1 The present invention relates to a process for maintaining and cleaning the outer surfaces of con¬ struction members in a rig construction at sea, especially for tlte removal and prevention of marine overgrowth on said outer surfaces.

The invention also relates to an apparatus for carrying out the process according to the invention, for maintaining and cleaning the outer surfaces of construction members in a rig construction at sea, especially for the removal and prevention of marine overgrowth on said outer surfaces.

With the present invention the objective is respectively an intermittently acting and a more or less continuousiyji acting solution for the prevention and removal of marine overgrowth on the outer surfaces of construction members in a rig construction. In other words the aim is an assembling of equipment or an apparatus which has the task ^' of keeping the outer surface of the construction member clean, that is to say free of marine overgrowth, so that the outer surface of the construction member can maintain the original outer coating as far as possible intact and unaffected by the surroundings. With the present invention the aim is a maintenance or a cleaning where one is not dependent upon direct contact between outer surfaces of the construction meirfa-er and the maintenance or cleaning equipment in order to keep the outer sur¬ faces clean and in order to remove attached mariner ver- growth respectively. ^' It has been found according to the invention that such maintenance or such cleaning can be achieved in an easy and simple manner by enclosing the construction member which is to be maintained totally or partially by a lattice work at a certain distance from the outer surface of the construction member, the lattice work being subjected respectively to a forwards and back-

wards and an upwards and downwards movement in the sea at a certain moderate distance from the construction member.

According to the invention it is found that the 5 relative movement between the construction member and the lattice work;- which causes a certain positive flow of fluid between the lattice work and the construction member, is sufficient to respectively maintain and clean the construction member in use. Tests have shown 0 that it is possible by using the lattice work on an already overgrown construction member to remove the overgrowth and thereby clean the construction member, solely by such relative movement between the lattice work and the construction member without necessary 5 contact between the lattice work and the construction member, The process according to the invention can therefore be carried out in a manner which does not necessarily involve wear and tear on the construction member or on the lattice work, at the same time as the Q lattice work can be allowed to move relatively freely relative to the construction member guided along the latter.

An especially simple solution is obtained by allowing the lattice work to be subjected to a movement 5 caused by wave movements of the sea and tidal movements of the sea respectively, the movements of the lattice work being determined by buoyancy means (floats) in the lattice work. In this way one can bring about without the use of extra power or extra control a Q movement controlled by movements of the sea, that is to first and foremost by vertical wave movements of the sea and tidal movements.

An apparatus for carrying out the process is characterised in that it consists of a lattice work 5 comprising a set of arcuate ring-shaped elements and a set of longitudinal connecting elements together with connection components for coupling together the ring-

forming elements and the longitudinal elements into a coherent unit, and that the"lattice work is provided with means for moving the lattice work to and fro along the construction member at a certain moderate distance from the outer surface of the construction member and with a length of ^' -movement at least equivalent to the distance between the arcuate ring-shaped elements.

By allowing the lattice work according to the invention to consist of various elements of arcuate annular form there is the possibility of permitting the lattice work to surround the construction member wholly or partially at a particular distance from the latter, depending upon the cross-sectional form of the construction member. By allowing the elements to have an arcuate annular contour the elements can be made to surround the periphery of the construction member and simultaneously ensure a control of the lattice work relative to the construction member together with adapting to a definite, moderate distance between the lattice work and the construction member. By employing longitudinal elements in connection with the arcuate ring-shaped elements the distance between the arcuate ring-shaped members can be adjusted so that the outer surface of the construction member is totally or sub- stantially totally covered by the movement of the arcuate ring-shaped elements along the construction member.

It is preferred that the lattice work is provided __with buoyancy members (floats) or that certain parts of the lattice work constitute buoyancy members.

It is possible for example to fasten floats to the upper portion of the lattice work and to allow the remainder of the lattice work to hang freely down¬ wards from the under side of the buoyancy member or members with a certain weight loading from the lattice work itself. It is also possible to allow the buoyancy members to become an integral part of certain parts of

the lattice work, such as the arcuate elements or certain of the arcuate elements, while remaining parts, especially the connection components, can serve as weight parts of the lattice work. Further features of the invention will be evident from the ^'■ following description having regard to the accompanying drawings, in which:

Fig. 1 shows the lattice work used on a rig con¬ struction, seen from the side, and shown in two outer positions by broken and full lines.

Fig. 2 shows a section of a lattice work according to the invention, illustrated by a portion within upper and lower ends of the lattice work. Fig. 3 shows a connection component for the elements of the lattice work, illustrated with certain portions in section.

Fig. 4 shows a section of the lattice work according to the invention, illustrated at the upper end of the lattice work. Fig. 5 shows a detail of the lattice work where a pipe or hose member is surrounded by a separate brush member.

In Fig. 1 there is shown a lattice work 10 arranged on the one construction member 11 in a rig construction 12,which supports itself against the sea bottom 13. The upper level of the sea has a wave out¬ line as shown at 14.

The lattice work 10 is illustrated in the embodi¬ ment shown in two outer positions, that is to say an upper position is shown in full lines, and a lower position is shown in broken lines. The lattice work 10 is moveable between the illustrated outer positions by means of the movements of the sea, which in the illustrated embodiment are constituted by the sea's wave movements. Alternatively or in addition the sea's movements can be produced by tidal movements of the sea, something which is especially the case in rig con-

structions which rest on the sea bottom. In the illu¬ strated embodiment there are employed extra buoyancy means in the form of a pair or some few floats 15 fastened to the upper edge of the lattice work. The floats 15 can be rigidly fastened to the lattice work 10, but are -preferably suspended to pivot freely on a fastening at the upper edge of the lattice work 10, so that the floats can be subjected to a certain pivotal movement to and fro along the surface of the sea relative to the lattice work, at the same time as the floats 15 supply the lattice work with extra buoyancy which raises and lowers the lattice work in step with the movements of the waves in a vertical direction. In addition or if necessary alternatively parts of the lattice work or certain parts of the lattice work constitute buoyancy bodies of the lattice work, that is to say certain parts of the lattice work can for example be filled with air or filled with buoyancy medium, while remaining parts of the lattice work can be filled with sea water or another weight-forming medium.

If desired the lattice work 10 can in the one outer position be- suspended or fixed by means of a fastening line (not shown) in order to restrict move¬ ment of the lattice work in the one direction of move¬ ment.

Practical tests have shown that movements of the lattice work - in step with movements of the sea - over a certain period of time have involved the removal of marine overgrowth which has already commenced from that portion 11 of the rig construction which extends closely up to the lattice work and which is overlapped by movements of the lattice work. In addition it has been found that existing -marine overgrowth on con¬ struction members 11a and lib, which extend up to the construction member covered by the lattice work, is

also removed as a side effect of the removal of marine overgrowth from the construction member 11 covered by ^" the lattice work 10.

It has been found that the flow movement which is caused between the moveable lattice work 10 relative to the construction member 11 creates poor growth conditions for marine overgrowth. The result is that additional new overgrowth is prevented, at the same time as overgrowth which has already commenced is re- moved. All according to desire and need one dan use the lattice work as a continuous protection for the various members of the rig construction or as an intermittently acting protection for the same.

- The lattice work in the illustrated embodiment is fabricated from a series of arcuate.. ring-shaped members 16 which are disposed at suitable distances from each other in the axial direction of the lattice work together with a pair or a number of longitudinal connecting elements 17 which connect the arcuate ring ele- ments 16 to each other. The arcuate ring members 16 can be made having arbitrary lengths and having arbi¬ trary arcuate outlines, adapted according to indivi¬ dual modes of use, that is to say depending upon the diameter and/or the shape of the _construction member which is to be maintained ^' or cleaned. In the illu¬ strated embodiment of Fig. 1 there are used three arcuate ring elements 16, which together surround the whole periphery of the construction member 11, while in Fig. 2 there is shown an alternative embodi- ment having two arcuate ring elements 16 which surround the construction member. In Fig. 1 there are omitted in certain segments (at junction points 18) of the lattice work 10 the one of the three sections or elements 16 to form a C-shaped arcuate ring outline, so that the lattice work 10 in such segments can pass unhindered a junction point 18 between several con¬ struction members 11 and 11a, lib respectively.

Arcuate ring elements 16 and connecting elements 17 are shown in the form of plastic pipes or plastic hoses, preferably made of nylon which is especially resistant to ultra violet light, heat, oil, chemicals and sea water having different salt contents.

The elements 16 and 17 are connected to each other via junction point-forming connection components 19, which in Fig. 3 are illustrated having four sleeve- shaped fastening pins 20, which project outwardly from a common housing member 21 having through bores. One end 20a of the fastening pins 20 can be provided with external threads which cooperate with corresponding internal threads of the housing member 21, while freely outwardly projecting ends 20b of the fastening pins can be provided with tensioning means 22, 23 for fixing the elements 16 and 17 each on its respective fastening pii . Alternatively the pins 20 can be connected to the housing member 21 via rapid coupling devices (not shown further) . In ^' Fig. 3 there are shown tensioning means 22 in the form of an annular series of inverted wedge-shaped gripping fingers, which to¬ gether with the pin end 20b disposed radially within define a gap 24 for the reception of the end portion of an element 16 or 17. By means of a clamp sleeve 23 which is axially moveable on the pin 20 one can grip into position the gripping fingers 22 in an effective fastening grip with the equivalent end portion of the element 16 or 17. Alternatively the elements 16 or 17 • can be provided with permanently secured rapid coupling members which replace the pins 20.

The housing member 21 of the connection component

10 can be made for example of polypropylene, while the pins 20 with associated gripping fingers 22 and clamp sleeve 23 can be made of nylon with an outer layer of PVC plastic.

The afore-mentioned example can be given diffe¬ rent practical designs and be made of various other

materials than described, as required, for example depending upon the temperature conditions, salt content and the like at the location of use.

The illustrated connection components 19 can if necessary be used for correspondingly fastening a sleeve stump on a float 15 to the lattice work 10.

In Fig. 4 there is shown a solution where the housing member 21a of the connection component 19 is provided with a fastening pin 25 for fixing a float 15. In addition there is shown an outlet 26 which passes across bores of the housing member 21a for the pins 20.In the outlet there is inserted a valve-forming sealing plug 27 having a rapid coupling connection to the housing member. Equivalent sealing plugs can be used at all the locations in the lattice work where elements 16 and 17 are excluded, for example at the lower end of the lattice work. To the plug 27 there can be coupled as indicated by broken lines 28 a pressure hose with associated rapid coupling. The hose 28 is connected to a pump 29 which via a supply conduit 30 is supplied with hydraulic oil or another weight-forming or buoyancy means-forming fluid from a supply 31. After the lattice work is put into position at the location of use, one takes care to fill the lattice work with pressure fluid, so that a favorable reinforcement is obtained on stretching out or extending different elements 16 and 17 of the lattice work with pressure fluid. By adapting the specific- gravity of the fluid for the purpose there ^" can be obtained a neutral buoyancy condition on the lattice work, and thereby the buoyancy of the whole lattice work can be easily controlled with a moderate buoyancy force in the floats 15.

In Fig. 5 there is shown a brush member 32 con- sisting of a sleeve member 33 split up longitudinally to which bristles 34 are fastened in groups. The brush member 32 is adapted to be fastened to an associated

arcuate ring element 16. As a consequence of the curvature of the element 16 in the longitudinal direction the member 32 is prevented from turning unintentionally on the element 16, but can be adjusted into different positions on the element 16 as required.