GB2588210A

GB2588210A - Apparatus for and method of moving a suspended object around a drill floor of a drilling rig

Info

Publication number: GB2588210A
Application number: GB1914955.8A
Authority: GB
Inventors: Lien Geir; Mydland Petter
Original assignee: Mhwirth AS
Current assignee: Mhwirth AS
Priority date: 2019-10-16
Filing date: 2019-10-16
Publication date: 2021-04-21
Anticipated expiration: 2039-10-16
Also published as: GB2588210B; GB201914955D0

Abstract

A guiding apparatus 400 for moving a suspended object 464, e.g. a short sub, around a drilling rig 420 drill floor 422, comprises a base 402 and an arm 404. The base may be fixed or on wheels or tracks. The arm has a first end 404a mounted to the base and a second end 404b, having a wire guide,448', and at least one joint so that the arm, or a portion thereof, may pivot relative to the base under action of actuators. The wire guide comprises a hook configured to partially or completely surround a cable 462 from which the object is suspended so that operation of the actuators causes the wire guide to engage with a portion of the cable 462 to move that portion of the cable 462 relative to the drill floor 422. The hook may comprise two co-operating hinged hook halves or be a fixed, tube or rod twisted over one turn of a helix. There may be overload protection to detach the hook and protect the arm. Reduces manual effort on the drill floor.

Description

Apparatus for and Method of Moving a Suspended Obiect around a Drill Floor of a Drilling Rig The present invention relates to apparatus for and method of moving a suspended object around drill floor of a drilling rig during drilling a well bore or during or oil and / or gas production.

Drilling rigs have a platform directly under a derrick which provides a work area in which the rig crew can work. The driller's cabin, from which the major components of the rig are controlled, is located adjacent the drill floor.

The drill floor is the most dangerous location on a drilling rig because of the heavy equipment which is moved around the area, yet many tasks associated with the running of a drilling operation are currently carried out manually by personnel working on the drill floor. The most dangerous area of the drill floor is known as the red zone.

In drilling operations, it is common to build a string of tubulars, such as a drill string, on the drill floor above the well centre opening. The string is usually assembled using a series of threaded pipe sections, where the threaded connections are made up (or broken out) using appropriate machines, such as pipe handling machines and power tongs. A bottom hole assembly (BHA) including a drill bit, is mounted at the lowermost end of the drill string.

Sometimes a short tubular or sub, is secured to the top of the drill string. The subs are generally stored on a pallet with a plurality of vertical rods extending upwardly from its uppermost surface, each subs being placed with one end over one of the rods so that the sub is supported in a vertical or near vertical orientation. In order to lift one of the subs, it is attached to cable, which extends from the sub over the Derrick, and down to a winch located on the drill floor. The winch may then be operated to reel in the cable, and lift the sub off the drill floor. Operators on the drill floor push or pull the cable above the sub to manoeuvre the sub in a generally horizontal plane so that it is vertically above the uppermost end of the drill string, before the winch is operated to lower the sub onto the top of the drill string. A winch and cable may also be used to lift other heavy items off the drill floor, with operators manually moving the item in a generally horizontal direction around the drill floor to the desired location.

It is an object of the present invention to provide an improved apparatus for and method of moving a suspended weight around a drill floor of a drilling rig.

According to a first aspect of the invention we provide a guiding apparatus for moving a suspended object around a drill floor of a drilling rig, the guiding apparatus having a base and an arm, the base being configured to support the arm on a drill floor of a drilling rig, the arm having a first end which is mounted on the base, a second end at which is provided with a wire guide, at least one articulated joint by means of which the arm, or a portion of the arm may pivot relative to the base, an actuator which is operable to pivot the arm or a portion of the arm relative to the base, wherein the wire guide comprises a hook which is configured to partially or completely surround a cable from which the object is suspended, so that operation of the actuator can cause the wire guide to engage with a portion of the cable to move that portion of the cable relative to the drill floor.

The guiding apparatus may further comprise a motor which is connected to the actuator and operable to drive the actuator.

The actuator may be hydraulically operable.

The guiding apparatus may further be provided with a controller which is operable to control the operation of the actuator, and which is remote from the remainder of the guiding apparatus.

The articulated joint may form a pivotal connection between the arm and the base.

The arm may comprise a first and second portion which are joined by the articulated joint. In this case, the first end of the arm may also be pivotally mounted on the base.

A release mechanism may be provided whereby a cable enclosed by the hook of the wire guide is released if it exerts a force on the arm of the guiding apparatus of greater than a predetermined level.

The hook of the wire guide may comprise at least two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm.

One of both of the hook parts may be pivotally mounted on a base part of the wire guide, the wire guide further comprising a release actuator which is operable to pivot the or each hook part relative to the base part between an open position in which ends of the hooks parts are spaced from one another so that a cable can pass between the hook parts to be partially enclosed by the hook parts, and a closed position in which the hook parts completely enclose the wire axis.

The two hook parts may be spaced from one another in a direction generally parallel to the wire axis.

The wire guide may be mounted on a holder which is pivotally connected to the second end of the arm, and the guiding apparatus further provided with a wire guide actuator which is operable to pivot the wire guide relative to the arm.

The wire guide may be mounted on a holder which is connected to the second end of the arm, the wire guide being mounted on the holder via a release mechanism which is operable to release the wire guide from the holder when a force exerted on the wire guide to separate it from the holder exceeds a predetermined level.

According to a second aspect of the invention we provide a drilling rig having a drill floor and a guiding apparatus according to the first aspect of the invention, the base of the guiding apparatus being supported on the drill floor.

The drilling rig may further comprise a derrick, a winch and a cable, the cable having a first end which is connected to the winch, a free end which can be connected to an object to be suspended above the drill floor, and an intermediate portion which is supported by the derrick.

The wire guide of the guiding apparatus may be arranged so that it surrounds or partially surrounds a portion of the cable between its free end and the intermediate portion.

A release part may be mounted on the cable below the portion of the cable surrounded by the wire guide, and where the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm, and one of both of the hook parts is pivotally mounted on a base pad of the wire guide, and can pivot relative to the base part between an open position in which ends of the hooks parts are spaced from one another so that a cable can pass between the hook parts to be partially enclosed by the hook pads, and a closed position in which the hook parts completely enclose the wire axis, the wire guide may be configured such that the hook parts move from the closed position to the open position when the release part engages with the hook parts and exerts a force on the hook parts which is greater than a predetermined level.

According to a third aspect of the invention we provide a method of moving an object around the drill floor of a drilling rig according to the second aspect of the invention wherein the method comprises: a) connecting the free end of the cable to the object, b) operating the winch to lift the object off the drill floor, c) moving the guiding apparatus so that the hook substantially surrounds a portion of the cable, d) operating the actuator of the guiding apparatus so that the hook of the guiding apparatus exerts a force on the cable to move the object in the desired direction.

Where the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm, one of both of the hook parts is pivotally mounted on a base part of the wire guide, and the wire guide further comprises a release actuator which is operable to pivot the or each hook part relative to the base part between an open position in which ends of the hooks parts are spaced from one another so that a cable can pass between the hook parts to be partially encircled by the hook pads, and a closed position in which the hook parts completely encircle the wire axis, step c of the method may comprise using the release actuator to move the hook parts to the open position, using the actuator of the guiding apparatus to move the arm towards the cable such that the cable moves to a position in which it is partially encircled by the two hook parts, and then using the release actuator to move the hook parts to the closed position so that the cable is completely encircled by the hook parts.

Where the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm and the two hook parts are spaced from one another in a direction generally parallel to the wire axis, step c of the method may comprise pivoting the hook about a pivot axis so that the wire axis is generally perpendicular to the longitudinal axis of the cable, using the actuator to move the arm towards the cable so that the cable passes between the two hook parts, and then pivoting the hook about the pivot axis so that the wire axis is generally parallel to the longitudinal axis of the cable.

Embodiments of the invention will now be described with reference to the following drawings of which: FIGURE 1 is an illustration of the base and arm of a guiding apparatus according to the first aspect of the invention, FIGURES 2a and 2b are illustrations of an embodiment of wire guide suitable for use in the apparatus illustrated in Figure 1, with a) the wire guide in an engage/release position, and b) the wire guide in an operative position, FIGURE 3 is an illustration of the wire guide illustrated in Figures 1a, 1b,and 1c with the release mechanism activated, FIGURES 4a, 4b and 4c are illustrations of an alternative embodiment of wire guide suitable for use in the apparatus illustrated in Figure 1, with a) the wire guide in an engage/release position, and b) the wire guide in the engage/release position being brought into engagement with a wire, and c) the wire guide in an operative position, and FIGURE 5 is a schematic illustration of a drilling rig according to the second aspect of the invention.

Referring to Figure 1, there is shown a guide apparatus 400 for guiding the movement of a load suspended from a cable or wire, the apparatus 400 having a base 402 and an arm 404, the base 402 being configured to support the arm 404 on a drill floor of a drilling rig. The arm 404 has a first end 404a which is mounted on the base 402, a second end 404b at which is provided a gripper 406 suitable for holding a wire guide (not shown in Figure 1) and at least one articulated joint 408 by means of which the arm 404, or a portion of the arm 404 may pivot relative to the base 402. The apparatus further comprises an actuator which is operable to pivot the arm 404 about the articulated joint 408 to alter the position of the gripper 406 relative to the base 402.

In this embodiment, the arm 404 comprises a first portion 410 and second portion 412 which are joined by a first articulated joint 408. In this example, the articulated joint is configured to allow the second portion 412 to pivot relative to the first portion 410 about an axis Z' which is generally parallel to a surface on which the base 402 is supported (not shown). It will be appreciated that this need not be the case, however, and the articulated joint could equally comprise a pivotal connection between the first end 404a of the arm 404 and the base 402.

The first end 404a of the arm 404 is pivotally mounted on the base 402. In this example, the first end of the first portion 410 is pivotal an axis X' which is generally perpendicular to a surface on which the base 402 is supported. Moreover, in this embodiment, the joint between the first portion 410 and the base 402 is configured to allow the first portion 410 of the arm 404 to pivot relative to the base 402 about an axis Y' which is generally parallel to a surface on which the base 402 is supported. This need not be the case, however. The first end 410a of the first portion 410 of the arm 404 could be fixed to the base 402, or pivotal about only one of these axes X', Y'.

A first actuator 438 is operable to pivot the second portion 412 of the arm relative to the first portion 410 of the arm about the articulated joint 408. A second actuator 440 is provided to pivot the first portion 410 of the arm 404 relative to the base 402. In this embodiment, the second actuator 440 is operable to carry out pivoting of the arm 402 about each pivot axes, X', Y' independently of the other, and may comprise two separate actuators.

The gripper 406 comprises a pair of clamping members 406a, 406b which are pivotally connected to a gripper base 406c. A third actuator 442 is provided which is operable to pivot the clamping members relative to the gripper base 406c, so that the clamping members 406a, 406b can move towards one another to clamp around any part placed between the two clamping members 406a, 406b, and away from one another to release the part.

In this case the arm 404 is provided with a second articulated joint 444 in the second arm portion 412 directly adjacent the second end 404b of the arm 404. A fourth actuator 446 is provided, and this is operable to pivot the second end 404b of the arm 404 about an axis W' which is generally perpendicular to the longitudinal axis of the part of the second arm portion 412 which extends to the first articulated joint 408.

In this embodiment, the actuators 438, 440, 442, 446 are operated hydraulically, and may comprise a hydraulic motor. The source of pressurised hydraulic fluid required for operation of the actuators 438, 440, 442, 446 may be a dedicated hydraulic power pack provided as part of the guiding apparatus 400. Alternatively, pressurised hydraulic fluid may supplied from a pump located remotely from the apparatus and connected to the apparatus via a hydraulic line.

Referring now to Figures 2a and 2b, there is shown an embodiment of wire guide 448 which may be used in conjunction with the apparatus 400 illustrated in Figure 1. The wire guide 448 comprises a hook 450, which has a wire axis A' and which is mounted on a base part 452, the hook 450 being configured to enclose or at least partially enclose the wire axis A'.

In this embodiment, the hook 450 comprises two separate hook parts 450a, 450b which are both pivotally connected to the base part 452. The wire guide 448 is provided with a release actuator (not shown) which is operable to pivot both of the hook parts 450a, 450b relative to the base part 425 between an open position in which the free ends of the hook parts 450a, 450b are spaced from one another so that a wire or cable can be moved between them to the wire axis, and a closed position in which the hook parts completely enclose the wire axis. The hook parts 450a, 450b in the embodiment are curved and, when in the closed position, together with the base part 452, enclose a generally cylindrical space, with the wire axis A' extending along the longitudinal axis of the cylindrical space.

It will be appreciated that, whilst in this embodiment, both hook parts 450a, 450b are pivoted by the release actuator, this is not necessarily the case. The hook 450 may be moved between its open and closed positions by the pivoting of only one of the hook parts 450a, 450b.

The wire guide 448 also comprises a grip part 454, which in this embodiment is generally cylindrical and is generally parallel to the cylindrical space enclosed by the hook parts 450a, 450b. The wire guide 448 may therefore by mounted on the second end 404b of the arm 404 of the apparatus illustrated in Figure 1, by placing the grip part 454 of the wire guide 448 between the two clamping members 406a, 406b of the gripper 406, and operating the third actuator 442 to pivot the clamping members 406a, 406b so that they clamp onto and hold the grip part 454 of the wire guide 448, as illustrated in Figure 2b.

An alternative embodiment of wire guide 448' is illustrated in Figures 3 and 4a, 4b and 4c. In this embodiments, the hook 450' comprises two hook parts 450a', 450b' which are not pivotal relative to the base part 452'. Instead, the two hook parts 450a', 450b' are spaced from one another in a direction generally parallel to the wire axis A'.

In this particular embodiment, the hook 450 comprises a tube or rod which is curved to form part of a helix (in this example just over one turn of a helix), which spirals around wire axis A'. It will be appreciated, however, that the tube/rod need not be exactly helical, and may simply be curved around the wire axis A' so that when viewed parallel to the wire axis A', the wire axis A' is surrounded completely, or almost completely, by the hook 450.

The base part 452' is mounted on a holder 454' which is mounted on the end of the second portion 412 of the arm 404. The holder 454' could comprise a grip part like that shown in the embodiment illustrated in Figures 2a and 2b, and the gripper 406 used to mount the wire guide 448' on the arm 404 as described above. In this embodiment, however, the holder 454' is secured directly to the second end 404b of the arm 404.

The hook 450' is fixed to the base part 452', and therefore no release actuator is required. Instead an actuator 456 is provided which is operable to pivot the wire guide 448' about a pivot axis V which is generally perpendicular to the wire axis A' and to the longitudinal axis of the second portion 412 of the arm 404.

The wire guide comprises a release mechanism which protects the arm 404 from being overloaded or damaged by excess force being applied to it by the wire guide. In this embodiment, the base part 452' and holder 454' are mechanically coupled together in such a way that the two can be parted if sufficient force is exerted on the hook 450' pulling it away from the arm 404. In this embodiment, the holder 454' comprises an outer frame 454a' which is secured to the second end 404b' of the arm 404, and the base part 452' an inner frame.

In this embodiment, the inner frame 452' is retained in the outer frame 454' by means of a detent mechanism in the form of plurality of generally hemispherical protuberances 458 which extend from radially outward facing surfaces of the inner frame 452' and are lodged in correspondingly shaped recesses 460 in the radially inwardly facing surface of the outer frame 454'. The lodging of the protuberances 458 in the recesses 460 holds the base part 452' in the holder 454' together if a relatively low force is applied to the hook 450', but if a sufficiently high force is applied to the hook 450' to pull it away from the arm 404, the protuberances will become dislodged, and the hook 450' become separated from the arm 404, as illustrated in Figure 3.

Alternative configurations of release mechanism are possible, however. For example, the protuberances may be provided on the outer frame 454' and lodge in corresponding recesses in the inner frame 452'. Moreover, instead of protuberences, spring loaded elements may extend from the inner frame 452' into corresponding recesses in the outer frame 454' (or vice versa). Alternatively, the wire guide 448' may be secured to the holder 454' by means of shear pin bolts which fracture to release the wire guide 448' from the holder 454' when the applied force exceeds a predetermined level.

Referring now to Figure 5, there is shown a drilling rig 420 having a drill floor 422 and a guiding apparatus 400 as described above, on the drill floor 422. In this case, the base 402 is mounted on a trolley 424 which has wheels 426 which are operable to move the base 402 and arm 404 around the drill floor 422. It will be appreciated that the trolley could equally be provided by tracks, Mecanum or omni wheels, or any other suitable motive means for moving it around the drill floor. The base need not be movable relative to the drill floor 422, and could, however, be secured to the drill floor 422, either directly or secured to a platform which is secured to the drill floor 422.

Advantageously the wheels 426 are powered by a trolley motor which operable remotely, for example, from a driller's cabin 428 adjacent the drill floor 422.

In a preferred embodiment, the actuators 438, 440, 443, 446, 456 provided to operate the guiding apparatus 400 are also controlled remotely, preferably from the driller's cabin 428.

This remote control may be achieved by a wired or wireless connection to the trolley motor or actuators 438, 440, 442,446, 456.

The drill floor 422 is provided with a derrick 430 and an aperture 432 which is below the derrick 430, through which a drill string 434 extends. The drill string 434 is made up of a plurality of pipe sections 434a, 434b which are joined end to end. A bottom hole assemble (BHA) 435 is provided at the lowermost end of the lowest pipe section 434b.

The drilling rig 420 is further provided with two winches 436 by means of which heavy items of equipment may be suspended from the derrick 430. A cable 462 extends from each of the winches 236. Each cable has a first end which is connected to its respective winch, and a free end which can be connected to an object to be lifted from and suspended above the drill floor 422, In the illustration shown in Figure 2, the free end of each cable 462 is secured to an end of a short section of drill string or a sub 464. An intermediate portion of each cable 462 extends over and is supported by a fixed pulley 466 mounted on the derrick 430.

The guiding apparatus 400 can be used to assist in manoeuvring the sub 464 in a generally horizontal direction whilst it is suspended from the cables 462 over the drill floor 422. The hook 450, 450' of the wire guide 448, 448' is placed around one of the cables 462 and one or more of the first, second and fourth actuators 438, 440, 446 are operated so that the cable 462 is pushed or pulled by the guiding apparatus 400 in such a way as to move the sub 464 to the desired position. Where the guiding apparatus 400 is mounted on a trolley 424, rather than secured to the drill floor 422, the trolley motor may also be operated to achieve the desired movement of the sub 464 by movement of the guiding apparatus 400 relative to the drill floor 422 in addition to movement of the arm 404 itself.

Where the wire guide 448 is as illustrated in Figures 2a and 2b, the hook 450 is placed around the cable 462 by operating the release actuator to pivot one or both of the hook parts 450a, 450b to the open position as illustrated in Figure 2a. One or more of the first, second or fourth actuators 438, 440, 446 are then operated to move the hook 450 towards the cable 462 until the cable passes through the gap between the ends of the two hook parts 450a, 450b into the space enclosed by the two hook parts 450a, 450b. The release actuator is then operated to pivot one or both of the hook parts 450a, 450b to the closed position as illustrated in Figure 2b so that a portion of the cable is encircled or surrounded by the hook 450..

Where the wire guide 448' is as illustrated in Figures 3, 4a,4b, and 4c, the hook 450' is placed around the cable 462 by operating the actuator 456 to pivot the wire guide 450' about pivot axis V until the wire axis A' is generally perpendicular to the cable 462 as illustrated in Figure 4a. One or more of the first, second or fourth actuators 438, 440, 446 are then operated to move the hook 450' towards the cable 462 until the cable passes through the gap between the two hook parts 450a', 450b' into the space enclosed by the two hook parts 450a', 450b' as illustrated in Figure 4b. The actuator 456 is then operated to pivot the wire guide 450' about the pivot axis V' until the wire axis A' is generally parallel to the cable 462 as illustrated in Figure 4c. A portion of the cable 462 is thus encircled or surrounded by the hook 450'.

It will be appreciated that the object suspended from the cable 462 can be very heavy, and, as such, significant forces can be exerted on the arm 404 whilst pulling on the cable 462 to move the object. As such, a release mechanism is provided to disengage the cable 462 from the arm 404 should these forces reach such high levels that they could cause damage to the arm 404.

In the case of the embodiment of wire guide illustrated in Figures 2a and 2b, a release part, in this example in the form of a ball 468, is mounted on the cable 462. The wire guide 448 is placed around the cable 462 such that the release ball 468 is below the hook 450. The lowermost ends of the hook parts 450a, 450b are chamfered and sized such the release ball 468 cannot pass along the cylindrical space enclosed by the hook parts 450a, 450b when they are in the closed position. If the cable 462 moves upwardly relative to the hook 450, the release ball 468 engages with the chamfered portion of the hook parts 450a, 450b, and if the force exerted on the hook 450 by the cable 462 is sufficiently large, this causes the hook parts 450a, 450b to pivot to their open position and free the release ball 468.

In relation to the embodiment of wire guide 448' illustrated in Figures 3, 4a, 4b, and 4c, if the cable 462 is pulling on the arm 404 with a sufficiently high force, the base part 452' of the wire guide 450' will detach from the holder 454' as described in relation to Figure 3 above, and the excess force of the arm 404 will be removed in that way. It should be appreciated, however, that the embodiment of wire guide 448 illustrated in Figures 2a and 2b could also be mounted on the arm 404 via a holder from which it is detachable in the same way.

In the embodiment illustrated in Figure 5, the drilling rig 420 is provided with one guiding apparatus 400. It will be appreciated that more than one guiding apparatus 400 may be provided, with each guiding apparatus pulling or pushing on the same or a different cable 462. For example, in the embodiment illustrated in Figure 5, two guiding apparatus 400 may be provided on the drill floor 422, with the wire guide of one guiding apparatus pushing or pulling on one of the two cables 462, and the wire guide of the other guiding apparatus pushing or pulling on the other one of the two cables 462.

Claims

Claims 1 A guiding apparatus for moving a suspended object around a drill floor of a drilling rig, the guiding apparatus having a base and an arm, the base being configured to support the arm on a drill floor of a drilling rig, the arm having a first end which is mounted on the base, a second end at which is provided with a wire guide, at least one articulated joint by means of which the arm, or a portion of the arm may pivot relative to the base, an actuator which is operable to pivot the arm or a portion of the arm relative to the base, wherein the wire guide comprises a hook which is configured to partially or completely surround a cable from which the object is suspended, so that operation of the actuator can cause the wire guide to engage with a portion of the cable to move that portion of the cable relative to the drill floor.
2 A guiding apparatus according to claim 1 wherein the actuator is hydraulically operable.
3 A guiding apparatus according to any preceding claim wherein the guiding apparatus is further provided with a controller which is operable to control the operation of the actuator, and which is remote from the remainder of the guiding apparatus.
4 A guiding apparatus according to any preceding claim wherein the articulated joint forms a pivotal connection between the arm and the base.
A guiding apparatus according to any one of claims 1 to 3 wherein the arm comprises a first and second portion which are joined by the articulated joint.
6 A guiding apparatus according to claim 5 wherein the first end of the arm is pivotally mounted on the base.
7 A guiding apparatus according to any preceding claim wherein a release mechanism is provided whereby a cable enclosed by the hook of the wire guide is released if it exerts a force on the arm of the guiding apparatus of greater than a predetermined level.
8 A guiding apparatus according to any preceding claim wherein the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm.
9 A guiding apparatus according to claim 8 wherein one of both of the hook parts is pivotally mounted on a base part of the wire guide, and the wire guide further comprises a release actuator which is operable to pivot the or each hook part relative to the base part between an open position in which ends of the hooks parts are spaced from one another so that a cable can pass between the hook parts to be partially enclosed by the hook parts, and a closed position in which the hook parts completely enclose the wire axis.
10.A guiding apparatus according to claim 8 wherein the two hook parts are spaced from one another in a direction generally parallel to the wire axis.
11.A guiding apparatus according to any one of claims 8 to 10 wherein the wire guide is mounted on a holder which is pivotally connected to the second end of the arm, and the guiding apparatus is further provided with a wire guide actuator which is operable to pivot the wire guide relative to the arm.
12.A guiding apparatus according to any one of claims 8 to 11 wherein the wire guide is mounted on a holder which is connected to the second end of the arm, the wire guide being mounted on the holder via a release mechanism which is operable to release the wire guide from the holder when a force exerted on the wire guide to separate it from the holder exceeds a predetermined level.
13.A drilling rig having a drill floor and a guiding apparatus according to any one of claims 1 to 12, the base of the guiding apparatus being supported on the drill floor.
14.A drilling rig according to claim 13 further comprising a derrick, a winch and a cable, the cable having a first end which is connected to the winch, a free end which can be connected to an object to be suspended above the drill floor, and an intermediate portion which is supported by the derrick
15.A drilling rig according to claim 14 wherein the wire guide of the guiding apparatus is arranged so that it surrounds or partially surrounds a portion of the cable between its free end and the intermediate portion.
16.A drilling rig according to claim 15 wherein a release part is mounted on the cable below the portion of the cable surrounded by the wire guide, the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm, and one of both of the hook parts is pivotally mounted on a base part of the wire guide, and can pivot relative to the base part between an open position in which ends of the hooks parts are spaced from one another so that a cable can pass between the hook parts to be partially enclosed by the hook parts, and a closed position in which the hook parts completely enclose the wire axis, the wire guide being configured such that the hook parts move from the closed position to the open position when the release part engages with the hook parts and exerts a force on the hook parts which is greater than a predetermined level.
17.A method of moving an object around the drill floor of a drilling rig according to any of claims 14 to 16 wherein the method comprises: e) connecting the free end of the cable to the object, f) operating the winch to lift the object off the drill floor, g) moving the guiding apparatus so that the hook substantially surrounds a portion of the cable, h) operating the actuator of the guiding apparatus so that the hook of the guiding apparatus exerts a force on the cable to move the object in the desired direction.
18. The method according to claim 17 wherein the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm, one of both of the hook parts is pivotally mounted on a base part of the wire guide, and the wire guide further comprises a release actuator which is operable to pivot the or each hook part relative to the base part between an open position in which ends of the hooks parts are spaced from one another so that a cable can pass between the hook parts to be partially encircled by the hook parts, and a closed position in which the hook parts completely encircle the wire axis, step c of the method comprising using the release actuator to move the hook parts to the open position, using the actuator of the guiding apparatus to move the arm towards the cable such that the cable moves to a position in which it is partially encircled by the two hook parts, and then using the release actuator to move the hook parts to the closed position so that the cable is completely encircled by the hook parts.
19 The method according to claim 17 wherein the hook of the wire guide comprises two hook parts each of which extends around a portion of a wire axis which is generally perpendicular to a longitudinal axis of the arm and the two hook parts are spaced from one another in a direction generally parallel to the wire axis, step c comprising pivoting the hook about a pivot axis so that the wire axis is generally perpendicular to the longitudinal axis of the cable, using the actuator to move the arm towards the cable so that the cable passes between the two hook parts, and then pivoting the hook about the pivot axis so that the wire axis is generally parallel to the longitudinal axis of the cable.