Fibre rope and hoisting system including such a fibre rope

Abstract

There is described a hoisting system and method of lifting that make use of a particular fibre rope. The fibre rope includes a plurality of magnets that are embedded within the fibre rope and spaced apart along the rope with a known axial distance between the magnets. The system may include a fibre rope hoisting speed sensor, and a magnetic field sensor that can sense the presence of the magnetic field of the embedded magnets. Using the sensors, the hoisting speed of the rope may be determined by: measuring the time between the passing of consecutive magnets by using the magnetic field sensor; calculating the distance between consecutive magnets using the hoisting speed sensor and the measured time between the passing of the consecutive magnets; and comparing the calculated distance between the magnets with an original, predefined distance between the magnets.

Claims

1. A hoisting system comprising: a fibre rope comprising a plurality of magnets embedded within the fibre rope with an axial distance therebetween along the fibre rope, wherein each of the plurality of magnets is a permanent magnet with a temperature-dependent magnetic field strength; a magnetic field sensor configured to sense the presence of the magnetic field of said magnets that are embedded in the fibre rope; a fibre rope hoisting speed sensor configured to measure the hoisting speed of the fibre rope; and a control unit configured to calculate the temperature of the plurality of magnets based on the magnetic field strength of the plurality of magnets measured by the magnetic field sensor, wherein the control unit is further configured to measure the time between the passing of consecutive magnets of the plurality of magnets embedded in the fibre rope as sensed by the magnetic field sensor, calculate the distance between the consecutive magnets based on the hoisting speed measured by the fibre rope hoisting speed sensor and the measured time between the passing of said consecutive magnets, and compare the calculated distance between the consecutive magnets with an original, predefined distance between the consecutive magnets.

2. Hoisting system according to claim 1, wherein the hoisting system further comprises a position sensor configured to sense different fibre rope position identifiers so as to uniquely identify different portions of said fibre rope.

3. Hoisting system according to claim 1, wherein said hoisting system further comprises an optical sensor configured to sense optically detectable marks that are on said fibre rope.

4. Hoisting system according to claim 1, wherein the hoisting system further comprises: a position sensor configured to sense different fibre rope position identifiers so as to uniquely identify different portions of said fibre rope; and an optical sensor configured to sense optically detectable marks that are on said fibre rope; wherein said magnetic field sensor, said position sensor, and said optical sensor are embedded within a common housing that is configured for receiving the fibre rope therethrough.

5. Hoisting system according to claim 1, wherein the hoisting system further comprises an infrared sensor configured to sense the temperature of said fibre rope.

6. The hoisting system of claim 5 wherein the infrared sensor is configured to sense the external surface temperature of said fibre rope.

7. Hoisting system according to claim 1, wherein the hoisting system comprises a knuckle-boom crane or a stand-alone winch system.

8. The hoisting system of claim 1 wherein the magnetic field sensor is configured to sense the magnetic field strength of the magnetic field of said magnets that are embedded in the fibre rope.

9. The hoisting system of claim 1 wherein the magnetic field sensor is configured to sense the orientation of the magnetic field of said magnets that are embedded in the fibre rope.

10. Hoisting system according to claim 1, wherein said permanent magnets are embedded in the core of said fibre rope.

11. Hoisting system according to claim 1, wherein said fibre rope further comprises a plurality of fibre rope position identifiers spaced along the fibre rope.

12. Hoisting system according to claim 1, wherein the fibre rope further comprises a plurality of optically detectable marks provided with an axial distance therebetween along the fibre rope.

13. Hoisting system according to claim 12, wherein the axial positions of said optically detectable marks substantially coincide with the axial positions of said magnets along the fibre rope.

14. Hoisting system according to claim 1, wherein said fibre rope further comprises a continuous and optically detectable mark along at least a portion of said fibre rope.

15. Method for operating a hoisting system, the method comprising: measuring the magnetic field strength of a plurality of magnets embedded within and axially spaced along a fibre rope, wherein each of the plurality of magnets is a permanent magnet with a temperature-dependent magnetic field strength; calculating the temperature of the plurality of magnets based on the measured magnetic field strength of the plurality of magnets; measuring the hoisting speed of the fibre rope by means of the fibre rope hoisting speed sensor; measuring the time between the passing of consecutive magnets of the plurality of magnets that are embedded in the fibre rope by means of a magnetic field sensor; calculating the distance between the consecutive magnets by means of said hoisting speed sensor and said measured time between the passing of said consecutive magnets, and comparing said calculated distance between the consecutive magnets with an original, predefined distance between the consecutive magnets.

Description

BRIEF INTRODUCTION OF THE DRAWINGS

(1) In the following is described exemplary embodiments as illustrated in the accompanying drawings, wherein:

(2) FIG. 1A shows, in a side view, a fibre rope according to the present disclosure;

(3) FIG. 1B shows, in a cross-sectional side view, the fibre rope from FIG. 1A;

(4) FIG. 2 shows, in a cross-sectional view and in larger scale, the fibre rope from FIG. 1A;

(5) FIG. 3 shows, in a side view, a hoisting system according to the second aspect of the disclosure;

(6) FIG. 4 shows a detail from FIG. 3;

(7) FIG. 5 shows, schematically, a housing with a fibre rope running therethrough;

(8) FIG. 6A shows, in a top view, a housing, including several sensors, with a fibre rope running therethrough;

(9) FIG. 6B shows, in a cross-sectional side view, the housing from FIG. 6A; and

(10) FIG. 7 shows, in a perspective and partially transparent view, a housing with a fibre rope running therethrough

DETAILED DESCRIPTION OF THE DISCLOSED EXEMPLARY EMBODIMENTS

(11) In the following the reference numeral 1 will indicate a fibre rope according to the first aspect of the present disclosure, whereas the reference numeral 10 indicates a hoisting system according to the second aspect of the disclosure. Identical reference numeral will indicate identical or similar features in the drawings. The drawings are shown simplified and schematic and the various features in the drawings are not necessarily drawn to scale.

(12) The upper portion of FIG. 1A and FIG. 1B shows a part of a fibre rope 1, while the lower portion of the figure shows the same part of the fibre rope 1 in a cross-section along the rope. In the shown embodiment the fibre rope comprises High Modulus Polyethylene (HMPE) and/or High-Performance Polyethylene (HPPE) fibres, but it could also be based on any other type of fibre, such as e.g. ara-mid, liquid crystal polymer, polyamides, polyester, carbon etc. As can be seen from the upper portion of FIG. 1A and FIG. 1B, the outside of the fibre rope 1 is provided with optically detectable, transverse marks 2 with a fixed, axial distance therebetween. The distance in the shown embodiment is in the order of 1 meter and it will be predefined. Other predefined distances may be used in other hoisting systems 10. As will be explained in the following, the distance between consecutive marks 2 will be indirectly measured in real-time, where an increased length may be indicative excessive creep due to heating and/or load. In addition to the transverse marks 2 provided around the circumference of the fibre rope 1, the outside out the fibre rope 1 is also provided with an optically detectable continuous mark 4 along the axial length of the shown portion of the fibre rope 1. The continuous mark 4 may be used to measure local twisting of the fibre rope 1 as will also be explained below, where excessive twisting may also be a discard criteria. The fibre rope 1 is further provided with a plurality of fibre rope position identifiers 6, shown as RFID tags in this exemplary embodiment. The RFID tags 6 are embedded in the fibre rope 1, such as near the outer surface of the fibre rope, in order to uniquely identify various length portions of the fibre rope 1. The unique identification of various length portions of the fibre rope 1 becomes particularly useful in combination with the sensing of other fibre rope parameters, such as length extension, twist and temperature so as to be able to identify which portions of the fibre rope 1 are exposed to the mentioned wear-critical parameters. The distance between the RFID tags 6 along the fibre rope 1 may, but need not be, similar to the distance between the optically detectable transverse marks 2. In the shown embodiment, the optically detectable marks are also visually detectable.

(13) The lower portion of FIG. 1A and FIG. 1B shows a cross-section along the length of the fibre rope 1. A plurality of magnets 8 are embedded in the fibre rope 1 substantially at the core 12, i.e. the radial centre, of the fibre rope 1. In the shown embodiment, the magnets 8 are separated from the rest of the fibre rope 1 by means of a protective sleeve 14, which may be particularly useful if the fibre rope is to be submerged in water. The sleeve 14 will create an impediment between the magnets 8 and sea water, thus preventing deterioration and magnetic field loss of the magnets. The sleeve 14 may typically comprise a polymeric material which is flexible and compact. The magnets 8 are of a permanent type with a temperature-dependent magnetic field strength, which makes it possible to measure the core temperature of the fibre rope by means of magnetic field strength measurements, typically with one or more hall-effect sensors connectable to a control unit as will be explained below. The axial distance between the magnets along the rope may coincide with the distance between the transverse visual marks 2. The combined use of both visual transverse marks 2 and embedded magnets 8 gives redundancy in the fibre rope 1 elongation monitoring. Fibre ropes 1 are already known that are provided with an internal sleeve 14 for improving radial stiffness of the rope. As such, the magnets 8 may be included inside such a sleeve 14, thus exploiting the already existing infrastructure.

(14) FIG. 2 is a cross-section, in a larger scale than FIG. 1, of the fibre rope 1 in a plane perpendicular to the length of the fibre rope 1. The magnet 8 is shown in the protective sleeve 14 surrounded by HMPE fibre 17.

(15) FIG. 3 shows a hoisting system 10 according to the second aspect of the disclosure, the hoisting system 10 comprising a fibre rope 1 according to the first aspect of the disclosure. In the shown exemplary embodiment the hoisting system 10 is provided as a knuckle-boom crane 10, though the fibre rope 1 could be used in any kind of hoisting system, including on any kind of crane and also in stand-alone winch systems. This particular kind of knuckle-boom crane 10, which is provided with a not shown winch drum orientated with the drum axis substantially vertical and with the winch drum as an integrated part of the crane support structure, was described in PCT/N02016/050047. The knuckle boom crane 10 may be use to lower and lift heavy loads to and from a seabed several thousand meters below sea-level. The knuckle-boom crane 10 will be moving together with the vessel on which is it placed due the impact of waves and wind. In certain parts of such a hoisting operation it may be necessary to keep the load substantially fixed relative to the seabed or to another reference system not moving together with the knuckle-boom crane 10. It may therefore be necessary to operate the knuckle-boom crane 10 in heave compensation mode, implying that the same portion of the fibre rope 1 undergoes numerous bending cycles under load, which may lead to excessive heating and potentially unacceptable wear of portions of the fibre rope 1.

(16) To monitor the temperature, elongation, twist and potentially also shaped change of the fibre rope 1, a housing 16, including a plurality of various sensors as will be explained in the following, is installed near a guiding sheave 18 on a main boom 20 of the knuckle-boom crane 10. Several such housings 16 may be installed along the length of the wire on the knuckle-boom crane 10 for measuring simultaneously on multiple locations along the fibre rope 1, but only one is used in the shown embodiment. Another housing 16 could e.g. be placed near a second guiding sheave 22 at the distal end of the main boom 20 where the knuckle-boom 24 is rotatably connected. The luffing motion of the knuckle-boom crane 10 is enabled by means of a first cylinder 19 adapted to lift and lower the main boom 20, while the knuckle-boom crane 10 is further provided with a second cylinder 26 for articulating the knuckle-boom 10 relative to the main boom 20 as will be understood by a person skilled in the art. A load suspension member 28 in the form of a hook is connected to the end of the fibre rope 1 hanging from the distal end of the knuckle-boom 24 for the connection of a not shown load to the fibre rope 1. The knuckle-boom crane 10 is also adapted to slew in the horizontal plane relative to a not shown pedestal.

(17) FIG. 4 shows an enlarged portion of the encircled part B from FIG. 3. The figure shows schematically the fibre rope 1 running through the housing 16 covering multiple sensors. The housing 16 is placed immediately after the guiding sheave 18 on the main boom 20 in the direction from the not shown winch drum towards the second guiding sheave 22 and the load suspension member 24 as shown in FIG. 3.

(18) The housing 16 with the fibre rope 1 running therethrough is shown in a perspective view in FIG. 5 and in a semi-transparent perspective view in FIG. 7, while FIG. 6A and FIG. 6B shows the housing 16 and fibre rope 1 in an end-view in an upper portion of the figure and in a cross-section through the line A-A in the lower portion of the figure. Inside the housing 16, there is provided two magnetic sensors 30. The magnetic sensors 30 are adapted to sense the passing of the magnets 8 through the housing 16. The hoisting system 10 is also provided with a not shown control unit including a timer function for measuring the time between the passing of consecutive magnets. Combined with input about fibre rope 1 speed, this makes it possible to calculate the distance between the embedded magnets 8, and hence also any change in distance. In the exemplary embodiment shown, the magnets 8 are of a permanent type with a magnetic field strength dependent on temperature. The magnetic sensors 30 are therefore, in this shown embodiment, of a type adapted to measure the magnetic field strength of the magnets 8. This makes it possible to calculate the core temperature of the fibre rope 1 in a reliable, efficient and non-intrusive way. The conversion from measured magnetic field strength to temperature may be found in a simple pre-calibration experiment, or it may also be found in look-up tables for certain frequently used permanent magnets as mentioned herein. Normally, the hoisting system include a control unit adapted to receive the measured magnetic field strength from the magnetic sensor and to calculate the temperature of the magnet, and thereby also the temperature at the core of the fibre rope, based on the measured magnetic field strength.

(19) Also, in the shown embodiment the magnetic sensors 30 are adapted to sense the direction of the magnetic field. The sensors used in this specific embodiment are three-dimensional magnetic hall effect sensors commercially available from the company Infineon Technologies AG. The housing is also provided with a fibre rope position sensor, here in the form of a RFID sensor/reader 32 for uniquely identifying the RFID tags 6 embedded in the fibre rope 1. Giving each length portion of the fibre rope 1 its own unique recognizable signature is very useful for knowing which portions of the fibre rope 1 that are subject to wear, creep, twist etc. at any time. Preferably the not shown control unit is connected to or comprises a storage unit adapted to store measured and calculated data from the different portions of the fibre rope 1, such as temperature data, elongation data, twist data, number of bending cycles under load data etc. Data from different time intervals may be compared so as to detect change. The housing 16 is further provided with cameras 34 for monitoring the transverse and continuous visual marks 2, 4. A plurality of such cameras may be distributed circumferentially around the fibre rope in the housing 16. In the shown embodiment only two cameras are used, but in alternative embodiments more cameras 34 may be used. In a particularly useful embodiment four cameras 34 may be placed evenly around the fibre rope 1 with 90° between each. The cameras 34 may be used in the same way as the magnets 8 to measure the distance between the transverse marks 2 so as to monitor any elongation of the fibre rope 1. The cameras 34 also monitor the axial continuous mark 4. The time from when one and the same camera 34 sees the continuous mark 4 to the next time the same camera 34 sees the continuous mark 4, i.e. the time between each 360° twist of the fibre rope, can be used to calculate the twist per meter. Once the camera 34 stops seeing the continuous mark 4 a control unit timer starts. The timer stops when the same camera 34 sees the continuous mark again. The cameras 34 will also monitor the shape and ovality of the fibre rope 1, while the control unit compares the latest data with the original shape and ovality of the fibre rope 1. The shape change, such a reduction in diameter, may also be compared with the elongation of the fibre rope 1. An increase in diameter compared to a set value will typically be an indication of slack in the fibre rope 1 or degraded fibres which may also be cross-checked by a not shown load cell value. The shape of the fibre rope 1 is determined by different images captured by cameras 34 circumferentially arranged with a defined angle therebetween, and/or with the inclusion of a not shown laser beams. The shape change is observed by image analysis in a control unit as will be mentioned below.

(20) The knuckle-boom crane 10 is further provided with an infrared (IR) sensor 36 for measuring the surface temperature of the fibre rope 1. In the shown embodiment the IR sensor 36 is provided outside the housing 16, however the IR sensor could equally well be included inside the housing 16. While the hall effect sensors 30 indirectly measure the core temperature of the fibre rope 1, the IR sensor 36 mainly measure the surface temperature of the fibre rope 1. By combining the two different temperature measurements, a temperature gradient in the radial direction of the fibre rope 1 may be calculated to give an indication about the heat dissipation. The temperature gradient in the length direction of the fibre rope 1 may now also be measured both at the core and at the surface.

(21) In normal operation, the speed of the fibre rope 1 is used as input for length measurements in combination with a timer. The rope speed is, in this embodiment, input from a not shown tachometer. The length measurements are used as input both for monitoring elongation and twist, but also in combination with the temperature measurements and monitoring of bending cycles under load to give an overall overview of wear and creep of the fibre rope 1. The RFIDs tags 6 and readers 32 are continuously used to identify different length portions of the fibre rope 1. Both excessive creep and twist are used as discard criteria for the worn portion of the fibre rope 1. The worn portion of the fibre rope 1 may be cut away and the two remaining ends may be spliced as will be known by a person skilled in the art. Examples of discard criteria may be 10% creep and/or 1 full twist per 10 meters, but these parameters will depend greatly on and vary between different types of fibre ropes 1. Excessive heating may also be a separate discard criterion due to the irreversible recrystallization mentioned introductorily. It should be noted that the mentioned limits may vary greatly between different hoisting systems 10 and in particular between different types of fibre ropes 1.

(22) In a particular embodiment, the hoisting system 10 includes one or more not shown cooling members. Some portions of the hoisting system 10, such as the winch drum, may be stored in a housing with a constantly controlled and cooled atmosphere. Other parts of the hoisting system 10, such as the area around the guiding sheaves 18, 22 where the fibre rope 1 undergoes numerous bending cycles and the temperature in-creases due to internal and external friction in the fibre rope 1, may be cooled when the fibre rope reaches a pre-set temperature. The conditional cooling will typically take place when the hoisting system 10 is set in heave compensation mode, where it may operate for several hours. Cooling may be done by means of flushing with water, electrolytes, air jets or other cooling fluids.

(23) It should be noted that the above-mentioned embodiments illustrate rather than limit the disclosure, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

(24) The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.