DEVICE FOR HANDLING OF A HOSE
The present invention relates to the handling of a hose primarily when transferring a fluid such as crude oil to a vessel. The invention relates first and foremost to an apparatus for handling a hose for the transfer of crude oil from an offshore production unit to a shuttle tanker.
In the offshore production of crude oil from a large field, pipelines are preferably laid from the oil field to land to convey the oil to a processing plant, such as an oil refinery. Such pipe installations are relatively expensive, and can only be built if the oil field is very large or if they can be used by several smaller fields close to one another.
To make smaller fields profitable, it is necessary to have cheaper solutions, and mobile production units have long been used for this purpose. Mobile production units are normally ships containing the necessary equipment to produce oil from a field, tanks for temporary storage of a certain amount of oil, and equipment for transferring crude oil from the mobile production unit to a shuttle tanker which runs between the oil field and a terminal on land.
Today, there are in essence two solutions in use for handling the hose for the transfer of oil from the mobile production unit to the shuttle tanker.
A commonly used solution is a transfer hose which lies on the deck of the mobile production unit. When oil is to be transferred, one end of the hose is hauled across to the shuttle tanker, the hose is connected to the tanks of the shuttle tanker and the tanks of the production unit, and then the oil transfer can commence. When the oil has been transferred from the mobile production unit to the shuttle tanker, the hose must be released from the shuttle tanker, closed to prevent oil from leaking out, and hauled back to the deck of the mobile production unit with the aid of winches or the like, and is again laid on the deck where it may be placed in a cradle to provide stability. This positioning of the hose is not satisfactory, whilst during maintenance that requires the hose to be drained, the hose must be hoisted up with the aid of a crane, to allow the oil to drain out of the hose.
A second solution, which, for example, is known from NO B 137 884, is an embodiment where the hose is coiled up on a drum. A drum of this kind must be large so as not to cause kinking of the hose. It has the advantage over the aforementioned
solution that the separate winch for retrieving the hose is not necessary, but is has the disadvantage that the hose must be rotated backwards and forwards on the drum in order to drain the hose when necessary. Moreover, a solution of this kind will require a rotating seal which may be worn and thus allow leakage.
DE 2 056 756 also makes known an apparatus where the hose is guided over a wheel displaceable in the longitudinal direction of the ship and having a vertical axis of rotation. However, this apparatus is associated with many problems which have resulted in its never becoming a success. For instance, the apparatus requires a great deal of space and cannot be placed on board an existing ship without considerable rebuilding. Moreover, it is large and heavy so that placing it on board a ship will have a negative effect on the tank or loading capacity of the ship. Furthermore, considerable problems will arise in that the force of gravity will seek to draw the hose out of engagement with the wheel and down onto the underlying deck and any hose support means.
The object of the present invention is to provide an apparatus for handling a hose preferably for the offshore transfer of a fluid, such as crude oil, from a production unit to a shuttle tanker wherein the aforementioned problems are obviated.
According to the invention there is provided an apparatus for handling a hose for the transfer of a fluid, such as crude oil, to a vessel, such as a shuttle tanker, from a second vessel or offshore production unit, wherein a hose, which is normally located on one of the vessels and connected to the tank thereof, is pulled from one vessel to the other and connected to the tank of the second vessel, and wherein the hose after transfer is disconnected from the tank of one of the vessels and hauled aboard the other vessel, wherein the hose on board the vessel on which it is normally located runs over a deflection body capable of being moved between two extreme positions, wherein in one of the extreme positions of the deflection body the hose is pulled out, whilst in the other extreme position of the deflection body the hose in its entirety is on board the vessel.
The invention will now be described with reference to two preferred embodiments and the appended figures, wherein:
Figure 1 is a side view of an apparatus according to the invention;
Figure 2 shows the same apparatus as in Fig. 1, viewed from the stern;
Figure 3 is a bird's eye view of the same apparatus as in Fig. 1 ;
Figures 4a and 4b are side views of the same apparatus as in Fig. 1 not connected to and connected to a shuttle tanker, respectively;
Figures 5a and 5b are side views of an alternative embodiment not connected to and connected to a shuttle tanker, respectively; whilst
Figure 6 is a side view of an alternative embodiment.
Embodiment 1.
The apparatus as shown in Figures 1 to 4 is provided on the deck 5 of a production ship 9. A hose 1 , of the type normally used for transfer operations of this kind, is secured and connected to the tank of the production unit at connection 8. From connection 8, which is close to the stern part of the mobile production unit, the hose 1 runs in a groove 6 essentially in the longitudinal direction of the ship. The hose then runs over a wheel 2, and then continues towards the stern of the ship, where it runs over a boom 7 equipped with a deflection body 13. Shaft 3 in the centre of the wheel 2, rests against two rails 4, one rail on each side of the groove 6. The rails 4 are each supported by a respective frame 10.
Figure 1 shows the hose when it has been pulled out halfway. When the hose 1 is pulled in on the mobile production unit 9, wheel 2 is pulled forward into its forward position, and connector 12 on the end of the hose 1 rests against boom 7.
When oil is to be transferred from the production unit to the shuttle tanker, first the shuttle tanker 11 is positioned relative to the production unit 9. To secure their mutual positioning, the shuttle tanker 11 is secured to the production unit 9 by means of hawsers. A hawser from the shuttle tanker 1 1 is then fastened to the end of the hose 1, and the hose 1 is pulled by means of this hawser on board the shuttle tanker. As the hose 1 is pulled on board the shuttle tanker, the wheel 2 is moved on the rails 4 towards the stern of the production unit.
When the hose has been hauled on board the shuttle tanker 11, connector 12 is connected to the tank of the shuttle tanker, and the transfer of crude oil commences.
When the transfer of oil has been completed, the connector 12 is disconnected from the tank of the shuttle tanker, a valve in the end of the hose 1 closes, and the hose is released onto the sea from the shuttle ship 11. The hose 1 is then hauled on board the production unit 9 in that wheel 2 is pulled forward until the hose is once more in the position where connector 12 rests against the boom 7 and the hose is taut. The hose is then stored in a stable manner on board the production unit 9 in that one part rests in groove 6 whilst the other part is held in place by the frame 10.
To pull in the hose 1 , the wheel 2 must have propulsion along rail 4. The type of propulsion is not critical, provided it allows operation in the relatively demanding conditions that prevail on board a ship. Chain drive or rack gearing of the wheel are most preferred.
The wheel 2 and deflection element 13 must have a radius which is greater than the smallest bending radius of the hose in order thereby to prevent the hose from being bent at an excessively small radius. In a preferred embodiment the radius of the wheel will be about 4 m. The deflection element 13 is shown as a fixed element having a cross- section which is a sector of a circle having a radius corresponding to the radius of the wheel 2. However, the deflection element may also be of other designs.
The height of the rail 4 above the deck will thus be such that the wheel 2 is always clear of the deck, and that the hose 1 is not pressed against the ship's deck by the wheel. It is preferred that a groove 6 is provided in the deck 5 for positioning the hose 1. The length of the rails is adapted to the length of the hose 1. In a preferred embodiment the rails are about 60 m in the length, which allows a hose length of about 120 m. At the stern the hose runs over booms 7 equipped with deflection element 13 which in the preferred embodiment are about 10 m in height, which ensures a fall of about 1 m between the boom 7 and the top of the wheel. When the hose is pulled in and the hose connector 12 rests against the boom 7, this allows draining of the hose since there is a fall from connector 12 to connection 8 at the other end of the hose.
In the embodiment illustrated in the figures, the hose, when pulled out and pulled in, will be exposed to a tensile force of about 500 kN, so that the tractive power of the centre of the wheel is twice that or about 1000 kN. During the pulling in and pulling out of the hose, the wheel will normally be driven at a rotation of about 0.25 revolutions per minute, which, with the given wheel radius, yields a hose pull-in rate or hose pull-
out rate of about 6 m per minute, or that the pay-out or pull-in of the effective part of the hose takes about 15 minutes.
To prevent too much of the hose being paid out or to prevent the end of the hose from being pulled so far in that connector 12 is pulled in from the boom 7, non-illustrated end stops may be provided on the rails 4. The wheel 2 may preferably be locked with a locking device such as a locking bolt, so that the wheel is prevented from moving when the wheel is in its rear position, i.e., the hose drawn out, and in its forward position, i.e., the hose drawn in.
Embodiment 2
Figure 5 is a lateral view of an alternative embodiment of the present apparatus with the hose 1 pulled in and with the hose 1 connected to the shuttle tanker 1 1 , respectively.
In this alternative embodiment the connection 8 between the tanks of the production unit and the hose is located on top of the boom 7. The hose runs up from the boom 7 over the wheel 2 and back in groove 6 in the deck 5 and runs out in an opening in the stern of the production unit. The opening in the stern of the production unit may be rounded or there may be provided a separate deflection element 13 as shown in the figure.
Above, the invention is described in a preferred embodiment where the apparatus is located on board a mobile offshore production unit. However, the present apparatus can of course be located on board other types of vessels for the transfer of fluid between the vessels. Of course, the apparatus can also be located on board shuttle tankers so that the hose is pulled on board the production unit from the shuttle tanker instead of the converse as described above.
Embodiment 3
The apparatus shown in lateral view in Figure 6 is an alternative embodiment where the boom 7 is omitted. The hose 1 is secured and connected in one end thereof to the ship's tank at connection 8 close to the stern of the ship, whence it runs in the longitudinal direction of the apparatus, preferably in a groove 6 towards the wheel 2. The hose then runs over the wheel and then back towards the stern of the ship. The weight of the hose 1 causes it to be pulled against the ship's deck. At the stern of the ship, the hose runs
out into the sea over a deflection element 13 which has a radius equal to or greater than the smallest bending radius of the hose. The deflection element 13 may be a smooth curved face or composed of a plurality of rollers.