NL2001656C2

NL2001656C2 - Hoisting device/hoisting crane for laying e.g. pipeline, on seabed during construction of e.g. underwater installation, has control unit compensating output signal of output unit based on measured joint diameter

Info

Publication number: NL2001656C2
Application number: NL2001656A
Authority: NL
Inventors: Joop Roodenburg; Johannes Hovestadt
Original assignee: Itrec Bv
Priority date: 2008-06-06
Filing date: 2008-06-06
Publication date: 2009-06-08

Abstract

The device has a traction winch (35) moving an elongated body (36), and a reel (74) performing subsequent reeling of the body. A control unit (100) has an input part for receiving a speed signal (101) that represents a speed of the body. A half input part receives input from a half speed signal (102) that represents a reel speed of the reel. The control unit calculates a nominal diameter (D1) of the reel speed based on the speed signal, and measures a joint diameter (D2) from the nominal diameter. The control unit compensates an output signal (104) of an output unit based on the diameter (D2). Independent claims are also included for the following: (1) a software program comprising a set of instructions for controlling a hoisting device/hoisting crane (2) a method for controlling a hoisting device/hoisting crane.

Description

P29434NLOO/RPO

Title: Hoisting device and method for controlling a hoisting device

FIELD OF THE INVENTION

The present invention relates to a hoisting device according to the preamble of claim 1. The present invention further relates to a method of controlling a hoisting device according to the preamble of claim 7.

5 BACKGROUND OF THE INVENTION

Known hoisting devices of this kind are used for the retrieval of elongated bodies such as cables or pipelines that are to be placed on the seabed. In particularly, the invention relates to hoisting devices intended to haul very heavy loads by means of a cable, a not 10 inconsiderable part of the load being often constituted by the weight of the cable, generally a cable of large diameter and of very great length. The invention also concerns the application of such a hoisting device or winch to off-shore technologies, e.g. for abandonment and recovery applications, oceanography and dredging at great depths. The invention also concerns the application of laying a pipeline in the offshore industry when installing platforms, 15 underwater installations, etc.

Such known hoisting device usually comprise a traction device or traction winch for displacing a cable. For example when such a hoisting device is a crane, the traction device is a winch that is used to raise and lower the cable which carries a load. Further, such known 20 devices usually comprise a device for storing that part of the cable that is not directly used. Such devices are for example storage winches which have a reel onto which excess cable can be reeled.

During operation of the hoisting device the storage device should supply or store the 25 same amount of cable as is required by the traction winch in order to maintain a tension in the cable that is substantially constant. In particular a pulling tension should be present to avoid sagging. In order to maintain a substantially constant tension in the elongate body, the known devices comprise a controller that can control the speeds of the traction winch and the storage winch such that this tension is substantially constant. The controller comprises an 30 input for receiving a signal from a force measuring sensor that measures the force on the cable. On the basis of the measured force, the tension on the cable can be determined by the controller and corrective action can be undertaken if required.

-2-

The speeds and accelerations at which hoisting devices must operate are steadily increasing. Although the known way of controlling the known hoisting device gives good results, it has proven that for increased speeds and increased accelerations the performance 5 of the control strategy based on a direct measurement of the force (tension) on the cable is reducing. The main reasons for the reduced performance can be found in the hoisting system itself, such as movements of the cable at higher speeds, elastic behaviour of the mechanical components etc. Another major contributor to the reduced performance of the known control method is the fact that the reel of the storage winch will store varying lengths of cable. Hence, 10 the effective or joint diameter of the reel will vary during operation. This means, that the hoisting device will respond differently to control signals from the controller depending on the amount of cable present on the storage winch.

OBJECT OF THE INVENTION 15

The present invention aims to provide an improved hoisting device and in particular an improved method of controlling such a hoisting device, wherein the hoisting device can handle higher speeds and higher accelerations.

20 SUMMARY OF THE INVENTION

In order to provide a hoisting device that performs well even when the speeds and accelerations of the hoisting device increase, a hoisting device for hoisting an elongate body is provided, that comprises a traction device for displacing the elongate body, a reel for 25 reeling the elongate body thereon, the reel and the elongate body reeled thereon having a joint diameter, and a control unit for controlling the hoisting device. The control unit comprises a first input for receiving a first speed signal representative of a speed of the elongate body at the traction device, a second input for receiving a second speed signal representative of a reel speed of the reel, and an output for providing an output signal to control a speed of the 30 reel. The control unit is arranged to calculate a nominal diameter speed of the reel from the first speed signal, to calculate the joint diameter from the calculated nominal diameter speed and the second speed signal, and to compensate the output signal based on the calculated joint diameter.

35 Alternatively, the invention provides a method of controlling a hoisting device, the hoisting device comprising a traction device for displacing the elongate body, a reel for reeling the elongate body thereon, the reel and the elongate body reeled thereon having a joint diameter, the method comprises measuring a speed of the elongate body at the traction -3- device, calculating a nominal diameter speed of the reel from the measured speed of the elongated body, and measuring the reel speed of the reel. The method further comprises calculating the joint diameter from the calculated nominal diameter speed and the measured reel speed, and calculating the reel speed from the measured speed of the elongate body 5 and the calculated joint diameter.

The inventors have realized that the requirement of maintaining a substantially constant tension on the elongate body can also be met by controlling the speed of the reel on the basis of the speed of the elongate body at the traction device and the joint diameter of the 10 reel and the elongate body reeled thereon. In fact, the required speed of the reel does no longer need to be derived from the measured tension on the elongate body. In fact, using the speed of the elongate body at the traction device represents a feed forward signal for the controller, increasing the performance of the control.

15 By taking into account the joint or actual diameter of the reel, changes in the speed are directly responded to and consequently the dynamic behaviour of the hoist device will improve allowing higher speeds. In fact, by calculating the nominal diameter speed, a scaled feed forward control is obtained for the control of the reel speed. This ensures that the response of the hoisting device is scaled for the joint diameter. This means that by taking into 20 account the joint or actual reel diameter, the hoisting device will respond differently depending on the length of elongate body reeled on the reel, meaning that the rate of change of the reel speed will be similar independent of the joint diameter.

Another advantage of the hoisting device and method according to the invention is, 25 that higher accelerations can be achieved. As the speeds of the traction device and the reel are directly coupled in the controller, the output signal can respond much faster to changes in the speed at the traction device, allowing higher accelerations.

Another advantage of the hoisting device and method according to the invention is, 30 that in principle no additional sensors are needed to implement the improved control method. In particular no additional sensors are required to measure the thickness of the layer of elongate body on the reel. Data on the respective speeds are already available in the controller and consequently an improved and less complex hoisting device is provided.

35 BRIEF DESCRIPTION OF THE DRAWINGS

-4-

Further advantageous embodiments of the hoisting device and the method of controlling such a device according to the invention are described in the claims and in the following description with reference to the drawing, in which: 5 Fig. 1 diagrammatically depicts an offshore vessel which is suitable, inter alia, for laying a elongate body such as a pipeline on the seabed;

Fig. 2 shows a hoisting crane at the rear side of the vessel shown in Fig. 1, partially in the form of a cut-away view;

Fig. 3 shows the hoisting crane from Fig. 2 from a different direction; 10 Fig. 4 shows a view of the hoisting crane shown in Figs. 2 and 3 from above;

Fig. 5 schematically shows the hoisting device with a controller, and Fig. 6 schematically shows the hoisting device as used for laying pipelines.

DETAILED DESCRIPTION OF EXAMPLES 15

Referring to Fig’s 1 to 4 first a general description is given of a possible application of the invention.

Figure 1 shows a floating device in particular an offshore vessel 1 which is suitable for 20 hauling elongate bodies such as cables or pipelines. In the example of Figure 1, the vessel 1 is suitable for laying a pipeline on the seabed.

The vessel 1 has a hull 2 with a working deck 3 and, at the front of the hull 2, a superstructure 4 for crew accommodation, etc.

25

The vessel 1 is provided with a pipeline-laying (elongate body) installation of the S-lay type, with one or more welding stations on the working deck 3, for coupling pipeline sections 9a in a substantially horizontal orientation. On the working deck 3 there are also what are known as tensioners 8 for carrying the weight of the pipeline 9 which is hanging downwards 30 from the vessel 1.

Furthermore, the vessel 1 has a stinger 5 which projects outside the hull 2 of the vessel 1 at the rear side of the vessel 1, engages on the hull 2 at an engagement point such that it can pivot about a substantially horizontal pivot structure 6 and forms a downwardly 35 curved support for pipeline moving towards the seabed.

Furthermore, the vessel 1 has a hoisting device or hoisting crane 20, disposed in the vicinity of the same side of the hull as the stinger 5, which hoisting crane 20 has a vertical -5- structure fixed to the hull 2. The hoisting crane 20 will be described in more detail below.

Here, the crane 20 is disposed above the location where the pipeline 9 leaves the working deck 3, on the longitudinal axis of the vessel 1.

5 The hoisting crane 20, which is illustrated in detail in Figures 2-4, has a substantially hollow vertical column 21 with a foot 22, which in this case is fixed to the hull 2 of the vessel 1. Furthermore, the column 21 has a top 23.

The hoisting crane 20 has a jib 24, which is illustrated in two different positions in 10 Figure 1. An annular bearing structure 25 extends around the vertical column 21 and guides and carries a jib connection member 26, so that the jib connection member 26, and therefore the jib 24, can rotate about the column 21.

In this case, the jib connection member 26 forms a substantially horizontal pivot axis, 15 so that the jib 24 can also be pivoted up and down. There is at least one drive motor 27 for displacing the jib connection member 26 along the annular bearing structure 25. By way of example, the annular bearing structure 25 comprises one or more guide tracks which extend around the column 21 and on which an annular component 28 of the jib connection member 26 is supported via running wheels. Jib securing supports 29 are arranged on the component 20 28 at two positions. The drive motor 27 may, for example, drive a pinion which engages with a toothed track around the column 21.

To pivot the jib 24 up and down, there is a topping winch 30 provided with a topping cable 31 which engages on the jib 24.

25

Furthermore, the hoisting crane 20 comprises a hoisting winch 35 for raising and lowering a load, with an associated hoisting cable 36 and a hoisting hook 37. At the top 23 of the column 21 there is a top cable guide 40 provided with a cable pulley assembly 41 for the topping cable 31 and with a cable pulley assembly 42 for the hoisting cable 36. The hoisting 30 winch 35 is an example of a traction means which is designed to displace the hoisting cable 36 which is in turn an example of an elongate body. In the example of Fig’s 1-4 the hoisting crane 20 is used for raising and lowering a load by means of the cable 36. It is noted however that the principle is similar to the process of laying pipelines on the seabed. Such pipelines also are an example of elongate bodies which are displaced by means of a traction device, 35 also known as tensioners. An example of such tensioners when used in connection with the present invention is schematically given in Figure 6.

One or more cable pulley assemblies 43 for the hoisting cable 36 and a cable pulley -6- assembly 44 for the topping cable 31 are arranged on the jib 24. The number of cable parts for each cable can be selected as appropriate by the person skilled in the art.

The winches 30 and 35 are in this case disposed in the foot 22 of the vertical column 5 21, so that the topping cable 31 and the hoisting cable 36 extend from the associated winch 30, 35 upward, through the hollow vertical column 21 to the top cable guide 40 and then towards the cable guides 43, 44 on the jib 24. The traction means or winch 35 is for example a so-called traction winch. Such a winch has for example winch frame and, as an example, two drum assemblies each having a profiled or corrugated surface for guiding the cable. The 10 cable is wrapped around the drums a number of times. Of course other examples of winches are also possible, such as winches having sheaves which have a circumferential friction surface for the cable 36. The latter type of winches are particularly suitable for non-metallic cables, such as cables made from synthetic fibres.

15 The top cable guide 40 has a rotary bearing structure, for example with one or more running tracks around the top of the column 21 and running wheels, engaging on the running tracks, of a structural part on which the cable pulley assemblies are mounted. As a result, the top cable guide can follow rotary movements of the jib about the vertical column 21 and adopt substantially the same angular position as the jib 24.

20

The top cable guide 40 may have an associated drive motor assembly which ensures that the top cable guide 40 follows the rotary movements of the jib 24 about the column 21, but an embodiment without drive motor assembly is preferred.

25 The winches 31 and 35 are arranged on a movable winch support 50, which is mounted movably with respect to the vertical column 21. The winch support 50 here is located in the vertical crane structure, preferably in the region of the foot 22 under the circular cross section part of the column 21, and is mechanically decoupled from the top cable guide 40. The support 50 could e.g. also be arranged in the hull of the vessel below the column, 30 e.g. the foot could have an extension which extends into the hull.

In the example shown, the winch support 50 is a substantially circular platform which at its circumference is mounted in an annular bearing 51, with the winches 31, 35 arranged on the platform. The annular bearing 51 is in this case such that the platform can rotate about 35 a vertical axis which coincides with the axis of rotation of the top cable guide. The bearing can have any appropriate design including trolleys running along a circular track.

The rotatable winch support 50 has an associated drive motor assembly 52 for moving -7- the winch support 50, in such a manner that the winch support 50 maintains a substantially constant orientation with respect to the jib 24 in the event of rotary movements of the jib 24 about the vertical column 21. The orientation of the winch support 50 with respect to the top table guide 40 likewise remains substantially constant, since its movements are once again 5 the consequence of rotary movements of the jib 24.

In the embodiment shown, there is an angle sensor 60 for detecting the position of the component 28 of the jib connection member 26 with respect to the vertical column 21, the drive motor assembly 52 of the winch support 50 having associated control means 53 which 10 are in operative contact with the angle sensor 60.

The winches 31, 35 each have an associated electrical (or electro-hydraulic) winch drive motor assembly 38, 39 which is disposed on the movable winch support 50. The electrical energy required is supplied by generators disposed elsewhere on the vessel, at a 15 distance from the movable winch support 50. One or more sliding contacts (not shown) are provided in the electrical connection between these generators and the winch drive motor assemblies 38, 39.

In a variant which is not shown, the winch support 50 can rotate about a vertical shaft, 20 this shaft being provided with one or more sliding contacts.

Via the one or more sliding contacts, a power current supply is preferably fed to the electrical equipment on the winch support 50.

25 The hoisting crane 20 is provided with a cab 70 for a hoisting crane operator, which cab 70 is in this case carried by the annular bearing structure 25 to which the jib 24 is secured, so that the cab 70 can rotate with the jib about the vertical column 21.

In the cab 70 there are at least control members (not shown) for operating the traction 30 winch 35 of the hoisting cable 36 and for operating the winch 31 of the topping cable 31. The winch drive motor assemblies 38, 39 have associated control means 100 (see Figure 5) which are in wired or, preferably, wireless communication with the associated control members in the cab 70. By way of example, a plurality of wireless transmission/reception units are disposed around the vertical column, in or in the vicinity of the path of the cab 70 35 around the vertical column.

The control means, for example electronic control equipment, for the one or more winches on the winch support 50 are preferably also positioned on this winch support 50.

-8-

The vessel 1, in particular the hoisting device or crane 20, is further provided with a storage winch 72. The storage winch 72 comprises a reel 74 on which the cable 36 can be reeled. The storage winch 72 is preferably located in the hull of the vessel 1 and is secured to 5 a floor part 75 thereof. The cable 36 is guided along a rotatably mounted wheel 73 which is provided with a sensor for measuring the force that is exerted on the cable 36 during use of the crane 20. Such a sensor is for example a loadcell.

The vessel 1 can be used to lay a pipeline 9, but also for hoisting work, such as the 10 hoisting work carried out, for example, in the offshore industry when installing platforms, underwater installations, etc.

Figure 5 shows schematically the setup of the traction winch 35 and the storage winch 72. As can be seen, the cable 36 can be displaced by the traction winch 35 in two directions 15 indicated by double arrow 80, one direction corresponding to lowering the hook 37 and consequently a load, the other direction corresponding to raising the hook 37. Further the sensor or loadcell 73 for measuring the force exerted on the cable 36 is shown to contact the cable 36. The controller or control means 100 comprise a first input for receiving a first speed signal 101 representative of a speed of the cable 36 at the traction winch 35 and a second 20 input for receiving a second speed signal 102 representative of the rotational speed of the reel 74. The controller 100 additionally comprises a third input for receiving a force signal 103 representative of a measured force on the cable 36. Finally, the controller 100 comprises an output for providing an output signal 104 to control the speed of the reel 74, whereby the output signal 104 is provided to the associated electrical (or electro-hydraulic) storage winch 25 drive motor (not shown).

The control method the controller applies in order to control the hoisting device or crane 20 is as follows.

30 During operation of the crane 20, whereby a load is attached to the hook 37, the traction winch 35 displaces the cable 36 under control of the operator in the cab 70. The cable 36 will be displaced by the traction winch 35 with a certain speed. The rotational speed of the traction winch 35 is measured and is representative for the cable speed at the traction winch 35 and is represented by the first speed signal 101. The rotational speed of the reel 74 35 of the storage winch can also be measured and is represented by the second speed signal 102.

-9-

The nominal diameter D1 of the reel 74 has a fixed and known value and is present in the controller 100. Hence, as the ratio of the diameter of the traction winch 35 and the diameter of the reel 74 are known, it is possible to calculate the speed of the reel in case the cable 36 was located on that nominal diameter D1, this speed is the nominal diameter speed 5 of the reel 74. However, there will be cable 36 reeled on the reel 74 and consequently the reel 74 and the cable 36 reeled thereon have a joint diameter D2. By measuring the (actual) rotational speed of the reel 74 and dividing the nominal diameter speed by said measured reel speed, a value can be derived for the amount (or length) of cable that is reeled on the reel 74 and consequently a value is obtained for the actual joint diameter D2.

10

Having this value for the actual joint diameter D2, the required rotational speed of the reel 74 can now be calculated by the controller 100 and an output signal that is compensated for the calculated joint diameter D2 is sent to the motor driving the reel 74. The output signal 104 in fact represents a scaled feed forward signal of the speed of the cable 36 at the traction 15 winch 35. Scaling of this feed forward signal results in an improved behaviour of the hoisting device compared to a feed forward that is based on the non-scaled speed of the cable at the traction winch.

Hence, the requirement of maintaining a substantially constant tension on the 20 elongate body or cable 36 can be met by controlling the speed of the reel 74 on the basis of the speed of the cable 36 at the traction winch 35 and the joint diameter D2. In fact, the required speed of the reel does no longer need to be derived from the measured tension on the cable 36 by the loadcell 73. The speed of the cable 36 at the traction winch 35 represents a feed forward signal for the controller 100.

25

The loadcell 73 may still be used to provide the force signal 103 to the controller 100. This provides a redundancy in the control of the crane 20 and will always ensure that the tension in the cable 36 will be kept between predetermined values in case of failure.

30 It is noted that instead of calculating a nominal diameter speed that is related to the diameter D1 of the reel 74, it is also possible to calculate a nominal diameter speed that is related to the maximum joint diameter the reel 74 and the cable reeled thereon will have.

The controller 100 can be a computer in which a software program is loaded that 35 contains program instructions for executing the control method as described above.

As mentioned above, it is also possible to employ the hoisting device of the invention and in particular the control method of the invention to the field of laying pipelines. An - 10- example of a hoisting device for laying pipelines using the principle underlying the invention is shown in Figure 6.

Figure 6 shows nearly the same setup as Figure 5, in comparison therewith the 5 traction winch has been replaced by a tensioner 35A. The tensioner 35A has two friction belts 90 each contacting the pipe 36A. The friction belts 90 are driven by a drive motor (not shown). The device of Figure 6 does not comprise a sensor for measuring the force exerted on the pipe 36A, but it is to be understood that this is of course also possible.

10 It is noted that the above described hoisting device and the corresponding control method are beneficial when non-metallic material such as synthetic (super) fibres are used for the cable. Such materials are much smoother than metal cables and display a much larger elongation when subjected to a load. This means that a control strategy based on measuring the tension in the cable will be less effective and a control strategy based on the invention will 15 be able to maintain a constant tension much more effective.

Claims

A lifting device (20) for lifting an elongated body (36), the device comprising: 5. a traction device (35) for moving the elongated body; - a reel (74) for coiling the elongate body (36) thereon, wherein the reel (74) and the elongated body (36) reeled thereon have a common diameter (D2), and - a control unit (100) for studying the lifting device (20), characterized in that the control unit (100) comprises: - a first input for receiving a first speed signal (101) representative of a speed of the elongated body (36) at the lifting device (35); - a second input for receiving a second speed signal 15 (102) representative of a reel speed of the reel (74), and - an output for providing an output signal (104) for studying a speed of the reel , wherein the control unit is further adapted to: - calculate a nominal diameter speed of the reel (74) from the first speed signal (101); - to calculate the common diameter (D2) from the calculated nominal diameter speed and the second speed signal (102), and - to compensate the output signal (104) on the basis of the calculated common diameter (D2). 25

The lifting device of claim 1, wherein the control unit (100) further comprises a third input for receiving a force signal (103) representative of a measured force on the elongate body (36) and wherein the control unit (100) is arranged for compensating the output signal (104) based on the force signal (103).

The lifting device of claim 2, wherein the control unit (100) is adapted to compensate for the output signal (104) based on the force signal (103) such that the measured force is kept substantially constant. 2 0 0 1 6 5 6 35

A lifting device according to any one of the preceding claims, wherein the lifting device (20) further comprises a drive motor for driving the reel and wherein the control unit (100) is adapted to provide the output signal (104) to the drive motor. 5

Lifting device according to one of the preceding claims, wherein the traction device (35) is a traction winch.

6. Lifting device according to one of the preceding claims, wherein the reel (74) is part of a storage winch.

7. Method for studying a lifting device (20), the lifting device comprising a traction device (35) for moving the elongated body (36), a reel (74) for reeling the elongated body (36) thereon, wherein the reel (74) and the elongated body (36) reeled thereon have a common diameter (D2), characterized in that the method comprises: - measuring a speed of the elongated body (36) at the pulling device (35) ); 20. calculating a nominal diameter speed of the reel (74) from the measured speed of the elongated body (36); - measuring the reel speed of the reel (74); - calculating the common diameter (D2) from the calculated nominal diameter speed and the measured reel speed, and 25. calculating the reel speed from the measured speed of the elongated body (36) and the calculated common diameter (02).

The method of claim 7, further comprising measuring a force on the elongate body (36) and calculating the reel speed from the measured force.

The method of claim 7 or 8, further comprising controlling a drive motor adapted to drive the reel (74).

A software program comprising program instructions for performing the method according to any of claims 7 to 9 when loaded on a computer.

A driving device (1), such as a ship and the like, comprising a lifting device (20) according to one of the claims from 1 to 6. Λ A. λ * -