EP0900319B1 - Process and device for separation of pipes or columns fixed in the ground - Google Patents

Description

The invention relates to an apparatus and a method to separate upright, with your lower End of pipes anchored in the ground, especially of support legs an offshore oil drilling or production platform the preambles of claims 1 and 4, respectively.

Such a method and to carry it out Devices suitable for the process are known from WO 93 / 192 81 and U.S. Patent 1,755,206.

To mine the numerous oil deposits, will for some time not only oil fields accessible from land, but also those under the sea floor or under so-called offshore fields located in other waters drilled. Such holes are in different Depths of water and partly sunk far from the coast. Basically what is training above the water surface concerns the same derrick as on land used, just on one above the water surface arranged conveyor platform. The type of support the production platform on the seabed is partly depending on the water depth. Most offshore oil platforms are formed by large pipes Support legs anchored in the sea floor.

Depending on the nature of the seabed, they are Support legs only embedded in the sea floor, e.g. rammed in and hold due to the friction in the seabed. If if this is not enough, the alternative is to the sunken foot of the support legs underwater concrete or The like to bring in, if necessary, partially the lower end of the pipe in the surrounding seabed emerges and after curing an artificially created forms a foundation anchored in the seabed, to which Anchoring effect the effect of the weight of the concrete accesses that up to the lower part of the respective pipe to a certain amount. The funding platforms get through these measures even in problematic Stability that they withstand the high loads resists in the high seas.

The first of these platforms were in the North Sea commissioned about 20 to 25 years ago; you will be no longer needed since the holes drilled with them Oil fields have been mined. You can't be easy be left standing because they are a danger to the Represent shipping.

There is therefore a need for a method and Devices with which the oil production platforms from the Seas to be eliminated after their useful life can. While removing the superstructure of the platform and the platform itself basically that of the country used oil derricks occur in the in support structures located partly in deep and moving water or platforms on significant problems. The Support legs must also be removed, but may for the reasons mentioned not simply high or dense be cut off below the surface of the sea, but regulations of the relevant authorities require that the support legs are a little below the sea floor be separated.

From DE-PS 671 660 is a device for severing known from pipes embedded in deep boreholes, whose cutting tool by means of a rod in the pipe is let down to the point of separation. The Cutting tool is attached to the inner wall of the pipe and cut it from the inside out.

For cutting support legs of the above This device is not suitable for platforms because the separation point is always in an area of the support legs, the one with seabed, concrete or similar is filled and thus a lowering of the separation point is not possible.

It was therefore tried with diving teams and suitable equipment to submerge and there the support legs by means of an outside around the support leg laid diamond wire driven in its longitudinal direction to cut off. This is because of the large wall thickness the tubes a lengthy and for the diving teams also dangerous procedure.

Furthermore, a device for cutting is from US Pat of the support legs of an off-shore oil drilling or production platform and their segmental removal known. The Device is due to the special structure used there Adjusted support legs. On the one hand, these consist of an outer Jacket tube and on the other hand from an inner tubular Stake. With the jacket pipes, the off-shore oil drilling or production platform first placed on the seabed. For fixing these cladding tubes in the seabed are then let down the tubular piles within the casing pipes and driven into the ocean floor. The length of the Piles are chosen so that after a sufficient hold was reached in the bottom of the sea Pass in the casing tube. The one between the inner pole and the outer casing tube formed for fastening the off-shore oil drilling or production platform on the ocean floor or to attach the casing tube to the pile a grouting material, such as concrete, backfilled.

To move the offshore oil drilling or production platform to separate the casing pipes from the tubular piles, the concrete is first between an ultrasound process crushed the pile and tube and then rinsed. A separator is then used to remove the pile to the top of the tubular pile let down. This separator essentially consists from a clamping device to attach it to the inside of the pile to be able to hold a predetermined position, as well as from a Cutting device to cut the upper segment of the pile to be able to separate. The cutting device has one in the radial direction and thus acting in the direction of the inner wall of the pile Piston / cylinder unit on, over the rotating cutting discs can be placed on the inner wall of the pile.

To ensure that only the pile and not the casing tube is severed, mechanical stops are provided which the Limit the extension movement of the piston / cylinder units, or the stroke of the piston / cylinder unit is adjustable. After the upper segment of the pile from the cutter is severed, this is still from the Clamping device of the separator is held and thus can together with the separator upwards from the casing tube be lifted out. This process is repeated until the tubular pile is removed from the respective casing tube is.

Also in U.S. Patent 4,389,765 for releasing support legs an off-shore oil drilling or production platform from the ocean floor mentioned the use of explosives. The explosions can, however, damage the support legs and therefore require extensive repairs. A use of the This makes the platform at a new location significant delayed.

The object of the invention is a method and an apparatus to create with the pipes of greater length and large diameter like the pillars of offshore oil drilling or production platforms despite the material in the pipes, such as soil or concrete quickly and therefore economically even under the seabed can be separated and also prevented here will that by friction of the cutting tools on the edges of the Separation groove and in the seabed outside the pipe increased wear or even breakage occurs.

This task is in its procedural aspect solved by the subject matter of claim 1.

According to the invention, the complete severing of the pipe due to rising air above the platform signals. This measure prevents the Cutting tools by an intervention in the environment of the cut pipe prematurely wear or even destroyed become.

An embodiment of the Method according to claim 2, in which a cutting unit with a cutting tool on the inner circumference of the pipe brought into effect and the pipe in the circumferential direction progressively cut from the inside out. A cutting process is quick because in this way from the relatively soft structural steel of the pipe thick chips removed and in the narrow circumferential direction extending separation zone a groove with a high Feed and high stock removal rate until cutting of the entire material cross-section can be introduced. Since it is cut from the inside, it plays no matter where the separation point with respect to the seabed is located; the procedure is carried out in its function does not affect the external conditions.

To prevent the weight of the support legs and any other structural parts associated with it to a sagging one in the process of severing located pipe leads what the cutting tool pinch and damage the cutting unit Catching the weight of the pipe expedient according to claim 3, what in a to be described Way by supporting the parts of the support structure happen on adjacent standing legs can.

The task is carried out in its apparatus aspect solved a device according to claim 4, thereby is characterized in that the power drive (34; 134) at least a piston / cylinder unit that can be operated with compressed air comprises and that means are provided that a connection between the working volume of the piston / cylinder unit and the cutting unit (40) and the drilling tool (60) supporting hollow rods (14), as soon as the cutting tools are in their radially outer Extreme position. By this measure is caused to rise through the hollow linkage Air above the platform completely cut through of the pipe signals. Thus the cutting process be stopped immediately afterwards, which prevents that by friction of the cutting tools on the edges of the Trennut and in the seabed outside the pipe increased wear or even breakage of the same occurs.

Preferably, the cutting unit according to claim 2 at least one radially movable, with the help a power drive can be pressed against the inner circumference of the tube cutting tool, its point of attack in a substantially perpendicular to the pipe axis Level is progressively shiftable in the circumferential direction. The cutting tool only after reaching the cutting point extended radially and for cutting the Pipe by finally creating a wall thickness continuous inner circumferential groove against its inner circumference employed.

To speed up the actual separation process, it is advisable to design the device according to Claim 6, wherein the cutting unit several symmetrically comprises cutting tools distributed around the pipe axis, that work simultaneously in the same separation groove.

It will be at the hole to reach the separation point often not possible to be in the pipe Underwater concrete exactly up to the inner circumference of the pipe to bore out. This is especially true if the pipe is no longer completely round. So it stays on the inner wall there may be a layer of concrete in the pipe, which the cutting tools use when they are subsequently used Could endanger activity.

To avoid this, a cleaning device is recommended according to claim 7, the working area of Cutting tools from residues of the adhering material cleans the attack of the cutting tools. The cleaning device can e.g. a brush-like arrangement of Include cleaning elements.

Since the supporting legs of the offshore oil drilling or platforms have significant weights and possibly also from the remaining ones Share the actual platform and the framework-like Struts are burdened, it can happen that Support leg at the point of separation during the separation process axially collapses and the cutting tools get jammed become.

It is therefore proposed according to claim 8 that a support device is provided which supports the weight of the Intercepts pipe during the separation process.

According to one embodiment, the support device can according to claim 9 in a neighboring already separated Pipe usable, about the same length Include support tube, which is in at the lower end the pipe on the seabed or through the underwater concrete formed pipe foundation and on the top End can be connected to the separated tube, which in the described in claim 10 by a hydraulic tensionable cone tension connection can happen. On this way the separated pipe with the neighboring one Platform parts held up so that the tube in which the cutting unit is working, not so heavily loaded is.

Embodiments of the invention are as follows explained with reference to the drawing.

Fig. 1 perspektivisch eine Stützkonstruktion mit davon abgehobener Förderplattform;

Fig. 2 schematisch eine Seitenansicht einer Stützkonstruktion;

Fig. 3 schematisch in Seitenansicht, teilweise geschnitten, eine erfindungsgemäße Vorrichtung mit einer ersten Ausführungsform des Schneidaggregats in einem ein Stützbein bildenden Rohr;

Fig. 4 einen vergrößerten Ausschnitt aus Fig. 3;

Fig. 5 eine alternative Ausführungsform des Schneidaggregats mit linearer Führung der Schneidwerkzeuge;

Fig. 6 und 7 schematische Darstellungen in Betracht kommender Schneidprinzipien;

Fig. 8 schematisch eine Ausführungsform bei der das Schneidaggregat und der Bohrwerkzeugkopf an einem Bohrgestänge angeordnet sind;

Fig. 9 eine Seitenansicht des Bohrwerkzeugkopfes aus Fig. 6 in vergrößertem Maßstab;

Fig. 10 eine Ansicht des Bohrwerkzeugkopfes aus Fig. 9 von unten sowie

Fig. 11 schematisch eine in einem bereits abgeschnittenen Stützbein angebrachte Stützvorrichtung.

The drawing shows:

Figure 1 is a perspective view of a support structure with a lifting platform lifted therefrom;

Fig. 2 schematically shows a side view of a support structure;

Fig. 3 schematically in side view, partially in section, a device according to the invention with a first embodiment of the cutting unit in a tube forming a support leg;

FIG. 4 shows an enlarged detail from FIG. 3;

5 shows an alternative embodiment of the cutting unit with linear guidance of the cutting tools;

Figures 6 and 7 are schematic representations of cutting principles under consideration;

8 schematically shows an embodiment in which the cutting unit and the drilling tool head are arranged on a drill pipe;

FIG. 9 shows a side view of the drilling tool head from FIG. 6 on an enlarged scale; FIG.

Fig. 10 is a view of the drilling tool head of FIG. 9 from below and

11 schematically shows a support device attached in a support leg that has already been cut off.

1 is one of its main components separate oil drilling or production platform 100 shown which includes an actual platform 1, which in the assembled Condition on a support structure designated 2 overall is supported. The whole usually on equipment arranged on platform 1, such as a drilling device, Accommodation etc. is already dismantled and in the Drawing no longer reproduced. For assembly and disassembly oil drilling or production platforms 100 and / or Support structures 2, crane ships 5 are used, the Have cranes 6, their lifting height above sea level Can be 200 m and more. In the phase shown the actual platform 1 hangs after loosening from the Support structure 2 already on the cranes 6.

Of the support structure 2 in Fig. 1 is only that Part located above sea level 10 (Fig. 2) drawn, which can be 30 to 40 m high. The support structure 2 is included as a tower or trestle-like scaffold Support legs 3 and truss-like cross struts 4 trained and by means of her down in the water reaching legs (indicated by dash-dotted lines) 3 anchored under the water surface in the seabed. The Water can be over 100m deep and any leg can 3 a comparable distance into the seabed embedded, e.g. be rammed in. The support legs 3 are so very long. They consist of large tubes 13 of 1 up to 2 m in diameter and considerable wall thicknesses from 30 to 50 mm. The number of support legs 3 depends on the structure of the Support structure 2 dependent.

Fig. 2 illustrates the dismantling situation of a Support structure 2, which is structurally something of Fig. 1st deviates. The upper parts 3 'of the support legs 3 are on the separation point 8 cut off and still belong to the actual platform 1, which is shown in FIG. 1 by the cranes 6 is lifted off the support structure 2. The support structure 2 protrudes above sea level 10 and extends by a depth corresponding to the water depth Route down to the ocean floor 11. The support legs 3 reach deep into the sea floor 11 and can their lower ends by pressed in underwater concrete or the like anchored in the seabed 11 in a foundation-like manner his. When abandoning an oil drilling or production platform 100 is required that the support legs 3 in a distance 7 of a few meters below the sea floor 11 lying separation points 9 from their deep in the seabed 11 reaching lower ends 12 at separation points 9 are separated. During the separation at the separation points 8 no problems due to the good accessibility prepares, the separation points 9 are below the water surface 10 and 11 and within the seabed accordingly difficult to achieve.

Because of this, one is inside each one Tube 13 lowerable and on its inner circumference for Oncoming attack, designated 50 as a whole in FIG. 3 Disconnecting device provided, the one with 40 designated cutting unit, which a drive device 30 is assigned. Seen in the lowering direction Cutting unit 40 is upstream at the lower end of Linkage 14 provided a drilling tool head 60, the Structure and operation described with reference to FIGS. 9 and 10 will be.

In the upper half of Fig. 3, such is on Upper end of the pipe to be separated 13 arranged drive device 30 shown, part of a usual Air lifting and drilling device is down and into that Drives tube 13 into hollow rod 14 reaching into it, in its lower area the cutting unit 40 is rotatably attached, its structure and function continue will be explained below.

A rotary drive 16 can be arranged in the drive device 30 can be used as it drives a drill head an air-lifting drilling device from the prior art is known. So there can be existing drive devices be used, the modifications only if necessary must have. For driving the cutting unit 40 and the drilling tool head 60 that extends Linkage 14 within the pipe to be separated 13 to beyond its upper end, so that it is above the upper end of the tube 13 by means of a turntable 18th by means of a gear wheel attached to the circumference of the linkage can be driven from the outside.

At the upper open end of the linkage 14 is a so-called Flushing head 17 arranged by the drilling operation material loosened at the bottom of an earth hole by the Inner cross section of the linkage 14 in the direction of Arrow 14A after the air lifting process in line 15 is rinsed out. The operation of the flushing head 17 and the air lifting process are state of the art known and will not be explained in more detail here. Below the rinsing head 17 is a designated 19 Rotary connection head arranged above the compressed air for the Air lifting process and another fluid medium (air or a hydraulic fluid) even at high pressures one or more parallel to or in the linkage 14 this extending supply lines 20 and 22 can be introduced is.

Fig. 4 shows an enlarged view of the the lower end of the linkage 14 is rotatably arranged Cutting unit 40 from FIG. 3. Within the linkage 14 are the supply line 20 for compressed air and the supply line 22 for compressed air or a hydraulic fluid shown. The compressed air can be used when drilling on the ground material loosened from the bore by the inside of the Rod-shaped flushing channel 21 in the direction of the arrow 14A are conveyed to the surface. To do that Cutting unit 40 within the pipe 13 to be separated lower the linkage 14 via flange connections 23 (see also FIG. 6) extended downwards in shots, until the cutting unit 40 is at the level of the separation point 9 is lowered. The torque required for machining (Rotary movement) is on the turntable 18 and the linkage 14 introduced into the cutting unit 40, i.e. it will entire linkage 14 together with the cutting unit 40 within of the tube 13 rotated about its axis A. The cutting unit 40 comprises a central part 41, in the interior thereof the flushing channel 21 is formed and its outer dimension in the exemplary embodiment only about a third of the inner diameter of the tube is 13, so that an annular Gap 42 remains.

In the example shown, the cutting unit 40 comprises three symmetrically distributed over the circumference of the linkage 14 swiveling cutting tools 24. Any cutting tool 24 in the exemplary embodiment of FIGS. 3, 4 and 8 its own power drive 34 assigned only to it, that of a fluid-operated piston / cylinder unit can exist. The fluid can be compressed air, its pressure but is limited, or a hydraulic fluid with which higher pressures and thus actuation forces of the power drive 34 can be achieved. The compressed air or the hydraulic fluid are fed via the feed line 22, so that the individual cutting tools 24 synchronously and with the same Forces are operated. It is understood that too there is a separate supply line for each power drive 34 can be. The cutting tools 24 with their power drives are arranged in the annular space 42.

If the power drives 34 are operated with compressed air, so there can be at least one cylinder between the working volumes and the inside of the linkage 14 one in the Drawing not shown be provided connection which is designed such that it is opened when the piston of this power drive 34 in its the extended position of the cutting tool assigned to it 24 corresponding end position. Through this Measure is caused to rise in the linkage 14 Air that is observed, for example, on the flushing head 17 can, the complete severing of the pipe signals. The separation process can then be stopped immediately, which prevents the cutting tools from unnecessary friction on the edges of the separating groove prematurely wear out or even penetrate into the outside of the pipe existing seabed are destroyed.

Each cutting tool 24 consists of an elongated one Base body 25, at one end of which a cutting plate 26 is attached. The inserts 26 are considered to be from Heavy-duty cutting material suitable for existing inserts educated. The base body 25 is on its Cutting plate 26 facing away from an end on the outer circumference of the central part 41 arranged horizontally to form a circle mounted about the axis A tangentiaien pivot pin 28. Between the pivot pin 28 and the insert 26 attacks a link 29 connected to the power drive, by means of which the cutting tool 24 during an upward movement of the handlebar 29 by pivoting around the Swivel pin 28 from a dash-dotted line in FIG. 4 downward transport position 24 'radially can be shifted outward until the insert 26 comes to attack on the inner circumference of the tube 13 and that Tube 13 at the separation point 9 from the inside to the outside Formation of a progressing from the inside out extending in a plane perpendicular to the axis A. Trennut 45 is cut by cutting.

In the embodiment shown in Figs. 3,4 and 8 is the power drive 34 as a piston unit / cylinder unit formed in the space 42 on the outer circumference of the central part fixedly arranged parallel to the axis A. and the piston rod 32 with the handlebar 29 via a on the central part 41 guided slide 33 motionally connected is. During the lowering movement of the cutting unit 40 is the cylinder of the piston / cylinder unit in its fully extended position (below as shown) so that the cutting tool 24 essentially aligned along axis A (position 24 ') and is free of the tube 13. To the cutting plate 26 against to press the inner circumference of the tube 13 is over the Lead 22 of the piston of the piston / cylinder unit after moved up and the base body 25 of the cutting tool 24th pivoted radially outwards. About the pressure of through the supply line 22 supplied compressed air or hydraulic fluid is the contact pressure of the cutting plate 26 to the Inner pipe wall to influence the cutting result adjustable. Once the tube 13 is completely cut the piston is moved down and that Cutting tool 24 pushed back into its starting position 24 ', so that the cutting unit 40 upwards from the separated tube 13 can be pulled out.

The pivoting of the cutting tool 24 to the inner tube wall or the actuation of the piston / cylinder unit can be done in a variety of ways known to those skilled in the art. If there are several supply lines 22, the piston can 32 alternately with pressure in both directions can be applied, the restoring torque can be applied via springs be effected and the like.

As an alternative to radial swiveling around a horizontal one The basic body of the cutting tool can also be linear be moved. 5 is a cutting unit 140 with linear to the axis A of the cutting unit 140 or Tube 13 radial guidance of the base body 125 of the Cutting tool 124 shown, the linear guides are formed in a tool guide body 131 which is arranged at the lower end of a central part 141 which at the upper end a flange 143 for connection to the Linkage 14 has. The basic body 125 of the cutting tools 124 are in radial guide channels 123 of the tool guide body 131 relocatable. In the left half 5 is the cutting tool 124 in the extended, shown in the right half in the retracted state. At the The end of the base body 125 facing the tube axis A is which is articulated and extends one leg 127 of a toggle lever up to the knee joint 133 while the other Leg 128 of the toggle lever starting from the knee joint 133 is articulated centrally near the pipe axis A. On the knee joint 123 of the toggle lever grips one end along the axis A extending joint rod 129, the other end via a pivot pin 132 with the power drive 134 is connected.

In contrast to the embodiment according to FIGS. 3.4 and 8 here is only a piston / cylinder unit as power drive 134 provided that all cutting tools 124 in common drives.

The piston / cylinder unit faces the central part 141 formed pistons 135. The cylinder of the piston / cylinder unit is more surrounding than the piston 135 Sliding cylinder 138 formed, the end plates 138A, 138B on the cylindrical outer circumference 142 of the central part 141 on either side of the radially protruding Piston 135 slide and with piston 135 Form pressure chambers 136, 137 which can be pressurized with compressed air are. Around the base body 125 of the cutting tool 124 in the respective guide channel 123 to the outside to move, compressed air is supplied to the upper pressure chamber 136, so that the sliding cylinder 138 is pushed upward is and the knee joints 127.128 over that with the sliding cylinder 138 connected handlebars 129 are stretched, so that the cutting inserts 126 of the cutting tools 124 linear against the inner circumference of the pipe to be separated 13 be employed.

At the top of the upper air chamber 136 is a extending to the interior of the linkage 114, Channel 136 'may be provided, the mouth of which in the upper Pressure chamber 136 is released when the sliding cylinder 138 in its upper, extended position of the cutting tools 124 is the limit position. Air rising inside the rod 114 signals then again the termination of the separation process.

With the arrangement shown in Fig. 5, dimensioned so is that approaching that on the left reproduced stretched position of the toggle lever 127,128 at Attack of the cutting insert 126 in the wall of the tube 13 takes place, can easily a high contact pressure the cutting inserts 126 against the tube 13 and one appropriate chip thickness can be achieved at the separation point 9. Around the cutting unit 140 with the cutting tools retracted Lower 124 into tube 13 and lift it up the lower pressure chamber 137 compressed air or hydraulic fluid supplied so that due to the Movement of the sliding cylinder 134 down the handlebars 129 and thus the knee 123 of the knee joint downwards are moved and thereby the cutting tools 124 in the Drive guide channels 123 inwards, as on the right 5 shown.

6 and 7 is the operation of the cutting units more depicted in principle.

6 corresponds to the previously described embodiment. A rotatable in the tube 13 about the axis A. Cutting unit 40, 140 has cutting inserts 26, 126, which can be moved radially out of the cutting unit 40, 140 are and a rotational movement along the inner circumference of the Run tube 13 only around axis A. The cutting inserts 26.126 act like internal parting steels.

7 shows an alternative embodiment, in which a cutting unit 240 about the axis A is rotatable, but no radially extendable cutting inserts, but rotatable on a tool carrier 231 Cutting tools 224 carries that on the edge of the cutting unit are rotatable about axes B parallel to axis A and come to attack on the inner circumference of the tube 13. The cutting tools 224 therefore rotate both around the Axis A as well as about axis B. Disk milling cutter to be formed.

In Fig. 8, the separator 50 is a whole with a cutting unit 40 rotatable on the linkage 14 3 and 4 reproduced. The linkage is there made up of several shots at coupling points 14 '' Rod members 14 'and extends from into the top of the tube 13, of which only the one in FIG top part is shown. To the linkage 14 within the To fix tube 13 radially are at axial intervals mutually stabilizers 35 arranged against the inner wall of the tube 13 and in which the linkage 14 is stored and can rotate freely. Between two Stabilizers 35 is a switching valve 47 in linkage 14 installed with which, for example, the reversal of the direction Radial pivoting movement of the cutting tools 24 controlled can be. As known from the drilling operation, as lowest bar is a stabilizing bar or drill collar 49 be installed in the linkage 14. At the top End of the linkage 14 is a free coupling point 14 '' ' for disengaging further rod elements 14 'or the drive device 30 (Fig. 3) provided. At the bottom of the linkage 14, the cutting unit 40 is arranged.

With the cutting units 40 of FIGS. 3 and 4 and 140 5 is the respective predetermined separation point 9 only attainable when the tube 13 is free there. In in many cases the tube 13 is up to a certain one Height filled with seabed or underwater concrete that can be located above the separation point 9.

Therefore, 40 and 140 is below the cutting units a drilling tool head 60 attached underneath is provided, 3, 4 and 8 below the cutting unit there 40 recognizable and enlarged in FIGS. 9 and 10 is reproduced.

The task of the drilling tool head 60 is in the pipe material located within the lower section of the pipe 13 to be cut out to below the separation point 9, so that the cutting unit 40 to the intended Separation point 9 can reach. To do that through the drilling tool head 40 material to be drilled away can, this is brief with reference to Figures 3 and 4 indicated air lifting method used. When drilling out of the tube 13, the device acts like a conventional one Earth auger; the cutting unit 40 is in this case when retracted Cutting tools inoperative. It is only after completed drilling started.

The tubes 13 are thus separated using existing drilling units and technology, whereby only between the drill head 60 and the linkage 14 use the cutting unit 40 and with supply lines is to be provided.

The one shown in Fig. 9, an approximately circular Outlined drill bit head 60 is over the top Flange 43 to one at the lower end of the cutting unit 40 provided counter flange. At the Bottom of the drilling tool head 60 are, like that Bottom view in Fig. 10 shows fixed, with hard metal occupied drill body 46 or roller chisel arranged, with which the one to be separated in the inner cross section of the Tube 13 located underwater concrete are drilled away can. The suction opening 48 is used for the air lifting method and is with the inner cross section of the linkage 14 (not shown) connected.

When drilling out the tube 13 can on the inner circumference of the pipe 13 adhering concrete layers remain, the cutting plates 26, 126 of the cutting tools 24, 124 when positioning against the inner circumference of the tube 13 can damage or destroy. To avoid this can be a cleaning device on the drilling tool head 60 with brush or scratch-like extensions that can be pushed out radially Cleaning elements 44 may be provided, by means of which adhering concrete removed to the metal of the tube 13 is brought into effect before the cutting tools 24, 124 become.

11 shows a support device 70, with which the load on a pipe 13 just to be separated Weight of the tube 13 itself, neighboring already cut pipes 13 and thus still remaining Superstructures of the platform can be intercepted. Shown is a support leg that is currently being worked on neighboring, already separated at the separation point 9 Tube 13. In the separated tube 13 after the Cutting unit including rods or pulled out with the rope an additional support tube 80 was slightly smaller Lowered diameter, the length of the length of the Tube 13 surpasses and consequently over the upper End of the tube 13 and the residues 63 still connected to it survives the platform. The pipe 13 is below with underwater concrete 61 up to an upper boundary surface 65 filled. This sits on this boundary surface 65 Support tube 80 with its lower end 80 '. Just below of the upper end 80 ″ of the support tube 80 is a conical tension connection 62 in the space between the support tube 60 and the inner circumference of the tube 13 arranged hydraulically is jammed. On the protruding from the tube 13 Part of the support tube 80 is a hydraulic one Lift cylinder 64 provided on the rest 63 of the platform attacks. When the lifting device 64 is actuated the rest 63 pulled up on the support tube 80. Doing so the upper part of the tube 13 taken away. Between the Attachment of the lifting cylinder 64 and the top of the Remaining 63 of the platform is a defined distance, that during the entire separation process of the others Support legs should be maintained. At the separation point 9 this creates a gap. Via the cone tension connection 62 is now a permanent tension between the support tube and the tube 13 achieved so that it on the constant maintenance of the pressure in the lifting cylinder 64 no longer arrives. The pipe to be cut off 13 neighboring pipes that have already been cut off and the pipes with them connected remnants 63 of the platform will be this way held up securely so that not the whole structure the point of separation 9 of the tube 13 just machined collapses. Without the support device it could be Separation process of the tube 13 being machined into one Clamp the cutting inserts 26, 126 in the at the separation point 9 formed inner circumferential groove 45 (Fig. 4) come if the remaining wall cross section of the tube 13 the load is no longer up to the task.

Claims (10)

1. Process for cutting off upright tubes (13) of large length and large diameter having their lower ends anchored in the ground, in particular supporting legs (3) of an offshore oil drilling or handling platform (100), in which a cutting assembly (40, 140, 240) is lowered through the upper end of the tube (13) to be cut off, into the tube (13) as far as a cutting point (9), which assembly acts against the inside of the tube (13) from inside, driven by compressed air and advancing over the periphery, material present in the tube (13) such as sea bed material or concrete in which the tube (13) can be embedded for improved anchoring age in the ground (11) being drilled out as far as below the cutting point (9) on lowering of the cutting assembly from above through the tube (13),
   characterised in that
   the attainment of complete cutting through of the tube by the cutting assembly (40, 140, 240) and thereby the complete cutting through of the tube (13) is signalled by compressed air rising through a hollow rod (14) carrying the cutting assembly (40, 140, 240), in particular compressed air for the cutting assembly (40, 140, 240).
2. Process according to Claim 1, characterised in that the cutting assembly (40, 140, 240) cuts through the tube (13) by chip-removing machining.
3. Process according to one of Claims 1 or 2, characterised in that the weight of the tube (13) and any components (63) which may be connected to it is taken during the cutting off process.
4. Equipment for cutting off upright tubes (13) of large length and large diameter having their lower ends anchored in the ground, in particular supporting legs (3) of an offshore oil drilling or handling platform (100),

   with a power drive (34; 134), and

   with a cutting assembly (40, 140, 240) which can be lowered through the upper end of the tube to be cut off, into the latter as far as a cutting point (9) and which comes into action progressively in a circumferential direction in an axially narrow cutting zone (45) on the inside of the tube (13) and cuts through the tube (13) at the cutting point (9), a rotatably driven drilling tool head (60) being mounted underneath the cutting assembly (40), by means of which material present in the lower part of the tube (13) such as sea bed material or concrete (61) or the like, with which the tube (13) is embedded for improved anchorage in the ground (11), can be drilled out from the inside of the tube (13) to a depth so that the cutting assembly (40, 140, 240) can be brought into position at the given cutting point (9),

   characterised in that
   the power drive (34; 134) includes at least one piston/cylinder unit driven by compressed air and that means are provided which effect a connection between the working volumes of the piston/cylinder unit and a hollow rod (14) carrying the cutting assembly (40) and the drilling tool (60) as soon as the cutting tools (24; 124; 224) are present in their radially outward extreme position.
5. Equipment according to Claim 4, characterised in that the cutting assembly (48, 140, 240) includes at least one radially movable machining cutting tool (24; 124; 224) which can be pressed against the inside of the tube (13) with the aid of a power drive, and of which the point of the engagement is progressively displaceable in a circumferential direction in a plane substantially perpendicular to the axis (A) of the tube.
6. Equipment according to Claim 5, characterised in that the cutting assembly (40, 140, 240) has a number of cutting tools (24; 124; 224) distributed symmetrically about the axis (A) of the tube.
7. Equipment according to one of Claims 4 to 6, characterised in that the cutting assembly (40) has associated with it a cleaning device (44) cleaning off adhering material from a ring-shaped region at the cutting point (9) up to the metal of the tube (13).
8. Equipment according to one of Claims 4 to 7, characterised in that a supporting device is provided, which takes the weight of the tube (13), and of any parts (63) which maybe connected to it, during the cutting off process.
9. Equipment according to Claim 8, characterised in that the supporting device comprises a supporting tube (80) which can be introduced into an adjacent already cut off tube (13) and having approximately the same length, and which has its lower end (80') placed on the ground or the tube base and can be connected in the region of its upper end (80") by a ram (64) to the cut off tube (13) or structural parts (63) connected to it.
10. Equipment according to Claim 9, characterised in that a hydraulically actuated cone clamping connection (62) is provided between the outer surface of the supporting tube (80) and the inner surface of the tube (13).

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