Field of the Invention

[0001 ] This invention relates generally to underground mining safety monitoring equipment and, more particularly, this invention relates to a coal seam strata resin injection hole temperature monitoring system.

Background of the Invention

[0002] In underground coal mining, when the ground above the working seam is considerably fractured and/or unstable, it is common to “glue” the ground together by injecting Polyurethane resin or similar products that go through an exothermic reaction process during the curing cycle into the strata above by drilling a hole 6-25m long (depending on conditions) and then pumping the hole full of resin which works its way into the fractures.

[0003] Some curing time is required, and during this curing process the resin temperature can reach 150°C or more.

[0004] However, if mining activities recommence to soon, there is a risk of warm or hot resin and coal ending up in the goaf (the cavity left behind as the longwall retreats and into which the above ground falls into).

[0005] This is a very undesirable situation as a heating in the goaf often leads to fire or explosion due to ignition of coal or flammable gases (CH ₄ ).

[0006] Due to this risk, the current control is a “fire watch” whereby time is allowed for the resin to cool after injection before mining re-commences.

[0007] Current measuring of temperature consists of looking for signs of smoke, and/or pointing a thermal camera at the roof and trying to detect any warmth, which is obviously not accurate.

[0008] The present invention seeks to provide a way, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative. [0009] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Disclosure

[0010] According to one aspect, there is provided a coal seam strata resin injection hole temperature monitoring system and method for a resin injection hole formed in coal seam strata.

[001 1 ] The system comprises a temperature sensing injector lance comprising a dowel string defining a lumen therethrough, the lumen defining an injection outlet at a distal end thereof and a proximal inlet. The lance further comprises a flexible temperature sensing cable arranged along an exterior surface of the dowel string. The temperature sensing cable comprises a plurality of temperature sensing transducers along the length thereof.

[0012] A control unit is electrically connected to the temperature sensing cable via a length of interfacing cable.

[0013] The method comprises inserting the dowel string with the flexible temperature sensing cable therealong into the resin injection hole into position and injecting exothermically curing resin into the inlet of the dowel string so that the resin fills the hole from the distal end of the dowel string and envelops the temperature sensing cable so that the temperature sensing transducers thereof are able to measure the temperature of surrounding resin during curing .

[0014] The control unit is electrically connected to the temperature sensing cable via the interfacing cable located a safe distance away from the lance.

[0015] The method comprises monitoring temperature sensor readings of the temperature sensors of the temperature sensing cable embedded in the resin using the control box during curing of the resin .

[0016] After curing, the dowel string and temperature sensing cable are left embedded in the resin.

[0017] Other aspects of the invention are also disclosed. Brief Description of the Drawings

[0018] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0019] Figure 1 shows a coal seam strata resin injection hole temperature monitoring system in accordance with an embodiment;

[0020] Figures 2 - 4 illustrate a coal seam strata resin injection hole temperature monitoring method in accordance with an embodiment;

[0021 ] Figure 5 shows electrical wiring of an analogue-type system in accordance with an embodiment;

[0022] Figure 6 shows an analogue-type control unit in accordance with an embodiment;

[0023] Figure 7 shows a protective nose cone in an embodiment;

[0024] Figure 8 shows a digital control unit in accordance with an embodiment

[0025] Figure 9 shows an electrical schematic of the digital control unit in accordance with an embodiment;

[0026] Figure 10 - 14 show exemplary graphical user interfaces of the digital control unit;

[0027] Figure 15 shows a schematic of the digital control unit in accordance with an embodiment; and

[0028] Figure 16 shows a temperature conversion barrier arrangement of the digital control unit in accordance with an embodiment.

Description of Embodiments

[0029] Figure 1 shows a coal seam strata resin injection hole temperature monitoring system 100.

[0030] A resin injection hole 101 is formed through a coal seam 102 and further into adjacent rock strata 103. Typically, the hole 101 is drilled to between 4 - 25 m into the strata 103 above the working seam 102 or into the “ribs” or coal walls adjacent to the extracted seam 102. [0031 ] The system 100 comprises a temperature sensing injector lance 104 which comprises a hollow dowel string 105 having a lumen therethrough for injection of exothermically curing resin into the hole 101. The dowel string 105 may be formed by a plurality of fibreglass tubes which are joined together using joints to form the dowel string 105 of a length suited for the hole 101 .

[0032] The lumen defines an injection outlet 106 at a distal end of the dowel string 105 and a proximal inlet.

[0033] The lance 104 further comprises a flexible temperature sensing cable 107 arranged along an exterior surface of the dowel string 105.

[0034] The temperature sensing cable 107 comprises a plurality of temperature sensing transducers 108 along the length thereof. The temperature sensing transducers 108 may be semiconductor-based electro resistive transducers which convert temperature to resistance. For example, the temperature sensing reading transducer may be a K-type thermocouple. In one embodiment, the temperature sensing transducer 108 may be the PtI OOO sensor.

[0035] The temperature sensing transducers 108 are arranged along the length of the temperature sensing cable 107 so that the temperature sensing transducers 108 lie along the dowel string 105 and across an exterior surface thereof so as to be able to measure the temperature of resin injected by the dowel string 105 and surrounding the dowel string 105 within the hole 101 .

[0036] The system 100 further comprises a control unit 109 electrically connected to the temperature sensing cable 107 via a length of interfacing cable 1 10.

[0037] The length of the interfacing cable 110 may allow safe distancing of the control unit 109 from the lance 104. Figure 1 generally shows a safe area 11 1 and a hazardous area 1 12. In embodiments, the interfacing cable 1 10 may be quite long, such as up to 4000 m or more in embodiments. As will be described in further detail below, in embodiments, the control unit 109 may be configured to account for electrical resistance of the interfacing cable 1 10 for so that the readings from the temperature sensing transducers 108 remain accurate irrespective of the length of the interfacing cable 1 10. [0038] The interfacing cable 1 10 may be electrically disconnected from the temperature sensing cable 107 at a cable joint 1 13 which, as shown in Figure 1 may be near the opening of the hole 101 .

[0039] The lance 104 may further comprise an inflatable packer 1 14 which is inflated to seal the distal end of the lance 104 within the hole 101 for injection of resin.

[0040] The lance 104 may further comprise resin injection tubes 1 16 fluidly connected to the lumen through the dowel string 105. The tubes 1 16 may be used to separately inject resin components which mix together within the lumen of the dowel string 105. In use, resin is injected through the injection tubes 1 16 to flow through the lumen of the dowel string 105 and from the distal outlet 106 thereof.

[0041 ] The packer 1 14 may be disconnected from the resin injection tubes 1 16 by cutting the resin injection tubes 1 16 once pumping has ceased. 1 15. In use, the dowel string 105, the packer 1 14, and the temperature sensing cable 107 are left embedded within resin within the hole 101 through the strata 103.

[0042] Figures 2 - 4 illustrate a coal seam strata resin injection hole temperature monitoring method in accordance with an embodiment.

[0043] According to Figure 2, the hole 101 is drilled through the working seam 102 into the strata 103. The lance 104 is prepared wherein the temperature sensing cable 107 is arranged along a length of the dowel string 105 and on an exterior surface thereof so as to be able to monitor the temperature of resin surrounding the dowel string 105 along the length of the dowel string 105.

[0044] The distal end of the lance 104 is inserted into the hole 101 until reaching position as is shown in Figure 3 wherein the distal end of the lance 104 is substantially at the end of the hole 101.

[0045] Figure 3 shows the inflation of the packer 1 14 to seal the distal portion of the lance 104 within the hole 101 . As the temperature sensing cable 107 is flexible, it is able to flex with the expansion of the packer 1 14. Preferably the temperature sensing cable 107 is a flat ribbon type cable able to withstand compression of the packer 1 14. [0046] Similarly, the flexible temperature sensing cable 107 is able to bend around connection joints of the tubular components forming the dowel string 105. [0047] Resin component reservoirs and associated pumps are attached to the resin injection tubes 1 16 and resin from the reservoirs injected through the tubes 1 16, through the inlet of the dowel string 105, through the lumen thereof and from the outlet 106 thereof so that the resin 1 17 begins to fill the hole 101 from the distal end of the dowel string 105 as is shown in Figure 3.

[0048] Figure 4 shows wherein the hole 101 is substantially entirely filled with the resin 1 17 and the temperature sensing cable 107 is enveloped by the resin 1 17. As such, the temperature sensing transducers 108 are able to measure the internal temperature of surrounding resin 1 17 during curing at sampling points along the length of the dowel string 105.

[0049] Exothermically curing of the resin 1 17 may cause the resin 1 17 to reach temperatures in excess of 150°C. As such, the temperature sensing cable 107 is preferably rated to 200°C or more. In this regard, the temperature sensing cable 1 17 may have a silicon sheath rated to 200°C or more.

[0050] As alluded to above, the temperature sensing cable 107 is preferably flat so as to withstand compression from the packer 1 14. Furthermore, cores of the temperature sensing cable 107 preferably comprises a core for each transducer 108 and a shared common ground 145 as is illustrated in Figure 5.

[0051 ] The sharing of the common ground, allows the reduction of the number of cores within the cable 107, thereby reducing the thickness thereof and to allow the cable 107 to be flat to withstand compression of the packer 107.

[0052] For example, where the temperature sensor cable 107 comprises three transducers 108, the temperature sensing cable 107 may comprise four cores, three cores for each transducer 108 and a further call for a common ground.

[0053] In an embodiment, the temperature sensing cable 107 is a 4-core silicone sheathed ribbon cable that is rated for 200°C and can withstand the pressure of the packer 1 14 when the packer 1 14 is expanded. Preferably, the cable joint 1 13 uses IP67 rated plugs.

[0054] The temperature sensing cable 107 may be 15m in length consisting of 1 1 m of silicone sheathed ribbon cable (which is installed in the hole 101 alongside the dowel string 105) and 4m of round CAT5 cable that extends from the hole 101 beyond the packer 1 14.

[0055] Preferably, the round CAT5 cable does not pass the packer 1 14 as it may not withstand the pressure exerted thereby. Furthermore, CAT5 cable may not be temperature rated for the exothermically curing temperatures. The round CAT5 cable has may have an IP67 rated RJ45 plug fitted to the end which connects into the interfacing cable 1 10.

[0056] The 11 m of silicone sheathed ribbon cable may houses three PtI OOO temperature sensors 108. The temperature sensors 108 may have a temperature sensor at a distal end of the cable 107, a further temperature sensor transducer 108 spaced 2 m back therefrom and a further temperature sensor transducer 108 further spaced 2m back from the middle sensor transducer 108.

[0057] As is illustrated in Figure 9, the interfacing cable 110 may use three cores per sensor transducer 108, so the resistance of the interfacing cable 110 can be measured by the temperature conversion barriers 139 as will be described in further detail below. In other words, any additional resistance introduced from the interfacing cable 1 10 may be automatically deducted from readings by the barriers 139, meaning that any length of interfacing cable 110 can be added without affecting the temperature sensor readings of the control unit 109.

[0058] The control unit 109 may be used to measure the internal temperature of the resin 117 as it cures from a safe distance away from the lance 104. Generally, the temperature will rise as the curing process commences, reach a peak, and then decrease to safe levels again whereafter mining process may recommence.

[0059] As alluded to above, the dowel string 105 and the temperature sensing cable 107 may be sacrificed by being left embedded in the cured resin 1 17.

[0060] Figure 7 shows a protective nose cone 122 which is attached to a distal end of the dowel string 105 in an embodiment, and which may be used to protect the temperature sensing cable 107.

[0061 ] The nosecone 122 may comprise a conical distal end defining the outlet 106 therethrough. In the embodiment shown, the outlet is formed by a primary central outlet 106A and a plurality of secondary periphery outlets 106B to reduce likelihood of blockage when injecting the resin 1 17. In embodiments, the primary and secondary outlets interface respective lumens through the dowel string 105 and are used to inject components of the resin so that the components do not mix within the dowel string 105.

[0062] As is evident from Figure 7, the temperature sensor cable 107 follows behind the nosecone 122 within the peripheral circumference of the nosecone 122 so that the temperature sensing cable 107 is protected behind the nosecone 122.

[0063] The nosecone 122 may comprise a cleat 108 which engages a distal end of the temperature sensor cable 107. In the embodiment shown, distal end of the temperature sensing cable 107 is wrapped around a cleat 108. The cleat 108 may be further recessed within the exterior surface of the nosecone 122 so as to not cause obstruction when inserting the lance 104.

[0064] Figure 6 shows an analogue type control unit 109 which exposes a pair of multimeter plug ports 1 18 to which plugs 1 19 of a hazardous area certified multimeter (such as the Fluke™ 28II LS. multimeters) can be attached. According to this embodiment, the control unit 109 further comprises a selector switch 120 (taking the form of a rotary selector switch in the embodiment shown) which connects a respective temperature sensor transducer 1 08 between the ports 1 18 depending on the rotary position of the selector switch 120.

[0065] According to this embodiment, the control unit 109 entirely comprises passive circuitry and is therefore certified for use in hazardous areas 1 12. Furthermore, a hazardous area certified multimeter can be plugged into the available ports 1 18 thereof and the selector switch 120 configured to read the resistance readings from each temperature sensor transducer 108. A conversion table may be provided to convert the resistive readings displayed by the multimeter to temperature.

[0066] Figure 5 shows an electrical schematic of the analogue type control unit 109 wherein it is shown that the selector switch 120 is able to independently address each temperature sensor transducer 108. [0067] The analogue type control unit 109 may comprise an RJ 45 connector 121 for a CAT5 interfacing cable 110.

[0068] Figure 8 shows an active electronic digital control unit 109 in accordance with a further embodiment. As is shown in Figure 8, the digital control unit 109 may be protectively housed within a ruggedised case 123 and which may comprise a touchscreen digital display 124. The case 123 may have a side port 1 25 for the interfacing cable 1 10.

[0069] Figure 15 shows a schematic of the digital control unit 109 in accordance with an embodiment wherein the control unit 109 comprises a processor 126 for processing digital data. The control unit 109 may further comprise a memory device 127 in operable communication with the processor 126 via system bus 128. The memory device 127 is configured for storing digital data including computer program code instructions.

[0070] In use, the processor 126 is configured for fetching, decoding and executing these computer program code instructions and associated data for implementing the control functionality described herein.

[0071 ] The data 129 stored by the memory 127 may comprise operational settings 130 for controlling the operation of the control unit 109. As will be described in further detail below, the settings 130 may relate to a hole number setting and interfacing cable 1 10 configuration settings.

[0072] The data 129 may further store temperature logs 131 which may be subsequently downloaded from the control unit 109.

[0073] The computer program code instructions may be logically divided into a plurality of computer program code instruction controllers 132.

[0074] In embodiments, the controllers 132 may comprise an addressing controller 133 which addresses each temperature sensor transducer 108 and an associated reading controller 134 which obtains a temperature sensor reading therefrom. The addressing controller 133 may be configured for configuring the temperature conversion barriers 138 to deduct resistance introduced by the interfacing cable 110. [0075] The controllers 132 may further comprise a logging controller 135 which updates the logs 131 with temperature readings.

[0076] The controllers 132 may further comprise a user interface controller 136 which displays a user interface 137 on the digital display 124.

[0077] The control unit 109 may further comprise analogue to digital converters 137 for each temperature sensor transducer 108. The converters 137 may convert 4 - 20 mA current loop signals to a digital representation.

[0078] For use within hazardous areas, the converters 137 may interface each temperature sensor transducer 108 via a temperature conversion barrier 138.

[0079] Figure 16 shows an exemplary temperature conversion barrier 138 arrangement interfacing temperature sensor transducers 108 installed within the hazardous area 1 12. The temperature conversion barrier 138 may be the MLT5576- RTD temperature conversion barrier in accordance an embodiment.

[0080] In this regard, Figure 9 shows an arrangement wherein the temperature sensor cable 107 comprises three temperature sensing transducers 108 and a pair of temperature conversion barriers 138 are used to interface the temperature sensing transducers 108.

[0081 ] Each temperature conversion barrier 138 may comprise a pair of resistive sensing inputs 139 and a corresponding isolated 4 - 20 mA output 140.

[0082] In the embodiment shown, the control unit 109 may comprise a first temperature conversion barrier 138A interfacing one of the temperature sensor transducers 108 and a second temperature conversion barrier 138B interfacing the other two transducers 108.

[0083] Each temperature conversion barrier 138 may further comprise a configuration input 141 .

[0084] As alluded to above, each temperature conversion barrier 138 may be configured to account for increased resistance depending on the length/and or configuration of interfacing cable 1 10.

[0085] For example, the configuration settings 130 may be configured to indicate that 1000 m of interfacing cable 1 10 has been installed. As such, the processor 126 calculates the associated electrical resistance induced thereby and then controls the temperature conversion barriers 138 via the configuration inputs 141 so that the temperature conversion barriers 138 automatically deduct the additional resistance introduced by the interfacing cable 110. As such, the 4 - 20 mA signal from the output 140 is the same irrespective of the installed length of interfacing cable 110.

[0086] Figures 10 - 14 show exemplary graphical user interfaces 137 displayed by the digital control unit 109.

[0087] Figure 10 shows an initial configuration screen, inviting an operator to connect the interfacing cable 110. The processor 126 may monitor the outputs 140 of the temperature conversion barriers 138 to detect whether an interfacing cable 1 10 and associated temperature sensing cable 107 have been connected to the control unit 109. The interface of Figure 10 may display a battery level indication 142.

[0088] Once the interfacing cable 1 10 and temperature sensing cable 107 have been connected to the control unit 108, the interface 137 shown in Figure 11 may be displayed. The interface 137 may comprise live temperature sensor readings 143 of each temperature sensor transducer 108 and have a keypad 144 used for inputting a hole number, in this case, hole number 568.

[0089] Once the hole number has been configured, the user interface 137 of Figure 12 may be displayed wherein the interface 137 comprises real-time temperature sensing readings 146. The temperature sensing readings 146 may be colour-coded read, amber and green to indicate safety levels according to temperature reading.

[0090] The interface 137 may be operable to show a trend 147 shown in Figure 13 wherein temperature sensing trends for each temperature sensor transducer 108 are shown averaged across 0-, 2- and 4-minute intervals. Figure 13 indicates the aforedescribed typical rise and fall in temperature as the exothermically curing process commences and completes and which may be indicative to an operator of the proper functioning of the system 100.

[0091 ] Peak temperature readings may be displayed in the interface 137 shown in Figure 14. [0092] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practise the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed as obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.