Engineering Failure Analysis 47(2015)162-177 Contents lists available at Science Direct VGINEFNING Engineering Failure Analysis ELSEVIER journalhomepagewww.elsevier.com/locate/engfailanal Failure analysis on circulating water pump of duplex stainless steel in 1000 MW ultra-supercritical thermal power unit Yue-Yue Ma, Shi Yan, Zhen-Guo Yang Guo-Shui Qi, Xin-You He b Zhejiang Zhengneng Jiaxing Electric Power Co, LTD, Jiaxing, Zhejiang Province 314201, PR China ARTICLE INFO A BSTRACT With a large number of properties suc mechanical properties and excellent corrosion resistance, 2205 duplex stainle SS)has been extensively used in many eived in revised form 29 September 201 industries for the last decades. However welding procedures will induce embrit Available online 23 October 2014 tlement of the weld joint, seriously decreasing the safety reliability of the weld joint. In this study, lots of unexpected fractures occurred on 2205 DSS which was used as the materia for making circulating water pump(CWP)in an ultra-supercritical thermal power plant of stainless steel (Dss) China for the first time. By means of diverse characterization methods, comprehensive Fracture investigation was carried out on the failed CWP. Analysis results reveal that many lack Circulating water pump penetrations(LOPs)in the weld joint and unbalance ferrite/austenite ratio induced by r welding procedures should be responsible for the fracture of the CWP. And effective countermeasures and suggestions were also proposed. So the analysis results have instructive significance for the fracture prevention of the CwP, even for ensuring safety operation of other equipment under similar seawater environment. e 2014 Elsevier Ltd. All rights reserved. 1 Introduction As one of the largest thermal power plants in the eastern part of China, Jiaxing power plant phase lll has two 1000 MW ltra-supercritical thermal power generating units, which are named by 7# and 8#f, respectively. these two units were put into commercial operation on June 23, 2011 and October 20, 2011, respectively, contributing a lot to the development local economic development. irculating water system is an important facility in a thermal power generating unit, which is used to pump seawater and then to feed seawater into a condenser to cool exhaust steam by heat exchange. Hereby, each of the two units of Jiaxing power plant phase lll was equipped with three CWPs, named 7A, 7B, 7C and 8A, 8B, 8C, respectively, all of which have same structure, designed and manufactured by Hitachi Pump Manufacture(Wuxi)Co., Ltd Fig. 1(a)and Fig. 1(b) show the external appearance and the structure of 8A CWP respectively Since the surrounding of the CWP's shell is natural seawater which usually contains high contents of salts, chloride ions and sediment particles, it requires a high performances such as excellent corrosion resistance and good mechanical proper ties for the material used in the cwps so dss is one of the best choices in this condition. In China. 2205 DSS was the first time used as the material of CWPs in thermal power plants. Corresponding author. Tel: +86 21 65642523: fax: +86 21 65103056. E-mail address: zgyangefudanedu cn(Z -G Yang). http://dxdoiorg/10.1016/jengfailanal2014.09.014 1350-6307/0 2014 Elsevier Ltd. All rights reserved.Failure analysis on circulating water pump of duplex stainless steel in 1000 MW ultra-supercritical thermal power unit Yue-Yue Ma a , Shi Yan a , Zhen-Guo Yang a,⇑ , Guo-Shui Qi b , Xin-You He b aDepartment of Materials Science, Fudan University, Shanghai 200433, PR China b Zhejiang Zhengneng Jiaxing Electric Power Co., LTD, Jiaxing, Zhejiang Province 314201, PR China article info Article history: Received 4 April 2013 Received in revised form 29 September 2014 Accepted 30 September 2014 Available online 23 October 2014 Keywords: Duplex stainless steel (DSS) Fracture Circulating water pump Failure analysis abstract With a large number of properties such as good mechanical properties and excellent corrosion resistance, 2205 duplex stainless steel (DSS) has been extensively used in many industries for the last decades. However, improper welding procedures will induce embrit￾tlement of the weld joint, seriously decreasing the safety reliability of the weld joint. In this study, lots of unexpected fractures occurred on 2205 DSS which was used as the material for making circulating water pump (CWP) in an ultra-supercritical thermal power plant of China for the first time. By means of diverse characterization methods, comprehensive investigation was carried out on the failed CWP. Analysis results reveal that many lack of penetrations (LOPs) in the weld joint and unbalance ferrite/austenite ratio induced by improper welding procedures should be responsible for the fracture of the CWP. And effective countermeasures and suggestions were also proposed. So the analysis results have instructive significance for the fracture prevention of the CWP, even for ensuring safety operation of other equipment under similar seawater environment. 2014 Elsevier Ltd. All rights reserved. 1. Introduction As one of the largest thermal power plants in the eastern part of China, Jiaxing power plant phase III has two 1000 MW ultra-supercritical thermal power generating units, which are named by 7# and 8#, respectively. These two units were put into commercial operation on June 23, 2011 and October 20, 2011, respectively, contributing a lot to the development of local economic development. Circulating water system is an important facility in a thermal power generating unit, which is used to pump seawater and then to feed seawater into a condenser to cool exhaust steam by heat exchange. Hereby, each of the two units of Jiaxing power plant phase III was equipped with three CWPs, named 7A, 7B, 7C and 8A, 8B, 8C, respectively, all of which have same structure, designed and manufactured by Hitachi Pump Manufacture (Wuxi) Co., Ltd. Fig. 1(a) and Fig. 1(b) show the external appearance and the structure of 8A CWP respectively. Since the surrounding of the CWP’s shell is natural seawater which usually contains high contents of salts, chloride ions and sediment particles, it requires a high performances such as excellent corrosion resistance and good mechanical proper￾ties for the material used in the CWPs, so DSS is one of the best choices in this condition. In China, 2205 DSS was the first time used as the material of CWPs in thermal power plants. http://dx.doi.org/10.1016/j.engfailanal.2014.09.014 1350-6307/ 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +86 21 65642523; fax: +86 21 65103056. E-mail address: zgyang@fudan.edu.cn (Z.-G. Yang). Engineering Failure Analysis 47 (2015) 162–177 Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal