NO20180386A1

NO20180386A1 - A vent hatch device

Info

Publication number: NO20180386A1
Application number: NO20180386A
Authority: NO
Inventors: Sigurd Steffenssen
Original assignee: Kvenna Emt As
Priority date: 2018-03-19
Filing date: 2018-03-19
Publication date: 2019-09-20
Also published as: NO344900B1

Description

A vent hatch device

Field of the invention

The invention concerns subsea structures for installation on a seabed. More particularly, the invention concerns a vent hatch device for hollow seabed structures, such as suction piles and the like.

Background of the invention

Suction piles are well known devices that are used to firmly attach a structure to a subsea seabed. Installation water depths of about 3000 meters are not uncommon. In principle, a suction pile comprises a bucket-shaped body, having a generally a generally tubular cross-section. One end of the tubular body is open and the other end is closed. Installation is performed by lowering the suction pile to the seabed with the open end facing downwards, and allowing the open end to penetrate the seabed and a distance into the soil beneath it, thus becoming partially embedded. The seabed penetration may be achieved by the mere weight of the suction pile (and any structure that it might carry) and/or by its downward momentum. The closed end, which is facing upwards during installation, is furnished with one or more openings furnished with vent hatches. During suction pile deployment and penetration, as described, the vent hatch (or hatches) is open, such that water inside the suction pile may escape through the hatch.

Following the aforementioned installation steps, and in order to firmly install the suction pile in the seabed, the vent hatch (or hatches) is closed, and air and remaining water inside the suction pile are pumped out via a hose and an associated valve and pump system. This pumping action creates a vacuum which serves to force the suction pile even further into the seabed soil. Finally, any remaining voids inside the suction pile may be filled with mud, grout or any other suitable substance. A remotely operated vehicle (ROV) is normally used to close the vent hatch, and to connect and disconnect the pump hose.

Suction piles are also commonly referred to as suction anchors, suction caissons, and suction buckets, and are used to moor a floating vessels and rigs, and to provide seabed foundations for platforms and subsea structures. Such subsea structures may for example be manifolds, valve trees, and templates.

A number of vent hatch types exist. In principle, a vent hatch comprises a coaming which is attached around an opening in the suction pile, and a hatch cover (or lid) which is connected to the coaming by means of one or more hinges. Various locking mechanisms exist, such as clamps or wedges. One problem with the known vent hatches is that they have a large (high) locking mechanism, require large forces to keep the cover in the closed position, and thus are relatively heavy. If the suction pile installation is unsuccessful and a realignment or relocation is required, the vent hatch must be opened and the embedding procedure must be repeated. It is a need for a vent hatch which is lighter, smaller and easier to operate than those of the prior art.

Summary of the invention

The invention is set forth and characterized in the main claim, while the dependent claims describe other characteristics of the invention.

It is thus provided a vent hatch device for a suction pile or similar, comprising a coaming configured for connection to an opening in said suction pile, a hatch cover configured for sealing connection with the coaming, and locking means for selectively locking and unlocking the hatch cover relative to the coaming; characterized in that the hatch cover comprises a main body having a domed shape, and the convex portion of the domed shape is facing the coaming when the hatch cover is in sealing connection with the coaming.

In one embodiment, the locking means comprises a plurality of peg members arranged around the coaming circumference, and a plurality of hook members arranged around the hatch cover circumference, and the hook members being configured for releasable engagement with respective peg members; and the hook members are rotatably supported by and connected to the hatch cover; and the hatch cover further comprises an actuation device for operating the hook members.

It is also provided a vent hatch device for a suction pile or similar, comprising a coaming configured for connection to an opening in said suction pile, a hatch cover configured for sealing connection with the coaming, and locking means for selectively locking and unlocking the hatch cover relative to the coaming; characterized in that the locking means comprises a plurality of peg members arranged around the coaming circumference, and a plurality of hook members arranged around the hatch cover circumference, and the hook members being configured for releasable engagement with respective peg members; and the hook members are rotatably supported by and connected to the hatch cover; and the hatch cover further comprises an actuation device for operating the hook members.

In one embodiment, a hook member is connected to the actuation device via a rotatable shaft, and the actuation device comprises a force transfer unit configured for rectilinear movement and connected to the shaft via a crank-and-pin connection, whereby a rectilinear movement of the force transfer unit results in a rotation of the shaft. The actuation device may comprise an interface element for operation by an ROV tool.

In one embodiment, a hook member is rotatably supported by and connected to the hatch cover via a shaft rotatably supported by at least a first support element connected to the hatch cover in the region of the hatch cover periphery.

In one embodiment, the hatch cover comprises a circumferential groove so arranged in the hatch cover as to be aligned with the coaming circumference, said groove being configured for accommodating a seal ring gasket, whereby the hatch cover forms a sealing connection with the coaming when the hatch cover is in a closed position.

9. The vent hatch device of claim 8, further comprising a seal ring gasket arranged in the groove and having an internal cavity and at least one bore extending through the seal ring gasket wall and into the cavity.

The hatch cover may be movably connected to the coaming via one or more hinges.

Brief description of the drawings

These and other characteristics of the invention will become clear from the following description of an embodiment, given as a non-restrictive example, with reference to the attached schematic drawings, wherein:

Figure 1 is a perspective view of an embodiment of the invented vent hatch in a closed but not locked state;

Figure 2 is a perspective view corresponding to that of figure 1, illustrating the invented vent hatch in a closed-and-locked state;

Figure 3 is an exploded view of the vent hatch illustrated in figure 1;

Figure 4 is a perspective view corresponding to that of figure 1, illustrating the invented vent hatch in a fully open state (only a part of the hatch cover illustrated);

Figure 5 corresponds to figure 4, and illustrates the invented vent hatch in an open state, with the hatch cover in an intermediate position;

Figure 6 is a close-up illustration approximately corresponding to the area A in figure 1, illustrating the hook position of maximum compressive force during locking and unlocking movement;

Figure 7 corresponds to figure 6, but illustrates the closed-and-locked state (corresponding to figure 2);

Figure 8 is a perspective cut-away drawing of a portion of the invented vent hatch in a closed-and-locked (corresponding to that of figure 2);

Figure 9 is a perspective cut-away drawing of a portion of the vent hatch (hatch cover in a closed position; actuation device removed);

Figure 10 is a close-up illustration approximately corresponding to the area B in figure 9; and

Figures 11a-c are schematic sectional drawings of the sealing ring gasket in a neutral, unbiased state (figure 11a), a state in which the gasket is subjected to internal positive pressure (figure 11b) and a state in which the gasket is subjected to internal vacuum (figure 11c).

Detailed description of an embodiment

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ”upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. Such terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

Referring initially to figures 1 and 2, the invented suction pile vent hatch compass in the illustrated embodiment a circular coaming 1 having a lower flange 23 for connection around a suction pile (not shown) opening as described above. The lower flange 23 is normally welded to the suction pile, and the coaming is thus preferably made of a carbon steel material.

The illustrated vent hatch comprises a circular hatch cover 2 which is attached to the coaming 1 via hinges 18. Locking means comprise a plurality of pegs or bollards 16 connected to, and protruding radially from, the coaming, and a corresponding number of rotatable hooks 11 connected to the hatch cover. In the illustrated embodiment, the locking means comprise four sets of hook-and-bollard, each set arranged 90º apart from the adjacent set. The skilled person will understand that this is an appropriate configuration, but the invention shall not be limited to four sets. Each hook 11 is mounted on a shaft 9 which is rotationally supported by a peripheral support element 24 and a central support 25. Each hook 11 is thus rotatable between an unlocked position (figure 1) and a locked position (figure 2). The rotation of the shaft 9, and thus the hook 11, is accomplished by an actuation device 26 connected to the hatch cover, preferably in the hatch cover center. The actuation device 26 comprises a conventional ROV interface and is configured such that the four shafts are rotated simultaneously and synchronously when the actuation device is operated. Referring additionally to figure 3 and figure 8, the actuation device 26 comprises in the illustrated embodiment a slotted pipe 3 connected to the hatch cover. A trapezoidal screw 7 (which is rotatable by an ROV) is connected via a nut 15 to a force transfer unit 5 which operates a crank 10 via a slot-and-pin connection. Rotation of the trapezoidal screw 7 thus moves the force transfer unit 5 linearly (here: vertically), and this linear motion is transferred to rotational motion of the shaft via the slot-and-pin connection and crank 10. The linear force in the force transfer unit 5 is thus transferred to torque in the shaft and hook. It can be seen from figures 1 and 2 that the force transfer unit 5 is in a lower position (near the hatch cover) when the hooks 11 are in the unlocked position, and has been moved to an upper position (away from the hatch cover) when the hooks 11 are in the locked position.

In the illustrated embodiment, the hatch cover 2 has a dome-shaped main body 27 connected to a circular rim 28 (see also figure 5 and figure 8). The main body and rim may be manufactured as separate items and welded together, or may be cast as one integral object. The hatch cover 2 is connected to the coaming 1 such that the convex side of the main body 27 is facing the coaming (and hence the opening in the suction pile). This is advantageous from an operational point of view, when the hatch cover is subjected to strong vacuum pressures. The hatch cover may thus be made slimmer and lighter than those of the prior art. In a practical application, the hatch cover may be subjected to pressures in the order of ± 10 barg, but the invention shall not be limited to this pressure range.

Another advantage of the dome-shaped hatch cover, is that the dome-shape effectively provides a recess for the actuation device 26 and consequently a vent hatch device which is lower (less tall) than those of the prior art.

Turning now to figure 6, it will be seen that the rotational shaft 9 and the corresponding bollard 16 are aligned along a generally vertical axis L when the hatch cover is in the closed position. Also, the hook 11 abutment face 33 (the portion of the hook which may abut against the bollard) is shaped such that is has a region P which is differently elevated than the adjacent portions of the abutment face 33. Figure 6 displays the hook position in which this elevated region P abuts against the bollard 16. This is the hook position which generates the maximum compressive force (indicated by arrow F) during a normal locking or unlocking operation. The compressive force is the force necessary to compress the seal ring gasket 30 (see i.a. figure 10; described below). When the hook is in the fully locked position, as shown in figure 7, and the hatch cover is not subjected to any pressure differentials, there is a small clearance C (see figure 8) between the abutment face 33 and the bollard 16, and the hook generates not compressive force on the bollard.

The hatch sealing system will now be described, initially with reference to figure 9 and figure 10. A ring seal groove 29 is arranged in the hatch cover rim 28. The groove comprises an extended portion 34 (bearing towards the hatch cover center), and a ring seal gasket 30 is arranged in the groove. The ring seal ring gasket 30 is made of a resilient material generally of a type which is known in the art. The ring seal ring gasket 30 comprises an inner cavity 31, extending in the entire ring seal gasket circumference. Referring now to figure 11a, the ring seal gasket 30 comprises at least one bore 32 whereby the inner cavity 31 is vented to the outside and may be subjected to ambient fluid pressures (gas, liquids). Although not illustrated, it should be understood that the ring seal gasket 30 may comprise several such bores 32, arranged at suitable intervals around the ring seal gasket circumference.

Figure 10 and figure 11a illustrate the hatch cover in a closed, locked, but unbiased position. The ring seal ring gasket 30 is in an non-deformed state. Figure 11b illustrates a situation in which there is positive pressure (p+) inside the coaming and hatch cover, and the ring seal gasket 30 is forced towards the peripheral side (outer side) of the hatch cover rim 28. Figure 11c illustrates a situation in which there is vacuum (p-) inside the coaming and hatch cover, and the ring seal gasket 30 is forced towards the center (inwards) of the hatch cover rim 28, partly occupying the extended portion 34. The bore (or bores) 32 ensures that the pressure inside the cavity 31 at all times is equalized with the external fluid pressure. It should be understood that the seal ring gasket 30 may be replaced by other gasket types.

The invented vent hatch device is easy to operate and requires less force to lock and unlock than the prior art devices, because the rotation of the shafts 9 and hooks 11 need only overcome the stiffness in the seal ring gasket. The ring seal gasket bores also contribute to lowering the force required to move the hooks, as they will enhance the ring seal gasket’s compressibility. The trapezoidal screw 7 (operating the nut 15) will therefore be exposed to lesser thread pressure and be easier to rotate.

The short distance d (see figure 8) between the hook-and-bollard coupling and the shaft peripheral support element 24 amounts to a short moment-arm, which also contributes to a lighter and leaner device without compromising strength.

Although the invention has been illustrated as having a circular coaming and cover, the invention shall not be limited to such geometry.

Although the invention has been described with reference to a suction pile, it should be understood that the invention is equally applicable for use on suction anchors, suction caissons and suction buckets, as well as other seabed foundation devices that utilize a similar suction principle.

Claims

1. A vent hatch device for a suction pile or similar, comprising

- a coaming (1) configured for connection to an opening in said suction pile,

- a hatch cover (2) configured for sealing connection with the coaming (1), and - locking means (11, 16) for selectively locking and unlocking the hatch cover relative to the coaming;

characterized in that

the hatch cover (2) comprises a main body (27) having a domed shape, and the convex portion of the domed shape is facing the coaming (1) when the hatch cover is in sealing connection with the coaming.

2. The vent hatch device of claim 1, wherein the locking means comprises a plurality of peg members (16) arranged around the coaming circumference, and a plurality of hook members (11) arranged around the hatch cover circumference, and the hook members being configured for releasable engagement with respective peg members; and the hook members are rotatably supported by and connected to the hatch cover; and the hatch cover further comprises an actuation device (26) for operating the hook members.

3. A vent hatch device for a suction pile or similar, comprising

- a coaming (1) configured for connection to an opening in said suction pile,

characterized in that

the locking means comprises

- a plurality of peg members (16) arranged around the coaming circumference, and - a plurality of hook members (11) arranged around the hatch cover circumference, and - the hook members being configured for releasable engagement with respective peg members; and

- the hook members are rotatably supported by and connected to the hatch cover; and the hatch cover further comprises an actuation device (26) for operating the hook members.

4. The vent hatch device of claim 3, wherein the hatch cover (2) comprises a main body (27) having a domed shape, and the convex portion of the domed shape is facing the coaming (1) when the hatch cover is in sealing connection with the coaming.

5. The vent hatch device of any one of claims 3 and 4, wherein a hook member (11) is connected to the actuation device (26) via a rotatable shaft (9), and the actuation device (26) comprises a force transfer unit (5) configured for rectilinear movement and connected to the shaft via a crank-and-pin connection, whereby a rectilinear movement of the force transfer unit results in a rotation of the shaft.

6. The vent hatch device of any one of claims 3-5, wherein the actuation device (26) comprises an interface element (7) for operation by an ROV tool.

7. The vent hatch device of any one of claims 3-6, wherein a hook member is rotatably supported by and connected to the hatch cover via a shaft (9) rotatably supported by at least a first support element (24) connected to the hatch cover in the region of the hatch cover periphery.

8. The vent hatch device of any one of claims 1-7, wherein the hatch cover comprises a circumferential groove (29) so arranged in the hatch cover as to be aligned with the coaming circumference, said groove being configured for accommodating a seal ring gasket (30), whereby the hatch cover forms a sealing connection with the coaming when the hatch cover is in a closed position.

9. The vent hatch device of claim 8, further comprising a seal ring gasket (30) arranged in the groove and having an internal cavity (31) and at least one bore (32) extending through the seal ring gasket wall and into the cavity.

10. The vent hatch device of any one of claims 1-9, wherein the hatch cover (2) is movably connected to the coaming (1) via one or more hinges (18).