Evaluation and Remaining Life Assessment of Separator and Demister in a Geothermal Power Generation Plant

Evaluation and remaining life assessment of separator and demister for 55 MW geothermal power generation plant have been conducted. The equipment has been used for 27 years and has stopped operating due to the failure of steam turbine. Before it is operated back, the condition of separator and demister needs to be evaluated and their remaining life assessment has to be calculated to anticipate the future repair. The methods used for evaluation were UT phased array, thickness measurement, chemical composition, hardness test and deposit composition analysis. The remaining life assessment was calculated in correlation with thickness reduction. The results showed that the chemical composition and hardness of materials met the standard of SA 516 Gr 70. No evidence of internal defect was found in both equipment. The demister in all part is still in good condition and its remaining life was beyond 20 years. In separator, the reduction in thickness extremely occurred on top head and cone. The remaining life of top head separator was below 1.2 years and cone separator was not more than 4.7 years. Deposit analysis taken from demister gave evidence the presence of sulfur, silica, iron oxide, and sulfide iron.