity models for the assessment of pipeline sleeves and construction dents and the application of these models to the UK pipeline population. It also discusses an approach developed for UKOPA ethylene pipeline operators to assess population developments adjacent to existing pipelines.