KR100471537B1 - Centrifugal pump and bearing arrangement thereof - Google Patents

Abstract

A centrifugal pump capable of being coupled to a drive motor, where the pump has an impeller (3) for radial direction of flow and having a discharge edge (13) at its outer diameter, and where the pump has a radially split pump casing (15) and is provided with at least one shaft seal (2). The impeller (3), for absorption of the forces acting on the impeller (3), is supported in a bearing device advantageously consisting of two axially adjacent bearings (1, 1'), where the width of the bearings or their respective bearing raceways (12, 12'; 14, 14') forms a characteristic distance a. A centre point (4) on the discharge edge (13) of the impeller (3) has, seen axially, a position which is at a distance b from another centre point between the bearings (1, 1') and in the direction of or from the inlet end (21) of the pump, where b </= 2a.

Description

Centrifugal pump and bearing arrangement

The present invention relates to a centrifugal pump that can be coupled to a drive motor, wherein the pump has an impeller having a discharge edge at its outer diameter, and the pump is provided with at least one shaft seal.

It is an object of the present invention to obtain a significant improvement of a motor-driven pump unit having a so-called single suction main centrifugal pump and a drive motor arranged in direct connection with the pump. The pump unit can typically be in a vertical form with a vertical axis of rotation and is constructed such that the pump components essential for maintenance can be disassembled without moving the pipeline or drive motor.

Centrifugal pumps included in this kind of pump unit are known in several different embodiments. Typically the shaft is supported by two shaft bearings hundreds of millimeters apart. At one end the shaft supports the impeller, and a shaft seal is arranged between the impeller and one bearing. In this embodiment the impeller has a substantially overhang of approximately the same size as the distance between the bearings. Typically, a radial force of varying magnitude acts on the impeller as the fluid flows through the pump. This force eventually buckles (deforms) the shaft, which requires a large enough gap in the inner seal of the impeller, resulting in a significant reduction in the function of the shaft seal. This factor has been a subject of caution in the specification for the minimum quality of the pump. Specifications The API 610 (American Petroleum Institute) and ISO 5199 (International Organization of Standardization) both specify a maximum allowable value of 0.05 mm for buckling near the shaft seal. For commercial and technical evaluations, another method of indicating the degree of buckling is used, ie L ³ / D ⁴ . In this expression, L is the cantilever length of the impeller and D is the diameter of the shaft.

To eliminate the support and cantilever of the impeller, bearings can be installed on each side of the impeller. However, this requires two shaft seals, one on each side. At least one bearing can also be disposed in the pumped fluid so that it can be lubricated and cooled. In special cases, such as in sealed sealed pumps, bearings and drive mechanisms are arranged in the fluid for some time. As a result, this embodiment does not have a shaft seal.

Furthermore, the impeller can be mounted directly on the shaft of the drive motor (usually an electric motor) or on a shaft extension rigidly connected to the electric motor shaft. However, conventional electric motors of standard design, at motor outputs of 10 to 30 kW or more, do not have sufficient bearing strength for their shaft bearings. Thus, there is a pump design in which the shaft extension has at least one spare bearing.

The pump casing may be split along the pump shaft (axially split), or be mounted on the shaft, so that internal components of the pump unit such as impellers, shaft seals, etc. can be easily disassembled without having to disassemble the pipeline or drive motor. Can be divided laterally (radial split). With regard to radial division, it is common nowadays to use openings on the drive motor side (so-called "back pull out"). Disassembly is probably done by first dismantling a part of the shaft or a part (spacer) of the extended shaft coupling. In this case, these parts have a length from which internal parts can be removed. In this type of pump unit, there is usually an elastic shaft coupling that can withstand one or more torsions, so that some deviation from the exact concentric positions of the centrifugal pump and drive motor is possible. The shaft bearings can be arranged according to the previous method, or if one shaft coupling is only angular-elastic, one bearing can be placed on the pump shaft and the other bearings are driven through the drive motor bearings. Is done.

1 is a cross-sectional view of a pump.

2 and 3 are cross-sectional views of two variants.

It is an object of the present invention to provide a novel centrifugal pump to overcome many of the drawbacks associated with the prior art.

According to the invention, the centrifugal pump is supported by a bearing device consisting of only two axially adjacent bearings, in order to absorb the force the impeller exerts on the pump, the design of the axial width of the bearing or the bearing raceway Form a characteristic distance (a), the center point on the discharge edge of the impeller having a position at a distance b from the axial center point between the bearings in the direction of the inlet end of the pump, as seen in the axial direction, B is less than or equal to 2a.

According to another embodiment, a rotatable sleeve is arranged between the at least one bearing and the at least one shaft seal to carry and / or branch out leaks from the shaft seal around the pump, the sleeve defining an impeller hub section. Divided into two chambers, the chamber in which the bearing is placed is separated from the pump fluid and / or any fluid leaking from the shaft seal.

According to another embodiment, at least two contact surfaces of a recess in which one end of the drive shaft for transmitting torque from the drive motor to the impeller receives the shaft end in the impeller hub, for example using a so-called spline or key coupling It is fixed and the other end of the drive shaft is connected to the drive motor shaft through a coupling. The coupling consists of a first flange fixed to the drive shaft or integral with the drive shaft, and a second flange fixed to the motor shaft or integral with the motor shaft, the first and second flanges being nut-bolt connections. And adhesive bonding, shearing pins, and the like.

The bearings in the bearing arrangement have respective outer bearing raceways arranged in the impeller hub and their respective inner bearing raceways mechanically connected to the pump casing.

Advantageously, the shaft seal is disposed in the annular portion of the impeller hub, and each outer bearing raceway of the bearing can be fastened to the drive shaft via the impeller and rotate together.

The shaft of the centrifugal pump is usually arranged substantially vertically and the drive motor is mounted on a stand which is connected to the pump casing.

The rotatable sleeve has double walls and / or vanes that are designed to create a pumping action when the sleeve rotates with the impeller to deliver any leaking fluid from the shaft seal past the chamber for the shaft bearing device to the periphery of the pump. .

The invention will now be described in more detail with reference to the accompanying drawings.

One of the features of the invention is that the shaft bearings 1, 1 ′ and the shaft seal 2 are installed in the impeller 3 with at least no cantilever or no cantilever. The center line of the impeller is shown at 21. The radial forces and moments applied to the impeller are absorbed by the bearings without the occurrence of warp or bending moments and the accompanying deformation. L ³ / D ⁴ is actually equal to zero. The shaft bearings are thus made of bearing raceways (bearing surfaces) such that at least one bearing has a function equivalent to several spaced bearings. For example, the bearings are made as several single or double angular contact ball bearings, conical ball bearings or so-called four-point bearings. At least one shaft seal 2 for the pumping medium is arranged immediately after or at a limited distance to the first bearing 1, and the bearing 1 and the shaft seal 2 rotate relatively thin in wall thickness. Separated by a possible split cup or sleeve 5. The sleeve 5 thus divides an area within the impeller hub section into two separate chambers 6, 7, and the second bearing 1 ′ is located completely separate from the pumping medium. The axial size of the sleeve 5 from the shaft seal 2 causes any leakage from the shaft seal chamber 7 to carry and / or branch around the pump unit 16 through the opening 17 in the pump casing, It is therefore large enough to prevent leakage from penetrating into the chamber 6 in which the shaft bearings 1, 1 ′ are arranged. Due to the limited space in the impeller hub section for bearings and seals, the drive shaft 8 for transmitting torque to the impeller 3 can load very large loads and at least two fastening members at one end of the drive shaft. It is connected to the impeller 3 via a firm connection using fasteners or shaft keys, a part of which is usually in the form of a so-called spline, indicated by reference numeral 9 in the drawing. The drive shaft 8 is preferably separated or sealed from the pumped fluid, using the sleeve 5 and the associated parts of the impeller hub section, the bearing carrier 19. At the other end of the drive shaft 8 it is also permanently engaged with or made of a single piece with the drive flanges 10, 10 ′, optionally with a flexible shaft 18 coupling coupled to the drive flange. Can be connected for delivery. The impeller hub section can also be made as a bearing raceway 12, 14; 12 ′, 14 ′ or bearing seat of the shaft bearing 1, 1 ′, in which case a force other than the torsional moment on the impeller 3 and Allow moment to transfer to bearing. This in turn means that the design can be optimized since the drive shaft 8 is only loaded by torque. The arrangement of the shaft bearings 1, 1 ′ and the shaft seal 2 inside the impeller 3 results in a significant change in the overall size and weight of the pump unit. Especially in the case of a vertical pump in which a drive motor (not shown) is supported by a stand (not shown) arranged on or immediately after the pump casings 15, 15 ′, 15 ″, 15 ′ of the centrifugal pump. A significant reduction in the overall height of is obtained. This reduces the magnitude and risk of normal motor vibration. If the pump unit is arranged onboard on a vessel, the risk of disturbance of the unit in the movement of the marine vessel and the vibration caused by the propulsion machinery is reduced. Form a bearing carrier.

The outer bearing ring or bearing raceway 12, 12 ′ of the shaft bearing can typically rotate with the impeller 3 and is arranged in the impeller hub 3 ′. This includes the advantage that only static stresses occur and therefore there is no dynamic load that can cause fatigue.

The bearing arrangement is also necessarily arranged in or connected adjacent to the impeller hub. The axial dimension of the bearing arrangement is therefore typically less than or equal to at least the entire axial length of the impeller.

In order to obtain optimum conditions with respect to the moment, the impeller 3 is supported by a bearing arrangement consisting of only two axially adjacent bearings 1, 1 ′, in order to absorb the forces acting on it, Each bearing raceway 12, 12 ′; 14, 14 ′ of the bearing in the form a characteristic distance (a) and, when viewed in the axial direction, the center point on the discharge edge 13 of the impeller 3. 4) is the position with a distance b from the center point between the bearings 1, 1 'in the direction of the inlet end 20 of the pump, where condition b &lt; The characteristic distance a of the present invention is the largest value of a1 and a2.

In a real shaft bearing, the width of the bearing, ie the axial dimension of the single or multiple bearing rings, has a first value a1 for the characteristic distance a. The second value a2 is the distance between the centers of force 30, 30 ′ on the centerline 21 of the bearing arrangement. For example, when a single row angular ball bearing is mounted pairwise in an "back-to-back" assembly, and a double row angular ball bearing and a so-called four point single row angular ball bearing In the case, the value of a2 is given in the ball bearing manufacturer's catalog, which is usually two to three times greater than a1. Of course, similar conditions apply in the case of conical ball bearings and other bearing types. The specific distance a of the present invention is the maximum of the values a1 and a2. Advantageously, the bearing device is manufactured with bearings of the type 2a greater than 1a so as to absorb the bending moment and the oblique moment in the best manner. Embodiments with a distance a1 can be used, for example, in simple structures in which only one adiabatic step ball bearing is used.

In general, the distance a1 is defined as the distance a when the distance a2 cannot be defined.

A rotatable sleeve 5 is preferably disposed between at least one bearing and at least the shaft seal 2 to carry and / or branch any leakage from the shaft seal 2 to the periphery 16 of the pump. . The sleeve 5 can properly divide the impeller hub section into two chambers 6, 7, and the chamber 6 in which the bearings 1, 1 ′ are arranged is leaking out of the shaft seal 2. Will be separated from the fluid and / or the pump fluid. The flanges 10, 10 ′ coupling between the shafts 8, 18 may be fixed by nut bolt connections or adhesive bonding or by using shearing pins or the like.

As can be seen in the figure, the bearings 1, 1 ′ have their respective outer bearing raceways 12, 12 ′ disposed on the impeller hub 3 ′, and each inner bearing raceway 14, 14 ′ of the bearings. ) Is mechanically connected to a pump casing 15 '"which acts as a bearing carrier. It can also be seen that the shaft seal 2 is arranged in the annular portion of the impeller hub. In addition, the outer bearing raceway 12 of the bearing It can be seen that 12 ′ can be connected to and rotated with the drive shaft 8 via the impeller 3.

The rotatable sleeve 5 is any leaking fluid which has a pumping action when the sleeve 5 rotates with the impeller 3 and moves beyond the shaft seal 2 past the chamber 6 for the shaft bearing device. It can be manufactured with double walls or with vanes, which is designed for the pumping action to take place in order to transfer it through the opening 17 of the pump casing to the periphery 16 of the pump. This is illustrated in FIGS. 2 and 3.

2 shows how the sleeve 5 has an additional part 22 in the form of a peripheral sleeve part with a radial bore 23. In FIG. 3 the sleeve is provided with a vane ring 24.

Claims (10)

A fluid delivery centrifugal pump that can be coupled to a drive motor, Casing 15, An impeller 3 having an outer diameter as the axial size and the discharge edge 13 and having a discharge edge 13 for discharging outward substantially in the radial direction, A bearing device disposed within the axial range of the impeller so as to rotationally support the impeller 3 in the casing 15 and comprising only one or more bearings 1, 1 ′; A central through bore for receiving a drive shaft 8 having a first end connected to the impeller 3 and a second end that can be coupled to the drive motor, the impeller being connected to the casing 15 (3) a bearing carrier 19, 15 "'extending into it, and At least one shaft seal 2 disposed between the impeller 3 and the casing to separate the bearing device from the carrying fluid, The width of the bearings 1, 1 ′ or the respective bearing raceways 12, 12 ′; 14, 14 ′ is the total axial distance a1 of the bearing and the force of the bearing at the center line 21 of the bearing arrangement. Form a characteristic distance (a) constituting a maximum value of the distance (a2) between the centers of Centrifugal pump, characterized in that the center point 4 on the discharge edge 13 of the impeller 3 in the axial direction has a position at a distance b from the axial center point for the bearing device, wherein b ≦ 2a. 2. The bearing (1, 1 ') according to claim 1, wherein a sleeve (5) is connected to the impeller (3), the sleeve for carrying or branching leakage from the shaft seal (2) to the periphery of the pump (16). And at least one shaft seal 2, the sleeve 5 forms two chambers 6, 7, and the chamber 6 in which the bearings 1, 1 ′ are disposed pumps fluid. Or separate from any fluid leaking from the shaft seal. The recess according to claim 1 or 2, wherein one end of the drive shaft (8) for transmitting torque from the drive motor to the impeller (3) receives a shaft end in the impeller (3, 3 '). In at least two contact surfaces therein, it is fixed using a spline or key coupling or the like, and the other end of the drive shaft is connected to the drive motor shaft 18 via a flange 10, 10 ′ coupling. Centrifugal pump. 4. The coupling according to claim 3, wherein the coupling is a first flange (10) fixed to or integral with the drive shaft and a second flange (10 ') fixed to the motor shaft or integral with the motor shaft. Wherein the first and second flanges can be joined by a nut-bolt connection, adhesive bonding, shear pins, and the like. 3. The bearing (1, 1 ′) according to claim 1, wherein the bearings (1, 1 ′) have respective outer bearing raceways (12, 12 ′) arranged on the impellers (3, 3 ′). Centrifugal pump, characterized in that each of the inner bearing raceways (14, 14 ′) is mechanically connected to the pump casing. 3. The shaft seal (2) according to claim 1, wherein the shaft seal (2) is arranged in an annular part of the impeller, and each outer bearing raceway (12, 12 ′) of the bearing is driven through the impeller (3). 8) a centrifugal pump, which is fastened together and can rotate together. 3. Centrifugal pump according to claim 1 or 2, characterized in that the centrifugal pump has a rotational axis centerline (21) arranged essentially vertically and the drive motor is mounted on a stand connected to the pump casing. The double wall as claimed in claim 2, wherein the sleeve (5) is designed to create a pumping action when the sleeve rotates with the impeller to convey any leaking fluid from the shaft seal (2) around the pump. And a vane. A bearing device for rotationally supporting an impeller in a casing in a centrifugal pump, The impeller has an axial size and an outer diameter as the discharge edge 13 and has a discharge edge 13 for discharging outward substantially in the radial direction, The bearing arrangement is arranged in the axial range of the impeller 3 and consists of only one or more bearings 1, 1 ′, A bearing carrier 19 is provided, which is connected to the casing 15 and extends into the impeller 3, which can be coupled to a first end connected to the impeller 3 and a drive motor for the pump. A central through bore for receiving the drive shaft 8 having a second end therein; The width of the bearings 1, 1 ′ or the respective bearing raceways 12, 12 ′; 14, 14 ′ is the overall axial width a1 of the bearing and the force of the bearing at the centerline 21 of the bearing arrangement. Form a characteristic distance (a) constituting a maximum value of the distance (a2) between the centers of When viewed in the axial direction, the center point 4 on the discharge edge 13 of the impeller 3 is arranged to have a position at a distance b from the axial center point for the bearing arrangement, wherein b ≦ 2a. Bearing device. 10. The bearing (1, 1 ') according to claim 9, wherein the bearings (1, 1') have respective outer bearing raceways (12, 12 ') disposed on the impeller (3, 3'), respectively. Bearing device characterized in that the inner bearing raceway (14, 14 ') is mechanically connected to the pump casing.