循环水不锈钢换热器抗氯离子应力腐蚀研究

炼油、化工装置中换热器占总设备数量的40％左右，占总投资的30％-45％，换热设备中大约有1／3是水冷器，其中不锈钢换热器容易受循环冷却水中Cl-影响而发生应力腐蚀，这就制约着有污水回用的循环水系统提升浓缩倍数。通过调研得出这种腐蚀受Cl-的含量、温度影响较大，pH值也有一定的影响。文章提出了当温度为50-80℃及pH值大于8时，工业循环水的Cl一质量浓度最大可达1000mg／L。还介绍了列管式和盘管式换热器的应力腐蚀开裂情况，并依据对现场调研结果得出换热器易发生应力腐蚀的部位主要包括胀接部位、U形管的弯曲部位、折流挡板和换热管其它部位等。并建议在循环水系统内进行挂片试验进一步研究不同因素和换热器不同部位对应力腐蚀的影响，以便提出防护措施。

Study on Resistance Against Stress Corrosion off Chlorine Ions of Cooling Water Stainless Steel Heat Exchangers

The heat exchangers in petroleum refineries and chemical plants account to about 40% of the total equipment quantity and 30%～45% of total equipment investment.In heat exchange equipment,one third is water cooler.The stainless steel heat exchangers are subject to stress corrosion caused by Cl-in cooling water,which will limit the increase of concentration of cooling water system.The investigation study confirms that the Cl-content and temperate have a greater impact on the corrosion and pH value also has a certain influence.At a temperature of 50～80 ℃ and pH value of 8,the maximum mass concentration of Cl-in industry cooling water can be as high as 1000 mg/L.The stress corrosion cracking(SCC) of tube heat exchangers and coil heat exchangers is introduced.The field investigation has found that the locations which are subject to stress corrosion in heat exchanger are mainly expanded connections,bent of U tube,rod baffles,heat exchanger tubes,etc.It is suggested to have coupon testing in cooling water system to further study the impact of different factors and different locations on stress corrosion so as to propose appropriate corrosion protection measures.