Lifting System

Abstract

1. A lifting system for a metallurgical plant, comprising an object (10) including one or more trunnions (15, 15') and a lifting device including one or more lifting hooks (20, 20') for receiving the trunnions, further comprising a detection system, the detection system comprising a receiver unit (4), a sensor unit (2, 2'), a magnet (1, 1') and a transmitter unit (3), the magnet and the sensor unit being aligned upon correct alignment of the at least one lifting hook with the at least one trunnion, so that a signal is presented to the receiver unit.

Description

Technical Field

[0001] The present invention relates to a lifting system for a metallurgical plant. The present invention further relates to a detection system.

Background Art

[0002] Lifting systems are an essential part of metallurgical plants. In the basic oxygen furnace (BOF) process, the lifting and transportation of the ladle may occur hundreds of times. During this discontinuous process, the hot metal undergoes pretreatment, primary metallurgy treatment, secondary metallurgy treatment, and is cast. All of these steps require the lifting and transportation of the hot metal in the ladle by a crane. Additionally, the scrap chute is also handled by the crane. For the safety and continuity of steelmaking, it is very important that the crane and the ladle are properly aligned during lifting and transportation. The crane operator must ensure that the hook of the crane is properly positioned around the spout of the ladle before lifting. Some major accidents have occurred in the steel industry as a result of inaccurately aligned lifting systems.

[0003] To reduce misalignment and human errors leading to tragedies, a detection system for the correct alignment of the crane and the ladle is desired. Due to the harsh conditions in a BOF plant, including high temperatures and a dusty environment, the robustness of the detection system is of great importance.

[0004] German Patent No. 102013017803 B4 discloses a misalignment system for a crane having two hooks connected via a crossbeam designed to receive components, a misreading system which is a magnetic flux introduction device, a magnetic flux detection device, and an electronic device connectable to the magnetic flux detection device for detecting the magnetic flux detected in the magnetic flux detection device.

[0005] The device of German Patent No. 102013017803B4 is a complex device that requires a plurality of components. This device requires a wired connection between the object to be lifted and the crane. Furthermore, it is unclear which side of the object is misaligned in the prior art device.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, it is desirable to provide a lifting device that can detect the alignment between the crane and the object to be lifted without requiring a complex wired connection.

[0007] Therefore, an object of the present invention is to provide a lifting device equipped with a robust detection system.

Means for Solving the Problems

[0008] This object is solved by the subject matter of the independent claims. Advantageous embodiments are provided in the dependent claims and the description.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] In a first aspect of the present invention, there is provided a lifting system for a metallurgical plant, comprising an object having one or more transions and a lifting device having one or more lifting hooks for receiving the transions, the lifting system further comprising a detection system, the detection system comprising a receiver unit, a sensor unit, a magnet and a transmitter unit, the magnet and the sensor unit being aligned when the lifting hook and the transion are correctly aligned, as a result of which a signal is presented to the receiver unit.

[0011] Advantageously, the detection system is configured such that the sensor unit detects a change in the magnetic field resulting from the correct alignment of the object and the lifting device. By placing the sensor unit inside the hook and a magnet on the object, or vice versa, the magnet and the sensor unit are aligned when the trunnion and the lifting hook are correctly engaged. The sensor unit detects the change in the magnetic field and typically triggers a transmitter unit to send a signal to a receiver unit arranged within a crane control system so that the control system knows that the hook is properly engaged. Thus, the detection system provides the control unit with information, such as a Boolean true false result that can be easily interpreted by the control unit. This can result in a warning in the human machine interface (HMI) for the operator or can be used directly to disable the lifting in a dangerous situation.

[0012] Accordingly, the present invention provides a lifting device having a robust and simple detection system. The object is not particularly limited and may be any container that needs to be lifted, such as a ladle or a scrap chute. The lifting device is typically an overhead traveling crane.

[0013] The magnet, the sensor unit, and the transmitter unit are not particularly limited, but preferably should be able to withstand harsh conditions commonly found in metallurgical plants, such as high temperatures, dusty environments, and shock impacts. The sensor unit may comprise a Hall effect sensor or a reed switch. Preferably, the sensor unit and the transmitter unit are battery-operated so that the system does not require a power cable.

[0014] In one embodiment of the present invention, the magnet is a permanent magnet so as to create its own permanent magnetic field. This is preferable because no current is required to operate the magnet.

[0015] Both the strength of the magnet and the sensitivity of the sensor unit determine the distance at which a signal will be presented. In one embodiment according to the present invention, the magnet has a residual magnetism of at least 3000 gauss. At a residual magnetism of at least 3000 gauss, the sensor unit can be operated at a minimum distance of 0 mm and a maximum distance of 500 mm, and is deactivated when the magnet and the sensor unit are misaligned by more than 100 mm. In this range, there is sufficient space to attach the sensor unit and the transmitter unit to the hook while maintaining a good threshold for the sensor unit and attach the magnet to the object.

[0016] In one embodiment according to the present invention, the distance between the magnet and the sensor unit during correct alignment is at most 200 mm. At distances exceeding 200 mm, the size and / or the residual magnetism of the magnet would need to be increased, which would make the installation of the magnet more difficult and result in a less accurate system.

[0017] In one embodiment according to the present invention, the threshold for the presentation of a signal to the receiver unit is at least 3 millitesla. Since the magnet, the sensor unit and the transmitter unit need to be arranged closer due to the position where the hook and the trunion engage, below 3 millitesla, their attachment to the object and the lifting device becomes less practical. Furthermore, this increases the impact load shown on the detection system, which may cause damage to the system.

[0018] The configuration of the elements of the detection system is not particularly limited. Preferably, the magnet is arranged on the outer side surface of the object. This ensures that the magnet does not come into direct contact with the substances inside the object. Preferably, the magnet is arranged adjacent to the trunion of the object, because this position is close to the interaction point between the trunion and the hook.

[0019] When handling hot metal, the outer side surface of the ladle may reach a temperature of up to 200 °C, and the hook may reach a temperature of up to 70 °C. Therefore, preferably the magnet is arranged on the object, and preferably the sensor unit and the transmitter unit are arranged on the hook. This is because the magnet can withstand higher temperatures compared to the sensor unit and the transmitter unit.

[0020] In a preferred embodiment, the sensor unit is arranged on the inner side surface of the hook, and the transmitter unit is arranged on the outer side surface of the hook. The inner side surface of the hook is defined as the side surface of the hook closest to the object. The transmitter unit and the sensor unit can be coupled via a cable passing through a conduit in the hook to transmit signals. Since the transmitter unit is generally more sensitive than the sensor unit, the transmitter unit is preferably installed on the outer side surface of the hook, which has a lower operating temperature and less impact effect, and thus improves the durability of the detection system.

[0021] In a preferred embodiment, the lifting system includes a sensor unit, a transmitter unit, and a magnet for each trunion / hook pair. In this way, no visual inspection from the operator is required to confirm the correct engagement between the hook and the trunion.

[0022] In a preferred embodiment, each sensor unit includes at least one Hall sensor. The Hall sensor may be a unipolar one that provides additional flexibility for attaching the magnet to the object. Furthermore, the Hall sensor can achieve high sensitivity and can be used at an operating temperature of up to 150 °C.

[0023] In a preferred embodiment, each sensor unit comprises at least two sensors, the transmitter unit comprises at least two transmitters, and the receiver unit comprises at least two receivers. In both the transmitter unit and the receiver unit, signals are compared. If a signal is received by only one of the transmitter and / or receiver, the system can provide a warning. By using such an arrangement, the detection system is fail-safe and makes the system very robust.

[0024] In one embodiment, the transmitter unit and the receiver unit are wirelessly connected. Preferably, the signal is presented via radio waves, such as WLAN, so that no cable between the transmitter unit and the receiver unit is required.

[0025] In a further embodiment, the detection system also comprises an object weighing unit. The weighing unit can detect whether the object is in an empty state or a filled state. In such a configuration, the HMI receives not only standard information regarding the movement of the lifting device, but also information regarding the weight of the object and information regarding the alignment of the lifting hook with the object. Thus, the HMI can provide an overall picture of the ongoing operation in the factory.

[0026] In another aspect of the present invention, a detection system for a lifting system comprising a magnet, a sensor unit, a transmitter unit and a receiver unit is provided. Such a system can be installed in an existing lifting system as an after-market solution. The magnet, the sensor unit and the transmitter unit are not particularly limited, but preferably should be able to withstand harsh conditions often found in metallurgical factories, such as high temperatures, dusty environments and impact effects. The sensor unit can comprise a Hall effect sensor or a reed switch. Preferably, the sensor unit and the transmitter unit operate on batteries so that the system does not require a power cable.

[0027] In one embodiment of the present invention, the magnet is a permanent magnet so as to create its own permanent magnetic field. This is preferable because no current is required to operate the magnet.

[0028] Both the strength of the magnet and the sensitivity of the sensor unit determine the distance at which a signal will be presented. In one embodiment according to the present invention, the magnet has a residual magnetism of at least 3000 gauss. At a residual magnetism of at least 3000 gauss, the sensor unit can be operated at a minimum distance of 0 mm and a maximum distance of 500 mm, and is deactivated when the magnet and the sensor are misaligned by more than 100 mm. Within this range, there is sufficient space to attach the sensor unit and the transmitter unit to the hook while maintaining a good threshold for the sensor unit and to attach the magnet to the object.

[0029] In one embodiment according to the present invention, the distance between the magnet and the sensor unit in the correct alignment is at most 200 mm. At distances exceeding 200 mm, the size and / or the residual magnetism of the magnet would need to be increased, which would make the installation of the magnet more difficult and result in a less accurate system.

[0030] In one embodiment according to the present invention, the threshold for the presentation of the signal to the receiver unit is at least 2 millitesla. Since the magnet, the sensor unit and the transmitter unit need to be arranged closer to the position where the hook and the trunion engage, 2 below millitesla, their attachment to those objects and the lifting device becomes less practical. Further, this increases the impact load shown on the detection system, which may result in damage to the system.

[0031] In a preferred embodiment, each sensor unit comprises at least two sensors, the transmitter unit comprises at least two transmitters, and the receiver unit comprises at least two receivers. In both the transmitter and the receiver, signals are compared. If a signal is received only by one of the transmitter and / or the receiver, the system is enabled to provide a warning. By using such an arrangement, the detection system is fail-safe and makes the system very robust.

[0032] In one embodiment, the transmitter unit and the receiver unit are wirelessly connected. Preferably, the signal is presented via radio waves, such as wlan, so that no cable between the transmitter unit and the receiver unit is required.

[0033] In a further embodiment, the detection system also comprises an object metering unit. The metering unit can detect whether the object is in an empty or filled state and can be used to signal a safety situation where the hook and the trunion are not aligned.

[0034] The present invention is further illustrated by the non-limiting example shown in FIG. 1.

[0035] Figure 1A shows an object 10 which is a hot metal mixer (partially shown) with two trunnions 15, 15'. Adjacent to the trunnions, permanent magnets 1, 1' (not shown) are attached. Each magnet is a ferrite magnet with a residual magnetism of 4000 gauss and has a size of 150×100×50 mm. Sensor units 2, 2' are attached to the inner side surfaces of each hook 20, 20'. The sensor unit has a unipolar Hall sensor, and the unipolar Hall sensor operates at a distance of 0 to 178 mm and is deactivated at a distance farther than 428 mm or a positional deviation of 100 mm. The threshold value of the sensor unit is 3 millitesla. A transmitter unit with a microprocessor is attached to the outer side surface of the hook. The transmitter unit and the sensor unit are connected by a cable and are charged by a battery. In Figure 1B, the hook and the trunnion are in the correct alignment that provides a positive wireless feedback signal from the transmitter unit to the receiver unit 4. In Figure 1C, the hook and the trunnion are not correctly aligned, and if the system starts to lift, a dangerous situation may occur. However, due to the incomplete alignment between the hook and the trunnion, the magnet does not set the sensor unit and falls below the threshold value. Therefore, a positive feedback signal is not presented to the receiver unit, and a warning message is displayed on the HMI.

Claims

A lifting system for a metallurgical plant, comprising an object having a pair of trunnions and a lifting device having a pair of lifting hooks for receiving the pair of trunnions, wherein the lifting system further comprises a detection system, the detection system comprising a receiver unit, a sensor unit, a permanent magnet and a transmitter unit, the permanent magnet and the sensor unit being aligned when the at least one lifting hook and one trunnion are correctly aligned, as a result of which a signal is presented to the receiver unit, each lifting hook comprising the sensor unit and the transmitter unit, the object comprising the permanent magnet for each trunnion, a lifting system.

2. The lifting system according to claim 1, wherein the object is a hot metal ladle.

3. The lifting system according to claim 1 or 2, wherein the permanent magnet has a residual magnetism of at least 3000 gauss.

4. The lifting system according to any one of claims 1 to 3, wherein the permanent magnet is attached to the outer side surface of the object.

5. The lifting system according to any one of claims 1 to 4, wherein the object comprises the permanent magnet adjacent to each trunnion.

6. The lifting system according to any one of claims 1 to 5, wherein the distance between the permanent magnet and the sensor unit during correct alignment is at most 200 mm.

7. The lifting system according to any one of claims 1 to 6, wherein the threshold value of the sensor unit is at least 2 millitesla.

8. The lifting system according to any one of claims 1 to 7, wherein the sensor unit is arranged inside the hook.

9. The lifting system according to any one of claims 1 to 8, wherein the transmitter unit is arranged outside the hook.

10. The lifting system according to any one of claims 1 to 9, wherein the transmitter unit and the receiver unit are wirelessly connected.

11. The lifting system according to any one of claims 1 to 10, further comprising an object weighing unit.

12. The lifting system according to any one of claims 1 to 11, wherein each sensor unit comprises at least one Hall sensor.

13. A detection system for a lifting system comprising the permanent magnet, sensor unit, transmitter unit, and receiver unit according to any one of claims 1 to 12.

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