NO20210456A1

NO20210456A1 - Rotating pipe cutter

Info

Publication number: NO20210456A1
Application number: NO20210456A
Authority: NO
Inventors: Svein A Gjølmesli
Original assignee: Sapeg As
Priority date: 2021-04-14
Filing date: 2021-04-14
Publication date: 2022-10-17
Also published as: NO347029B1

Description

Title : Rotating pipe cutter

FIELD OF THE INVENTION

The invention relates to devices for cutting of pipes or other elongated tubular bodies, more particularly to devices for cutting pipes internally from within the bore of the pipe.

BACKGROUND OF THE INVENTION

Elongated tubular bodies must sometimes be cut. In certain situations, the outside surface of the tubular body is inaccessible and thus not available for cutting. Nonlimiting examples of such tubular bodies include for example a buried or submerged pipe, in particular oil well pipes or casings. When the outside of a tubular body is inaccessible the pipe must be cut internally. In the oil and gas industry it is sometimes advantageous to internally cut a pipe so that a freed pipe section can be removed from a well and reused. Other reasons and applications for internally cutting an elongated tubular body will be apparent to one skilled in the art.

One example of a prior art solution for internally cutting pipes is to use an explosive charge to break the pipe wall. The use of explosive charges has obvious disadvantages in terms of effectiveness and safety, particularly in an environment exposed to volatile petroleum products.

Another prior art solution involves the use a rotating cutting device that is inserted and advanced along, or lowered into the pipe. Known rotary cutting devices utilize either a spring mechanism or hydraulic actuators to extend the cutting teeth via a conical mandrel.

Particular prior art includes:

US 1,772,710 which teaches a cutting device where cutting teeth are forced radially outward by fluid pressure from a well.

US 2017/0328159 which teaches a cutting device where cutting teeth are forced radially outward by a hydraulic or electrical actuator.

US 1529848 which describes a solution where cutter elements are extended by a conical sleeve . However, the principle of movement of the conical sleeve here is based on the use of hydraulic pressure.

US1643709 which describes a similar solution where a conical mandrel is used which drives the cutter elements outward while rotating. Here, however, the movement of the conical mandrel through one is achieved via a reciprocating actuator.

US1643572 which describes another variant where a conical mandrel is used to move the cutter elements out while rotating. This solution is based on pulling this the mandrel upwards.

US2112026 which describes a solution using a conical mandrel that is driven longitudinally through rotation and which drives the cutter elements outwards at the same time as it is rotated. It also describes one rotating head part.

US2208011 which describes a solution using a conical mandrel that is driven longitudinally through rotation and which drives the cutter elements outwards at the same time as it is rotated.

Known arrangements have disadvantages, however. Springs often do not provide sufficient force to enable the teeth to cut through thick or hardened steel.

Hydraulic arrangements are complicated, require a separate hydraulic system, and are prone to failure. A potential leak from a hydraulic line is also an environmental hazard, particularly in the case of offshore applications.

There is a need therefore for an improved cutting device for internally cutting a tubular body such a pipe that avoids the problems and deficiencies of prior art solutions.

SUMMARY OF THE INVENTION

The present invention provides a cutting device for internally cutting an elongated tubular body such as a pipe, in particular for cutting a steel pipe such as an oil well pipe or casing. The device according to the invention is arranged to be connected to the end of a rotational source, for example a downhole motor. Downhole motors exist in different types, for example electric as well as hydraulic, and for different purposes. An example is the so-called PDM (positive displacement motor) used for rotation of a drill bit, also called a mud motor. Other types are downhole motors are supplied by electric power, and are typically used in connection with a well tractor, with the purpose of driving various rotary tools in the well. (a well tractor, also a generally known device in the art, is a device that moves up/down inside the pipe, bringing along various tools like a downhole motor, can fix itself to the pipe and hold against rotation and axial motion). In certain situations the drill string can function as a rotational source.

The device of the present invention comprises a non-rotating outer sleeve that connects to a non-rotating portion of the rotational source. A rotatable, at least partially threaded axle is connected to the rotating part of the rotational source and passes through the bore of the non-rotating sleeve. At the opposite end of the nonrotating sleeve is a rotatable, essentially hollow rotator member with a central bore connected to the threaded axle. Rotation of the rotating part (for example a shaft) of the rotational source thus causes rotation of the threaded axle and thus rotation of the rotator member.

The rotator member comprises one or more extendable cutting teeth. In one embodiment the teeth are contained in a modular carrier unit having a central bore affixed to the rotator. The cutting teeth have an outer cutting tip, preferably of a hardened material such as cemented tungsten carbide, and a lower end. The cutting teeth extend through an opening that leads from the internal bore of the rotator (or carrier unit) and through the wall of the rotator (or carrier unit). When extended, the cutting tip of the teeth will engage the inner wall of the tubal member to be cut. As the rotator/carrier unit rotates, the teeth will thus rotate. When extended with sufficient force, the rotating teeth will cut the pipe. The means by which the cutting teeth are extended is described as follows:

Arranged within the non-rotating sleeve is a longitudinally translatable body with a sloped surface, with a relatively narrower portion at a front end, and widening to a relatively wider portion that is distal to the front end. The translatable body is arranged such that as the body moves in a longitudinal direction, the narrower portion encounters the cutting teeth first, allowing the sloping surface of the translatable body to press the teeth outward as the translatable body continues to move longitudinally. In one embodiment the translatable/sloped body is a cone shaped body, with the narrow end of the cone arranged in the direction of rotator/ carrier unit, and the wide end of the cone arranged in the direction of the rotational source. In another embodiment, the translatable/sloped body has a cone-shaped potion at the front end, and which abruptly or gradually tapers to a narrower portion that is distal to the widest portion of the cone-shaped portion. One aspect of this second embodiment of the translatable body (which tapers gradually) resembles a forward facing cone connected to a rearward facing cone. In another aspect of this second embodiment of the translatable body (which tapers abruptly), a cross section of the translatable/sloped body has a shape resembling an arrowhead.

The translatable/sloped body has a central, at least partially threaded bore, which is arranged to engage the threads of the threaded axle. The translatable/sloped body is movable longitudinally in relation to the non-rotating sleeve, but has rotationrestraining means that prevent the translatable/sloped body from rotating in relation to the non-rotation sleeve, for example a tab or guide block that travels in a slot or groove in the non-rotating member.

When the rotational source causes the threaded axle to rotate in a first direction, the threads of the translatable/sloped body will travel along the threads of the axle, thus drawing the translatable/sloped body in the direction of the rotator member/carrier unit. The sloped surface of the translatable/sloped body will press against the lower end of the cutting teeth as the sloped surface advances, pressing the teeth outward and pressing the cutting tip of the teeth into cutting engagement with the internal wall of the pipe.

Some rotational sources are able to rotate in two directions. With a rotational source of this type the translatable/sloped body is preferably the cone-shaped embodiment. When the rotational source is rotated in the opposite, second direction the cone will retreat away from the rotator member/carrier unit, allowing the teeth to retract out of cutting engagement with the internal wall of the pipe. In one aspect the teeth are connected to a spring-loaded device that forces the teeth back down into the rotator/carrier member as the cone retreats. Some rotational sources rotate in only one direction, however. With rotational sources of this type the translatable/sloped body is preferably an embodiment that tapers to a narrower portion distal to the widest portion. In this aspect, the rotation of the rotational source advances the translatable/sloped body in a forward direction, similar to the cone-shaped embodiment. Rather than reversing direction to reattract the cutting teeth, however, the translatable body is advanced further forward past the widest portion. As the translatable body narrows, the cutting teeth are allowed to retract as described above.

According to yet another aspect, the cutting device of the invention has centralizing means to center the device within the tubular body to be cut. Such means, known to one skilled in the art, include bow springs, leaf springs, spacers and the like.

In use, the cutting device of the invention will be connected to the end of the rotational source. The rotational source will be inserted in and advanced along the interior of the pipe by known means to a desired cutting location. The rotating shaft of the rotational source is caused to rotate in the first direction, whereby the sloped surface of the translatable body will press the cutting teeth into cutting engagement with the interior wall of the pipe.

An operator, knowing the length of the cutting teeth, the internal diameter of the pipe, the rpm of the rotational source and the pitch of the threads can precisely control the cutting device to cut through a pipe wall of known thickness. The operator may also be able to judge the progress and completion of a cutting operation by the torque of the rotational source. According to one aspect, the extension of the cutting teeth, and hence the progress of a cutting operation, is a function of the total number of rotations according to the formula:

e=time(mins)*rpm*g

Where g is a gearing ratio defined by the pitch (p) of the thread between threaded axle and cone (in mm/turn) and the angle of the cone (alfa), so that

g= p*tan(alfa).

The operator will thus know how long time it takes before the cutting teeth are through the wall of the tubular body to be cut. If the rotational source reports torque or power back to the operator, such data can also be used to control the cutting device.

According to one aspect, the cutting device of the invention comprises a fail-safe in the event that the operator forgets to stop the rotation in time. In one embodiment the fail-safe comprises the threads of the axle having a only a specified length whereby the translatable body will only extend the cutting teeth a specific distance. The threads of the translatable body will thus unwind from the threads of the axle after it advances a specific distance and move no further. A spring in the rotator member is arranged to push back against the translatable body so that the threads of the translatable body will reengage the threads of the axle when the operator later reverses the rotation of the rotational source allowing the threads of the translatable body to re-enter the threads of the axle and move back.

According to one aspect, the cutting teeth are arranged in a modular carrier unit connected to the rotator. The modular carrier unit can be removed and replaced, for example to provide cutting teeth of various length and configuration to be used with the device, or to permit simple replacement of the carrier unit when the teeth become worn.

The device according to the invention, according to one aspect comprises:

● a non-rotating sleeve,

● a rotatable, essentially hollow rotator arranged at an end of the nonrotating sleeve,

● a rotatable, at least partly threaded axle with a threaded portion, the axle connected at one end to the rotator and at an opposite end to a rotational source,

● one or more radially-extendable cutting teeth disposed within or in connection with the rotator, the cutting teeth having an outer cutting tip and a lower end,

● a longitudinally translatable body having a sloped surface arranged within the non-rotating sleeve, the translatable body having a bore with threaded portion, the threads of which are arranged to engage the threaded portion of the axle , whereby rotation of the axle in a first direction causes the translatable body to move in a longitudinal direction into engagement between the sloped surface and the lower end or ends of the one or more cutting teeth,

● whereby longitudinal movement of the translatable body causes the lower end or ends of the cutting teeth to be pressed radially outward by the sloped surface, forcing cutting tip or tips into cutting engagement with the tubular body.

Other aspects of the invention are described in detail below and in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to the following figures, wherein:

Figs 1 and 2A, B, C are perspective and cross-sectional views respectively, illustrating the principle of the invention.

Fig. 3 is a perspective view of an embodiment of the invention.

Fig 4 is a cross-sectional side view of an embodiment of the invention.

Fig. 5 is a cross-sectional perspective view of an embodiment of the invention.

Fig. 6 is an exploded view showing the components of an embodiment of the invention.

Fig. 7 is a perspective, cut-away view of an end portion of a rotational source.

Fig. 8 is a perspective, cut away view showing the non-rotating components of an embodiment of the invention.

Fig 9 is a perspective, cut away view showing the rotating components of an embodiment of the invention.

Fig 10 is a perspective view of a cone-shaped embodiment of a translatable/sloped body of an embodiment of the invention.

Fig 11 is an exploded view of Fig 10.

Fig 12 is a perspective view of a modular carrier unit according to an embodiment of the invention.

Fig 13 is an exploded view of Fig 12.

Fig 14 is a detailed perspective, cut away view of a rotator member of an embodiment of the invention

Fig 15 A-D are cross sectional views and an alternative embodiment of the translatable/sloped body showing the body advancing progressively forward

DETAILED DESCRIPTION OF THE INVENTION

Figs 1 and 2 illustrate the principle of operation of the cutting device 10 of the invention. Cutting device 10 is shown inserted in an elongated tubular body to be cut, here illustrated as a pipe 12. The device comprises a non-rotating sleeve 14, to the forward end of which is rotatably connected to or arranged against a hollow rotator 16. A rotatable axle 18 passes through the central bore of sleeve 14 and is connected to rotator 16. Axle 18 has a threaded portion 20. Arranged within rotator 16 are one or more radially extendable cutting teeth 22. Cutting teeth 22 have a cutting tip 24 and a lower end 26. Arranged within non-rotating sleeve 14 is a longitudinally translatable body 28 having a sloped surface 30. Translatable body 28 has a bore with a threaded portion 32 arranged to engage with threaded portion 20 of axle 18.

Figs 2 A, B and C illustrate the principle of operation of the cutting device 10 of the invention. Fig 2A shows cutting teeth 22 in a retracted position. When axle 18 is caused to rotate in a first direction 34 the threaded portion 32 of translatable body 28 will advance forward along threaded portion 20 of axle 18, as shown in Fig. 2 B. Translatable body 28 has rotation-inhibiting means to prevent the body from rotating in relation to sleeve 14, here illustrated as a tab or guide block 36 that travels in a slot or groove 38 of sleeve 14. Slot or groove 38 can be covered by a slot cover 39. As shown, the lower end 26 of cutting teeth 22 have been pressed outward by sloped surface 30 such that cutting tip 24 is in cutting engagement with the interior wall of pipe 12.

Fig 2C shows translatable body 28 having advanced further forward into the hollow interior of rotator 16 such that cutting teeth 22 have fully cut through pipe 12.

A more detailed embodiment of cutting device 10 will now be described with reference to Figs 3-14. Figs 3, 4 and 5 show non-rotating sleeve 14 connected to a rotational source 40. A rotational source is a device that comprises a rotating part such as a rotating shaft, used to power various tools such a drill bit and the like. At the end of non-rotating sleeve 14 rotator 16 is rotatably arranged. Centralizing means are attached to sleeve 14 and rotator 16, such as a leaf spring or bow spring 44. Other centralizing means are also possible to employ. In the embodiment shown, the cutting teeth 22 are arranged in a modular carrier unit 46 removably connected to rotator 16. In order to connect axle 18 to various rotational sources 40, the connection is provided by an adapter 48. Longitudinally translatable body 28 is shown in Figs 4 and 5 arranged inside non-rotating sleeve 14. Fig 6 is an exploded view showing the respective arrangement of the components of the cutting device of the invention.

Fig 7 illustrates an end portion of a rotational source 40. The end portion comprises a non-rotating outer part 50 and a rotating inner part, such as a rotating shaft 52. The non-rotating sleeve of cutting device 10 is rigidly connected to outer part 50, while axle 18 is connected to rotating shaft 52, for example via adapter 48.

Fig. 8 illustrates the non-rotating components of the device and rotational source. As shown, non-rotating sleeve 14 is connected to non-rotating outer part 50 of the rotational source. Translatable body 28 is movable in a longitudinal direction, but prevented from rotating by guide blocks 36 (more readily seen in Fig 10) that travel in slots or grooves 38.

Fig 9 illustrates the rotatable components of the device of the invention. Axle 18 is connected to rotational source shaft 52 by adapter 48. Axle 18 is connected to rotator 16, to which is connected carrier unit 46.

Figs 10 and 11 are detailed views of one embodiment of translatable body 28, in the shape of a cone 56. Cone 56 has a narrower forward end 58, and a distal widest end 60. In one aspect, bore with threaded portion 32 comprises a threaded bushing 62 insertable in the narrow end 58.

Figs 12 and 13 are detailed views of an embodiment of carrier unit 46. Carrier unit 46 comprises a carrier body 64 having guide slots 66 arranged for accepting cutting teeth 22. A disc 68 and carrier lid 70 close the carrier unit 46 with cutting teeth 22 outwardly movable in guide slots 66. A torsional spring 72 is connected between teeth 22 and disc 68, the torsional spring arranged to exert a force biasing teeth towards the interior of the carrier unit when the teeth are extended. As shown, an arm of torsional spring 72 presses against a pin 74 connected to teeth 22.

Fig 14 illustrates an aspect of an embodiment of the invention useful for example with a rotational source that may rotate in two directions. In this embodiment, the translatable body28 is a cone shaped body 56. In this embodiment, the rotational source advances the translatable body by rotating in a first direction. The advancing cone-shaped body presses cutting teeth 22 into cutting engagement with the pipe to be cut. In order to retract the teeth, the operator reverses the direction of the rotational source. As a failsafe, the threaded portion 20 of axle 18 is of limited length in order to prevent over extension of the cutting teeth. In this embodiment, a spring 76 at the end of rotator 16 presses cone 56 back towards the threaded portion of axle 18, so that the threaded portion 32 of the cone can reengage the threaded portion 20 of the axle. As the cone retreats, torsional springs 72 force teeth 22 back into the cutting device.

Fig 15 illustrates another embodiment of the cutting device, useful with rotational sources that can only rotate in one direction. With rotational sources of this type, the operator cannot reverse direction in order to retract the cutting teeth. In this event, a forwardly-only movable translatable body 78 can have a shape which allows the teeth to retract as the translatable body moves further forward. As shown in Fig 15, one embodiment of forwardly-only movable translatable body 78 has a cone shaped portion 80 at a forward end of the body with a narrow end (79) sloping to a widest portion (81), which transitions to an tapering portion 82, which may be an abruptly tapering portion, immediately distal to the widest portion of the cone shaped portion. As body 78 moves forward, the cone-shaped portion 80 will press up on the cutting teeth as described below, and as shown in Figs 15 A, B and C. As the body 78 advances further forward, teeth 22 will be retracted into the tapering portion 82 as illustrated in Fig 15 D.

LIST OF REFERNCE NUMBERS

10 Cutting device

12 Pipe

14 Non-rotating sleeve

16 Rotator

18 Axle

20 Threaded portion

22 Cutting teeth

24 Cutting tip

26 lower end

28 Translatable body having sloped surface

30 Sloped surface

32 Bore with threaded portion

34 First direction

36 Tab or guide block

38 Slot or groove

39 Slot cover

40 Rotational source

42 Leaf spring

44 Bow spring

46 Carrier unit

48 Adapter

50 Non-rotating part

52 Rotating shaft

54 Spring

56 Cone

58 Narrow end

60 Widest part

62 Bushing

64 Carrier body

66 Guide slot

68 Disc

70 Carrier lid

72 Torsion spring

74 Pin

76 Spring

78 Forward-only movable body 80 Cone-shaped portion

81 Widest portion

82 taper

Claims

1. A device (10) for internally cutting an elongated tubular body (12), the device comprising:

a. a non-rotating sleeve (14),

b. a rotatable, essentially hollow rotator (16) arranged at an end of the non-rotating sleeve (14),

c. a rotatable, at least partly threaded axle (18) with a threaded portion (20), the axle connected at one end to the rotator (16) and at an opposite end to a rotational source (52),

d. one or more radially-extendable cutting teeth (22) disposed within or in connection with the rotator (16), the cutting teeth having an outer cutting tip (24) and a lower end (26),

e. a longitudinally translatable body (28) having a sloped surface (30) arranged within the non-rotating sleeve (14), the translatable body having a bore with threaded portion (32), the threads of which are arranged to engage the threaded portion (20) of the axle (18), whereby rotation of the axle in a first direction (34) causes the translatable body to move in a longitudinal direction into engagement between the sloped surface (30) and the lower end or ends ( 26) of the one or more cutting teeth (22),

f. whereby longitudinal movement of the translatable body causes the lower end or ends (26) to be pressed radially outward by the sloped surface (30), forcing cutting tip or tips (24) into cutting engagement with the tubular body (12).

2. A device according to claim 1, wherein the cutting teeth (22) are arranged in a modular carrier unit (46) removably connected to the rotator (16).

3. A device according to one of the preceding claims, wherein the cutting teeth (22) are biased in an inward direction by a spring (72).

4. A device according to one of the preceding claims, wherein the longitudinally translatable body (28) is in the shape of a cone.

5. A device according to one of claim 1-3, wherein the longitudinally translatable body (28) has a forward cone-shaped portion (80) with a narrow end (79), sloping to a widest portion (81), with a tapering portion (82) immediately distal to the widest portion (81).

6. A device according to one of the preceding claims further comprising centralizing means (42,44).

7. A device according to one of the preceding claims further comprising a replaceable adapter (48) for connecting to the axle (18) to various rotational sources.

8. A device according to one of the preceding claims wherein the rotational source is a downhole motor.

9. A method for internally cutting an elongated tubular body, comprising the steps of:

a. connecting a device according to one of claims 1-8 to a rotation source,

b. inserting the device into the interior of the tubular body,

c. advancing the device to a cutting position,

d. causing the rotational source to rotate the axle, thereby forcing cutting teeth into cutting engagement with the interior wall of the tubular body,

e. controlling the progress of a cutting operation (e) according to the formula

e=time(mins)*rpm*g

where g is a gearing ratio defined by the pitch (p) (in mm/turn) of the thread between threaded axle (18) and the threads (32) of the translatable body and the angle of the cone (alfa), so that g=p*tan(alfa).