Protective element and decanter centrifuge

Abstract

The invention relates to a protective element (1) for arrangement on the outer circumference of a screw thread (2) of a screw (3), in particular a conveying screw or a compression screw, comprising a wear element (5) that is abraded during operation of the screw (3), wherein the protective element (1) comprises at least one magnetic element (6), in particular a permanent magnet, wherein the magnetic element (6) is arranged in such a way that it is abraded during operation of the screw (3), and is preferably abraded only when a part of the wear element (5) has already been abraded.

Description

[0001] Protective element and decanter centrifuge

[0002] The invention relates to a protective element and a decanter centrifuge.

[0003] Decanter centrifuges are known devices in the art used for separating solids and liquids. They operate continuously and are particularly suitable for processing suspensions with high solids content.

[0004] Decanter centrifuges typically consist of a rotating drum within a housing, which has a cylindrical-conical shape. A screw, also rotating, is located inside this drum. A solid-liquid mixture is introduced into the drum. The screw, with its helical thread, transports the settled solids to the conical end of the drum, where they are discharged.

[0005] The process of separating and transporting solids places considerable stress on the screw thread of the decanter centrifuge. Therefore, wear elements, such as hard metal or ceramic plates (so-called "tiles"), are typically attached to the outer circumference of the screw thread to protect it. Since these wear elements wear down over time, they must be regularly inspected or replaced. However, this is a complex and costly process, as the entire centrifuge must be disassembled to check the condition of the wear elements and replace them manually if necessary. Furthermore, each individual wear element must be inspected before replacement.

[0006] Therefore, a detection system or sensor device is of great interest either to monitor the condition of the wear protection elements and / or to select the right time for shutdown and maintenance of a decanter centrifuge.

[0007] The object of the present invention is to overcome the problems of the prior art, at least partially or completely. A further object of the invention is to provide a reliable method for detecting the wear state of a wear element. An object of the invention may also be to improve or optimize maintenance intervals and to increase the service life of a machine.

[0008] These and other tasks are solved by a protective element according to claim 1.

[0009] Within the scope of the invention, it was discovered that these and other problems can be solved by a protective element comprising a magnetic element, particularly in combination with a magnetic field sensor arranged on the housing of a decanter centrifuge, which detects the magnetic field of the magnetic element. When the magnetic element is worn down by the operation of the decanter centrifuge, its emitted magnetic field changes. This change can be detected. Additionally, the magnetic element can be at least partially surrounded by a shielding element. When the shielding element is worn away, the magnetic element can be exposed, or the magnetic element is unshielded, thereby allowing its magnetic field to be detected. According to the invention, a protective element is provided for arrangement on the outer circumference of a screw thread of a screw, in particular a conveying screw or a compression screw.The protective element can be designed as a protective tile, a weld overlay, powder coating, or in another form on the screw thread. The protective element includes a wear element that is worn down during screw operation.

[0010] The protective element further comprises at least one magnetic element. The magnetic element is arranged such that it is worn down during operation of the screw, and preferably only when part of the wear element has already been worn away.

[0011] The magnetic element can be located, in particular, in the wear element.

[0012] The magnetic element can be a permanent magnet. Several magnetic elements, preferably particulate or powder-shaped, can be provided, optionally arranged unevenly within the protective element, particularly within the wear element.

[0013] The magnetic element can be, for example, a neodymium magnet (NdFeB) or a samarium-cobalt magnet (SmCo). Preferably, the magnetization direction of the magnetic element can be axial.

[0014] The magnetic element can be designed as a single magnet or as a stack of magnets, with non-magnetic protective layers optionally provided between the stack layers. The material properties of the magnetic element, in particular the maximum operating temperature (Curie temperature) and, if applicable, the use of a coating such as Ni-Cu-Ni, Ni-Cu-Ni-Cr, Cr-Cu-Ni-Cr, or the like, are preferably tailored to the specific process conditions.

[0015] It may be provided that the protective element includes a support element designed for attachment to a continuous outer edge of the worm gear. The wear element may be arranged on the support element. The wear element may preferably project at least partially beyond the support element. The wear element may have a higher hardness than the support element.

[0016] The magnetic element can, for example, be cuboid or cylindrical. The magnetic element can optionally be arranged on or arranged on the support element, or be inserted or insertable into the support element.

[0017] The term "partially projecting" can mean, among other things, that the wear element projects beyond the support element at least along a longitudinal dimension, along a transverse dimension or along both dimensions, so that a kind of cantilever is formed.

[0018] The wear element is designed to have a higher hardness than the support element. In particular, the wear element comprises a different material or materials than the support element.

[0019] A shielding element can be provided to shield the magnetic field generated by the magnetic element, wherein the shielding element is arranged in such a way that it is worn away in front of the magnetic element during operation of the screw, so that it loses at least part of its shielding effect, and preferably is only worn away when part of the wear element has already been worn away.

[0020] It may be provided that the shielding element is arranged as a shielding layer on the protective element in such a way that it is rubbed off in front of the wear element with the magnetic elements during operation, so that it loses at least some of its shielding effect.

[0021] The shielding element can also be shaped, for example, cuboid, trapezoidal, or cylindrical. This can prevent or reduce wear on the magnetic element, thus avoiding or delaying the need to replace the expensive magnetic element. For example, a shielding element can be replaced after it has worn down, so that the magnetic element itself does not need to be replaced.

[0022] The worn-out wear element can also be replaced with a new wear element on the support element, if necessary.

[0023] The shielding element can be designed to at least partially, preferably completely, surround the magnetic element, or to be flush with an end face of the magnetic element. For example, the shielding element can be flush with a side face of the magnetic element in such a way that the shielding element is at least partially worn away before the magnetic element is exposed and worn away.

[0024] It can be provided that the support element is essentially cuboid in shape with a longitudinal extent L and a transverse extent Q, with the wear element projecting beyond the support element in the direction of the transverse extent Q.

[0025] It may be provided that the magnetic element and / or the shielding element extends beyond the support element in the direction of the longitudinal extension L.

[0026] It may be provided that the support element has a recess for positive locking on the circumferential outer edge of the worm thread, essentially opposite the wear element.

[0027] It may be provided that the shielding element comprises a soft magnetic material, in particular soft iron.

[0028] The wear element may comprise or consist of a non-magnetic hard material, in particular carbide, tungsten carbide, or ceramic. The support element may comprise or consist of steel, in particular stainless steel, or titanium.

[0029] It can be provided that the magnetic element is inserted into a recess of the support element and preferably glued in place.

[0030] In one embodiment of the invention, the wear element can preferably be glued, welded, or screwed onto the support element. In another embodiment of the invention, the shielding element can be inserted into a recess of the support element and preferably glued in place.

[0031] It may also be provided that the wear element is at least partially directly adjacent to the magnetic element, the shielding element, or both elements.

[0032] The invention further comprises a decanter centrifuge, optionally comprising a stationary housing, a drum rotatable in the housing about an axis of rotation R, and a screw with a circumferential screw thread rotatable in the drum about the axis of rotation R. Furthermore, a decanter centrifuge according to the invention comprises at least one radially outwardly directed protective element according to the invention, arranged on the outer edge of the screw thread, in particular glued or welded on, wherein the protective element is, for example, provided in the form of a protective tile.

[0033] The housing may optionally comprise non-ferromagnetic steel. The radially outward-facing protective element may be arranged such that it does not contact the inner wall.

[0034] The housing may be equipped with at least one magnetic field sensor configured to measure the magnetic field emitted by the magnetic element of the guard during the rotation of the worm gear relative to the housing. The drum may comprise or consist of non-magnetic material or a low-permeability material. For example, the drum may comprise or be formed of duplex steel. Preferably, the magnetic field sensor is arranged on the inside of the housing, thus positioned between the drum and the housing. Alternatively, the magnetic field sensor may be arranged on the outside of the housing.

[0035] A magnetic element is preferably dimensioned such that the generated magnetic field bridges the distance to the magnetic field sensor. Preferably, the magnetic element is dimensioned such that its magnetic field can still be detected by the magnetic field sensor even with increasing wear.

[0036] Furthermore, it may be provided that the at least one magnetic field sensor is designed to measure the magnetic field emitted by the magnetic element of the protective element during the rotation of the worm gear and the drum relative to the housing, wherein the worm gear and the drum may optionally rotate at different speeds.

[0037] It may be provided that two or more protective elements are arranged offset on the worm gear in such a way that the magnetic fields of the magnetic elements do not overlap. The associated magnetic field sensors can be arranged offset from each other on the housing in such a way that each magnetic field sensor can detect the magnetic field of one magnetic element.

[0038] This allows wear on the protective elements to be detected at different points along the screw's thread. This enables timely maintenance of the screw.

[0039] The protective elements may be arranged at essentially identical rotational angular positions and linearly offset parallel to the axis of rotation R, with two or more associated magnetic field sensors arranged linearly offset from each other along the longitudinal extent of the housing. The magnetic field sensor may be configured as a Hall sensor, GMR sensor, AMR sensor, TMR sensor, or flux-gate sensor.

[0040] It may be provided that at least two magnetic field sensors are arranged in an electrically connected manner.

[0041] It may be provided that conventional protective elements, in particular glued or welded radially outwardly directed, are arranged on the outer edge of the worm thread and are not designed according to a protective element according to the invention. Such conventional protective elements may also include a wear element, but not a magnetic element. The conventional and the protective elements according to the invention may substantially completely encompass the outer edge of the worm thread. The conventional protective elements may have the same dimensions as the protective elements according to the invention.

[0042] Further features of the invention will become apparent from the claims, the description of the exemplary embodiments, and the figures. The invention is explained below with reference to figures which show exemplary embodiments:

[0043] Fig. 1a shows a schematic cross-sectional view of part of a decanter centrifuge along its axis of rotation R.

[0044] Fig. 1b shows a schematic cross-sectional view AA of a decanter centrifuge normal to its axis of rotation R.

[0045] Fig. 2a shows a schematic cross-sectional view of a protective element on a worm gear.

[0046] Fig. 2b shows schematically how the magnetic field changes when the protective element of Fig. 2a is worn away.

[0047] Fig. 3 shows a schematic cross-sectional view of a protective element on a worm gear.

[0048] Fig. 4a shows a schematic cross-sectional view of a protective element on a worm gear. Fig. 4b schematically shows how the magnetic field changes when the protective element of Fig. 4a wears down.

[0049] Fig. 5 shows a schematic cross-sectional view of a protective element on a worm gear.

[0050] Fig. 6 shows a schematic cross-sectional view of a protective element on a worm gear.

[0051] Fig. 1a shows a schematic cross-sectional view of part of an exemplary decanter centrifuge 9. Fig. 1b shows the sectional view AA of the decanter centrifuge 9. The decanter centrifuge 9 has a cylindrical-conical shape and comprises a housing 10 in which a drum 11 and a screw 3 are arranged around an axis of rotation R. The drum 11 and the screw 3 are designed to rotate in the same direction and, at least partially during operation, to be operated at different rotational speeds. An air gap is provided between the drum 11 and the housing 10.

[0052] The screw 3 comprises a screw thread 2, which has a conventional thread pitch and does not extend radially outwards to the inner wall of the drum 11. A plurality of protective elements 1 are arranged radially outwards around the outer circumference of the screw thread 2. The protective elements 1 are arranged with a recess 8 at the outer edge of the screw thread 2. The protective elements 1 are connected to the screw thread 2, for example by gluing, welding, or similar means.

[0053] In this embodiment, the protective elements 1 comprise a support element 4, a magnetic element 6, a wear element 5, and optionally a shielding element 7. The protective elements 1 are arranged along the axis of rotation R of the decanter centrifuge 9 on the screw thread 2 such that the magnetic fields of the magnetic elements 6 do not overlap. In particular, the protective elements 1 can be arranged along the axis of rotation R such that the magnetic fields of the protective elements 1 do not overlap perpendicular to the axis of rotation R. Optionally, one protective element 1 can be arranged for each thread pitch or for each half thread pitch of the screw thread 2. Conventional protective elements T are arranged between the protective elements 1 along the entire outer edge of the screw thread 2, as schematically illustrated by the dashed line in Fig. 1b.Conventional protective elements T comprise a support element 4 and a wear element 5, but no magnetic element 6. Preferably, the protective elements T have the same external dimensions as the protective elements 1.

[0054] The protective elements 1, 1' are arranged on the screw thread 2 such that they essentially do not contact the inner wall of the drum 11 of the decanter centrifuge 9. In particular, the wear element 5 of the protective elements 1, 1' does not contact the inner wall of the drum 11.

[0055] At least one magnetic field sensor 12 is arranged on the housing 10 of the decanter centrifuge 9. The magnetic field sensor can be arranged on the outside of the housing, as in this embodiment, but also on the inside of the housing. A magnetic field sensor 12 is designed such that it can detect the magnetic field of a magnetic element 6 of a protective element 1 on the worm gear 2 when this element passes the position of the magnetic field sensor 12 during operation.

[0056] The magnetic field sensors 12 are further arranged such that each magnetic field sensor 12 detects the magnetic field of a single, associated magnetic element 6. In this embodiment, one magnetic field sensor 12 is thus arranged on the housing 10 for each protective element 1. The magnetic field sensors 12 can be arranged angularly offset around the circumference of the housing 10. Alternatively, several magnetic field sensors 12 can be arranged linearly offset from one another along the longitudinal extent of the housing 10.

[0057] The magnetic field sensors 12 are configured as Hall sensors, GMR sensors, AMR sensors, TMR sensors, or flux-gate sensors. The magnetic field sensors 12 can be electrically interconnected or configured as separate units. The general operating principle of the invention is described with reference to the exemplary decanter centrifuge 9 of Figures 1a and 1b.

[0058] During operation of a decanter centrifuge 9, a liquid-solid mixture is fed into the drum 11. The drum 11 and screw 3 rotate at varying speeds between 1000 and 5000 rpm during operation. The solids are forced outwards and moved by the screw 3 towards the solids outlet at the tapered end of the drum 11. The liquids are transported towards the opposite, cylindrical end, towards the liquid outlet. This process separates the solids and the liquid.

[0059] During operation, the protective elements 1, 1' on the worm gear 2 are subjected to high stress and wear down over time. In an advantageous embodiment of the protective element 5, the wear element 5 of the protective elements 1 is worn down first. At a certain point, the wear element 5 is worn down to such an extent that the magnetic element 6 or the shielding element 7, and subsequently the magnetic element 6, are also worn down.

[0060] As soon as the magnetic element 6 is worn or exposed, its magnetic field changes. The magnetic field sensor 12 on the housing 10 of the decanter centrifuge 9 detects this change in the magnetic field. The measurement data can be evaluated, in particular, by a data processing device connected to the magnetic field sensor 12. By detecting the change in the magnetic field, maintenance of the decanter centrifuge 9 can be initiated in a timely manner. In particular, this prevents damage to the screw thread 2 by replacing the protective element 1, T in a timely manner.

[0061] The general operating principle can be implemented, among other things, with protective elements according to the embodiments shown in Fig. 2-6.

[0062] Embodiments of the protective element 1 are described in Figures 2a to 5. Figure 2a shows a schematic cross-sectional view of a protective element 1 on a worm gear 2. In this embodiment, the protective element 1 is designed as a protective tile. Figure 2b schematically shows in a diagram how the magnetic field of the magnetic element 6 changes when the protective element 1 of Figure 2a wears down. The protective element 1 is attached to the outer edge of the worm gear 2.

[0063] The protective element 1 comprises a support element 4 designed for attachment to the outer edge of the worm thread 2. In this embodiment, the support element 4 has a recess 8 designed to be positively engaged with the outer edge of the worm thread 2. A wear element 5 is arranged on the support element 4, the wear element 5 projecting at least partially beyond the support element 4.

[0064] In this embodiment, the support element 4 is essentially cuboid in shape with a longitudinal dimension L and a transverse dimension Q. The wear element 5 projects beyond the support element 4 in the direction of the transverse dimension Q. The wear element 5 is arranged on the support element 4 such that it is worn down first during operation of the decanter centrifuge 9.

[0065] The support element 4 comprises or consists of steel, in particular stainless steel, or titanium. The wear element 5 has a higher hardness than the support element 4. The wear element 5 comprises or consists of a non-magnetic hard material, in particular carbide, tungsten carbide, or ceramic.

[0066] The protective element 1 of Fig. 2a comprises a magnetic element 6, which is designed as a permanent magnet. The magnetic element 6 is essentially cuboid and is bonded into the support element 4. Several magnetic elements 6 can also be arranged side by side in a protective element 1. The magnetic element 6 is inserted into the support element 4 in such a way that it is only worn down during operation of the decanter centrifuge 9 once part of the wear element 5 has already been worn away. Fig. 2b shows how the magnetic field of the magnetic element 6 of Fig. 2a changes with increasing wear. The field amplitude B (mT) decreases linearly with wear. This change can be detected by a magnetic field sensor 12, which is mounted on the decanter centrifuge 9.

[0067] Figure 3 shows a schematic cross-sectional view of a protective element 1 on a worm gear 2. In this embodiment, the protective element 1 is designed as a protective tile. The protective element 1 is arranged at the outer edge of the worm gear 2. The protective element 1 includes a support element 4, which is designed for attachment to the outer edge of the worm gear 2.

[0068] In this embodiment, the support element 4 has a recess 8 which is designed to be positively engaged with the outer edge of the worm thread 2.

[0069] A wear element 5 is arranged on the support element 4, projecting at least partially beyond it. In this embodiment, the support element 4 is essentially cuboid in shape with a longitudinal dimension L and a transverse dimension Q. The wear element 5 projects beyond the support element 4 in the direction of the transverse dimension Q. The wear element 5 is arranged on the support element 4 such that it is worn down first during operation of the decanter centrifuge 9.

[0070] The support element 4 comprises or consists of steel, in particular stainless steel, or titanium. The wear element 5 has a higher hardness than the support element 4. The wear element 5 comprises or consists of a non-magnetic hard material, in particular carbide, tungsten carbide, or ceramic.

[0071] The protective element 1 of Fig. 3 comprises a magnetic element 6, which is designed as a permanent magnet. The magnetic element 6 is inserted into the support element 4. It may be glued into the support element 4. Furthermore, the magnetic element 6 may be cylindrical or cuboidal. Several magnetic elements 6 may be arranged side by side in a protective element 1. The magnetic element 6 is inserted into the support element 4 in such a way that, during operation of the decanter centrifuge 9, it is only worn down when part of the wear element 5 has already been worn away.

[0072] The protective element 1 of this embodiment further comprises a shielding element 7 for shielding the magnetic field generated by the magnetic element 6. The shielding element 7 is arranged such that, during operation of the decanter centrifuge 9, it is only worn down once a portion of the wear element 5 has already been worn away. As wear progresses, the shielding element 7 loses its shielding effect. In this embodiment, the shielding element 7 is inserted into the support element 4. The shielding element 7 is placed onto the magnetic element 6, so that the magnetic element 6 is flush with one end face of the magnetic element 6.

[0073] The shielding element 7 is arranged such that, during operation of the decanter centrifuge 9, the shielding element 7 is at least partially worn away before the magnetic element 6 is worn away. The shielding element 7 can comprise a soft magnetic material, for example, soft iron.

[0074] During operation of the decanter centrifuge 9, the wear element 5 and then the shielding element 7 are worn away as wear increases. As long as the shielding element 7 at least partially covers the magnetic element 6, the magnetic field sensor 12 cannot detect any or only a weak magnetic field from the magnetic element 6. As soon as the magnetic element 6 is exposed, its magnetic field can be detected by the magnetic field sensor 12.

[0075] Fig. 4a shows a schematic cross-sectional view of a protective element 1 on a worm gear 2. Except for the magnetic element 6 and the shielding element 7, the protective element 1 is designed like the protective element 1 of Fig. 3. In this embodiment, the magnetic element 6 is enclosed by the shielding element 7 on at least four sides. The shielding element 7 is inserted into the support element 4. The shielding element 7 may be glued in place. Fig. 4b shows an exemplary diagram illustrating how the magnetic field changes when the protective element 1 of Fig. 4a wears down. During operation of the decanter centrifuge 9, with increasing wear, first the wear element 5 and then the shielding element 7 are worn away. As long as the shielding element 7 covers the magnetic element 6, the magnetic field sensor 12 cannot detect any or only a very weak magnetic field from the magnetic element 6.

[0076] As soon as the magnetic element 6 is partially exposed, its magnetic field can be detected by the magnetic field sensor 12. This sharp increase in the field amplitude B (mT) after the magnetic element 6 has been exposed is clearly visible in the diagram in Fig. 4b.

[0077] Fig. 5 shows a schematic cross-sectional view of a protective element 1 on a worm gear 2. The protective element 1 is designed like the protective element 1 of Fig. 2a. Only the magnetic element 6 is not inserted into the support element 4, but is arranged on the outside of the support element 4. The magnetic element 6 can be glued to the support element 4. The wear element 5 is arranged directly on the magnetic element 6 and on the support element 4. The wear element 5 can be glued to the magnetic element 6 and to the support element 4.

[0078] A typical wear pattern of the protective element 1 during operation of the decanter centrifuge 9 is shown schematically by the dashed lines, which show how the wear element is at least partially worn down first, before the magnetic element 6 is worn down.

[0079] Fig. 6 shows a schematic cross-sectional view of a protective element 1 on a worm gear 2. In this embodiment, the protective element 1 is arranged directly on the worm gear 2. The protective element 1 comprises a non-magnetic hard material as a wear element 5, for example, a carbide or ceramic. In this embodiment, particulate or powdered magnetic elements 6 are distributed throughout the wear element 5. The magnetic elements 6 are shown schematically in Fig. 6. Preferably, the magnetic elements 6 are distributed homogeneously within the wear element 5.

[0080] It is also possible for the protective element 1 to be applied to the worm gear 2 as a weld overlay or as powder coating. The magnetic elements 6 can also be distributed within the weld overlay or powder coating.

[0081] Furthermore, a shielding element 7 can be provided on the protective element 1 of the embodiment shown in Fig. 6. The shielding element 7 can be arranged as a shielding layer on the protective element 1 in such a way that it is worn away in front of the wear element 5 during operation, so that it partially loses its shielding effect.

[0082] The invention is not limited to the described embodiments, but includes all devices and methods within the scope of the following patent claims.

[0083] Reference symbol list

[0084] 1, 1 ' Protective element

[0085] 2 worm gears

[0086] 3 snail

[0087] 4 support element

[0088] 5.5' Wear element

[0089] 6 Magnetic Elements

[0090] 7 Shielding element

[0091] 8 Exclusion

[0092] 9 Decanter centrifuge

[0093] 10 cases

[0094] 11 Drum

[0095] 12 Magnetic field sensor

Claims

Patent claims 1. Protective element (1) for arrangement on the outer circumference of a screw thread (2) of a screw (3), in particular a conveying screw or a compression screw, comprising a wear element (5) which is worn down during operation of the screw (3), characterized in that - the protective element (1) comprises at least one magnetic element (6), in particular a permanent magnet - wherein the magnetic element (6) is arranged such that it is worn down during operation of the screw (3), and preferably only when part of the wear element (5) has already been worn down.

2. Protective element (1) according to claim 1, characterized in that the magnetic element (6) is arranged in the wear element (5).

3. Protective element (1) according to claim 1 or 2, characterized in that several, preferably particulate or powder-shaped magnetic elements (6) are provided which are optionally arranged unevenly distributed in the protective element (1), in particular in the wear element (5).

4. Protective element (1) according to one of claims 1 to 3, characterized in that - a support element (4) designed for attachment to a continuous outer edge of the worm thread (2) is provided, - wherein the wear element (5) is arranged on the support element (4) and preferably extends at least partially beyond the support element (4), and - wherein the wear element (5) has a higher hardness than the support element (4).

5. Protective element (1) according to one of claims 1 to 4, characterized in that a shielding element (7) is provided for shielding the magnetic field generated by the magnetic element (6), wherein the shielding element (7) is arranged such that it is worn down in front of the magnetic element (6) during operation of the screw (3), so that it loses at least part of its shielding effect, and preferably is worn down only when part of the wear element (5) has already been worn down.

6. Protective element (1 ) according to claim 5, characterized in that the shielding element (7) surrounds the magnetic element (6) at least partially, preferably completely, or is arranged flush with an end face of the magnetic element (6).

7. Protective element (1) according to one of claims 4 to 6, characterized in that the support element (4) is essentially cuboid in shape with a longitudinal extent L and a transverse extent Q, wherein the wear element (5) projects beyond the support element (4) in the direction of the transverse extent Q.

8. Protective element (1) according to claim 7, characterized in that the magnetic element (6) and / or the shielding element (7) projects beyond the support element (4) in the direction of the longitudinal extent L.

9. Protective element (1 ) according to claim 7 or 8, characterized in that the support element (4) preferably has a recess (8) on one side substantially opposite the wear element (5) for a positive locking arrangement on the circumferential outer edge of the worm thread (2).

10. Protective element (1 ) according to one of claims 5 to 9, characterized in that the shielding element (7) comprises a soft magnetic material, in particular soft iron.

11. Protective element (1) according to one of claims 1 to 10, characterized in that the wear element (5) comprises or consists of a non-magnetic hard material, in particular carbide, tungsten carbide or ceramic.

12. Protective element according to one of claims 4 to 11, characterized in that the support element (4) comprises or consists of steel, in particular stainless steel, or titanium.

13. Protective element (1 ) according to one of claims 4 to 12, characterized in that the magnetic element (6) is inserted into a recess of the support element (4) and preferably glued in place.

14. Decanter centrifuge (9) comprising: - a fixed housing (10), - a drum (11) rotatable in the housing (10) about a rotational axis R , - a screw (3) rotatable in the drum (11) about the axis of rotation R with a circumferential screw thread (2), characterized in that at least one radially outwardly directed protective element (1) according to one of claims 1 to 13, for example in the form of a protective tile, a weld overlay or a powder coating, is provided, arranged on the outer edge of the screw thread (2), in particular glued or welded on.

15. Decanter centrifuge (9) according to claim 14, characterized in that at least one magnetic field sensor (12) is provided on the housing (10), which is designed to measure the magnetic field emitted by the magnetic element (6) of the protective element (1) during the rotation of the screw thread (2) relative to the housing (10).

16. Decanter centrifuge (9) according to claim 14 or 15, characterized in that a. on the screw thread (2) two or more protective elements (1) are arranged offset from each other such that the magnetic fields of the magnetic elements (6) do not overlap, and wherein b. two or more magnetic field sensors (12) are arranged on the housing (10) offset from each other such that each magnetic field of a magnetic element (6) can be detected by each magnetic field sensor (12).

17. Decanter centrifuge (9) according to claim 14 or 15, characterized in that a. the protective elements (1) are on substantially identical rotation angle positions and are arranged offset from each other on a line running substantially parallel to the axis of rotation R, and wherein b. two or more magnetic field sensors (12) assigned to the protective elements (1 ) are arranged linearly offset from each other on the housing (10) along the longitudinal extent of the housing (10).

18. Decanter centrifuge (9) according to one of claims 14 to 17, characterized in that the magnetic field sensor (12) is designed as a Hall sensor, GMR sensor, AMR sensor, TMR sensor or as a flux-gate sensor.

19. Decanter centrifuge (9) according to one of claims 14 to 18, characterized in that a. conventional protective elements (1 ') arranged on the outer edge of the screw thread (2), in particular glued or welded, radially outwardly directed, are provided which are not designed according to one of claims 1 to 12, wherein b. the conventional protective elements (1 ') comprise a wear element (5'), and wherein c. the protective elements (1 , 1 ') substantially completely encompass the outer edge of the screw thread (2).

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