[0001] The present disclosure relates generally to propellers fitted Self-Elevating Work Platform (SEWOP). Embodiments of the disclosure are related to SEWOP having propellers with rudders and azimuth thrusters that provides power and robust feature of propellers as well as flexible and agile features of the azimuth thrusters, for maximizing the control of power at the time of positioning SEWOP near offshore installation.

BACKGROUND

[0002] The Self-Elevating Work Platform (SEWOP) is a self-propelled barge equipped with system for jacking the barge out of and in water as per the requirement. SEWOPs are extensively used in the oil and gas industry. The SEWOP has unique feature of self-propelling and self-elevating, such that the SEWOP can be moved to the offshore installation and can be elevated to the required height, for performing various offshore installation works. The SEWOP or lift boat mainly has a hull, one or more tubular or lattice legs, cranes and propulsion system. The propulsion system has azimuth thruster. Some design use tunnel thruster in the bow for controlling the direction.

[0003] FIGS. 1 and 2 illustrate a type of lift boat 100 with a machinery deck or hull 101 and tubular legs 104 and FIGS. 3 and 4 illustrate another type of lift boat 100 with a hull 101 and lattice legs 115. The propulsion system essentially consists of electric motor driven azimuth thrusters 102 and a tunnel thruster 105. The tunnel thruster 105 is utilized for maneuvering the lift boat 100. The electric power to the motors of propulsion system is supplied from the main power circuit of lift boat 100. In FIGS. 1 and 2, the azimuth thrusters 102 are positioned below a helideck structure 111 of the lift boat 100, such that lift boat 100 moves forward along with tunnel thruster 105 which is positioned on the open deck side. As shown in FIGS. 3 and 4, the tunnel thruster 105 is positioned below the helideck structure 111 of the lift boat 100, such that lift boat 100 moves towards the installation platform along with azimuth thrusters 102 which are positioned below the open deck side.

[0004] The hull 101 or the platform structure has the helideck structure 111 on which a helicopter 109 can be operated. The accommodation block 108 is the space available for the operational personnel and does not include machineries and equipment area. The barge captain can operate the propulsion system from the wheel house or control room 106 {shown in FIG. 1). The hull 101 has rescue lifeboats 110 which are used to rescue crewmen and passengers, in case of emergency. The lift boat 100 has an engine driven electric power generator 107 (shown in FIG. 1 ) for operating the various machineries in the hull 101 , such as for powering hydraulic power units of cranes 103. The leg wells 112, fluid storage tanks 113 and auxiliary machines 114 of lift boat 100 are shown in FIGS. 2 and 4.

[0005] FIGS. 5A-5B and FIGS. 6A-6B illustrate electric motor driven tunnel and azimuth thrusters 105 and 102 utilized in FIGS. 1-4 of the lift boat 100 respectively. The electric motor 118 receives power supply from the engine driven electric power generator 107 depicted in FIG. 1. A thruster drive system 119 having a gear box transmits the rotational energy of the electric motor 118 to thruster blade 116, such that the tunnel thrusters 102 and/or the azimuth thruster 105 provides required trust to propel the lift boat 101 to the offshore installation, based on the steering of the lift boat 100 by the barge captain. The steering system 120 of azimuth thruster 102 is shown in FIG. 6.

[0006] Thus, in lift boat 100 of FIGS. 1-2, the azimuth thrusters 102 are positioned below the helideck structure 111, such that lift boat 100 moves forward with tunnel thruster 105 which is positioned on the open deck side and in lift boat 100 of FIGS. 3- 4, tunnel thruster 105 is positioned below the helideck structure 111, such that lift boat 100 moves towards the installation platform with azimuth thrusters 102 which are positioned below the open deck side. Other SEWOP designs use propellers which are small units and do not have stern thruster. Generally, lift boat is fitted with a dynamic positioning system which takes a reference from the satellite enabled global positioning software, to accurately position the lift boat near the offshore installation.

[0007] The ability to maneuver near the offshore installation is poor in above discussed propulsion systems (in FIGS. 1-4). Other methods of positioning of SEWOP near offshore installation use mooring winches, which are time consuming and labor intensive. Moreover, mooring for bigger SEWOP is difficult. The azimuth thrusters with tunnel thruster are improvements over the propellers and helps in positioning, only when the azimuth is pushing the SEWOP. If the SEWOP is needed to be pulled near the installation platform, azimuth thrusters lose the power due to Kort Nozzle. The stern tunnel thruster also assists in maneuvering only and does not provide any additional pull or push for the SEWOP, at the time of positioning the SEWOP near the offshore installation platform.

[0008] Thus, with existing propulsion systems, while SEWOP is approaching an offshore installation, it is critical to control its movement to avoid collision. Hence during positioning of SEWOP there is high demand of accurate performance on the propulsion system to enable correct location of the SEWOP.

[0009] A need, therefore, exists for an improved propeller fitted self-elevating work platform that overcomes the above drawbacks.

SUMMARY

[0010] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiment and is not intended to be a full description. A full appreciation of the various aspects of the embodiments disclosed herein can be gained by taking into consideration the entire specification, claims, drawings, and abstract as a whole.

[0011] It is, therefore, one aim of the disclosed embodiments to provide for a propeller fitted Self-Elevating Work Platform (SEWOP) comprising a propulsion system having at least one propeller each directly coupled to an individual engine through a gearbox, at least one rudder provided behind at least one propeller to control the direction of the SEWOP and at least one azimuth thruster provided at stem to control the maneuvering at the time of positioning and to provide additional thrust if required. The propeller and rudder are positioned at aft of the hull.

[0012] It is therefore, one another aim of the disclosed embodiments to provide for a propeller fitted SEWOP wherein the azimuth thruster comprises steering gear for providing the required thrust in any direction to keep the SEWOP in position.

[0013] It is, therefore, one another aim of the disclosed embodiments to provide for a propeller fitted SEWOP wherein the propellers thrust is guided by the rudders at the time of positioning the SEWOP near the offshore installation.

[0014] It is, therefore, one another aim of the disclosed embodiments to provide for a propeller fitted SEWOP in which the azimuth thruster is driven by an electrical motor with variable frequency drive.

[0015] It is therefore one another aim of the disclosed embodiments to provide for a propeller fitted SEWOP wherein the propeller with rudder is driven by a diesel engine.

[0016] It is, therefore, yet another aim of the disclosed embodiments to provide for a propeller fitted SEWOP in which the azimuth thruster and its steering gear are driven by a hydraulic or electric motor and the rudder of propeller is controlled by hydraulic or electric motor drive.

[0017] It is, therefore, yet another aim of the disclosed embodiments to provide for a propeller fitted SEWOP in comprising more than one azimuth thruster and more than one rudder, wherein all the azimuth thrusters work in sync and all the rudders work in sync, to position the SEWOP near the installation site.

[0018] It is, therefore, yet another aim of the disclosed embodiments to provide for a propeller fitted SEWOP having a retractable azimuth thruster, to protect the thruster when it is not in operation.

[0019] It is, therefore, one another aim of the disclosed embodiments to provide for a propeller fitted SEWOP in which the propeller and the azimuth thrusters are used together for population in case of emergency, when the SEWOP needs to be quickly moved away from the installation unit.

[0020] It is, therefore, one another aim of the disclosed embodiments to provide for a propeller fitted SEWOP in which the gearbox and the electric motor are first mounted from the top of the thruster well and then azimuth thruster is mounted from the bottom.

[0021] A method for positioning a propeller fitted self-elevating work platform, comprising:

[0022] providing thrust by operating the propeller positioned at aft of a SEWOP, while SEWOP is moving in an open water, wherein a rudder is behind the propeller and said rudder is driven by an individual engine through a gearbox; providing thrust by operating the propeller and the rudder to slowly move the SEWOP towards installation site; and providing thrust by operating azimuth thruster at stern with at least one steering gear to rotate the SEWOP to desired angle, to assist in maintaining position of the platform during installation.

[0023] It is, therefore, one another aim of the disclosed embodiments to provide for a method of positioning a propeller fitted SEWOP comprising, wherein SEWOP comprises more than one thruster and more than one rudders and operating all the rudders at aft in sync and operating all the azimuth thrusters in sync, such that while positioning the SEWOP, the thrust of the propellers is guided by the rudders and the thrust of the azimuth thrusters is guided by the steering gears.

[0024] It is, therefore, one another aim of the disclosed embodiments to provide for a method of positioning a propeller fitted SEWOP wherein the azimuth thruster is powered by at least one hydraulic motor or electric motor with a variable frequency drive.

[0025] It is, therefore, one another aim of the disclosed embodiments to provide for a method of positioning a propeller fitted SEWOP wherein the steering gear of azimuth thruster is driven by at least one hydraulic motor or electric motor.

[0026] It is, therefore, one another aim of the disclosed embodiments to provide for a method of positioning a propeller fitted SEWOP, wherein the rudder of the propeller is controlled by at least one electric motor drive or hydraulic motor drive.

[0027] It is, therefore, yet another aim of the disclosed embodiments to provide for a combination of propeller and thruster that brings in the power and robust feature of propellers as well as flexible and agile features of the azimuth, thus maximizing the control of power during positioning of the SEWOP, which is the most crucial part of operation on SEWOP.

[0028] Other aspects and advantages of the invention will become apparent from the following detail description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.

[0030] FIG. 1 is an illustration of a side view of a prior art lift boat showing a hull and tubular legs;

[0031] FIG. 2 is an illustration of a top view of the lift boat depicted in FIG. 1, showing the thrusters in a machinery deck;

[0032] FIG. 3 is an illustration of a side view of a prior art lift boat showing a hull and lattice legs;

[0033] FIG. 4 is an illustration of a top view of the lift boat depicted in FIG. 3, showing the thrusters in a machinery deck;

[0034] FIGS. 5A and 5B is an illustration of side views of an electrical motor driven tunnel thruster depicted in FIGS. 1-4;

[0035] FIGS. 6A and 6B is an illustration of side and top views of an electrical motor driven azimuth thruster depicted in FIGS. 1-4; [0036] FIG. 7 is an illustration of a side view of a lift boat showing a hull, lattice legs, a propeller and tunnel thruster, in accordance with disclosed embodiments;

[0037] FIG. 8 is an illustration of a side view of a direct engine driven propeller with a rudder for propulsion of the lift boat depicted in FIG. 7, in accordance with disclosed embodiments; and

[0038] FIG. 9 is an illustration of a top view of a direct engine driven propeller depicted in FIG. 8, in accordance with disclosed embodiments.

[0039] Fig. 10 is an illustration showing the thruster assembly indicating the position of thruster well.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0040] The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.

[0041] Disclosed embodiments provide a propulsion system having a combination of propellers with rudders and thruster that brings in the power and robust feature of propellers as well as flexible and agile features of the azimuth. The propulsion system maximizes the control of power during positioning of the SEWOP near offshore installation, which is the most crucial phase of operation on SEWOP.

[0042] Referring to FIG. 7, a side view of a lift boat 300 having a hull 301, lattice legs 304, pedestal cranes 303 and propulsion system is disclosed. The propulsion system has at least one propeller 305 and rudder (not shown) positioned at aft of the hull 301 and at least one azimuth thruster 302 positioned at stern of the hull 301. The propeller 305 with rudder and azimuth thruster 302 is utilized to position the lift boat 300 near the offshore installation site. After positioning, the hull 301 can be elevated above the sea level and the lattice legs 304 can be drilled and deployed in the seabed for supporting the SEWOP 100. One end of a cantilever 309 is attached to open deck side of the hull 301 and the other end of the cantilever 309 holds a Work Over Unit (WOU) 308, above the seabed for performing work over operations, such as cleaning oil & gas wells. Once the SEWOP is supported, the machineries and equipment in the lift boat 300 can be utilized for installing an offshore structure such as well head platform, a wind mill, etc.

[0043] The cranes of pedestal type or Leg Encircling Cranes (LECs) type can be utilized during installation, such as for material handling from SEWOP to the installation structure. FIG. 7 shows a pedestal crane 303 utilized for handling materials at the time of installation or construction of a platform at offshore. The hull

301 or the platform structure has a helideck structure 307 on which a helicopter can be operated to assist in installation process. The accommodation block 306 is the space available for the operational personnel and does not include machineries and equipment area. The barge captain can operate the propulsion system from the wheel house or control room. The hull 101 has rescue lifeboats 310 which are used to rescue crewmen and passengers in case of emergency. The lift boat 300 has an engine driven electric power generator for operating the various machineries in the hull 301, such as for powering hydraulic power units of cranes 303, driving propulsion system, etc.

[0044] The propeller 305 has a rudder (shown in FIGS. 8 and 9) provided at its back to control the direction of the lift boat 300. Each propeller 305 is driven by directly coupling to an individual diesel engine (shown in FIGS. 8 and 9). The azimuth thruster 302 is electrical motor driven with a variable frequency drive. The azimuth thruster 302 has steering gear (shown in FIGS. 8 and 9) for providing the thrust in any required direction and hence helps to keep the lift boat 300 in position. The azimuth thrusters 302 are provided in the front of the hull 301 to control the maneuvering during positioning or to provide additional thrust if required. The electric power to the motors is supplied from main power circuit of the lift boat 300. As shown in FIG. 7, the propeller 305 is positioned below the helideck structure 307 of the lift boat 300, such that lift boat 300 moves forward with azimuth thrusters 302 which are positioned on the open deck side. The azimuth thruster 302 is of retractable type, to protect the thruster when it is not in operation.

[0045] It should be noted that the propellers and rudders corresponds to ship design and can be installed and maintained as per prevalent marine practice. The azimuth thruster is bottom mounted, such that the thruster is split in two parts. The gearbox and motor contributing to upper part (401) of thruster assembly is first mounted from the top of the thruster well, and then the lower part (402) of thruster assembly is fitted from the bottom of the thruster well (403) as shown in Fig 10.

[0046] While lift boat 300 is moving in open waters, the propulsion is by the propeller 305 which is driven by individual diesel engine. While near an offshore installation, the SEWOP or lift boat 300 needs to be positioned and hence the propeller 305 and the rudder are used to slowly move towards the installation. Further, the stern azimuth thruster 302 driven by electric motor can rotate three hundred and sixty degrees to assist in maintaining the position. The azimuth thruster due to its steering gear can provide thrust in any required direction and also assist in keeping the lift boat 300 in position. At the time of positioning, wherein more than one azimuth thruster and more than one rudder is present, all the azimuth thrusters 302 work in sync and all the rudders at the AFT in sync, such that the thrust of the propeller 305 is guided by the rudders and the thrust of the azimuth thruster 302 is guided by the steering gear of the azimuth thruster.

[0047] The unique combination of propeller 305 and azimuth thruster 302 brings in the power and robust feature of propeller 305 as well as flexible and agile features of the azimuth thruster 302, thus maximizes the control of power during positioning of the lift boat 300, which is the most crucial phase of the operation on lift boat 300.

[0048] FIG. 8 and FIG. 9 illustrate side and top views of a direct engine driven propeller 305 with a rudder 321 for propulsion of the lift boat 300 depicted in FIG. 7 respectively. The propeller 305 is positioned at aft of the hull 301 and is powered by directly connecting to a diesel engine 319 through a shaft drive 318 including a gearbox. A long shaft known as a propeller shaft 314 is used for connecting the diesel engine 319 and the propeller 305. A stern tube 315 forms a narrow hole in the hull 301 at the rear end (aft peak) of the lift boat 300, through which the propeller shaft 314 passes and connects the engine 319 and propeller 305. Plummer block 316 connects the propeller shaft 314 and a shaft extension 317 which is positioned at the engine side. A coupling 320, couples the shaft drive 318 and the shaft extension 317, such that the rotational energy from the shaft drive 318 is transferred to the shaft extension 317, to drive the propeller blade 312. As shown in FIG. 8, the propeller 305 is positioned below a bulkhead 325 which is positioned at the end of the hull 301.

[0049] A rudder 321 is provided behind the propeller 305 to control the direction of the lift boat 300. The rudder 321 operates by redirecting the fluid that past the hull 301, thus imparting a turning or yawing motion to the lift boat 300. The rudder 321 can be a flat plane or sheet of material attached with hinges to the lift boat 300. Normally, the rudder 321 is connected to a steering system 323 through a rudder shaft 324. The steering system 323 is positioned in the wheel house or control room of the lift boat 300, such that the barge captain can operate the steering system 323 to control the direction of the lift boat 300. A bearing 322 is a rotating support placed between the rudder shaft 324 and the rudder 321, in order to allow them to move easily in the water, at the time of operating the steering system 323. A keel 311, one of the main longitudinal beams (or plates) of the hull 301 of the lift boat 300 is shown in FIG. 8. [0050] The propeller blade 312 is connected to the propeller shaft 314 and the shaft extension 317 extends from the shaft drive 318 through the coupling 320, as shown in FIGS. 8-9. Rummer block 316 couples the propeller shaft 314 and the shaft extension 317. Y-bracket 313 can be utilized to support the propeller 305 under the operational load and can withstand maximum output of the engine 319.

[0051] It should be noted that the lift boat consist of at least one propeller driven with individual diesel engine and at least one azimuth thruster at stem which are driven by electric motor. Any possible combinations in number of propellers rudders and azimuth thrusters are possible for positioning the SEWOP near offshore installation. It should also be noted that the azimuth thruster can be also be driven by hydraulic motor and the steering gear can also be driven by hydraulic motor without any limitation. Also, the rudder for the propellers can be rotated by electric motor or by hydraulic system.

[0052] While SEWOP or lift boat is moving in open waters, the propulsion is by all the propellers. While near an offshore installation, the SEWOP needs to be positioned and hence all propellers and the rudders are used to slowly move towards the installation. Further the all stern azimuth thrusters assist in maintaining the position. In case of emergency if the vessel needs to quickly move away from the unit, ail the propellers and all the azimuth thrusters are used together to increase the thrust of the lift boat.

[0053] Thus from the above description it is very apparent that a unique combination of propeller with rudder and azimuth thruster with steering gear brings in the power and robust feature of propellers as well as flexible and agile features of the azimuth, thus maximizes the control of power during positioning of the vessel.

[0054] It will be appreciated that variations of the above disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

[0055] Although embodiments of the current disclosure have been described comprehensively, in considerable detail to cover the possible aspects, those skilled in the art would recognize that other versions of the disclosure are also possible.