NMR Helium Tank Pressure Control Using Dual Pressure Sensors
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Solution Overview
Problem
Existing pressure regulation systems in helium tanks of NMR magnets are inefficient and unsafe due to fluctuations in atmospheric pressure, leading to artifacts in NMR measurements, loss of helium, and potential system failures.
Innovation Solution
A dual-pressure sensor system that adjusts the helium tank pressure based on both internal and external pressures, using a control device to maintain a stable setpoint through incremental changes, ensuring operational safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed pressure setpoint is used to maintain constant helium tank pressure, then measurement stability is improved, but operational safety deteriorates when atmospheric pressure fluctuates significantly
Solution Approach 1:
The patent applies dynamics by making the pressure setpoint adjustable and adaptive rather than fixed. The control device dynamically modifies the setpoint based on the measured pressure difference between the helium tank and atmosphere, allowing the system to adapt to varying atmospheric conditions while maintaining safe operation margins
Solution Approach 2:
The patent implements feedback by using a pressure sensor to continuously measure the pressure difference between the helium tank and atmosphere, and feeding this information back to the control device. The control device then adjusts the setpoint accordingly, creating a closed-loop control system that responds to actual operating conditions
2Reliability
If atmospheric pressure is monitored and setpoint is adjusted dynamically, then operational safety is improved, but device complexity increases
Solution Approach 1:
The patent uses a differential pressure sensor as an intermediary that directly measures the pressure difference between the helium tank and atmosphere. This simplifies the system by eliminating the need for separate absolute pressure sensors and complex calculations, as the intermediary device provides the exact information needed for safe operation
Solution Approach 2:
The patent changes the control parameter from absolute pressure to pressure difference. By controlling the setpoint as a pressure difference value rather than an absolute pressure value, the system becomes more robust to atmospheric variations while requiring simpler sensing and control logic
3Reliability
If pressure relief valve is used to prevent air intake, then safety is improved, but helium loss increases during atmospheric pressure drops
Solution Approach 1:
The patent applies preliminary action by proactively adjusting the pressure setpoint in response to detected atmospheric pressure drops, before the pressure difference becomes large enough to trigger the pressure relief valve. This preventive approach maintains safety margins while avoiding unnecessary helium venting
Solution Approach 2:
The patent enables the system to skip the intermediate state where excessive pressure difference would trigger safety valve activation. By dynamically adjusting the setpoint to maintain an appropriate pressure difference, the system rushes through the dangerous state space and maintains operation in the safe, efficient region
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
The system provides stable helium tank pressure, preventing helium loss and system failures, while maintaining efficient helium use and reducing measurement artifacts.
Implementation Method 1
a pressure sensor arranged inside the cryostat, by which the pressure difference between an interior of the helium tank and atmosphere can be determined
Implementation Method 2
the control device is configured to change a setpoint for the pressure in the helium tank in response to the atmospheric pressure
Implementation Method 3
a control valve for adjusting the outflow of helium gas from the helium tank
Data Source
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AI summary
A device (1) for regulating the pressure in a helium tank (2) of an NMR magnet (23), comprising – a first pressure sensor (6) for measuring a first pressure in the helium tank (2), – a control valve (5) for adjusting a draining helium gas stream from the helium tank (2), – an electronic closed-loop control device (13) for driving the control valve (5), the electronic closed-loop control device (13) being configured – to obtain measured first pressure values D1 from the first pressure sensor (6), – and to adjust a position of the control valve (5) on the basis of the measured first pressure values D1, the first pressure values D1 being brought to a predefined setpoint value SW, wherein the device (1) additionally comprises – at least a second pressure sensor (7; 7a) for measuring a second pressure outside the helium tank (2), wherein the electronic closed-loop control device (13) is additionally configured – to obtain measured second pressure values D2 from the second pressure sensor (7; 7a), – and to determine the setpoint value SW on the basis of the second pressure values D2, and wherein the closed-loop control device (13) is configured to gradually change the setpoint value SW for the pressure in the helium tank (2) as soon as a difference DIF=D1-D2 between the measured first pressure value D1 and the measured second pressure value D2 reaches or exceeds predefined threshold values. The device improves the availability of the NMR magnet.