TBM Gas Detection Metering Module
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Solution Overview
Problem
Tunnel boring machines face challenges in accurately detecting critical gases, such as methane, under high pressure and fluctuating conditions on the rear side of a cutting wheel, which can lead to unreliable alarm systems during harsh and variable operating conditions.
Innovation Solution
The implementation of a metering module with a pressure reducer and flow control valve, combined with a double diaphragm pump, allows for controlled pressure reduction and precise flow rate adjustment of separated gases delivered to a gas analysis unit, ensuring accurate detection of critical gases even under pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas separation is performed under high pressure conditions in the mining chamber, then gas detection can be performed in situ, but the detection accuracy deteriorates due to pressure fluctuations and variable operating conditions
Solution Approach 1:
The system divides the detection process into two independent segments: a separation module that handles high-pressure gas-liquid separation in the mining chamber, and a detection module that operates at stable atmospheric pressure. This segmentation allows each module to be optimized for its specific operating conditions, with the separation module tolerating pressure fluctuations and the detection module maintaining measurement precision.
Solution Approach 2:
The patent introduces an intermediary system consisting of extraction lines and pressure regulation mechanisms that connect the high-pressure mining chamber to the atmospheric-pressure detection environment. This intermediary buffer zone allows gas to be transported from the harsh high-pressure environment to the stable detection environment, isolating the sensitive detection equipment from pressure fluctuations.
2Adaptability or versatility
If extraction lines are extended into the high pressure zone for in-situ detection, then detection coverage is improved, but system complexity increases
Solution Approach 1:
The extraction lines serve multiple functions: they act as both material transport conduits for removing mined material and as gas sampling lines for detecting critical gases. This multi-functionality reduces the need for separate dedicated gas sampling systems, thereby reducing overall system complexity while maintaining comprehensive detection coverage.
Solution Approach 2:
The system utilizes the existing pressure differential and flow dynamics of the mining chamber environment to automatically draw gas samples through the extraction lines. The gas flow is driven by the pressure difference between the high-pressure mining chamber and the lower-pressure detection environment, eliminating the need for additional active pumping or complex control mechanisms.
3Speed
If gas flow rate is increased to improve detection speed, then response time is reduced, but detection accuracy decreases due to insufficient separation
Solution Approach 1:
The system dynamically adjusts the flow rate parameter based on operating conditions. During normal operation, a higher flow rate enables rapid detection response. When pressure fluctuations increase or separation efficiency decreases, the system automatically reduces the flow rate to allow sufficient time for complete gas-liquid separation, thereby maintaining measurement accuracy across varying operational states.
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
This configuration enables reliable detection of critical gases, such as methane, with sufficient accuracy for safety alarms, maintaining precision and reliability under harsh and variable operating conditions.
Implementation Method 1
the metering module has a pressure reducer and a flow control valve downstream of the pressure reducer, high pressures can be reduced in a controlled manner
Implementation Method 2
downstream of the pressure reducer, a double diaphragm pump is provided... the flow rate of separated gas... can be set and maintained with sufficient accuracy
Data Source
AI summary
A device for detecting a content of critical gas in a mining chamber of a tunnel boring machine includes a separation module by which a fluid fed in via an extraction line connection is cleaned of solid and liquid components. A gas line arrangement arranged downstream of the separation module in the flow direction of the fluid carries the fluid, including substantially only gaseous components, through a pressure reducer and through a flow control valve of a metering module by which the gas to be analyzed can be delivered in a controlled manner assisted by a double diaphragm pump and a pressure stabilizer to a gas analysis unit even at high pressures in the cavity.