Offshore crew transfer

Abstract

This application describes a bow motion detection system for detecting the motion of the bow of a floating vessel and, based on the detected motion, providing an indication that it is safe and / or not

Description

[0001] OFFSHORE CREW TRANSFER

[0002] TECHNICAL FIELD

[0003] The present invention relates generally to offshore crew transfer.

[0004] Systems and methods in accordance with the invention have application in particular for assisting crew to transfer from a floating vessel, for example a crew transfer vessel (“CTV”), to an offshore structure such as an offshore wind turbine generator (“WTG”) in an offshore windfarm.

[0005] BACKGROUND

[0006] A conventional approach to crew transfer from a CTV to a WTG is for the skipper of the CTV to control the propulsion systems of the CTV to push the bow against the WTG structure. Friction between the bow and the structure helps to hold the bow of the CTV in place on the structure. Crew members can then step from the bow of the CTV onto the WTG structure. However, the transfer can only take place in suitable sea state conditions.

[0007] Sea state is the general condition of the free surface on a large body of water (i.e. the sea in this case) - with respect to wind waves and swell - at a certain location and moment.

[0008] The motion of the waves tends to cause relative movement between the CTV and the WTG structure (which is a fixed structure). If the current sea state means either or both of the vertical rise and fall or roll of the bow of the CTV relative to the WTG structure are too great or too rapidly changing, then the friction between the bow of the CTV and the structure will be insufficient to prevent sudden and significant relative movement between the two and the crew transfer should not go ahead.

[0009] Typically, each offshore windfarm site will stipulate its ‘sea state’ working parameters for safe transfer from the CTV to the WTG.

[0010] On occasions when the sea state is on the limit or close to the limit and rising, it falls to the skipper of the CTV and the lead “AT” (Authorised Technician) to decide whether it is safe for a crew member to transfer or not. This approach relies on the judgement of these decision makers, based on their experience and the guidelines they operate under, and is open to undue pressure on a decision through peer pressure or commercial pressure to make the transfer.

[0011] The transfer operation is fraught with danger, especially for the crew members at the moment of transfer from the CTV to the WTG platform. It is a cause of stress for the skipper and AT of the CTV, as well as the crew members who are transferring from the CTV to the WTG.

[0012] Solutions have been proposed to this problem, including the system described in W02020 / 007637. This document describes an approach for crew transfer vessels that uses a wave detection device (e.g. an x-band radar or LIDAR device) to detect sea waves and a predicting system for predicting bow motion of the crew transfer vessel in response to the detected sea waves. A “go” or “no go” transfer decision is made based on the predicted bow motion.

[0013] SUMMARY OF INVENTION

[0014] Embodiments of the invention are generally aimed at providing an improved, in particular more objective and safer, approach to crew transfer from a floating vessel to an offshore structure (and back again) by providing real-time feedback about the movement of the vessel to the crew member who is about to transfer.

[0015] With this aim in mind, it is proposed that embodiments of the invention make use of a bow motion detection system, mounted at the bow of the floating vessel, which is able to detect the motion of the bow in real time and, based on the detected motion, provide an indication whether it is safe for a crew member to transfer or not.

[0016] With this approach, the “go” or “no go” decision no longer need be made by an individual whose judgement could be somewhat subjective and potentially influenced (even subconsciously) by commercial and other non-safety-related factors. Rather, the “go” or “no go” indication is given impartially by the bow motion detection system, mitigating the dangers discussed above. As the decision is made based on real time bow motion, no reliance needs to be placed on predicted motions. The term “floating vessel” used herein is intended to cover any vessel from which a person (crew member) can be transferred to an offshore structure. One example is a crew transfer vessel (CTV), including CTVs for offshore windfarms.

[0017] The term “offshore structure” used herein is intended to cover any offshore structure to which people (crew members) transfer from a floating vessel (e.g. a CTV). One example is a wind turbine generator (WTG) platform. The structure will typically be a fixed structure but embodiments of the invention may also be deployed in scenarios where the structure is itself floating, for example an anchored floating platform.

[0018] In a first aspect, the invention provides a bow motion detection system for a floating vessel, the system comprising: a housing mountable to the vessel at its bow; one or more sensors within the housing for detecting motion of the housing in at least one dimension and producing an output signal based on the detected motion; a processor within the housing, configured (e.g. controlled by software stored in memory accessible to the processor) to receive the sensor output signal, based on the sensor output signal to make a determination whether it is safe and / or not safe for a person to transfer from the vessel to a structure adjacent the bow of the vessel, and to output a corresponding indication signal; and an indicator device on or within the housing for receiving the indication signal from the processor and providing an indication perceptible from the exterior of the housing to a person stood near to the housing to indicate to the person whether it is safe and / or not safe to transfer from the vessel to the structure.

[0019] When the housing is mounted to the vessel at its bow, the housing moves with the bow of the vessel and the motion of the housing equates to the motion of the bow, so the sensor(s) provide a real time measure of the bow motion.

[0020] This self-contained unit, with all of the elements of the system within or on the housing, can conveniently be mounted on a vessel and quickly and easily put into operation.

[0021] In some embodiments, the one or more sensors can detect at least one or more of: the vertical rise and fall of the housing; - the roll angle of the housing;

[0022] - the pitch angle of the housing;

[0023] - the yaw angle of the housing;

[0024] - the rate of change of the vertical rise and fall of the housing;

[0025] - the rate of change of the roll angle of the housing;

[0026] - the rate of change of the pitch angle of the housing; and

[0027] - the rate of change of the yaw angle of the housing.

[0028] In some embodiments, the processor is configured to make the determination whether it is safe and / or not safe for a person to transfer based on any one of or any combination of any two or more of: maximum vertical rise and fall of the housing, maximum roll angle of the housing, maximum pitch angle of the housing, maximum yaw angle of the housing, maximum rate of change of vertical rise and fall of the housing, maximum rate of change of roll angle of the housing, maximum rate of change of pitch angle of the housing, and maximum rate of change of yaw angle of the housing.

[0029] The specific values for the motion parameters used to make the ”go” or “no go” decision can be set based, for example, on the sea state working parameters dictated for the specific offshore site.

[0030] In some embodiments, the indicator device can be configured to indicate when it is safe to transfer from the vessel to the structure, to indicate when it is not safe to transfer from the vessel to the structure, or both.

[0031] Indicating both conditions is more fail safe because if neither condition is indicated it would then suggest a fault in the system. In contrast, if only one of the conditions is indicated, a lack of indication caused by a fault could wrongly be taken to mean that the opposite condition is true.

[0032] In some embodiments the indicator device comprises one or more visual indicators, for example lights. For example, at least two different colour lights could be used, one to indicate that it is safe to transfer and the other to indicate that it is not safe to transfer. In accordance with norms, a green light could be used to indicate that it is safe to transfer and a red light to indicate that it is not safe to transfer.

[0033] In some embodiments, the system further comprises a second indicator device remote from the housing and in communication with the processor to receive the indication signal from the processor and provide a perceptible indication to a person stood near to the second indicator device to indicate to the person whether it is safe and / or not safe to transfer from the vessel to the structure. In this way, the indication can be readily available, for example, to the skipper or other person in the wheelhouse of the vessel, as well as the crew members at the bow. The communication may, for example, be wireless. One example of a suitable wireless communication protocol is Bluetooth™.

[0034] In a second aspect, the invention provides a method of crew transfer from a floating vessel to an offshore structure, the method comprising: measuring, in real time, the motion of the bow of the vessel; making a determination, based on the measured bow motion, as to whether it is safe and / or not safe for a person to transfer from the floating vessel to an offshore structure adjacent the bow of the vessel; and based on the determination, providing an indication to a person whether it is safe and / or not safe to transfer from the vessel to the structure.

[0035] The method may make use of a bow motion detection system as described above in connection with the first aspect of the invention.

[0036] The skilled person will appreciate that the features described and defined in connection with the aspects of the invention and the embodiments thereof may be combined in any combination, regardless of whether the specific combination is expressly mentioned herein. Thus, all such combinations are considered to be made available to the skilled person.

[0037] For the avoidance of doubt, the skilled person will appreciate that in this specification the terms “vertical”, “rise”, “fall”, “roll”, “pitch”, “yaw”, etc refer to motion of the floating vessel as found in the example when in normal use and are included to help the skilled person understand the movement of the vessel relative to the offshore structure, irrespective of their actual orientation in space. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIGURE 1 schematically shows a bow motion detection system in accordance with an embodiment of the present invention; and

[0039] FIGURE 2 shows components of the main unit of the system of fig. 1.

[0040] DETAILED DESCRIPTION OF THE EMBODIMENT

[0041] An embodiment is described below by way of example with reference to the accompanying drawings.

[0042] In the exemplified embodiment, illustrated schematically in fig. 1, the system is provided in a self-contained unit, mountable at the bow of a crew transfer vessel (CTV). It may be mounted, for example, on the foredeck safety rail of the CTV.

[0043] The unit includes motion sensors, for example accelerometers, to measure motion of the unit, and hence the bow of the vessel on which it is mounted, in multiple dimensions. The unit also includes a processor, which interprets the sensor outputs to assess whether or not the motion of the bow is above or below safe thresholds, in order to make a ”go” / “no go” decision for transfer of crew from the CTV to an offshore structure (e.g. a WTG). The thresholds can be set based on sea state working parameters dictated for the specific offshore site.

[0044] The decision can be notified to users via indicator lights on the unit, green for “go” and red for “no go”.

[0045] The exemplified embodiment also includes a wheelhouse unit. This unit is in effect a repeater for the “go” / “no go” decision, with its own set of green and red lights to indicate the decision to personnel who can see the wheelhouse unit. The wheelhouse unit is in wireless communication with the main, self-contained unit via a Bluetooth™ connection. The operation of the green and red lights is driven by a signal from the processor in the main unit, transmitted via the wireless connection. Both the main unit and the wheelhouse unit include their own power source, for example rechargeable batteries.

[0046] In use, the main unit is mounted at the bow of the CTV and the wheelhouse unit is mounted in the wheelhouse of the CTV. Once the vessel is pushed on to the offshore structure, the measurement process is initiated and the units observed to view the “go” or “no go” indication as the case may be.

[0047] In this example, the “go” / “no go" indication is determined based on whether or not limit values are breached (i.e. exceeded) for one or more off roll angle, pitch angle, yaw angle, or rates of change of these angles. If a limit value is exceeded, a “no go” condition is indicated.

[0048] In other embodiments, a “no go” condition may be determined based on specific combinations of two or more limits being breached.

[0049] The features of one example of the electronics onboard the main unit are now described with reference to fig. 2.

[0050] The unit includes the following components: a processor (“Teensy 3.2”); an inertial measurement unit, IMU, (“BNO55”), combining accelerometer, gyroscope, magnetometer and orientation software; a pressure / altitude / temperature sensor (“MCL3115 A2”); an SD Card reader / SD card (for recording the sensed motion); a set of status LEDs (red, blue and white); and a set of “go” / “no go” LEDs (green and red). LED Behaviour

[0051] Go / NoGo LED

[0052] The go / nogo LED is GREEN when a roll / pitch breach hasn’t occurred in the specified timeframe.

[0053] The go / nogo LED is RED when a roll / pitch breach has occurred within the specified timeframe.

[0054] Status LED

[0055] The status LED will be WHITE when the unit is in the ready state, ie neither logging, nor reporting an error.

[0056] The status LED will flash BLUE when logging to the SD card is in progress.

[0057] The status LED will flash RED when an error has been encountered. In this state the unit should be connected to a PC to track the cause of the error.

[0058] Errors include:

[0059] - Error detecting / writing to SD card

[0060] - Error detecting the pressure sensor

[0061] Error detecting the IMU

[0062] Power

[0063] The unit includes a 5200mAh lithium battery pack which, on a full charge will power the system for an 8 hour session.

[0064] The battery pack may be charged through a laptop or 5 V mains charger via a CHARGE port on the top panel of the unit.

[0065] The unit includes a power gauge visible through the top panel showing the quartiles of battery power remaining whilst the unit is operating, or whilst the battery pack is charging. Connection to a PC

[0066] The processor has a serial UART port accessible through a USB ‘Data’ socket on the panel.

[0067] The unit may be operated (ie config variables set, data viewed) using a terminal app such as ‘PuTTY’ or ‘Realterm’, or if preferred a PC app may be used for a more user friendly experience.

[0068] Instructions which may be manually sent to the unit include:

[0069] - D show the current data

[0070] Q stop showing the current data, useful when displaying the config variables

[0071] ? Show the config variables

[0072] X Reset the current alarm (if triggered)

[0073] - F List the files on the SD card

[0074] T Set the current time (T=dd / mm / yyyy hh:mm:ss)

[0075] - R0AN=x Set the roll angle limit (in degrees) to x

[0076] - PIAN=x Set the pitch angle limit to x

[0077] YAAN=x Set the yaw angle limit to x

[0078] - R0RA=x Set the roll angle rate of change (in degrees per sec) to x

[0079] - PIRA=x Set the pitch angle rate of change (in degrees per sec) to x

[0080] YARA=x Set the yaw angle rate of change (in degrees per sec) to x

[0081] Setting a breach angle, or rate of change of angle to zero will disable that particular source of a ‘breach’. - ROTO=x Set the roll breach timeout to x seconds

[0082] - PITO=x Set the pitch breach timeout to x seconds

[0083] YATO=x Set the yaw breach timeout to x seconds

[0084] - PLOG=n Set the logging period to n seconds (0.5 to 3600) The config variables are stored in non-volatile EEPROM memory so are not lost on power down.

[0085] Lossins to the SD Card

[0086] Live data may be logged to an SD card at a configurable rate (max 2Hz).

[0087] Data is saved in a comma separated format where the filename is created automatically from the timestamp when logging starts, with the naming convention ddmmhhMM.csv

[0088] The field order is:

[0089] Log ID Auto-increments

[0090] Timestamp Dd / MM / yyyy hh:mm:ss Air pressure mBar Temperature Degrees Celsius Roll angle Degrees Pitch angle in degrees Yaw angle in degrees Roll Alert (1 = alert state)

[0091] Pitch Alert (1 = alert state) Yaw Alert (1 = alert state) Roll threshold angle Degrees Pitch threshold angle Yaw threshold angle Roll alert timeout Seconds Pitch alert timeout Yaw alert timeout.

[0092] The skilled person will understand that various modifications and additions can be made to the example described above without departing from the spirit and scope of the present invention.

Claims

CLAIMS:

1. A bow motion detection system for detecting the motion of the bow of a floating vessel and, based on the detected motion, providing an indication that it is safe and / or not safe for a person to transfer from the floating vessel to an offshore structure adjacent the bow of the vessel, the system comprising: a housing mountable to the vessel at its bow; one or more sensors within the housing for detecting motion of the housing in at least one dimension and producing an output signal based on the detected motion; a processor within the housing, configured to receive the sensor output signal, based on the sensor output signal make a determination whether it is safe and / or not safe for a person to transfer, and output a corresponding indication signal; and an indicator device on or within the housing for receiving the indication signal from the processor and providing an indication perceptible from the exterior of the housing to a person stood near to the housing to indicate to the person whether it is safe and / or not safe to transfer from the vessel to the structure.

2. A system according to claim 1, wherein the one or more sensors can detect at least the vertical rise and fall of the housing.

3. A system according to claim 1 or claim 2, wherein the one or more sensors can detect at least the roll angle of the housing.

4. A system according to any one of the preceding claims, wherein the one or more sensors can detect at least the pitch angle of the housing.

5. A system according to any one of the preceding claims, wherein the one or more sensors can detect at least the yaw angle of the housing.

6. A system according to any one of the preceding claims, wherein the one or more sensors can detect at least the rate of change of the vertical rise and fall of the housing.

7. A system according to any one of the preceding claims, wherein the one or more sensors can detect at least the rate of change of the roll angle of the housing.

8. A system according to any one of the preceding claims, wherein the one or more sensors can detect at least the rate of change of the pitch angle of the housing.

9. A system according to any one of the preceding claims, wherein the one or more sensors can detect at least the rate of change of the yaw angle of the housing.

10. A system according to any one of the preceding claims, wherein the processor is configured to make the determination whether it is safe and / or not safe for a person to transfer based on any one of or any combination of any two or more of: maximum vertical rise and fall of the housing, maximum roll angle of the housing, maximum pitch angle of the housing, maximum yaw angle of the housing, maximum rate of change of vertical rise and fall of the housing, maximum rate of change of roll angle of the housing, maximum rate of change of pitch angle of the housing, and maximum rate of change of yaw angle of the housing.

11. A system according to any one of the preceding claims, wherein the indicator device is configured to indicate when it is safe to transfer from the vessel to the structure.

12. A system according to any one of the preceding claims, wherein the indicator device is configured to indicate when it is not safe to transfer from the vessel to the structure.

13. A system according to any one of the preceding claims, wherein the indicator device is configured to indicate both when it is safe to transfer from the vessel to the structure and when it is not safe to transfer from the vessel to the structure.

14. A system according to any one of the preceding claims, wherein the indicator device comprises one or more visual indicators.

15. A system according to claim 14, wherein the or each visual indicator is a light.

16. A system according to claim 15, comprising at least two different colour lights, one to indicate that it is safe to transfer and the other to indicate that it is not safe to transfer.

17. A system according to claim 15 or claim 16, wherein the indicator device comprises a green light to indicate that it is safe to transfer.

18. A system according to any one of claims 15 to 17, wherein the indicator device comprises a red light to indicate that it is not safe to transfer.

19. A system according to any one of the preceding claims, further comprising a second indicator device remote from the housing and in communication with the processor to receive the indication signal from the processor and provide a perceptible indication to a person stood near to the second indicator device to indicate to the person whether it is safe and / or not safe to transfer from the vessel to the structure.

20. A crew transfer vessel comprising a bow motion detection system according to any one of the preceding claims, with the housing of the system mounted at the bow of the crew transfer vessel.

21. A crew transfer vessel comprising a bow motion detection system according to claim 19, with the housing of the system mounted at the bow of the crew transfer vessel and the second indicator device mounted in a wheelhouse of the vessel.

22. A method of crew transfer from a floating vessel to an offshore structure, the method comprising: measuring, in real time, the motion of the bow of the vessel; making a determination, based on the measured bow motion, as to whether it is safe and / or not safe for a person to transfer from the floating vessel to an offshore structure adjacent the bow of the vessel; and based on the determination, providing an indication to a person whether it is safe and / or not safe to transfer from the vessel to the structure.

23. A method according to claim 22, wherein the method uses a bow motion detection system according to any one of claims 1 to 19 for measuring the real time motion of the bow of the vessel.

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