Pump and method for adjusting the delivery rate of a pump

Abstract

The invention relates to a pump for conveying a conveying medium with a suction-side inlet, a pressure-side outlet, a suction chamber, a conveying housing with a pressure chamber and a transport element rotatably mounted in the conveying housing for conveying the conveying medium from the suction chamber to the pressure chamber and with a recirculation line through which the conveying medium is supplied from the pressure chamber to the suction chamber, wherein an interchangeable insert with an unchanging flow cross-section is arranged in the recirculation line.

Description

[0001] The invention relates to a pump for conveying a conveying medium, comprising a suction-side inlet, a pressure-side outlet, a suction chamber, a conveying housing with a pressure chamber, and a transport element rotatably mounted in the conveying housing for conveying the conveying medium from the suction chamber to the pressure chamber. The invention also relates to a method for adjusting the delivery rate of such a pump.

[0002] Pumps have long been known for a variety of tasks and in various designs. In many applications, the flow rate of a pump must be very precise, for example, to enable accurate metering of the pumped medium or to ensure that the production process functions properly and no quality issues arise. The effective flow rate of pumps depends on various parameters, in particular the speed, the viscosity of the pumped medium, the differential pressure, the gap dimensions, and the number of chambers.

[0003] With regard to gap dimensions, unavoidable manufacturing tolerances in particular lead to the fact that the design gap dimensions and thus also the design flow rate cannot be precisely achieved at a predetermined speed of the transport element. The actual flow rate is therefore inevitably subject to tolerances.

[0004] Adjusting the flow rate is a difficult and time-consuming task due to the various influencing parameters, especially if no further process changes are to be made during operation, such as changes to the speed of the transport element(s). In this case, the pump must first be assembled, set up for test operation, measured, and then disassembled if necessary. Other transport elements must be used, or the existing transport elements must be newly manufactured or reworked. These tasks are either impossible or difficult for users to manage. The resulting rework is time-consuming and also associated with high costs.

[0005] WO 2014 / 019687 A2 shows a multiphase pump with a recirculation line for returning the liquid phase to the suction side to ensure adequate lubrication of the screw spindles when the pumped medium contains increased gas content. A valve that can be opened or closed is arranged in the recirculation line.

[0006] The object of the present invention is to provide a pump and a method which make it possible to adjust the effective delivery rate of the pump at a predetermined speed of the transport element in a cost-effective, rapid and precise manner.

[0007] According to the invention, this object is achieved by a pump having the features of the main claim and a method having the features of the subordinate claim. Advantageous embodiments and further developments of the invention are disclosed in the subclaims, the description, and the figures.

[0008] The pump for conveying a conveying medium with a suction-side inlet, a pressure-side outlet, a suction chamber, a conveying housing with a pressure chamber and a transport element rotatably mounted in the conveying housing for conveying the conveying medium from the suction chamber into the pressure chamber and with a recirculation line via which the conveying medium is supplied from the pressure chamber to the suction chamber, is characterized in that a replaceable insert with a fixed flow cross-section is arranged in the recirculation line.

[0009] An advantage of the pump according to the invention is that the pump's delivery rate can be quickly and precisely adjusted at a predetermined speed of the transport element by inserting an insert with a particularly predetermined, fixed flow cross-section. Due to the fixed flow cross-section, a continuous, essentially constant loss volume flow is established in the recirculation line at the predetermined speed of the transport element. Depending on the size of the fixed flow cross-section of the insert, a corresponding effective delivery rate results at the predetermined speed. Pumps are operated over an operating range within which the pump provides the desired or guaranteed delivery rate under certain operating parameters, possibly also within a delivery rate range.A test or acceptance takes place at a so-called guarantee point, where defined conditions exist and the pump must deliver the guaranteed or desired flow rate at a predetermined speed. Once the predetermined speed is reached, the actual flow rate is measured at the outlet. This measurement is usually carried out using an insert with a minimal flow cross-section, in particular with a flow cross-section with a diameter of zero, i.e. a closed recirculation line. The actual flow rate is higher than the guaranteed flow rate at the guarantee point. The required flow cross-section is calculated from the difference between the actual flow rate and the target flow rate, and the appropriate insert is selected or manufactured and installed.A retest by operating the pump at the predetermined speed at the guaranteed point shows whether the desired flow rate has been achieved or whether further adjustments need to be made by using a different insert. A system consisting of several inserts with different flow cross-sections facilitates the adjustment of the flow rate. By installing a suitable insert with the defined flow cross-section, the effective flow rate at the predetermined speed of the transport element can be corrected so that it corresponds to the desired flow rate at the predetermined speed of the transport element. In particular, no disassembly of the pump is required to adjust the flow rate at the predetermined speed of the transport element.

[0010] If a different effective flow rate is to be achieved at the predetermined speed of the transport element, the insert can be replaced with one with a different predetermined, fixed flow cross-section or adapted accordingly. Using an insert with a larger flow cross-section will result in a lower effective flow rate at the predetermined speed of the transport element. A smaller flow cross-section of the insert, however, results in a larger effective flow rate at a constant speed.

[0011] The fact that the in particular predetermined, unchangeable flow cross-section of the replaceable insert is unchangeable means in particular that the flow cross-section cannot be changed during operation of the pump when the insert is arranged in the recirculation line. The suction chamber is in particular arranged in terms of flow between the inlet and the transport element. The transport element is preferably a screw spindle, a rotary piston, a worm or a gear. The flow cross-section is predetermined in that it is determined by selecting the correct or necessary insert with the suitable flow cross-section on the basis of measured values ​​before operation of the pump, wherein the interchangeability allows adaptation to changed operating conditions or wear.

[0012] Preferably, the insert is designed as a screw-in, clamp-in, or insertable bolt. This allows for particularly easy replacement and insertion of the insert.

[0013] A further development of the invention is characterized in that the insert is inserted into an opening in the pump housing and / or into a bushing inserted into the opening of the pump housing. This is advantageous in that a corresponding system with an insert and a bushing can be easily retrofitted to existing pumps. The inserts can be adapted to the properties of the bushing separately, so that the respective inserts can be optimally matched to the bushing. The bushing is supplied together with a set of inserts with different flow diameters and can also be used as a module during retrofitting.

[0014] Preferably, the bushing is secured in the conveyor housing by pressing, screwing, or welding. This creates a stable connection between the bushing and the conveyor housing. Alternatively, the bushing is formed integrally with the conveyor housing. This ensures that the bushing cannot become loose over time.

[0015] Preferably, the bushing is configured to correspond to the opening in the conveyor housing, and the insert is configured to correspond to the bushing. For example, the bushing has a contour, in particular an inner diameter, that corresponds to the contour of the insert, in particular an outer diameter of the insert. This minimizes tolerances between the opening of the conveyor housing and the bushing, and between the bushing and the insert, so that leakage currents are effectively avoided or at least reduced. Alternatively or additionally, the insert is configured to correspond to the opening.

[0016] The pump preferably has a housing on which the inlet and outlet are arranged. The discharge housing is preferably arranged within the housing. This allows the flow of the pumped medium in the pump to be optimized. At the same time, such an arrangement of the discharge housing dampens vibrations and noise, thus reducing the pump's noise emissions.

[0017] Alternatively, the inlet and outlet are located on the pump casing. This allows for a particularly simple and space-saving pump design.

[0018] Preferably, the bushing extends through the suction chamber. This enables a particularly simple and cost-effective design of the recirculation line. For this purpose, the suction chamber preferably at least partially surrounds the pump housing.

[0019] A further development of the invention is characterized in that the insert has a longitudinal bore and a transverse bore which are fluidically connected to one another, wherein the conveying medium passes from the pressure chamber via the longitudinal bore into the insert and via the transverse bore from the insert to the suction chamber.

[0020] Preferably, the longitudinal bore of the insert is a blind bore. With this design of the longitudinal bore, it is not necessary to seal the end of the longitudinal bore facing away from the pressure chamber with a sealing element. Furthermore, this design optimizes the flow behavior of the pumped medium in the recirculation line.

[0021] In a preferred embodiment, the bushing has a longitudinal bore that is fluidically connected to the longitudinal bore of the insert, and a transverse bore that is fluidically connected to the transverse bore of the insert. This is particularly advantageous from a rheological perspective.

[0022] Preferably, the longitudinal bore of the bushing is arranged substantially coaxially with the longitudinal bore of the insert. Preferably, the transverse bore of the bushing is arranged substantially coaxially with the transverse bore of the insert. This optimizes the flow behavior of the conveying medium within the insert and the bushing.

[0023] Preferably, the longitudinal bore of the bushing has a larger diameter than the longitudinal bore of the insert. Preferably, the transverse bore of the bushing has a larger diameter than the longitudinal bore of the insert. This focuses the pressure gradient in the recirculation line on the insert, thus relieving the bushing and preventing flow problems within the recirculation line.

[0024] Preferably, the predetermined, fixed flow cross-section of the insert is the smallest flow cross-section of the recirculation line. In this embodiment, the recirculation flow is most strongly influenced by the fixed flow cross-section.

[0025] Preferably, the fixed flow cross-section is formed in the longitudinal bore of the insert. This achieves a fluid-dynamically advantageous design of the recirculation line.

[0026] Preferably, a sealing element, in particular an O-ring, a sealing disc, or a sealing strip, is arranged on the insert. This prevents or at least reduces leakage from the pressure chamber to the suction chamber.

[0027] Preferably, at least one sealing element is arranged on the outer diameter of the bolt. Preferably, at least one sealing element is arranged between a head of the bolt and the bushing and / or an external thread of the bolt and an internal thread of the bushing. Such a sealing element prevents leakage currents along the outer diameter of the bolt.

[0028] The pump preferably has at least two transport elements. For example, two screw spindles can be rotatably mounted in the pump housing as a screw spindle pair, or several screw spindle pairs can be rotatably mounted in the pump housing. Providing at least two transport elements increases the pump's delivery capacity. Furthermore, this can contribute to increasing the pump's accuracy and precision with regard to the delivery rate.

[0029] The pump is preferably a single-spindle or multi-spindle screw pump. Screw pumps are highly efficient and durable. The pump is preferably single-flow or multi-flow.

[0030] The invention also solves the problem by the method for adjusting the delivery rate of a pump for conveying a conveying medium with a suction-side inlet, a pressure-side outlet, a suction chamber, a conveying housing with a pressure chamber and a transport element rotatably mounted in the conveying housing for conveying the conveying medium from the suction chamber into the pressure chamber and with a recirculation line via which the conveying medium is fed from the pressure chamber to the suction chamber, with the steps: a) Determining the effective flow rate of the pump at a predetermined speed of the transport element, b) determining the deviation of the effective delivery rate of the pump at the predetermined speed of the transport element from a predetermined delivery rate at the predetermined speed of the transport element and c) inserting an insert with a fixed flow cross-section into the recirculation line, wherein the predetermined, fixed flow cross-section of the insert is dimensioned such that the effective delivery rate of the pump at a predetermined speed of the transport element corresponds to the predetermined delivery rate at the predetermined speed of the transport element.

[0031] A particular advantage of this method is that the pump's delivery rate can be adjusted quickly and precisely without having to dismantle the pump. In one embodiment of the method, the effective delivery rate of the pump is determined at a so-called guarantee point, where, in addition to the predetermined speed, the delivery rate is generally determined, in particular measured, at a defined viscosity of the pumped medium and / or at a defined differential pressure. Based on the difference between the effective, i.e. measured, delivery rate and the target delivery rate under the defined conditions at the guarantee point, the insert with the appropriate flow cross-section is then selected and used.

[0032] The effective flow rate is, in particular, the actual amount of fluid pumped per unit of time, taking into account losses, especially losses due to the return of fluid via a recirculation line. Other possible losses may be due to friction losses, leakage currents, wear, temperatures, pressures, or suction conditions.

[0033] The effective flow rate of the pump at the predetermined speed of the transport element is determined, for example, by measuring and / or calculating.

[0034] Preferably, the recirculation line is closed when determining the effective flow rate of the pump at the predetermined speed of the transport element. For this purpose, an outlet insert, which has no flow cross-section, can be inserted into the recirculation line. In this variant, the method can be implemented very cost-effectively, since it is not necessary to first provide an outlet insert with an outlet flow cross-section.

[0035] Alternatively, when determining the effective delivery rate of the pump at the predetermined speed of the transport element, an output insert having an output flow cross-section is arranged in the recirculation line. Preferably, after determining the deviation of the effective delivery rate of the pump at the predetermined speed of the transport element from the predetermined delivery rate at the predetermined speed of the transport element, the predetermined, fixed flow cross-section of the insert is determined as a function of the deviation of the effective delivery rate of the pump at the predetermined speed of the transport element from the predetermined delivery rate at the predetermined speed of the transport element, as well as the output flow cross-section of the output insert. In this way, an iterative adjustment of the flow cross-section can be carried out.

[0036] Exemplary embodiments of the invention are explained in more detail below with reference to the figures. They show: Fig. 1 - a schematic representation of a pump; Fig. 2 - a schematic sectional view of a pump; Fig. 3 - a schematic sectional view through a pump in a detailed view; Fig. 4 - a schematic sectional view of a pump with an insert removed from the bushing and Fig. 5 - a schematic sectional view of a pump with an insert removed from the bushing in a detailed view.

[0037] In the Fig. 1 shows a pump 10 for conveying a pumped medium, designed as a screw spindle. The pump 10 has a housing 18 with an outer wall on which an inlet 12 with an inlet connection 13 and an outlet 14 with an outlet connection 15 are arranged. In the example shown, the inlet 12 is arranged on the side of the housing 18, and the outlet 14 is arranged on top. An insert 50 is inserted obliquely from above into the housing 18.

[0038] Fig. 2 shows a sectional view through the pump 10 of the Fig. 1. Within the housing 18, two transport elements 30 in the form of screw spindles are arranged, forming a pair of screw spindles, which are rotatably mounted in a conveyor housing 20. The conveyor housing 20 is arranged in the housing 18 within an inner shell 21 or an inner wall and an outer wall 17 of the housing 18. In the illustrated embodiment, the transport elements 30 are designed as two-spindle, two-flow screw spindles. In the illustrated embodiment, the flow direction runs from the outside to the center of the transport elements 30.

[0039] The conveying medium is guided through the inlet 12 into the suction chamber 16, which in the example shown is formed between the outer wall 17 and the inner casing 21 and surrounds the conveying housing 20 enclosing the transport elements 30. From the outside, the conveying medium is guided perpendicular to the image plane on both sides into the center of the transport elements 30 and there reaches the pressure chamber 22. The transport elements 30 are arranged in a so-called liner, which is inserted into the conveying housing 20. From the pressure chamber 22, the conveying medium reaches the outlet 14. In an upper region, the conveying housing 20 has an opening 24 into which a bushing 60 is inserted. In addition, the bushing 60 is inserted into an opening 19 of the housing 18, which is arranged essentially coaxially to the opening 24 of the conveying housing 20. The bushing 60 can be fastened in the conveying housing 20, for example, by pressing in, screwing in, or welding.Alternatively, it is possible to form the bushing 60 in one piece with the conveyor housing 20. In the example shown, the bushing 60 projects through the housing 18 from the outer wall 17 through the suction chamber 16 and the inner casing 21 into the conveyor housing 20 and forms a recirculation line 40 via which the conveying medium is fed from the pressure chamber 22 to the suction chamber 16. A replaceable insert 50 with a defined, constant flow cross-section 52 is arranged in the recirculation line 40. In the example shown, the insert 50 is inserted into the bushing 60 and closes the outer wall 17. It is also possible to insert the insert 50 directly into an opening 24 in the conveyor housing 20. The predetermined, constant flow cross-section 52 of the insert 50 is, in the example shown, the smallest flow cross-section of the recirculation line 40.

[0040] The effective delivery rate of the pump 10 at a predetermined speed of the transport elements 30 is permanently determined by the predetermined, fixed flow cross-section 52, in particular at a defined differential pressure and a defined viscosity of the pumped medium. At a predetermined speed of the transport element 30, a continuous, constant loss volume flow is established in the recirculation line 40 as a function of the predetermined, fixed flow cross-section 52. By inserting an insert 50 with a suitable flow cross-section 52, the effective delivery rate of the pump 10 can thus be adjusted to a desired value. This enables simple and precise adjustment of the delivery rate of the pump 10 at a predetermined speed of the transport elements 30 without requiring disassembly of the pump 10.

[0041] Fig. 3 shows a detailed view of the sectional view from Fig. 2. The bushing 60 has a longitudinal bore 62 into which the insert 50 is inserted. In the example shown, the insert 50 is designed as a screw-in bolt and has a longitudinal bore 54 in the form of a blind hole, which is fluidically connected to the longitudinal bore 62 of the bushing 60 and forms the predetermined, fixed flow cross-section 52. In addition, the insert 50 has a transverse bore 56, which is fluidically connected to the longitudinal bore 54 of the insert 50 and a transverse bore 64 of the bushing 60. The longitudinal bore 54 of the insert 50 and the longitudinal bore 62 of the bushing 60 are arranged essentially coaxially to one another. The transverse bore 56 of the insert 50 and the transverse bore 64 of the bushing 60 are also arranged essentially coaxially to one another. In addition, the transverse bore 64 of the bushing 60 has a larger diameter than the transverse bore 56 of the insert 50.

[0042] In the example shown, the bushing 60 and the insert 50 together form the recirculation line 40. During the recirculation, the conveying medium flows from the pressure chamber 24 via the longitudinal bore 62 of the bushing 60 into the longitudinal bore 54 of the insert 50. From there, the conveying medium flows via the transverse bore 56 of the insert 50 into the transverse bore 64 of the bushing 60 and finally into the suction chamber 16.

[0043] The bushing 60 is designed to correspond to the openings 19, 24. In the example shown, the bushing has, for example, an outer diameter that essentially corresponds to an inner diameter of the openings 19, 24. In addition, the insert 50 has an outer diameter 57 that essentially corresponds to an inner diameter 63 of the longitudinal bore 62 of the bushing 60. A sealing element 70 in the form of an O-ring is arranged on the outside of the insert 50, which prevents or at least reduces a leakage of pumped medium between the outer diameter 57 of the insert 50 and the inner diameter 63 of the bushing 60. A further sealing element 72 in the form of a sealing disk is arranged between a head of the insert 50 and an upper side of the bushing 60.

[0044] If a different delivery rate of the pump 10 is desired at a predetermined speed of the transport elements 30, the insert 50 can be replaced with another insert having a different predetermined, fixed flow cross-section, which is dimensioned such that the effective delivery rate of the pump 10 at a predetermined speed of the transport elements 30 corresponds to the desired delivery rate at the predetermined speed of the transport element 30. Alternatively, the insert 50 can be remachined accordingly so that it has a predetermined, fixed flow cross-section 52, which is dimensioned such that the effective delivery rate of the pump 10 at a predetermined speed of the transport elements 30 corresponds to the desired delivery rate at the predetermined speed of the transport element 30.

[0045] The Fig. 4 shows a sectional view of the pump 10 in a state in which the insert 50 has been removed from the bushing 60. In this removed state, the insert 50 can be reworked, for example, by drilling out the longitudinal bore 54 so that it has a larger, predetermined, fixed flow cross-section 52. The insert 50 can then be reinserted into the bushing 60.

[0046] Fig. 5 shows a detailed view of the sectional view from Fig. 4. The insert 50 has an external thread 58 which is designed to correspond to an internal thread 66 of the bushing 60. List of reference symbols 10 Pump 12 Entrance 13 inlet nozzles 14 Outlet 15 outlet nozzles 16 Suction chamber 17 Exterior wall 18 housings 19 Opening 20 conveyor casings 21 inner jacket 22 Printing room 24 Opening 30 Transport element 40 Recirculation line 50 use 52 predetermined, unchanging flow cross-section 54 Longitudinal bore 56 cross hole 57 outer diameter 58 external thread 60 socket 62 Longitudinal bore 63 inner diameter 64 cross hole 66 internal threads 70 Sealing element 72 Sealing element QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2014 / 019687 A2

[0005]

Claims

[1] Pump (10) for conveying a conveying medium with a suction-side inlet (12), a pressure-side outlet (14), a suction chamber (16), a conveying housing (20) with a pressure chamber (22) and a transport element (30) rotatably mounted in the conveying housing (20) for conveying the conveying medium from the suction chamber (16) into the pressure chamber (22) and with a recirculation line (40) via which the conveying medium is fed from the pressure chamber (22) to the suction chamber (16), characterized by that a replaceable insert (50) with a fixed flow cross-section (52) is arranged in the recirculation line (40). [2] Pump (10) according to one of the preceding claims, characterized by that the insert (50) is designed as a screw-in, clamp-in or insertable bolt. [3] Pump (10) according to one of the preceding claims, characterized bythat the insert (50) is inserted into an opening (24) of the conveyor housing (20) and / or into a bushing (60) inserted into the opening (24). [4] Pump (10) according to claim 3, characterized by that the bushing (60) is designed to correspond to the opening (24) and the insert (50) is designed to correspond to the bushing (60). [5] Pump (10) according to claim 3 or 4, characterized by that the bushing (60) extends through the suction chamber (16). [6] Pump (10) according to claim 3, characterized by that the insert (50) is designed to correspond to the opening (24). [7] Pump (10) according to one of the preceding claims, characterized by that the insert (50) has a longitudinal bore (54) and a transverse bore (56) which are fluidically connected to one another, wherein the conveying medium passes from the pressure chamber (22) via the longitudinal bore (54) into the insert (50) and via the transverse bore (56) from the insert (50) to the suction chamber (16). [8] Pump (10) according to one of the preceding claims, characterized by that the constant flow cross-section (52) of the insert (50) is the smallest flow cross-section of the recirculation line (40). [9] Pump (10) according to one of the preceding claims, characterized by that a sealing element (70, 72), in particular an O-ring or a sealing strip, is arranged on the insert (50). [10] Method for adjusting the delivery rate of a pump (10) for conveying a conveying medium, having a suction-side inlet (12), a pressure-side outlet (14), a suction chamber (16), a conveying housing (20) with a pressure chamber (22) and a transport element (30) rotatably mounted in the conveying housing (20) for conveying the conveying medium from the suction chamber (16) into the pressure chamber (22) and having a recirculation line (40) via which the conveying medium is supplied from the pressure chamber (22) to the suction chamber (16), comprising the steps: a) determining the effective delivery rate of the pump (10) at a predetermined speed of the transport element (30), b) determining the deviation of the effective delivery rate of the pump (10) at the predetermined speed of the transport element (30) from a predetermined delivery rate at the predetermined speed of the transport element (30) and c) inserting an insert (50) with a fixed flow cross-section (52) into the recirculation line (40), wherein the fixed flow cross-section (52) of the insert (50) is dimensioned such that the effective delivery rate of the pump (10) at the predetermined speed of the transport element (30) corresponds to the predetermined delivery rate at the predetermined speed of the transport element (30). [11] Method according to claim 10, characterized bythat the determination of the effective delivery rate of the pump (10) takes place at a defined viscosity of the pumped medium and / or a defined differential pressure.

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