CA2115690A1 - Method and apparatus for towing icebergs - Google Patents
Method and apparatus for towing icebergsInfo
- Publication number
- CA2115690A1 CA2115690A1 CA002115690A CA2115690A CA2115690A1 CA 2115690 A1 CA2115690 A1 CA 2115690A1 CA 002115690 A CA002115690 A CA 002115690A CA 2115690 A CA2115690 A CA 2115690A CA 2115690 A1 CA2115690 A1 CA 2115690A1
- Authority
- CA
- Canada
- Prior art keywords
- towline
- iceberg
- bag
- towing
- bags
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
- B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING
- B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
- B63B21/56—Towing or pushing equipment
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- Ocean & Marine Engineering (AREA)
- Revetment (AREA)
Abstract
A method is described for towing icebergs in which a towline is looped around the iceberg and the looped towline is pulled by the free ends thereof. According to the novel feature at least one approximately neutrally buoyant container of significant mass is attached to the towline adjacent to the iceberg, said container serving to hold the towline at or near the waterline during pulling. The neutrally buoyant container may be one or more bags holding sea water or one or more containers holding solid material, such as rocks and air.
Description
~ 1 Method and Apparatus for Towin~ Iceberqs Back~round of the Invention This invention relates to a method and apparatus for the towing of icebergs.
Offshore oil activity in iceberg infested waters exposes marine facilities and vessels to a risk of iceberg damage.
Offshore platforms, drillships and support vessels can be damaged by iceberg collision. Subsea installations such as pipelines, wellheads and moorings can be damaged by the scouring action of icebergs passing over them. Routine marine operations can be disrupted by the presence of icebergs in the oilfield area.
Iceberg towing is a means of reducing the effect of icebergs on offshore oilfield operations. In a towing lS procedure a boat, usually a tugboat, attempts to divert the trajectory of an iceberg by pulling it with an attached line or hawser. Many proposed methods for the towing of icebergs have been suggested and a small number of these have been evaluated experimentally. Only one towing method, that of encircling an iceberg with a floating polypropylene towline pulled by a tugboat, has found acceptance in routine offshore operations. In this method, known as the conventional iceberg towing method, the ends of the encircling polypropylene towline are shackled to a steel towing hawser wound out from a winch on the towing vessel. The polypropylene towline is pulled tight against the rear face of the iceberg as the vessel assumes its required heading and engages the tow.
There has been little subsequent advance in iceberg towing since this procedure was first proven off the coast of Newfoundland in 1974.
There are several important advantages to this conventional towing method including the fact that it can be carried out in adverse weather and requires only simple equipment and limited training of personnel. An important safety advantage of this approach is that it eliminates the necessity of closely approaching the iceberg to be towed. On the negative side, the tow success rate of this method is impaired by the potential loss of towing attachment. This loss of attachment is due to the tow rope slipping over the top of the iceberg, either because the iceberg is smooth and rounded with no grooves or protrusions on which the towline could register, or because the iceberg rolls in the water and dumps the towline. If the loss of attachment occurs while the towline is stretched under tension the line will snap back towards the vessel and frequently become snarled. When attachment is lost, reconnection is often slow and difficult.
The steel towing hawser must be winched on board, one end of the polypropylene tow rope must be freed and the rope redeployed around the iceberg. The delay associated with reattachment may be critical when icebergs are in close proximity to oilfield installations.
Several techniques have been tried to overcome problems with rope slippage and loss attachment in iceberg towing. One technique has been to use nets to enclose the iceberg rather than simply encircling it with a rope. As well, attempts have been made to apply the towing force to the iceberg at a point below its water line. This minimizes the rolling moment induced on the iceberg by the towforce and thus reduces the likelihood of rope slippage caused by iceberg rolling. In both cases, however, the hardware required to implement the concepts has proven cumbersome and difficult to handle at sea.
There have also been attempts to directly attach a towing device to an iceberg. With this arrangement, the towing device is embedded into the iceberg or connected to the iceberg surface such as to have an attachment strong enough to bear the full towing force, even if the iceberg should roll.
Among direct attachment mechanisms there may be mentioned suction cup devices, thermally embedded ice anchors, anchors embedded into the iceberg by drilling below the waterline with a submerged remotely operated vehicle (ROV), etc. All of these towing methods have met with very limited success as all have required the use of either a helicopter or ROV or they have required the direct boarding or very close approach to the iceberg to be towed. No direct attachment device suitable 211a690 , for routine use from an unassisted workboat in adverse weather and sea conditions has to date been developed, and the handling and logistics problems to be overcome before such a system could be considered functional are very great.
At the present time the conventional iceberg towing method is the best available. It is, therefore, the object of the present invention to provide an improved system which retains the safety and ease of operation of the conventional technique while decreasing the number of unsuccessful tows caused by towline slippage.
SummarY of the Invention This invention relates to an improved conventional iceberg towing system. With the system of the present invention the towline is provided with a large, neutrally buoyant mass which strongly resists any force tending to lift it from the water.
In conventional iceberg towing, the tow force is applied to a floating towline encircling the iceberg and is transmitted to the rear face of the iceberg, acting at or about the waterline. Loss of connection occurs when the towline slips over the iceberg either because the iceberg is smooth and the towline fails to register at the waterline and slides upward or because the iceberg rolls. Since the centre of mass of the iceberg lies well below the waterline the towforce generates a large rolling moment. In conventional iceberg towing, loss of connection always starts with the towline increasing its elevation relative to its initial position near the waterline.
This problem is overcome in the present invention by providing a towline of very large neutrally buoyant mass.
When the towline has been weighed down sufficiently the line cannot begin to slip upwards on the iceberg until enough tow force has been applied to lift the added weight. The weight of the towline used to prevent loss of connection is determined by the available towforce, iceberg roll stability, and the degree of slope of the rear facing surface of tne iceberg at the waterline.
21156~
-According to a preferred embodiment of the invention, the weight necessary to keep the towline at or near the waterline is provided by seawater entrapped in containment bags. With this method, the mass of the seawater moving with the towline assembly is high while the dry weight of the towline assembly remains low to facilitate handling during deployment and recovery.
Thus, in accordance with the improved system according to the preferred embodiment of the invention, a number, e.g. 2 to 5, of large discrete water filled bags are attached to the towline by shackles at evenly spaced intervals. These bags are spaced in accordance with the observed size of the iceberg to be towed such that the distance between the outermost bags approximately equals the-width of the rear face of the iceberg.
The bags are adapted for filling with water at time of deployment and for emptying of water when they are retrieved.
In another embodiment of the invention the bags are left filled with water and are moored in the ocean between uses.
Filling of the bags can be achieved by pumping them full of seawater with a high capacity pump or by towing them behind the tow vessel such that water flows into and expands the bag.
In a preferred embodiment of the invention the bags are configured to give a self-filling action upon immersion in the ocean. This action can be provided using a bag open to water at the top in combination with top end flotation, bottom end ballasting and one or more wall stiffening members to expand the bag to its full capacity.
In a preferred embodiment of the invention a recovery strap is attached to the bottom of each water bag for the purposes of emptying it of water at time of retrieval. The strap is preferably extended to a point on the towline at an appropriate position ahead of each bag. Then, as the towline is being retrieved, the recovery strap reaches the stern of the vessel before the bag does. When the recovery strap is retrieved on deck it is attached to an auxiliary winch and pulled in separately from the towline. Tnis upends the bag, - 211~690 causing the water to be dumped out and at the same time pulling the bag onto the deck. Once the bag is brought on deck, it is disconnected from the towline and can then be stored until next needed.
According to a further embodiment of the invention, instead of a number of discrete water filled bags, a single long cylindrical containment bag can be used in the manner of a boom which is filled with seawater. This long containment bag is attached to the towline at several points along its length. This long cylindrical containment bag can be filled by pumping it full of seawater with a high capacity pump or by towing it behind the tow vessel such that water flows into and expands the elongated bag. Restrictions along the bag can be used to control the flow of water along the length of the bag when the bag is subjected to asymmetrical lifting or towing forces. This embodiment would be well suited for mooring at sea between tows, in which configuration it would require less frequent filling and draining.
According to another embodiment of the invention, an iceberg towing boom can be assembled from rigid containers filled with ballast sufficient to make them approximately neutrally buoyant. As for example, metal or plastic containers filled partly with concrete or rocks and partly with air. For example, the containers can be made from a rigid plastic, such as polyethylene. The containers could be spaced along a rope or cable forming a boom which could be assembled at a shore location and then towed when needed to an offshore oil location. The flexible boom would be deployed around an iceberg in a manner similar to that used to deploy a conventional polypropylene towline. The boom could be constructed sturdily to resist storm damage or ice contact damage and would be left in the ocean for extended per~ods during which a potential iceberg towing requirement existed.
Brief Description of the Drawinqs Figure 1 is a schematic illustration of a towing system for icebergs;
Figures 2a and 2b are schematic illustrations of towing forces on an iceberg;
Figure 3 is a pictorial view of a towing arrangement according to the invention;
Figure 4 is a pictorial view of a further embodiment of the invention; and Figures 5a-5d are schematic illustrations of a self filling water bag arrangement.
Figure 1 shows a typical conventional towing system for icebergs. For this purpose the iceberg 10 is pulled by a thick polypropylene towline 11 and a typical towline for this purpose is one about 12cm diameter and 800m long. The ends of the towline 11 connect together by a shackle 12 which is connected to a heavy duty steel towing hawser 13 which is wound on to the main winch of an anchor handling tug 14.
With this technique, a marker buoy 16 is positioned and is connected by a buoy line 15 to towline lla. The tug 14a then moves in the direction shown around the iceberg 10 while paying out the polypropylene towline from the rear of the vessel. The tug continues around the iceberg 10 to locations 14b and 14c and then continues back to the location of the marker buoy 16 where the ends of the towline are connected together by the shackle 12. The tow vessel 14 then pays out additional steel hawser 13 from its main winch until it is a safe distance from the iceberg 10. At this time the tug is ready to commence the tow.
Figure 2a shows the typical problems encountered in a conventional iceberg tow. The towline floats on the surface of the water 19. Here, the iceberg 10 is shown with a sloping registration surface 20. It can be seen that the towing force 2la parallel to the waterline acting against the surface of the iceberg creates a tangential force 21b tending to lift the towline out of the water and upwards along the surface of the iceberg. Furthermore, the tow force imparts a rolling moment -21c about the centre of the iceberg 10a. The problem with this arrangement as described above is the ease with which attachment to the iceberg is lost either by the towline slipping upwards along the surface or the iceberg rolling.
Figure 2b shows the action of the present invention when used as an enhancement to conventional towing. Here it can be seen that the tangential component of the force 2ld exerted by the waterbag 24 opposes the upward tangential force 21b. This prevents the towline from slipping further upwards and reduces the rolling moment 21c applied to the iceberg 10.
Figure 3 shows an arrangement according to the present invention in which water bags 24 are connected to towline 11.
These water bags 24 are quite large, each typically weighing 15 tons or more. Two to five of these bags are typically positioned along the rear face of an iceberg. Each bag 24 is held by strapping 23 connected to a mounting collar 22 on the towline 11. Flotation collars 25 are also positioned on the towline on each side of collar 22.
The bottom end of each water bag 24 contains ballast weights in the form of dense metal or other heavy material.
Connected to the bottom of each bag 24 is a recovery strap 26 which is connected at its free end 27 to the towline 11. This strap 26 is typically about 25 meters long and is connected at a significant distance from the bag attachment point 22.
During hauling of the towline 11 the recovery strap 26 reaches the stern of the tug well before the bag 24. The strap 26 is long enough to be pulled well forward on the work deck so as to permit the crew to unshackle it from a mid deck position rather than near the stern. While the strap is being freed, the recovery of the towline is paused. Once free from the towline the recovery strap is wound in with an auxiliary winch, upending the bag and dumping its contained seawater while at the same time pulling it onto the deck. Once on the deck, the bag is disconnected from the towline and is stored until the next tow. This procedure is followed for each bag until all are on board.
An elongated bag arrangement is shown in Figure 4, with 211~6~0 -the elongated bag 31 mounted from the towline 11 by mounting straps 30. These mounting straps 30 are connected by shackles 34 to straps 35 surrounding the elongated water bag 31. The end of the water bag 31 includes a water inlet/outlet valve 32. Restrictions located at points 33 prevent water from sloshing along the length of the bag under asymmetrical lifting or towing forces.
Figure 5a-5d shows the action of a self-filling water bag. In Figure 5a the bag 24 is in its fully collapsed position at time of initial deployment in the ocean. Figure 5b shows the bag starting to fill with water which pours in through the opening 38 which is below the water surface.
Filling action is provided by the force of the ballast weight 36 sinking and pulling against the buoyancy of the flotation collars 25. This action stretches out the bag increasing its capacity and causing it to pull in water. The wall stiffening member 37 keeps the sides of the bag from collapsing during filling and ensures the bag fills quickly with its maximum capacity of water. Figure 5c shows the bag partially filled with water 39 flowing in opening 38, while Figure 5d shows the fully filled water bag.
Offshore oil activity in iceberg infested waters exposes marine facilities and vessels to a risk of iceberg damage.
Offshore platforms, drillships and support vessels can be damaged by iceberg collision. Subsea installations such as pipelines, wellheads and moorings can be damaged by the scouring action of icebergs passing over them. Routine marine operations can be disrupted by the presence of icebergs in the oilfield area.
Iceberg towing is a means of reducing the effect of icebergs on offshore oilfield operations. In a towing lS procedure a boat, usually a tugboat, attempts to divert the trajectory of an iceberg by pulling it with an attached line or hawser. Many proposed methods for the towing of icebergs have been suggested and a small number of these have been evaluated experimentally. Only one towing method, that of encircling an iceberg with a floating polypropylene towline pulled by a tugboat, has found acceptance in routine offshore operations. In this method, known as the conventional iceberg towing method, the ends of the encircling polypropylene towline are shackled to a steel towing hawser wound out from a winch on the towing vessel. The polypropylene towline is pulled tight against the rear face of the iceberg as the vessel assumes its required heading and engages the tow.
There has been little subsequent advance in iceberg towing since this procedure was first proven off the coast of Newfoundland in 1974.
There are several important advantages to this conventional towing method including the fact that it can be carried out in adverse weather and requires only simple equipment and limited training of personnel. An important safety advantage of this approach is that it eliminates the necessity of closely approaching the iceberg to be towed. On the negative side, the tow success rate of this method is impaired by the potential loss of towing attachment. This loss of attachment is due to the tow rope slipping over the top of the iceberg, either because the iceberg is smooth and rounded with no grooves or protrusions on which the towline could register, or because the iceberg rolls in the water and dumps the towline. If the loss of attachment occurs while the towline is stretched under tension the line will snap back towards the vessel and frequently become snarled. When attachment is lost, reconnection is often slow and difficult.
The steel towing hawser must be winched on board, one end of the polypropylene tow rope must be freed and the rope redeployed around the iceberg. The delay associated with reattachment may be critical when icebergs are in close proximity to oilfield installations.
Several techniques have been tried to overcome problems with rope slippage and loss attachment in iceberg towing. One technique has been to use nets to enclose the iceberg rather than simply encircling it with a rope. As well, attempts have been made to apply the towing force to the iceberg at a point below its water line. This minimizes the rolling moment induced on the iceberg by the towforce and thus reduces the likelihood of rope slippage caused by iceberg rolling. In both cases, however, the hardware required to implement the concepts has proven cumbersome and difficult to handle at sea.
There have also been attempts to directly attach a towing device to an iceberg. With this arrangement, the towing device is embedded into the iceberg or connected to the iceberg surface such as to have an attachment strong enough to bear the full towing force, even if the iceberg should roll.
Among direct attachment mechanisms there may be mentioned suction cup devices, thermally embedded ice anchors, anchors embedded into the iceberg by drilling below the waterline with a submerged remotely operated vehicle (ROV), etc. All of these towing methods have met with very limited success as all have required the use of either a helicopter or ROV or they have required the direct boarding or very close approach to the iceberg to be towed. No direct attachment device suitable 211a690 , for routine use from an unassisted workboat in adverse weather and sea conditions has to date been developed, and the handling and logistics problems to be overcome before such a system could be considered functional are very great.
At the present time the conventional iceberg towing method is the best available. It is, therefore, the object of the present invention to provide an improved system which retains the safety and ease of operation of the conventional technique while decreasing the number of unsuccessful tows caused by towline slippage.
SummarY of the Invention This invention relates to an improved conventional iceberg towing system. With the system of the present invention the towline is provided with a large, neutrally buoyant mass which strongly resists any force tending to lift it from the water.
In conventional iceberg towing, the tow force is applied to a floating towline encircling the iceberg and is transmitted to the rear face of the iceberg, acting at or about the waterline. Loss of connection occurs when the towline slips over the iceberg either because the iceberg is smooth and the towline fails to register at the waterline and slides upward or because the iceberg rolls. Since the centre of mass of the iceberg lies well below the waterline the towforce generates a large rolling moment. In conventional iceberg towing, loss of connection always starts with the towline increasing its elevation relative to its initial position near the waterline.
This problem is overcome in the present invention by providing a towline of very large neutrally buoyant mass.
When the towline has been weighed down sufficiently the line cannot begin to slip upwards on the iceberg until enough tow force has been applied to lift the added weight. The weight of the towline used to prevent loss of connection is determined by the available towforce, iceberg roll stability, and the degree of slope of the rear facing surface of tne iceberg at the waterline.
21156~
-According to a preferred embodiment of the invention, the weight necessary to keep the towline at or near the waterline is provided by seawater entrapped in containment bags. With this method, the mass of the seawater moving with the towline assembly is high while the dry weight of the towline assembly remains low to facilitate handling during deployment and recovery.
Thus, in accordance with the improved system according to the preferred embodiment of the invention, a number, e.g. 2 to 5, of large discrete water filled bags are attached to the towline by shackles at evenly spaced intervals. These bags are spaced in accordance with the observed size of the iceberg to be towed such that the distance between the outermost bags approximately equals the-width of the rear face of the iceberg.
The bags are adapted for filling with water at time of deployment and for emptying of water when they are retrieved.
In another embodiment of the invention the bags are left filled with water and are moored in the ocean between uses.
Filling of the bags can be achieved by pumping them full of seawater with a high capacity pump or by towing them behind the tow vessel such that water flows into and expands the bag.
In a preferred embodiment of the invention the bags are configured to give a self-filling action upon immersion in the ocean. This action can be provided using a bag open to water at the top in combination with top end flotation, bottom end ballasting and one or more wall stiffening members to expand the bag to its full capacity.
In a preferred embodiment of the invention a recovery strap is attached to the bottom of each water bag for the purposes of emptying it of water at time of retrieval. The strap is preferably extended to a point on the towline at an appropriate position ahead of each bag. Then, as the towline is being retrieved, the recovery strap reaches the stern of the vessel before the bag does. When the recovery strap is retrieved on deck it is attached to an auxiliary winch and pulled in separately from the towline. Tnis upends the bag, - 211~690 causing the water to be dumped out and at the same time pulling the bag onto the deck. Once the bag is brought on deck, it is disconnected from the towline and can then be stored until next needed.
According to a further embodiment of the invention, instead of a number of discrete water filled bags, a single long cylindrical containment bag can be used in the manner of a boom which is filled with seawater. This long containment bag is attached to the towline at several points along its length. This long cylindrical containment bag can be filled by pumping it full of seawater with a high capacity pump or by towing it behind the tow vessel such that water flows into and expands the elongated bag. Restrictions along the bag can be used to control the flow of water along the length of the bag when the bag is subjected to asymmetrical lifting or towing forces. This embodiment would be well suited for mooring at sea between tows, in which configuration it would require less frequent filling and draining.
According to another embodiment of the invention, an iceberg towing boom can be assembled from rigid containers filled with ballast sufficient to make them approximately neutrally buoyant. As for example, metal or plastic containers filled partly with concrete or rocks and partly with air. For example, the containers can be made from a rigid plastic, such as polyethylene. The containers could be spaced along a rope or cable forming a boom which could be assembled at a shore location and then towed when needed to an offshore oil location. The flexible boom would be deployed around an iceberg in a manner similar to that used to deploy a conventional polypropylene towline. The boom could be constructed sturdily to resist storm damage or ice contact damage and would be left in the ocean for extended per~ods during which a potential iceberg towing requirement existed.
Brief Description of the Drawinqs Figure 1 is a schematic illustration of a towing system for icebergs;
Figures 2a and 2b are schematic illustrations of towing forces on an iceberg;
Figure 3 is a pictorial view of a towing arrangement according to the invention;
Figure 4 is a pictorial view of a further embodiment of the invention; and Figures 5a-5d are schematic illustrations of a self filling water bag arrangement.
Figure 1 shows a typical conventional towing system for icebergs. For this purpose the iceberg 10 is pulled by a thick polypropylene towline 11 and a typical towline for this purpose is one about 12cm diameter and 800m long. The ends of the towline 11 connect together by a shackle 12 which is connected to a heavy duty steel towing hawser 13 which is wound on to the main winch of an anchor handling tug 14.
With this technique, a marker buoy 16 is positioned and is connected by a buoy line 15 to towline lla. The tug 14a then moves in the direction shown around the iceberg 10 while paying out the polypropylene towline from the rear of the vessel. The tug continues around the iceberg 10 to locations 14b and 14c and then continues back to the location of the marker buoy 16 where the ends of the towline are connected together by the shackle 12. The tow vessel 14 then pays out additional steel hawser 13 from its main winch until it is a safe distance from the iceberg 10. At this time the tug is ready to commence the tow.
Figure 2a shows the typical problems encountered in a conventional iceberg tow. The towline floats on the surface of the water 19. Here, the iceberg 10 is shown with a sloping registration surface 20. It can be seen that the towing force 2la parallel to the waterline acting against the surface of the iceberg creates a tangential force 21b tending to lift the towline out of the water and upwards along the surface of the iceberg. Furthermore, the tow force imparts a rolling moment -21c about the centre of the iceberg 10a. The problem with this arrangement as described above is the ease with which attachment to the iceberg is lost either by the towline slipping upwards along the surface or the iceberg rolling.
Figure 2b shows the action of the present invention when used as an enhancement to conventional towing. Here it can be seen that the tangential component of the force 2ld exerted by the waterbag 24 opposes the upward tangential force 21b. This prevents the towline from slipping further upwards and reduces the rolling moment 21c applied to the iceberg 10.
Figure 3 shows an arrangement according to the present invention in which water bags 24 are connected to towline 11.
These water bags 24 are quite large, each typically weighing 15 tons or more. Two to five of these bags are typically positioned along the rear face of an iceberg. Each bag 24 is held by strapping 23 connected to a mounting collar 22 on the towline 11. Flotation collars 25 are also positioned on the towline on each side of collar 22.
The bottom end of each water bag 24 contains ballast weights in the form of dense metal or other heavy material.
Connected to the bottom of each bag 24 is a recovery strap 26 which is connected at its free end 27 to the towline 11. This strap 26 is typically about 25 meters long and is connected at a significant distance from the bag attachment point 22.
During hauling of the towline 11 the recovery strap 26 reaches the stern of the tug well before the bag 24. The strap 26 is long enough to be pulled well forward on the work deck so as to permit the crew to unshackle it from a mid deck position rather than near the stern. While the strap is being freed, the recovery of the towline is paused. Once free from the towline the recovery strap is wound in with an auxiliary winch, upending the bag and dumping its contained seawater while at the same time pulling it onto the deck. Once on the deck, the bag is disconnected from the towline and is stored until the next tow. This procedure is followed for each bag until all are on board.
An elongated bag arrangement is shown in Figure 4, with 211~6~0 -the elongated bag 31 mounted from the towline 11 by mounting straps 30. These mounting straps 30 are connected by shackles 34 to straps 35 surrounding the elongated water bag 31. The end of the water bag 31 includes a water inlet/outlet valve 32. Restrictions located at points 33 prevent water from sloshing along the length of the bag under asymmetrical lifting or towing forces.
Figure 5a-5d shows the action of a self-filling water bag. In Figure 5a the bag 24 is in its fully collapsed position at time of initial deployment in the ocean. Figure 5b shows the bag starting to fill with water which pours in through the opening 38 which is below the water surface.
Filling action is provided by the force of the ballast weight 36 sinking and pulling against the buoyancy of the flotation collars 25. This action stretches out the bag increasing its capacity and causing it to pull in water. The wall stiffening member 37 keeps the sides of the bag from collapsing during filling and ensures the bag fills quickly with its maximum capacity of water. Figure 5c shows the bag partially filled with water 39 flowing in opening 38, while Figure 5d shows the fully filled water bag.
Claims (15)
1. A method for towing icebergs which comprises looping a towline around the iceberg and pulling the looped towline by the free ends thereof, characterized in that at least one approximately neutrally buoyant container of significant mass is attached to the towline adjacent to the iceberg, said container serving to hold the towline at or near the waterline during pulling.
2. A method according to claim 1 wherein the neutrally buoyant container is a bag.
3. A method according to claim 1 wherein the bag contains seawater as the mass.
4. A method according to claim 1 wherein the neutrally buoyant container is a metal or plastic container partially filled with solid material and partially filled with air.
5. A method according to claim 4 wherein the solid material comprises concrete or rocks.
6. A method according to claim 3 wherein a plurality of water filled bags are used.
7. A method according to claim 3 wherein a single water filled bag is used.
8. A method according to claim 7 wherein said single bag is an elongated bag attached to the towline.
9. A method according to claim 8 wherein the elongated bag has internal baffles to prevent flow of water along its length.
10. A method according to claim 3 wherein the bags are retrieved, emptied and detached after use.
11. A method according to claim 3 wherein the bags are filled by pumping.
12. A method according to claim 3 wherein the bags are filled by dragging through the water.
13. A method according to claim 3 wherein the bags are self-filling.
14. A method according to claim 4 wherein the container is a rigid plastic container.
15. A method according to claim 14 wherein the containers are assembled into a boom.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002115690A CA2115690A1 (en) | 1994-02-15 | 1994-02-15 | Method and apparatus for towing icebergs |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002115690A CA2115690A1 (en) | 1994-02-15 | 1994-02-15 | Method and apparatus for towing icebergs |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2115690A1 true CA2115690A1 (en) | 1995-08-16 |
Family
ID=4152913
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002115690A Abandoned CA2115690A1 (en) | 1994-02-15 | 1994-02-15 | Method and apparatus for towing icebergs |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2115690A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU205321U1 (en) * | 2021-03-24 | 2021-07-08 | Публичное акционерное общество "Нефтяная компания "Роснефть" (ПАО "НК "Роснефть") | DEVICE FOR TOWING ICE FORMATIONS |
-
1994
- 1994-02-15 CA CA002115690A patent/CA2115690A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU205321U1 (en) * | 2021-03-24 | 2021-07-08 | Публичное акционерное общество "Нефтяная компания "Роснефть" (ПАО "НК "Роснефть") | DEVICE FOR TOWING ICE FORMATIONS |
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