Research Of Pressure Vessel Safety Based On Grey System Theory

More high-sulphur crude oil imported from Middle-east, the content of sulphur and acid in homemade oil is rising too, the corrosion is serious in refinery. Measured the corrosion pate with electric resistance probe, monitored sulfur value, salt value, salt value after desalt, acid value, iron ion value and pH value of cooling water. Carried on grey correlation analysis, calculated absolute, relative and synthetic degree of incidence, carried on predominance analysis too. For Shengli crude oil the main factor to the corrosion pate is acid value in crude oil, but for Middle-east oil the main factor is salt value after desalt.Measured the thickness of elbow by ultrasonic thickness meter, which is a quasi smooth sequence, accumulating generation operator is according to quasi exponent law. Established GM (1,1) model which passed error check is eligible. Adding a number to the sequence, then subtract it from the result, increased prediction precision. Used DGM and Verhulst model to simulate asway sequence, used GM (1, N) and GM (0, N) model to simulate corrosion and interrelated sequence, used GM (1, 1) model to predict the thickness in the future. Grey system model is feasible for eroding corrosion, can help for setting down overhaul period, and ensure safety.For exchangers rebuilding project, considered general tube-shell exchangers and helix- baffled structure, tube materials are 20 steel with TH847 coating, 20 steel aluminizing, 316L and dual phase steel. Considered heat transfer efficiency, manufacture fee, maintenance fee, safety and manufacture difficulty, carried on grey target decision, grey incidence decision and grey variable weight decision. Find that helix-baffled structure is better than common baffle structure; helix-baffled structure with 20 steel aluminizing tubes is the best preference plan.Fabricate difficulty is a prodigious grey number, aimed at helix-baffled exchangers with two courses in tube side, splitted one baffle into four parts, analyzed the tube holes'distributing, created mathematics model, compiled numerical controlled program with EIA code, realized numerical controlled process on Mitsubishi numerical controlled machine tool. This carried out the white number, lowered the cost, and ensured the security.