Pump assembly with a vertical pump arranged in a canister

Abstract

A pump assembly includes a vertical pump arranged in a canister. The vertical pump includes a pump column disposed between a pump head and a pump bowl in an axial direction. The pump is arranged in the pump column and is configured to pump a fluid a column inlet at the pump bowl to a column outlet at the pump head. The pump column is supported so as to be stabilized by at least two damping arms disposed on an outer surface of the pump column, and each damping arm has an support end to support a respective damping arm on an inner surface of the canister in a radial direction perpendicular to the axial direction. Each support end is movable independently from each other support end with respect to the axial direction.

Claims

1. A pump assembly comprising: a vertical pump arranged in a canister, the vertical pump comprising a pump column disposed between a pump head and a pump bowl in an axial direction, a pump device being arranged in the pump column and configured to pump a fluid from a column inlet at the pump bowl to a column outlet at the pump head, and a vibration damper comprising a holder and at least two damping arms disposed so as to support and stabilize the pump column, each damping arm of the at least two damping arms has a support end to support a respective damping arm on an inner surface of the canister in a radial direction perpendicular to the axial direction, the holder mounted around the pump column and having a shape corresponding to a shape of the pump column, each damping arm of the at least two damping arms mounted to the holder, the holder comprising a first retainer and a second retainer, the first retainer and the second retainer being mounted around the pump column, each damping arm of the at least two damping arms connected to the first retainer and to the second retainer and orientated along the axial direction with the support end extending towards the pump head such that each support end is disposed above the first retainer and the second retainer with respect to the axial direction, and each support end being movable independently from each other support end with respect to the axial direction.

2. The pump assembly in accordance with claim 1, wherein the pump column and each of the damping arms defines a respective angle that is 10° to 80°.

3. The pump assembly in accordance with claim 2, wherein the holder comprises a first half shell and a second half shell, the first half shell and the second half shell being connectable by a fastener.

4. The pump assembly according to claim 2, wherein the holder is one of a plurality of vibration dampers, and each vibration damper of the plurality of vibration dampers being arranged at a different position in the axial direction.

5. The pump assembly in accordance with claim 1, wherein the holder comprises a first half shell and a second half shell, the first half shell and the second half shell being connectable by a fastener.

6. The pump assembly according to claim 5, wherein the holder is one of a plurality of vibration dampers, and each vibration damper of the plurality of vibration dampers being arranged at a different position in the axial direction.

7. The pump assembly according to claim 1, wherein the holder is one of a plurality of vibration dampers, and each vibration damper of the plurality of vibration dampers being arranged at a different position in the axial direction.

8. The pump assembly in accordance with claim 1, wherein each support end comprises a flattened edge, the flattened edge facing towards the inner surface of the canister.

9. The pump assembly in accordance with claim 1, wherein the at least two damping arms includes at least three damping arms disposed on the outer surface of the pump column.

10. The pump assembly in accordance with claim 1, wherein the damping arms are equidistantly distributed around an outer circumference of the pump column.

11. The pump assembly in accordance with claim 1, wherein the pump column and each of the damping arms defines a respective angle that is 30° to 80°.

12. The pump assembly in accordance with claim 1, wherein the pump column and each of the damping arms defines a respective angle that is 30° to 60°.

13. The pump assembly in accordance with claim 1, wherein the at least two damping arms includes four to eight damping arms disposed on the outer surface of the pump column.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in more detail hereinafter with reference to the drawings.

(2) FIG. 1 is a bow centralizer as already known in the state of the art,

(3) FIG. 2 is a schematic representation of an embodiment of a vertical pump according to the invention,

(4) FIG. 3 is a mechanical vibration mode shape of a pump column, which can also be approximated as operational vibration due to an excitation of a natural frequency,

(5) FIG. 4 is a perspective view of a first embodiment of a vibration damper according to the invention,

(6) FIG. 5 is a cross-sectional view of a variant of the first embodiment of the vibration damper shown in FIG. 4, and

(7) FIG. 6 is a representation of the vibration damper of FIG. 5 arranged on a pump column.

DETAILED DESCRIPTION

(8) FIG. 1 shows a schematic illustration of the state of the art, which has already been described above. As already mentioned above, the reference signs of FIG. 1 contain an apostrophe (or prime), since they refer to the state of the art.

(9) FIG. 2 shows a schematic representation of an embodiment of a pump assembly according to the invention which is designated in its entirety with reference numeral 1. The pump assembly 1 comprises a vertical pump 100 arranged in a canister 6. The basic structure of the vertical pump 100 as such is known from the prior art. However, the general description given with reference to FIG. 2 is also valid for an embodiment of a vertical pump 100 according to the invention.

(10) FIG. 2 shows the vertical pump 100 in its usual operating position, i.e. in vertical orientation. Hereinafter relative terms regarding the location like “above” or “below” or “upper” or “lower” refer to this operating position shown in FIG. 2.

(11) The vertical pump 100 has a pump bowl 11 (at a lower end), a pump head 12 (at an upper end) and a pump column 3 arranged between the pump bowl 11 and the pump head 12. The vertical pump 100 comprises a pumping unit 2 located at the pump bowl 11 of the pump 100. The pumping unit 2 includes a suction bell 18 having an column inlet 14 for a fluid to be pumped and with at least one impeller 19 (see FIG. 3, not shown in FIG. 2), but quite often a plurality of impellers 19 (pump device) for conveying the fluid from the column inlet 14 to an column outlet 31 below the pump head 12 of the pump. The impellers 19 are mounted in series on a pump shaft (pump device, not shown) in a torque-proof manner. The pump shaft for rotating the impeller(s) 19 is sometimes also referred to as line shaft.

(12) From the pump head 12 of the pumping unit 2 the tubular pump column 3 vertically extends upwards to connect the pumping unit 2 to a bearing unit 4 for supporting the pump shaft that vertically extends within the pump column 3. The pump column 3 is in fluid communication with a discharge pipe 32 arranged at the pump head 12 and connects the pump column 3 with the column outlet 31 for discharging the pumped fluid. The pump column 3 extends in an axial direction A that is defined by the rotational axis of the pump 100 about which the impeller(s) 19 is/are rotating during operation. The axial direction A coincides with the vertical direction, i.e. with the direction of gravity, when the pump 100 is in its usual operating position. A direction perpendicular to the axial direction A is referred to as radial direction.

(13) On top of the bearing unit 4, a drive unit 5 is arranged for driving the impeller(s) 19 of the pump 100. The drive unit 5 can be, for example, an electric motor or any other driver. The drive unit 5 is operatively connected to the impeller 19 by the pump shaft or the line shaft extending in the center of the pump column 3 and coaxially therewith. The pump shaft is supported by the bearing unit 4 and a plurality of shaft bearings arranged within the pump column 3 at different heights for guiding the pump shaft along its entire axial length.

(14) The vertical pump 100 is arranged in a canister 6 surrounding the pump column 3. The canister 6 is of essentially cylindrical shape and extends in the axial direction A to receive the pump column 3 and the pumping unit 2 of the vertical pump 100. At its upper end, the canister 6 is supported by a foundation 7 and can be fixed to the foundation 7 by screws or bolts (not shown) or any other appropriate means or device.

(15) The vertical pump 100 further comprises a support structure 8 arranged below the bearing unit 4, which supports the entire vertical pump 100. As shown in FIG. 2 the support structure 8 can rest on the canister 6 or can be mounted to the canister 6. Alternatively, or additionally, the support structure 8 can also be directly connected to or supported by the foundation 7. The pump column 3 and the pump unit 2 usually freely hang, i.e. without additional support, into the canister 6.

(16) Approximately at the same height with respect to the axial direction A where the discharge pipe 32 is arranged, an inlet pipe 9 is disposed through which the fluid to be pumped can enter the canister 6 as indicated by the arrow without reference numeral on the right side of FIG. 2. During operation of the pump 100 the canister 6 is completely filled with the fluid to be pumped. The fluid enters the canister 6 through the inlet pipe 9, is sucked through the column inlet 14 of the pump 100 by the action of the rotating impeller(s) 19 and discharged through the discharge pipe 32 as indicated by the arrow without reference numeral on the left side of FIG. 2.

(17) The difference in height (with respect to the axial direction A) between the column inlet 14 of the pump 100 which is arranged at the pump bowl 11 and the inlet pipe 9 for the fluid which is arranged below the pump head 12 increases the suction pressure at the column inlet 14 of the pump 100, thus also increasing the available net positive suction head (NPSH).

(18) According to an embodiment of the invention a vibration damper 10 is disposed between the pump column 3 and the canister 6 for suppressing the vibration of the pump column 3. The vibration damper 10 comprises at least two damping arms 15. In the embodiment shown in FIG. 2, four damping arms 15 are provided. The vibration damper 10 further comprises, a holding device 20. The four damping arms 15 are mounted to the holding device 20, which holding device 20 is arranged around the pump column 3.

(19) The pump column 3 is supported in a stabilizing manner by the damping arms 15 disposed on an outer surface 30 of the pump column 3. Each damping arm 15 comprises a support end 150 which extends towards an inner surface 60 of the canister 6, in order to support the pump column 3 in a radial direction, which radial direction is perpendicular to the axial direction A. The pump assembly 1 is characterized in that each support end 150 is movable independently from the other support ends 150 with respect to the axial direction A.

(20) The damping arms 15 therefore create a link between the pump column 3 and the canister 6 that rigidifies and stabilizes the pump assembly 1. The damping arms 15 are connected to the pump column 3 and contact the inner surface 60 of the canister 6 with the support ends 150, in dependence of the operating state of the pump assembly 1. As the damping arms 15 are independent in movement, they will follow a shape of the pump column 3 and allow a contact all around in every operating state.

(21) The damping arms 15 are orientated along the axial direction A with their support ends 150 extending towards the pump head 12.

(22) By way of example, FIG. 3 shows a vibration mode of the pump column 3 that is due to an excitation of a specific natural frequency. If the rotational speed of the drive unit 5 corresponds to a frequency which is equal or close to this structural natural frequency of the system, the corresponding mode is excited, resulting in strong vibrations. Since the pump column 3 is essentially only supported by the foundation 7 but otherwise freely hanging in the canister 6 the pump column 3 and the pump unit 2 attached to it can experience such oscillations as shown in FIG. 3. These resonant effects can have detrimental impacts on the pump 100. In particular, a premature failure of the bearings like the shaft bearings can be caused by resonance.

(23) In FIG. 3 the locations denoted with reference numerals 33, 34, 35 represent the location of the pump column 3 when the pump 100 is not in operation and there is no vibration, while the locations denoted with reference numerals 331, 341, 351 represent the pump column 3 in a vibration mode when the corresponding structural natural frequency (eigenfrequency) of the vibratory system is excited, for example by the rotational frequency of the drive unit 5.

(24) In order to resolve these resonant vibrations, the present invention proposes damping arms 15 for suppressing such vibrations or in other words for shifting the structural natural frequency of the vibratory system to such high frequencies which are far away e. g. from the rotational frequency of the drive unit 5.

(25) Preferably a plurality of damping arms 15 is located at or near such a height between the column inlet 14 and the column outlet 31 where the antinode of the vibration mode to be suppressed is located. It goes without saying that more than two pluralities of damping arms 15 can be arranged between the pump column 3 and the canister 6 at different axial positions (i.e. different heights).

(26) Furthermore, the vibration damper 10 comprises the damping arms 15 and the holding device 20. The damping arms 15 are mounted to the holding device 20, wherein more than one vibration damper 10 can be arranged between the pump column 3 and the canister 6 with said vibration dampers 10 being located at different axial positions (i.e. different heights with respect to the axial direction A). For suppressing the vibration mode illustrated in FIG. 3, for example a first vibration damper 10 can be located at a height indicated by the level 36 and a second vibration damper 10 can be located at a height indicated by level 37 in FIG. 3. Of course, it is also possible to locate individual vibration dampers 10 at such heights that they suppress vibration modes belonging to different structural natural frequencies of the vibratory system. For example, level 37 can be a good location for the vibration damper 10 as it is near the antinodes for the first three lateral column modes.

(27) FIG. 4 shows a perspective view of an embodiment of the vibration damper 10 according to the invention. The basic design of the vibration damper 10 is such that at least two damping arms 15 are arranged at the pump column 3 for adding stiffness and stability between the canister 6 and the pump column 3. Thus, the damping arms 15 clamp and/or support the pump column 3 against the canister (not shown in FIG. 4) therewith suppressing or at least dampening the vibration of the pump column 3.

(28) The damping arms 15 are arranged at the holding device 20 and are therefore a component of the vibration damper 10. The vibration damper 10 comprises the plurality of, here eight, damping arms 15, each of which is designed to move independently from the other damping arms 15.

(29) As shown in FIG. 4 the eight damping arms 15 are fixed to the holding device 20, which is configured to be mounted around the pump column 3. The holding device 20 is designed as an essentially ring-shaped band, wherein the inner diameter of the ring-shaped band is such that the holding device 20 closely fits around the pump column 3. The holding device 20 comprises a first half shell 121, and a second half shell 122. The first half shell 121 and the second half shell 122 are connected by a fastener 120. The fastener 120, for example a clasp or a flange, or a screw connection, is designed such that the holding device 20 can be easily mounted to or removed from the pump column 3. Due to the fastener 120, the holding device 20 can be opened to receive the first half shell 121 and the second half shell 122 and the first half shell 121 and the second half shell 122 can be removed from the pump column 3. When the fastener 120 on the other hand is closed, the holding device 20 is fixed to the pump column 3. For removing the holding device 20 from the pump column 3 only the fastener 120 must be opened and the holding device 20 can be easily removed.

(30) The holding device 20 of FIG. 4 further comprises a first retainer 201 and a second retainer 202, which are mounted around the pump column 3. Each of the damping arms 15 is connected with a first connecting end 151 to the first retainer 201 and with a second connecting end 152 to the second retainer 202.

(31) Preferably, the damping arms 15 are equidistantly arranged on the holding device 15, such that the damping arms 15 are equidistantly located about the circumference of the pump column 3 when the holding device 20 is mounted to the pump column 3, such that the damping arms 15, restrain the pump column 3 equally in all radial directions. Each damping arm 15 is designed such that its support end 150 is located above the first retainer 201 and the second retainer 202 with respect to the axial direction A.

(32) For most applications it is sufficient to provide at most two vibration dampers 10. Preferably, each vibration damper 10 has three or four to eight damping arms 15. The vibration dampers 10 can be located at different heights of the pump column i.e. at different positions with respect to the axial direction A (not shown in FIG. 4). By this measure all structural natural frequencies can be increased to such an extent that they are considerably higher than the excitation frequencies occurring in the operating speed range of the vertical pump 100.

(33) FIG. 5 shows a cross-sectional view of a variant of the first embodiment of the vibration damper 10 shown in FIG. 4. In addition, FIG. 6 shows a front view of the vibration damper 10 of FIG. 5 arranged on a pump column 3. The damping arms 15 shown in this variant comprise a flattened edge at the support end 150, which faces towards the inner surface 60 of the canister 6.

(34) Each damping arm 15 can engage the inner surface 60 of the canister 6 independently, thus forming a stabilizing connection between the canister 6 and the pump column 3. The pump column 3 can be clamped and/or supported by the damping arms 15, when the damping arms 15 are supported with their support end 150 on the inner surface 60 of the canister 6. Each damping arm 15 is a lever and comprises the connecting end 151, 152 connected to the outer surface 30 of the pump column 3 (i.e. to the first retainer 201 and the second retainer 202). The connecting end 151, 152 of each damping arm 15 is a fulcrum of the lever and the support end 150 of each damping arm 15 is a load point of the lever, at which load point the damping arm contacts the inner surface 60 of the canister 6. Additionally, an angle α between the pump column 3 and each damping arm 15 is larger than 0° and smaller than 90°. Preferably, the angle α is about 10° to 80°, more preferred 30° to 80°, especially preferred 30° to 60°. The angle α can also vary due to the operation of the vertical pump 100, since the damping arms 15 can be bendable, with respect to the radial direction so that the vibrations of the vertical pump 100 are suppressible. Therefore, if the support end 150 of a single damping arm 15 is pressurized in the operating state the damping arm will move about the fulcrum (in the radial direction) and the support end 150 will independently and freely move with respect to the axial direction A, without affecting an axial movement of another damping arm 15.

(35) Referring now to all described embodiments and variants of the vibration damper 10 or the damping arms 15, respectively, it is also possible to directly fix the individual damping arms 15 at an appropriate location to the pump column 3, for example by welding. Thus, it is not necessary that the damping arms 15 are fixed to the pump column 3 via the holding device 20.

(36) For most applications it is preferred that three or four damping arms 15 are arranged at the same height between the pump bowl 11 and the pump head 12 of the pump 100. For other applications up to eight damping arms 15 arranged at the same height (with respect to the axial direction A) can be preferred. In any case it is preferred that the damping arms 15 are equidistantly distributed along the circumference of the pump column 3 at said height.

(37) In addition, for many applications it is sufficient to have at most two vibration dampers 10 at different heights with respect to the axial direction A in order to shift all structural natural frequencies of the vibratory system to higher frequencies than the frequencies at which the vertical pump 100 is operated.

(38) In many applications it is not needed or even not desired that the pump column 3 of the vertical pump 100 is centered with respect to the canister 6 in the mounted state, i.e. the distance in radial direction between the pump column 3 and the canister 6 varies along the circumference of the pump column 3 and/or along the height of the pump column 3 in axial direction A. In such applications it is not desired that the damping arms 15 exert a centering force on the pump column 3 because such additional centering forces could result in additional loads acting on parts of the pump 100, for example on the bearings.

(39) Preferably all damping arms 15 are configured in an identical manner, so that each vibration damper is very easy to manufacture. Slight deviations of the canister 6 and/or the pump column 3 from a circular cross-section are then compensated by the damping arms 15, because they are movable independently from each other. Thus, the deviations from a circular cross-section are automatically compensated, because each of the equally designed damping arms can include a different angle α with the pump column 3 than the other damping arms 15. Usually, the variation in the angle α as seen over all damping arms 15 is quite small and does not exceed one degree.