WO2008094106A1

WO2008094106A1 - Rock drilling equipment and a method in association with same

Info

Publication number: WO2008094106A1
Application number: PCT/SE2008/000089
Authority: WO
Inventors: Göran JACOBSSON
Original assignee: Atlas Copco Rock Drills Ab
Priority date: 2007-01-31
Filing date: 2008-01-31
Publication date: 2008-08-07
Also published as: SE530810C2; WO2008094106A8; SE0700245L

Abstract

Rock drilling unit (1) with a thread (4) for being able to create a threaded connection to a drill unit (13) with a second thread (10). The rock drilling unit and the drill unit include means (8,15,9,16) for creating, after joining together of the units, a tight space comprising the threaded connection, and a duct (5) via which that space can be pressurised with a fluid before parting of the connection. A rock drilling rig including such rock drilling unit and/or drill unit is also described. A method for parting a threaded connection between such a rock drilling unit and drill unit is also described.

Description

Rock drilling equipment and a method in association with same

Technical field

The present invention relates to devices and a method for facilitating repeated taking apart and reuse of drill units in a rock drilling context, and to a rock drilling rig which includes such devices.

Background

For certain rock drilling rigs, the percussion unit which generates impacts on a drill is placed in direct connection with a drill bit at the end of the drill in a borehole, while a rotation unit on the rig above is adapted to generating rotary motion for the drill bit. The rotation unit may for the purpose be provided with an adaptor, which is usually connected to a further adaptor, a saver sub, which may itself be connected to a first drill pipe in a drill string comprising at least one drill pipe.

In other types of rock drilling rigs, a drill string may be connected to the rock drilling machine and may comprise a necessary number of drill rods, the leading drill rod being connected to a drill bit. The rock drilling machine generates impacts and a rotary motion, or rotation only, which is imparted to the drill bit via the drill rods in the drill string. The rock drilling machine is provided for the purpose with an adaptor which transmits the generated percussive force and rotary motion, or rotary motion only, to the drill string.

The units in the drill string, i.e. the respective drill pipes or drill rods, are provided at their respective ends with a thread of conical or cylindrical configuration, viz. an internal thread, a female element, at one end of the drill rod and an external thread, a male element, at the other end of the drill rod. A drill string may thus comprise more than one drill rod, with the male and female elements of two separate drill rods being screwed to one another to form a threaded connection.

The drill string may be connected to a saver sub which is itself connected to the rotation unit or the rock drilling machine, or to the adaptor of the rotation unit/the rock drilling machine, by threads likewise of conical or cylindrical configuration.

During drilling in rock with a rock drilling machine which, when in use, comprises both a rotation unit and a connected drill string, the threads at the respective threaded connections between drill pipes and at the connections between first drill pipe and saver sub, between saver sub and adaptor and between adaptor and rotation unit/rock drilling machine, will usually be increasingly firmly screwed together when the direction of rotation of the rotating units is such as to endeavour to screw the male and female elements of a threaded connection more firmly to one another. This is still clearer in percussion drilling, in which a shock wave also repetitively passes from one element to another and causes the threads to tighten increasingly the longer the machine runs. This applies in particular at the threaded connection between the saver sub and the adaptor and at the threaded connection between the adaptor and the rotation unit/the rock drilling machine. Since these threaded connections are situated innermost in the drilling equipment comprising rotation unit, adaptors and drill string and therefore absorb longest the twisting forces at the threaded connection, said threaded connections are subject to the greatest screwing forces. A reason for this is that these threaded connections are not taken apart during drill pipe or drill bit changing or during the jointing operation required when drilling a deeper hole than is possible with one drill string or drill pipe. In such cases further elements are therefore incorporated progressively as the hole is drilled deeper, whereas the drill rods are removed one after another when the drill string is lifted out after completing the drilling of the hole. Thereafter the drill rods are incorporated again during the drilling of the next hole. The threaded connection is thus subject to great forces, both rotary and percussive, but has also to withstand being taken apart and screwed up again a large number of times.

Parting the threaded connection between drill units in the drill string involves their being unscrewed by means of hydraulic jaws adapted to gripping the drill units on their respective sides of the threaded connection. Jaws of this kind can nevertheless normally not grip the rotation unit/the rock drilling machine and the adaptor simultaneously, nor the adaptor and the saver sub simultaneously, so this type of auxiliary means is not usable in this context. Particularly in conical threaded connections, it is difficult to part the saver sub from the adaptor and the adaptor from the rotation unit or the rock drilling machine. It is often only with great difficulty that they can be freed from one another, despite the availability of certain other tools suitable for the purpose.

US specification 3 233 499 refers to an example of a connection in which a nut can be slackened by applying liquid pressure in a gap. The nut concerned is of a very special type with specific devices adapted to nut release from a threaded rod. Arrangements of the kind referred to in that specification are not applicable to threaded connections between drill units such as described above.

Specification EP 0 957 233 discloses a threaded connection for jointing of pipes in the oil and gas industry. A pressurised fluid is used mainly for assembling the threaded connection, but it is stated that it may also be used for parting of connections. The solution indicated is nevertheless not suitable for frequently repeated parting and reassembly, since the sealing method indicated will lead to plastic deformation of the sealing surfaces, particularly in relation to percussion drilling in which a shock wave has repetitively to pass through the connection. There is no reference to safety risks to personnel during parting of the connection arising from high pressure at the connection. Nor is there any such indication in specification GB 2 148 439, which refers to threaded connections which are snapped together but are unscrewed by pressurisation.

Object of the invention and its principal characteristics

An object of the present invention is to present a solution for reducing the disadvantages of the prior art technology.

An aspect of the invention proposes devices with characteristics according to the attached independent claims 1, 8 and 13.

A further aspect of the invention proposes a method with characteristics according to the attached independent method claim.

Further advantageous embodiments of the invention are set out in the dependent claims. Devices according to the invention are in general terms: The rock drilling unit 1 with a thread 4 making it possible to create a threaded connection to a drill unit 13 with a second thread 10. The rock drilling unit and the drill unit include means 8,15,9,16 for creating, after joining together of the units, a tight space comprising the threaded connection, and a duct 5 via which that space can be pressurised with a fluid before parting of the connection. Said means 8,15,9,16 should be so configured that the threaded connection can be opened and reclosed a large number of times with continuing tightness across the threaded connection when the units 1,13 are joined together. Moreover, at least one of the units 1,13 has to comprise means adapted to preventing the pressurised fluid from causing harm to personnel during parting of a threaded connection between the units 1,13. A rock drilling rig including a rock drilling unit and/or a drill unit as above is also comprised.

A substantial advantage afforded by the method and devices according to the invention is that parting a threaded connection between a rock drilling machine and a drill unit, as they are defined in the claims, with no damage to elements cooperating in the connection and no harm to personnel effecting the parting, is greatly facilitated. Supplying a fluid at high pressure via the duct 5 to a connection between a rock drilling unit 1 and a drill unit 13 establishes a considerable and mainly radially acting force at the threaded connection, thereby reducing the force involved in unscrewing the threads of the connection from one another. The only tool required during the parting may thus be confined to tongs of a standard type. It is often sufficient to fix the outer element and run the rotation unit in the opposite direction of rotation from that applied during drilling.

Throughout this specification, fluid includes grease, liquid, gas or mixtures whose main constituent is classifiable within these expressions.

Brief description of the drawing

The diagram depicts in cross-section a connection between two units in a rock drilling context, each of them exemplifying the invention, viz. a rock drilling unit 1 on the right and a drill unit 13 on the left. In this specific example illustrated, the right element takes the form of one end of the spindle of a rotation unit for rock drilling and the left element takes the form of one end of an adaptor. The threads 4 and 10 involved in the connection are enclosed in a sealed space which can be pressurised via a duct 5 which in this example has its end fitted with a nipple 7 comprising a check valve for connecting, for example, a grease gun before parting of the connection. Also depicted are sealing surfaces 8,15,9,16 so disposed that the surfaces 15,16 which seal against the inner element of the connection, i.e. against the axial hole, are opened earlier during parting of the connection than the sealing surfaces 8,9 situated further out in the connection. This is to prevent pressurised fluid from flowing towards the operator.

Detailed description of preferred embodiments

A number of exemplifying versions of the invention are described below with reference to the attached drawing.

The diagram shows an example of the type of connection in which the arrangement according to an aspect of the invention is applicable. The connection incorporates one end of an adaptor 13 intended to be fittable to one end of a spindle 1 of a rock drilling machine or a rock drilling rotation unit.

The adaptor 13 has at its one end an outer wall 18 in the form of a truncated cone, and this outer wall is at least partly provided with an external conical thread 10. A hole may extend axially through, and along the centreline of, the adaptor. This hole may be used for transfer of pressurised air, or water or oil, for driving the drilling machine at the tip of an undepicted drill string connected to the other end of the adaptor.

The connection also includes a second drill unit, hereinafter called the rock drilling unit 1, exemplified in this case by the spindle of the rock drilling rotation unit or the rock drilling machine. This spindle 1 is provided at a first end with an internal conical thread 4. There is of course nothing to prevent the threads being vice versa, i.e. the spindle having an external conical thread intended to be accommodated in an adaptor which has an internal thread.

The same type of connection may be effected between an adaptor and a saver sub, in which case the adaptor corresponds to ref. 1 and the saver sub to ref. 13. This case is nevertheless not depicted in the drawing, since the actual threaded connection in the respective case is equivalent in that substantially the only difference is in the outer configuration of the components.

A threaded connection may be formed by said external and internal threads 10,4 being screwed to one another. A vital point for the invention is that at least one out of the rock drilling unit 1 and the drill unit 13, i.e. in the drawing the spindle and the adaptor or other corresponding units, is provided with a duct 5 connecting the shell surface 2,14 of the unit and the wall 3,18 along which the thread 4,10 is provided. It is also essential that both the rock drilling unit 1 and the drill unit 13 have mutually corresponding sealing surfaces 8,15; 9,16 situated along the wall 3; 18 on respective sides of the thread 4; 10. These sealing surfaces have to be so disposed that, after joining together of the rock drilling unit and the drill unit, they can seal against one another directly or indirectly and thus form a sealed and therefore pressurisable space in which the threads of the connection constitute at least parts of the surfaces delineating the space. It is essential that the orifice of the duct 5 in the shell surface 2,14 be accessible from outside even after joining together of the units 1,13 and that the orifice in the wall 3,18 be situated between said sealing surfaces 8,15,9,16. This makes it possible for the threaded connection formed by joining the units together to be pressurised by a fluid, as previously defined, being supplied to the duct 5 under pressure. Parting of the connection is thus substantially facilitated. It is important that the sealing surfaces be so configured that during tightening of the connection they do not cause permanent deformation in one another of such a kind as to make it impossible for the connection to be opened and reclosed a large number of times without the surfaces having to be machined. It is at the same time advantageous that the sealing surfaces, as depicted in the diagram, constitute a circular cylindrical portion of the units 1,13. It is also advantageous that the sealing surfaces of the rock drilling unit and the drill unit seal indirectly to one another via an elastic seal means 11. This seal means may with advantage comprise an O- ring 11 or other seal suited to withstanding high pressure. It is then advantageous if at least one out of the rock drilling unit and the drill unit is provided with at least one annular groove for fitting the seal means. This groove then includes one of the sealing surfaces. A further possibility for withstanding high pressure is for a support ring 12 also to be fitted in the groove. If only one groove in all is provided in the units 1,13, it is advantageous that it be situated close to the outer element of the connection, corresponding to groove 9, in order to achieve the best possible seal for the sake of personnel safety. In the case with no groove, the inner sealing surfaces 15,16 will then constitute a gap seal. Better effects are nevertheless achieved if the inner surfaces 15,16 are also provided with grooves and seal means.

In the example depicted in the drawing, a first end of the spindle 1 is surrounded by an outer wall or shell surface 2 of circular cross-section which surrounds the first end of the spindle. At the same first end of the spindle 1, an internal conical wall 3 of circular cross-section is provided with an internal thread 4 and adapted to accommodating a corresponding conically configured external thread 10, as mentioned in relation to the drill unit 13, exemplified in this case by the adaptor. The internal thread 4 is provided along a section of said internal conical wall 3. A duct running through between the outer wall and the inner wall is provided in this first end of the spindle. The nipple 7 is fittable in the outer wall in said duct where this duct cuts the outer wall. A connecting means 6 for the nipple 7 is provided in the orifice of the duct at the shell surface 2. This connecting means has to be capable of creating a tight and mechanically stable connection to the nipple. This is normally effected by a thread but may also, for example, be effected by a constriction close to the actual orifice to prevent a nipple with expanding fastening means from becoming detached at high pressure.

In cases where the threaded connection is in the form of a saver sub screwed to an adaptor, the description remains as in the previous paragraph. The rock drilling unit 1 may then be either the adaptor or the saver sub, and the drill unit 13 may accordingly be the other corresponding unit. Likewise, the connection may in the same manner involve two drills or drill rods forming part of a drill string or a drill bit and a drill pipe or drill rod.

An intention of the configuration according to the invention is that the pressure of the fluid, as previously defined, should cause the space between the threads to be subjected to a force directed substantially radially and therefore expand. This facilitates the parting of a drill unit connected to a rock drilling unit by a threaded connection. If the fluid comprises grease or oil or is in some other way provided with lubricating properties, these fluid properties will help to reduce the friction between the elements of the threaded connection and thereby further facilitate the parting. On the other hand, thorough cleaning of the threads may then be necessary before refitting, to prevent the threads from slackening at an incorrect stage, e.g. while incorporating a new drill pipe, which may be preceded by the rotation unit being run in the opposite direction of rotation while drill pipe/drill rod is being fastened. In this respect it is more desirable that the fluid should not have lubricating properties.

It is therefore important to prevent the nipple 7 being confused with an ordinary grease nipple and to prevent, for example, grease being mistakenly injected during ordinary servicing of the rock drilling equipment. One possibility would be for the nipple to be concealed by a cap to provide protection not only against dirt and mechanical damage but also against the above risk of confusion. The simplest way of providing such protection, however, is by the nipple normally not being fitted but being replaced by a plug during ordinary use. When a need for extra force to release the connection arises, the nipple is connected instead of the plug, and the fluid is supplied.

The nipple is of a high-pressure type, i.e. it has to be dimensioned for supply of a fluid, as defined previously, at high pressure, advantageously at least 800 bar.

The fluid may be supplied to the duct 5 by means of an ordinary grease gun or, if so desired, a hand-operated oil pressure pump. Even at significantly lower pressures, e.g. from 300 bars, however, supplying the fluid may facilitate the parting. The pressure applied to the connection is within the range 100 to 1000 bar, preferably 500 to 800 bar. Higher pressures may also arise but would entail using components of a higher class.

Nipple of a high-pressure type means, for example, that the check valve, usually in the form of a ball which seals against the orifice of the nipple, has to withstand the pressure levels indicated.

Where O-rings are used as seals, they may preferably be made of harder material, and be provided with support rings, so that the seals will be appropriate to the high pressure which occurs at the connection when the fluid, e.g. in the form of grease or oil, is injected.

The fluid supplied via the duct 5 may be injected into the actual threaded connection, via the channel which is always present between the crests on one thread and the valleys on the other thread and in the gap between the wall 3 of the rock drilling machine and the wall 18 of the drill unit.

It should also be noted that after injection of, for example, oil at high pressure, the connection may present a safety risk or risk of discharge to the environment when the threaded connection is parted. For this reason the configuration may be so arranged that the seal 15,16 which seals the connection in towards the axial hole is opened earlier during unscrewing of the connection than the seal 8,9 situated further out in the threaded connection, i.e. than the seal which has the larger diameter. This may for example be effected, as in the drawing, by arranging the locations of the grooves along corresponding sealing surfaces on the opposite rock drilling unit in such a way that during parting of the connection the inner groove leaves its corresponding sealing surface first. This makes it possible for the enclosed space in the threaded connection to be opened first towards the inner element of the threaded connection, so that any jet of oil at high pressure is directed inwards towards the axial cavity of the connection, thereby avoiding risks of harm to personnel or pollution of the environment.

Another way of dealing with the fluid is to provide either the rock drilling unit 1 or the drill unit 13 with a second duct of similar configuration to the first duct 5 except that, if this second duct is in the rock drilling unit, it may also have an orifice in the first duct 5 instead of, or in addition to, the orifice in the wall 3 between the sealing surfaces 8,15. The orifice of the second duct at the shell surface is provided with fastening means, e.g. a thread, for an openable evacuation means for the pressurised fluid. An openable evacuation means may also be fitted in said orifice. When pressurisation has taken place and the connection has therefore been rendered readily releasable, this evacuation means may be opened in order to deal safely with fluid outflow. Said means may, for example, take the form of an ordinary venting valve well known from, for example, hydraulic brake systems. To sum up, the rock drilling unit and the drill unit may each, as previously described, respectively comprise some of the following: rock drilling machine, rock drilling rotation unit, spindle for rotation unit for rock drilling, rock drilling adaptor, rock drilling saver sub, drill pipe, drill rod or drill bit.

In the use of rock drilling machines, one or more of these is generally fitted to a rock drilling rig for positioning and alignment and for control of constituent units of the rock drilling machines.

Seal devices on rock drilling units and drill units have to be able to withstand pressures of 100-1000 bar, preferably 500-800 bar.

A rock drilling unit may have its opposite end configured as a drill unit, or vice versa.

There is of course nothing to prevent the invention being applied in threaded units for rock drilling which have cylindrical instead of conical thread sections or have no axial hole running through them.

To enable the shock wave in percussion drilling to be transmitted between the units 1,13, it is important that the threaded connection be tightened so that the units are in firm direct metallic contact with one another in the axial direction, as illustrated in the drawing at the boundary surface 20, otherwise the thread will quickly become overheated by the friction heat.

It is also advantageous that the seal of the threaded connection should be along substantially circular cylindrical surfaces as depicted in the drawing.

To prevent plastic deformation which would limit the reusability of the units 1,13, the sealing surfaces are so configured that the pressure between them does not exceed the yield point of the material.

Claims

1. A rock drilling unit (1) including an outer shell surface (2) and a first thread (4) provided along a wall (3) at one end of the rock drilling unit, in which the rock drilling unit is also connectable to a drill unit (13) comprising a second thread (10) for forming a threaded connection between the threads (4,10) of the rock drilling unit (1) and of the drill unit (13) upon connection of the units to one another, which wall (3) is connected to or includes both a first sealing surface (8) and a second sealing surface (15), said sealing surfaces (8,15) being situated each on their respective side of the first thread (4), and the sealing surfaces (8,15) being adapted, after connection of the drill unit (13), to sealing directly or indirectly against corresponding sealing surfaces (9,16) provided on the drill unit, and in which the rock drilling unit further includes a first duct (5) with one end opening into the shell surface (2) and accessible from the outside of the rock drilling unit even after connection of the drill unit, and another end opening into said wall (3) between the sealing surfaces (8,15) of the rock drilling unit to make it possible, after connection of the drill unit (13), for a pressurised fluid to be introduced via the duct (5) to the threaded connection formed, thereby establishing a force directed substantially radially and acting separatingly upon the threaded connection in order to facilitate parting of the connection, characterised in that the rock drilling unit includes a first means for preventing the pressurised fluid from causing harm to personnel during the parting of the threaded connection.

2. A rock drilling unit according to claim 1, in which the sealing surfaces (8,15) are configured to not create such surface pressure against corresponding sealing surfaces (9,16) on the drill unit during assembly of the connection that plastic deformation occurs in either surface.

3. A rock drilling unit according to claim 1 or 2, in which said first means involves the sealing surfaces (8,15) being so configured that during parting of the threaded connection they, in cooperation with the corresponding sealing surfaces (9,16) on the drill unit, first open the enclosed space in the threaded connection towards the inner element of the connection, i.e. the inner sealing surfaces (15,16)

4. A rock drilling unit according to claim 1, in which said first means takes the form of a second duct with its one end in the shell surface and its other end between said sealing surfaces (8,15) or in the first duct (5), which second duct may be provided, in its orifice at the shell surface, with an openable evacuation means to make it possible, after connection of the drill unit and pressurisation of the resulting threaded connection, for there to be controlled evacuation of the fluid via the second duct during the parting of the threaded connection.

5. A rock drilling unit according to any one of the above claims, further comprising a groove including one of said sealing surfaces (8,15), the groove being adapted to fitting of a seal means (11).

6. A rock drilling unit according to any one of the above claims, in which the first thread is an internal thread.

7. A rock drilling unit according to any one of the above claims, in which the first thread is provided on a conically shaped surface.

8. A drill unit (13) including an outer shell surface (14) and a second thread (10) provided along a wall (18) at one end of the drill unit, in which the drill unit is also connectable to a rock drilling unit (1) configured according to any one of the above claims in order to form a threaded connection between the threads (10,4) of the drill unit (13) and of the rock drilling unit (1) upon connection of the units to one another, which wall (18) is also connected to or includes both a third sealing surface (9) and a fourth sealing surface (16), said sealing surfaces (9,16) being situated each on their respective side of the second thread (10), and the sealing surfaces (9,16) of the drill unit being adapted, after connection of the rock drilling unit (1), to sealing directly or indirectly against sealing surfaces (8,15) provided on the rock drilling unit to make it possible, after connection of the rock drilling unit (1), for a pressurised fluid to be introduced via the duct (5) to the threaded connection formed, thereby establishing a force directed substantially radially and acting separatingly upon the threaded connection in order to facilitate parting of the connection, characterised in that the drill unit includes a second means for preventing the pressurised fluid from causing harm to personnel during the parting of the threaded connection.

9. A drill unit according to claim 8, in which the sealing surfaces (9,16) are configured to not create such surface pressure against corresponding sealing surfaces (8,15) on the rock drilling unit during assembly of the connection that plastic deformation occurs in either surface.

10. A drill unit according to claim 8 or 9, in which said second means involves the sealing surfaces (9,16) being so configured that during parting of the threaded connection they, in cooperation with the corresponding sealing surfaces (8,15) on the rock drilling unit, first open the enclosed space in the threaded connection towards the inner element of the connection, i.e. the inner sealing surfaces ( 15 , 16) are adapted to opening earlier than the outer sealing surfaces (8,9).

11. A drill unit according to claim 8 or 9, in which said second means takes the form of a second duct with one end opening into the shell surface (14) and another end opening onto the wall (18) between said sealing surfaces (9,16) on the drill unit, which second duct may be provided, in its orifice at the shell surface (14), with an openable evacuation means to make it possible, after connection of the rock drilling unit (1) and pressurisation of the resulting threaded connection, for there to be controlled evacuation of the fluid via the second duct during the parting of the threaded connection.

12. A drill unit according to any one of claims 8 to 11, further including at least one groove (17,19) which itself includes one of the drill unit's sealing surfaces (9,16) and is adapted to fitting of a seal means (11).

13. A rock drilling rig including one or more rock drilling units and/or drill units according to any one of the above claims.

14. A method for parting of a threaded connection between a rock drilling unit (1) according to any one of claims 1 to 7 and a drill unit (13) according to any one of claims 8 to 12, including the steps of:

• supplying a fluid under pressure via a first duct (5) to a sealed space comprising said threaded connection • unscrewing the rock drilling unit (1) and the drill unit (13) from one another, with application of means for causing controlled evacuation of the pressurised fluid in order to prevent the fluid causing harm to personnel.

15. A method according to claim 14, in which the pressure imparted by the fluid is caused to amount to between 100 and 1000 bar, preferably between 500 and 800 bar.