The Stress Analysis And Research For Non-radial Nozzle Of Pressure Vessel

The pressure vessels is a regular process equipment, it must be bored non-radial holesdue to the requirements of process and structure, at the same time, oval holes will be made inthe vessels. The results of the opening, not only weakened the strength of the pressure vesselwall, but also elevate stress concentration near the hole. In many cases, the peak stress is up toseveral times of the container membrane stress. So, how to analyze the stress concentrationnear the non-radial openings correctly, and adopt appropriate reinforcement is the subject ofpressure vessel design.In this paper, the non-radial opening structure is the research object, according to fourimpact factors, relational models were created to analyze. The impact factors as follow:non-radial angle, thickness of tubes, length of elongation and thickness of reinforcementrings.In this way, we can obtained the characteristics of stress distribution for the fourimpact factors.Some conclusions were obtained through the studies above:(1) Non-radial stress concentration factors increased significantly with the increase ofnon-radial angle, but not monotonically increasing. The stress concentration factors arerelatively high when the non-radial angles are between25and45.At the same time, we canknow that grinding the weld has positive effect for the elimination of the residual stress by thecomparative analysis for round chamfer.(2) Reinforcement for the tubes lead to a better situation for stress, but the thickness oftubes should not be blindly increased. When the thickness ratio increased to1.2, the effect ofreinforcement began to decrease. We think it is appropriately that the thickness ratio isbetween0.8and1.2.(3)The effect of internal stretching tubes is not so good. It is not necessary to stretch thetube. when the reinforcement meet the requirements. It is recommended that stretch lengthshould be less than0.5T.(4) The effect of reinforcement ring is better. However, reinforcing ring can increasethickness of vessel, resulting in increasing for the local bending stress, at the same time,reinforcement ring and cylinder can not be completely fit, so the anti-fatigue performance ofvessel is poor. By the results of finite element simulation, the conclusion can be made thatthickness of the ring is appropriate between0.8Tand1.2T.(5) On the basis of previous experiments, semi-empirical and semi-theoretical stress quick formulas are derived by the analytic geometry of space theory and regression analysismethod. It can be easily obtain the non-radial stress distribution by these relatively simpleformulas.