Ship and a method adapted to generate tensile stresses in a pull line extended between the ships and an object to which a pull is to be applied

The present invention concerns a ship which is adapted to generate tensile stresses in a pull line extending between a ship and an object to which a pull is to be applied. The ship, which includes at least one line pull winch, includes equipment in the form of a holding line and a holding line anchorage which is laid out in the desired tensioning direction from the object with a view to generating tensile stresses. At its stern, the ship moreover has at least one line entry opening and force-absorbing line supports for the pull and holding lines. At least one of the supports is adapted to guide the line concerned in a direction toward the line pull winch. The force-absorbing line supports are interconnected via a tension-absorbing constructional element. The resulting ship is capable of generating very high pull forces in a pull line extending in an arbitrary direction from an object to which a pull is to be applied. The invention also concerns a method of applying a pull from a ship of the invention to a pull line, and a use of a ship of the invention for testing the tensile strength of anchorages, for applying a pull to grounded ships and for applying a pull to vessels during towing.

FIELD OF THE ART 
The present invention concerns a ship which is adapted to generate tensile 
stresses in a pull line extending between the ship and an object to which 
a pull is to be applied, said ship comprising at least one line pull 
winch. 
MOST IMMEDIATE PRIOR ART 
The marine industry today includes ships and barges which are used for 
generating tensile stresses in lines which extend between a ship and an 
object. The ships/barges are frequently specially designed and can be used 
only for a specific purpose. The objects may e.g. be anchorages for 
vessels and offshore structures, grounded ships and ships to be towed. 
Thus, within e.g. the offshore industry, specially built anchor handling 
ships and large crane vessels are used for handling the paying-out and 
testing of anchoring lines/anchor systems for the production systems. The 
reason is that today production systems are established at a water depth 
of up to 800-1200 meters, which makes unusually high demands on the 
ships/equipment to be used in order for the paying-out and testing of 
anchoring lines/anchor systems to be handled rapidly and reliably. 
It is not unusual that the minimum holding power requirement of the 
anchoring systems is 700-800 tons for each anchoring line in the anchoring 
system. 
Therefore, the certification authorities make particularly high demands on 
equipment and testing of the anchoring lines of the anchor systems in 
order to be sure that the systems satisfy the necessary holding power 
requirements. 
Testing of an anchoring line in a laid anchoring system is impeded to a 
high degree by the circumstance that the anchored production system is 
constructed such that the system cannot be subjected to large test forces 
in a direction opposite to the anchoring line to be tested. Testing must 
therefore be performed when the line concerned is released from the 
system, which involves increased difficulty in handling the testing and 
necessitates execution of time-consuming and laborious operations before 
the testing is completed. 
The use of the ships, crane vessels and equipment known today thus involves 
very difficult and time-consuming operations when the anchor lines are to 
be laid out and subsequently tested. 
Accordingly, there is a long-felt need for a simplification of these 
operations and for a simultaneous reduction in the time required to 
perform these operations. 
U.S. Pat. No. 2,988,892 discloses an anchoring system comprising 
precemented anchoring means. The upper ends of two anchoring lines 
positioned opposite each other are connected via tackles directly with 
respective winches on an intermediate barge. The document just teaches 
pulling at a specific angle and in a specific direction and suggests no 
structure that allows tensioning of the lines. 
However, the barges have not been used in practice, as they are exclusively 
contemplated for the testing and laying-out of small and simple anchoring 
system, and further it has been necessary to employ tug boats for slow and 
cumbersome transport of the barges. Finally, the barge will be unsafe in 
windy weather, because it does not have the required seaworthiness, so 
that it is dangerous to be on board the barge. 
OBJECT 
The object of the invention is to provide a versatile ship of the type 
mentioned in the opening paragraph, which is capable of safely and 
efficiently generating tensile stress in arbitrary directions in a pull 
line extending between the ship and an object without undue time 
consumption. 
THE NOVELTY OF THE SHIP 
The ship of the invention is novel in that it comprises equipment in the 
form of a holding line and a holding line anchorage which is laid out in 
the desired tensioning direction from the object with a view to generating 
said tensile stresses, that, at its stern, the ship moreover comprises at 
least one line entry opening as well as force-absorbing line supports for 
the pull and holding lines, at least one of said supports being adapted to 
guide the line concerned in a direction toward the line pull winch, and 
that the force-absorbing line supports are interconnected via a 
tension-absorbing constructional element. 
ADVANTAGES 
The invention thus provides a ship which, in relation to the known ships, 
is surprisingly capable of generating very high tensile forces in a pull 
line which extends in an arbitrary direction from an object to which a 
pull is to be applied. 
A further advantage of the invention is that the lines are introduced into 
the ship in an extremely safe and efficient manner, thereby reducing the 
risk of accidents. 
ADVANTAGES OF ADVANTAGEOUS EMBODIMENTS 
Expedient embodiments are defined in claims 2-10. 
According to claim 2, the constructional element is adapted to absorb 
tensile strengths above 200 tons, thereby allowing the ship to used for 
tasks requiring particularly high forces. 
In another embodiment, the line supports are fixedly mounted on the 
constructional element, which is detachably secured at the quarterdeck of 
the ship. As a result, the line supports and the constructional element 
may be removed from the deck of the ship when they are not in use. This 
results in a versatile ship which may be employed for several different 
purposes. 
According to claim 4, the constructional element is plate-shaped. This 
provides a compact structure, which is also capable of absorbing large 
tensile strengths. 
In another advantageous embodiment of the Invention, the quarterdeck of the 
ship comprises hydraulically activatable locking parts to position and 
secure the constructional element. This ensures simple and efficient 
attachment of the constructional element. In a particularly expedient 
embodiment, the locking parts are inclined, so that the constructional 
element is fixed both horizontally and vertically. 
According to claim 6, the line supports are provided in alignment with the 
line entry openings at the side of the ship. This ensures that the lines 
are guided perpendicularly inwards toward the ship during tensioning, 
thereby obviating the need for further line supports. 
When the line supports are provided with rotatably mounted guide rollers, 
the lines are safely given a directional change under a high load with a 
minimum loss of friction. 
According to claim 8, the ship comprises line pull winches to apply a pull 
to both of said lines. This results in fast and efficient line haul-in and 
a fixing force twice as large. 
According to claim 9, the ship comprises dynamometer means which allow 
measurement of the tension generated in the pull line. This may be an 
advantage particularly when it is desired to generate a specific tensile 
stress in the lines, e.g. during testing. 
Finally, according to claim 10, a block is secured at one end of a line to 
which a pull is applied, through which block an auxiliary line is run, one 
end of said auxiliary line being fixed, the other end of said auxiliary 
line being run to the line pull winch to provide a 1:2 change in force 
between the winch and the line to which a pull is to be applied. This 
ensures that a great force may be generated in the pull line. 
The present invention also concerns a method of applying a pull from the 
ship to a pull line extending between the ship and an object to which a 
pull is to be applied. The method is unique in that a holding line 
anchorage is laid out in the desired tensioning direction from the object, 
from which anchorage a holding line extends back to the ship, and that the 
pull line and/or the holding line is subsequently hauled in from the ship 
while retaining the other of the lines. This ensures that the object may 
be subjected to a pull in an arbitrary direction. 
The invention moreover concerns a use of a ship for testing the tensile 
strength of anchorages for lines to moor vessels in the open sea, for 
testing the tensile strength of anchorages for lines to moor offshore 
structures in the open sea, for applying a pull to grounded ships during 
salvage of these, and for applying a pull to vessels during towing of 
these. 
MODE OF OPERATION 
When the winch of the ship hauls in the holding line and/or the pull line, 
the lines will be tensioned in extension of each other so as to be 
stretched between the holding line anchorage and the object to which a 
pull is to be applied. 
When said line or lines are hauled in additionally, the pulling force in 
the pull line will be transferred from the line support of the pull line 
on the ship and via the tension-absorbing constructional element to the 
holding line support on the ship, and from there via the holding line 
further on to the holding line anchorage.

DETAILED DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS 
The ship 1 shown in FIG. 1 is adapted to generate tensile stresses in a 
pull line 4 extending between the ship 1 and an object (not shown) to be 
subjected to a pull. 
The ship 1 comprises two line pull winches 7, 8. In addition, the ship 1 
comprises a holding line 5 and a holding line anchorage 6 paid out in the 
desired tensioning direction from the object to generate tensile stresses. 
The ship 1 moreover comprises two line entry openings 11, 12 at its stern 
and force-absorbing line supports 16, 17 for the pull and the holding 
lines. The force-absorbing line supports 16, 17, which are adapted to 
guide the line concerned in a direction toward the line pull winches 7, 8, 
are interconnected via a tension-absorbing constructional element 18. 
The line supports 16, 17 are fixedly mounted on the constructional element 
18 so that the forces applied by the lines 4, 5 to the line supports 16, 
17 are safely transferred to the constructional element 18. 
In the embodiment shown, the constructional element 18 is provided as an 
upper plate and a lower plate positioned in parallel opposite each other 
with a space between them. The constructional element might also have 
other shapes, as the term constructional element is intended to mean 
beams, plates, etc. which have a sufficient strength to absorb the loads. 
In the embodiment shown, the constructional element 18 is detachably 
secured at the quarterdeck 13 of the ship. It is ensured hereby that the 
constructional element 18 can be removed from the quarterdeck 13 of the 
ship so that the ship 1 may also be used for other types of tasks, without 
the constructional element 18 taking up undue space. Thus, the 
constructional element having the premounted line supports 16, 17 arranged 
on the plates, may be installed quickly on the ship when required, 
resulting in a versatile ship useful for several purposes. 
The constructional element 18 is secured and positioned with respect to the 
ship 1 via hydraulically activatable locking parts 24, 25 which are 
mounted in the quarterdeck 13 of the ship. The locking parts 24, 25 are 
provided as two pairs of legs which, when being activated, move obliquely 
upwards from the quarterdeck 13 toward each other by means of a hydraulic 
device (not shown). The constructional element 18 thus comprises 
corresponding openings so that the constructional element 18 is fixed 
vertically as well as horizontally when the locking parts 24, 25 are moved 
up through the openings in the constructional element 18. 
The tension-absorbing constructional element 18 is adapted to absorb 
tensile forces above 200 tons in the embodiment shown. The ship 1 may 
hereby be used for generating extremely great tensile stresses. 
The ship moreover comprises two line entry openings 11, 12 which are 
arranged in the starboard side and the port side, respectively, of the 
ship 1 at the stern of the ship. The line entry openings 11, 12 are 
arranged at a level above the deck 13 of the ship. In use, the pull line 4 
is passed from the object and the holding line 5 from the holding line 
anchorage through their respective line entry openings 11, 12 and further 
via the line supports 16, 17 to the line pull winches 7, 8, see FIG. 2. 
During tensioning of the lines, the high forces will cause the ship 1 to 
assume such a position that the lines enter the deck substantially 
perpendicularly to the fore-and-aft direction of the ship, as appears from 
FIG. 1. 
In the embodiment shown, the line supports 16, 17 are provided in alignment 
with the line entry openings 11, 12 at the side of the ship, and are 
formed by two rotatably mounted guide rollers. The guide rollers, which 
are mounted on their respective vertical shafts 19, 20 secured to the 
upper and lower plates in the constructional element 18, are arranged 
between the upper plate and the lower plate. 
As shown in FIG. 2, the line supports 16, 17 are arranged such that, in 
use, they guide the lines 4, 5 from a direction which is substantially 
perpendicular to the fore-and-aft direction of the ship to a direction 
which is substantially parallel with the fore-and-aft direction of the 
ship and which extends in a direction toward the line pull winches 7, 8. 
In use, the guide rollers thus guide the lines 4, 5 from the line entry 
openings 11, 12 to the line pull winches 7, 8 in a safe and reliable 
manner. 
The ship 1 also comprises two line pull winches 7, 8 to apply a pull to 
both of said lines. Each line pull winch 7, 8 consists of two drums 9, 10, 
21, 22. Depending on the desired pull strength and the amount of line to 
be pulled in to generate a tensile stress in the pull line 4, one or two 
line pull winches 7, 8 and one or more drums may be used. Each of the 
winches 7, 8 can pull with a force of up to about 850 tons in the 
embodiment shown. 
As shown in FIG. 1, the line pull winches 7, 8 are placed approximately 
amidships with the axes of the drums 9, 10, 21, 22 extending horizontally 
and perpendicularly to the fore-and-aft direction of the ship. However, 
the winches 7, 8 might also be arranged at other places and in other ways 
without departing from the idea of the invention. When the winches are 
arranged amidships and the line supports 16, 17 at the stern of the ship, 
however, it is ensured that there is a great spacing between these parts, 
which provides a larger area in which the tensioning may take place. 
The line pull winches 7, 8 night also consist of just one drum, which 
results in a simpler structure. However, a greater pulling force may be 
obtained by using several drums in each winch. Further, when several drums 
are used, one may be employed for initial winding-up of the line, and the 
other drum may then be activated just at the final tensioning where the 
force requirement is particularly great, frequently above 500 tons. 
In the embodiment described in which the line pull winches 7, 8 are placed 
amidships, already existing ships may be used. Thus, it is not necessary 
to use specially built anchor handling ships or large crane vessels. 
The ship moreover comprises gripper arms 29 which we arranged immediately 
in front of the hydraulically activatable locking parts 19, 20. The 
gripper arms are used for securing the lines 4, 5 during tensioning, as 
tensioning takes place in several steps. 
As shown in FIGS. 1 and 2, a block 28 may be mounted at the end of the line 
to which a pull is applied, through which block an auxiliary line is 
passed. One end of the auxiliary line is fixed, and its other end is run 
to the line pull winch with a view to obtaining a 1:2 change in force 
between the winch and the line to which a pull is to be applied. 
Finally, the ship 1 comprises a means 23 for measuring force, which may be 
adapted to perform a controlled measurement of the line load. Said means 
may be constructed as a strain gauge which is mounted on one or more of 
the lines, as shown in FIG. 2, but may e.g. also be incorporated in the 
line pull winches so that the load on the winches is recorded. 
When the ship 1 of the invention is used, a pull line 4 is extended between 
the ship 1 and the object to which a pull is to be applied. Further a 
holding line anchorage 6 is laid out in the desired tensioning direction 
from the object, and a holding line 5 is fixed between this anchorage 6 
and the ship. Then, at least one line is wound up by means of the line 
pull winch 7, 8 of the ship 1. Depending on i.e. the required pull, one or 
more winches and one or more drums may be used. During tensioning, the 
lines 4, 5 are guided into the ship 1, as shown in FIG. 1 and explained 
above. The gripper arms 29 are used for securing the lines 4, 5 in 
connection with change of block 28 and drum 8, 9, 21, 22. 
The present invention also concerns a method of applying a pull force from 
a ship 1 of the invention to a pull line 4 extended between the ship 1 and 
an object to which a pull is to be applied. The method comprises laying 
out a holding line anchorage 6 in the desired tensioning direction from 
the object, and a holding line 5 extends from the anchorage 6 back to the 
ship 1. The pull line 4 and/or the holding line 5 is hauled in from the 
ship 1, while retaining the other of the lines, thereby applying a pull to 
the pull line 4. 
The invention also concerns uses of the ship 1 of the invention. 
Thus, the ship 1 of the invention may be used for testing the tensile 
strength of anchorages for lines to moor vessels or offshore structures in 
the open sea. In this context, offshore structures are taken to include 
structures such a drilling platforms, floating production vessels, and 
loading buoy systems, and frequently the anchoring takes place at a water 
depth of up to 800-1200 meters. 
The invention also concerns a use or the ship 1 of the invention for 
applying a pull to grounded ships during salvage of these. It is hereby 
made possible to pull a grounded ship off the ground using fewer ships 
than is normally the case, as a particularly great pulling force may be 
provided using the ship 1 of the invention. Thus, today more ships are 
used for pulling grounded ships off the ground, as they just use their 
engine power for pulling and do not hold any holding anchoring means. 
Finally, the invention also concerns a use of a ship 1 for applying a pull 
to vessels during towing of these. 
Thus, it is shown in FIG. 3 how two ships 1 may be used for generating 
tensile stresses in a pull line 4. The ships 1 are connected to each other 
by means of two auxiliary lines 31, 32 so that both ships 1 are connected 
to the pull line 4 as well as the holding line 5. This provides a doubled 
tensile stress. 
Many modifications may be made without departing from the idea of the 
invention. For example, the line entry opening may be provided as a 
cut-out in the hull of the ship or may e.g. be shaped as a well.