System and method for determining torque

Abstract

A system for determining torque remotely offshore is disclosed. The system comprises a support (710), a motor (730), and a shaft (740) connected to the motor (730) at one end of the shaft (740) and for driving a tool for operating remote offshore equipment. The system comprises a first encoder (810) and a second encoder (820), both configured to detect twist of the shaft (740), each being arranged between the support (710) and the shaft (740), the first encoder (810) being arranged close to the motor (730) and the second encoder (820) being arranged at a distal end of the shaft (740) thereby detecting twist of the shaft (740); and a housing (830) comprising electronics (840) for both the first encoder (810) and the second encoder (820), the housing (830) being sealed off to maintain 101 kPa, 1 atm, for the electronics (840), the electronics (840) comprising a processor (850) configured to determine the torque based on the detected twist. A subsea system and method using the same are also disclosed.

Description

[0001] SYSTEM AND METHOD FOR DETERMINING TORQUE

[0002] Technical Field

[0003] The present disclosure relates generally to the field of measuring torque at a remote location offshore, for example subsea. More specifically, the present invention relates to a system for determining torque remotely offshore, where the system may comprise a robotic arm. The present invention also relates to a subsea system with such a system and a method for remotely operating subsea equipment with at least two different torque values with a tool with such a system.

[0004] Background

[0005] There is a need to operate equipment offshore. This is done with a robotic arm to support operations on subsea devices. The robotic arms can be used with subsea devices such as manifolds, trees, pumps, and blowout preventers. Robotic arms for manipulating devices subsea are know from EP3165709B1 and EP3296505B1. The equipment require different torques when operated. For example, a small valve needs requires less torque to be operated compared with a larger valve. These two operations require two different tools and therefore also calibration with each tool change. It is a problem to measure torque at a remote location, offshore, where frequent calibrations are not possible or practical. Different operations require different tools and consequently a tool change. Each tool change requires a calibration to ensure that the equipment is operated with the correct torque. Different operations with the same tool may require a calibration. It is desirable to eliminate the requirement to calibrate but at the same time be able to use different tools.

[0006] A further problem is moving the tool and the robotic arm through the splash zone when installing or uninstalling the robotic arm subsea. The waves, water, wind, etc. tend catch the tool and to separate and open up the robotic links when moved through the splash zone. This may result in damage to the tool and the robotic arm, failure to properly install the robotic arm, or even loss of the robotic arm. The accuracy of a torque tool may be affected. This may cause for a need to calibrate anew.

[0007] It is desirable to provide a system that avoids calibration, can be used remotely, addresses these problems, is inexpensive to manufacture, is easy to manufacture and assemble, and is robust and reliable. The tool and the robotic arm should be easy to move through the splash zone and also be able to provide a good and reliable operation of different well equipment. The present disclosure is directed to overcoming one or more of the problems as set forth above.

[0008] SUMMARY

[0009] It is an objective of the present invention to provide a system for determining torque remotely offshore, a subsea system comprising such a system, and a method for remotely operating subsea equipment with at least two different torque values with a tool with such a system. This objective can be achieved by the features as defined by the independent claims. Further enhancements are characterized by the dependent claims. The invention is defined by the claims.

[0010] According to one embodiment, a system for determining torque remotely offshore is disclosed. The system comprising a support 710, a motor 730, and a shaft 740 connected to the motor 730 at one end of the shaft 740 and for driving a tool for operating remote offshore equipment. The system comprises a first encoder 810, a second encoder 820, and a housing 830. The first encoder 810 and the second encoder 820 are both configured to detect twist of the shaft 740, each being arranged between the support 710 and the shaft 740. The first encoder 810 is arranged close to the motor 730 and the second encoder 820 is arranged at a distal end of the shaft 740 thereby detecting twist of the shaft 740. The housing 830 comprises electronics 840 for both the first encoder 810 and the second encoder 820. The housing 830 is sealed off to maintain 101 kPa, 1 atm, for the electronics 840, the electronics 840 comprising a processor 850 configured to determine the torque based on the detected twist. When using one or more tools for different operations subsea the system determines accurate torque without the need to calibrate.

[0011] The system may further comprise a robotic arm with an end effector 400. The end effector 400 may comprise the support 710, the motor 730, the shaft 740, the first encoder 810, the second encoder 820, the housing 830, and the electronics 840. The robotic arm 630 may comprise a base 100, a first arm 200, and a second arm 300. The first arm 200 may comprise a first end 210 rotatably connected to the base 100 for rotation around a first rotational degree of freedom R1, and a second end 220 opposite the first end 210. The second arm 300 may comprise a third end 310 rotatably connected to the second end 220 for rotation around a second rotational degree of freedom R2 parallel to the first rotational degree of freedom R1, and a fourth end 320 opposite the third end 310 of the second arm 300. The end effector 400 may be connected to the fourth end 320 for rotation around a third rotational degree of freedom R3 being parallel to the second rotational degree of freedom R2. The robotic arm may be removably attached subsea. For example, a subsea system may comprise an interface position 640 for remote installation of the robotic arm 630.

[0012] The first arm 200 and the second arm 300 may be configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm. The second arm 300 and the end effector 400 may be configured to have complimentary shapes to allow at least a major part of the end effector 400 to fold in to the second arm 300 such that when they are folded together at least a major part of the end effector 400 is positioned within the outer boundary of the second arm 300.

[0013] The end effector 400 may comprise a flexible element 410 allowing the end effector 400 to rotate around a fifth rotational degree of freedom R5 perpendicular to the third rotational degree of freedom R3. The base 100 may comprise one or more attachment means 130 for lifting the robotic arm. The robotic arm may be configured to have a mass centre lying on a vertical plane going through two attachment means 130, when the first arm 200, the second arm 300, and the end effector 400 are folded together.

[0014] The shaft 740 is at least partially shaped as a hollow cylinder. A part between the encoders may be a hollow cylinder.

[0015] The system may further comprise a redundant housing 832 comprising redundant electronics 842 and a redundant processor 852, corresponding to the housing 830 with its electronics 840 and processor 850. Alternatively, or in combination the processor 850 may be configured to store data comprising the determined torque value. The processor 850 may be a controller and may store the data in a data storage part of the electronics.

[0016] According to one embodiment, a subsea system may comprise the system according to any one of embodiments described herein. The subsea system may further comprise a subsea installation 600 comprising at least two pieces of subsea equipment 610, 620 to be operated by the robotic arm 630 and an interface position 640 for remote installation of the robotic arm 630.

[0017] According to one embodiment, a method is disclosed for remotely operating subsea equipment 770 with at least two different torque values with a tool 760 with the system as described herein. The method comprises engaging 910 a piece of subsea equipment 770 with the tool 760; and operating 920 the subsea equipment 770 with the tool 760 to a predetermined torque while receiving feedback from the processor 850 of the torque based on the detected twist.

[0018] The method may further comprise operating 930 a subsequent subsea equipment 770 with the tool 760, or a different tool, uncalibrated to a different predetermined torque while receiving feedback from the processor 250 of the torque based on the detected twist. According to at least one embodiment, no calibration is necessary, and the operation may be done with initial factory calibration. There is thus no need for a further calibration when changing tool or operation on a different subsea equipment.

[0019] The method may further comprise collecting 940 data comprising the determined torque value from the processor 250 after the subsea equipment 770 has been operated with the tool 760 to the predetermined torque. The data may include the determined torque and an identification of the subsea equipment 770. This allows subsequent verification what subsea equipment has been operated to what torque value, for example what valve has been tightened with what torque.

[0020] The method may further comprise taking up 950 misalignment, with a flexible element 410, between a predetermined position and the actual position for the tool 760 for operating the subsea equipment 770. The method may further comprise folding 960 the end effector 100 into an arm of the robotic arm such that when they are folded together at least a major part of the end effector 100 is positioned within the outer boundary of the arm. The method may further comprise removably attaching the robotic arm subsea. The method may further comprise operating the system remotely, with the system being subsea. An operator may be on a vessel at sea or even onshore.

[0021] One or more embodiments disclosed herein allows the system to determine the torque remotely offshore, with no need for re-calibrating each time when changing tool or operating different subsea equipment. A robotic arm with the system may be moved to different remote locations, for example subsea, and use the same or different tools without the need to calibrate the tool each time.

[0022] At least one of the above embodiments provides one or more solutions to the problems and disadvantages with the background art. Other technical advantages of the present disclosure will be readily apparent to one skilled in the art from the following description and claims. Various embodiments of the present application obtain only a subset of the advantages set forth. No one advantage is critical to the embodiments. Any claimed embodiment may be technically combined with any other claimed embodiment or embodiments.

[0023] Brief Description of the Drawings

[0024] The disclosure will be further described with reference to examples depicted in the accompanying figures in which:

[0025] FIG 1 is a schematic illustration of a robotic arm and a base according to one embodiment;

[0026] FIG 2 is a schematic illustration of a cut through view of a part of an effector with the system according to an embodiment;

[0027] FIG 3 is a schematic illustration of a view from above of a subsea installation with the robotic arm and subsea equipment according to an embodiment; and

[0028] FIG 4 is a schematic illustration of a method according to an embodiment.

[0029] Detailed Description

[0030] Embodiments of the present invention provide a system for determining torque remotely offshore, a robotic arm with such a system, a subsea installation with such a system, and a method for remotely operating subsea equipment with at least two different torque values with a tool with such a system. This detailed description describes in detail at least one way of carrying out the claimed invention by referring to the drawings. Various embodiments are illustrated in the figures. Figure 1 illustrates the unfolded robotic arm with the end effector 400. Here a first arm 200, a second arm 300, and an end effector 400 are unfolded. Figure 2 shows a view of a part of the end effector. The view is a cut along the axis of the end effector 400. Figure 3 is a top view of a subsea installation 600 with the robotic arm 630 that can operate at least two pieces of subsea equipment 610, 620. Figure 4 illustrates the method for remotely operating subsea equipment with at least two different torque values with a tool with such a system.

[0031] Figure 2 illustrates a system for determining torque remotely offshore. The system comprises a support 710, a motor 730, and a shaft 740. The motor 730 may comprise a gear box between the motor and the shaft 740. The shaft 740 is connected to the motor 730 at one end of the shaft 740. The shaft 740 is configured for driving a tool for operating remote offshore equipment, for example subsea. The system comprises a first encoder 810, a second encoder 820, and a housing 830. The first encoder 810 and the second encoder 820 are both configured to detect twist of the shaft 740. Each encoder being arranged between the support 710 and the shaft 740, the first encoder 810 being arranged close to the motor 730 and the second encoder 820 being arranged at a distal end of the shaft 740 thereby detecting twist of the shaft 740. The housing 830 comprises electronics 840 for both the first encoder 810 and the second encoder 820. The housing 830 is being sealed off to maintain 101 kPa, 1 standard atmosphere, 1 atm, for the electronics 840. The electronics 840 comprises a processor 850 configured to determine the torque based on the detected twist. This may be the only means for determining the torque. The system may further comprise a body 750, for example the end effector housing, and the support 710 may be a part of, or connected to, the body 750.

[0032] As best illustrated in figure 2, when the motor 730 rotates the shaft 740 rotates. The shaft 740 is connected to the motor 730 at one end of the shaft 740. The shaft 740 may be directly connected to the motor 730 with no other means therebetween or with a gear box therebetween. The shaft 740 may have at the other end a tool holder for a tool 760 for operating subsea equipment 770. The shaft 740 may be at least partially shaped as a hollow cylinder. The hollow cylinder may have different diameters, for example one section of the hollow cylinder may have one diameter and another section of the hollow cylinder may have a smaller or larger diameter. The wall thickness of the shaft 740 as a hollow cylinder may also vary. For example, one section may have one thickness and another section may have a thicker or thinner thickness. In this way the hollow cylinder may be configured to twist a suitable amount when torque is applied and over a predetermined torque range. This arrangement give a compact and reliable end effector with the system.

[0033] Since the two encoders 810, 820 are each at one end of the shaft 740 they can detect the amount of twist that the shaft 740 twists when torque is applied. The distance between the two encoders 819, 820 is at least a major part of the shaft 740. Each encoder 810, 820 may comprise two parts, one part stationary on a housing 750, the other part on the shaft 740. Therefore, even if the housing 750 twists during an operation, only the relative amount of twist of the shaft 740 is measured by the two encoders 810, 802. By having two encoders 810, 820 no calibration is needed because any misalignment would be taken up by both encoders and cancel each other out. For example, the encoders may only consider the amount of twist when the motor 730 is in operation. The encoders may be digital sensors, contactless sensors, light sensors, magnetic sensors, rotary sensors, preferably contactless rotary sensors. According to one embodiment, the system may comprise a redundant housing 832. The redundant housing 832 may comprise redundant electronics 842 and a redundant processor 852. This corresponds to the housing 830 with its electronics 840 and processor 850. In case of a malfunction of the electronics 840 in the housing 830, the system may still operate by using the redundant electronics 842 in the redundant housing 832. According to one embodiment, the redundant electronics 842 and / or the redundant processor 852 may be in the housing 830.

[0034] According to one embodiment, the processor 850 may be configured to store data comprising the determined torque value. The data may be stored in a data storage part of the electronics 840. The data stored may be stored automatically and include torque data and identification of the subsea equipment. In this way a user may subsequent to an operation get data showing what torque was used for a certain operation. For example, a user may use the system for closing two different valves and opening a third valve, all three with a different tool and / or different torque requirement, or all three with the same tool. When all three operations have been done, then the user can retrieve all three stored toque amount data from the system. In this example there is no need to calibrate when changing between different tools. The valves may be in the range of half-inch to seven-inch valves with the same torque tool.

[0035] According to one embodiment, and best illustrated in figure 1 and 3, the system may further comprise a robotic arm 630. The robotic arm 630 may comprise an end effector 400. The end effector 400 may comprise the support 710, the motor 730, the shaft 740, the first encoder 810, the second encoder 820, the housing 830, and the electronics 840. The end effector 400 may further comprise a gear box, encoder for the motor, and / or motor electronics. The robotic arm 630 may comprise a base 100, a first arm 200, and a second arm 300. The first arm 200 may comprise a first end 210 rotatably connected to the base 100 for rotation around a first rotational degree of freedom R1 , and a second end 220 opposite the first end 210. The second arm 300 may comprise a third end 310 rotatably connected to the second end 220 for rotation around a second rotational degree of freedom R2 parallel to the first rotational degree of freedom R1, and a fourth end 320 opposite the third end 310 of the second arm 300. The end effector 400 may be connected to the fourth end 320 for rotation around a third rotational degree of freedom R3 being parallel to the second rotational degree of freedom R2. In this way, and as illustrated in figure 1, the robotic arm 630 can move the end effector 400 with at least three parallel degrees of freedom. The base 100 may comprise means 110 for rotating the base 100 around a fourth rotational degree of freedom R4 perpendicular to the first rotational degree of freedom R1. The means 110 may be a swivel. The means 110 may allow the first arm 200, the second arm 300, and the end effector 400 to be rotated perpendicular to the first, second, and third rotational degrees of freedom R1, R2, R3.

[0036] The end effector 400 may comprise a flexible element 410 allowing the end effector 400 to rotate around a fifth rotational degree of freedom R5 perpendicular to the third rotational degree of freedom R3. The fifth rotational degree of freedom R5 may also, or alternatively, be perpendicular to a sixth rotational degree of freedom R6. The flexible element 410 may, for example, be a torsion bar allowing the base to rotate, for example allowing 5-10 degrees flexibility, around the fifth rotational degree of freedom R5. The flexible element 410 may, for example, be a spring or a gimbal. This flexibility allows the end effector 400 to align with its working position. The fifth rotational degree of freedom R5 may be passive, that is there may not be any drive means for rotation around the fifth rotational degree of freedom R5, instead the flexible element 410 may allow the robotic arm to be flexible. The flexibility may be plus / minus 5 to 10 degrees. As an alternative, or addition, hereto, the base 100 may comprise a flexible element allowing the base 100 to rotate around a further rotational degree of freedom perpendicular to the first rotational degree of freedom R1. The fifth rotational degree of freedom R5 may also be perpendicular to the fourth rotational degree of freedom R4.

[0037] The end effector 400 may further comprise rotational means 450 for rotating an end of the end effector, or a tool attached to the end effector, around a sixth rotational degree of freedom R6 being perpendicular to the third rotational degree of freedom R3. The end effector 400 may further comprise additional rotational means for rotating the end around a further rotational degree of freedom being perpendicular to the sixth rotational degree of freedom R6 and the third rotational degree of freedom R3.

[0038] The first arm 200 and the second arm 300 may be configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm. For example, the second arm 300 may fold into the first arm 100, for example by the second arm 300 rotating around the second rotational degree of freedom R2. At least a major part of one of the arms is to be understood to be at least half the arm. Preferably at least three quarters, and preferably substantially all of the arm is positioned within the outer boundary of the other arm. For example, when the second arm 300 is aligned with the first arm 200, they are adjusted in a straight line with each other, the second arm 300 may be inside the other arm. The second arm 300 may be folded into the first arm 200 such that the second arm 300 is protected by the first arm 200, for example when stored or transported through the splash zone.

[0039] The robotic arm 630 may be removably attached subsea. The base 100 may be suitable for being installed subsea to a subsea installation 600, for example a manifold, a tree, a blowout preventer, a pump, or any other equipment subsea. This is best illustrated in figure 3. The base may be installed subsea at an interface position 640 on a subsea installation 600. In figure 3 the interface position 640 has been indicated by a dashed circle, because it may not be visible underneath the base 100 of the robotic arm 630. The end effector 400 has also been indicated by a dashed circle in figure 3. The end effector 400 may comprise the support 710, the motor 730, the shaft 740, the first encoder 810, the second encoder 820, the housing 830, and the electronics 840. The robotic arm 630 may be attachable to, and removable from, the subsea installation 600. A subsea system may comprise any embodiment of the system described herein. The subsea system may further comprise the subsea installation 600 comprising at least two pieces of subsea equipment 610, 620 to be operated by the robotic arm 630 and the interface position 640 for remote installation of the robotic arm 630. The robotic arm 630 may allow to perform operations such as, for example, opening / closing a valve, making a connection, switching a lever, etc. The base 100 may comprise an elongate part that can be placed in an opening, for example a funnel, of the subsea equipment. In this way the base 100 with the robotic arm may be installed on, for example, a manifold. The base 100 may provide a fourth rotational degree of freedom R4. The fourth rotational degree of freedom R4 may be along an axis of the elongate part as illustrated in figure 1 and may be perpendicular to the first rotational degree of freedom R1. The first arm 200 may be the first link in the robotic arm and may be connected to the base 100 for rotation around the first rotational degree of freedom R1. The first arm 200 may be attached for rotation at an outer side, the periphery, of the base 100, for the purpose of extending the reach of the robotic arm. The first arm 200, the second arm 300, and the end effector 400 may form the robotic arm as three links, like three chain links, with the first, second, and third rotational degrees of freedom R1, R2, and R3 being all parallel to each other and perpendicular to the fourth rotational degree of freedom R4. The second arm 300 may be arranged between the first arm 200 and the end effector 400. The end effector 400 may be the last link of the robotic arm. The arms 200, 300 may be straight arms. The end effector 400 may carry a tool, such as for example a gripper or a torque tool.

[0040] Embodiments described herein may allow the robotic arm 630 to work on two or more pieces of subsea equipment 610, 620. Operations such as, for example, opening / closing a valve, making a connection, and / or switching a lever may be performed. A subsea installation 600 may comprise an interface position 640 and a tool changing means 650. The robotic arm 630 may be placed in the interface position 640 and thereby be in a position to reach two or more pieces of subsea equipment 610, 620, and the tool changing means 650. A tool held by the end effector 400 may be used for operating on two or more pieces of subsea equipment 610, 620. At least one embodiment described herein allows to use different tools at two different pieces of subsea equipment 610, 620 without the need for calibrating to get a correct torque reading. At least one embodiment described herein allows to use the same tool at two different pieces of subsea equipment 610, 620 without the need for calibrating to get a correct torque reading. At least one embodiment described herein allows to use different tools at any piece of subsea equipment 610, 620 without the need for calibrating to get a correct torque reading. At least one embodiment described herein provides for a change of tool without the need to calibrate for the new tool. As best illustrated in figure 3, the robotic arm 630 with the system may operate on a first piece of subsea equipment 610 with a first tool. Thereafter the robotic arm 630 may change the first tool to a second tool at the tool changing means 650. Subsequently, and without the need to calibrate, the robotic arm 630 with the system may operate on a second piece of subsea equipment 620 with the second tool. The robotic arm 630 with the system may operate on the first piece of subsea equipment 610 with the second tool, also without the need to calibrate.

[0041] A method is disclosed for remotely operating subsea equipment 770 with at least two different torque values with a tool 760 with the system according to any one of the embodiments disclosed herein. The method is schematically illustrated in figure 4, but reference is also made to the figures 1 to 3. The method comprises engaging 910 a piece of subsea equipment 770 with the tool 760; and operating 920 the subsea equipment 770 with the tool 760 to a predetermined torque while receiving feedback from the processor 850 of the torque based on the detected twist. The method may be for remotely operating subsea equipment 770 with at least two different torque values with a different tool 760 each with the system according to any one of the embodiments disclosed herein. No calibration of the tool with regard to torque is required when using at least one embodiment disclosed herein. The subsea equipment 770 may be the two or more pieces of subsea equipment 610, 620.

[0042] The method may further comprise operating 930 a subsequent subsea equipment 770 with the tool 760, or a different tool, uncalibrated to a different predetermined torque while receiving feedback from the processor 250 of the torque based on the detected twist. As also disclosed above with reference to figure 3, when changing to a different tool or changing to operate to a different piece of subsea equipment, this may be done with no calibration, thus with un-calibrated tools. No calibration is necessary when changing tool and one may rely on the initial calibration made when the system was built, and this allows to make tool changes using uncalibrated tools. Calibration as mentioned herein may refer to calibrating the end effector, and / or the system, with regard to torque, for example rectifying the end effector, and / or the system, such that a correct amount of torque is measured.

[0043] The method may further comprise collecting 940 data comprising the determined torque value from the processor 250 after the subsea equipment 770 has been operated with the tool 760 to the predetermined torque. This allows a user to be able in real time, or at a later stage, to verify what subsea equipment 770 has been operated to what torque value, for example what valve 610, 620 has been tightened with what torque. Such verification and check can be done remotely. The data collection may include collecting identification data of the different pieces of subsea equipment.

[0044] The method may further comprise taking up 950 misalignment, with a flexible element 410, between a predetermined position and the actual position for the tool 760 for operating the subsea equipment 770. This allows a tool 760 to properly operate a piece of subsea equipment, even when the arms 200, 300 of the robotic arm 630 carrying the system are not flexible.

[0045] The method may further comprise folding 960 the end effector 100 into an arm of the robotic arm 630 such that when they are folded together at least a major part of the end effector 100 is positioned within the outer boundary of the arm. As disclosed above, this allows the robotic arm 630 with the end effector 400 and the system to be stored in a protected position and move through a splash zone without damage.

[0046] The method may further comprise removably attaching the robotic arm subsea. The base 100 may comprise one or more attachment means 130 for lifting the robotic arm. Preferably there may be two attachment means 130, one on each side of the base 100, preferably on the same sides as the one or more of the two first arm side supports 230, 232 and the two second arm side supports 330, 332. The attachment means may be, for example openings, means suitable for a gripper to connect to. The gripper may be configured for preventing the first arm 200, the second arm 300, and the end effector 400 to unfold when the gripper engages the one or more attachment means 130 for lifting the robotic arm, for example by the gripper being U-shaped. The gripper may be configured for holding, engaging, one or more of the first arm 200, the second arm 300, and the end effector 400 to keep the robotic arm folded together when the gripper is attached to the base 100. The gripper may be configured for engaging the first arm 200, with the second arm 300 and the end effector 400 substantially folded inside the first arm 200. The gripper may be configured for clamping the first arm 200, with the second arm 300 and the end effector 400 substantially folded inside the first arm 200, between the gripper and the base 100, thereby limiting, preventing, the first arm 200 to move, unfold, relative to the base 100 where the attachment means 130 are. This provides a simple yet effective way of handling the folded robotic arm with the gripper and ensuring that the robotic arm cannot unfold when, for example, being moved through the splash zone.

[0047] The robotic arm may be configured to have a mass centre lying on a vertical plane going through two attachment means 130, when the first arm 200, the second arm 300, and the end effector 400 are folded together, preferably folded together and lying on the base 100, as best illustrated in figure 4. The mass centre may be lying on a straight line between two attachment means 130. This improves the robotic arm’s possibility to be handled in a safe manner without tipping over and possibility to be transported through the splash zone. The mass centre is in this case very similar to the centre of gravity. The mass centres of the base 100, the first arm 200, the second arm 300, the end effector 400, when folded together onto the base 100 may be close to each other, and the combined mass centre hereof may be lying in a vertical plane that goes through the two attachment means 130. The plane may extend in the direction of the fourth rotational degree of freedom R4.

[0048] At least one embodiment described herein provides a torque control system using encoders. It permits to control all variation of torque range, for example from half-inch to seven-inch valves, using the same torque tool without the need to change it subsea. At least one embodiment address: high accuracy of torque applied since there is no need to consider motor current; reduces the risk of damaging subsea equipment, for example valves, due to the precise torque control; providing a standard solution to all different manifolds configurations; providing high accuracy on subsea equipment data, for example valve signature; and providing historical data of each subsea equipment and its position since the system can record and compare torque increase of each subsea equipment during their lifetime. Further advantages provided by at least one embodiment is no restriction on subsea equipment set / range application, due to variation of torque accuracy due to temperature and / or subsea pressure. The possibility and capability to operate the complete range of subsea equipment renders the system and method simple due to not having to calibrate or change the torque tool.

[0049] It will be apparent to those skilled in the art that various modifications and variations can be made to the system for determining torque remotely offshore, the subsea system with such a system, and the method for remotely operating subsea equipment with at least two different torque values with a tool with such a system. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and method. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

Claims1 A system for determining torque remotely offshore, the system comprising a support (710), a motor (730), and a shaft (740) connected to the motor (730) at one end of the shaft (740) and for driving a tool for operating remote offshore equipment, the system comprising a first encoder (810) and a second encoder (820), both configured to detect twist of the shaft (740), each being arranged between the support (710) and the shaft (740), the first encoder (810) being arranged close to the motor (730) and the second encoder (820) being arranged at a distal end of the shaft (740) thereby detecting twist of the shaft (740); and a housing (830) comprising electronics (840) for both the first encoder (810) and the second encoder (820), the housing (830) being sealed off to maintain 101 kPa, 1 atm, for the electronics (840), the electronics (840) comprising a processor (850) configured to determine the torque based on the detected twist.2 The system according to claim 1 , further comprising a robotic arm with an end effector (400), the end effector (400) comprising the support (710), the motor (730), the shaft (740), the first encoder (810), the second encoder (820), the housing (830), and the electronics (840).3 The system according to claim 2, wherein the robotic arm (630) comprises a base (100); a first arm (200) comprising a first end (210) rotatably connected to the base (100) for rotation around a first rotational degree of freedom (R1), and a second end (220) opposite the first end (210); a second arm (300) comprising a third end (310) rotatably connected to the second end (220) for rotation around a second rotational degree of freedom (R2) parallel to the first rotational degree of freedom (R1), and a fourth end (320) opposite the third end (310) of the second arm (300); and the end effector (400) connected to the fourth end (320) for rotation around a third rotational degree of freedom (R3) being parallel to the second rotational degree of freedom (R2).4 The system according to claim 2 or 3, wherein the robotic arm is removably attached subsea.5 The system according to claim 3 or 4, wherein the first arm (200) and the second arm (300) are configured to have complimentary shapes to allow at least a major part of one of the arms to fold into the other arm such that when they are folded together at least a major part of one arm is positioned within the outer boundary of the other arm.6 The system according to any one of claims 2 to 5, wherein the end effector (400) comprises a flexible element (410) allowing the end effector (400) to rotate around a fifth rotational degree of freedom (R5) perpendicular to the third rotational degree of freedom (R3).7 The system according to any one of the preceding claims, wherein the shaft (740) is at least partially shaped as a hollow cylinder.8 The system according to any one of the preceding claims, further comprising a redundant housing (832) comprising redundant electronics (842) and a redundant processor (852), corresponding to the housing (830) with its electronics (840) and processor (850); and / or wherein the processor (850) is configured to store data comprising the determined torque value.9 A subsea system comprising the system according to any one of the preceding claims 2 to 7, the subsea system further comprising a subsea installation (600) comprising at least two pieces of subsea equipment (610, 620) to be operated by the robotic arm (630) and an interface position (640) for remote installation of the robotic arm (630).10 A method for remotely operating subsea equipment (770) with at least two different torque values with a tool (760) with the system according to any one of the preceding claims, the method comprising engaging (910) a piece of subsea equipment (770) with the tool (760); andoperating (920) the subsea equipment (770) with the tool (760) to a predetermined torque while receiving feedback from the processor (850) of the torque based on the detected twist.11 The method according to claim 10, further comprising operating (930) a subsequent subsea equipment (770) with the tool (760), or a different tool, uncalibrated to a different predetermined torque while receiving feedback from the processor (250) of the torque based on the detected twist.12 The method according to any one of the claims 10 or 11 , further comprising collecting (940) data comprising the determined torque value from the processor (250) after the subsea equipment (770) has been operated with the tool (760) to the predetermined torque.13 The method according to any one of the claims 10 to 12, further comprising taking up (950) misalignment, with a flexible element (410), between a predetermined position and the actual position for the tool (760) for operating the subsea equipment (770).14 The method according to any one of the claims 10 to 13, further comprising folding (960) the end effector (100) into an arm of the robotic arm such that when they are folded together at least a major part of the end effector (100) is positioned within the outer boundary of the arm.15 The method according to any one of the claims 10 to 14, further comprising removably attaching the robotic arm subsea.

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