Hydrogen Tank Pressure Control for Embrittlement Prevention
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Solution Overview
Problem
Hydrogen embrittlement poses a risk to stainless steel tanks used for transporting liquid hydrogen, leading to potential cracking, and existing solutions either use more expensive materials or fail to adequately manage pressure changes as the tank is emptied.
Innovation Solution
A method and device that continuously measure temperature and liquid level in the tank, automatically limiting pressure to a threshold between 1.5 and 3 bar when the temperature exceeds -140°C to -160°C and the liquid level drops, using a system with temperature and pressure sensors connected to an electronic control system for gas venting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If stainless steel materials such as 304L or 304N are used to reduce cost and weight, then manufacturing cost and weight are reduced, but the tank becomes susceptible to hydrogen embrittlement and cracking
Solution Approach 1:
The invention changes the pressure parameter to prevent hydrogen embrittlement. By maintaining tank pressure below a critical threshold (e.g., 15 bar or 20 bar depending on steel grade), the chemical potential of hydrogen is reduced, preventing it from reaching concentrations that cause embrittlement in the steel microstructure. This allows use of lighter, cheaper steels like 304L or 304N that would otherwise be unsuitable.
Solution Approach 2:
The invention implements preliminary action by pre-establishing pressure limits before hydrogen embrittlement can occur. Pressure control measures are taken in advance during filling and operation to ensure hydrogen partial pressure never reaches critical levels that would initiate embrittlement processes in the steel material.
2Reliability
If pressure control measures are implemented to prevent embrittlement, then reliability is improved, but device complexity increases due to additional sensors and control systems
Solution Approach 1:
The invention implements feedback control by continuously monitoring tank pressure using pressure sensors and comparing readings against pre-determined critical thresholds. When pressure approaches the embrittlement risk threshold, the system automatically triggers venting operations through control valves to maintain pressure below critical levels, creating a closed-loop safety system.
Solution Approach 2:
The system performs self-service safety functions by automatically monitoring and controlling pressure without requiring external intervention. The electronic control system autonomously manages pressure control valves and venting operations based on sensor inputs, eliminating the need for manual pressure management while ensuring embrittlement prevention.
3Productivity
If the tank is emptied to deliver liquid hydrogen, then productivity is improved, but pressure increases and liquid level drops causing embrittlement risk
Solution Approach 1:
The invention applies dynamics by adapting pressure control strategy during the emptying process. As liquid level drops and vapor space increases during delivery operations, the system dynamically adjusts pressure management to account for changing conditions. Pressure control valves and venting systems are activated during emptying to maintain safe pressure levels despite the increasing risk of embrittlement as liquid level decreases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces the risk of tank embrittlement by maintaining a safe pressure range for the steel, allowing the use of less expensive and lighter stainless steel materials while preventing cracking during hydrogen transport.
Implementation Method 1
comprises a temperature sensor located in the upper part of the tank
Implementation Method 2
comprises a pressure sensor
Implementation Method 3
a member for selectively venting gas to the exterior of the tank
Data Source
AI summary
Method for controlling the pressure in a transportable cryogenic tank (1), especially a tank (1) mounted on a transportable platform (2) capable of being moved by a truck, the tank (1) being made of steel and containing pressurized liquid hydrogen, the method comprising at least one of the following: continuously or periodically measuring the temperature in the tank (1) and continuously or periodically measuring the level of the liquid in the tank and, when the measured temperature exceeds a set upper temperature threshold (Ts) lying between minus 140° C. and minus 160° C., and, respectively, when the liquid level in the tank drops below a set liquid level threshold, the pressure in the tank (1) is limited to a value less than or equal to a set pressure threshold (Pmax) lying between 1.5 and 3 bar.