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51314-3733-Experience with Standard Duplex Stainless Steel Seawater Pump in Arabian Gulf Seawater Conditions

Product Number: 51314-3733-SG
ISBN: 3733 2014 CP
Author: Sivuyile Funani
Publication Date: 2014
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Corrosion problems can be a serious issue in seawater pumps because of the aggressive nature of seawater. Usually damage in seawater can be minimized through use of highly corrosion resistant materials. Standard duplex stainless steels like type 2205 or cast CD4MCuN are frequently used in seawater pump construction because of their superior resistance to localized corrosion and higher strength compared to austenitic stainless steels which are a cheaper material option. Corrosion rates in chlorinated seawater depends on temperature and chloride content among other operation factors. The higher chloride content and cooling seawater temperature on the Gulf coast presents corrosion challenges that are unique to the region which can make materials that perform well in typical cooling seawater system to corrode under certain operating conditions. The failure of a vertical seawater cooling pump components made up of standard duplex stainless steel (type 2205 and cast CD4MCuN) after less than two years of intermittent operation is presented as an example of the poor performance of standard duplex stainless steels in Arabian Gulf cooling seawater. The shaft enclosing tube stud bolts and nuts of a seawater pump were found to be severely corroded. Results of lab analysis that includes optical microscopy hardness testing and chemical analysis (C/S XRF and water) done are presented. Analysis of the failed nuts and bolt indicated that they suffered from crevice corrosion with both ferrite and austenite being preferential attacked at different areas. Severe pitting of the impeller was also observed on the same pump. Only superficial pitting was observed on the four pumps that were operating continuously on the same pond as the one that failed. This failure illustrates that standard duplex stainless steels should be selected and used with care under the extreme gulf seawater conditions. Available literature on performance of standard duplex stainless steels in Arabian gulf conditions is also reviewed.
Corrosion problems can be a serious issue in seawater pumps because of the aggressive nature of seawater. Usually damage in seawater can be minimized through use of highly corrosion resistant materials. Standard duplex stainless steels like type 2205 or cast CD4MCuN are frequently used in seawater pump construction because of their superior resistance to localized corrosion and higher strength compared to austenitic stainless steels which are a cheaper material option. Corrosion rates in chlorinated seawater depends on temperature and chloride content among other operation factors. The higher chloride content and cooling seawater temperature on the Gulf coast presents corrosion challenges that are unique to the region which can make materials that perform well in typical cooling seawater system to corrode under certain operating conditions. The failure of a vertical seawater cooling pump components made up of standard duplex stainless steel (type 2205 and cast CD4MCuN) after less than two years of intermittent operation is presented as an example of the poor performance of standard duplex stainless steels in Arabian Gulf cooling seawater. The shaft enclosing tube stud bolts and nuts of a seawater pump were found to be severely corroded. Results of lab analysis that includes optical microscopy hardness testing and chemical analysis (C/S XRF and water) done are presented. Analysis of the failed nuts and bolt indicated that they suffered from crevice corrosion with both ferrite and austenite being preferential attacked at different areas. Severe pitting of the impeller was also observed on the same pump. Only superficial pitting was observed on the four pumps that were operating continuously on the same pond as the one that failed. This failure illustrates that standard duplex stainless steels should be selected and used with care under the extreme gulf seawater conditions. Available literature on performance of standard duplex stainless steels in Arabian gulf conditions is also reviewed.
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