WO2018186792A1

WO2018186792A1 - Method and system for transporting rock material

Info

Publication number: WO2018186792A1
Application number: PCT/SE2018/050350
Authority: WO
Inventors: Thorsten MICHELFELDER; Jonas KÖHLSTRÖM; Sverker Hartwig; Niklas Fors
Original assignee: Epiroc Rock Drills Aktiebolag
Priority date: 2017-04-07
Filing date: 2018-04-04
Publication date: 2018-10-11
Also published as: EP3607174A1

Abstract

A method and system (10) for transporting rock material (20) such as drill muck in a conveying conduit by means of an airflow, the system comprising a conveying conduit (11) having an inlet end (12) for receiving rock material to be transported and an outlet end (13); a suction device (14) for creating an airflow, which suction device is arranged in connection to the outlet end (13) of the conveying conduit (11); and an extraction unit (15) for extracting rock material (20) that has been transported in the conveying conduit (11), the extraction unit being arranged in fluid connection to the outlet end (13). The system further comprises a feed controller (16) for controlling the provision of rock material (20) to the inlet end (12) of the conveying conduit (11), wherein a sensor (17) is arranged to monitor the airflow in the conveying conduit, and that a control unit (18) is arranged to in response to the monitored airflow in the conveying conduit produce a command to control the provision of rock material (20) to the inlet end (12) of the conveying conduit and/or to produce a command to control a suction effect of the suction device.

Description

METHOD AND SYSTEM FOR TRANSPORTING ROCK MATERIAL

TECHNICAL FIELD

[0001] The invention relates to a method and a system for transporting rock material, such as drill muck, segmented rock and soil material or the like, in a conveying conduit by means of a forced airflow. Specifically, the invention relates to such a method and system in an excavating operation.

[0002] The invention is useful for all types of mining or rock excavation machines, including rock drilling machines. A typical implementation is tunnel boring machines where the rock is mechanically excavated using large cutting heads having disc- or roller cutters that are brought against the rock in a rotating manner. Depending on the design of the machine the excavated rock may be brought directly into the conveying conduit of the system or brought into the system from a buffering location, such as a pile of fragmented rock material on the tunnel floor, or from another conveying system. The present method and system for transporting rock material is also useful to transport the rock material from so- called long wall mining machines or different types of rotary cutting machines used for soft rock excavation or coal mining.

BACKGROUND

[0003] In rock excavation operations rock material, typically in the form of drill muck, is produced and needs to be removed from the excavation zone, e.g. a drill hole. This is particularly complex in underground applications in which the rock material needs to be transported up to ground level. Often, the transport is performed in steps, wherein the rock material is firstly transported from the actual drilling location to a charging point from which it is further transported on conveyor belts, wagons, skips or to the like to ground level.

[0004] In many rock drilling applications, the rock material is removed from the drill hole either by means of a water flushing the drill hole and/or an applied over pressure arranged to push the rock material out from the drill hole, and/or by applying a negative pressure so as to suck the rock material from the drill hole. The rock material may either be arranged to pass outside of the drill string or within the drill string.

[0005] US 7,090,018 B2 discloses an apparatus in which a concentric tubing string is utilized to provide a pressurized clean out medium in one of at least two concentric channels by means of a discharge compressor, wherein the produced drill muck and clean out medium is removed through another concentric return channel, preferably by means of a vacuum unit, and specifically a suctioning compressor.

[0006] In WO 2010/093775 A2 is disclosed a tunnelling apparatus in which drilling is performed by a drill head to which drilling fluid and pressurized air is provided, a vacuum source being provided to remove the rock material from the drill hole. The excavation machine may be controlled in response to a measured pressure in the evacuation conduit and/or in response to a measured airflow of the provided pressurized air.

[0007] Both these systems relate to methods of controlling a drilling operation in which the drill hole may be regarded as a closed system, such that the pressurized clean out medium applied by the discharge compressor is not allowed to escape between the tubing string and the inside of the drill hole, wherein all material is pushed in to the return channel.

[0008] In some applications, several drill holes are drilled next to each other, intersecting each other, and in such applications, there will be an opening along at least one side of the whole drill hole such that it will not be possible to force the rock material or drill muck into a conveying line by means of an applied over pressure. Further, in other applications, rock material is moved from one point to another. A lot may be gained if such conveying may be done with a conveying conduit as the use of a conveying conduit implies that it will not be necessary to provide transport tunnels adapted for wheel-loaders or the like.

[0009] A further arrangement for transporting material is known from JP 4-11-303585, in which sludge material is sucked through a tube by means of a vacuum pump. The arrangement comprises a pressure gauge or a flow meter for monitoring the pressure or the flow in the tube, and a control valve is arranged and regulated to govern the air inlet into the tube and thereby the air flow in said tube. This arrangement is advantageous in that it does not require a closed drill hole to function.

[0010] However, the arrangement of JP 4-11-303585 is primarily arranged to suck sludge material or a slurry by allowing it to form plugs or blockings inside the tube. An air- inlet is arranged to control the viscosity of the sludge material in order to improve the transportation thereof. This is a method that works fine with sludge material, but which is not adapted for rock material, where plugs of material should be avoided, because such plugs may require shutting down of the system to be resolved. Namely, it is generally not possible to resolve a plug of rock material by simply increasing the suction force. Instead the block needs to be resolved mechanically, which in most cases means shut down and disassembly of at least the blocked part of the system. [0011] Hence there is a need of a method and a system with an improved transport of rock material in areas of limited access during an excavation operation, such as in mining applications.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a method and a system for transport of rock material, which method and system provides an improved and reliable feeding of rock material, especially in areas of limited access. A further object is related to minimising the risk of the formation of plugs or blockings inside a conveying counduit.

[0013] According to a first aspect the invention relates to a method of transporting rock material such as drill muck in a conveying conduit during an excavation operation of rock material by means of a forced airflow, the method comprising the steps of producing an airflow in a conveying conduit inside which rock material is to be transported by means of a suction device arranged at an outlet end of the conveying conduit; providing rock material to an inlet end of said conveying conduit; and extracting rock material from said conveying conduit at an extraction point between the inlet end and the outlet end. The method includes monitoring an actual parameter representing the airflow in the conveying conduit and to control a set parameter that at least indirectly governs the airflow in the conveying conduit.

[0014] The controlling of a set parameter is based on the monitoring of the actual parameter and is typically made so as to avoid that the airflow reaches below a critical value that has been set to correspond to an undesired risk of formation of plugs inside the conveying conduit.

[0015] The invention is based on the notion that rock material is best conveyed in a conveying conduit by means of a continuous and preferably relatively high air flow. This is in accordance with the invention achieved by monitoring an actual parameter representing the airflow in the conveying conduit. It has not been proven reliable to monitor a pressure, or a negative pressure, because the pressure may vary in response to a wide variety of parameters and is therefore not a reliable source of information for controlling of the airflow in the conveying conduit. Specifically, monitoring of the pressure in the conveying conduit is not reliable as a sole information source for controlling the airflow so as to avoid the formation of plugs or blocks.

[0016] According to a specific embodiment the set parameter that at least indirectly governs the airflow in the conveying conduit is a parameter related to the provision of rock material to said inlet end of the conveying conduit and/or a parameter related to the suction effect of the suction device. Specifically, a command to reduce a rate of provision of rock material to the inlet end of the conveying conduit or a command to increase the suction effect of the suction device is issued in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

[0017] According to a specific embodiment a command to reduce a rate of provision of rock material to the inlet end of the conveying conduit is issued in response to that the monitored actual parameter reaches below a first threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a threshold rate.

[0018] According to a specific embodiment a command to reduce a speed of provision of rock material to the inlet end of the conveying conduit is a command to stop the provision of rock material to the inlet end of the conveying conduit.

[0019] According to a specific embodiment the inlet end of the conveying conduit is connected to an excavation machine having a cutting head arranged to be rotated and driven into a rock and to thereby produce rock material to be transported away in said conveying conduit, and wherein the control unit is configured rate to control of excavation of stone material, e.g. by adjusting the thrust force and/or the speed of advancement and/or the rotational speed of a cutting head to thereby control the provision of rock material to the conduit inlet,

[0020] A command to revise a parameter related to the operation of an excavation machine may be issued in response to that the monitored actual parameter representing the airflow reaches below a first threshold value.

[0021] Specifically, a command to reduce the thrust force acting on the cutting head of the excavation machine is issued in response to that the monitored actual parameter representing the airflow reaches below a first threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a threshold rate. Specifically, the command to reduce the thrust force acting on a cutting head of the excavation machine may be a command to stop advancement of the cutting head.

[0022] According to a specific embodiment the actual parameter representing the airflow in the conveying conduit is continuously categorized in one of at least two airflow ranges, a lower, and a medium airflow range, wherein commands are issued to keep the suction effect of the suction device in the medium airflow range. [0023] According to another specific embodiment the actual parameter representing the airflow in the conveying conduit is continuously categorized in one of at least three airflow ranges, a lower, a medium and a higher airflow range, wherein commands are issued to keep the suction effect of the suction device in the medium airflow range.

[0024] Specifically, a command to reduce a speed of advancement of the cutting head, i.e. to reduce the thrust force acting on said cutting head, is issued when the monitored actual parameter is categorized as pertaining to the lower airflow range.

[0025] According to a specific embodiment the monitoring of a parameter representing the airflow in the conveying conduit is performed at a point downstream of the extraction point.

[0026] According to a specific embodiment, as a first measure in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate, a command to increase the suction effect of the suction device is issued, and wherein, as a second measure in a subsequent step, a command to reduce a speed of provision of rock material to the inlet end of the conveying conduit is issued.

[0027] According to a second aspect the invention relates to a system for transporting rock material such as drill muck in a conveying conduit by means of an airflow, the system comprising:

a conveying conduit having an inlet end for receiving rock material to be transported and an outlet end;

a suction device for creating an airflow, which suction device is arranged in connection to the outlet end of the conveying conduit; and

an extraction unit for extracting rock material that has been transported in the conveying conduit, the extraction unit being arranged in fluid connection to both the inlet end and the outlet end. A sensor is arranged to monitor an actual parameter representing the airflow in the conveying conduit, wherein a control unit is arranged to control a set parameter that at least indirectly governs the airflow in the conveying conduit in response to the monitored actual parameter.

[0028] The monitored actual parameter is typically controlled so as to avoid that the airflow reaches below a critical value that has been set to correspond to an undesired risk of formation of plugs inside the conveying conduit. [0029] According to a specific embodiment, the set parameter that at least indirectly governs the airflow in the conveying conduit is a parameter related to the provision of rock material to said inlet end of the conveying conduit and/or a parameter related to the suctioning effect of the suction device.

[0030] According to a specific embodiment the control unit is configured to issue a command to reduce a rate of provision of rock material to the inlet end of the conveying conduit or a command to increase the suction effect of the suction device in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

[0031] According to a specific embodiment an auxiliary air inlet is arranged

downstream of the inlet of the conveying conduit and upstream of the extraction unit, the auxiliary air inlet being of an ejector type providing an accelerated air flow inside the conveying conduit. Preferably, the conveying conduit has a widened cross-sectional area downstream of the auxiliary air inlet.

[0032] According to a specific embodiment the inlet end of the conveying conduit is connected to an excavation machine having a cutting head arranged to be rotated and driven into a rock and to thereby produce rock material to be transported away in said conveying conduit, and wherein the control unit is configured to control a thrust force of said cutting head.

[0033] In a more general form the control unit is configured to control a rate of excavation of stone material, e.g. by adjusting the thrust force and/or the speed of advancement and/or the rotational speed of a cutting head to thereby control the provision of rock material to the inlet.

[0034] According to a specific embodiment the control unit is configured to issue a command to reduce said thrust force in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

[0035] By means of the inventive system and method, transport of rock material will be made more efficient and stops due to plugs or blockings in the conveying conduit may be minimized and the control of the transport will be improved such that problems related to plugs or blockings of rock material may be avoided. Instead of transporting rock materials in the form of blocks, which may form blockings, inside the conveying conduit the air flow will be controlled so as to assure a continuous airflow and, as a consequence, a continuous airflow driven transportation of rock material through the conduit with a minimized risk of the formation of plugs or blockings.

[0036] This is achieved in that a parameter representing the airflow in the conveying conduit is monitored, and in that a reaction is caused by said monitoring. The monitoring provides a reliable indication of the status of the flow of air and stone material in the conveying conduit, in contrast to a monitoring of other parameters, such as the pressure or negative pressure in the conveying conduit, or the pressure or flow in a conduit providing cleaning fluid or pressurized air to the inlet end of the conveying conduit.

[0037] Hence, the invention provides a novel and reliable manner of controlling the flow of air and ultimately the flow of stone material inside the conveying conduit. With the addition of the step of controlling the provision of rock material to the inlet end of the conveying conduit in response to the monitored actual parameter a continuous flow may be achieved and problems such as blockings and the like may be avoided.

[0038] Other embodiments and advantages will be apparent from the detailed description and the appended drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0039] An exemplary embodiment related to the invention will now be described with reference to the appended drawings, of which:

Fig. 1 is a schematic representation of a system in accordance with the invention for transporting stone material;

Fig. 2 is a specific embodiment of the invention, in which a conveying conduit is connected to a drilling machine;

Fig. 3 is a detailed view of a part of the system shown in fig. 2;

Fig. 4 is a schematic view of an auxiliary air inlet to be used in an embodiment of the inventive system; and

Fig. 5 is a schematic view of a drill rig on which the inventive system may be

implemented. DETAILED DESCRIPTION OF EMBODIMENTS

[0040] Fig. 1 is a schematic representation of a system 10 for transporting rock material 20 such as drill muck in a conveying conduit 11 by means of a forced airflow. The system comprises a conveying conduit 11 having an inlet end 12 arranged at a supply point 21 for receiving rock material 20 to be transported, and an outlet end 13, where a suction device 14 is arranged to suck the rock material 20 through said conveying conduit 11.

[0041] The suction device 14 is arranged to create an airflow and is therefore arranged in connection to the outlet end 13 of the conveying conduit 11. The suction device 14 is preferably a vacuum device that uses an air pump to create partial vacuum and thereby create the suction in the conveying unit 11. The air pump can be of different types such as screw type, fan or blower type, roots type or liquid ring type. The conveying conduit may be comprised of several separate tubular parts of rigid materials such as steel or other metals, or flexible materials such as rubber, with or without reinforcements. Typically, straight metal tubes may be joined to flexible parts of thick and/or reinforced rubber to together form the conveying conduit 11.

[0042] An extraction unit 15 for extracting rock material that is transported in the conveying conduit is arranged along the conveying conduit 11. In connection to the extraction unit 15 a disposal point 22 for disposal of the transported rock material 20 is arranged. The disposal point 22 may either be a point where the rock material will be loaded on to other types of transport units, such as conveyor belts, muck cars or trucks, or a point where the rock material 20 will be recovered for ore extraction or for disposal.

[0043] The system further comprises a feed controller 16 for controlling the provision of rock material to the inlet end 12 of the conveying conduit 11. A sensor 17 is arranged to monitor an actual parameter representing the airflow in the conveying conduit, and a control unit 18 is arranged to control a set parameter that at least indirectly governs the airflow in the conveying conduit in response to said monitored actual parameter, so as to avoid that the airflow reaches below a critical value that has been set to correspond to an undesired risk of formation of plugs inside the conveying conduit. It should be noted that a monitoring of the pressure inside the conveying conduit does not lead to a reliable control of the airflow, because a strongly reduced airflow due to the initiation of the formation of a plug or block will not necessarily show up as a significant pressure drop. Therefore, in line with the invention, a continuous transport of rock material, which is free from plugs, is achieved by the controlling of a parameter that at least indirectly governs the airflow in the conveying conduit in response to the monitored actual parameter [0044] In the shown embodiment the control unit 18 is arranged to produce a command to control the provision of rock material to the inlet end of the conveying conduit in response to the monitored airflow in the conveying conduit. Typically, the control unit 18 provides a command directly to the feed controller 16, or to an operator who is thereby urged or advised to manipulate the feed controller 16. The control unit 18 may also be arranged to control an effect regulator 28 of the suction device or to urge the operator to increase the effect of the suction device. This is preferably an increase of the power of the suction device to increase the air flow in the conveying conduit 11. However, the power may also be decreased if the air flow is determined to be larger than needed.

[0045] The sensor 17 for monitoring the actual parameter representing the airflow may be a direct meter, or a meter that measures a parameter from which the airflow may be calculated. The airflow can be a volumetric airflow, or an air mass flow measured or calculated from the parameter monitored by the sensor. It suffices to measure the airflow, or the actual parameter representing the air flow airflow, in or close to the suction device in order to deduce the airflow in the conveying conduit. As an alternative, under specific circumstances, it may be possible to monitor the power consumption of the suction device as a parameter representing the airflow in the conveying conduit.

[0046] Thus, the monitored actual parameter representing the airflow can be the actual airflow (volumetric airflow or air mass flow), a parameter relating to the air flow, or a parameter that varies as a function of the air flow from which the airflow can be calculated or estimated such as the air flow velocity, air flow velocity change rate or the dynamic pressure or the like. It is preferred that the monitored actual parameter representing the airflow is the actual air mass flow or a parameter that varies as a function of the air mass flow. This has been found to provide the most reliable information about the status of the rock transporting process in the conveying conduit 11.

[0047] In fig. 1 , the feed controller 16 is very schematically represented by an arrow indicating that the inlet end 12 of the conveying conduit 11 may be moved towards or away from the supply point 21 where rock material 20 to be transported is provided. Alternatively, rock material may advantageously be provided to the inlet end of the conveying conduit 11 , e.g. by means of scrapers or the like, which would be controlled by the feed controller. Fig. 1 represents a general embodiment of the invention in which the system is utilized to transport rock material from one point to another. Within the scope of the invention the invention the system may be implemented as part of different specific embodiments for different applications. [0048] The present invention may e.g. be implemented in different applications of mining or rock excavation operations, such as tunnel boring machines where the rock is mechanically excavated using large cutting heads having disc- or roller cutters that are brought against the rock in a rotating manner as known in the art. Depending on the design of the machine the excavated rock may be brought directly into the conveying conduit of the system or brought into the system from a buffering location, such as a pile of fragmented rock material on the tunnel floor, or from another conveying system. The present method and system for transporting rock material may also be useful to handle the material transport from so-called long wall mining machines or different types of rotary cutting machines used for soft rock excavation or coal mining.

[0049] The control unit for controlling such machines can be arranged to control the provision of rock material to the inlet end of the conveying conduit and the machines can also be configured to control the rate of excavation of stone material, e.g. by adjusting the thrust force or the speed of advancement or the rotational speed of a cutting head to thereby control the provision of rock material to the inlet. In accordance with the invention, this controlling is done in response to a parameter representing the air flow in the conveying conduit. This can be done manually by an operator or directly by the control unit.

[0050] In fig. 2 a specific embodiment of the invention is shown, in which the inlet end 12 of the conveying conduit 11 is connected to an excavation machine, in this case a drilling machine 1 , that is arranged on a drill rig 2. As is apparent from the detailed view in fig. 3 the drill rig 2 further comprises a carrier 3 for carrying drill string components 5, which are to be interconnected to a drill string. The drill rig 2 also comprises a power unit 4 for providing the drilling machine 1 with power. The drilling machine 1 is arranged on a derrick 6 that is adapted to be fixed at a drilling location, e.g. in a mine, by means of fixation supports 7. The drilling machine is arranged to be driven to and from along said derrick 6.

[0051] In conformity with the general representation of fig. 1 the specific embodiment of fig. 2 includes a conveying conduit 11 with an inlet end 12, which in the shown

embodiment is connected to a drilling machine 1. The conveying conduit 11 may be divided into three sections; a first section A connecting an outlet of the drilling machine 1 to a connection point at the drill rig 2, to which a second section B of the conveying conduit 11 is connected. A third section C of the conveying conduit 11 extends from the extraction unit 15 to the suction device 14. Said third section C is hence arranged to transport air, wherein the extraction unit 15 is provided with a separator 23, typically in the form of grid or the like where the rock material is allowed to be separated by gravity from the air. The length of the conveying conduit may vary and may be up to 100 meters or more. It may also be provided to transport the rock material at least partly upwards. Specifically, the second section B of the conveying conduit 11 may be much longer in relation to the first and third sections A and C, respectively.

[0052] The second section B may have a somewhat wider cross section than said first section A. In a very specific embodiment, the diameter Di of the first section A is about 265 mm and the diameter D2 of the second section B is about 300 mm, e.g. about 10-20 % larger in diameter than the first section A. Typically, in such an embodiment with those specific measures, the airflow is ideally kept between 4 and 7 m³ per second, or more specifically between 4,5 and 6 m³. The dynamic pressure may typically be kept at around 1-2 kPa.

However, these specifications are not restrictive of the invention but are only examples relevant for a very specific embodiment of the invention. The parameters need to be individually specified for a specific installation and is set by a skilled person based on the notion that the mass airflow should be kept continuous and kept above a specific threshold.

[0053] In order to manage the increasing cross section of the conveying conduit 11 from section A to section B the connection point at the drill rig comprises an auxiliary air inlet 19 from which second part B of the conveying conduit 11 extends to the extraction unit 15. The auxiliary air inlet 19 is preferably of an ejector type providing an increased flow rate inside the conveying conduit 1 1 , wherein a throttled airflow is received into the conveying conduit 11 at said auxiliary air inlet point. In one possible embodiment the added air flow from the auxiliary air inlet 19 can be controlled by varying the inlet size. The auxiliary inlet can thus be controlled in relation to the monitored actual parameter representing the airflow in the conveying conduit 1 1. Typically, the pressure will be the same in all sections A, B and C of the conveying conduit, but since the cross section is larger in section B than in section A the mass flow will be higher in section B than in section A. The greater the difference in diameter is between the two sections A and B the greater the effect of the increased airflow will be.

[0054] Also, more than one auxiliary air inlet 19 may be arranged, or the conveying conduit may be arranged without auxiliary air inlets, except for the open inlet end 12, where both air and rock material is received. The airflow is accelerated at the auxiliary air inlet 19 by the relative pressure difference, where the pressure is about 0.5 Bar inside the auxiliary air inlet 19 and about 1 Bar outside the same. The fact that the auxiliary air inlet 19 is shaped as an ejector with a throttled inlet and an acceleration portion will lead to that the pressure difference will create a substantial acceleration of the air. [0055] Fig. 4 is a schematic view of a possible embodiment of an auxiliary air inlet 19. The auxiliary air inlet 19 comprises an inlet part 24 and an outlet part 25, which parts are arranged with a circular gap between them. The circular gap constitutes a slit opening 26 through which a controlled quantity of air is allowed to enter. The slit opening 26 may e.g. be arranged as ring shaped slit or as a plurality of slits arranged along the circumference of the auxiliary air inlet 19 or in any other configuration providing a controlled and substantially laminar flow. The inlet part 24 may be connected to the first section A of the conveying conduit 11 and the outlet part 25 may be connected to the second section B of the same, downstream of the first section A. (See figs. 2-3).

[0056] It is important that the slit opening 26 has a limited and controlled size, such that it will not lead to a reduction of the upstream suctioning effect, i.e. the airflow in the first section A of the conveying conduit 11. The slit opening 26 is preferably dimensioned so as to allow entrance of an amount of air that implies a maintained or even increased air velocity of the airflow involving stone material inside the conveying conduit 11. A maintained or increased air velocity of the airflow is achieved as a consequence of the increasing width of the conveying conduit 11. In the shown embodiment this increased width is achieved in that the outlet part 25 of the conveying conduit 11 comprises a widening portion 27 with cross section that increases continuously and substantially seamlessly from the slit opening 26 towards the second section B of the conveying conduit. This sort of "soft" increase of the cross section is advantageous in that an increased airflow velocity thereby may be achieved while maintaining a substantially laminar airflow.

[0057] In addition to the above characteristics of the airflow it may also be possible, within the scope of the invention, to provide a varying suctioning effect depending on variations of properties influencing the airflow in the conveying conduit. For instance, the suctioning effect may be set to a specific level depending on the fix parameters in a specific application that influences the airflow. As an example, the suctioning effect may be set to an elevated level in correspondence to that a longer conveying conduit 11 is utilized or to compensate for a conveying conduit arranged to transport the rock material upwards, against gravity, e.g. up from a mining location. An effect regulator 28 is arranged at the suction device 14 in order to control the suctioning effect of the suction device 14.

[0058] Further though, the suctioning effect may be adjusted in response to a monitored actual parameter relating to the airflow in the conveying conduit. If it is noted that said monitored actual parameter decreases, e.g. below a certain threshold, the suction device 14 may be controlled to a higher effect, to thereby increase the suctioning effect. In a specific embodiment the effect may be increased up to a specific threshold, which may be the maximum effect of the suction device, or lower, before the provision of rock material to the inlet end of the conveying conduit is adjusted. Hence, as a first measure the suctioning effect of the suction device may be controlled in response to the monitored actual parameter, and, as a second measure, if the controlling of the suctioning effect does not affect the monitored actual parameter in a desired manner, adjusting the rate of provision of rock material to the inlet end of the conveying conduit.

[0059] Fig. 5 is a schematic view of a drilling machine 1 in operation, fixed at a drilling location in a mine by means of fixation supports 7. A drill string 8 comprised of several hollow drill string components 5, 5', 5" extends from the drilling machine 1 , which is arranged on a derrick 6. At the outer end of the drill string 8, extending into the rock which is being excavated, a cutting head 9 is arranged. The cutting head 9 is arranged to crush the rock into drill muck, which is subsequently transported through the inside of the drill string 8 to the inlet end 12 of the conveying unit 11 as indicated in figures 2 and 3. The rock drilling machine 1 may be used to provide a bore for ore bearing rock or to provide a through hole, e.g. to produce a tunnel or to connect different mining galleries for pressure equalizing purposes.

[0060] In the following a method in accordance with the invention will be described. The method relates to transporting rock material such as drill muck in a conveying conduit by means of a forced airflow. The method comprises the steps of producing an airflow in a conveying conduit 11 inside which the rock material is to be transported by means of a suction device 14 arranged at an outlet end 13 of the conveying conduit. Rock material is provided to the inlet end 12 of said conveying conduit. The rock material is extracted from said conveying conduit at an extraction point 22 between the inlet end and the outlet end at an extraction device 15. Preferably, the extraction device 15 comprises an accumulation chamber and a trap door 23 through which the rock material may be let out from said accumulation chamber. Preferably, the system is paused and the suction device turned off or down when the trap door 23 is opened to let the accumulated rock material out. However, as an alternative, a gate lock arrangement may be provided to continuously allow collected rock material to be released without pausing the operation.

[0061] During the transport of rock material, an actual parameter representing the airflow in the conveying conduit is monitored. Further, the suctioning effect of the suction device 14 and/or the provision of rock material to said inlet end of the conveying conduit is controlled in response to said monitored actual parameter. In response to that said monitored actual parameter reaches below a threshold a command is issued by the control unit 18 to reduce a speed of provision of rock material 20 to the inlet end 12 of the conveying conduit 11 and/or to increase the suctioning effect of the suction device 14. The command may be issued in response to that the monitored actual parameter representing the airflow that is measured by a sensor 17 reaches below a first threshold value, either directly to the feed controller 16 or to an operator controlling said feed controller 16.

[0062] The command may also be to completely stop the provision of rock material to the inlet end of the conveying conduit in response to that the monitored actual parameter representing the airflow reaches below said first threshold value. Normally, the provision of rock material to the inlet end of the conveying conduit may be resumed as soon as the monitored actual parameter representing the airflow reaches above said first threshold value, or preferably as soon as the monitored actual parameter representing the airflow reaches above a second, higher threshold value. The second higher threshold value provides a precaution so as to assure that a plug or any other obstacle that hinder the way, will be fully released before the provision of rock material is resumed. Preferably though, the first threshold value is chosen to correspond to a level representing an airflow indicating that the conveying conduit risk getting plugged, before it actually is plugged.

[0063] The sensor 17 may be a transducer placed in an internal conduit with a cross sectional area A within the suction device. It measures the dynamic pressure with the help of several Pitot (or Prandtl) tubes. The Pitot tube has a mouth facing the airflow some distance from the tube walls. Due to the velocity of the air stream a certain over pressure P is created in this tube. The relation between this pressure and the air velocity follows Bernoulli's theorem, why the velocity v can be deducted.

[0064] A static pressure P_stat may be measured though a hole perpendicular to the conduit. This static pressure is used to calculate the air density p. For an accurate reading the temperature T also needs to be measured, but in many applications the temperature differences are so small that its variation may be neglected from the equation. The air mass flow may be calculated as the velocity v of the airflow times the density p of the airflow times the area A of the conduit. Preferably, the actual parameter representing the airflow is the actual air mass flow, or a parameter that varies as a function of the air mass flow from which the air mass flow may be calculated or estimated.

[0065] Further, in most applications a table or the like may be used. Therefore, in reality, it suffices to monitor a parameter that in one way or another represents the airflow, e.g. the dynamic pressure or the air velocity. From the monitoring of this parameter a threshold may either be mathematically deduced or empirically tested for a specific system. The threshold may also correspond to a gradient of the monitored actual parameter.

Specifically, a rapid decrease of the airflow, or the parameter representing the airflow, in particular the air mass flow, may be an indication of that a blocking or plug is about to form in the conveying conduit 11. The threshold may thus be chosen to represent a specific decrease of the airflow and not to a specific value of the airflow.

[0066] Normally, the airflow decreases more or less linearly to a certain point, at which it decreases more rapidly. In this aspect it is useful to use a gradient as a threshold.

However, the point at which the airflow starts to decrease more rapidly may be relatively close to a point where a plug is formed and waiting to this point may hence indulge a certain risk. Therefore, it may be advantageous to take action when the airflow reaches a threshold value that is above a point where the airflow starts to decrease more rapidly. This is however up to an operator to decide, either by setting the threshold in advance with a certain level of safety margin, or by the field operator by reacting before a set threshold is reached. Further, a set threshold may be adapted during operation so as to further optimize operation underway.

[0067] An indication system may be arranged that continuously indicates the monitored actual parameter representing the airflow, which indication system may include a scale for representing the monitored actual parameter representing the airflow with respect to different ranges, i.e. low, medium and high airflow ranges, where a command to reduce a speed of provision of rock material to the inlet end of the conveying conduit is issued when the airflow reaches in to the low airflow range. The command may be subtle in to the extent that an operator knows that the provision of stone material should be decreased at a certain airflow level or following a certain decrease of airflow level without receiving a specific command to reduce the provision of stone material to the inlet end. An indication of the level of airflow may hence be sufficient, as long as the operator knows at which point, i.e. at which threshold, the provision of stone material should be decreased

[0068] A command to revise a parameter related to the operation of a drilling machine is issued in response to that the monitored actual parameter relating to the airflow reaches below a first threshold value. Such a command may e.g. be to reduce the excavation speed of a rock excavation machine and, in the specific case of a drilling machine, to reduce a thrust force acting on a cutting head or the rotational speed of a cutting head of the drilling machine in response to that the monitored actual parameter representing the airflow reaches below a first threshold value. This applies in particular to a drilling machines. Further, the control unit may be arranged to continuously control the feed controller 16 in response to the monitored airflow. [0069] A threshold may also be used as a target threshold at which the transport of rock material is close to an optimum value. In such an embodiment the provision of rock material to the inlet of the conveying conduit may be continuously controlled in response to the actual parameter representing the airflow to lie as close as possible to said threshold. Hence, if the airflow is monitored as higher than the optimal threshold the provision of rock material to the inlet of the conveying conduit may be increased, and if, on the contrary, the airflow is monitored as lower than the optimal threshold the provision of rock material to the inlet of the conveying conduit may be decreased.

[0070] Further, within a certain interval of airflow the operation may be considered as optimal such that the provision of rock material to the inlet of the conveying conduit may be kept relatively constant whenever the monitored actual parameter representing the airflow is within said range.

[0071] The suction effect of the suction device 14 may also be continuously controlled in response to the actual parameter representing the airflow to help keep the airflow at an optimal level. In the application of a drilling or excavation machine with a cutting head the thrust force applied by the machine will be reduced or even totally released in response to a decreased level, while the rotation of the drill string and cutting head may be upheld. In another embodiment both the thrust force and/or the rotation speed of the cutting head may be reduced sequentially or simultaneously in response to that the monitored actual parameter representing the airflow reaches below a first threshold value.

[0072] The monitoring of a parameter representing the airflow in the conveying conduit is preferably performed at a point downstream of the extraction point 22 by monitoring the airflow at said downstream point. In the shown embodiment the sensor 17 for monitoring the airflow is arranged inside the suction device 14. It may however be arranged at any point along the conveying conduit 11 , preferably it is however arranged downstream of the extraction unit 15 to avoid the hostile environment upstream of the extraction unit 15 caused by the flowing rock material inside the conveying conduit 11. Further, it may be

advantageous that the monitoring of the parameter relating to the airflow is done downstream of the auxiliary air inlet, since it allows a monitoring of the full airflow, including the air that is received at said auxiliary air inlet.

[0073] Above, the invention has been described with reference to specific

embodiments. The invention is however not limited to these embodiments. It is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.

Claims

1. A method of transporting rock material such as drill muck in a conveying conduit during an excavation operation of rock material by means of a forced airflow, the method comprising the steps of producing an airflow in a conveying conduit (11) inside which rock material is to be transported by means of a suction device (14) arranged at an outlet end (13) of the conveying conduit; providing rock material to an inlet end (12) of said conveying conduit; and extracting rock material from said conveying conduit at an extraction point (22) between the inlet end and the outlet end; characterised by monitoring an actual parameter representing the airflow in the conveying conduit and to control a set parameter that at least indirectly governs the airflow in the conveying conduit in response to the monitored actual parameter.

2. The method according to claim 1 , wherein the set parameter that at least indirectly governs the airflow in the conveying conduit is a parameter related to the provision of rock material to said inlet end (12) of the conveying conduit (11 ) and/or a parameter related to the suction effect of the suction device (14).

3. The method according to claim 2, wherein a command to reduce a rate of provision of rock material to the inlet end of the conveying conduit (11) or a command to increase the suction effect of the suction device is issued in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

4. The method according to claim 3, wherein the command to reduce a rate of provision of rock material to the inlet end (12) of the conveying conduit (11 ) is a command to stop the provision of rock material to the inlet end of the conveying conduit.

5. The method according to either of claims 1 or 2, wherein the inlet end (12) of the conveying conduit (11) is connected to an excavation machine (1 ), and wherein a set parameter related to the operation of an excavation machine is controlled in response to the monitored actual parameter representing the airflow.

6. The method according to claim 5, wherein a thrust force acting on a cutting head (9) of the excavation machine (1) is controlled in response to the monitored actual parameter representing the airflow.

7. The method according to claim 6, wherein a command to reduce a thrust force acting on a cutting head (9) of the excavation machine (1 ) is issued in response to that the monitored actual parameter representing the airflow reaches below a first threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

8. The method according to anyone of the preceding claims, wherein said actual

parameter representing the airflow in the conveying conduit (11) is continuously categorized in one of at least two airflow ranges, a lower, and a medium airflow range, wherein commands are issued to keep the suction effect of the suction device (14) in the medium airflow range.

9. The method according to anyone of the claims 1-7, wherein said actual parameter representing the airflow in the conveying conduit (11 ) is continuously categorized in one of at least three airflow ranges, a lower, a medium and a higher airflow range, wherein commands are issued to keep the suction effect of the suction device (14) in the medium airflow range.

10. The method according to anyone of the claims 1-7, wherein the monitored actual parameter representing the airflow in the conveying conduit (11 ) is continuously categorized in one of at least three airflow ranges, a lower and a medium airflow range, wherein the drilling is at least intermittently controlled in response to which range the monitored actual parameter representing the airflow may be categorized, and wherein a command to reduce a speed of advancement of the cutting head is issued when the monitored actual parameter is categorized as pertaining to the lower airflow range.

11. The method according to anyone of the preceding claims, wherein the monitoring of an actual parameter representing the airflow in the conveying conduit (11 ) is performed at a point downstream of the extraction point (22).

12. The method according to claim 3, wherein, as a first measure in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate, a command to increase the suction effect of the suction device (14) is issued, and wherein, as a second measure in a subsequent step, a command to reduce a speed of provision of rock material to the inlet end (12) of the conveying conduit (11) is issued.

13. A system (10) for transporting rock material (20) such as drill muck in a conveying conduit by means of an airflow, the system comprising:

a conveying conduit (11 ) having an inlet end (12) for receiving rock material to be transported and an outlet end (13);

a suction device (14) for creating an airflow, which suction device is arranged in connection to the outlet end (13) of the conveying conduit (11 ); and

an extraction unit (15) for extracting rock material (20) that has been transported in the conveying conduit (11 ), the extraction unit being arranged in fluid connection to both the inlet end (12) and the outlet end (13), characterised in that a sensor (17) is arranged to monitor an actual parameter representing the airflow in the conveying conduit (11), wherein a control unit (18) is arranged to control a set parameter that at least indirectly governs the airflow in the conveying conduit in response to the monitored actual parameter.

14. The system (10) according to claim 13, wherein the set parameter that at least

indirectly governs the airflow in the conveying conduit is a parameter related to the provision of rock material to said inlet end (12) of the conveying conduit (11) and/or a parameter related to the suction effect of the suction device (14)

15. The system (10) according to claim 14, wherein the control unit (18) is configured to issue a command to reduce a rate of provision of rock material to the inlet end of the conveying conduit (11 ) or a command to increase the suction effect of the suction device in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

16. The system (10) according to anyone of the claims 13-15, wherein an auxiliary air inlet (19) is arranged downstream of the inlet (12) of the conveying conduit (11 ) and upstream of the extraction unit (15), the auxiliary air inlet being of an ejector type providing an accelerated air flow inside the conveying conduit (11 ).

17. The system (10) according to claim 16, wherein the conveying conduit (11) has a widened cross-sectional area downstream of the auxiliary air inlet (19).

18. The system (10) according to anyone of the claims 13-17, wherein the inlet end (12) of the conveying conduit (11) is connected to an excavation machine (1) having a cutting head (9) arranged to be rotated and driven into a rock and to thereby produce rock material (20) to be transported away in said conveying conduit (11), and wherein the control unit (18) is configured to control a thrust force of said cutting head (9).

19. The system (10) according to claim 18, wherein the control unit (18) is configured to issue a command to reduce said thrust force in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate.

20. The system according to anyone of claims 13-19, wherein, as a first measure in response to that the monitored actual parameter reaches below a specific threshold value or that the monitored actual parameter representing the airflow decreases at a rate that is at or above a specific threshold rate, the control unit (18) is configured to issue a command to increase the suction effect of the suction device (14), and wherein, as a second measure in a subsequent step, the control unit (18) is configured to issue a command to reduce a speed of provision of rock material to the inlet end (12) of the conveying conduit (11 ).