Continuum risk-based asset integrity management system for geothermal steam pipelines: Kamojang Unit 4, Indonesia

Abstract

This work examines the use of pressure drop in geothermal steam lines using a continuum approach to the implementation of risk-based analysis. The study is performed by observing the behaviour of changes in pressure drop along the steam pipeline in the Kamojang geothermal field. The relevance of this study is in the context of the implementation of physical asset management based on the PAS 55 guidelines that emphasise risk-based management. This is using the risk-based inspection (RBI) method utilising the API RP-580 standard. Application of flow analysis as a continuum risk-based approach in asset integrity management system is feasible due to its ability to be performed while the equipment is online. It can serve as a first tear assessment before conventional pipeline thickness measurements for setting an effective and efficient maintenance program. This method is also suitable for pipelines that are difficult to access with conventional thickness measurement methods. Steam pipelines in dry fields can have a higher thining rate and effectively shortened life when compared with steam lines from two-phase and wet geothermal fields due to the limited silica carryover. The steam pipeline for Kamojang Unit 4 is in reasonable conditions to continue operating for its intended lifetime of 30 years. Steam washing with slightly mineralised (SiO2 and Cl rich) water/brine is recommended to extend the life of the pipeline.