Tangent Radius Nozzle Assembly for Pressure Vessel Stress Reduction
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Solution Overview
Problem
Pressure vessels, such as boiler drums, face stress concentrations at the intersection of pipes and the shell due to cyclic thermal and mechanical stresses, limiting their operational cycles and lifetime due to fatigue and magnetite layer cracking.
Innovation Solution
A nozzle assembly with a radius geometry tangent to the inner and outer surfaces of the pressure vessel walls, optionally including an integral flange, is designed to reduce stress concentrations through finite element analysis, ensuring the weld area is outside high-stress regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional nozzle with sharp corners is used at the intersection of the pipe and pressure vessel shell, then the manufacturing is simpler, but stress concentrations occur leading to higher stresses and reduced lifetime
Solution Approach 1:
The nozzle incorporates a rounded end portion with a radius that is substantially tangent to the inner surface contour of the pressure vessel wall, replacing sharp corners with curved surfaces to eliminate stress concentrations at the intersection of the pipe and vessel shell
Solution Approach 2:
The nozzle geometry is locally optimized at the intersection area with a specific radius configuration that is tangent to the vessel wall contour, while the rest of the nozzle body maintains standard cylindrical geometry, applying complexity only where needed to reduce stress
2Adaptability or versatility
If the nozzle operates under cyclic thermal and mechanical stresses, then the pressure vessel can handle pressure and temperature changes, but the stress concentrations limit the number and magnitude of cycles the vessel can withstand
Solution Approach 1:
The rounded end portion with tangent radius geometry distributes cyclic thermal and mechanical stresses more evenly throughout the nozzle-vessel intersection, preventing stress concentration points that would initiate fatigue cracks during repeated pressure and temperature cycles
Solution Approach 2:
The nozzle geometry is designed in advance with a tangent radius at the intersection to preemptively cushion against stress concentrations before cyclic loading begins, protecting the weld area and vessel shell from fatigue damage during operational cycles
Data Source
AI summary
In a nozzle and a nozzle assembly, for use in a pressure vessel, stress analysis is used to determine areas of stress concentration. The nozzle is configured to reduce these stress concentrations.