GB2628461A - Advanced controlled flow excavation system designs - Google Patents

Abstract

A first aspect is a controlled flow excavation system (CFE) for subsea operations. The CFE has multiple individual excavating tools 11, 12 in which the outputs of at least two of the tools are arranged to operate as a linked team and that each of the tools is electrically driven. A second aspect relates to a CFE with multiple individual excavating tools in which at least two of the tools are arranged to operate as a linked team. There are means whereby the relative angle or position of the tools in the team, such as the relative orientation along mutually perpendicular respective X and Y axes - can be altered whilst the tools are in their original in situ subsea operational position. A third aspect relates to a CFE with multiple individual excavating tools in which at least two of the tools are arranged to operate as a linked team. The tools can have their relative angle or position altered by an operator of the team whilst remaining in the same plane as one another. There are means enabling the relative angle or position of the tools in the team to be altered so as to occupy a plane different than the plane first referred to.

Description

ADVANCED CONTROLLED FLOW EXCAVATION SYSTEM DESIGNS

Field of the Invention

The invention relates to controlled flow excavation systems and lends itself by way of exemplary embodiment to such systems adapted and intended for use in subsea operations where, for example, trenches need to be dug in the seabed to accommodate pipes, cables and the like.

Review of Art Currently Known to the Applicant Controlled flow excavation systems ("CFEs") for subsea operations are well known.

Broadly speaking, they consist conventionally of one or (more usually) two power driven motor units whose individual motors generate a pressurised and relatively concentrated output stream of fluid via internal vanes and impellers so as to blast soil away from the seabed and form a trench as the CFE unit is moved along the seabed. They can also be used for other mass movement of seabed soil in a given direction, for other purposes, but the trench-creating illustration is most easily understood and will be used in the disclosure which now follows.

Typically, when a trench is excavated in the seabed, soil is removed as the trench is created and that soil is deposited alongside the trench in large banks ("berms" in industry parlance). Once the cable or pipeline has been positioned in the bottom of the thus-created trench, it requires covering and the most cost-effective method of doing this is clearly to replace the excavated material back into the trench by using the blasting_ power of the CFE unit to shill it, effectively, back where it came from.

Such techniques are well known in themselves, and a number of previously published patent applications by operators currently in this field of activity exists. They confirm the standard approach, namely, to use (usually) two separately mounted excavation tools, each comprising a respective motor driving the surrounding water via a vane/impeller array housed in a "can" (conventionally speaking) to literally blast the soil in the berm hack into the trench.

The intended skilled reader of this present specification will know the techniques currently used in this specialised field. One previously published document embodying current thinking is GB patent No. 2576978B granted to Rotech Group Limited and initially published on 11 March 2020. The disclosure of that prior published document is extensive, as are the drawings forming part of that same disclosure (there are no less than 18 sheets of them) and figures 10 through 16 inclusive of those same drawings illustrate a system whose twin-tools are linked to give a combined output; and the motors driving the respective ones of those twin-tools are hydraulically powered.

Hydraulically powered twin-tool arrangements of the kind described and illustrated in GB2576978B have obvious advantages in use, in that their output is maximised at the point of impact with the seabed. They also, however, have drawbacks. If, for example, the twin-tool Cl-L" system is to be used for excavating the seabed around an existing pipe (in order to remove it and replace it with another or a larger one), then a twin tool system of the kind under discussion in GB2576978B will tend to 'hit' the pipe; whereas what is needed is for the blast output of the system to hit the area surrounding the sides of the pipe.

A hydraulically driven system can have its tools angled, to a limited extent, but it is difficult to control the output because the hydraulic supply and drive apparatus required is relatively cumbersome. Nevertheless, the power output advantages of the hydraulically driven twin-tool system have so far overridden its drawbacks. And whilst electrically driven CFE tools do exist, all twin-tool systems currently known to the applicant have been hydraulically driven to date.

CFE tools driven by an electric motor are relatively large and cumbersome in themselves. Conventional electric motor design tends to make the system noticeably top heavy and hence the entire subsea unit becomes too large and cumbersome to he of practical use.

Modern motor design, however, has recently developed shorter squatter electrical units capable of much the same or even better power output when compared with their hydraulic equivalent -yet the industry sticks to its "twin-tools arc hydraulic-only" thinking The Extent of the Invention The inventive concept now disclosed takes this continuing tradition-bound industry thinking and changes it by incorporating recent developments to give a number of new and non-obvious inventive results. They are new, literally, as far as the applicant is aware.

They arc also inventive because as has been outlined above, the industry, despite it having several well-known proponents, and being of primary and continuing importance in itself, has shown no tendency to he motivated to change the current well developed hydraulically driven systems.

In a first broad aspect, therefore, the invention is embodied in a controlled flow excavation system for subsea operations in which there are provided multiple individual excavating tools and in which the outputs of at least two of the tools are arranged to operate as a linked team, in use characterised in that each of the tools of such a team is electrically driven.

With appropriate electric motor design, now currently available from specialist suppliers, this can be achieved and whilst impcllor/propellor design is of course of major importance, this is a given and can he supplied as part of the overall design process following the decision to adopt electric power.

Such a departure from conventional thinking leads to a further aspect of the invention whereby means are provided to alter the operational angle and/or or the operational position of each tool relative to the other tool in the team. Any thought of using electrical power for the driving motor of such a tool has made it awkward if not practically impossible to have individually orientatable tool movements because of the conventional electric motor size and weight problems outlined above. With new and currently available designs for this purpose, however, the versatility given by adjustable twin-tools can now he embraced.

In particular, the invention makes it possible for the relative orientation of the tools in the team to be altered whilst the tools arc in their in situ subsea operational position; or other than in that position, for example when they system is being set up, altered, and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.

For a twin-tool electrically powered CFE system to work efficiently, the output of the tools must be kept within a small percentage of one another. This is relatively easy in a conventional hydraulic system, but historically has been difficult in an electrically driven system. Any drive system takes up considerable space on the deck of a vessel carrying or controlling the system, for example, and so using two drive containers would prove inefficient and unattractive in reality.

In a further development of the invention, therefore, the tools are controlled in use via one overall operator-controlled system, which is adapted to allow an operator of the team to balance the outputs of those tools evenly. The decision to use electrically driven tools makes it possible to use one variable frequency drive (VFD') to control the two motors when the system is submerged by balancing the output flows using a single electric control source.

In yet a further development of the invention, again flowing directly from the decision to use electrical drive power for the twin-tools of the system, means arc provided whereby the output of -in particular, the power supply tool -the tools in the team can readily be uncoupled whilst the tools are in their in situ subsea operational position; or whilst in a position other than that operational position, for example when the system is being set up, altered and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.

In a development linked directly to the one outlined immediately above, the power supply to one electrically driven tool can selectively he readily uncoupled once the tools are in their in situ subsea operational position; or whilst they are in anyone of the alternative positions envisaged in that same immediately preceding paragraph.

This has immediate apparent advantages from a timescale to mobilise' standpoint, saving several hours in practical conditions of set up time on the deck of the vessel from which the system in use is controlled. Whilst quick release electrical systems arc not uncommon in the industry generally, their use is unheard of in a 0-±, application.

The invention, as has been disclosed above, is concerned broadly with improvements in the 20 field of controlled flow excavation systems for subsea operations in which there arc provided multiple individual excavating tools and in which the outputs of at least two of the tools are arranged to operate as a linked team in use.

Such a system will he referred to from now onwards as a system "of the kind defined".

In further developments of the invention flowing from the concepts outlined above, a system of the kind defined and in which the tools of the linked team can have their relative angle or position altered by an operator of the team whilst remaining, in all relative operational positions, in substantially the same plane as one another, is characterised by the provision of means enabling the relative angle or position of the tools in the team to he altered so as to occupy, in use, a plane or planes other than the plane first referred to.

Such a system may also he characterised by the provision of means whereby the operator can direct the outputs of the tools to issue in substantially parallel streams.

It may also he characterised advantageously by the provision of means whereby one or both tools can have its relative angle or position altered whilst the or each tool is in its in situ subsea operational position; and/or whilst the tool is in a position other than its in situ subsea operational position, for example when the tool is being set up, altered, and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.

All these are further aspects of the invention flowing, with operational advantage, from the essential insight to use for the first time in this industry an electrical power source to drive the outputs of both tools of a twin-tool operationally linked system.

Brief Description of the Drawings

In the single sheet of the accompanying drawings: Figure 1 shows the essential features of a conventional CFE system; Figure 2 shows the system of Figure 1 with its twin tools in an alternative relative orientation; and Figure 3 shows a design embodying, by way of example only, one form that a CFE system 25 embodying the invention might take.

Description of the Preferred Embodiment

Conventional thinking in the industry under discussion, as shown in Figures 1 and 2 and as outlined in the text above, has respective blast-generating tools 11, 12 each mounted within and carried on an operating framework 13 which in use is suspended via lifting eyes referenced respectively 14, 15, 16, 17 on chains (not shown) which extend from a common gantry output mechanism to raise and lower the unit from the seabed.

Each tool 11, 12 comprises essentially a motor 18, 19 driving a respective "can" 20, 21 to generate the power driven blast output of the tool in use. As Figure 1 and Figure 2 show in sequence, conventionally the tools can be swivelled so as to operate for example with each tool pointing downwards towards the seabed (Figure 1) or with each of them angled relative to the other (Figure 2). The means by which the individual tools can swivel on the framework, and indeed the means by which each of them generates its blast output to move the seawater around it under pressure, can he conventional and the intended skilled addressee of this specification needs no further tuition in that respect.

The twin-tool system exemplified in Figures 1 and 2 has worked well, as compared to one using just a single tool, to date. But hitherto the movement of the individual tools as Figures 1 and 2 illustrate has always been restricted to movements of the tools in the same plane as one another. In Figures 1 and 2 the tools move, as shown, in the same vertical plane as one another, and whilst the Figure 1 arrangement is convenient for transport, for example, the Figure 2 orientation allows both tools to he focussed on the same spot for blasting purposes. Whatever relative orientation is chosen, however, the plane of movement is the only one available within these conventional designs.

The Figure 3 arrangement, by contrast, enables both tools 11, 12 to occupy, in use, a plane or planes other than the vertical plane to which the tools of Figures 1 and 2 are restricted; by so arranging matters that the Figure 3 tools can swivel about the horizontal axis which spans them across the frame 13. In one embodiment of the Figure 3 invention, one tool 11 could swivel Lo a position in which it is angled at an angle differing from that of the other tool 12. As shown, however, both tools 12, 13 in Figure 3 occupy essentially the same notional plane and the advantages flowing from this include a potentially much greater rate of soil movement, more efficiency, greater production rates during backfil ling of the berms into the trench, and much better handling of soil movement in general.

This is made possible by the decision to replace the conventional hydraulic motors 18, 19 with electric ones which arc now available in a form which the skilled designer can incorporate, without necessarily having to exercise unduly inventive thinking, into this twin-tool design of unit. One such motor design, proven in non-public tests of apparatus incorporating it by the Applicants, was sourced from Submersible Motor Engineering of 9 Ryelane Street, Maddington WA6109, Australia. That source is identified by way of example only, but its very availability at the relevant time highlights the refusal of the CFE industry to shift from its traditional (and indeed, ironically, entrenched) hydraulic-only design constraints.

The reader will appreciate that when we say "plane" in the context of this present disclosure, we use the term accurately but broadly and not in any literal geometric sense. The tools 11, 12 of course are not planar but three-dimensional. The axes about which each of them is symmetrically constructed, however, do occupy a literal plane and it is in this context that we describe them as being able, in a system embodying the invention, to occupy a plane or planes other than the conventional and nominally vertical (with reference to Figures 1 and 2) one so far used by this particular industry.

The reader will also appreciate that, whilst Figure 3 of the drawings illustrates (like Figures 1 and 2) units of relatively conventional exterior dimensions in relation to motors 18, 19 it is, literally, illustrative of the principle rather than attempting to give any indication to the reader of the dimensions which the newly available electric motors might embody. The intended skilled addressee, now the invention has been revealed, would he able to design appropriately dimensioned electrically driven tools from within his or her or their existing developed knowledge base.

The scope of the invention is defined in the claims which follow.

Claims (13)

1. Claims 1. A controlled flow excavation system for subsea operations in which there are provided multiple individual excavating tools and in which the outputs of at least two of the tools are arranged to operate as a linked team, in use, characterised in that each of the tools of such a team is electrically driven.
2. 2. A system according to Claim 1 characterised in that means are provided whereby the operational angle and/or the operational position of each tool relative to the other tool in the team can he altered.
3. 3. A controlled flow excavation system for subsea operations in which there are provided multiple individual excavating tools and in which at least two of the tools are arranged to be operated as a linked team, in use, characterised by the provision of means whereby the relative angle or position of the tools in the team -in particular, but not exclusively, the relative orientation of the tools along mutually perpendicular respective X and Y axes -can be altered whilst the tools are in their in situ subsea operational position.
4. 4. A system according to Claim 1 or Claim 2 and characterised by the provision of means whereby the relative angle or position of the tools can be altered when the system is in a position other than its in situ subsea operational position, for example when the system is being set up, altered, and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.
5. 5. A system according to any preceding claim and characterised in that some at least of the tools are controlled, in use, via one overall operator controlled system which is adapted to allow an operator of the team to balance the outputs of those tools evenly via a single electric control source.
6. 6. A system according to any preceding claim and characterised by the provision of means whereby the output of, in particular the power supply to, the tools in a linked team can readily be uncoupled whilst the tools are in their in situ subsea operational position. I0
7. 7. A system according to any of Claims 1 to 5 and characterised by the provision of means whereby the output of, in particular the power supply to, a linked team of tools can readily he uncoupled whilst the tools are in a position other than their in situ subsea operational position, for example when the system is being set up, altered and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.
8. 8. A system of the kind defined herein, characterised by the provision of means whereby the output of, in particular the power supply to, one electrically driven tool can selectively he readily uncoupled whilst the tools are in their in situ subsea operational position.
9. 9. A system of the kind defined herein, characterised by the provision of means whereby the output of, in particular the power supply to, one electrically driven tool can selectively he readily uncoupled whilst the tools are in a position other than their in situ subsea operational position, for example when the system is being set up, altered and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.
10. 10. A controlled Row excavation system for subsea operations of the kind in which there are provided multiple individual excavating tools and in which at least two of the tools are arranged to he operated as a linked team whose tools can have their relative angle or position altered by an operator of the team whilst remaining, in all relative operational positions, in substantially the same plane as one another characterised by the provision of means enabling the relative angle or position of the tools in the team to be altered so as to occupy, in use, a plane or planes other than the plane first referred to.
11. 11. A system of the kind defined herein characterised by means whereby the operator can direct the outputs of the tools to issue in substantially parallel streams. 1I
12. 12. A system of the kind defined herein characterised by the provision of means whereby one or both tools can have its relative angle or position altered whilst the or each tool is in its in situ subsea operational position.
13. 13. A system of the kind defined herein characterised by the provision of means whereby the or each tool can have its relative angle or position altered whilst the tool is in a position other than its in situ subsea operational position, for example when the tool is being set up, altered, and/or serviced above or adjacent the seabed or on or above or adjacent the deck of a vessel carrying or controlling the system in operation.