There is demonstrated potential for failures to occur on station piping assets in facilities, therefore it is prudent to take measures to manage preventable releases. In 2018, Enbridge developed a reliability model that uses readily available asset information to quantify the likelihood of failure of station piping assets. With successful implementation of the station piping model, and a follow-on flange reliability model, Enbridge realized opportunity to develop a much-needed auxiliary piping reliability model.

Auxiliary piping assets may be defined as piping systems connected to the main process flow piping which provide specific operational functionality (instrumentation, drains, pressure relief pathways, etc.) but are not part of the normal process flow path. These assets may contain components such as flanges, valves, fittings, threaded or welded connections, fittings, small diameter piping/tubing, or flex hoses.

Historical leak data indicates that auxiliary piping assets experience a higher leak frequency than other assets in a facility.

While there are industry guidelines that provide description of the individual components of auxiliary piping assets, there are few that discuss integrity management of auxiliary connections as a unit once they are operational. Previously published auxiliary piping models require inputs which are not readily available, e.g., condition of threads, welds, internal corrosion, etc. which often require on-site inspection. For pipeline operators, field data gathering is costly and challenging given stations are spread out over numerous km’s.

Given the high number of auxiliary piping assets and their potentially wide variation in parameters, there is benefit in developing a reliability-based model to support the planning phase of a risk-based integrity management program. A reliability model that works in two stages has been developed for this purpose. The pre-inspection assessment (first) stage is designed to prioritize groups of auxiliary piping assets on a station piping segment for inspection, and the post-inspection assessment (second) stage is then applied to select the specific assets that require maintenance action.

The model development considered industry guidelines, historical failure data, and subject matter experts’ inputs. This paper will discuss the design concepts, model architectures, the contributing factors, and their sensitivities to the likelihood of failure results. Through this paper, the auxiliary piping model may be applied by any operator managing such assets.

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