GB2126312A - Abandoning head of automatic release type - Google Patents

Abstract

There is disclosed an abandoning head of cylindrical structure for lowering a pipeline to the sea bed, in which the means for fixing it to a pipe portion (2) butt-welded to the free end of said pipeline consist of a series of spherical toothed sectors (5) engaging with a rack (7) formed in the end of said cylindrical structure (1), said sectors (5) being provided with locking teeth (12) cooperating with an annular projection (13) on said tube portion (2), and being disposed radially about a central sphere (8) rigid with the piston (10) of a horizontal hydraulic cylinder (11), the rear chamber (14) of which is directly connected to a medium pressure accumulator (16), said cylinder (11) being controlled by a special hydraulic circuit Fig. 5, (not shown) by means of a sound pulse or manually. <IMAGE>

Description

SPECIFICATION Abandoning head of automatic release type This invention relates to a new abandoning head for laying a pipeline, which is self-contained and arranged for rapid and simple automatic release either by remote or manual control,while being reliable, simple, economical and in particular easy to fix to the pipeline. An abandoning head is a generally cylindrical robust structure used for lowering a pipeline being laid on to the sea bed, and abandoning it there wheneverthe pipe laying ship has to suspend operations and withdrawfrom the working zone. Said head mustthen be recovered afterthe pipeline has been laid.

For this purpose, the structure is provided at one end with a connection bore for a ring to which the cable of a winch on the pipe laying ship is hooked, while its other end is locked to the pipeline to be lowered on to the sea bed.

In the current state ofthe art, the abandoning head is generally locked to the pipeline to be abandoned by means of pinning. More specifically, a pipe portion provided with diametrically opposing bores is welded to the free end of the pipeline, and the abandoning head also provided with diametrically opposing bores is inserted into the pipe portion, the two then being coupled together by a pin which passes through said diametrically opposing bores of the pipe portion and head.

It isapparentthat such a method gives riseto obvious drawbacks due to complications in the pinning operations, and in particular in the recovery of the head, which requires divers to manually remove the pin.

The object ofthe present invention is to obviate the aforesaid drawbacks and thus provide an abandoning head which in addition to being simple and economical, allows rapid coupling and automatic or manual release.

This is substantially attained in that atthat end ofthe head distant from that provided with the connection bore there is provided a coupling and release device of simple and economical construction and reliable operation, which allows easy and rapid fixing and automatic detachment ofthe head to and from a pipe portion which is welded to the pipeline to be abandoned.

More specifically, the abandoning head for lowering the free end of a pipeline from a pipe laying ship on to the sea-bed, said head being constituted by a robust cylindrical steel structure provided atone end with a connection bore for a ring for hooking to the cable of a winch on said pipe laying ship and at its other end with means for its fixing to a pipe portion butt-welded to said free end of the pipeline, is characterised according to the present invention in that said fixing means consist of a series of spherical toothed sectors which are disposed radially and engage with a rack provided in said other end ofthe structure, and are held in position by a central sphere rigid with the piston of a horizontal hydraulic control cylinder inside the structure, each of said sectors projecting from said other end ofthe structure byway of a locking tooth which is caused to cooperate with the inner surface of an annular projection present at the free end of said pipe portion by the action of said hydraulic control cylinder, of which the rear chamber is directly connected to an internal medium pressure hydraulic energy accumu lator,there being present inside said structure a hydraulic circuit for manually controlling said hyd- raulic cylinder and for setting the head for its automatic rapid release by remote control using a sound pulse.

In this manner, the head is fixed to and detached from the pipe portion by simply moving the piston of the hydraulic cylinder and consequently said central sphere which by pressing against the toothed sectors compels them to rotate on the rack and to thus cause their locking teeth to open outwards against said internal surface ofthe annular projection on the pipe portion, thus locking the head to this latterwhenthe sphere is moved outwards, and in contrast releasing the locking teeth when the sphere is moved towards the inside ofthe structure.

On the other hand, astherearchamberofthe hydraulic control cylinder is in direct communication with the medium pressure accumulator with the result thatthe piston and consequently said central sphere are continuously urged outwards, the locking teeth of the head are normally in their operating position, and thus in order to release the head it is necessaryonlyto feed the front chamber of the hydraulic cylinder with a pressure greater than the average pressure existing in said rear chamber. According to a preferred embodi ment of the present invention, said fixing means consist of a series of twelve spherical toothed sectors disposed radially and separated from each other by spacers.Afurtherfundamental characteristic of the present invention is that said hydraulic control circuit is constituted by an automatic th ree-way two-position solenoid valve which when in its normal position connects, by way of a unidirectional valve, a four-way four-position manual valve to an internal accumulator forthe discharged oil, this lattervalvewhen in its normal position being connected by way of a second unidirectional valve to the front chamber of said hydraulic cylinder, said solenoid valve being caused by a motor, operated bythe sensors of a sonar system which are energised by a sound controlling pulse, to switch-overtemporarily into its second position in which, by way of said manual valve and said second unidirectional valve, it connects a third internal high pressure hydraulic energy accumulatorto said front chamber of said hydrauliccylinder, said chamber being also connected to another passageway of said manual valve by bypassing said second unidirectional valve. Finally, according to a preferred embodiment of the present invention, a second manual four-way four-position valve is connected to said manual four-way four-position valve in parallel to this latter and in a position diametrically opposite thereto with respect to said cylindrical structure.

This thus provides double control which ensures easy manual operation, in that one of the two manual valves is always easily accessible whichever way the head lies on the sea bed.

The invention is described in detail hereinafter with reference to the accompanying drawings which illus trate a preferred embodiment thereof by way of non-limiting example, in that technical and constructional modifications can be made thereto without leaving the scope of the present invention.

In said drawings: Figure 1 is a perspective view of the abandoning head constructed in accordance with the invention; Figure 2 is a longitudinal section through the head of Figure 1 when coupled to the pipe portion; Figure 3 is a front section through the head on the line AA of Figure 2, to an enlarged scale; Figure 4 is a partial longitudinal section to an enlarged scale through the head of Figure 1 when released from the pipe portion; Figure 5 is a diagram ofthe manual and automatic hydraulic control circuitforthe head according to the invention.

In Figure 1 ,the reference numeral 1 indicates a robust cylindrical steel structure constituting an abandoning head to be locked to the free end of a pipe portion 2 which is butt-welded to a pipeline, not shown in the figure. Said structure 1 is provided at its end 1' with a bore 3 for connecting a ring for hooking to the cable of a winch of a pipe laying ship, also not shown in the figure, and is provided at its other end 1" with means 4for its fixing to said pipe portion 2.

Said means 4 consist of a series of twelve spherical toothed sectors 5 disposed radially and separated from each other by spacers 6, and engaging with a rack 7 formed in said end 1 of the strucutre 1 they being kept in position by a central sphere 8 rigid with the rod 9 of the piston 10 of a horizontal hydraulic control cylinder 11 fixed to the inside of the structure 1.

All said spherical toothed sectors 5 project from the end 1" of the structure 1 by way of a locking tooth 12 which is arranged to cooperate with the inner surface of an annular projection 13 present on the free end of said pipe portion 2.

The rear chamber 14 of said hydraulic control cylinder 11 is directly connected, byway of the conduit 15, with a medium pressure hydraulic energy accumulator 16 which is installed in the structure 1 and communicates with the outside byway of the conduit 15' and the instant connector 17 which is embedded into one side of the abandoning head (see specifically Figure 1).

In this mannerthe piston 10 is normally atthe right hand end of its stroke, the sphere 8 is also displaced to the right, and thus the spherical toothed sectors 5 are rotated by the action ofthe rack 7 in the sense of opening out their locking teeth 12 against the inner surface ofthe annular projection 13. In otherwords, the normal position of the head is that in which it is oupled to the pipe portion 2 as shown in Figure 2.

Afurthertwo accumulators, namely a high pressure hydraulic energy accumulator 18 and a discharge accumulator 19, are also installed in the structure 1.

The high pressure hydraulic energy accumulator 18 is connected via the conduit 20 to the instant external connector 21 embedded into one side of the abandoning head, and via the conduit 20' (see Figure 5) to a circuit 22 contained in the housing 23 situated inside the structure 1. More specifically, the conduit 20' connects the accumulator 18 to the passageway I of an automaticthree-waytwo-position solenoid valve 24 which in its normal position connects its passageway II to the passageway Ill as shown in Figure 5, ie it connects the passageway IV of a manual four-way four-position valve 25, by way of a unidirectional valve 26, to said discharge accumulator 19 which is also connected by the conduit 27 to the instant external connector 28.Said solenoid valve 24 is controlled by an electric motor 29 which is mounted on the spindle 30 of the solenoid valve and is operated by the sensors 31, and 31", disposed 1200 apart, of a sonar system which can be energised by a controlling sound pulse.

Following said controlling sound pulse, said motor operates for a predetermined time (eg. 50 seconds) during which it makes the spindle 30 of the solenoid valve 24 rotate through one complete revolution, said valve, starting from its normal position Il-Ill illustrated in Figure 5, thus returning there after passing temporarilythrough its second position II-l,atwhich it connects the high pressure accumulator 18 to said passageway IV of the manual valve 25.

The normal position of this latter valve 25, which is accessible from the outside, is that illustrated in Figure 5, ie its said passageway IV is connected to the passageway V which is connected by the conduit 32 to the front chamber 34 of the hydraulic control cylinder 11 byway of a second unidirectional valve 33.

Of the othertwo passageways of the valve 25, the passageway Vl is connected via the conduit 35 and conduit 20to said high pressure hydraulic energy accumulator 18, and the passageway VII is connected, via the conduit 36 which bypasses said second unidirectional valve 33, and byway of said conduit 32 to said front chamber34 ofthe hydraulic control cylinder 1 1.

Finally, Figure 5 shows by dashed lines the conneo tion, in parallel to said manual four-way four-position valve 25, of a second manual four-way four-position valve 25' which is positioned diametrically opposite the first with respect to the structure 1 (see specifically Figure 2), so that one of said two valves is always easily accessible from the outside whicheverway the head lies on the sea bed.

The method of operating the head and its setting for rapid automatic release are as follows.

As the pressure of the accumulator 16, which acts in the rear chamber 14 ofthe horizontal hydraulic control cylinder 11, keeps the rod 9 pushed outwards in the mechanical coupling position for coupling the head to the pipeline to be abandoned, or ratherto the pipe portion 2 butt-welded to the pipeline to be abandoned, it is firstly necessary to open said mechanism. Forthis purpose, one ofthe two manual valves 25 or 25' is moved from position IV-V to position VI-VIl, so that the high pressure in the accumulator 18 passes into the front chamber 34 of the cylinder 11 to retract the piston 10 and thus open the locking teeth 12 as shown in Figure 4.

It is now possible to move the end 1" of the head 1 up to the end of the pipe portion 2 that they mate, after which said previously operated manual valve 25 or 25' is moved into position lV-Vll,which empties the front chamber 34 as it is directly connected to the discharge accumulator 19, and with consequent expansion in the chamber 14. The piston 10 again moves to the right, thus causing the locking teeth 12 to openoutagainsttheinnersurfaceoftheannular projection 13 on the pipe portion 2, to lock the head and pipe portion together.

On returning said manual valve 25 or 25' to position IV-V (see Figure 5), the head is set for automatic release by the sonar system.

In this respect, after lowering the pipeline by means of a cable hooked into the bore 3 of the head, a sound pulse is used to energise the sensors 31,31' and 31" of a sonar system, these closing the electric circuit of the motor 29 which remains in operation for a predetermined time (eg. 50 seconds), and during this time period causes the spindle ofthe automatic valve 24to make one complete revolution. Said valve 24thus passes from its normal position Il-Ill to position ll-l" to connectthe front chamber 34 ofthe hydraulic cylinder 11 to the high pressure accumulator 18.In this manner, as the pressure in the front chamber 34 is higher it overcomes that of the rear chamber 14 provided by the accumulator 16, thus causing the piston 10 to retract and open the mechanism (situation shown in Figure 4). When the valve again passes automaticallyfrom said position ll-l to its initial position Il-Ill, the front chamber 34 of the cylinder 11 again becomes connected to the discharge line of the accumulator 19, but the pressure cannot fall because ofthe presence ofthe unidirectional valve 33, and thus the mechanism remains open. In order to be able to effect the closure operation, one ofthetwo manual valves 25 or 25' must be moved from position IV-Vto position IV-VII, thus short-circuiting the unidirectional valve 33. Finally, if the automatic device does not operate, the mechanism can be released manually by operating one of the two manual valves 25 or 25', and more specifically by moving one of said valves from the manual position IV-V to the position VII-VI orVI-V, this short-circuiting the automatic solenoid valve 24 and directly feeding the front chamber 34 of the hydraulic cylinder 11 with high pressure.

Claims (5)

1. An abandoning head for lowering the free end of a pipeline from a pipe laying ship onto a sea bed, said head comprising a cylindrical structure provided at one end with a connecting means for connecting it to the cable of a winch on said pipe laying ship and at its other end with means forfixing itto a pipe portion butt-welded to said free end ofthe pipeline, said fixing means comprising a series of spherical toothed sectors which are disposed radially and engage a rack provided in said other end ofthe structure, and which are held in position by a central sphere rigid with the piston of a hydraulic control cylinder inside the structure, each of said sectors projecting from said other end of the structure by way of a locking tooth which is adapted to cooperate with the inner surface of an annular projection on the free end of said pipe portion by the action of said hydraulic control cylinder, the rear chamber which is directly connected to an internal hydraulic energy accumulator, there being present inside said structure a hydraulic circuit for manually controlling said hydraulic cylinder and for setting the head for its automatic rapid release by remote control using a sound pulse.

2. An abandoning head as claimed in claim 1, wherein said fixing means comprises a series of twelve spherical toothed sectors disposed radially and separated from each other by spacers.

3. An abandoning head as claimed in claim 1 or 2, wherein said hydraulic control circuit comprises an automaticthree-waytwo-position solenoid valve which when in its normal position connects, by way of a unidirectional valve, a four-way four-position manual valve to an internal accumulatorforthe discharged oil, this lattervalvewhen in its normal position being connected by way of a second unidirectional valve to the front chamber of said hydraulic cylinder, said solenoid valve being caused by a motor, operated by the sensors of a sonar system which are energised by a controlling sound pulse, to switchovertemporarily into its second position in which, by way of said manual valve and said unidirectional valve, it connects a third internal hydraulic energy accumulator to said front chamber of said hydraulic cylinder, said chamber being also connected to another passageway of said manual valve by bypassing said second unidirectional valve.

4. An abandoning head as claimed in any of the preceding claims, wherein a second manual four-way four-position valve is connected to said manual four-way four-position valve in parallel to the latter and in a position diametrically opposite thereto with respectto said cylindrical structure.

5. An abandoning head of automatic release type, substantially as described and illustrated herein.