Frame for decanter centrifuge

Abstract

This invention relates to a frame for a decanter centrifuge. The frame includes two elongated box beams extending parallel to each other between a first end and a second end. Each box beam includes at least two ground supports at a third position and a fourth position, respectively. The third position is located near the first end, and the fourth position is located near the second end. Each box beam also includes: a C-beam defining two horizontal flanges and a vertical web interconnecting the two horizontal flanges; and a vertical plate, opposite to the vertical web, interconnecting the two horizontal flanges. A reinforcing plate extends longitudinally between the third and fourth ends. The third and fourth ends are located between the first and second ends.

Description

Technical Field

[0001] This invention relates to a frame for a decanter centrifuge, a decanter centrifuge, and a method for manufacturing a frame for a decanter centrifuge. Background Technology

[0002] A decanter centrifuge is a centrifuge that performs a centrifugal sedimentation process on a suspension of solid particles and liquid during operation. A decanter centrifuge comprises a cylinder rotatably mounted on a frame. During operation, the suspension forms an annular liquid layer along the inner wall of the cylinder under centrifugal force, where denser solid particles settle radially to the cylinder wall to form sludge, and the clarified liquid is discharged through the cylinder overflow port. The sediment is discharged mechanically (typically using an Archimedes screw conveyor).

[0003] The cylinder is typically horizontally supported on the frame by bearings on either side. Additionally, the drive motor, gearbox, and (if necessary) reverse drive motor are also mounted and supported by the frame. The rotating components of the decanter centrifuge (such as the cylinder) are surrounded by a protective cover and a shell for collecting the separated solids and liquids. The shell is typically an integral part of the frame. For ease of maintenance and installation of the decanter centrifuge, the cover is mounted separately on the frame.

[0004] To support the weight of the decanter centrifuge, the frame typically consists of elongated metal box beams, which in turn are supported on ground supports that connect to the foundation at the installation site. These ground supports typically take the form of four legs to provide stability.

[0005] Recently, there has been a growing demand for decanter centrifuges that allow suspensions to remain in the cylinder for longer periods. One way to achieve this is to make the cylinder of the decanter centrifuge larger and longer. Therefore, the frame supporting the cylinder must be longer. The frame must also be made stronger to support the increased weight of the larger cylinder.

[0006] During operation, the cylinder typically rotates at speeds of 2000-6000 rpm. When the cylinder rotates at such high speeds, vibrations will inevitably occur. These vibrations will be induced into the frame and must be absorbed by the frame without causing any resonance effect within it. Using higher cylinder speeds will induce higher frequencies into the frame. If the frequencies induced during operation cause resonance effects in the frame, it can lead to significantly stronger vibrations within the frame and potentially damage the frame. To avoid inducing resonance effects from the cylinder into the frame, the frame must have a natural frequency (or idiosyncratic frequency) significantly higher than the vibration frequencies induced into the frame by the cylinder's rotation.

[0007] The natural frequency of a frame depends on its bending stiffness and is inversely proportional to its mass. More specifically, the natural frequency increases with increasing bending stiffness and decreases with increasing mass. Making the frame longer in the longitudinal direction while keeping other dimensions constant will decrease the bending stiffness because the frame will require a longer box girder. It will also increase the mass because more material will be used to make the frame longer. Therefore, making the frame longer will significantly decrease its natural frequency. When the frame's natural frequency approaches that of the rotating cylinder, a resonance effect will occur.

[0008] To maintain the bending stiffness of the frame, it can be made more robust. One way to make the frame more robust using the existing dimensions of the box girders is to use stiffening plates attached to the box girders. The following prior art proposes stiffening plates: JP 7234489 describes a centrifuge having a frame with a hollow first frame member extending in a first direction, a hollow second frame member extending in a second direction, and a connecting portion connecting the first frame member to the second frame member. The connecting portion includes a first fixing portion fixed to an end portion of the first frame member and a second fixing portion fixed to an end portion of the second frame member. A reinforcing portion bridges between the first fixing portion and the second fixing portion and extends in a direction intersecting the first and second directions.

[0009] JP07071052 describes a screw conveyor having a reinforcing member fixed between a reinforcing ring and a shell.

[0010] KR200396783 describes a spiral dewatering machine having a reinforcing plate mounted in a semi-circular ring shape.

[0011] CN212861338 describes a vehicle energy absorption box with reinforcements.

[0012] Therefore, the objective of this invention is to provide a technique for increasing the length of the cylinder of a decanter centrifuge while preventing resonance in the frame. Summary of the Invention

[0013] According to a first aspect of the invention, the above objective is achieved by a frame for a decanter centrifuge, the frame defining a longitudinal direction, a vertical direction extending laterally relative to the longitudinal direction, and a transverse direction extending laterally relative to both the longitudinal and vertical directions, the frame comprising: Two elongated box beams extend parallel to each other in the longitudinal direction between their first and second ends. At least two connecting elements, extending in the lateral direction, interconnect the box girder at a first position in the longitudinal direction and a second position in the longitudinal direction, respectively. At least two ground supports extend vertically at a third position and a fourth position along the longitudinal direction, respectively, with the third position near the first end and the fourth position near the second end. Each box girder includes: A C-shaped beam, defining two horizontal flanges and a vertical web connecting the two horizontal flanges, the two horizontal flanges and the vertical web defining an internal passage between themselves, and A vertical plate, opposite to a vertical web, interconnects two horizontal flanges, wherein the vertical web and each of the two horizontal flanges includes a reinforcing plate attached to the internal passage of the C-beam, the reinforcing plate extending longitudinally between a third end and a fourth end, the third end and the fourth end being located longitudinally between a first end and a second end, such that the reinforcing plate extends only a portion of the distance between the first end and the second end.

[0014] The frame consists of two box beams extending longitudinally and at least two connecting elements between the two box beams in the transverse direction. The connecting elements can be used to support bearings for, for example, the rotating cylinder of a decanter centrifuge, the housing below the cylinder, the gearbox, and the motor. The box beams are made of metal and have an overall rectangular shape. The box beams are composed of vertical plates and C-beams.

[0015] C-beams are typically fabricated as elongated metal elements, shaped like a C, with two horizontal flanges and a vertical web that interconnects the two horizontal flanges edge-to-edge. Internal channels are thus formed between the vertical web and the two horizontal flanges. The C-beam is reinforced by stiffening plates attached to the web and the two horizontal flanges, facing the internal channels of the C-beam. In this way, the stiffening plates are not visible from the outside and therefore do not affect the appearance of the frame. The vertical plates are attached to the two horizontal flanges edge-to-edge, opposite to the vertical web, to form a rectangular and box-shaped beam. Therefore, the box beam is hollow.

[0016] Stiffening plates allow for longer box girder lengths while maintaining the frame's bending stiffness, thus preserving its natural frequency. However, adding stiffening plates makes the frame heavier. This is negative because it lowers the frame's natural frequency. Surprisingly, however, it has been found that stiffening plates do not necessarily have to extend the full length of the box girder (i.e., the full length between the first and second ends). To reduce the frame's weight, stiffening plates can extend only a portion of the distance between the first and second ends. In particular, stiffening plates can be attached between locations along the longitudinal direction of the box girder with higher bending stresses, while omitting locations along the longitudinal direction of the box girder with lower bending stresses.

[0017] Ground supports provide support to the box girder at third and fourth positions along the longitudinal direction. Each box girder is thus supported on the ground (i.e., a factory floor, etc.) by two ground supports extending downwards in the vertical direction and supporting the frame on the ground. The third position is located near the first end, and the fourth position is located near the second end. To understand this, it means that the third position is closer to the first end in the longitudinal direction than the center point of the frame, and the fourth position is closer to the second end in the longitudinal direction than the center point of the frame.

[0018] Near the first and second edges (i.e., close to the ground supports), the bending stress will be low, while near the longitudinal center point of the box girder (i.e., far from the ground supports), the bending stress will be high. To reduce the weight of the frame, the reinforcing plate can therefore only extend a portion of the distance between the first and second ends without significantly reducing the bending stress, because the bending stress near the first and second ends is low. In this way, the increase in the mass of the frame will be smaller, allowing for a higher natural frequency of the frame.

[0019] According to another embodiment of the first aspect, the C-beam is manufactured as a unitary element. In this way, there will be no joints in the C-beam, allowing it to be more rigid and easier to manufacture. The C-beam can be made, for example, by pressing, casting, or molding.

[0020] According to another embodiment of the first aspect, the box girder is made of a metal such as cast iron or carbon steel. Metals such as cast iron or carbon steel are typically used for box girder due to increased stiffness and reduced maintenance requirements.

[0021] According to another embodiment of the first aspect, the reinforcing plate is attached by spot welding, and the reinforcing plate is provided with holes for spot welding. In this way, the reinforcing plate is securely fastened to the C-beam, increasing bending stiffness.

[0022] According to another embodiment of the first aspect, the reinforcing plates are attached by fillet welds, and the reinforcing plates define a gap between themselves for the fillet welds. By filling the gap between the reinforcing plates with fillet welds, the bending stiffness can be increased.

[0023] According to another embodiment of the first aspect, the length between the first end and the second end is at least 20% longer than the distance between the third end and the fourth end, preferably 30% longer, and more preferably 40% longer. By making the reinforcing plate shorter, the weight can be reduced without necessarily increasing the bending stress.

[0024] According to another embodiment of the first aspect, the reinforcing plates are substantially centered between the first and second ends. Therefore, the reinforcing plates are placed where they have the greatest effect, and this location is close to the center where the bending stress is highest.

[0025] According to another embodiment of the first aspect, the distance between the first end and the second end is 5-10 meters, preferably 6-9 meters, and the distance between the third end and the fourth end is 2-5 meters, preferably 3-4 meters. The standard decanter centrifuge is at most 5 meters long. The length of the decanter centrifuge can be increased by including the length of the frame and reinforcing plates.

[0026] According to another embodiment of the first aspect, the third position is located between the first end and the third end, and the fourth position is located between the second end and the fourth end. Because the bending stress at the ground support is very low, the reinforcing plate does not need to extend beyond the third and fourth positions respectively (when the third and fourth positions are the locations of the ground support).

[0027] According to another embodiment of the first aspect, the first and second ground supports are made as box-shaped legs, which are attached to one of the corresponding elongated box beams. Preferably, the frame is supported by four legs extending from the box beams to the ground. The legs may be made hollow, similar to the box beams.

[0028] According to a second aspect of the invention, at least one of the two connecting elements interconnects the first ends of the parallel box beams, and at least the other of the two connecting elements interconnects the second ends of the parallel box beams. Interconnecting the ends of the parallel box beams further improves the bending stiffness of the frame.

[0029] According to a second aspect of the invention, the above objective is achieved by a decanter centrifuge comprising a decanter cylinder mounted on a frame according to the first aspect.

[0030] According to a third aspect of the invention, the above objective is achieved by a method of producing a frame for a decanter centrifuge, the frame defining a longitudinal direction, a vertical direction extending laterally relative to the longitudinal and transverse directions, and a transverse direction extending laterally relative to the longitudinal and vertical directions, the method comprising the steps of: Two C-beams are provided, extending parallel to each other in the longitudinal direction between a first end and a second end. Each C-beam defines two horizontal flanges and a vertical web that interconnects the two horizontal flanges. The two horizontal flanges and the vertical web define an internal channel between themselves. The reinforcing plate is attached to the internal channel of the C-beam, extending longitudinally between the third and fourth ends, which are located longitudinally between the first and second ends, such that the reinforcing plate extends only a portion of the distance between the first and second ends. In contrast to the vertical web, the vertical plate and two horizontal flanges are interconnected, thereby producing two elongated box beams that extend parallel to each other in the longitudinal direction between the first and second ends. The box girder is interconnected by at least two connecting elements extending in the transverse direction at a first position in the longitudinal direction and a second position in the longitudinal direction, respectively. At least two ground supports are attached to each box girder, the ground supports extending vertically at a third position in the longitudinal direction and a fourth position in the longitudinal direction, the third position being near the first end and the fourth position being near the second end.

[0031] The method according to the third aspect can be used to produce according to the framework of the first aspect. Attached Figure Description

[0032] Figure 1 This is a perspective view of a decanter centrifuge according to the present invention.

[0033] Figure 2 This is a cross-sectional perspective view of the frame according to the present invention.

[0034] Figure 3 This is a perspective view of a box girder according to the present invention.

[0035] Figure 4A This is a perspective view of the C-shaped beam according to the present invention.

[0036] Figure 4B This is a perspective view of the reinforcing plate according to the present invention.

[0037] Figure 4C This is a perspective view of a spot weld according to the present invention.

[0038] Figure 4D This is a perspective view of a fillet weld according to the present invention. Detailed Implementation

[0039] Figure 1 This is a perspective view of a decanter centrifuge 10 according to the present invention. The decanter centrifuge 10 includes a frame 12 and a cover 14 mounted on the frame 12. The decanter centrifuge 10 includes a rotating member (not visible) rotatably mounted on the frame 12 below the cover 14. The frame 12 includes two box beams 16 extending parallel to each other in the longitudinal direction L between a first end 22a and a second end 22b. The frame 12 also includes at least two connecting elements 18 for connecting the box beams 16 at a first position 24a and a second position 24b in the longitudinal direction L.

[0040] In this embodiment, the first position 24a and the second position 24b are the same as the first end 22a and the second end 22b, respectively; however, this is not necessarily the case. The frame 12 also includes four ground supports 20, which are in the form of legs extending downward from the box beam 16 in the vertical direction V, for supporting the decanter centrifuge 10 on the ground (not shown). The ground (not shown) may be a factory floor, etc.

[0041] The vertical direction V is transverse relative to their longitudinal direction L. Ground support 20 is connected to the box girder at third position 24c and fourth position 24d. Third position 24c is located between the first end 22a and the center point C between the first end 22a and the second end 22b, and fourth position 24d is located between the second end 22b and the center point C. Drive motor 26 and reverse drive motor 28 are supported by frame 12.

[0042] Figure 2 This is a sectional perspective view of the frame 12 according to the invention. A reinforcing plate 30 is located within the box girder 16. The reinforcing plate 30 extends at a third end 22c and a fourth end 22d. The third end 22c is located between a third position 24c and the center point C, while the fourth end 22d is located between a fourth position and the center point C. Furthermore, the third position 24c is located between the first end 22a and the third end 22c, and the fourth position 24d is located between the second end 22b and the fourth end 22d.

[0043] The reinforcing plate 30 adds bending stiffness to the box girder 16 to increase the natural frequency of the frame 12. The reinforcing plate 30 does not extend all the way to the first end 22a and the second end 22b because the added weight would lower the natural frequency, and the bending stiffness would not be increased by adding plates near the first end 22a and the second end 22b. In this way, the frame 12 can be made longer, and therefore the rotating member (i.e., the cylinder, not shown) can also be made longer.

[0044] Other connecting elements 18 are typically located between the box beams 16 for mounting bearings (not shown) of the rotating components and / or the housing (not visible) below the rotating components, etc.

[0045] Figure 3 This is a perspective view of a box girder 16 according to the present invention. The box girder 16 includes a C-shaped beam 32 and a vertical plate 34. The C-shaped beam includes a first horizontal flange 32a, a second horizontal flange 32b, and a vertical web 32c. The vertical web 32c interconnects the first horizontal flange 32a and the second horizontal flange 32b at opposite edges. The vertical plate 34 interconnects the first horizontal flange 32a and the second horizontal flange 32b with the vertical web 32c at an edge-to-edge manner, thereby forming an internal channel 36 between the first horizontal flange 32a, the second horizontal flange 32b, the vertical web 32c, and the vertical plate 34.

[0046] The reinforcing plate 30 includes: a first reinforcing plate 30a attached to a first horizontal flange 32a; a second reinforcing plate 30b attached to a second horizontal flange 32b; and a third reinforcing plate 30c attached to a vertical web 32c. The reinforcing plates 30 are attached to the internal passage 36 of the box girder 16 and are therefore not visible from the outside.

[0047] Figure 4A This is a perspective view of the C-beam 32 according to the invention. The C-beam 32 is typically made of a metal such as cast iron or carbon steel. It is typically manufactured as a single piece, i.e., as an integral element, and typically extends the entire length of the frame.

[0048] Figure 4B This is a perspective view of the reinforcing plate 30 being mounted into the C-beam 32 according to the present invention. The first reinforcing plate 30a, the second reinforcing plate 30b, and the third reinforcing plate 30c are typically made as three separate pieces. In this embodiment, the first reinforcing plate 30a, the second reinforcing plate 30b, and the third reinforcing plate 30c are made to have substantially the same dimensions as the first horizontal flange 32a, the second horizontal flange 32b, and the vertical web 32c, respectively; however, this is not necessarily the case, as they can also be smaller, provided that the reinforcing plate 30 fits into the internal channel 36. However, the reinforcing plate 30 does not extend the full length of the C-beam 32. The reinforcing plate 30 is typically attached before the attached vertical plate (not shown).

[0049] Figure 4C This is a perspective view of the spot weld between the reinforcing plate 30 and the C-beam 32 according to the invention. The reinforcing plate 30 is typically provided with orifices 38 for spot welding the reinforcing plate 30 to the C-beam 32. In this way, the reinforcing plate 30 is securely attached to the C-beam 32, and the reinforcing plate 30 is thus able to increase the bending stiffness of the C-beam 32.

[0050] Figure 4D This is a perspective view of the fillet welds between the reinforcing plates 30 according to the present invention. It is possible to interconnect the reinforcing plates 30 by fillet welds 40 between the first reinforcing plate 30a and the third reinforcing plate 30c and between the second reinforcing plate 30b and the third reinforcing plate 30c.

Claims

1. A frame for a decanter centrifuge, the frame defining a longitudinal direction, a vertical direction extending laterally relative to the longitudinal direction, and a transverse direction extending laterally relative to both the longitudinal and vertical directions, the frame comprising: Two elongated box beams, the two elongated box beams extending parallel to each other in the longitudinal direction between a first end and a second end. At least two connecting elements extend in the lateral direction and interconnect the box beams at a first position and a second position in the longitudinal direction, respectively. At least two ground supports extend from each of the elongated box girder in the vertical direction at a third position along the longitudinal direction and a fourth position along the longitudinal direction, respectively, the third position being near the first end and the fourth position being near the second end. Each box girder includes: A C-shaped beam, the C-shaped beam defining two horizontal flanges and a vertical web connecting the two horizontal flanges, the two horizontal flanges and the vertical web defining an internal channel between themselves, and A vertical plate, opposite to the vertical web, interconnects the two horizontal flanges, wherein the vertical web and the two horizontal flanges each include a reinforcing plate attached to the internal channel of the C-beam, the reinforcing plate extending in the longitudinal direction between a third end and a fourth end, the third end and the fourth end being located in the longitudinal direction between the first end and the second end, such that the reinforcing plate extends only a portion of the distance between the first end and the second end.

2. The framework according to claim 1, wherein, The C-shaped beam is manufactured as a single integrated component.

3. The framework according to any one of the preceding claims, wherein, The box girder is made of metal such as cast iron or carbon steel.

4. The framework according to any one of the preceding claims, wherein, The reinforcing plate is attached by spot welding, and the reinforcing plate is provided with holes for spot welding.

5. The framework according to any one of the preceding claims, wherein, The reinforcing plates are attached by fillet welds, and the reinforcing plates define a gap in the middle of themselves for the fillet welds.

6. The framework according to any one of the preceding claims, wherein, The reinforcing plate has a thickness of 50%-150% of the thickness of the C-beam, such as being approximately the same as the thickness of the C-beam.

7. The framework according to claim 6, wherein, The vertical plate has a thickness of 150%-250% of the thickness of the C-beam, such as approximately twice the thickness of the C-beam.

8. The framework according to any one of the preceding claims, wherein, The length between the first end and the second end is at least 20% longer than the distance between the third end and the fourth end, preferably 30% longer, and more preferably 40% longer.

9. The framework according to any one of the preceding claims, wherein, The reinforcing plate is substantially centered between the first end and the second end.

10. The framework according to any one of the preceding claims, wherein, The distance between the first end and the second end is 5-10 meters, preferably 6-9 meters, and the distance between the third end and the fourth end is 2-5 meters, preferably 3-4 meters.

11. The framework according to any one of the preceding claims, wherein, The third position is located between the first end and the third end, and the fourth position is located between the second end and the fourth end.

12. The framework according to any one of the preceding claims, wherein, At least one of the two connecting elements interconnects the first ends of the parallel box beam, and at least the other of the two connecting elements interconnects the second ends of the parallel box beam.

13. The framework according to any one of the preceding claims, wherein, The first and second ground supports are made into box-shaped legs, which are attached to one of the corresponding elongated box beams.

14. A decanter centrifuge comprising a decanter cylinder mounted on a frame according to any one of the preceding claims.

15. A method of producing a frame for a decanter centrifuge, the frame defining a longitudinal direction, a vertical direction extending laterally relative to the longitudinal direction, and a transverse direction extending laterally relative to both the longitudinal and vertical directions, the method comprising the steps of: Two C-beams are provided, extending parallel to each other in the longitudinal direction between a first end and a second end. Each C-beam defines two horizontal flanges and a vertical web that interconnects the two horizontal flanges. The two horizontal flanges and the vertical web define an internal channel between themselves. The reinforcing plate is attached to the internal channel of the C-beam, extending in the longitudinal direction between a third and a fourth end, the third and fourth ends being located in the longitudinal direction between the first and second ends, such that the reinforcing plate extends only a portion of the distance between the first and second ends. In contrast to the vertical web, the vertical plate and the two horizontal flanges are interconnected to produce two elongated box beams that extend parallel to each other in the longitudinal direction between the first and second ends. The box girder is interconnected by at least two connecting elements extending in the transverse direction at a first position and a second position in the longitudinal direction, respectively. At least two ground supports are attached to each box girder, the ground supports extending in the vertical direction at a third position along the longitudinal direction and at a fourth position along the longitudinal direction, the third position being near the first end and the fourth position being near the second end.

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