US3739971A

US3739971A - Piping tensioning device

Info

Publication number: US3739971A
Application number: US00132514A
Authority: US
Inventors: A Silvestri; G Gargatagli
Original assignee: Saipem SpA
Current assignee: Saipem SpA
Priority date: 1970-04-09
Filing date: 1971-04-08
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19
Also published as: GB1291677A; NL7104649A; NL165270B; FR2089215A5; NL165270C

Abstract

Device for laying piping columns under a pre-fixed constant stretch, permitting laying pipe in the sea at substantial depths, comprising means for tightening between them the pipe to be launched, control and vertical guide means for bringing the tightening means into contact with the pipe and for applying a frictional force, and actuating means for running the tightening means horizontally to exert traction on the piping column, the tightening means being characterized in having two long opposite tracks running on sliding rolls and supported by sliding blocks which are hinged so as to adjust the tracks to conform to the pipe and rubber coated curved, pipe-conforming saddles attached to the tracks.

Description

United States Patent 1191 Silvestri et al.

[ PIPING TENSIONING DEVICE [75] Inventors: Antonio Silvestri, San Donato Milanese; Guglielmo Gargatagli, Milan, both of Italy [30] Foreign Application Priority Data June 19, 1973 2,797,798 7/1957 Hallden 2. 226/172 Primary Examiner-Allen N. Knowles Attorney-Ralph M. Watson [57] ABSTRACT Device for laying piping columns under a pre-fixed constant stretch, permitting laying pipe in the sea at substantial depths, comprising means for tightening between them the pipe to be launched, control and vertical guide means for bringing the tightening means into 3081 70 Apr 1970 2 A/ contact with the pipe and for applying a frictional 52 U.S. Cl 226/172, 226/173, 226/195 and actuating means for running the tightening 51 lm. c1 B65h 17/34 means hmimmany exert the Piping [58] Field of Search 226/172, 173, 195; P the tightening P being h i i y g I 61/716 mg two long opposite tracks running on shdmg rolls and supported by sliding blocks which are hinged so as 56] References Cited to atdjlst the tgacks to coigforrn to thgdpipe 231d lrlugbfr coa e cur e p1pe-con ormmg sa es a ac e 0 UNITED STATES PATENTS the tracks 3,024,956 3/1962 Gretter 226/172 X 3,285,485 1 1/1966 Slator 226/172 11 Claims, 4 Drawing Figures PAIENIED 9 mums mvnw'rons U10 GARGATAGLI Ammo suvrsrm g cums PIPING TENSIONING DEVICE The present invention relates to a device for tensioning pipings and more particularly to a device which, by keeping a piping column under a prefixed constant stretch, allows the laying in the sea at noticeable depths.

It is known indeed that, during the laying in the sea, the pipes tend, under their own weight, to bend and may reach such bending radii to compromise the elastic stability, exceeding the yield point, typical of the pipings. Therefore in order to make possible the laying, it is necessary to maintain the abovementioned bending radii always higher than a prefixed limit and this is reached by means of a tensioning force, which, secured to the work pontoon, keeps tight by friction the pipe of the piping column, by subjecting in such a way all the column to a such prefixed constant stretch to warrant the elastic balance of the column self.

The piping column under tension shall be launched in the sea or recovered on the work pontoon according to whether the stretch developed by the movers of the pontoon self be respectively higher or lower than that exerted by the above-mentioned tensioning device.

Now, according to the prior art, the tensioning device consists substantially of two opposed series of tensioning rollers employed to tighten between them the pipe of the piping column with such a force to warrant the necessary friction. All the rollers of each series are pivoted on a unique horizontal rigid bar in such a way that it is sufficient to move vertically said bar to cause all the rollers to fit themselves simultaneously to the different sizes of the pipes to be tightened. On the other hand, as it is well known, the piping column to be launched is very often provided with a cement sheath and this entails therefore the two-fold requirement to be compelled to realize by means of the abovementioned opposed series of tensioning rollers a noticeable tightening force with an elevated friction coefficient by keeping however moderate the specific pressure on the pipe in order that the concrete be not cracked.

At this purpose all the tensioning rollers are lined with a gummy material or the like having a hollow of the same diameter as the pipe to be tightened. In such a way, indeed, the gummy coating, besides to increase the friction, for its intrinsic nature, is no more in touch with the pipe only along the generatrix of this, but along a rather wide arc of circumference and, i.e., along the relatively large contact surface represented by the above-mentioned hollow, with subsequent low specific pressure on the pipe. Such a tensioning device, known in the art, presents many drawbacks both of practical and operative nature and of economic nature. Above all said device does not allow to lay in the sea the pipings also at elevated depths.

As a matter of fact when a piping column is launched on a sounding very deep, it tends to arrange according to a catenary which presents itself arcuated also in correspondence to the tightening zone, due to the tensioning device. Therefore, to be able to effect a laying at noticeable depth, it is necessary to tighten the pipe of the column by maintaining its original curvature. By making use of the tensioning device, known to the art, said pipe on the contrary is pressed and tightened horizontally by the rollers pivoted on rigid horizontal bars and this should have as a consequence the inflection of the piping column at the outlet from said device with a not admissible bending radius.

Beside this operative restriction of the known device, it must take into account that the already mentioned concrete coating is not complete on all the column of pipings but we have so many cement sheathings separated by interspaces free of sheathing in correspondence of the junctions of the pipes. In correspondence of said interspaces, the tensioning rollers of the tensioning device known in the art should not be able to effect such a tightness of the pipe to warrant the necessary friction. To obviate, indeed, this drawback, the abovementioned interspaces are previously filled with suitable coatings which besides entailing an additional work represents also an economic burden.

On the other hand, as the same tensioning device must be suitable to the laying in the sea of pipings having deifferent diameters, ranging; in practice from 200 mm to 1500 mm, it is evident that in the case of the tensioning device known in the art it is necessary to arrange so many gummy coatings presenting a hollow having the same diameter of the pipe to be tightened as the possible diameter of the pipes selves. Because each of said gummy coatings costs very much, it derives con sequently an additional noticeable economic burden.

The object of the present invention is the elimination of the above-mentioned drawbacks and the realization of a tensioning device which allows the laying in the sea of pipings also at noticeable depths and without previous adjustments of the piping column. This is practically achieved by adopting as tightening element of the pipe of the piping column, two long opposed tracks whose catenaries, rather than on a rigid horizontal bar, run, according to a feature of the invention, each on several sliding blocks hinged and adjustable which allow to approximate with a broken line, the curvature of the pipe. In this way, for what previously said, the tensioning device allows to effect the laying in the sea also at noticeable depths and, moreover, because of the considerable length of the tracks, the practical and eco' nomic drawback of being obliged previously to adopt the piping column by shutting its interspaces free of cement sheathing is avoided.

Another characteristic of the invention is then given by the fact that to the track links are fixed some saddles in welded plates presenting each a curved surface of the same diameter of the pipe to be tightened and equipped with a dovetail guide wherein are inserted, by a fixed joint, some coating blocks in rubber or the like. In said guide are inserted as many blocks as are necessary to coat entirely the above-mentioned surface and form with them the gummy tightening surface of the pipe of the piping column. The advantage of said solution lies in the fact that, by varying the diameter of the pipe to be laid, it is sufficient to replace only the welded plates saddles having a low coat, with other suitable saddles, by arranging over these ones the same rubber blocks having a high cost of the preceding saddles.

Further details and features of the invention will be clear from the following description of the accompanying drawings which illustrate a preferred embodiment,

given only by way of example, because the technical and constructional modifications may be made without departing from the scope of the present invention.

In said drawings, FIG. ll illustrates a schematic front section of the tensioning device according to the invention, FIG. 2 illustrates a schematic longitudinal section,

FIG. 3 shows frontly the saddle coated of blocks utilized in the present invention, and FIG. 4 is a side view, in a higher scale, of the above-mentioned saddle with little blocks fixed to the track link.

With reference to the figures, numeral reference 1 indicates the base of the tensioning device which is rigidly fixed on the work pontoon and which supports, in correspondence of its four vertexes, four couples of columns, 2 turned and perfectly vertical, which are in turn connected on the upper part to a head 3.

All these elements form the rigid framework of support of the tensioning device. An upper caisson 4 and a lower caisson 5 present each two side sections 6 in suitable cylindrical hollows in which the abovementioned turned columns 2 are inserted in order that said caissons are positively guided by said columns in their vertical movements. Moreover

caissons

4 and 5 support at their ends some toothed cylinders for the operation of two long, opposed tracks, respectively 8 and 9, which, brought in touch respectively with the upper generatrix and the lower generatrix of the pipe to be launched provided with the sheath of cement 11, have the function to tighten between them the said pipe of the piping column to lay in the sea with such a friction force to stretch all the column with a constant and prefixed stretch.

Both upper track 8 and lower track 9 run in correspondence of the tightening zone of pipe 10 (i.e. in the lower part for track 8 and in the upper part for track 9), on sliding rollers 12 supported by sliding blocks 13 (three in the drawings) hinged between them to the ends and in turn bolted in correspondence of the hinges respectively to the

caissons

4 and 5 by means of adjustable threaded pivots 14. In such a way, by lengthening or by shortening suitably the above-mentioned adjustable pivots, it is possible to move angularly between them the above-mentioned sliding blocks in order that one can approximate with a broken line the curvature of the pipe to be tightened 10 of the piping column which must be laid in the sea at noticeable depths.

On the other hand, the length of two

tracks

8 and 9, by causing a tightening zone long enough to warrant always the tightening of several pipes of the piping column allows, as already mentioned, the laying in the sea of said column without being compelled to shut previously the interspaces free of cement sheathing in correspondence of the joints of the piping. In order to avoid the crack of the cement sheathing 11, pipe 10 is not tightened directly by two

opposed tracks

8 and 9, but indirectly by means of coating little blocks 15 fitted in suitable dovetail guides foreseen on some saddles made in welded plate 16 which are fixed to the links of said

tracks

8 and 9. More precisely (see particularly FIGS. 3 and 4), to each

link

17, 17, 17" and so on, is fixed by means of bolts or coupling pins 18, a saddle 16 which, if necessary, is equipped with two anchorage fins 19 strengthened by angle bars 20. Each saddle 16 consists of several welded plates, box-shaped and shaped in such a way to present frontly a concave surface 21 having the same diameter of the sheathed pipe 10 to be tightened. On said surface and extending for all its length is then welded a dovetail guide 22 wherein are fitted so many little blocks of neoprene or of similar material 15 as it requires to coat entirely the abovementioned concave surface 21.

These aligned coating little blocks 15 form in such a way a gummy curved surface 23 having high friction coefficient, which represents the contact surface with sheathed pipe 10. As the above-mentioned curved saddles 16 are suitable to tighten only a type of pipe, and i.e. only that pipe which has the same diameter of the concave surfaces 21, made in the same ones, it results that, in order to launch pipes having different diameters, it will be necessary to arrange so many series of curved saddles as are the possible different diameters of the piping to be launched. At this purpose it must point out that whereas the coating gummy little blocks have a high cost, the curved saddles of welded plate are easy to realize and have a very low cost.

Therefore, according to the present invention, the fact that it is necessary to replace, as the diameter of the pipe to be launched changes, only the series of low cost saddles, by making use always of the same coating little blocks, entails obviously a noticeable economy as to the prior art.

The vertical movement guided positively by columns 2, of the upper caisson 4 and of the relative upper track 8 to bring the little blocks of neoprene or similar mate rial 15 in touch with the upper generatrix of the sheathed pipe 10 to be tightened, is realized by means of a screw mechanism consisting of four side worm screws (see FIG. 2), arranged vertically between the couples of guide columns 2 and supported in such a way to be able to turn by head 3 of the rigid support framework of the tensioning device, which engage respectively in four nut screws (not evident in the figure), rigidly fixed in the side sections 6 of caisson 4. Said worm screws are turned about their axes by means of joint transmission 25 by an electric motor 26 arranged on said head 3.

Once the upper track 8 has been brought in touch with the upper generatrix of the pipe to be tightened 10, the relative upper caisson 4 is fixed in such a position by means of pins (not drawn in the figures) in such a way to unload the coupling screw-nut of any stress. At this purpose, both at the side sections 6 of caisson 4, and along the guide columns 2, holes wherein the above-mentioned clamping pins may be inserted are foreseen. Lower caisson 5 and the relative lower track 9 are, on the contrary, moved vertically to tighten the pipe to be launched with a fixed friction force by four side oleodynamic pistons 27 hinged at the base 1 between the couples of guide columns 2 and acting on side sections 6 of caisson 5. Said operation systems of

caissons

4 and 5, by assuring a vertical movement with the caissons always arranged perfectly horizontal and by warranting in such a way the uniformity of pressure exerted by

tracks

8 and 9 on pipe 10 in all the zone of tightening, besides to allow also by virtue of the same length of the tracks, as already said, the launching of the piping column without previously sheathing the junctions, allow also to apply to said piping column a stretch much more near to the yield point, given the noticeable safety with which said stretch may be now based, and this results in the possibility to. lay in the sea pipes at still more noticeable depths. Finally both the upper track 8 and lower track 9 are operated in such a way to run in the direction of arrows 28 to exert the required traction on the column of the piping to be launched, each by an electric motor 29 supported by

caisson

4 or 5 and connected by means of gears to one of the toothed cylinders 7.

The adoption of an electric motor instead of the conventional hydraulic motors for the operation of the track, besides a more easy upkeep and a higher fineness of regulation of the traction grade, allows too an easy self-regulation of the tensioning of the piping column by means of easy known means. In the present invention said self-regulation is reached by driving the two electric motors 29 by means of a servo control (not shown) interlocked to the stretch applied to the piping column. More precisely, said servo control deenergizes and stops motors 29 by stopping consequently

tracks

8 and 9 when the applied stretch is just the one prefixed to which must be subjected all the piping column to be launched; it energizes said motors 29 in such a way to run

tracks

8 and 9 in the direction of arrows 28 when the stretch developed by the movers of the work pontoon comes higher than the prefixed stretch, and therefore the piping column is launched; it energizes motors 29 in the opposite sense, i.e., in such a way to run

tracks

8 and 9 in the opposite direction of the arrows 28. When the stretch applied to the piping column tends to decrease as to the prefixed stretch, and consequently the column is retired on the pontoon.

The operation of the tensioning device of the present invention is as follows: The piping to be launched interposed between the two

tracks

8 and 9 is supported by sliding rolls 12 and by sliding blocks 13 of the lower caisson 5; then by operating motor 26 the upper caisson 4 lowers, guided along the guide columns 2 by the above-mentioned screw device, until its track 9 comes in contact with the upper generatrix of the piping; after having fixed upper caisson 4 in this position by pins, by means of oleodynamic pistons 27, lower caisson 5 is pushed towards the generatrix of the piping until its track 9 does not exert, in cooperation with upper track 8 the necessary tightening force of the piping; afterwards the main motors 29 are actuated by means of the above-mentioned servo control, so that

tracks

8 and 9 begin to exert the necessary traction on the piping.

We claim:

1. Tensioning device for laying a piping column in the sea, comprising tightening means for gripping between them the pipe to be laid, control and vertical guide means to bring the above-mentioned tightening means in contact respectively with the upper generatrix and the lower generatrix of the pipe to be laid and for gripping said pipe with a determined frictional force, and actuating means to run the above-mentioned tightening means horizontally so as to exert the necessary traction on the piping column, characterized in the fact that said tightening means consists of two long opposed upper and lower tracks and vertically movable upper and lower caissons supporting said tracks, which upper and lower tracks run along the tightening zone of the pipe on sliding rolls supported by sets of sliding blocks hinged between them at the ends and angularly regulable with respect to each other by being bolted at the hinges to the respective above-mentioned caissons through threaded pivots of regulation and including track links to which are fixed curved saddles bearing upper coatings of little friction blocks of rubbery material.

2. Tensioning device as in claim 1 characterized in that each of said sets consists of three sliding blocks.

3. Tensioning device as in claim 1 characterized in that the above-mentioned curved saddles fixed to the track links consist each of several box-like welded plates shaped so as to present a frontal concave surface of the same diameter as that of the pipe to be gripped and to which is welded a dovetail guide extending throughout the length of said concave surface.

4. Tensioning device as in claim 3 characterized in that the above-mentioned welded plate curved saddles are each equipped with two side anchorage tabs reinforced by angle bars which are fixed to the track links through coupling pivots.

5. Tensioning device as in claim 3 characterized in that said little friction blocks are fitted in said dovetail guides of the welded plate curved saddles in such a number as to coat entirely the said concave surfaces of the saddles.

6. Tensioning device as vin claim 1 characterizedin that said little friction blocks are of neoprene.

7. Tensioning device as in claim 1 characterized in that said vertical guide means consists, for both the upper and lower tracks, of a base, a head and four couples of turned vertical guide columns, fixed to the four vertexes of the base and the head, and extending through associated cylindrical cavities in the side sections of the track-supporting caissons so that they are positively connected thereto.

8. Tensioning device as in claim 1 characterized in that the above-mentioned control means to bring the upper track in contact with the upper generatrix of the pipe to be laid consists of couples: of guide columns, a head connecting said columns and four side worm screws, vertically engaged between the said couples of guide columns and the side sections of the upper caissons, which are rotated about their axes by means of an electric motor fixed on said connecting head.

9. Tensioning device as in claim 8 characterized in that the upper track is locked in contact with the upper generatrix of the pipe to be laid by means of locking pins which are inserted in mating holes in the side sections of the upper caisson and the corresponding guide columns.

10. Tensioning device as in claim 1 characterized in that said control means of the lower track to tighten the grip of said tightening means upon the pipe to be laid with a determined frictional force consists of a base,

couples of guide columns and four side oleodynamic pistons hinged to said base between the couples of guide column and connected to the side sections of said lower caisson.

11. Tensioning device as in claim 1 characterized in that said actuating means to run the two opposed tracks horizontally so as to exert the necessary traction on the piping column to be laid consists of an electric motor for each track, said electric motors being driven by a servo control interlocked to the stretch applied to the piping column to be laid.

Claims

1. Tensioning device for laying a piping column in the sea, comprising tightening means for gripping between them the pipe to be laid, control and vertical guide means to bring the abovementioned tightening means in contact respectively with the upper generatrix and the lower generatrix of the pipe to be laid and for gripping said pipe with a determined frictional force, and actuating means to run the above-mentioned tightening means horizontally so as to exert the necessary traction on the piping column, characterized in the fact that said tightening means consists of two long opposed upper and lower tracks and vertically movable upper and lower caissons supporting said tracks, which upper and lower tracks run along the tightening zone of the pipe on sliding rolls supported by sets of sliding blocks hinged between them at the ends and angularly regulable with respect to each other by being bolted at the hinges to the respective above-mentioned caissons through threaded pivots of regulation and including track links to which are fixed curved saddles bearing upper coatings of little friction blocks of rubbery material.

6. Tensioning device as in claim 1 characterized in that said little friction blocks are of neoprene.

8. Tensioning device as in claim 1 characterized in that the above-mentioned control means to bring the upper track in contact with the upper generatrix of the pipe to be laid consists of couples of guide columns, a head connecting said columns and four side worm screws, vertically engaged between the said couples of guide columns and the side sections of the upper caissons, which are rotated about their axes by means of an electric motor fixed on said connecting head.

10. Tensioning device as in claim 1 characterized in that said control means of the lower track to tighten the grip of said tightening means upon the pipe to be laid with a determined frictional force consists of a base, couples of guide columns and four side oleodynamic pistons hinged to said base between the couples of guide column and connected to the side sections of said lower caisson.