NO346430B1

NO346430B1 - Device for preventing an object from falling through a gap

Info

Publication number: NO346430B1
Application number: NO20201254A
Authority: NO
Inventors: Bjørn Egil Kristiansen
Original assignee: Kongshavn Industri As
Priority date: 2020-11-18
Filing date: 2020-11-18
Publication date: 2022-08-08
Also published as: NO20201254A1

Description

TITLE: Device for preventing an object from falling through a gap

Field of the invention

The invention relates to a device for preventing an object from falling through a gap between a skidable offshore drilling rig, and ends of a pair of skidding beams that the drilling rig is arranged to be skidded along. Said drilling rig being movable relative to said ends of the pair of skidding beams.

Background of the invention

Falling object poses danger to both personnel and sensitive equipment. In the oil and gas industry there is constant focus on preventing unwanted incidents related to falling objects. The focus on preventing unwanted incidents relating to falling objects is especially high on offshore oil and gas installations. Offshore oil and gas installations have a small footprint so equipment and personnel are placed on multiple floors/decks. Most of the goods sent from and to such installations are sent by ship and lifted between the installation and the ship by crane. A lot of equipment is also lifted internally on the installation by crane. There is always a danger that equipment and goods lifted over an area may fall and land in that area.

On installation where drilling operations are performed large quantities of equipment is lifted to and from the drillfloor on the drilling rig.

There is a wide variety of offshore oil and gas installation that is equipped with drilling rigs. One type is combined drilling and production platforms that is stationary on the field and built for both performing drilling/well operations and for producing hydrocarbons. Such platforms are often equipped with a skidable drilling rig that can be skidded around above a set of wellheads for the drilling rig to perform drilling, maintenance downhole and other well operation down in the wells that is tied back to the platform.

Another type of offshore installation is jack up rigs. Jack ups rigs are movable drilling rigs and normally purpose built to perform drilling and well operation and do most commonly not comprise facilities for producing hydrocarbons. Jack up rigs can drill, do well completion operations or other types of well operation either on its own with a subsea BOP or they can do similar operation on a wellhead platform or on other types of fixed installations. A jack up rig is therefor often equipped with a skidable drilling rig so it is able to perform work down through the wellhead of the side of the jack up rig. The jack up rig is then placed near a wellhead platform and the drilling rig is skidded out from the side of the hull of the jack up rig so it is above the wellhead on the wellhead platform. And the drilling rig of the jack up rig can also then be skidded around to reach each of the wellheads on the wellhead platform.

On a typically combined drilling and production platform the drilling rig is placed on two set of skidding beams. A first skid or frame is movable along a first set of skidding beams. On top of the first skid the is a second set of skidding beams that is transvers to the first set of skidding beams. On this second set of skidding beams there is a second skid that can be moved along the second set of skidding beams.

In the area below the first set of skidding beams the wellheads are placed and there will usually be wells that are producing with X-mas three and lines with hydrocarbons under pressure going from the x-mas trees to the process plant. The area is sometimes covered with a deck with hatches, but these are not designed to withstand an impact from a heavy object.

On some offshore installation the area the drilling rig can be skidded over covers areas where it is noting below the skidding beams, it is straight down into the sea.

The drillfloor can be 20-30 meters or more above the first set of skidding beams. Pipedeck is often the top deck of the structure closest to one side of the skidding area. Pipedeck is usually more or less on the same height as the drillfloor and is also the area where a lot of the equipment needed on the drillfloor is stored. With other word there is usually a variable-width-gap between pipedeck and drillfloor that is 20-30 meter deep and where a lot of equipment is moved across.

There is need for solution for securing the lower lying areas around a skidable drilling rig from falling objects impacting sensitive equipment, falling into the sea or hitting personnel working in the area.

Disclosure of the state of art

To remedy some of the problems described it is known to avoid lifting above certain areas and to block of areas for personnel.

KR 20100020613 describes a resistance reduction apparatus for a moon pool. It is provided to reduce vortex flow caused in the moon pool by effectively interrupting a flow field into the moon pool. A first rod and a second rod are located separate from each other at the entrance of a moon pool. A grid is located between the first rod and the second rod, with both ends connected to the first and the second rod. The first rod is fixed to one side of the moon pool entrance and the second rod can move close to the first rod.

Objects of the present invention

The invention has one or more of the following objects:

- providing equipment and/or solutions that will decrease the likelihood of equipment or personnel being harmed from falling objects, particular in areas around a skidable drilling rig.

- providing a device that is flexible in use

- providing a system, device or solution for securing an area around a skidable drilling rig from falling objects and that this system, device or solution do not required to be removed and mounted again every time the drilling rig is moved/skidded

Summary of the invention

The invention relates to a device for preventing an object from falling through a gap between a skidable offshore drilling rig, and ends of a pair of skidding beams that the drilling rig is arranged to be skidded along. Said drilling rig being movable relative to said ends of the pair of skidding beams. The device comprises:

- a net to be suspended between the drilling rig and the ends of the pair of skidding beams above an area to be protected from the object falling,

- a drum connected to the ends of the pair of skidding beams and arranged so that said net can be spooled up on said drum from a first end rim of said net,

- rotation means for rotating said drum to spool in and out said net and to maintain tension in said net, and

- attachment means for attaching an opposite second end rim of said net to the skidable offshore drilling rig,

The net is arranged to be spooled in and out of said drum to keep said net stretched out and in tension between the drilling rig and the ends of the pair of skidding beams when the drilling rig is moved relative to the ends of the pair of skidding beams.

The net can comprise an open mask net, a sheet of fabric, canvas or tarpaulin which prevents objects from passing through the net.

Said attachment means can be a suspension beam.

The suspension beam can comprise at least one first impact absorbing element for absorbing tension shocks in the net resulting from the falling object impacting said net.

Said drum can be supported by a pair of drum support bearings each arranged on a drum support structure, said drum support structure is arranged to be connected to said ends of the pair of skidding beams.

The device can further comprise:

- a horizontally extending roller arranged for the net to be passed across to support the net,

- a pair of vertical roller support arms extending between said drum support structure and said horizontally extending roller, for supporting said roller, and - a pair second impact absorbing elements for holding said horizontally extending roller to said pair of vertical extending arms, wherein said impact absorbing elements is arranged to yield to allow said horizontal roller to resiliently move towards said drum for absorbing tension shocks in the net resulting from the object impacting said net.

The drum can further comprises a drum brake for preventing the drum from rotating when said drilling rig is static, or to be activated upon an impact.

The rotation means for rotating said drum is selected from a list consisting of:

a hydraulic motor arranged in one of said drum support structures, an electric motor arranged in one of said drum support structures, a crank handle attached to an end of said drum, and a return spring.

Description of the figures

Embodiments of the present invention will now be described, by way of example only, with reference to the following diagrams wherein:

Fig. 1 shows an embodiment of the device in an angle from above

Fig. 2 shows the same embodiment as in Fig.1 seen from one of the sides Fig. 3 shows the same embodiment as in Fig.1 , looking in the direction where the net can be pulled to spool it of the drum

Fig. 4a shows a roller support arm

Fig. 4b shows the other roller support arm

Fig. 5 shows the connection between a roller support arm and the roller

Fig. 6a shows part of the suspension beam in a first embodiment

Fig. 6b shows the suspension beam in the first embodiment

Fig. 7a shows the suspension beam in a second embodiment

Fig. 7b shows part of the suspension beam in the second embodiment

Fig. 7c shows part of the suspension beam in the second embodiment

Fig. 7d shows part of the suspension beam in the second embodiment Reference numbers

1 First structure

1` Nearby structure (in the case when the first structure is a nearby structure)

1`` A pair of skidding beams (in the case when the nearby structure is the ends of a pair of skidding beams)

2 Second structure

2` A skid (in the case when the second structure is a skid)

2`` Skidable offshore drilling rig (in the case where the second structure and or the skid is a skidable offshore drilling rig)

3 Area to be protected (for example the sea, wellhead area, area with process equipment and or lines with hydrocarbons under pressure) 10 Device for catching of falling objects

11 Net

11.1 First end rim of net (at drum)

11.2 Second end rim of net

12 Drum

12.1 Drum motor (rotation means in the form of drum motor)

12.2 Drum brake

13 Suspension beam

13.1 Pulley

13.2 Wire

13.3 Wire guide

13.4 Attachment loops

13.5 Anchoring points

13.6 Shackles

13.7 Cover

13.8 Damping structure

14 Roller

15 Roller support arms

15. 1 Slots in roll support arms

17 Drum support structure

18.1 First impact absorbing elements

18.2 Second impact absorbing element

Description of preferred embodiments of the invention

The invention relates to a device 10 for preventing a falling object from impacting an area to be protected 3 between a first structure 1 and a second structure 2. The device comprises a net 11 to be suspended above the area to be protected 3 between the two structures 1, 2, a drum 12 for spooling or winding up the net 11 from a first end rim 11.1, and a suspension beam 13 for holding a second end rim 11.2 of the net 11.

The net 11 can be made of or comprise open mask net, a sheet of fabric or canvas, tarpaulin, etc. The net 11 can have shock absorbing abilities.

The drum 12 can be equipped with a drum motor 12.1 for spooling on and off net 11 and for keeping a constant tension in the net 11. The drum can also be equipped with a brake 12.2 for locking the drum 12 when the net 11 is stationary and for securing the net 11 when it is impacted by a falling object. Further the drum can be supported by bearings in each end.

In one preferred embodiment the device 10 further comprises two arms 15 one extending vertically up from each ends of the drum 12. A roller 14 is extending between the arms 15, attached close to the top of the arms 15. One of the purposes of the roller is to change direction of the net 11 from vertical to horizontal. The net 11 is extending more or less vertically up from the drum 12 and then changes direction as it passes over the roll 14 to being more or less horizontal towards the second structure 2. The roll 14 is in each end connected to the arms 15 via a second set of impact absorbing elements 18.2, and the ends of the roll 14 extends into a groove or slot 15.1 in the arm 15. The slot 15.1 extends a distance along the arm 15 from the top of the arm for the purpose of guiding the roll 14 (as seen in Fig.1, 4b and 5).

If a falling object impacts the net 11, the second impact absorbing elements 18.2 that connects the roll 14 to the top of the arm 15 will extend in length allowing the roll 15 to move a distance in the direction towards the drum 12 along the slots 15.1. The energy from the impact will partly be transferred to the second impact absorbing elements 18.2 that will be deformed and absorb energy from the impact. One possible embodiment of the connection between the roll and the arm is seen in a close-up view in Fig.5.

The second end rim 11.2 of the net 11 is connected to the second structure 2 via an elongated suspension beam 13 that comprises a shock absorbing suspension. The shock absorbing suspension comprises a first set of impact absorbing elements 18.1. Two possible embodiments of the shock absorbing suspension in the beam 13 is disclosed in the figures.

Fig. 6a and.6b shows one possible embodiment that comprises a pully system. The system comprises two wires 13.2 that are threaded through attachments loops 13.4 on the second end rim 11.2 of the net 11. Along the suspension beam 13 wire guides 13.3 are placed. The two wires 13.2 are passed behind the wire guide 13.3 (i.e. on the side of the wire guide 13.3 facing the second structure 2) every other time so that one wire is behind the wire guide 13.3 and the other wire 13.2 is passed through the attachment loops 13.4 of the net 11. All the attachment loops 13.4 is threaded by at least one wire 13.2. The wires passes over a pulley 13.1 in each longitudinal end of the suspension beam 13 and the wires are directed back towards the middle (in the longitudinal direction) of the suspension beam 13 where both wires 13.2 is anchored in both ends to anchoring points 13.5. Both wires 13.2 are anchored in the anchoring points 13.5 via first impact absorbing elements 18.1.

If a falling object impacts the net 11 the net will pull on the wires 13.2 and the wires will transfer the pull to the first impact absorbing elements 18.1 that will deform i.e. extend in length and absorb energy from the impact.

A second embodiment of the suspension beam 13 is showed in Fig.7a – 7d. In this embodiment a wire 13.2 is passed through attachment loops (not seen in Fig.7a-7d) and through a series of shackles 13.6 connected to first impact absorbing elements 18.1 anchored in the suspension beam 13. An object falling and impacting the net 11 will cause the net 11 to pull on the first impact absorbing elements 18 that will give inn and extend in length i.e. absorb energy from the impact.

In addition, the second embodiment is equipped with a cover 13.7 supported with a deformation structure 13.8. The purpose of this is to provide means for dampening the impact of an object falling and hitting the suspension beam 13 and the first impact absorbing elements 18.1. The cover 13.7 will cover the suspension beam 13 and deflect a falling object towards the net 11. Such cover 13.7 and dampening structure 13.8 can also be arranged on the first embodiment of the suspension beam 13, but the first embodiment will in most cases be slimmer and is therefore not so exposed for falling objects.

The impact absorbing elements 18.1, 18.2 can be a tearing brake of the type Pfeifer Isofer AG has described in patent EP2920369B1. Such an impact absorbing element will be suitable for use with the device 10. The Pfeifer brake is very compact before it is teared up along a path weakened by perforations and can extended several times its starting length. Other types of shock absorbing elements 18.1, 18.2 can also be used.

Different types of nets 11 can be used but one type that is particular suitable is the type of net described in patent application NO320548B1.

In Fig.1 one can see one application that the device 10 is suitable for. The net 11 is stretched up between the first structure 1, which is a nearby structure 1` in this case one of the ends of a pair of skidding beams 1`` and the second structure 2 in this case a skid 2` being movable along said skidding beams 1``. The drum 12 is held by a drum support structure 17 (or two structures 17 in this case, one on each end of the drum 12) that is fastened to the ends of the skidding beams 1``. The suspension beam 13 is attached to the second structure 2 the skid 2`. When the skid 2` is skidded away from the drum 12, the drum is arranged to spool off more net 11 as it is pulled of the drum 12 by the skid 2`.

The skid 2` can be a skidable offshore drilling rig 2``. The net 11 can then cover the area between the skidding beams 1`` from the end of the skidding beams 1`` and to the skid where on the drilling rig 2`` in this case is placed. The device 10 can be designed so that the drum support structure 17 and/or the drum and roll extend beyond the area between the skidding beams 1``, hence the net 11 can cover an area wider than in between the skidding beams 1``. For instance, if the drilling rig 2`` is wider than the distance between the skidding beams 1``.

The net 11 will be covering and protecting the area to be protected 3 in this case the below wellhead area and/or the sea. Devices 10 with nets 11 can be placed on both sides (opposite sides) of the drilling rig 2`` and will then cover all the wellheads and most of the sensitive process equipment below the area where the drilling rig 2`` can be skidded.

The device 10 can have similar applications in the oil and gas industry or in other industries.

In one aspect the invention relates to a device 10 for preventing an object from falling through a gap between a first structure 1 and a second structure 2, said structures 1, 2 being movable relative to each other, wherein the device 10 comprises:

- a net 11 to be suspended between the two structures 1, 2 above an area to be protected 3 from the object falling,

- a drum 12 connected to the first structure 1 and arranged so that said net 11 can be spooled up on said drum 12 from a first end rim 11.1 of said net 11, - rotation means 12.1 for rotating said drum 12 to spool in and out said net 11 and to maintain tension in said net 11, and

- attachment means 13 for attaching an opposite second end rim 11.2 of said net 11 to the second structure 2,

wherein the net 11 is arranged to be spooled in and out of said drum 12 to keep said net 11 stretched out and in tension between the first structure 1 and the second structure 2 when they are moved relative to each other.

The device 10 will function best if the two structures are movable relative to each other along a line in the direction towards each other and away from each other.

Claims

1. Device (10) for preventing an object from falling through a gap between a skidable offshore drilling rig (2``), and ends of a pair of skidding beams (1``) that the drilling rig (2``) is arranged to be skidded along, said drilling rig (2``) being movable relative to said ends of the pair of skidding beams (1``), characterized in that the device (10) comprises:

- a net (11) to be suspended between the drilling rig (2``) and the ends of the pair of skidding beams (1``) above an area to be protected (3) from the object falling,

- a drum (12) connected to the ends of the pair of skidding beams (1``) and arranged so that said net (11) can be spooled up on said drum (12) from a first end rim (11.1) of said net (11),

- rotation means (12.1) for rotating said drum (12) to spool in and out said net (11) and to maintain tension in said net (11), and

- attachment means for attaching an opposite second end rim (11.2) of said net (11) to the skidable offshore drilling rig (2``),

wherein the net (11) is arranged to be spooled in and out of said drum (12) to keep said net (11) stretched out and in tension between the drilling rig (2``) and the ends of the pair of skidding beams (1``) when the drilling rig (2``) is moved relative to the ends of the pair of skidding beams (1``).

2. Device (10) according to claim 1, wherein the net (11) comprise an open mask net, a sheet of fabric, canvas or tarpaulin which prevents objects from passing through the net (11).

3. The device (10) according to claim 1 or 2, wherein said attachment means is a suspension beam (13).

4. The device (10) according to claim 3, wherein the suspension beam (13) comprises at least one first impact absorbing element (18.1) for absorbing tension shocks in the net (11) resulting from the falling object impacting said net (11).

5. The device (10) according to any preceding claim, wherein said drum (12) is supported by a pair of drum support bearings each arranged on a drum support structure (17), said drum support structure (17) is arranged to be connected to said ends of the pair of skidding beams (1``).

6. The device (10) according to claim 5, wherein the device (10) further comprises: - a horizontally extending roller (14) arranged for the net (11) to be passed across to support the net (11),

- a pair of vertical roller support arms (15) extending between said drum support structure (17) and said horizontally extending roller (14), for supporting said roller (14), and

- a pair second impact absorbing elements (18.2) for holding said horizontally extending roller (14) to said pair of vertical extending arms (15), wherein said second impact absorbing elements (18.2) is arranged to yield to allow said horizontal roller (15) to resiliently move towards said drum (12) for absorbing tension shocks in the net (11) resulting from the object impacting said net (11).

7. The device (10) according to any of the preceding claims, wherein the drum (12) further comprises a drum brake (12.2) for preventing the drum (12) from rotating when said drilling rig (2``) is static, or to be activated upon an impact.

8. The device (10) according to any of the preceding claims, wherein the rotation means (12.1) for rotating said drum (12) is selected from a list consisting of:

a hydraulic motor arranged in one of said drum support structures (17), an electric motor arranged in one of said drum support structures (17), a crank handle attached to an end of said drum (12), and a return spring.