Integrity Management of Flange Connections Using Reliability Model

Abstract

There is demonstrated potential for failures to occur on station piping assets in facilities, therefore it is critical to take measures to manage preventable releases. In 2018, Enbridge developed a reliability model that uses available asset information to quantify the likelihood of failure of station piping assets. Enbridge based this model on the CFER PIRIMID software, with some modifications to minimize the use of default values and to meet the company’s integrity management program requirements. With successful implementation of station piping model, Enbridge realized opportunity to develop a much-needed flange model leveraging the station piping model. Historical leak data indicates that flanged connections often experience a higher leak frequency than other assets in a facility. While there are industry guidelines that provide guidance for the assembly of process flange connections in a facility, there are few that discuss integrity management of flange connections once they are operational. Most published condition assessment flange models require inputs which are not readily available, e.g. condition of flange faces and gaskets. These inputs often require the flange to be disassembled just to obtain the data. For pipeline operators, data gathering is even more challenging as there are stations (with numerous flanges) that are spread out along the entire pipeline. Given the high number of flange connections and their wide variation in parameters within transmission pipeline facilities, there is benefit in developing a reliability-based model to guide the integrity management of flange connections. A reliability model that works in two stages was developed for this purpose. The pre-inspection assessment stage was designed to utilize available inputs to prioritize groups of flanges for inspection, and the post-inspection assessment (second) stage is then applied to select the specific flanges that require maintenance action. Enbridge utilized industry guidelines, relevant standards, historical failure data, and subject matter experts’ inputs to develop the station piping and flange models. This paper will discuss the design concepts, model architectures, the contributing factors, and their sensitivities to the likelihood of failure results. These concepts may be utilized by any operator managing such assets, and the model designs may be tailored to suit a wide range of facility environments.