NO313156B1 - Tool for cutting a tube from the inside - Google Patents

Description

The invention relates to a tool for cutting a pipe from the inside, including a housing, means for clamping the housing at a place in the pipe, and a rotary head with a nozzle for sending out a mixture of a carrier fluid and abrasive material as a cutting jet against the pipe.

The scope of the invention is the cutting of pipes, especially metal pipes.

A pile foundation on which an oil platform rests is usually anchored to the seabed and must be cut off when the oil platform is to be dismantled when operations are finished. This type of operation is usually carried out by introducing a tool for radial or diamentral cutting of the pile (or pipework) to the inside of a pile and cutting the pile using a high-pressure abrasive jet.

European patent application EP-A-0063940 describes an abrasive jet cutting tool which can be inserted inside a passage, where the tool comprises a housing, a head which is rotatably mounted relative to the housing and at least one cutting mouth piece connected to a pressurized fluid source and supplied with said pressurized fluid mixed with abrasive or worn particles. The device described in this document includes auxiliary nozzles for displacing the tool using a fluid jet, i.e. by reaction, and it includes an annular expandable collar that allows the device to be placed inside the pipework during the cutting operation.

The device described in European patent EP-A-0063940 is intended for cutting pipes or piles, i.e. for cutting using a fluid jet that is filled with abrasive particles and in a direction that is parallel to the axis of the pipe system in which it is inserted .

To cut pipework radially or diametrically, the tool must be positioned very precisely in the pipework to ensure that it is cut correctly; if the axis of the tool (especially the rotation axis of the tool head) is laterally displaced in relation to the pipe laying axis, then a helical cut is produced after rotation of the head through one revolution (360°), which prevents removal of pipe sections and means that a truly diametrical cut has not been achieved.

The problem thus consists in providing a cutting device with improved positioning.

The problem also consists of providing a cutting device which can be manoeuvred, positioned and removed quickly and as simply as possible within such a pipe arrangement or support piles on the platform.

From GB-2236065, a rotatable tool for cutting pipes with a jet containing abrasive material is known. The tool is arranged on a housing which is inserted into the inside of the pipe and attached to it. The components of the cutting medium in the jet are fed to the tool separately and mixed before being fed to a cutting nozzle. The cutting tool has a radially movable nozzle in a rotary head.

From US-4,529,008 an apparatus for repairing underground pipelines is known. The apparatus includes a housing, which is inserted into the pipeline, and which is provided with expandable, torus-shaped positioning rings.

A particular purpose of the invention is to make it possible to cut pipes, such as piles or piles from the inside, in a way that gives a clean cut.

According to the invention, a tool is therefore proposed as mentioned in the Introduction, characterized by the fact that the means for clamping the housing in the pipe include two inflatable rings mounted on the housing with contact surfaces spaced from each other in the inflated state, and that the nozzle is radially movable stored in the rotary head, which nozzle is assigned to an actuator and a roller, which keeps the nozzle at a distance from the pipe, as the actuator exerts pressure on the nozzle and roller in the direction of the pipe during cutting.

With such a tool, it is possible to cut a pipe from the inside in the desired, precise way.

Further features of the tool are indicated in the independent patent claims.

A tool adapted for cutting mainly vertical pipes is characterized by the fact that the tool is suspended in a lifting body, which lifting body has at least one inflatable clamping ring for fixing the lifting body relative to the pipe. The at least one inflatable clamping ring can advantageously be surrounded by an intermediate ring with a friction surface against the pipe.

The radial ring thickness for the inflatable rings in the inflated state will advantageously be at least twice the radial ring thickness in the deflated state. The invention ensures very accurate positioning of the tool in the pipe, for example with an accuracy of approx. 5 mm to 10 mm, and the inflatable rings can expand or expand greatly as well as contract (radial contraction) during positioning or withdrawal of the tool in/from the pipe.

Several advantages of the invention will be better understood from the following description which refers to the attached drawings which illustrate non-limiting embodiments of a cutting tool according to the invention. Fig. 1 shows a longitudinal section of a cutting tool equipped with a pneumatic lift in accordance with the invention, where the section is in a plane including the common longitudinal axis of symmetry for the device and the pipework to be cut. Fig. 2 and 3 are respective schematic cut-away sections showing the operation of the expandable positioning and lifting rings in a tool according to the invention. Fig. 4 shows a detail of a specific embodiment of a

movable nozzle in accordance with the invention.

Reference is made to fig. 1 where a cutting tool according to the invention comprises a housing 2 of mainly cylindrical shape with an axis 4 which must remain essentially coaxial with the longitudinal axis ZZ through the pipe or pipeline 1 while cutting the pipe 1, which may for example be made of metal. The tool comprises a head 3 which is rotatable in relation to the housing 2. The pipe 1, which can be the foundation of an oil platform support pile, can for example be mounted in an external pillar 19, which can be made of metal and which is attached to the pile with cement 20 between the two pipes 1 and 19. The pipe 19 may or may not be anchored to the seabed.

The cutting tools 2 and 3 are suspended in straps 16 from the lift or hoist 36 which itself can be suspended in straps 15 from the hook of a lifting device (not shown); the unit consisting of the cutting tool and the hoist 36 has been inserted into the pipe 1 via its upper end and has been lowered to the level where the diametrical cut is to be made through the pipe 1 (and possibly through the pipe 19 and through the cement filling (by the action of an abrasive (abrasive ) beam emitted from the nozzle 5 in a radial direction (with respect to the pipes 1, 19) i.e. along an axis XX shown in Fig. 1, the nozzle 5 being rotated about the axis ZZ through the pipe 1 to effect the diamentral cut (by for for example a speed of one revolution of 4 to 6 hours).

In the position shown in fig. 1 is the cutting tool in the cutting position and is fixed and centered in the pipe 1 with two expandable rings 6,7 placed around a cylindrical part or collar 23 (for example of sheet metal) which forms part of the fixed housing 2.

A bearing 34 with a large diameter is arranged at the lower end of the housing 2 so that the head 3 can rotate relative to the housing 2 about the pipe axis ZZ, which is essentially identical to the axis 4 of the housing and/or the head of the cutting tool.

Turning can be carried out by means of a hydraulic motor 28 which is supplied with drive fluid via a flexible hose 29. The motor 28 turns, for example via a coupling, one or more down-gear gears 27 whose last output shaft carries a pinion 26 which is engaged with a ring gear 25 which is rigidly connected to the head 3, so that the head thus turns the axis 4, ZZ.

The head 3 comprises a construction, e.g. a metal construction, which consists of pipe 56 and a metal frame 21 on which an actuator 18 is attached. The actuator can displace the nozzle attached to the end of the tube 43, which forms a delivery channel 44 for the fluid filled with abrasive particles, so that fluid can be supplied to the nozzle.

The channel 44 is angled and comprises a mainly longitudinal part located along the axis 4 and a radial part along the axis XX; the entrance to the pipe 43 and/or the pipeline 44 is connected to a flexible hose 32 whose lower end to the pipe 43. The flexible high-pressure hose 32 can rotate at the same speed as the head 3 due to the rotary coupling 33.

The entrance to the coupling 33 is connected with a flexible feed hose 31 to supply high-pressure fluid filled with wear particles.

At the outer tangential or radial end of the tube 43, near the nozzle 5, a roller 45 is provided which can lie against and roll on the inner surface 40 of the tube 1 and maintain a set gap or distance between the end of the nozzle 5 and the wall, suitable for the operation being performed. The actuator 18 presses the nozzle radially and presses the roller 45 against the inner wall 40 of the pipe.

The actuator 18 can consist of a single-acting hydraulic cylinder with spring or accumulator return; alternatively, and as described below with reference to fig. 4, the actuator can be constituted by a mechanical actuator instead of a hydraulic cylinder, which means that the flexible hydraulic feed hose to the actuator 18 can be omitted.

Expandable positioning rings 6,7 are fed with an expansion fluid through the flexible feed hoses 30 (shown in part). Each expandable ring 6, 7 is fixed between two circular flanges 24 fixed on the outer surface of the collar 23 and which hold the expandable rings 6, 7 in position. The outer surface presses against the inner surface 40 of the pipe 1 during expansion and the rings are deformed under the pressure of fluid injected via the flexible hoses 30.

It can also be seen at the top of fig. 1 that the hoist or lift 36 essentially consists of a tubular body 35 with a hollow inside and three flanges 41, e.g. circular flanges, which form two annular spaces, each of which has an expandable lifting ring 8,9 which can be fed by the same means as the expandable positioning rings 6,7 (expansion limits are not shown).

Advantageously, the expandable lifting rings 8,9 are surrounded by respective cushions 37,38 which have a ring shape, are mainly compact and relatively incompressible, and have external surfaces 39 with a high coefficient of friction against the internal surface of the tube 1, thereby enabling locking of the lift in the tube. When the cutting operation is complete, the lifting device can be used to lift both the cutting tool and the cut pipe to the surface due to the pressure exerted by the lifting rings 8,9 which are expanded, causing the outer surface of the pads 38,37 to lie against it Inner wall of the pipe and allow the cut pipe to be lifted out.

Reference is now made to fig. 2 where the collar 23, which forms an essential part of the frame of the housing of the cutting tool, is reduced in weight by cutouts or windows 28 therein. Expandable positioning rings 6,7 are arranged at its circumference.

Each ring has a toroidal shape and consists essentially of a membrane 10 which is preferably made of an elastomer reinforced with mineral or textile fibers to give it high elasticity, great radial expansion capacity and good elastic memory to make it return to its output -or folded position each time the extended ring is relieved. The membrane forms a sealed cavity 11 provided with an opening or valve 57 which connects the cavity and/or the expandable ring with a hose (30 in Fig. 1) for inflating and relieving the rings 6,7.

Each ring extends around the periphery of the collar 23 between two circular flanges 24 whose height 12 essentially corresponds to the unloaded height (ie in the absence of inflation pressure) of the expandable rings 6,7, which height is very small compared to the non- inflated width 14 of the expandable rings.

Fig. 3 shows the expandable ring 6,7 which has been pressurized and where part of the outer surface of the membrane 10 is in

contact with the inner surface 40 of the tube 1. It can be seen that, due to its radial elasticity, the expandable ring 10 has been deformed under the influence of the fluid injected into the cavity 11 and has contacted and pressed against the inner surface of the tube 1 40. The height 13 or the

radial thickness of the rings 6,7 is large in relation to the relieved height 12 (fig. 2), preferably at least twice the height.

Fig. 4 shows a preferred embodiment of a movable nozzle in a device according to the invention. The nozzle 5 can be held close to the inner surface 40 of the tube 1 by means of the construction shown in this figure; the construction comprises a pipe 43^ whose rear end 434 is connected e.g. to the rotatable flexible hose 32 (fig. 1), so that fluid filled with wear particles is fed in the direction of the arrow 49 to the channel inside the tube 43^.

The central portion of the pipe 43^ comprises a thin pipe 433 attached to the pipe 43^ via its upstream end portion (left in Fig. 4), around which a movable pipe 43£i provided with seals 50, can slide in a bore 55 provided in the tube 43^; where the downstream end of the pipe 43£ (right in Fig. 4) carries the delivery nozzle 5 for fluid filled with wear particles, and is attached to a flange 51 attached in turn to a roller 45 which can lie against the inner surface 40 of the pipe 1 and slowly roll over this as the tool head rotates around the pipe's 1 longitudinal axis. The flange 51 also carries an ultrasound detector 46 which monitors the cut.

The flange 51 also receives the ends of threaded rods 47 which pass through a flange 52 which is fixed relative to the tool head. The other end is connected to a flange 53 which can slide on the fluid delivery tube 43^; a helical pressure spring 48 is placed around the pipe 43 and acts between the fixed flange 52 and the sliding flange 53. It works as follows: the pressure in the fluid filled with abrasive particles tends to press the nozzle against the inner wall 40 of the pipe 1 until the roller makes contact with the wall. This compresses the spring 48 via the flange 51, the rods 47 and the flange 53, and thus causes a return force to act against the nozzle; the tube 43^ is also forced

(right in fig. 4) under the pressure in the vector fluid filled with abrasive particles. The pipe 43^ is held in place by a shoulder which lies against the flange 52.

A system is thus provided which accommodates small deviations from the real coaxiality between the axes through the tool head and the axis through the pipe to be cut, and a device is provided which ensures an essentially constant contact pressure of the roller against the inner wall of the pipe and consequently ensures that the distance between the outlet of the nozzle and the wall to be cut is constant.

As shown in fig. 1, it can be seen that the first and second expandable rings (for positioning and/or lifting) are superimposed, their respective planes of symmetry being essentially parallel to each other (and perpendicular to the axis ZZ).

Claims (6)

1. Tool for cutting a pipe (1) from the inside, including a housing (2 ), means (6,7) for clamping the housing (2) at a place in the pipe (1), and a rotary head (3) with a nozzle (5) for sending out a mixture of a carrier fluid and abrasive material as a jacket jet towards the pipe (1), characterized in that the means for clamping the housing (2) in the pipe (1) include two on the housing (2) mounted, inflatable rings (6,7) with contact surfaces spaced against the pipe (1) in an inflated state, and that the nozzle (5) is radially movable stored in the rotation head (3), which nozzle (5) is assigned a actuator (18;43) and a roller (45), which keeps the nozzle at a distance from the pipe (1), as the actuator (18;43) exerts pressure on the nozzle (5) and the roller (45) in the direction of the pipe (1) under the cutting. 2. Tool according to claim 1, characterized in that each ring (6,7) lies in a respective circumferential groove on the housing (1), which groove has a radial depth (12) at least corresponding to the radial ring thickness (12) in the deflated ring state. 3. Tool according to claim 2, characterized in that the housing (2) includes a tubular structure (23) on the outside of which circumferential, radially directed flanges (24) are arranged which form the aforementioned grooves. 4. Tool according to one of claims 1 to 3, characterized in that the rotation head (3) includes a internal ring gear (25) in driving cooperation with a drive gear (26) which is driven by a motor (28) into the housing (2). 5 . Tool according to one of the preceding claims and adapted for cutting mainly vertical pipes, characterized in that the tool is suspended (16) in a lifting body (36), which lifting body (36) has at least one inflatable clamping ring (8,9) for fixation of the elevator body (36) relative to the tube (1). 6. Tool according to claim 5, characterized in that the at least one inflatable clamping ring (8,9) is surrounded by an intermediate ring (37,38) with a friction surface (39) against the pipe (1).