Arrangement and method for installing casing

Abstract

An arrangement and a method for installing a casing in a borehole are described. The arrangement includes a casing, a boring pipe, which is adapted within the casing, and the boring pipe includes flow channels for compressed air and a flushing medium. The flushing medium flow channel is arranged to lead the flushing medium to the bottom of the borehole. The arrangement also includes a percussion hammer, which includes a compressed air operated percussion piston adapted in a cylinder of the percussion hammer, as well as hole drilling means for drilling a hole for the casing. The flushing medium flow channel is adapted to bypass the percussion piston or which flushing medium flow channel is adapted to pass through the percussion piston, and in which arrangement the drilling means additionally includes splines transmitting a rotating motion and adapted to conduct the compressed air that used the percussion piston through the splines.

Claims

1. An arrangement for installing a casing in a borehole, the arrangement comprising: a casing; a boring pipe which is adapted within the casing, the boring pipe comprising a flow channel for compressed air; a flushing medium flow channel arranged within the casing and arranged to lead the flushing medium to the bottom of the borehole, the casing being installed in the borehole permanently; a percussion hammer which comprises a compressed air operated percussion piston adapted in a cylinder of the percussion hammer; hole drilling means for drilling a hole for the casing; and guiding means for guiding exhaust air of the compressed air to a space between the percussion hammer and the casing, the flushing medium flow channel being adapted to bypass the percussion piston by leading the flushing medium around an outside of the percussion piston, or in which arrangement the drilling means additionally comprises splines transmitting a rotating motion and adapted to conduct the compressed air that operated the percussion piston through the splines, and in which arrangement the flushing medium flow channel is adapted to pass through the percussion piston.

2. An arrangement as claimed in claim 1, wherein, on the outside of the cylinder of the percussion hammer, there is adapted a shell, which together with an outer wall of the cylinder, forms part of the flushing medium flow channel, bypassing the percussion piston.

3. An arrangement as claimed in claim 2, wherein the part of the flushing medium flow channel, which part bypasses the percussion piston, extends circularly around the cylinder of the percussion hammer.

4. An arrangement as claimed in claim 2, where the shell adapted on the outside of the cylinder forms part of the outer surface of the percussion hammer.

5. An arrangement as claimed in claim 1, wherein, on the outside of the cylinder of the percussion hammer, there are adapted one or more pipes which form part of the flushing medium flow channel, bypassing the percussion piston.

6. An arrangement as claimed in claim 5, wherein the part of the flushing medium flow channel, which bypasses the percussion piston is at its top end connected to an adaptor of the boring pipe, having an adapter flow channel which is arranged to move the flushing medium flow channel further from a longitudinal center axis of the arrangement.

7. An arrangement as claimed in claim 5, wherein the arrangement further comprises at least one collar which is connected to the casing or to a casing shoe fixed to the casing, where the part of the flushing medium flow channel, bypassing the percussion piston, is by its bottom end connected to at least one collar.

8. An arrangement as claimed in claim 7 wherein at least one collar additionally comprises at least one locking member for locking the at least one collar to the casing or casing shoe.

9. An arrangement as claimed in claim 8, wherein at least one locking part is adapted to lock at least one collar to the casing or casing shoe by means of a pressurized flushing medium.

10. An arrangement as claimed in claim 8, wherein the at least one locking part comprises a pressure line which is adapted to lock the at least one collar to the casing or casing shoe.

11. An arrangement as claimed in claim 5, wherein the percussion hammer comprises a bottom member which has at least one flushing medium flow channel of the bottom member, which is adapted in flow connection to the part of the flushing medium flow channel, bypassing the percussion piston, and in which the hole drilling means comprises at least one flushing medium flow channel of the drilling means, which is adapted in flow connection to the flushing medium flow channel of the bottom member and to lead the flushing medium to the bottom of the borehole.

12. An arrangement as claimed in claim 11, wherein the flow channel of the bottom member comprises a circular flow groove which is adapted on the inner surface of the bottom member and which circulates in the plane of said inner surface which is at least substantially perpendicular to the longitudinal center axis of the arrangement.

13. An arrangement as claimed in claim 12, further comprising seals adapted on both sides of the circular flow groove.

14. An arrangement as claimed in claim 1, wherein the hole drilling means comprises at least one flushing medium flow channel of the drilling means, which is adapted to lead the flushing medium from the flushing medium flow channel to the bottom of the borehole, and in which arrangement the flushing medium flow channel is adapted to pass through the percussion piston.

15. An arrangement as claimed in claim 1, wherein the compressed air that operated the percussion piston is removed by an exhaust air channel that comprises a center opening in the hole drilling means, which is in flow connection to the cylinder of the percussion hammer, and at least one air channel passing radially from the center opening through a bottom member of the percussion hammer, the air channel being in flow connection to the space between the percussion hammer and casing.

16. An arrangement as claimed in claim 1, wherein the drilling means additionally comprises splines transmitting a rotating motion and adapted to conduct the compressed air that operated the percussion piston through the splines.

17. An arrangement as claimed in claim 1, wherein the compressed air that drove the percussion piston is removed by the exhaust air channel, the arrangement further comprising: at least one side exhaust air channel led past the hole drilling means, which is in flow connection to the cylinder of the percussion hammer; an air flow channel which is in flow connection to said at least one exhaust air channel; and at least one air channel passing radially from the air flow channel through the bottom member of the percussion hammer, this channel being in flow connection to the space between the percussion hammer and casing.

18. An arrangement as claimed in claim 17, wherein the side exhaust air channel is formed among the splines.

19. An arrangement as claimed in claim 17, wherein the circular air flow channel is adapted on the inner surface of the bottom member, is adapted against the drilling means, and circulates said part of the drilling means in a plane that is at least substantially perpendicular to the longitudinal center axis of the arrangement.

20. A method for installing a casing, the method utilizing an arrangement that comprises a casing and boring pipe, a percussion hammer and means for boring a hole, the method comprising: rotating the boring pipe inside the casing, the boring pipe comprising a flow channel for compressed air, a flushing medium flow channel arranged within the casing and arranged to lead a flushing medium to the bottom of the borehole, the casing being installed in the borehole permanently; driving the percussion hammer by the compressed air, the percussion hammer comprising a compressed air operated percussion piston adapted in a cylinder of the percussion hammer; and flushing the bottom of the borehole using the flushing medium flow channel which is adapted to bypass the percussion piston by leading the flushing medium around an outside of the percussion piston, or flushing the bottom of the borehole by the flushing medium which is led through the percussion piston to the hole drilling means and further to the bottom of the borehole, in which arrangement the drilling means additionally comprises splines which transmit a rotation motion and by means of which the compressed air that operated the percussion piston is led through the splines.

21. An arrangement for installing a casing in a borehole, the arrangement comprising: a casing; a boring pipe which is adapted within the casing, the boring pipe comprising a flow channel for compressed air; a flushing medium flow channel arranged within the casing and arranged to lead the flushing medium to the bottom of the borehole; a percussion hammer which comprises a compressed air operated percussion piston adapted in a cylinder of the percussion hammer; and hole drilling means for drilling a hole for the casing, wherein, on the outside of the cylinder of the percussion hammer, there is adapted a shell, which together with an outer wall of the cylinder, forms part of the flushing medium flow channel, bypassing the percussion piston, the flushing medium flow channel being adapted to bypass the percussion piston, or in which arrangement the drilling means additionally comprises splines transmitting a rotating motion and adapted to conduct the compressed air that operated the percussion piston through the splines, and in which arrangement the flushing medium flow channel is adapted to pass through the percussion piston.

22. An arrangement for installing a casing in a borehole, the arrangement comprising: a casing; a boring pipe which is adapted within the casing, the boring pipe comprising a flow channel for compressed air; a flushing medium flow channel arranged within the casing and arranged to lead the flushing medium to the bottom of the borehole; a percussion hammer which comprises a compressed air operated percussion piston adapted in a cylinder of the percussion hammer; and hole drilling means for drilling a hole for the casing, wherein the compressed air that operated the percussion piston is removed by an exhaust air channel that comprises a center opening in the hole drilling means, which is in flow connection to the cylinder of the percussion hammer, and at least one air channel passing radially from the center opening through a bottom member of the percussion hammer, the air channel being in flow connection to the space between the percussion hammer and casing, the flushing medium flow channel being adapted to bypass the percussion piston, or in which arrangement the drilling means additionally comprises splines transmitting a rotating motion and adapted to conduct the compressed air that operated the percussion piston through the splines, and in which arrangement the flushing medium flow channel is adapted to pass through the percussion piston.

23. An arrangement for installing a casing in a borehole, the arrangement comprising: a casing; a boring pipe which is adapted within the casing, the boring pipe comprising a flow channel for compressed air; a flushing medium flow channel arranged within the casing and arranged to lead the flushing medium to the bottom of the borehole; a percussion hammer which comprises a compressed air operated percussion piston adapted in a cylinder of the percussion hammer; hole drilling means for drilling a hole for the casing, wherein the compressed air that drove the percussion piston is removed by the exhaust air channel; at least one side exhaust air channel led past the hole drilling means, which is in flow connection to the cylinder of the percussion hammer; an air flow channel which is in flow connection to said at least one exhaust air channel; and at least one air channel passing radially from the air flow channel through the bottom member of the percussion hammer, the at least one air channel being in flow connection to the space between the percussion hammer and casing, the flushing medium flow channel being adapted to bypass the percussion piston, or in which arrangement the drilling means additionally comprises splines transmitting a rotating motion and adapted to conduct the compressed air that operated the percussion piston through the splines, and in which arrangement the flushing medium flow channel is adapted to pass through the percussion piston.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in more detail in the accompanying drawings, in which

(2) FIG. 1 is a schematic sectional side view of an arrangement for installing a casing,

(3) FIG. 2a is a schematic sectional side view of a second arrangement for installing a casing,

(4) FIG. 2b shows a cross section A-A of the arrangement of FIG. 2a,

(5) FIG. 3a is a schematic sectional side view of a third arrangement for installing a casing,

(6) FIG. 3b is a schematic sectional side view of a detail of the arrangement of FIG. 3a,

(7) FIG. 4a is a schematic sectional side view of an arrangement for installing a casing,

(8) FIG. 4b is a schematic sectional side view of a detail of the arrangement of FIG. 4a,

(9) FIGS. 5a to 5c are sectional side views of alternative details of a collar of the arrangement of FIGS. 4a and 4b,

(10) FIG. 6 is a schematic sectional side view of a detail of an arrangement,

(11) FIG. 7a is a schematic sectional side view of an arrangement for installing a casing,

(12) FIG. 7b is a schematic sectional side view of a detail of the arrangement of FIG. 7a, and

(13) FIG. 8 is a side view of a detail of collar of an arrangement.

(14) For the sake of clarity, the figures show the invention in a simplified manner. Similar parts are indicated in the figures by the same reference numbers.

DETAILED DESCRIPTION

(15) FIG. 1 is a schematic sectional side view of an arrangement for installing a casing.

(16) The arrangement 100 comprises a casing 1, which is a tubular piece installed in the ground, typically permanently. At the installation stage of the casing 1, boring pipe 2 has been adapted inside it to be rotated inside the casing. The arrangement 100 further comprises a percussion hammer 5 which is operated by compressed air. For this purpose, the arrangement 100 features a flow channel for compressed air 3. The bottom X of the borehole is flushed by a flushing medium which is fed to the bottom B of the borehole through the flow channel 4.

(17) The flushing medium may be water, a mixture containing water, such as boring sludge, or another suitable substance in a flowing form.

(18) The percussion hammer 5 shown in FIG. 5 is a compressed air operated DTH hammer (down-the-hole-hammer). Obviously, the percussion hammer 5 may, as concerns it basic idea, be a hammer other than a DTH hammer.

(19) Note, however, that the drawings only show the hammer parts that are essential from the viewpoint of the invention. The figures show an embodiment of the DTH hammer, which does not utilise a foot valve installed to the top end of a pilot crown. The arrangement according to the invention is naturally also suitable for embodiments provided with a foot valve.

(20) The percussion hammer 5 comprise a compressed air operated percussion hammer 6 which is adapted to the cylinder 9 of the percussion hammer movably back and forth.

(21) The arrangement 100 further comprises hole drilling means 8 for boring a hole into the ground for the casing 1. In the embodiment shown in the figure, the drilling means 8 comprise a pilot crown 26 and reamer 27. The drilling means 8 may be formed in another manner: in an embodiment, the drilling means 8 comprise a so-called wing reamer, in another words, a drill crown with wings that open.

(22) In the arrangement, the flushing medium flow channel 4 is adapted to bypass the percussion piston 6 of the percussion hammer 5. The advantage of this arrangement is that the flushing of the bottom B of the borehole may be effectively implemented with the use of a separate flushing circuit, while the drilling power of the percussion piston is high due to the large mass and large pneumatic working area of the percussion piston. According to an idea, it may be noted that the advantages of a DTH hammer and RC hammer have been combined.

(23) In the embodiment shown in FIG. 1, the flushing medium flow channel 4 comprises a part 12 which bypasses the percussion piston 6 and which extends in a circular manner around the cylinder 9 of the percussion hammer. Said part 12 of the flow channel is formed by adapting a tubular shell 10 around the cylinder 9. The shell may be formed of steel or similar. In accordance with FIG. 1, the shell 10 adapted outside the cylinder 9 may form part of the outer surface of the percussion hammer 5, but this is not compulsory, however.

(24) The part 12 bypassing the flushing medium flow channel of the percussion piston connects at its top end to an adaptor 14 of the boring pipe, which connects the boring pipe 2 to the percussion hammer 5. The boring pipe adaptor 14 has an adaptor flow channel 15 which is arranged to shift the flushing medium flow channel 4 further from the longitudinal centre axis X of the arrangement, whereby the part 12 of the flow channel may be advantageously connected, in the flow technical sense, to the flushing medium channel in the boring pipe.

(25) The percussion hammer 5 comprises a bottom member 16 which has at least one flushing medium flow channel 17 of the bottom member, which is adapted in flow connection to the part 12 of the flow channel flushing medium, bypassing the percussion piston. In an embodiment, the quantity of flushing medium flow channels 17 is three. The task of the bottom member flushing medium flow channel 17 is to lead the flushing medium from the structures of the percussion hammer 5 to the drilling means 8.

(26) The drilling means 8 of a hole comprise at least one drilling means flushing medium flow channel 18 which leads the flushing medium to the bottom B of the borehole. In an embodiment, the quantity of the drilling means flushing medium flow channels 18 is three.

(27) In the embodiment of FIG. 1, the flow channel 18 opens roughly parallel to the centre axis X to the bottom B of the borehole. This way, efficient flushing is accomplished directly against the bottom B of the borehole. In some other embodiment, the flow channel 18 opens at an angle substantially different in relation to the centre axis, whereby flow in the direction of the hole bottom may be enhanced. In a third embodiment there are a plurality of flow channels 18, directed mutually in different directions.

(28) In the embodiment of the Figure, the flow channel 17 of the bottom member comprises a circular flow groove 19 which is adapted on a cylindrical inner surface of the bottom member 16 and which circulates in the plane of said inner surface, which is at least substantially perpendicular to the longitudinal centre axis X of the arrangement. The width of said circular flow groove 19, that is, the dimension in the direction of the longitudinal centre axis X of the arrangement, is dimensioned wide enough so that the flushing medium flow channel 4 stays open for the entire duration of the boring work regardless of the movement of the drilling means 8. The hole drilling means 8 move by the impact of the percussion piston in the direction of the centre axis X in the manner shown by the arrow M, and additionally the hole drilling means 8 rotate around the centre axis X.

(29) On both sides of the circular flow groove 19, seals 20 (shown in FIG. 2a) are advantageously installed, the purpose of which is the prevent the flushing medium to leak out of the flushing medium channel.

(30) The percussion piston 6 is operated by compressed air which is fed to the cylinder 9 of the percussion hammer from a compressed air flow channel 3. In the embodiment of FIG. 1, the compressed air that operated the percussion piston 6 is removed from the cylinder 9 by an exhaust air channel 21, which comprises a centre opening 22 in the drilling means 8. This is in flow connection to at least one air channel 23 radially passing through the bottom member 16 of the percussion hammer, this channel being in turn in flow connection to the space between the percussion hammer 5 and casing 1. Air exits this space at the top end of the casing 1.

(31) FIG. 2a is a schematic sectional side view of a second arrangement for installing a casing, and FIG. 2b is its cross section A-A. In this embodiment, the flushing medium flow channel is implemented in the same manner as in the embodiment of FIG. 1. Instead, there is a difference in arranging the removal of compressed air. Now, the compressed air that drove the percussion piston 6 is removed by the exhaust air channel 21 which comprises at least one side exhaust air channel 24, led past the drilling means 8 and being in flow connection to the cylinder 9 of the percussion hammer.

(32) The advantage is that there is no need to drill or otherwise machine channels in the drilling means 8 for the exhaust air, which would reduce its solidity.

(33) FIG. 2b shows an embodiment where the side exhaust air channel 24 is formed among splines 28 that transmit a rotating movement to the drilling means 8.

(34) The exhaust air channel 21 further comprises a circular air flow channel 25 which is adapted on the inner surface of the bottom member 16. The circular air flow channel 25 circulates said inner surface in a plane that is at least substantially perpendicular to the longitudinal centre axis X of the arrangement.

(35) The width of said circular flow groove 25, that is, the dimension in the direction of the longitudinal centre axis X of the arrangement, is large enough so that the flow channel 21 stays open for the entire duration of the boring work regardless of the movement of the drilling means 8.

(36) The circular air flow channel 25 is in flow connection to said at least one air exhaust channel 24 and at least one air channel 23 passing through the bottom member 16 of the percussion hammer, this channel being in turn in flow connection to the space between the percussion hammer 5 and casing 1. Air exits said gap in the manner already explained.

(37) FIG. 3a is a schematic sectional side view of a second arrangement for installing a casing, and FIG. 3b a detail thereof sectionally from the side. According to an idea, the part 12 of the flushing medium flow channel, said part bypassing the percussion piston 6, is formed by using a pipe 13 adapted outside the cylinder 9 of the percussion hammer. In the embodiment of FIG. 3a, the is one pipe 13 but there may obviously be more of them.

(38) The advantage is that the flushing medium flow channel 4 may be implemented in a very simple way.

(39) In other respects, the flushing medium flow channel 4 is implemented as in the embodiment of FIG. 1.

(40) The exhaust air channel 21 comprises an air channel 23 formed in the drilling means 8, and a channel leading from it to the bottom member 16 and further through the bottom member.

(41) FIG. 4a is a schematic sectional side view of an arrangement for installing a casing, and FIG. 4b a detail thereof sectionally from the side. In this embodiment, the flushing medium flow channel 4 may be implemented by a part 12 of the flow channel, as in FIG. 3a, this part advantageously being a pipe 13 or a hose. In FIG. 3a, the pipe 13 is connected by its top end to an adaptor 14 of the boring pipe, whereby it rotates with the boring pipe 2. In the embodiments of FIGS. 4a and 4b, the pipe 13 may be connected by its bottom end to at least one collar 30, which is advantageously circular, whereby the pipe 13 cannot rotate with the boring pipe 2. The collar 30 may be connected or fastened to the casing 1 or a drill shoe 31 connected to the casing 1 by means of at least one locking part 32 such as a sleeve. The fastening or locking of the collar 30 may also be implemented by means of locking parts 32 set symmetrically. The locking part 32 may be formed of rubber or another suitable flexible material. The pipe 13 may be fastened to the casing 1 in a fixed and non-rotating manner, whereby it will not rotate with the boring pipe 2. By means of the locking part 32, the collar 30 may be both locked and sealed to the casing 1, whereby it is possible to lead all the flushing medium to the bottom B of the borehole. The arrangement 100 may further comprises one or more seals 38 to prevent water from getting to other structures.

(42) By using a solution where the flushing medium is led past the percussion piston 6 by a non-rotating pipe 13 considerable savings are achieved, because a standard percussion hammer 5 and boring pipe 2 may be used instead of purpose-built ones. In addition, the flushing medium may be supplied by means of a normal pipe 13 and pump. The pipe 13 may also be used, once boring is complete, to inject the cement slurry to the bottom B of the drilled hole to strengthen the drilled hole.

(43) In the embodiments according to FIGS. 4a and 4b, the removal of compressed air may be arranged like in the embodiment shown in FIG. 2a. The percussion piston 6 is operated by compressed air which is fed to the cylinder 9 of the percussion hammer from a compressed air flow channel 3. The compressed air that drove the percussion piston 6 is removed by the exhaust air channel 21 which comprises at least one side exhaust air channel 24, led past the drilling means 8 and being in flow connection to the cylinder 9 of the percussion hammer. The exhaust air channel 21 comprises a circular air flow channel 25 which is adapted on the inner surface of the bottom member 16. The circular air flow channel 25 is in flow connection to said at least one side air exhaust channel 24 and at least one air channel 23 passing through the bottom member 16 of the percussion hammer, this channel being in turn in flow connection to the space between the percussion hammer 5 and casing 1, from which the air exists at the top end of the pipe.

(44) In embodiment according to FIGS. 4a and 4b, the removal of compressed air may also be arranged so that the side exhaust air channel 24 is formed among splines 28 that transmit a rotating motion to the drilling means 8, as was described in the embodiment of FIG. 2b.

(45) FIGS. 5a to 5c are sectional side views of alternative details of a collar 30 of the arrangement of FIGS. 4a and 4b. For reasons of clarity, FIGS. 5a to 5c do not show the exhaust air channel 21, which may be according to the details shown in FIGS. 4a and 4b. In the embodiment of FIG. 5a, the collar 30 may comprise a locking part 32. The collar 30 and locking part 30 may be circular and circulate on the inner surface of the casing 1. The collar 30 connects to the casing 1 or casing shoe 31 connected to the casing. The locking part 32 may be located on the outer surface of the collar 30 against the casing 1, fastening and sealing the collar 30 and preventing its rotation with the pilot crown 26. At least one locking part 32 may be adapted to lock at least one collar 30 to the casing 1 or casing shoe 31 by means of a pressurised flushing medium. The locking part 32 may comprise an open inner part 35, as shown in FIG. 5a, or the inner part may be solid. An open inner part 35 allows the flushing medium to access the inside of the locking part 32. Manufacturing a locking part 32 having an open inner part 35 is easier and more economical. By means of a pressure limit valve 34, the pressure of the flushing medium may be raised to be adequate, and to lock the collar 30 to the casing 1 in a non-rotating fashion. The pressure is advantageously 4 bar. As in FIG. 5a, the pressurised flushing medium may be led from the pipe 13 to the locking part 30 where the locking part 32 is pressurised against the casing. According to an embodiment, the removal of compressed air may be arranged through the splines 28 transmitting a rotating motion. The run of the flushing medium is shown by the arrows F and the removal of compressed air by the arrows R.

(46) According to an embodiment shown in FIG. 5b, the locking and sealing of the collar 30 may be performed by means of the locking part 32, in which the pressurisation may be carried out on a separate pressure line 33 of the locking part. The pressurised substance is brought in according to the arrow S through the pressure line 33 to lock and seal the collar 30 against the casing 1. By means of the seal 20, a leakage gap between the collar 30 and pilot crown 26 may be sealed and the access of water inside the casing prevented. In the embodiment of FIG. 5b, the locking part 32 comprised a closed inner part. FIG. 5c shown an arrangement according to FIG. 5b, where the locking part 32 comprises an open inner part 35.

(47) FIG. 6 is a schematic sectional side view of a detail of an arrangement. To simplify the Figure, there is no casing 1 or casing shoe 31 shown. In accordance with FIGS. 4a and 4b, the flushing medium is brought along the pipe 13 to the collar 30 which is locked non-rotatable to the casing 1 or casing shoe 31. In the arrangement, the percussion hammer 5 comprises a pilot crown 26 with a foot valve 36 or without a foot valve. Pressurised exhaust air R may be brought through a centre opening 22 arranged through the pilot crown 26, and removed through at least one air channel 23 to the space between the percussion hammer 5 and casing 1.

(48) FIG. 8 is a side view of a detail of the collar 30 of an arrangement. FIG. 8 describes an arrangement similar to the one in FIGS. 5a to 5b, but the locking of the collar 30 is arranged in an alternative manner. The pipe 13 may be connected by its bottom end to at least one collar 30. The collar 30 may be connected or fastened to the casing 1 or a casing shoe 31 connected to the casing 1 by means of at least one locking part 32b. The locking part 32b may comprise a mechanical locking, such as a gearing of FIG. 8, between the casing shoe 31 and collar 30. According to an embodiment, the locking part 32b may comprise, on the inner surface of the casing 1 or casing shoe 30, at least one rib, protrusion, or pin fixed by welding, for example. It is similarly possible to form at least one groove on the outer surface of the collar 30 to lock the collar 30 in a non-rotating manner to the rib, protrusion, or pin of the casing 1 or casing shoe 31. The fastening or locking of the collar 30 may also be implemented by means of locking parts 32b set symmetrically.

(49) FIG. 7a is a schematic sectional side view of an arrangement for installing a casing. FIG. 7b is a schematic sectional side view of a detail of the arrangement of FIG. 7a. Differing from FIGS. 1 to 6, the bottom B of the borehole may be flushed by a flushing medium which is led through the percussion piston 6 to the hole drilling means 8 along a flushing medium pipe 39 in the centre opening 22 and further to the bottom B of the borehole along a flushing medium flow channel 18 of the drilling means. In embodiments according to FIGS. 7a and 7b, the removal of compressed air may be arranged through the side exhaust air channel 24, according to FIG. 2a. In an embodiment, the side exhaust air channel 24 is formed among splines 28 that transmit a rotating motion to the drilling means 8, as was described in the embodiments of FIGS. 2b, 4a, 4b, 5a to 5b.

(50) The arrangement 100 may be used according to, for example, the following method:

(51) rotating the boring pipe 2 inside the casing 1,

(52) driving the percussion hammer 5 by compressed air, and

(53) removing released material by flushing the bottom B of the borehole by a flushing medium which is led past the percussion piston 6 of the percussion hammer from the borehole 2 to the hole drilling means 8 and further to the bottom B of the borehole, or by flushing the bottom B of the borehole by a flushing medium which is led through the percussion piston 6 to the hole drilling means 8 and further to the bottom B of the borehole, and the drilling means 8 in the arrangement additionally comprising splines 28 transmitting a rotating motion and by means of which the compressed air that drove the percussion piston 6 is led through the splines 28.

(54) In some cases, features disclosed in this application may be used as such, regardless of other features. On the other hand, when necessary, features disclosed in this application may be combined in order to provide different combinations.

(55) The drawings and related disclosure are only intended to illustrate the inventive idea. It is apparent to a person skilled in the art that the invention is not restricted to the embodiments described above, in which the invention is disclosed through some examples, but various modifications and different applications of the invention are feasible within the inventive idea defined in the accompanying claims.

REFERENCE MARKINGS

(56) 1 casing 2 boring pipe 3 compressed air flow channel 4 flushing medium flow channel 5 percussion hammer 6 percussion piston 8 hole drilling means 9 percussion hammer cylinder 10 shell 11 cylinder wall 12 part of flow channel 13 pipe 14 boring pipe adaptor 15 adaptor flow channel 16 bottom member of percussion hammer 17 bottom member flushing medium flow channel 18 drilling means flushing medium flow channel 19 circular flow groove 20 seal 21 exhaust air channel 22 centre opening 23 air channel 24 side exhaust air channel 25 circular air flow channel 26 pilot crown 27 reamer 28 spline 30 collar 31 casing shoe 32, 32b locking part 33 pressure line 34 pressure limit valve 35 open inner part 36 distributing valve 37 damper 38 seal 39 flushing medium pipe 100 arrangement B bottom of borehole F flushing medium P compressed air R exhaust air X longitudinal centre axis of arrangement