TECHNICAL FIELD

The present invention relates to sea water suction hoses as well as related systems and methods.

BACKGROUND

Sea water suction lines or hoses are used for suction of cold sea water from great sea depths in order to use the water for process cooling. The normal working depths vary between approximately 90-160 meters, but 600-1000 meters are also possible. In fact, no real depth limitation exist, it is possible to go even deeper if it would be beneficial. The flow velocity in such a suction line is typically in the range of 2-3 m/s.

To prevent marine growth in the hose, hypochlorite is injected at the water intake level. The hypochlorite is lead through an injection line from a dedicated system which is located at a ship, an oil platform or another marine structure at the sea surface level, to the water intake level where it is distributed.

The injection line is commonly installed in the sea water suction hose at the same time as this is assembled, one injection line section connected to each end of a suction hose section by a termination piece. The sea water suction hose is built up by suction hose sections, and in each suction hose section an injection line section is installed. When two sea water suction hose sections are connected, the two injection line sections also need to be connected. This connection is both cumbersome and time consuming, which also makes it expensive.

Further, if there is a malfunction in the injection line, the whole sea water suction hose needs to be taken out of the water and on board the marine structure in order to provide access to the damaged portions of the injection line. This requires dismantling of the whole hose in order to reach the damaged portions of the injection line. To dismantle the hose, all hose sections and injection line sections, need to be separated one by one and taken up to the deck of the marine structure. This is a very costly and time- consuming project.

A known type of injection line is disclosed in W02008/017937A1. In this sea water suction hose, a hypochlorite hose section is attached to each hose section prior to assembly of the suction hose. One problem with this type of injection line is the large interference required when the injection line is installed, but also when it needs inspection, repair or needs to be exchanged. From the above it is understood that there is room for improvements.

SUMMARY

An object of the present invention is to provide a sea water suction hose which is improved over prior art and which eliminates or at least mitigates the drawbacks discussed above. More specifically, an object of the invention is to provide a hypochlorite injection line arrangement which is permitted to be recovered for inspection or to be exchanged without any dismantling operation of the suction hose sections. These objects are achieved by the technique set forth in the appended independent claims with preferred embodiments defined in the dependent claims related thereto.

In a first aspect, there is provided a method for installing an injection line into a sea water suction hose. The suction hose includes a number of interconnected hose sections, and the method comprises the steps of: pulling the injection line through line receiving elements of the hose sections from the top section of the hose to the bottom section by means of a guiding strand led around a strand guiding means; and connecting the injection line to a spreader at the bottom of the sea water suction hose. An advantage with this method is that the whole injection line is inserted into the complete sea water suction hose, and not within each hose section at a time. I n one embodiment, each line receiving element of the hose sections is prov ided with two openings. This is advantageous in that the injection line can run through one of the openings, and the guiding strand can run through the other. Prior to the pulling step a first leg of the guiding strand may be guided through one of the openings of the line receiving elements of each hose section. i n one embodiment, a second leg of the guiding strand is guided through the other of the openings of the line receiving elements.

The injection line may be connected to the first leg of the guiding strand. Thereby, the injection l ine may be brought down through the hose by means of the guiding strand.

In said pulling step the second leg of the guiding strand may be pulled upwards, and the first leg, together with the injection l ine may then be brought downwards through the line of line receiving elements until the injection line reaches the bottommost suction hose section. This is an efficient way of installing an injection line into a marine sea water suction hose. Furthermore, it is a reversible method, in that the injection line may be retracted from the hose again, by means of the guiding strand.

The top end of the injection line may be connected to a connection element, and the bottom end to a spreader. The connection element connects the injection l ine wi th a tank of e.g. hypochlorite, and the spreader distributes the hypochlorite to the sea water at the entrance of the hose.

Preferably, the injection line is continuous. This is advantageous since the whole injection line may be retracted in order to be exchanged, or when it is in need of maintenance. Dismantling of the whole suction hose is not required, which saves a lot of time and costs. in a second aspect, there is prov ided a kit for assembling a sea water suction hose system. This kit comprises a number of hose sections which are connectable to each other. Each hose section is provided with at least one line receiving element for guiding of a strand and an injection line. The kit further comprises a hang off cup connectable to a marine structure, and a hang off spool connectable to an uppermost hose section and which is adapted to extend along a side of a marine structure. The kit also comprises a strainer which is connectable to a bottommost hose section and which is provided with a spreader for dispensing a liquid. Furthermore, the system comprises an injection line for a liquid, a connecting dev ice for connecting the injection line to the spreader, and a guiding strand for guiding the injection line through each line receiving element.

In one embodiment, the injection line is continuous. This is advantageous when assembling the hose, as well as when the injection line needs to be repaired or exchanged.

In one embodiment the liquid led in the injection line is hypochlorite. This is advantageous since hypochlorite is effective in preventing marine growth, which is otherwise a problem in this type of application. In a third aspect, it is proposed to use a guiding strand for installation and removal of an injection line, preferably for hypochlorite, in a sea water suction hose system having a number of hose sections. The use of a guiding strand or rope to install the injection line is very efficient and cost saving. It is also possible to use the guiding rope as a recovery rope in order to retract the injection line from the suction hose when this is desired for any reason without dismantling the rest of the suction hose.

In a fourth aspect, there is provided a method of assembling a seawater suction hose system. The method comprises the steps of: guiding a first leg of a guiding strand through a female part of a connecting device arranged in the strainer of the sea water suction hose system, and through at least one line receiving element of a first hose section; guiding a second leg of the guiding strand beside the female part of the connecting dev ice and through the line receiving element of the first hose section; connecting additional hose sections to the first hose section and guiding the first and second legs of the guiding strand through the line receiving element of each additional hose section; connecting a male part of the connecting dev ice to an injection line, preferably for hypochlorite; connecting the first leg of the guiding strand to the male part of the connect ing dev ice; pulling the second leg of the guiding strand upwards; bringing the first leg, together with the male part of the connecting device and the injection line, downwards through the line receiving elements until the male part of the connecting device reaches the strainer below the bottommost suction hose section; connecting the male part of the connecting device to the female part of the connecting device; and connecting the top end of the injection line to a connection element located on a marine structure.

The second leg of the guiding strand may be stored at sea level for future maintenance. The guiding strand may function as a recovery strand, and the injection line may be retracted by means of the strand. This arrangement allows for easy retraction of the in jection line, without dismantling of the remaining suction hose.

The injection line may be retracted by means of the guiding strand. This is

advantageous in that the whole injection line may be retracted in one piece, without dismantling the suction hose.

In a fifth aspect, there is provided a hose section for a sea water suction hose. This hose section comprises at least one line receiving element which is configured to receive an injection line. Further, the hose section comprises a guiding strand configured to be used for installation and removal of the injection line. An advantage of this sea water suction hose compared to known hoses is that the injection line is continuous through the whole extend of the suction line. Further, it is possible to insert and remove the whole injection line in one continuous piece. This is beneficial when the injection line has been damaged and needs to be exchanged, or when it is in need of maintenance. With this insertion removal system, the injection line may be brought out of the structure and up to the marine structure alone; the rest of the hose remains in the water.

The line receiving element may comprise a protrusion which protrudes radial ly from the inner wall of the hose section. The line receiving element may comprise two openings, one for the guiding strand and one for the injection line. This protrusion together with the openings form a system or a path for both the guiding strand and for the injection line, thus allowing for a continuous injection line along the whole extent of the sea water suction hose.

I n one embodiment, the l ine receiving element comprises a circular portion extending along an inner or outer surface of the hose section. This is beneficial if line receiving elements are desired at other locations than in the joint between two hose sections. i n another embodiment, the l ine receiving element is arranged in a connection flange for connection of two hose sections. This line receiving element may be a spacer between the two hose sections. It is favourable to integrate the line receiving element in an existing component of the hose in order not to add extra components. The line receiving element may be arranged at a mid portion of the hose section. It is advantageous to use more line receiving elements in addition to the ones arranged in the connection area between two hose sections. This allows for a more stable arrangement, since the distance between two line receiving elements is shorter. The line receiving element is preferably one of the following alternatives: a spool piece, a spacer, or a dedicated part attached to the hose section. Depending on the composition of the hose more than one of the alternatives may be used in the same suction hose.

Preferably, the injection line of the hose section is for hypochlorite. This is

advantageous since hypochlorite is effective in preventing marine growth. in a sixth aspect, there is prov ided a sea water suction hose system which comprises a number of interconnected hose sections. The system further comprises a hang off cup connected to a marine structure and a hung off spool connected to an uppermost hose section and adapted to extend along a side of the marine structure. Furthermore, the system comprises a strainer connected to a bottommost hose section and provided with a spreader for dispension of a liquid. The strainer comprises a tank for the guiding strand. The injection line is connected to the spreader by means of a connecting device.

Preferably, the injection line is continuous. This is advantageous since the whole injection line may be retracted in order to be exchanged, or when it is in need of maintenance. Dismantling of the whole suction hose is not required, which saves a lot of time and costs.

Preferably, the injection line is retractable by means of the guiding strand. To keep the guiding strand within the hose for use as a recovery rope is beneficial in the event of a malfunction in the injection line, or when it for other reasons need to be inspected or brought out of the suction hose.

The liquid in the injection line may be hypochlorite. This is advantageous since hypochlorite is effective in preventing marine growth, which is otherwise a problem in this type of application.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the inv ention will be described in the following; references being made to the appended diagrammatical drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

Fig. 1A is a sectional side view of a prior-art sea water suction hose.

Fig. IB illustrates a number of sea water suction hose systems in accordance with an embodiment of the invention.

Fig. 2 is a cross sectional view of a sea water suction line as shown in Fig. IB. Fig. 3 is a partially cut-out view of a bottom part of the sea water suction hose shown in

Fig. 2.

Fig. 4 is a partially cut-out view of a middle part of the sea water suction hose shown in Fig. 2.

Fig. 5 is a partially cut-out view of a middle part of the sea water suction hose shown in

Fig. 2.

Fig. 6 is a partial ly cut-out view of a bottom part of the sea water suction hose shown in Fig. 2.

Fig. 7 is a partially cut-out view of a bottom part of the sea water suction hose shown in Fig. 2.

Fig. 8 is a partially cut-out close up of a rope tank shown in Fig. 7.

Fig. 9 is a schematical side view of a sea water suction hose according to one embodiment. DETAILED DESCRIPTION

Hereinafter, certain embodiments will be described more fully with reference to the accompanyin drawings. The inv ention may, however, be embodied i n many di fferent forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will ful ly convey the scope of the invention, such as it is defined in the appended claims, to those skilled in the art.

A prior-art sea water suction line 100 with a hypochlorite injection line 1 10 installed is shown in Fig. 1A. The hose 100 comprises a number of hose sections 101, 102 which are connected by bolted flanges 120. The injection line 1 10 comprises sections 1 1 1 , 1 12 which are connected by couplings 130 at the same longitudinal level as the coupling between the suction hose sections 101 , 102.

A number of complete sea water suction hose systems according to one embodiment are shown in Fig. IB. A number of hose systems 202 extend from a deck of a ship or similar marine structure 320, such as an oil rig or platform, and into the water W. Each sea water suction hose system 202 comprises a hang off cup 311 connected to the marine structure 320, a hang off spool 3 10 connected at the top to the hang off cup 3 1 1 and at the bottom of the first of a number of interconnected hose sections 201, and a strainer 200 arranged below the bottommost hose section 201.

With reference to Fig. 2, a sea water suction hose 202 according to one embodiment is shown. This marine hose system comprises a hang off cup 3 1 1 , a hang off spool 310, a number of hose sections 201 a-f and a strainer 200. The hose sections 20 la-f are interconnected by couplings 205 comprising connection flanges 295 (shown in Figs 4- 5). A strand or cord, here in the shape of a guiding rope 230, extends through the whole hose system, from the hang off cup 3 1 1 at the top to the strainer 200 at the bottom. Also extending from the top to the bottom is a continuous in jection line 270, which leads hypochlorite or other marine growth preventing liquid from a system onboard the marine structure (320) to the water intake level in the strainer 200.

In Figs 3-6 the installation sequence of a hypochlorite injection line 270 is shown at different stages.

In Fig. 3 there is shown a strainer 200 connected to the bottommost sea water hose section 201 f according to one embodiment. The cut-out shows the hypochlorite spreader 210 connected to the female part 220 of the connecting device. Below the spreader 210 there is a rope guiding member or a rotatable return sheave 290. The first leg 230a of the guiding recovery rope 230 is lead from the rope tank 240 ( Fig. 8) v ia the return sheave 290, through the female part 220 of the connecting device and further upwards. The second leg 230b of the guiding removal rope 230 extends from the rope tank 240 (Fig. 8) via the return sheave 290, beside the female part 220 of the connecting device and further upwards through the water suction hose 200. When a hypochlorite injection line 270 is to be installed, the second leg 230b is pulled upwards, whereby the first leg 230a moves downwards, bringing with it the injection line 270, which is connected to the rope 230. Further to Fig. 4, a coupling 205 between two hose sections 201 a, 201 b is shown as wel l as a line receiving element 260, in this embodiment located on the inside of the hose 202. The l ine receiving element 260 comprises a circular portion 261 integrated in a connection flange 295 arranged between the hose sections 201 a-b. Furthermore, line receiving element 260 comprises a protrusion 262 with two through openings 263, 264, which protrude inwards towards the inner of the hose 202.

Through the opening 263 runs the first leg 230a of the rope 230 and through the opening 264 runs the second leg 230b. Both rope legs 230a, 230b are shown as cropped for illustrative purposes, they both extend upwards through the string of hose sections 201 af.

During assembly of the suction line, the two legs 230a, 230b are pulled upwards and routed in the dedicated openings 263, 264 in the guiding protrusions 262 which are regularly distributed along the line at each hose section 20 1 a, 201 b flange area.

The guiding openings 263 , 264 are provided with regular intervals within the suction line 202. The protrusion 262 in which they are placed may be integrated in a spacer, placed between two hose sections 201, but it may just as well be welded to a spacer or bolted to a spool piece (not shown). It may also be bolted or welded directly in the hose flange (not shown).

The same view of the two hose sections 201a, 201b as in Fig. 4 is shown in Fig. 5. The difference is that in Fig. 5 the first leg 230a of the rope 230 has been pulled upwards, compared to the situation shown in Fig. 4. Thus, the hypochlorite injection line 270 together with a male part 280 of the connecting device, here embodied by a hot stab, has moved down through the string of hose sections 201 a-f and are now arranged above the line receiving element 260. When the first leg 230a is pulled further upwards, the hot stab 280 and the injection line 270 will pass through the opening 264 on their way down. i n Fig. 6 the hypochlorite injection line 270 and the hot stab 280 have reached the strainer 200 connected to the bottommost hose section 201 f. The hot stab 280 is now connected to the receiving element 220 and the hot stab 280 may be automatically locked into position with the receiving element 220, or it may be locked by means of an external intervention, e.g. by a remotely operated underwater vehicle (R.OV). At sea level the other end of the injection line 270 will be connected to a connection element (271) for continuous or regular supply of hypochlorite into the sea water.

Fig. 6 also shows how the rope 230 runs in the rotatable return sheave 290, by which rope 230 the injection li ne 270 may be pulled up to the surface level, e.g. for reparation purposes, and then returned down into the string of hose sections 201 a-f again, by means of the guiding recovery rope 230. I n other embodiments (not shown), the return sheave may be a stationary rope guiding means or another type of rotatable member. The bottom part of the strainer 200 and a rope tank 240 for installation purposes is shown in Fig. 7. The rope tank 240 is used when the string of hose sections 201 a-f is assembled. The tank 240 is divided into two compartments 251 , 252 by a partition wail 250. The first leg 230a of the guiding removal rope 230 is wound up in the first compartment 251 , and the second leg 230b is wound up in the second compartment 252.

When the string of hose sections 201 a-f is to be assembled, the first 230a and the second 230b legs of the rope 230 are lead through the line receiving elements 260, as described in connection with Figs 3-4. More of the rope 230 is collected from the tank 240 as additional hose sections 201 are added. When the hose 202 is completed the rope 230 is pulled up in order to come into contact with the return sheave 290, as shown in Fig. 6. At this stage the rope tank 240 has fulfilled its purpose and is not used anymore.

Fig. 8 shows a close-up of the rope tank 240 with the rope 230 wound up in the two compartments 25 1 , 252. i n an alternative embodiment, shown in Fig. 9, the l ine receiving element 260 with the protrusion 262 is provided on the outside of the hose 202, in connection with a coupling 205. Thus, the injection line 270 is provided on the exterior of the hose 202 comprising hose elements 201 a-c. This location of the injection line 270 provides for extra easy access.

It should be appreciated that the inventive concept is not l imited to the embodiments described herein, and many modifications are feasible within the scope of the inv ention set forth in the appended claims. For example, the invention is not limited to the distribution of hypoch lorite; it could be any form of liquid prev enting marine growth in the water.