Stress Analysis And Calculation Of The Shell Boiler Foot Ring And Ellipsoid Sealing Head And T Junction

The shell boiler is a kind of pressure vessel. The safety and efficiency must be considered in the product design. The strength calculation standard for pressure parts of boilers is mandatory and has a stronger legally binding requiment than other boiler standards. Therefore, the strength calculation is an essential job when designing the boiler and checking the safety.With the development of technology, the shell boiler pressure is improved to 3.8 MPa. But the present strength calculation standard GB/T 16508-1996 for pressure parts of shell boiler has been used for 14 years, some regulations are not reasonable. Hence, the standard has been revising since 2008. In this thesis, finite element method is used to analyze some parts strength and provide the basis for the standard to be revised.Based on the theory of elastic mechanics, the stress distributions of foot ring, the sealing head and the T junction under internal pressure are deduced by theoretical analysis. This work analyzes the stress of these parts and the stress distribution is obtained by the finite element software ANSYS?12.1. By performing stress linearization along the wall thickness, the stress intensity distribution results are obtained and evaluated.Based on the finite element analysis, the numerical results show that the stress of lateral support of U foot ring is the largest and S foot ring is the lowest. The force conditions of foot ring are improved when the boiler has a circular flue, throat, mouth circle, slag hole and other structures. While, the foot ring thickness can be calculated by the minimum thickness formula. If the thickness is less than furnace thickness, the furnace thickness is used. If these are circular flue, throat, mouth circle, slag hole and other structures, the thickness doesn't need to be calculated and the inner furnace thickness is directly used.Simulation results show that the biggest point of edge-sealing head happens on the peak of the long axis. The limiting condition expended from d / D_n≤0.6 to d / D_n≤0.7 is feasible.Simulation results also show that with the effect of internal pressure, the largest stress is located at the inside shoulder of the welded T junction which requires reinforcement. For the same diameter main pipe, the stress of straight tee is bigger than the reducing tee. The welded T junctions of seamless steel pipe is reinforced by an addtional thickness to the wall when they are in a boiler with the rated pressure not more than 3.8 MPa and an outer diameter of main pipe D_w≤273mm. Meanwhile, the welded T junctions of seamless steel pipe is reinforced with an addional thickness to the wall when they are in the boiler with the rated pressure not more than 2.5 MPa and an outer diameter of main pipe D_w≤426mm.