重催油浆换热器管板开裂的应力腐蚀失效

锦州石化六厂的重催油浆换热器,在投入使用半年多就在浮头管板处出现多处裂纹,裂纹大多从管束开始呈环状沿径向管板延伸,导致不能正常生产,造成较大的经济损失。介绍了此换热器的工艺条件,对开裂的浮头管板进行断口宏观形貌、微观形貌、准解理微观形貌、腐蚀产物和管桥部位裂纹分析,并得出应力腐蚀是引起重催油浆换热器管板开裂的重要原因之一。分析油浆换热器管板受力和腐蚀环境:管板在焊接残余应力、温差应力、气-液两相流的诱导振动及装配应力的相互叠加作用下,受拉应力;在高温环烷酸和高温重硫醇、重硫醚的腐蚀环境中,导致应力腐蚀开裂。

STRESS CORROSION FAILURE ON CCU TUBE- PLATE FRACTURE OF SLURRY HEAT EXCHANGER

According to heavy catalysis slurry heat exchanger in the No.6 petrochemical corporation of Jinzhou,there were a lot of cracks in tube-plate of slurry heat exchanger after it was used about half a year and the cracks mostly started from the tube bundle in the form of annulus and propagated in radial direction.As a result,it caused unnormal production and large economic losses.The process conditions of CCU slurry heat exchanger were introduced and the reason of fracture in tube-plate was analyzed through the macro and micro-image of CCU tube-plate fracture,cracks of pipe bridge,quasi-cleavage fracture micro-image and the corrosion products of tube-plate fracture.In the end,the conclusion that the stress corrosion was one of the important reasons of the fracture in the CCU tube-plate was drawn.By the stress and corrosion condition analysis of tube-plate,the tube-plate is borne tension stress under superimposition of the welding residual stress,thermal stress,vibration induced by gas-liquid phase flow and the assembly stress.Thus stress corrosion fracture takes place under the condition of hyperthermia naphthenic acid,hyperthermia mercaptan and sulfide.