Hydrogen Pressure Vessel Reinforcing Ring Design
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Solution Overview
Problem
Conventional pressure vessels storing hydrogen face issues with hydrogen environment embrittlement and fatigue cracks at screw-threaded portions due to direct contact with hydrogen, leading to reduced strength and ductility, and potential failure under internal pressure.
Innovation Solution
A pressure vessel design featuring a reinforcing ring fitted to the cylinder portion to cover the screw-threaded area, separating hydrogen from the screwable portion and reducing stress concentrations, along with a seal portion to enhance sealing and prevent deformation, thereby suppressing embrittlement and fatigue cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a screwable portion is used to close the cylinder portion, then the lid portion can be securely fixed, but hydrogen environment embrittlement occurs at the screw-threaded portion due to direct contact with hydrogen
Solution Approach 1:
A seal portion (O-ring) is introduced as an intermediary element between the lid portion and the cylinder portion. This seal portion prevents hydrogen from reaching the screw-threaded portion while still allowing the lid to be securely fixed through the screwable portion, thus resolving the contradiction between reliable securing and preventing hydrogen embrittlement
2Ease of operation
If the lid portion is held by the screwable portion, then the lid can be positioned, but stress concentrates at the screw-threaded portion causing fatigue cracks under internal pressure
Solution Approach 1:
The stress concentration problem is addressed by applying local quality enhancement through surface treatment (such as shot peening or rolling) at specific locations of the screw-threaded portion. This treatment creates compressive residual stresses locally at the thread roots, which counteracts the tensile stresses from internal pressure and prevents fatigue crack initiation, while maintaining the overall positioning function
3Stress or pressure
If high-strength low-alloy steel is used for the pressure vessel, then the vessel can withstand high pressure, but the screw-threaded portion becomes more susceptible to hydrogen embrittlement
Solution Approach 1:
The seal portion acts as a mediator that isolates the high-strength low-alloy steel screwable portion from hydrogen exposure. This allows the use of high-strength materials for pressure containment while the seal prevents hydrogen from causing embrittlement at the threaded connections
Data Source
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AI summary
A pressure vessel (10) is provided with: a cylinder part (1) that defines a pressure chamber (11); a screwing part (3) that is disposed inside at least one of the two ends of the cylinder part; a lid (2) that has a pressure-receiving surface (2A) facing the pressure chamber and that is disposed at a position closer to the pressure chamber than is the screwing part; and a reinforcing ring (4) that is fitted to the outer circumferential surface of the cylinder part. The reinforcing ring covers, along the axial direction of the cylinder part, a part on an outer circumferential surface (IF) corresponding to a portion or the entirety of the engaging portion (12) between the cylinder part and the screwing part.