Research On Failure And Risk Analysis Of Carbon Steel Condenser Based On Indirect Cooling Open System

Carbon steel condenser is a common type of shell and tube heat exchanger,which usually uses water or air as the coolant to remove heat.It is widely used in petroleum,refrigeration,power and metallurgy field,etc.Due to the large cooling ability of water,and the indirect open recirculating cooling water system consumes less water compared to the direct open recirculating cooling water system,which is consistent with the principle of water conservation in China,the indirect open recirculating cooling water system is often preferred in the industry.Therefore,it is of great engineering significance to study the carbon steel condenser based on the indirect open recirculating cooling water system.At present,carbon steel condenser is gradually developing in the direction of high temperature,high pressure,and large-scale.After long-term operation of the indirect open recirculating cooling water system,there are also problems such as water quality decline or even serious deterioration,resulting in frequent safety accidents,and the severely damaged of personal safety and economic benefits.Therefore,the safety research on carbon steel condenser is urgently needed.In this paper,the failure and risk analysis of a carbon steel condenser in an oil refinery are carried out,which can provide a theoretical reference for preventing the failure of the same type of condenser.By observing the on-site inspection of the carbon steel condenser and combining the analysis results of the shell-side medium composition,it was clear that there was no connection between the failure of the tube bundle perforation and the flash tower top gas of the shell-side.Through monitoring and analyzing the main water quality indicators of the indirect open recirculating cooling water system for one year,it was founded that the tendency to scale of recirculating cooling water was strong.Through inductively coupled plasma optical emission spectroscopy and ion chromatography analysis of the corrosion products,it was determined that the recirculating cooling water contained inorganic salt scale such as calcium carbonate.Through chemical composition analysis and metallographic examination of the perforated failed tube bundle,it was judged that the matrix was qualified.The corrosion products in the tube were observed with macro and micro morphology inspection,energy spectrum analysis,X-ray fluorescence analysis and X-ray diffraction analysis to confirm that dissolved oxygen corrosion and microbial corrosion occurred inside the tube bundle universally.The scale layer on the inner wall of the tube bundle was mainly composed of inorganic salt scale,corrosion scale and biological slime scale,which caused serious under-deposit corrosion.The highly corrosive chloride ion can exacerbate the auto-catalyzing acidification effect of the occluded area under the scale,which caused the tube bundle to perforate in a short time.The failure fault tree was established around the carbon steel condenser systematically and completely.The qualitative analysis results showed that the system was dangerous and there were many failure paths.With the help of Bayesian network model,the carbon steel condenser was quantitatively analyzed to obtain the failure probability of the system nodes and the posterior probability of the root nodes to find the key risk factors that affected the failure of the system,so as to formulate targeted control measures and prevent or resolve various risks in the operation of the equipment.