Development of Guidelines for Parallel Pipelines

Abstract

Due to the increasing demand for natural gas in many locations, there is often a need to increase the capacity of existing and future gas transmission pipeline networks. In some situations, there may be a possibility of increasing the operating pressure (e.g. uprating), but in others there may be no alternative but to lay new pipelines, often along the same route as an existing pipeline. If one pipeline fails in this situation, it is possible that a second parallel pipeline may also fail as a result. However, there is also increasing pressure on the use of land and therefore the minimum separations with which pipelines may be laid and operated safely when in parallel to other pipelines need to be considered. This paper describes work carried out as a collaborative project supported by gas transmission pipeline operators to provide guidance on the likelihood of failure of a pipeline, for a range of different conditions, following failure of an adjacent pipeline. A framework has been developed that identifies the sequence of events that could lead to failure of a parallel pipeline, including the possibility of escalation from a leak (or puncture) to a full bore rupture. Work has been carried out including large scale experiments and CFD (Computational Fluid Dynamics) modelling to enable the critical processes in the framework to be quantified. This methodology has been used to produce general guidelines for parallel pipeline assessments, in order to support the design of new parallel pipeline installations. The methodology has been developed specifically for parallel natural gas transmission pipelines. However, the principles are relevant to parallel pipelines transporting other substances, and consideration is given to how the methodology may be adapted for such circumstances. The methodology provides input to any risk assessments of parallel pipeline installations, to quantify the possible contribution to the failure frequency from escalation. General guidance developed using the methodology presented in this paper, has recently been included in the recommendations for steel transmission pipelines, IGEM/TD/1 (Edition 5), published by the Institution of Gas Engineers and Managers. However, where general recommendations are not achievable, the methodology may be applied to take site and pipeline-specific factors into account.

Underground parallel pipelines domino effect: An analysis based on pipeline crater models and historical accidents

“…The rupture of an underground gas or liquefied product pipeline occurs with the formation of a ground crater by the source jet [4,5,6]. When the released gas ignites, the fire will develop inside the crater [7].…”

“…In this instance, there is the possibility of the domino effect [8]. According to [5], among twelve incidents involving a rupture of underground pipelines, one incident was reported in which domino effect was believed to have occurred.…”

“…In this paper, among 17 accidents involving underground parallel pipelines, two cases of domino effect have been identified. To prevent underground parallel pipelines domino effect, it is necessary to define minimum separations between two or more pipelines adjacent to gas pipelines, or to implement mitigating measures ensuring that they may be arranged and operated safely [5,9,10].…”

“…However, pipeline 3 would be subject to a ground pressure load during the crater formation and a thermal load caused by the jet fire in case of ignition. Therefore, the safety of pipeline 3 will depend on whether it can withstand these loads without losing its integrity [5,7]. Figure 3).…”

A model for the initial stages following the rupture of a natural gas transmission pipeline

“…As described in Acton et al (2010a), finite element models have been used for this purpose assuming a range of surrounding soils. The results from these detailed calculations have been analysed and a series of correlations have been produced to fit the results for global parameters describing the craters, such as their length, width and depth.…”