Operational experiences and asset management of geothermal pipelines at Wairakei

Abstract

Contact Energy has a risk-based monitoring programme on its pipelines, maintaining pressure integrity to ensure safe, reliable operation and compliance with legislation. The monitoring programme has been developed over time from technical knowledge and operational experience.
When the Wairakei geothermal field was first developed in the 1950s, there was no industrial knowledge for transporting geothermal fluids cross-country, particularly two-phase flow. Early scientific and metallurgical research established that low carbon steel was a suitable material for construction of pipelines and most steamfield equipment.
Once operation started, experience showed us what the damage mechanisms were, together with how to identify and monitor them. This knowledge was used to modify the inspection programme. Together with that, external and process threats such as tree fall, vehicles collisions, ground washouts and water-hammer events shaped how we operate and maintain our equipment. Minor improvements have been made to designs but sixty years of operational experience have proven the soundness of the early pioneers’ decisions. Combined, this has given the confidence to safely run the plant with a comprehensive management plan for the assets along with simple monitoring requirements.
This paper outlines some of the knowledge and those experiences, how these have shaped our approach to pipeline safety and how challenges are addressed.