Patent Publication Number: US-2023140625-A1

Title: Tunnel boring machine having a device for detecting a content of critical gas

Description:
The invention relates to a tunnel boring machine according to the preamble of claim  1 . 
     Such a tunnel boring machine is known from JP 2678563 B2. The generic tunnel boring machine is provided with a device having an extraction line, which is fluidically connected to a cavity arranged on the rear side of a cutting wheel. On the side opposite the cavity, the extraction line is connected to a separation module, through which a gas to be detected is separable from a fluid. The separated gas can be fed into a gas analysis unit, which is arranged downstream of the separation module, and through which warning messages, such as an alarm in the case of critical gas conditions, can be activated. 
     A further tunnel boring machine having a device for detecting a content of critical gas is known from JP2004-300721A. This previously known device has a separation module for separating the gas to be detected from a fluid taken from a discharge unit and a metering module arranged downstream of the separation module for controlled charging of a gas analysis unit with separated gas. In the previously known device, the gas to be detected is separated by changing the pressure conditions in a gas-liquid mixture with solid components. In order to detect a content of critical, in particular explosive, gas such as methane, a portion of the gas that has escaped from this mixture is transferred to a gas analysis unit. 
     Devices for analyzing a gas extracted from a fluid originating from a borehole are known from US 2018/0171786 A1 and WO 2019/143362 A1, wherein in this case a separation module for separating the gas to be detected from the fluid and a metering module downstream of the separation module for controlled feeding of sepatated gas to a gas analysis unit, a pressure reducer and a flow control valve are present. 
     The object of the invention is to specify a tunnel boring machine of the above-mentioned type, which is characterized by detecting a content of critical gas in a cavity subject to relatively high pressure, but possibly also to pressure fluctuations, such as in case of strong pressure drops, and which is arranged on the rear side of a cutting wheel with an accuracy sufficient at least for a danger alarm, even under harsh, possibly rapidly and strongly variable operating conditions. 
     This object is achieved in a tunnel boring machine of the type mentioned with the characterizing features of claim  1 . 
     Due to the fact that in the tunnel boring machine according to the invention the metering module has a pressure reducer and a flow control valve downstream of the pressure reducer, and that a double diaphragm pump is provided downstream of the pressure reducer, high pressures can be reduced in a controlled manner but also the flow rate of separated gas, which is important for a sufficiently reliable detection of a content of a critical gas, and which is delivered to a gas analysis unit, can be set and maintained with sufficient accuracy in case of a pressure drop. 
     Further advantageous developments of the invention are the subject matter of the dependent claims. 
    
    
     
       Further expedient developments and advantages of the invention result from the following description of exemplary embodiments of the invention with reference to the figures of the drawing. 
       In particular: 
         FIG.  1    shows a highly schematic side view of an exemplary embodiment of a tunnel boring machine according to the invention with an embodiment of a device according to the invention, 
         FIG.  2    shows a perspective view of the exemplary embodiment of a device according to the invention shown in  FIG.  1    with a view of a front side accessible to an operator during operation and a gas analysis unit, 
         FIG.  3    shows a perspective view of the exemplary embodiment according to  FIG.  2    with a view of the rear side facing away from the front side and 
         FIG.  4    shows a perspective view of another exemplary embodiment of a device according to the invention with a view of a rear side corresponding to the illustration in  FIG.  3   . 
     
    
    
       FIG.  1    shows an exemplary embodiment of a tunnel boring machine  103  according to the invention in a highly schematic side view. The tunnel boring machine  103  has a cutting wheel  106  on a front end in the advancing direction, which wheel can be rotated by means of a drive unit  109  and which is equipped with mining tools  115  adapted to the prevailing geology for excavating material on a working face  112 . 
     On the side of the cutting wheel  106  facing away from the working face  112 , there is a mining chamber  118  formed as a hollow space, which can be under a pressure of several 1,000 hectopascals (hPa), particularly in the case of a mining method working with pressure assistance. Material which is mined by the working face  112  and which has been conveyed into the mining chamber  118  can be removed via a removal unit  121  which is equipped, for example, with a screw conveyor. 
     In the exemplary embodiment according to the invention, an extraction line  124  opens at one end into the mining chamber  118 , which is sealed against a passage for the extraction line  124 , in its upper region, which is predominantly free of liquid and solids. The extraction line  124  is connected to a fluid processing unit  127  at its end remote from the mining chamber  118 . The fluid present in the extraction area in the mining chamber  118 , which due to the harsh mining conditions also contains liquid and solid components in addition to gaseous components, can thus be fed to the fluid processing unit  127  with the extraction line  124 . The fluid processing unit  127  is connected to a gas analysis unit  133  via a measurement gas transfer line  130 . Both the fluid processing unit  127  and the gas analysis unit  133  are connected to a discharge line  136 , with which the individual components of the fluid extracted from the mining chamber  118  via the extraction line  124  can be discharged from a tunnel space  139  located at the rear of the working face  112 . 
       FIG.  2    shows a perspective view on the front side accessible to an operator during normal operation, of the structure of the fluid processing unit  127  of an exemplary embodiment of a device according to the invention, which is typically used in a tunnel boring machine  103 , which is explained by way of example with reference to  FIG.  1   . The fluid processing unit  127  according to  FIG.  2    is configured on the inlet side with an extraction line connection  203 , to which the extraction line  124  explained in  FIG.  1    but not shown in  FIG.  2    for clarity can be connected in a pressure-tight manner. The extraction line connection  203  communicates with an inlet portion of a fluid mixture line assembly  206 , which is in turn connected to an air connection  209 , a test gas connection  212 , a service connection  215 , and a water connection  218 . The water connection  218  is connected to a water line arrangement  221 , with which water can be supplied to the fluid mixture line arrangement  206  as required. 
     A separation module  224  with two series-connected separators  227 ,  230  in the exemplary embodiment is integrated in the fluid mixture line arrangement  206  downstream of the extraction line connection  203  and the further connections  209 ,  212 ,  215 ,  218  in the direction of flow of a fluid fed in via the extraction line connection  203 . With the separators  227 ,  230 , which are expediently set up for successive coarse and subsequent fine separation and which work by gravity, solid components such as smaller stones, sand and/or mud material and liquid components can be removed from the fluid originating from the mining chamber  118 , so that in the direction of flow of the fluid, on the outlet side of the separation module  224 , essentially only gaseous components are contained. The separators  227 ,  230  are connected in the bottom area to a discharge line arrangement  233 , with which, as shown in  FIG.  2   , the liquid and solid material formed in the separators  227 ,  230  can be discharged, advantageously in a controlled manner by means of check valves. 
     After passing through the separation module  224  with an essentially complete separation of the solid and liquid components, the fluid then consisting essentially only of gaseous components enters a gas line arrangement  236  in which a pressure reducer  239  of a metering module  240  is integrated. By means of the pressure reducer  239 , the inlet pressure in the gas line arrangement  236  can be reduced to an outlet pressure of typically around 1,000 hPa to around 2,000 hPa with a corresponding reduction in volumetric flow. In the gas line arrangement  236  there is also provided an integrated double diaphragm pump  245 , which is resistant to abrasive components in the fluid such as grains of sand, which is connected to a first throttle valve  241  and to a second throttle valve  242  and which can be controlled by means of a solenoid control switch  243  operating with pressurized control air from a control air line  244 , with which the pressure of the fluid in the direction of flow after the double diaphragm pump  245  can be increased to a certain overpressure if required. 
     The double diaphragm pump  245  has two diaphragms that are forcibly coupled to one another, which are supplied via the control air line  244  by the magnetic control switch  243 , which is designed as a 3/2 control valve, for example, via a pulse-like voltage provided by a voltage pulse generator, not shown in  FIG.  2   , wherein the magnetic control switch  243  is activated above a certain voltage signal level, and which can be actuated alternately with the pressurized control air via a return spring after the voltage has dropped below the voltage signal level in such a way that a sufficiently high stroke capacity is provided at a sufficiently high clock frequency and an adjusted pressure in the control air line  244 . As a result, less time is allocated on average to the low-pressure or low-volumetric flow range of the diaphragm after reaching the stroke end position and for resetting. 
     To smooth out remaining pressure fluctuations, particularly under atmospheric conditions in the mining chamber  118 , i.e. without self-delivery of the fluid, the opening degrees of the throttle valves  241 ,  242  are set to a relatively small value, so that the used air escaping for relieving the diaphragm only escapes into the environment with a great deal of delay. As a result, if each diaphragm is reset before the initial position is reached, it transitions again to the next stroke and the opposite diaphragm has meanwhile taken over the lifting work essentially seamlessly. 
     In the flow direction of the fluid downstream of the double diaphragm pump  245 , a pressure stabilizer  248  in the form of an expansion tank with a diaphragm for stabilizing the pressure in the gas line arrangement  236  and then a flow control valve  251  of the metering module  240  are integrated into the gas line arrangement  236 , which is expediently formed as a needle valve for a fine adjustment of flow rate. In the flow direction of the fluid downstream of the flow control valve  251  there is a Y-junction  254 , which subdivides the gas line arrangement  236  into a main arm  257  with a relatively large flow rate and in a secondary arm  260  with a lower flow rate compared to the flow rate in the main arm  257 . 
     Arranging the flow control valve  251  upstream of the Y-junction  254  in the flow direction of the gaseous fluid has the advantage that the entire volumetric flow in the gas line arrangement  236  can be influenced in a targeted manner, taking into account the fluid-dynamic properties of downstream components in the flow direction of the fluid. If, for example, the drain line  136  is relatively long for operational reasons, this results in further pressure losses, which are associated with a corresponding reduction in the volumetric flow. In this case, the entire volumetric flow can be pre-metered to a value suitable for a relatively precise measurement by the gas analysis unit  133  with the aid of the flow control valve  251 . 
     A volumetric flow measuring module  266  is integrated in the main arm  257  in the flow direction of the fluid downstream of a passive check valve  263  provided for safety reasons, with which the volumetric flow of gaseous fluid flowing through the main arm  257 , which is in a fixed ratio to the volumetric flow flowing in the secondary arm  260 , can be measured. The discharge line  136  of  FIG.  1    is connected on the outlet side of the volumetric flow measurement module  266 . 
     In turn, a secondary arm filter module  269  with two secondary arm filters  272 ,  275 , which are connected in parallel for redundancy reasons, is integrated into the secondary arm  260  in order to remove residual contamination from the fluid flowing through the secondary arm  260  of the gas line arrangement  236  before it enters the sample gas transfer line  130  in order to avoid damage to the usually relatively sensitive gas analysis unit  133 . 
     The gas analysis unit  133  can thus be used to feed in gaseous, cleaned fluid, which is only subject to relatively small pressure fluctuations, with a relatively constant volumetric flow. With the gas analysis unit  133 , the gaseous components in the composition of the gaseous fluid can be detected with regard to critical, in particular explosive, gases such as methane. For this purpose, the gas analysis unit  133  expediently has a very precise volumetric flow meter with a quantity adjustment wheel coupled thereto for very precise metering of the gaseous fluid supplied to a gas sensor of the gas analysis unit  133 . 
     The connections  203 ,  209 ,  212 ,  215 ,  218 , which are accessible to an operator from the front during normal operation, can each be closed and opened via a stopcock. As a result, particularly when the extraction line connection  203  is closed, pressurized air can be fed through the air connection  209  and water can be fed through the water connection  218  with the connected water line arrangement  221  for rinsing in particular the fluid mixture line arrangement  206  with flow in both directions. When the corresponding stopcock is opened and the other stopcocks are closed, a test gas can be passed through the test gas connection  212  to check the functionality of the fluid processing unit  127  and in particular the gas analysis unit  133 . 
       FIG.  3    shows a perspective view of the exemplary embodiment of a fluid processing unit  127  according to  FIG.  2    with a view of the rear side facing away from the front side. The part of the gas line arrangement  236  with the components integrated into it that is not visible in the representation according to  FIG.  2    can be seen in  FIG.  3   . In particular, it can be seen from the illustration according to  FIG.  3    that the gas line arrangement  236  is equipped with a shut-off valve  303 , with which, in the front area in the direction of flow of the gaseous fluid flowing in the gas line arrangement  236 , for example in cases such as a critical fill level in the separation module  224 , a blocking of the rear region in the flow direction can take place. Furthermore, the arrangement of the Y-junction  254  in the form of a T-piece with the neck of the T on the inlet side of the secondary arm  260  can be clearly seen from the representation according to  FIG.  3   . Moreover, it can be seen from  FIG.  3    that the separators  227 ,  230  are each provided with a filling level sensor  306 , by means of which a warning signal can be generated to the effect that the contents of the separators  227 ,  230  can be discharged by an operator via the discharge line arrangement  233  at a maximum filling level. 
       FIG.  4    shows a perspective view of a further exemplary embodiment of a fluid processing unit  127  with a view of a front side accessible to an operator during operation, corresponding to the illustration according to  FIG.  2   , wherein in the exemplary embodiment of a fluid processing unit  127  explained with reference to  FIGS.  2  and  3   , and in the exemplary embodiment of a fluid processing unit  127  of  FIG.  4   , corresponding components are provided with the same reference symbols and are not explained in more detail below to avoid repetition. 
     The exemplary embodiment according to  FIG.  4    differs from the exemplary embodiment according to  FIG.  2    and  FIG.  3    essentially in the fact that the flow control valve  251  is integrated in the main arm  257  upstream of the volumetric flow measurement module  266  with a main flow filter module  403 , which is arranged upstream for protection in particular in case of a low-lying arrangement in the lower region of the fluid processing unit  127 . A check valve  263  is not provided in the embodiment according to  FIG.  4   . The exemplary embodiment of a fluid processing unit  127  according to  FIG.  4    is characterized in that by setting the flow rate in the main arm  257 , the flow rate in the secondary arm  260  can be adjusted with a relatively high accuracy, which increases the measurement precision of the gas analysis unit  133 . 
     The exemplary embodiment of  FIG.  2    and  FIG.  3    and the exemplary embodiment of  FIG.  4    have in common that the pressure adjustment, pressure stabilization and flow rate adjustment for proper operation of the gas analysis unit  133  occur via the sequence in the flow direction of the fluid formed by the pressure reducer  239 , the double diaphragm pump  245 , the pressure stabilizer  248  and the flow control valve  251  with subsequent division at the Y-junction  254  into a main arm  257  with a larger flow rate and in a secondary arm  260  with a lower flow rate in the direction of the gas analysis unit  133 . As a result, the content of critical gas in the gaseous fluid can be determined largely without delay, even under strongly changing ambient conditions in the mining chamber  118 , at least so precisely that, for example, the presence of explosive methane in a safety-relevant concentration can be detected reliably and relatively quickly.