AU2008243437A1 - Delivery pump - Google Patents

Description

WO 2008/131846 PCT/EP2008/002767 KSB Aktiengesellschaft 5 Description Delivery pump The invention relates to a delivery pump with a 10 variable-speed drive, the delivery pump being designed as a single-stage rotatory pump with a radial impeller (2) of centrifugal type of construction, arranged rotatably in an impeller chamber of a pump casing (1), for delivering a fluid between a pump inlet (4) and a 15 pump outlet (13), the radial impeller (2) being connected to a drive motor variable in speed into the five-digit range of revolutions per minute, the radial impeller (2) receiving the flow centrally, being provided with delivery ducts (3) and, in the case of an 20 outside diameter of up to 55 mm, delivery heads of up to 300 m. In the field of research and development processes in the chemical and pharmaceutical industries, there is 25 the demand for ever faster developments at lower costs. The production of such substances requires more flexible, smaller-scale and more environmentally friendly processes. This leads to the use of process engineering components which are sometimes operated 30 with very low filling volumes and with a continuous substance flow. On account of the demand for a flexible use of such plants, it is necessary to be able to scavenge the entire plant, together with the assemblies mounted in it, with the aid of special scavenging 35 media. Such plants require an accurate, constant, freely adjustable and pulsation-free volume flow of liquid WO 2008/131846 - 2 - PCT/EP2008/002767 substances. For high-precision continuous volume flows in the range of zero milliliters per minute up to a three-digit number of liters per hour, positive-displacement pumps in the form of 5 micro-annular and gear pumps and also in the form of diaphragm and piston pumps are employed. Such positive-displacement pumps have the disadvantage of the lack of reliability due to friction between the components to be sealed off, moved in relation to one 10 another, and their pulsating delivery stream. A resulting outlay in terms of maintenance and the costs for wearing parts and for exchanging these are detrimental to rapid research and development work and appreciably disrupt a,production process. 15 A rotatory pump, designed as a canned motor pump, for the circulation of supercritical hydrocarbons is known from WO 2005/052365 A2. The drive motor has a can made from PEEK, within which is arranged a rotor protected 20 by a high-grade steel covering. Ceramic bearings of the pump shaft and of the drive rotor are lubricated by a part stream of the delivery fluid, said part stream being extracted from the pump casing. The impeller of open design has a diameter of between 1 and 2 inches, 25 and the impeller-driving rotor of the rolling bearing-mounted direct-current motor has a diameter of between 1.5 and 2 inches. The single-stage pumping arrangement with the open impeller is intended to reach maximum rotational speeds of up to 60 000 rpm. The 30 suction connection piece, the pressure connection piece and a type of spiral chamber following the impeller are arranged in an outer pump casing part, while an inner pump casing part has the overhung-mounted impeller and a fastening for a variable-speed direct-current canned 35 motor as a drive motor. The disadvantage of this canned motor design is the multiplicity of gaps which, because of the complex flow WO 2008/131846 - 3 - PCT/EP2008/002767 routing between the pump and canned motor, seriously impede the cleaning of the pump. Since part of the delivery fluid flows permanently through the motor and its gap space, a high introduction of heat into the 5 delivery fluid occurs due to the frictional heat of the rolling bearings and to the heat loss from the canned motor. Consequently, this pump can be operated only in the immediate vicinity of an undefined optimal operating point. If this pump were operating under part 10 load, an inadmissibly high introduction of heat would take place very quickly. This would result not only in damage to the fluid, but also in a failure of the pump as a result of cavitation or dry running. 15 The problem on which the invention is based is, for the delivery and metering of liquid substances in the milliliter range of chemical, pharmaceutical and/or cosmetic components, to develop a pump unit, the delivery rate of which is variable, pulsation-free and 20 accurately adjustably, over a wide range for different delivery media having different properties and the pump of which can be cleaned easily for rapid product changes. 25 The problem is solved by means of the features of claim 1. A metering pump in the form of a rotatory pump of centrifugal type of construction is consequently implemented. This is designed as a delivery pump for use in a process engineering plant for nominal 30 operation in the form of continuous rotatory pump part-load operation with delivery rates in the range of 0 ml/min to 7000 ml/min, nominal operation being characterized by a rotatory pump part-load-specific rotational speed nq TL 2 0,05 10, and the impeller 35 chamber being provided on the circumference with one or more pump outlet ducts arranged at an acute angle to or tangentially to the radial impeller outside diameter.

WO 2008/131846 - 4 - PCT/EP2008/002767 In complete contrast to all current rotatory pump design rules or provisions, this rotatory pump is designed for extreme part-load operation, with the result that small quantities are delivered, 5 pulsation-free. For this purpose, the delivery pump preferably has a rotatory pump part-load-specific rotational speed nq TL 0.05 3 (1/min). Designing the delivery pump for a rotatory pump part-load operating range nqTL< 2 .5 has also proved advantageous. The outside 10 diameter of the radial impeller (2) may amount to a maximum of 70 mm. According to further refinements, the pump casing, with a radial impeller arranged in~ it, preferably, has a 15 residual volume lower than 30 milliliters. This has the considerable advantage that the delivery pump is easily scavengable. In addition, as a result of the low residual volume and the minimum number of gaps, when a fluid to be delivered is changed, only low product 20 losses during a cleaning or scavenging of the delivery pump occur in the latter. Furthermore, an inside diameter of the impeller chamber is designed to be a maximum of 4% larger than an outside diameter of the radial impeller. Also, by reducing the size of the 25 impeller chamber surrounding the radial impeller, an increase in a dynamic pressure prevailing at the pump outlet duct takes place. In this case, the inlet ports of one or more pump outlet ducts are designed in the form of pressure tubes or similarly to a pressure tube. 30 According to another refinement of the delivery pump, the latter is provided with a thermal control device, preferably for nominal operation at a rotatory pump part-load-specific rotational speed nqTL 0.05 . 1 35 (1/min). This device improves the delivery of sensitive fluids and/or of fluids with a low boiling point by means of WO 2008/131846 - 5 - PCT/EP2008/002767 the delivery pump capable of being operated in a wide nqTL range. According to another design, a seal is arranged between 5 the impeller chamber and the radial impeller and/or its shaft. A design is likewise possible in which a hermetically leaktight magnet-coupled drive transmits a torque to the radial impeller. Also, a bearing for the shaft is arranged on the pump casing, on the thermal 10 control casing and/or on a bearing casing. Moreover, the delivery pump may be designed as a block assembly with a flanged-on motor. The delivery pump is characterized by constant running 15 operation or by metering operation, depending on a drive to be used. Exemplary embodiments of the invention are illustrated in the drawings and are described in more detail below. 20 In the drawings: fig. 1 shows a delivery pump in longitudinal section fig. 2 shows a perspective view of the pump 25 unit fig. 3 shows a perspective view of an impeller fig. 4 shows an impeller in section fig. 5 shows a cross section through the delivery pump and 30 fig. 6 shows the position of the delivery pump in an nq graph. Fig. 1 illustrates a delivery pump of single-stage type of construction. A radial impeller 2 of centrifugal 35 type of construction is arranged rotatably in the pump casing 1. The radial impeller 2 has delivery ducts 3 and receives the flow centrally through a pump inlet 4. The radial impeller 2 is connected force-transmittingly WO 2008/131846 - 6 - PCT/EP2008/002767 to a variable-speed drive 5 and has an outside diameter DA which may amount to up to 70 mm. The radial impeller rotates in an impeller chamber 6, the inside diameter DLRI of which is designed to be only a maximum of 4% 5 larger than the outside diameter DA of the radial impeller 2. The pump casing 1 is provided with a thermal control device 7 which in this exemplary embodiment is 10 integrated in the pump casing. Other forms of construction are also possible. Cooling spaces 7.1 to 7.3 surround the impeller chamber 6 and also a seal casing 8 contiguous to the pump casing 1. Within the seal casing B is arranged, as a type of shaft seal, a 15 seal 9 which is illustrated in the exemplary embodiment as a lip sealing ring. Depending on the delivery fluid used, the seal 9 may also be designed as a floating ring seal. The seal 9 may bear sealingly against the impeller 2, against an impeller hub 2.1 or against the 20 shaft 10, depending on the selected connection between the impeller and a shaft 10 of the drive. The thermal control spaces 7.1 to 7.3 are acted upon by external means. As a result, the parts of the pump casing which are touched by the delivery fluid are reliably cooled, 25 since the rotatory pump is designed for continuous operation in a part-load operating point map, the delivery rate limits of which lie in the range of 0 milliliters/min to 3600 milliliters/min in the case of a delivery head limit of 20 meters - 300 meters. As a 30 result of the high rotational speed of the drive 5 necessary for this purpose, additional coolant 11 is arranged on the outer circumference of the drive 5. The drive 5 is also connected or fastened force-transmittingly to the thermal control device 7. 35 The area of the pump inlet 4 is defined by a bearing face 12 which is located in the immediate vicinity of the pump interior and against which a line to be WO 2008/131846 - 7 - PCT/EP2008/002767 connected for a delivery fluid bears sealingly. A similar design is present at the pump outlet 13 which here is located below the drawing plane and can be seen only partially as a semicircle. The fastening of pump 5 lines, not illustrated here, which are to be connected thereto takes place by known means, for example union nuts. By a pump line being led directly up to the impeller chamber 6 and because of the small diameter differences between the impeller outside diameter DA 10 and the inside diameter DLRI Of the impeller chamber 6, a residual volume equal to or- lower than 50 milliliters occurs within the pump casing, with mounted radial impeller, for a delivery fluid. This very small quantity has the advantage that only the least possible 15 losses arise when the valuable delivery fluids are changed. The pump inlet 4 and the pump outlet 13 are clear from fig. 2 which is a perspective view of the delivery pump 20 constructed as a unit. The thermal control device 7 is integrated into the pump casing 1, and the pump inlet 4 and pump outlet 13 are led through the thermal control device 7 as far as the impeller chamber. 25 External thermal control means, for example coolants, are supplied to and discharged from the thermal control spaces 7.1 to 7.3 by means of the axial or radial connections 14, 15 which can be used selectively. A pump unit and drive motor 5 are combined into a 30 structural unit and are held in a carrying element 16. The carrying element 16 affords the precondition for modular construction or installation into an existing plant. 35 Fig. 3 shows a perspective view of a radial impeller 2. The radial impeller 2 is of disk-shaped configuration and in this example is provided with a hub 2.1. A force-transmitting connection to the shaft 10, not WO 2008/131846 - 8 - PCT/EP2008/002767 illustrated here, of the drive 5 takes place within the hub 2.1. Delivery ducts 3 are arranged inside the radial impeller 2. In addition, a multiplicity of delivery depressions 18, which are configured in the 5 form of blind bores, are arranged on the impeller circumference 17. With the aid of these delivery depressions, the pressure coefficient of the rotatory pump impeller is improved. In one possible configuration, the pressure-side and suction-side cover 10 disks 19, 20 have a plurality of radially running delivery grooves 21. The delivery grooves- 21 likewise improve the pressure coefficient of an impeller installed according to fig. 1 in an impeller chamber 6. Compensating bores 22 penetrating through the impeller 15 in the axial direction serve for pressure compensation within the pump casing and at the same time as a mounting aid when a connection to the drive is being made. 20 Fig. 4 shows a section through an impeller 2 in which four delivery ducts 3 are used. Their diameter is co-ordinated such that they do not intersect an adjacent delivery duct in the region of the impeller inlet 23. This ensures that a defined impeller inlet 25 diameter is maintained. The depth T of the delivery depressions 18 is selected as a function of the desired residual volume of a ready-assembled pump. Instead of the delivery depressions 18, shown here, in 30 the form of bores, any other form, for example grooves, slots or the like, by means of which energy transmission is possible in the region of the impeller outside diameter, may also be employed. 35 Fig. 5 shows a cross section through the delivery pump. On account of the generously dimensioned thermal control space 7.2 which is operatively connected to the other thermal control space, continuous extreme WO 2008/131846 - 9 - PCT/EP2008/002767 part-load operation is ensured. The pump outlet duct 13 may be configured as a simple bore or, as illustrated, it may be formed by an insert 24 resembling a pressure tube and having an inlet port 25. The latter makes s simple adaptation possible. Owing to the minimized impeller chamber 6, a radial gap width which lies in the single-digit millimeter range is obtained between the outside diameter DA of the 10 radial impeller and the enveloping surrounding diameter DLRI Of the impeller chamber 6. In a practical rotatory pump, the radial gap between the impeller and casing lies in the region of 2 mm. The gap between the impeller and casing lies in a similar order of 15 magnitude in the region of the axial impeller sides. Owing to this configuration of the casing region having a minimal residual volume, the pump can be cleaned very quickly and reliably by a scavenging medium. The pump can also be adapted to changed delivery conditions or 20 plants with the lowest possible losses of parts of the delivery product. Owing to the continuous rotation of the centrifugal impeller 2, pulsation-free operation of this delivery pump is obtained. 25 Owing to the minimized gap between the impeller outside diameter and impeller chamber, the circumferential component of the impeller simultaneously approaches the circumferential speed, and, in combination with a pump outlet 13 arranged at an oblique angle, preferably 30 tangentially, to the impeller 2, a maximum possible dynamic pressure is obtained for this rotatory pump at its outlet port. In conjunction with the variable-speed motor, high delivery heads, along with a minimal residual volume within the pump casing, can be 35 implemented. The contact-free arrangement of the impeller within the impeller chamber avoids frictional surfaces bearing WO 2008/131846 - 10 - PCT/EP2008/002767 sealingly one against the other. This measure prevents the generation of mechanical frictional heat, prevents frictional wear and resulting contamination of a delivery fluid with abraded particles and improves 5 operational reliability due to substantially prolonged service lives. Moreover, sealing gaps which counteract cleanability are avoided. In fig. 6, the nq values of rotatory pumps are compared 10 with those of positive-displacement pumps in an nq graph in characteristic maps depicted by unbroken lines. The novel delivery pump, with its characteristic map, illustrated in gray, of the rotatory pump part-lpaa-specific rotational speed nqTL, covers the 15 range between these two opposite pump types for the first time.

WO 2008/131846 - 11 - PCT/EP2008/002767 List of reference symbols 1 = Pump casing 2 = Radial impeller 5 2.1 = Hub 3 = Delivery ducts 4 = Pump inlet 5 = Variable drive 6 = Impeller chamber 10 7 = Thermal control device 7.1-7.3 = Cooling spaces 8 = Seal casing 9 = Seal 10 = Shaft 15 11 = Coolant 12 = Bearing face 13 = Pump outlet 14, 15 = Connections for thermal control means 16 = Carrying element 20 17 = Impeller circumference 18 Delivery depressions 19, 20 = Cover disk 21 = Delivery grooves 22 = Compensating bores 25 23 = Impeller inlet 24 = Inlet port 25 = Pressure tube D, = Outside diameter radial of impeller 2 DLRI = Inside diameter impeller of chamber 6

Claims (15)

1. A delivery pump with a variable-speed drive (5), the delivery pump being designed as a single-stage 5 rotatory pump with a radial impeller (2) of centrifugal type of construction, arranged rotatably in an impeller chamber (6) of a pump casing (1), for delivering a fluid between a pump inlet (4) and a pump outlet (13) the radial impeller (2) being connected to a drive 10 motor variable in speed into the five-digit range of revolutions per minute, the radial impeller (2) receiving the flow centrally, being provided with delivery ducts (3) and, in the case of an outside diameter of up ~ to 55 mm, having speed-dependent 15 delivery heads of up to 300 m, characterized in that, for use in a process engineering plant, the delivery pump is designed for nominal operation in the form of continuous rotatory pump part-load operation with delivery rates in the range of 0 ml/min to 7000 ml/min, 20 in that nominal operation is characterized by a rotatory pump part-load-specific rotational speed nqTL 0 .05 10 (1/min), and in that the impeller chamber (6) is provided on the circumference with one or more pump outlet ducts (13) arranged at an acute 25 angle to or tangentially to the radial impeller outside diameter.

2. The delivery pump as claimed in claim 1, characterized in that nominal operation preferably has 30 a rotatory pump part-load-specific rotational speed nqTL : 0.05 3 (1/min).

3. The delivery pump as claimed in claim 1 or 2, characterized in that the delivery pump is designed for 35 a rotatory pump part-load operating range nqTL< 2 .5. WO 2008/131846 - 13 - PCT/EP2008/002767

4. The delivery pump as claimed in claim 1, 2 or 3, characterized in that the outside diameter of the radial impeller (2) amounts to a maximum of 70 mm.

5 5. The delivery pump as claimed in one of claims 1 to 4, characterized in that the pump casing (1), with a radial impeller (2) arranged in it, preferably has a residual volume lower than 30 milliliters. 10

6. The delivery pump as claimed in claim 5, characterized in that an inside diameter (DLRI) of the impeller chamber (6) is designed to be a maximum of 4% larger than an outside diameter (DA) of the radial impeller (2). 15

7. The delivery pump as claimed in claim 4 or 5, characterized in that, by reducing the size of the impeller chamber (6) surrounding the radial impeller (2), an increase in a dynamic pressure prevailing at 20 the pump outlet duct (13) takes place.

8. The delivery pump as claimed in one or more of claims 1 to 7, characterized in that inlet ports (24) of one or more pump outlet ducts (13) are designed in 25 the form of pressure tubes (25) or similarly to a pressure tube.

9. The delivery pump as claimed in one or more of claims 1 to 8, characterized in that the pump casing 30 (1) is provided with a thermal control device (7-7.3).

10. The delivery pump as claimed in claim 9, characterized in that, preferably for nominal operation at a rotatory pump part-load-specific rotational speed 35 nqTL 0.05 1 (1/min), the pump casing (1) is provided with a thermal control device (7-7.3). WO 2008/131846 - 14 - PCT/EP2008/002767

11. The delivery pump as claimed in one or more of claims 1 to 10, characterized in that a seal (9) is arranged between the impeller chamber (6) and the radial impeller (2) and/or its shaft (10). 5

12. The delivery pump as claimed in one of claims 1 to 11, characterized in that a hermetically leaktight magnet-coupled drive transmits a torque to the radial impeller (2). 10

13. The delivery pump as claimed in one of claims 1 to 12, characterized in that a bearing for the shaft (10) is arranged on the pump casing (1), on the thermal control casing (7) and/or on a bearing casing. 15

14. The delivery pump as claimed in one of claims 1 to 13, characterized in that the delivery pump is designed as a block assembly. 20

15. The delivery pump as claimed in one or more of claims 1 to 14, characterized by constant running operation or by metering operation.