| Abstract |
Corrosion has been an integral part of geothermal operations but this is usually associated with liquids or aqueous media. Corrosion is prevalent in condensate lines, branch lines of acid wells and injection wells handling acid or saline fluids. The rate by which the metal will thin out is addressed by providing enough corrosion allowance in the design and construction of the Fluid Collection and Reinjection Sysfem (FCRS) facilities and by installing mitigating measures such as caustic soda injection to sustain operations throughout its operating life. Ambient H2S in air conosion however l's usually not considered in the design considerationo f the FCRS. Moreover,t here is no esfab/ished rate by which the ambient air will corrode the surtace facilities. Based on Tongonan-l experience for the pasf 20 years, no significant problems related to ambient HrS in air were encountered in the FCRS facilities. The ambient HrS level in Upper Mahiao (UM) increased when the NCG from the power plant was diverted from ds sfackhead and drspersed through the Gas DispersionS ysfem (GDS) located at the Spray Tower. After the GDS became operational, the HzS levels in the ambient air increased within the vicinity of the spray tower from 0.01 to 5 ppm. This caused the corrosion observed in the electronic components (RNl and controllers) of the control equipment near the spray tower. Through metal coupons corrosion rate measurementsi,t was determinedt hat most of the ProcessO uf-Sfation( POS) and control stationsin the different LGPF FCRS with no GDS have low to moderate observed corrosion. ln Upper Mahiao, heavy to severe corrosion were obserued directly indicating that the UM GDS is the cause of the corrosion in the electronic components. The ambient air corrosion testing a/so revealed that the brass coupons were not significantly affected in mosf locations but the copper coupons were found to be susceptiblet o this type of corrosion.T he positivea ir and double door sysfem in POS100 in Upper Mahiao helped minimize corrosion in the fesf coupons comparedt o couponsr nsfall ed in other rooms in the same building without positive air and double door provision. The air filtration sysfem in the GDS building did not help in controlling corrosion because direct entry of outside air into the building was not prevented. |