Abstract
Welded joints are analysed as critical regions in a pressure vessel in respect to structural failure due to the elastic-plastic fracture/crack growth. To assess structural integrity of pressure vessels used in chemical industry the risk based procedure has been introduced and applied in the case of a large spherical pressure vessel used as a vinyl-chloride monomer (VCM) storage tank in HIP Azotara Pancevo. The risk matrix has been used, taking into account the basic definition of risk, being the product of the probability and consequence, and applied to different regions of welded joints, having different mechanical properties, i.e. crack resistance. To estimate probability, the failure assessment diagram (FAD) has been used, as an engineering tool, defined according to the position of the operating point for different regions of the welded joint, relative to the critical point on the limit curve. Generally speaking, consequence is estimated based on pressure vessel parameters, or by detailed analysis of health, safety, business and security issues, but in the analysed case, the worst case scenario is assumed, with the highest consequence due to potential disaster for environment and fatalities.
Highlights
Crack-like defects are the biggest risk in operating large pressure vessels, i.e. storage tanks in chemical industry, as explained and described in [1]
To assess structural integrity of pressure vessels used in chemical industry the risk based procedure has been introduced and applied in the case of a large spherical pressure vessel used as a vinyl ¬chloride monomer (VCM) storage tank in HIP Azotara Pančevo
To overcome the gap between engineers and managers, there is a need to provide simple, e.g. risk based structural integrity assessment of all cases involving crack-like defects, especially if toxic and/or flammable storage medium is used such as vinyl chloride monomer (VCM)
Summary
Crack-like defects are the biggest risk in operating large pressure vessels, i.e. storage tanks in chemical industry, as explained and described in [1]. These defects are likely to appear in welded joints because of complex microstructure in different regions (Base Metal – BM, Weld Metal – WM, Heat Affected Zone – HAZ), being more or less sensitive to cracking. Disregarding their potentially disastrous effect is not an option. There are a number of formal methods for eliciting expert judgement, which provide an aid to the formulation of appropriate questions
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