Patent Application
20240139754
This application claims priority to German patent application no. 102022211338.1 filed on Oct. 26, 2022, the contents of which are fully incorporated herein by reference.
The present invention is directed to bearings, and more particularly to bearing arrangements for grinding mills and methods for determining fill rates of grindings mills.
Generally, to assess or determine the fill rate of a drum of a horizontal grinding mill, the power generated by a motor driving the drum is monitored as there is a general correlation between the power needed to rotate the drum and the weight of the drum. However, this correlation is not linear, and when the fill rate of the drum reaches higher or greater filling levels, the motor power decreases leaving the operator in a “blind spot” in which the operator does not know if the fill rate of the drum is actually decreasing or the amount of material within the drum is too great.
These methods for estimating of the fill rate of the drum are not sufficiently accurate, such that the drum is loaded within a safety margin in order to avoid an overfilling of the drum. An overfilling of a drum may result in an unplanned and undesired shut down of the grinding process, resulting in production losses.
Further, the fill rate of the drum has a direct influence on product quality, process efficiency and process control. As the environment inside the drum is typically harsh or corrosive, there is generally no practical capability of positioning a sensor within the drum in order to directly measure the fill rate of the drum. Additionally, as the drum is typically rotating, the use of wired sensors is generally difficult.
An object of the present invention is to provide a method and apparatus for accurately determining the fill rate of a drum of a horizontal grinding mill.
According to one aspect, a method for determining the fill rate of drum of a horizontal grinding mill, which includes a first bearing device and a second bearing device supporting the drum in rotation, is proposed. This method comprises:
The method enables the accurate estimation of the fill rate of the drum in real time without analyzing the power generated by a motor driving the drum, allowing for a more accurate estimation of the fill rate inside the drum.
Preferably, the method further comprises determining a load applied on the second bearing device, the first relationship correlating the fill rate of the drum to the determined load applied on the first bearing device and to the determined load applied on the second bearing device.
Preferably, the method further comprises determining the first relationship during the training/calibration period, the determination of the first relationship comprising:
Preferably, each bearing device comprises a bearing, which is provided with an inner ring and with an outer ring capable of rotating concentrically relative to one another, and a fiber optic sensor comprising an array of optical strain gauges mounted on the inner or outer ring of the bearing. Also preferably, the step of determining the load applied on each bearing device comprises:
Preferably, the first relationship is a regression model.
According to another aspect, a bearing arrangement of a horizontal grinding mill, the grinding mill including a drum, is proposed. The bearing arrangement comprises a first bearing device and a second bearing device, the drum being supported in rotation by the first and second bearing devices.
The bearing arrangement of the horizontal grinding mill further comprises:
Preferably, the load determining means or “load determiner” are/is further configured to determine the load applied on the second bearing device, and the first relationship links the fill rate of the drum to the determined load applied on the first bearing device and to the determined load applied on the second bearing device. Once again, the first relationship is a preferably a regression model.
Preferably, each bearing device includes a bearing provided with an inner ring and with an outer ring capable of rotating concentrically relative to one another, and a fiber optic sensor comprising an array of optical strain gauges mounted on the inner or outer ring of the bearing, and the load determining means/load determiner comprise: measuring means, or a measuring device, configured to measure the deformations of the inner or outer ring of each bearing from the array of optical strain gauges, and second determining means, or a second load determiner, configured to determine the load acting on each bearing from the deformations of the inner or outer ring of each bearing and a predetermined second relationship between the deformations and the loads. Preferably, the measuring means or measuring device comprise an optical interrogator connected to at least one fiber optic sensor.
Other advantages and features of the invention will appear on examination of the detailed description of embodiments, in no way restrictive, and the appended drawings in which:
Reference is made to
The first bearing device 5 and the second bearing device 6 may be identical or may be formed differently (e.g., one signal row and the other double row, one including balls and the other rollers, etc.). Each bearing device 5, 6 includes a roller bearing 8, 9 provided with an inner ring 10, 11 mounted on the shaft 4 and an outer ring 12, 13 mounted into the bore of the housing 2. Each outer ring 12, 13 radially surrounds the inner ring 10, 11. Either the inner rings 10, 11 and/or the outer rings 12, 13 rotate concentrically relative to each other.
Each roller bearing 8, 9 is further provided with a row of rolling elements 14, 15, respectively, radially interposed between inner and outer raceways of the inner rings 10, 11 and the outer rings 12, 13. In the illustrated example, the rolling elements 14, 15 are balls. Alternatively, the roller bearings 8, 9 may include any other appropriate types of rolling elements 14, 15, for example cylindrical rollers, tapered rollers, needles, etc. In the illustrated example, the roller bearings 8, 9 each include only a single row of rolling elements 14, 15. Alternatively, the roller bearing comprises several rows of rolling elements. Alternatively, the bearing 8, 9 may not include any rolling elements; in other words, the bearing 8, 9 may be plain bearings.
An annular groove 16, 17 is formed in the outer surface of each one of the outer rings 12, 13 of each roller bearing 8, 9. Each groove 16, 17 is oriented radially outwardly so as to radially face the bore of the housing 2.
An optical fiber 18, 19 is housed into or disposed within the groove 16, 17 of the outer ring 12, 13 of each roller bearing 8, 9. Each optical fiber 18, 19 is connected to a monitoring device 20. In the illustrated example, the optical fibers 18, 19 are mounted on the outer rings 12, 13 of the roller bearings 8, 9 as described above. However, the optical fibers 18, 19 may each alternatively be mounted on the inner rings 10, 11 of the roller bearings 8, 9 or one fiber 18 or 19 may be mounted in the outer ring 12, 13 and the other fiber 19, 18 may be mounted in the inner ring 11, 10.
As the first and second bearing devices 5, 6 are preferably identical,
The optical fiber 19 preferably comprises optical strain gauges 23, 24, 25, 26 mounted into the groove 17 of the outer ring 13. In the illustrated example, the optical fiber 19 comprises the four optical strain gauges 23, 24, 25, 26. In other variants, the optical fiber 19 may comprise less or more than four optical strain gauges.
Each optical strain gauge 23, 24, 25, 26 includes a different set of refraction gratings, for example a set of Bragg refraction gratings. When the optical strain gauges 23, 24, 25, 26 are illuminated by an optical signal, for example emitted by a laser, each set of refraction gratings reflects a part of the optical signal. Each reflected signal by the optical strain gauges 23, 24, 25, 26 has a different wavelength so that the reflected signal emitted by each optical strain gauges 23, 24, 25, 26 may be identified.
When a load is applied on the bearing 9, the optical fiber 19 is stretched or compressed so that the reflected wavelength changes. The optical fiber 18 of the first bearing device 5 comprises a first array of optical strain gauges (not depicted, but preferably identical to strain gauges 23, 24, 25, 26) and the optical fiber 19 of the second bearing device 6 comprises a second array of strain gauges comprising the optical strain gauges 23, 24, 25, 26.
The bearing arrangement of the horizontal grinding mill further comprises a monitoring device 20 which includes both load determining means 27, or a load determiner 27, and fill rate determining means 28, or a fill rate determiner 28. The fill rate determining means 28 are intended to determine the fill rate of the drum 3 and include a first memory 31 storing a first predetermined relationship REL1 between the fill rate of the drum 3, the load applied on the first bearing device 5, and the load applied on the second bearing device 6. The first predetermined relationship REL1 is determined during a training or calibration period outside of normal production operations of the grinding mill 1.
The load determining means/load determiner 27 are/is intended to determine the load applied on the first bearing device 5 and on the second bearing device 6. The load determining means 27 comprise measuring means or a measuring device provided with a first optical interrogator 29 connected to the optical fiber 18 of the first bearing device 5 in order to measure the deformations of the outer ring 12 of the roller bearing 8 by use of the optical strain gauges.
The measuring means/measuring device preferably further comprises a second optical interrogator 30 connected to the optical fiber 19 of the second bearing device 6 to measure the deformations of the outer ring 13 of the roller bearing 9 from the optical strain gauges 23, 24, 25, 26. Each one of the first and second optical interrogators 29, 30 includes an optical signal transmitter (not represented), for example a laser, and an optical receiver (not represented).
The load determining means 27 further comprise second determining means 32 and a second memory 33 storing a predetermined second relationship REL2 between the deformations measured by the interrogators 29, 30 and the loads on the bearings 5, 6. In one variant, the second memory 33 is located outside the load determining means 27.
The monitoring device 20 comprises a processing unit 35 implementing the load determining means 27 and the fill rate determining means 28.
The determination of the first relationship REL1 is explained as follows.
Further, the load applied on the first bearing device 5 and the load applied on the second bearing device 6 are each determined by the determining means 27.
The first optical interrogator 29 measures the deformations of the outer ring 12 of the first bearing 8 from the first array of optical strain gauges (not shown) and the second optical interrogator 30 measure the deformations of the outer ring 13 of the second bearing 6 from the second array of optical strain gauges 23, 24, 25, 26.
The second determining means 32 determine a measured load acting on the first bearing 8 from the deformations of the outer ring 12 of the first bearing 8 measured by the first interrogator 29 and the second predetermined relations ship REL2. Further, the second determining means 32 determine a measured load acting on the second bearing 9 from the deformations of the outer ring 13 of the second bearing 9 measured by the second interrogator 30 and the second predetermined relationship REL2.
During step 43, the measured loads acting on the first and second bearings 8, 9 and the measured fill rate of the drum 3 are stored in a memory (not represented).
Steps 40, 41, 42, 43 are repeated a plurality of times with different known quantities of material. When steps 40, 41, 42, 43 are repeated the plurality of times, during a step 44, the first predetermined relationship REL1 is determined from each data couple including the measured fill rate of the drum 3 and the associated measured loads acting on the bearings 8, 9 implementing, for example, a regression model.
In another embodiment, the first predetermined relationship REL1 is determined by simulations, calculation or theoretical relations during the training/calibration period.
During a step 45, the motor 7 drives the filled drum 3. During a step 46, while the motor 7 drives the drum 3, the drum 3 is continuously fed in one end with the material to be ground, and from the other end, the ground material is discharged.
The first optical interrogator 29 measures the deformations of the outer ring 12 of the first bearing 8 from the first array of optical strain gauges (not depicted) and the second optical interrogator 30 measures the deformations of the outer ring 13 of the second bearing 9 from the second array of optical strain gauges 23, 24, 25, 26.
The second determining means 32 determine the load acting on the first bearing 8 and the load acting on the second bearing 9. The fill rate determining means 28 determine the fill rate of the drum 3 in real time from the first predetermined relationship REL1, the determined load applied on the first bearing device 5 and the determined load applied on the second bearing device 6 determined by the second determining means 32. The fill rate of the drum 3 is continuously determined or calculated.
In another embodiment, the fill rate of the drum 3 is determined from the load applied on one of the first and second bearing devices 5, 6, the first predetermined relationship REL1 being between the fill rate of the drum 3 and the load applied on the one of the first and second bearing devices 5. 6.
The monitoring device 20 permits accurate estimation of the fill rate of the drum 3 in real time without analyzing the power generated by the motor 7, allowing for a more accurate estimation of the fill rate inside the drum 3.
Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention.
Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.
All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter. The invention is not restricted to the above-described embodiments, and may be varied within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022211338.1 | Oct 2022 | DE | national |
