Safety Assessment Of In-service Pressure Vessel Comprising Defect

With the rapid development of modern industry, pressure vessel plays an increasingly critical role in the petroleum?chemical?marine engineering and shipbuilding. Pressure vessel also plays an important role in marine propulsion system.The failure of pressure vessel often leads to trouble. For pressure vessel in service,a small crack at the welding position even causes the eventual destruction of the whole structure.Therefore, the safety assessment of pressure vessel containing defects is necessary. Safety assesment standards such as BS7910, GB/T19624-2004 and SINTAP which are based on "fitness for purpose" have been implemented. The wide use of these standards ensures less incidents occurred. Meanwhile,manpower and material resource have been saved.BS7910 is mainly used in the safety assessment of submarine oil pipeline in domesic application.In this paper, gas cylinder in service is chosen as the research object. The latest British Standard BS7910 and finite element method are used to evaluate the semi-elliptical surface crack of gas cylinder.The safety assessment of gas cylinder using BS7910 proves its effectiveness in pressure vessel.The main contents are as follows:1. Safety assessment about defects of BS7910 is introduced in detail.2. Mechanical properties and response of pressure vessel in actual working conditions are studied by using finite element method. Stress components such as membrane stress and bending stress are obtained through finite element method. Afterwards the safety assessment of the pressure vessel with defects is implemented.3. Fatigue assessment of pressure vessel is conducted by using ANSYS and relevant specification. In the case of a known initial flaw size, the remaining life (crack propagation life) of the pressure vessel is calculated by assessing the critical size of flaw.