| Abstract |
A methodology has been developed for plant risk assessment of ageing geothermal fluid collection and disposal systems (FCDS) in Tongonan, Philippines, which is already in its 20th years of operations. The method applies the principles of risk-based inspection to the plant asset management practices. The plant risk assessment assigns each individual component within the plant a risk rating, which allows plant inspection and maintenance to be targeted and prioritised, both during operation and at scheduled shut downs. Assessment starts with quantifying the likelihood of corrosion and metallurgical damage, which has already, or is likely, to occur. Then the consequence of this damage occurring is quantified in terms of commercial, safety and environmental factors. Combination of these likelihood and consequence ratings give an overall risk rating for each component in the plant. In Tongonan, Phase 1 of the Risk Based Inspection programme provides a rigorous analysis on which to base an initial prediction of the remaining life of the individual components being assessed. Phase 2 involved actual inspection of identified components within the FCDS. Finally, Phase 3 is the continuous monitoring of the identified high-risk and high-consequence components, as well as potential high-risk areas. The immediate advantages are an ability to predict which items require detailed condition inspection, which are likely to require maintenance or replacement in a given timescale and which are suitable for immediate life extension beyond their design life. This has obvious cost benefit implications for the optimised and prolonged operation of the plant. |