柴油蒸汽发生器腐蚀开裂分析

Study on Corrosion Cracking of Two Diesel Steam Generators

检查两台加氢装置的柴油蒸汽发生器管板腐蚀开裂时,发现其腐蚀开裂机理都为碱脆,主要是在制造时管板焊接存在残余应力高,水质中Na+/PO34-的摩尔比控制不足(实际操作中Na+/PO34-的摩尔比应控制在2.5～2.8,而两台锅炉水中的Na+/PO54的摩尔比却大于2.8)导致游离NaOH的产生及温度等因素造成的腐蚀开裂。提出了防腐和改建措施:在制造时降低残余应力,同时使用pH-磷酸盐协调处理等方法控制水质中游离的NaOH产生;使用改进型的制造设计,预防和控制蒸汽发生器管板的腐蚀开裂。

The examination of the corrosion cracking of tube p]ates in two diesel steam generators found out that the corrosion mechanisms were caustic embrittlement mainly resulting from corrosion cracking due to higher residue stress in the fabrication wehtiug of tube plates because of insufficient control of Na^＋/PO4^3- molar ratio in water and temperature, etc （ The Na^ ＋/PO4^3- mole ratio should be controlled at 2.5 - 2.8. Whereas, the Na^ ＋/PO4^3 - mole ratio in boiler water is greater than 2.8 ） resuhing in corrosion cracking from the formation of fiee NaOH and temperature, etc. Con＇osion protection measures and revamping measures have been proposed：The residue stress should be reduced in fabrication, and pH -phosphate should be applied to control the formation of free NaOH in water, Fabrication design should be improved to prevent and control the corrosion cracking of tube plates of sleam generators.