DE2549000A1 - PLATFORM FOR WORKING IN THE SEA - Google Patents

Description

Patent application

of the company

Strabag Bau-AG, 5 Cologne-Deutz, Siegburger Strasse 241

Platform for working in the sea

The invention relates to a platform for work in the sea with a buoyant foundation body in which supports extending beyond the sea surface are anchored and which is connected to a deck comprising the supports and designed as a floating body by tension members and can be lowered to the sea floor with lowering devices arranged on the deck with which the deck can also be pulled up on the supports ο

A platform of this type is known in which the supports are made of telescopically telescopic steel frameworks.

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There are towers whose lower parts are anchored to the body of the gudgeon and the upper parts of which are guided and can be fastened to a frame-shaped floating deck that surrounds them. When lowering, the initially floating foundation body is flooded and lowered with winches while hanging from tension members. standing on the floating deck frame.

This known platform is in larger dimensions and for the foundation in great water depths of about 30 m and no longer usable. For great water depths, heavyweight platforms have recently been built, their foundations and supports made of seawater-resistant material, such as reinforced concrete or prestressed concrete, and are sufficiently stable to absorb and absorb the considerable dynamic forces from the sea and wave impact large deck with high payload at a distance above the water surface to wear. The aim here is as small a swimming depth as possible for the platform so that it is shallow Waters produced and can be transported to the installation site by swimming through shallow waters. at During this transport, the platform should be able to carry as high a payload as possible in order to carry all the necessary on deck Machines, apparatus and equipment for the work to be carried out at sea, such as oil drilling, to be able to carry them, their subsequent transport and assembly due to the weather dependency would be extremely time-consuming "

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By placing the floatable deck on the floating foundation body, it is possible to carry high payloads with a heavyweight platform during the transport of the platform to be carried to the place of use, so that all essential machines and equipment, such as drilling rigs, cranes, pipes and Pump systems that can already be installed at the place of manufacture near the shore. When swimming to the scene of action is then the center of gravity of the platform with their heavily laden deck and towering support legs usually above the center of buoyancy that However, dimensional stability of the foundation body, which protrudes above the water surface together with the deck, is sufficient in order to be able to transport the platform safely to the place of use. However, the platform gets there when it is lowered of the foundation body to the sea floor in a critical phase.

When it sinks to the seabed, the foundation body is completely submerged and loses its dimensional stability. As the center of gravity of the overall system lies above the center of gravity of buoyancy, the Risk of the platform capsizing if lateral disruptive forces such as wind and swell act on the platform when it is being lowered the foundation body act. The deck floating on the surface of the water can act as the foundation body do not stabilize sufficiently, as the tension members connecting the foundation body with the deck, as a result of the

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due to the swell caused by the swell of the deck temporarily slack and the backward turning moment of the deck cannot transfer to the foundation body. In addition, produce the periodic ones caused by the swell Fluctuations of the deck in the ropes considerable inertia forces, which place them under very high stress and are easy to do Break.

The object of the invention is to avoid these difficulties and to design the platform in such a way that it floats safely together with the fully equipped deck during transport to the site of use and can be lowered onto the sea bed without the risk of capsizing at the place of use _{or the like}

This object is achieved with the invention in that the tension members from the foundation body to the upper end of the Columns run through and are prestressed.

This training has the advantage that the deck is firmly connected to the foundation body in every position, even in wind and swell remains, because it hangs on the tension members running through to the upper end of the supports and out of the water lifts if it gets into a wave trough and this reduces the distance to the foundation body, which is done without pre-tensioning the slackening of the lower tension member sections between the deck and the foundation body would result. The righting one Moment of the floating deck then acts via the supports on the foundation body, so that its tendency to capsize

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is also counteracted when there is no longer a train connection between the deck and the lower part of the tension members Foundation body consists.

The stabilizing effect of the deck is fully effective even when external forces such as wind and swell When lowering the foundation body, move the platform from its vertical position to an inclined position. That to the The floating deck is attached to continuous tension members and is always held parallel to the foundation body under the effect of the disturbing forces deeper into the water on one side, so that the buoyancy is opposite to the capsizing moment Righting moment is generated as a force couple on the one hand via the lower tension member sections directly and on the other hand acts on the foundation body via the upper tension member sections and the supports.

By the tensile bias prevents individual Zuggliederabschnitte alternately limp excited and again and are thus exposed to high shock loads that can lead to large deformations and fatigue fractures in the tension members ₀ In addition, thereby avoiding shock loads of lifting and fastening points which are particularly dangerous because they can lead to a sudden failure of the entire suspension.

It is particularly useful if the tension members so far

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are biased that none of their above and below deck upper sections and lower sections becomes stress-free when the highest waves to be expected act on the floating deck. Load changes from the forces caused by the swell then only ever lead to an increase or decrease the tensile force already present in the tension members, in the lower and upper section of each tension member at the same time there is a change in the tensile stress, which, however, never reaches the value zero.

Since the tension members pass through according to the invention from the foundation body to the upper end of the supports, they can, as well like the lowering devices, both for lowering the foundation body on the seabed and for pulling it up of the deck in its working position above the water level can be used immediately.

According to a further feature of the invention the tension members ropes may be, which is arranged through the deck and / or foundation body and / or at the upper end of the support roller blocks are clipped and run over arranged on the deck winches ₀ The for sinking and catching up of the foundation body and for pulling and lowering the deck on the supports required high tensile forces can be distributed over several strands of rope and managed with normal friction winches

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End at the upper end of one of the supports and penetrate the deck. To lower the foundation body and to raise the deck, the same winches can work on the same rope without having to reposition the rope or reverse the direction of rotation of the winches _{or the like}

According to a further feature of the invention, the lowering devices can also be hydraulic climbing presses, which clamp on the tension members. Climbing presses are hydraulic lifting devices with two rope clamps, one with the cylinder and one with the other is connected to the piston of the lifting device and which alternately clamp on the rope and that on them Lift up the attached deck, one clamp supporting the deck carried by the climbing press on the rope, while the other rope clamp is tightened by retracting the piston and, in turn, is clamped to the rope when the piston extends and raises the deck attached to it.

Together with these climbing presses, prestressed steel bars can also be used as tension members.

The invention is illustrated by the drawings of an exemplary embodiment explained in more detail. It shows:

Fig. 1 shows a platform according to the invention with the deck placed on the foundation body in the towing state in a side view and partially in section,

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Fig. 2 shows the object of Fig. 1 when lowering the foundation body,

FIG. 3 shows the platform according to the invention with the foundation body set down on the seabed in FIG a side view and partly in section,

4 shows the platform according to FIG. 3 in the working position with the deck raised,

FIG. 5 shows a schematic diagram corresponding to FIG. 2, which shows the stress when waves pass through,

6 shows a schematic diagram corresponding to FIG. 5, which shows the loads on the platform lateral disruptive forces explained,

FIG. 7 shows a corresponding to the intermediate stage according to FIG Schematic diagram showing the arrangement of the tension members and the formation of a lowering device and

Fig. 8 is one of those used to raise and lower the deck Climbing presses in a schematic side view on an enlarged scale.

In the drawings, 10 is a platform for work in the sea, which is designated as a heavyweight platform

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forms is and, for example, as an oil rig for drilling Petroleum can be used in deep seabeds. The platform 10 consists of a buoyant foundation body 11 made of reinforced concrete or prestressed concrete, the one in many Cells subdivided cavity 12, the ballast 13 in the form of sand, silt or the like in part. record and can be flooded and drained again. It can also be used for oil storage. In the foundation body 11 are four appropriately tubular supports 14 made of prestressed concrete or steel anchored, on which a buoyant deck 15 in is guided displaceably in the vertical direction. The deck 15 is preferably made of a steel, box-shaped Platform, which the derrick 16 and other, not shown here devices for performing the intended Working in the sea bears. The supports 14 penetrate the deck 15 in suitable recesses 17 »in which the supports 14 when the foundation body 11 is lowered onto the Sea floor 18 are guided laterally and in which the horizontal forces from the deck 15 on the supports 14 and vice versa be transmitted.

The deck 15 is connected to the foundation body 11 by tension members 19 connected, which are passed in suitable channels 20 through the deck 15 and over the entire length of the supports 14 run through. The tension members 19 are with their one end 21 on the foundation body 11 and with their other end 22 on upper end 23 of the supports 14 attached to a head frame 24, that during the transport, during the lowering of the foundation body and while the deck is being pulled up

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is attached to the supports on these _o

Each of the tension members 19 is at least one lowering device 26, which is arranged on the surface 25 of the deck 15. The lowering device 26 moves that Deck 15 on the tension members 19 in the longitudinal direction of the supports 14th

In the transport state shown in FIG. 1, the deck 15 rests on the foundation body 11 and is with it Tensioned over the tension members 19, on which the foundation body 11 with the help of the lowering devices 26 against the Deck 15 is pulled. The cavity 12 of the foundation body 11 is completely drained and floats on the water surface 28, where it is towed to the place of use with tugs 29 (Fig. 1) "

Arrived at the place of use, the foundation body 11 is released from the deck 15 and flooded so far that its weight collapses with the weight of the support legs attached to it, the buoyancy of these components reaches or slightly exceeds The foundation body 11 then hangs with the lower sections 19b of the tension members 19 on the lowering devices 26, which lower the foundation body 11 continuously and evenly until it reaches the sea floor 18 (Fig. 2) "

During the lowering, the deck 15 floats on the water surface 28 and the tension members 19, which each extend over the entire length of the support legs 14, run through the

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Lowering devices 26 therethrough. The .Tug ships 29 hold meanwhile the platform is in place so that currents, wind and swell will not drive it away.

Since wind and swell normally prevail even in good weather on the high seas, waves passing through must be expected, which raise and lower the deck, while the foundation body 11 is withdrawn from swell after reaching a certain depth. The waves passing through tend to raise and lower the floating deck 15, whereby additional traction forces are alternately introduced into the lower sections 19b and the upper sections 19a of the tension members 19, while at the same time the opposing tension member sections are de-energized. If, for example, the deck 15 is lifted by a shaft 30, the upper sections 19a of the tension members 19 are tension-free, while the lower sections 19b receive additional tension (FIG. 5) 19b without tension and the upper sections 19a come under tension, since the buoyancy on deck 15 decreases or disappears completely and the deck 15 then hangs with the tension members 19 on the end structures 24 of the supports 14 and tries to push the foundation body 11 deeper _o

Since this changing load is extremely demanding on the tension members 19, the tension members 19 are after

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Invention biased so far that none of its above and below the deck 15 upper sections 19a and lower sections 19b when the highest waves 30 and 31 to be expected act on the floating deck 15 becomes dead. What is achieved hereby is that the tension members 19 do not cause any impact loads, but only one be subjected to swelling stress, doh. the tensile stresses effective in them are corresponding to the sea gradually larger or smaller, but cannot jump from zero to a larger value or drop from this to zero "

6 shows a state when the platform is being lowered, in which lateral disturbance forces such as wind and swell act on the platform and try to bring it out of its vertical position into an inclined position _o Since the weight s center of gravity G is above the lift center of gravity A. is located, the tendency to tilt is increased. With increasing inclination, the deck 15 dips deeper into the water on one side than on the opposite side, so that the buoyancy forces 32 are greater there than here Tension members 19 of the more deeply immersed supports 14 and over the upper sections 19a of the tension members 19 of the less deeply immersed supports 14 and over these itself is transferred to the foundation body 11, so that the system is again

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can straighten up. The deck 15 thus enables real stabilization the platform when it is being lowered, causing the platform to capsize under the influence of lateral disruptive forces prevented. Here, too, the pre-tensioned tension members 19 are only subjected to a swelling change in tension, resulting from the gradual inclination as the platform is heeled and raised again.

For lowering the foundation body 11 and for later lifting the deck 15 out of the water, friction winches 33 are used, which are arranged on the deck 15 and are only shown schematically in FIG. As tension members 19 are used in this case high-strength steel cables, which are sheared by several roller blocks 34 and 35, of which the one roller blocks 34 on the head frame 24 of the supports 14 or at the top 36 of the foundation body 11 and of which the other 35 at the top 25 and at the bottom 37 of the deck 15 are attached.

Instead of steel cables, prestressed steel rods can also be used for the tension members 19. In this case it is expedient to use hydraulic Klette rpre ssen 38 as the lowering device, one of which is shown schematically in FIG. 8 shown and which can also be used in conjunction with steel cables. The climbing press 38 consists from expediently one or more hydraulic cylinders 39, which carry a lower cable clamp set 40, with which the climbing press can clamp onto the tension member 19. On the piston 41 of the climbing press 38 there is an upper set of rope clamps

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arranged, which can also clamp on the tension member 19. The hydraulic climbing press 38 works in one Housing 43, which is firmly connected to the deck 15 and through which the tension member 19, for example a steel cable or a steel rod, goes through and on which the climbing press 38 can be supported when lifting.

During the lifting phase shown in FIG. 8, the climbing press 38 is clamped with its lower set of rope clamps 40 Tension member 19 fixed. When the piston 41 is extended, the upper cable clamps, which slide loosely along the tension member 19, press 42 the housing 43 and with it the deck 15 in the air. As soon as the pistons 41 are fully extended, it jams Cable clamp pair 42 on the tension member 19 and holds the housing 43 and deck 15 in the raised position, while the lower Loosen the cable clamps 40 and move the pistons 41 into the cylinder 39, the cable clamps 40 on the tension member 19 being a piece slide upwards. The cable clamps 40 can then again be placed firmly around the tension member 19, while the upper cable clamps 42 open and repeat the process just described begins.

When the deck is lowered and the foundation body is raised proceeded analogously in reverse order

After the foundation body 11 has been lowered, it is completely flooded and the deck 15 is flooded with the aid of the lowering devices 26 lifted out of the water and pulled up on the nozzle 14 until it reached the position shown in FIG

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In this state, the head girders 24 on the supports 14 together with the tension members 19 can be removed if other devices are provided for fastening and connecting the deck 15 to the supports 14. When the deck is raised, the platform according to the invention does not have only a stable position, but wind and waves can no longer harm it, _etc.

The invention is not restricted to the exemplary embodiment. For example, it is also possible to pretension the tension members 19 to a lower value than corresponds to the highest wave to be expected if one believes that one can accept occasional impact loads on the tension members. It is also possible to use bundles of rods instead of ropes and rods for the tension members and to protect them from corrosion by taking special measures _o Instead of the lifting and lowering devices, which are only explained as examples, lowering devices of other types can also be used, without the scope of the invention is exceeded o

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Claims (6)

Expectations .JPlatform for working in the sea with a buoyant Foundation body in which supports extending beyond the surface of the army are anchored and the with a deck designed as a floating body, which includes the supports, is connected by tension members and is connected to the deck arranged lowering devices can be lowered onto the army floor, with which the deck can also be pulled up on the supports is, characterized in that the tension members (19) from the foundation body (11) to the upper end (23) of the Supports (14) run through and are prestressed o 2. Platform according to claim 1, characterized in that the tension members (19) are biased so far that none their upper sections (19a) and lower sections located above and below the deck (15) (19b) is de-energized when the highest waves to be expected act on the floating deck (15). 3. Platform according to claim 1 or 2, characterized in that the tension members (19) are ropes which are passed through on Deck (15) and / or foundation body (11) and / or roller blocks arranged at the upper end (23) of the supports (14) (34, 35) are sheared and run over cable winches (33) arranged on the deck (15). 4. Platform according to one of claims 1 to 3, characterized in that 709819 / 0Ö7S indicates that the tension members (19) with their one end (21) on the foundation body (11) and with their other End (22) are attached to the upper end (23) of one of the supports (14) and penetrate the deck " 5. Platform according to one of claims 1 to 4, characterized in that that the tension members (19) are prestressed steel rods 6. Platform according to one of claims 1 to 5, characterized in that that the lowering devices (26) are hydraulic climbing presses (38) which are attached to the tension members Clamp (19). 7ο platform according to one of claims 1 to 6, characterized in that that the deck (15) and the foundation body (11) over the tension members (19) with the help of the lowering devices (26) are braced against each other during transport ο 709819 / 007S