Pressure Vessel Nozzle Lip Design for Stress Reduction
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Solution Overview
Problem
Pressure vessels used in cyclic pressure applications, such as Pressure Swing Adsorption (PSA) systems, experience high stress concentrations at nozzles, leading to the need for thicker components to withstand fatigue, which increases weight and cost without adequate consideration of weld stress distribution.
Innovation Solution
A nozzle design with specific geometric ratios and weld placement to reduce stress concentrations, allowing for thinner vessel walls and easier maintenance, while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional nozzle design is used in cyclic pressure applications, then stress concentrations at nozzles increase, but vessel wall thickness must be increased to withstand fatigue
Solution Approach 1:
The nozzle design applies local quality by creating a contoured lip region with specific geometric ratios (first distance 0.75t-4t, second distance 0.5t-2t, third distance 0.5t-3t) that locally modifies stress distribution. This localized geometric optimization at the nozzle-vessel interface reduces stress concentrations without requiring global thickening of vessel walls, thereby maintaining fatigue resistance while reducing overall vessel weight.
Solution Approach 2:
The invention changes geometric parameters of the nozzle structure, specifically defining the lip contour through three critical distance parameters relative to wall thickness t. By optimizing these dimensional parameters (first distance 0.75t-4t, second distance 0.5t-2t, third distance 0.5t-3t), the design alters the stress field distribution locally, enabling reduced vessel wall thickness while maintaining required fatigue strength.
2Strength
If thicker vessel components are used to account for cyclic stresses, then fatigue resistance improves, but manufacturing cost increases
Solution Approach 1:
Instead of uniformly thickening all vessel components, the invention applies local quality by concentrating geometric optimization specifically at the nozzle lip region. The contoured lip with optimized distance parameters (first distance 0.75t-4t, second distance 0.5t-2t, third distance 0.5t-3t) locally manages stress, allowing standard thickness elsewhere and reducing overall material cost while maintaining fatigue resistance.
Solution Approach 2:
The nozzle is segmented into distinct functional regions: the contoured lip region with optimized geometry for stress management, the barrel section for fluid flow, and the connection interface. This segmentation allows each region to be optimized independently, with the lip region bearing the stress management function while other regions maintain standard design, reducing overall manufacturing cost.
3Strength
If welds are placed in high stress areas to ensure structural integrity, then strength is maintained, but stress concentration increases
Solution Approach 1:
The contoured lip geometry is designed in advance to create a stress-gradient zone that progressively transitions from the high-stress nozzle interior to the lower-stress vessel wall. The optimized distance parameters (first distance 0.75t-4t, second distance 0.5t-2t, third distance 0.5t-3t) pre-position the weld zone in a region of reduced stress concentration, allowing structural integrity without exacerbating stress peaks.
Solution Approach 2:
The contoured lip introduces curved geometric transitions instead of sharp corners or abrupt changes. This curvature distributes stress more evenly across the weld zone, reducing stress concentration factors while maintaining structural integrity. The smooth transitions defined by the distance parameters eliminate stress risers that would otherwise concentrate at the weld interface.
Data Source
AI summary
A nozzle for a pressure vessel can include a lip design that facilitates an improved reduction in stress at a location at which the nozzle can be joined to the vessel. Embodiments can include a contoured annular lip element for attachment to an end of a vessel to position a nozzle within an opening at an end of the vessel for fluidly connecting the vessel to another plant element. The nozzle can include one or more geometries to position a weld for joining the nozzle to the end of the vessel so that the weld is located at a pre-selected location to experience a pre-selected level of stress during operation of the vessel to facilitate use of a vessel having a reduced overall wall thickness to provide a vessel having an overall lower weight and capital cost while also improving the ease with which maintenance can be performed.