Positive displacement pump and pump system

Abstract

To provide a positive displacement pump capable of analyzing a conveyance material.SOLUTION: A positive displacement pump for conveying a material to be conveyed includes a measurement assembly including at least one measurement channel capable of passing and running at least a part of the material to be conveyed by the pump. The at least one measurement channel has a noncircular cross section; the measurement assembly including a pressure sensor assembly detects a pressure acting at a position separated in the circulation direction of the at least one measurement channel when the at least a part of the material to be conveyed by the pump flows through the at least one measurement channel. The positive displacement pump and a control unit are disclosed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a positive displacement pump and a pump system comprising such a positive displacement pump.

Background Art

[0002] Positive displacement pumps, such as eccentric screw pumps, rotary piston pumps, screw spindle pumps, or hose pumps, are intended to convey a material to be conveyed (conveyance material). The conveyance material is a freely flowing material, in particular a liquid or a viscous material (low-viscosity or high-viscosity). Examples of such conveyance materials include process liquids used during the manufacture of workpieces, such as cooling liquids, oils, varnishes, and paints. Further examples may include waste water and sludge.

[0003] Conventional positive displacement pumps can convey the conveyance material but cannot analyze it. In particular, the viscosity of the conveyance material can be important in certain scenarios. In the case of known solutions, in order to analyze the conveyance material, a sample of the conveyance material is taken while the positive displacement pump is stopped. The sample is then analyzed in a laboratory, for example, to determine the viscosity of the conveyance material. This approach is laborious and time-consuming.

Summary of the Invention

Problems to be Solved by the Invention

[0004] From the above-described background circumstances, an object of the present invention is to provide a positive displacement pump that enables analysis of the conveyance material.

Means for Solving the Problems

[0005] According to the present invention, there is provided a positive displacement pump according to claim 1 and a pump system according to claim 10.

[0006] A positive displacement pump for conveying a material to be conveyed comprises a measurement assembly having at least one measurement channel through which at least a part of the material to be conveyed by the pump can flow. At least a part of the conveyed material conveyed by the pump corresponds in particular to a part of the volumetric flow rate of the conveyed material conveyed by the pump. At least a part of the material conveyed by the pump can be referred to as a volumetric flow rate ratio, a volume ratio, or a quantity ratio.

[0007] The at least one measurement channel has a non-circular cross-section. This cross-section is a cross-section perpendicular to the flow direction of the at least one measurement channel. The cross-section can be constant in the flow direction of the at least one measurement channel (e.g., over the entire length of the at least one measurement channel).

[0008] The measurement assembly has a pressure sensor assembly which detects the pressures acting at spaced positions in the flow direction of the at least one measurement channel when at least a part of the material to be conveyed by the pump flows through the at least one measurement channel. These pressures can act outwardly from the inside of the at least one measurement channel. The measurement assembly or / and the pressure sensor assembly can in particular determine the pressure difference between two or more detected pressures.

[0009] This type of positive displacement pump provides for the detection of pressures along a measurement channel having a non-circular cross-section. Since these pressures vary depending on the conveyed material, it is possible to directly analyze the conveyed material with the positive displacement pump. The non-circular cross-section of the measurement channel has proven to be particularly advantageous as it ensures a flow profile in the measurement channel that is favorable for pressure measurement.

[0010] The cross-section of the at least one measurement channel can have at least one straight portion. In this case, the at least one measurement channel can have at least one flat side forming the at least one straight portion in the cross-section.

[0011] At least one straight portion can reach a corner of the cross-section at one of its ends, or can reach each corner of the cross-section at both of its ends. Such corners can form an angle of 10° to 170°, for example 45° to 135°, particularly 90°.

[0012] In one example, the cross-section is polygonal. In this case, each corner can be formed by two of at least one straight portion. The cross-section can be polygonal, in which case each side of the polygon corresponds to one of at least one straight portion.

[0013] The cross-section can be rectangular. In this case, each of the four sides of the rectangular cross-section can correspond to one of at least one straight portion.

[0014] The pressure assembly is configured to detect, for example, the pressure acting from the inside of at least one measurement channel towards the sensor surface (e.g., outwards). For this purpose, the pressure sensor assembly can have a pressure sensor for detecting the pressure acting on the sensor surface. For each pressure to be detected, a separate sensor surface and a separate pressure sensor can be provided.

[0015] The sensor surface can form part of the cross-section of the measurement channel. The sensor surface can be formed substantially flat. The sensor surface particularly forms one of at least one straight portion in the cross-section. Thus, the sensor surface can form a flat portion of the side wall in at least one measurement channel. In an alternative configuration, the sensor surface can be designed to be curved. In this case, it is possible for the sensor surface to form a curved portion of the cross-section. The sensor surface can extend over a part of the length of at least one measurement channel in the flow direction of at least one measurement channel. This type of configuration of the sensor surface can reduce turbulence and flow deflection in the measurement channel and provide a more reliable pressure measurement.

[0016] According to one example, the cross-section has a height that is smaller than the width of this cross-section. In this case, the sensor surface can extend in the width direction of the cross-section. Thus, the sensor surface can extend, in particular, over the entire width of the measurement channel.

[0017] The measurement assembly can have a flow straightener that is arranged upstream of at least one measurement channel in the flow path of the transport material transported by the pump. The flow straightener can be arranged directly in front of at least one measurement channel and can be connected to the measurement channel in particular. The flow straightener can form an inlet opening that is tapered in the flow direction in at least one measurement channel. The inlet opening can be rounded, for example, so as not to form a step in the measurement channel in the flow direction.

[0018] At least one measurement channel or / and the flow straightener can be configured such that a laminar flow profile of the transport material to be transported is ensured in the measurement channel (for example, within a predetermined transport speed range in a positive displacement pump or / and within a predetermined viscosity range of the transport material) in particular in the width direction or / and height direction of at least one measurement channel.

[0019] At least one measurement channel can have a plurality of measurement channels through which at least a part of the transport material to be transported by the pump can flow. These measurement channels are different in particular in their cross-sections. The cross-sections can be different in their surface areas. The cross-sections can be formed in the same geometric shape (for example, rectangular), but can have different (for example, scaled) dimensions with respect to this geometric shape. Thus, it is conceivable that polygons of different sizes with the same side length ratio are provided as cross-sections. The cross-sections (for example, rectangular) of the measurement channels are different in particular in their heights and can have the same width. In this case, the pressure sensor assembly is formed in particular to detect the pressure in each measurement channel.

[0020] The measurement channels of the measurement assembly are, for example, fluidly connected in parallel. In this case, the measurement channels are conveyed by a pump and also differ with respect to at least a part of the conveyance material that can flow through each measurement channel. That is, different volume flow rates with respect to the conveyance material conveyed by the pump can be assigned to each measurement channel.

[0021] The measurement assembly can have components in which each of at least one measurement channel is formed. These components can be integrally formed. The components are formed of, for example, a ceramic material in order to ensure high wear resistance. Alternatively or additionally, the rectifier can be formed of a ceramic material. The measurement channels can be incorporated into the components (for example, by milling, punching, or sawing). It is also conceivable to form the components together with the internal measurement channels. The components are substantially cylindrical and can extend along the flow direction of at least one measurement channel. The components can have recesses that extend radially and are spaced apart from each other in the flow direction in order to receive the pressure sensors of the pressure sensor assembly. Two or more recesses can be provided in each measurement channel. These recesses can be formed as through-holes leading into each measurement channel. In this case, the sensor surface can be part of a pressure sensor fitted into the recess.

[0022] The components can be surrounded by a tubular housing, which can be referred to as a housing tube. The virtual enclosure of the components or / and the housing tube can be formed to be concave-curved in the flow direction. In other words, the components or / and the housing tube can be formed to be bulging. The housing tube can have cooling fins in order to passively control the temperature of the material to be conveyed in the measurement channel. It is possible to provide a heating device or / and a cooling device, and this device is configured to ensure a defined temperature with respect to the housing, the components, or / and the material to be conveyed in the measurement channel.

[0023] The flow directions of the measurement channels can extend parallel to each other. Alternatively or additionally, it is conceivable that the width directions of the cross-sections of the measurement channels extend obliquely to each other. In particular, at least one straight portion of the cross-section of each measurement channel can be assumed to be aligned radially outward with respect to a common axis (for example, the longitudinal axis of the component). The outer sides (for example, the widths) of the cross-sections can each be arranged tangentially based on a virtual circle, or can have the same distance from a reference point (for example, a point on the longitudinal axis of the component).

[0024] According to a second aspect of the present invention, a pump system is provided. This pump system includes a positive displacement pump according to the first aspect of the present invention and a control unit. The control unit is configured to determine the viscosity of the conveyed material or / and the conveying speed (for example, the provided volume flow rate) of the positive displacement pump based on the pressure detected by the pressure sensor assembly.

[0025] The control unit is configured to classify the viscosity as viscoplastic, shear-thinning, shear-thickening, Newtonian, or Bingham. The control unit can be configured to determine whether the material to be conveyed is a material having a shear rate dependent on viscosity or / and whether it is a material having a flow restriction based on the pressure detected by the pressure sensor assembly. For this purpose, the viscosity values of a plurality of measurement channels can be determined, which can also be referred to as viscosity multi-point measurement.

[0026] The control unit can be configured to determine the conveying speed of the positive displacement pump based on the pump speed of the positive displacement pump or / and the pump control signal for the positive displacement pump, in particular based on a pump characteristic curve known for the positive displacement pump, and to determine the viscosity of the conveyed material to be conveyed based on the conveying speed thus determined and the pressure detected by the pressure sensor assembly. This viscosity can also be determined as a function of at least one parameter (for example, shear rate or / and temperature).

[0027] The control unit is configured to perform one or several of the steps of outputting the determined conveying speed value and / or the determined viscosity value, detecting wear of the positive displacement pump based on the determined conveying speed and / or viscosity, detecting slip of the positive displacement pump based on the determined conveying speed and / or viscosity, controlling the positive displacement pump based on the determined conveying speed and / or viscosity, controlling a viscosity adaptation device based on the determined conveying speed and / or viscosity in order to adapt the viscosity of the conveying material to be conveyed, and controlling a processing plant for processing the conveying material to be conveyed based on the determined conveying speed and / or viscosity.

[0028] Hereinafter, the present invention will be described in more detail with reference to the drawings.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0030] FIG. 1 shows a schematic diagram of a pump system 2. The pump system 2 includes a positive displacement pump 4 and a control unit 6 communicably connected to the positive displacement pump 4. The control unit 6 can be mechanically fixed to the pump 4 or provided separately from the pump 4.

[0031] The positive displacement pump 4 can be an eccentric screw pump, but it can also be other types of positive displacement pumps. The positive displacement pump 4 is configured to convey a free-flowing filling material 8, in particular a varnish, an oil, or a suspension (wastewater) from the filling material storage 10 into the filling material receptacle 12.

[0032] The positive displacement pump 4 comprises a measurement assembly 14. In the example shown, the measurement assembly 14 is located in the downstream region of the pump 4. Alternatively, the measurement assembly 14 may be located in the upstream region suggested by reference numeral 13. In any case, the measurement assembly 14 has at least one measurement channel 16 and a pressure sensor assembly 18 including pressure sensors 20, 22. In the example shown, two pressure sensors are provided in the measurement channel 16, but it is also conceivable to provide three, four, or more pressure sensors in the measurement channel 16.

[0033] At least a part of the conveyed material 8 conveyed by the pump 4 can flow through the measurement channel 16. The pressure sensors 20, 22 are spaced apart from each other in the flow direction 24 of the measurement channel 16 (e.g., over a distance L from the center of the sensor to the center of the sensor) and can detect the pressure present at each position inside the measurement channel 16. This pressure can be detected as an absolute pressure or as a differential pressure (e.g., based on a predetermined reference pressure, in particular the atmospheric pressure around the pump 4).

[0034] The measuring assembly 14 can include further sensors, in particular temperature sensors for detecting the temperature of the conveyed material conveyed by the pump 4. It is conceivable that the measuring assembly 14 has one or more temperature sensors in each measuring channel 16 in order to detect the temperature of the conveyed material conveyed through the corresponding measuring channel 16. The temperature measurement values of these temperature sensors can be used to detect shear heating. A heating device and / or a cooling device 7 can be provided which is configured to define the temperature of the housing of the pump system 2, the temperature of the components of the pump system 2, and / or the temperature of the conveyed material within the measuring channel 16.

[0035] The measuring assembly can also have a flow rectifier 23 which is arranged upstream of at least one measuring channel 16 and is intended to bring about a desired flow profile (for example laminar flow) of the conveyed material within the measuring channel 16. In the simplest case, the flow rectifier forms a funnel-shaped inlet of the measuring channel 16 and can in particular be made of a wear-resistant material such as ceramic.

[0036] FIG. 1 further shows an optional viscosity adaptation (regulation) device 26. The viscosity adaptation device 26 can adjust the viscosity of the conveyed material, for example, by adding a diluent or a thickener, by controlling the temperature of the conveyed material, and / or by adapting the particle size distribution in the conveyed material (for example by grinding the particles contained in the conveyed material). Furthermore, an optional processing plant 28 is shown, which is configured to use the conveyed material 8 conveyed by the pump 4 in a manufacturing process and / or a processing process. This plant can be, for example, a coating plant for applying varnish, in particular for manufacturing multilayer battery cells.

[0037] The control device 6 is configured to determine the viscosity of the conveyed material and / or the conveying speed of the positive displacement pump based on the pressure detected by the pressure sensor assembly. The viscosity can be determined based on the pressure difference of the pressure detected by the pressure sensors 20, 22 while flowing through the measurement channel 16, based on the volume flow rate flowing through the measurement channel 16, and based on the known shape of the measurement channel. In the illustrated example, the total volume flow rate of the conveyed material conveyed by the pump 4 is guided to pass through the measurement channel 16. Therefore, the volume flow rate through the measurement channel 16 is directly obtained from the conveying speed of the positive displacement pump. The control unit 6 can be configured to determine this conveying speed based on the pump speed of the positive displacement pump 4 and / or the pump control signal of the positive displacement pump 4, in particular based on the known pump characteristic curve for the positive displacement pump 4. In particular, under the assumption that the conveyed material is not compressible, there is no need to separately measure the volume flow rate to determine the viscosity.

[0038] Based on the determined conveying speed and / or the determined viscosity, the control unit 6 can output the corresponding value (e.g., to a screen or a data processing device). The determined conveying speed and / or viscosity can also be further processed by the control unit 6.

[0039] For example, if it is assumed that the viscosity is constant but the pressure values detected by the sensors 20, 22 change over a specific period, it can be concluded that the conveying speed of the conveying pump has decreased. If the pump 4 was controlled by the same control signal (e.g., pump frequency) during this period, the control unit 6 can conclude that the pump 4 is worn and / or the slip of the pump 4 has increased. Subsequently, the control unit 6 can output a warning or readjust the pump 4 until the pressure value again falls within the desired range (this range corresponds to the desired volume flow rate at a known constant viscosity).

[0040] In contrast, if it can be assumed that the conveying speed determined for the pump 4 is constant while the pressure values detected by the sensors 20, 22 vary over a specific period, it can be concluded that the viscosity of the conveyed material 8 is changing. In particular, in this case, the temperature of the conveyed material 8 can be considered in order to determine, for example, whether the change is solely due to temperature or whether other causes are present. Subsequently, the control unit 6 can output a warning or control the viscosity adaptation device 26 in order to adapt the viscosity to the desired value. Alternatively or additionally, the control unit 6 can inform the processing plant 28 of the viscosity change so that the manufacturing process can be adapted accordingly.

[0041] The pressure values can be analyzed over time, in particular to detect unwanted pulsations after the pump 4 has been switched on. The control unit 6 can readjust the pump 4 as required in order to minimize such pulsations. In the case of an eccentric screw pump, the control or readjustment of the pump 4 can include, for example, adapting the position of the stator in the pump 4.

[0042] As described above, during operation of the pump 4, i.e., when the measurement channel 16 is flowing, a pressure drop occurs in the flow direction of at least one measurement channel 16. The pressure drop can occur linearly, in particular along the flow direction. Thus, the two pressure sensors 20, 22 detect different magnitudes of pressure caused by the conveyed material 8 in the measurement channel 16. In particular, the viscosity of the conveyed material 8 can be determined from this pressure difference. In this case, the following formula applies:

Equation

[0043] JPEG2025093877000003.jpg37166

[0044] FIG. 2 shows a perspective view of an exemplary measurement assembly 14. In the illustrated example, the measurement assembly 14 has a substantially cylindrical component 30 in which a measurement channel 16 is formed. Both the measurement channel 16 and the component 30 extend along the flow direction 24. In FIG. 2, the component 30 is embedded in the housing tube 32, but this is not necessarily essential.

[0045] FIG. 3 shows a longitudinal sectional view of the exemplary measurement assembly 14 in the flow direction 24. In the illustrated example, there is no housing tube 32, and thus the component 30 is not enclosed. As shown in FIG. 3, it can be seen that each sensor has sensor surfaces 34, 36 that laterally define the measurement channel 16. These sensor surfaces 34, 36 are spaced apart from each other in the flow direction 24 and extend only over a part T1, T2 of the length of the measurement channel 16 in the flow direction 24. In the illustrated example, the sensor surfaces 34, 36 are relatively large compared to the height h of the measurement channel (T1 > h, T2 > h). Thus, a high shear rate can be provided in the measurement channel 16. For example, if a lower shear rate is desired, it is also conceivable to vary the dimensions of the measurement channel 16 (T1 = h or T1 < h; and / or T2 = h or T2 < h). The centers of each sensor surface 34, 36 are offset by a distance L in the flow direction 24.

[0046] At least one measurement channel 16 has a non-circular cross-section 38, in particular a cross-section including one or more straight portions 39. In this case, the sensor surfaces 34, 36 can form one of these straight portions. FIG. 4 shows an example of such a non-circular cross-section 38 of at least one measurement channel 16. In the illustrated example, the cross-section 38 is rectangular and has a height h smaller than the width a. In the width direction of the cross-section 38 of the measurement channel 16, the sensor surfaces 34, 36, which are flat (for example also rectangular or circular), extend over the entire width of the measurement channel 16 and form the upper side of the measurement channel 16.

[0047] In the case of cross-section 38, the following equation is applicable to the channel shape coefficient K of measurement channel 16:

Number

[0048] JPEG2025093877000005.jpg21166

[0049] As described above, when the volumetric flow rate is known, the viscosity can be calculated based on the detected pressure, and when the viscosity is known, the volumetric flow rate can be calculated based on the detected pressure. This also applies to other channel shapes, in which case the channel shape coefficient K may deviate from Equation 3.

[0050] At least one measurement channel 16 can have a plurality of measurement channels 16-1, 16-2…, 16-n. In other words, the measurement assembly 14 can have a plurality of appropriately formed measurement channels 16. The measurement channels can, in particular, have cross-sections 38-1, 38-2…, 38-n that can be different from each other. Thus, for different channel cross-sections, each value of the pressure difference Δp can be determined. From this, for each measurement channel, the corresponding viscosity value in the conveyed material can be determined. By comparing these viscosity values, the control unit 6 can conclude the viscosity that is a function of the shear rate of the conveyed material, and in particular, can determine whether the conveyed material is shear-thinning or shear-thickening.

[0051] Figure 5 shows an example of the arrangement of a plurality of measurement channels 16-a, 16-2, 16-3. All of these measurement channels are formed in the same component 30, and the flow directions extend parallel to each other. In this case, the measurement channels 16-1, 16-2, 16-3 each have rectangular cross-sections 38-1, 38-2, 38-3. Each cross-section has the same width a, but the heights h1, h2, h3 are different.

[0052] Each of the measurement channels 16-1, 16-2, 16-3 is provided with a corresponding pressure sensor having sensor surfaces 34-1, 34-2, 34-3 and 36-1, 36-2, 36-3. Also in this case, each sensor surface forms the upper side of each measurement channel. In this case, the sensor surfaces are aligned radially outwards with respect to the longitudinal axis 38 of the component 30 extending in the flow direction. Thereby, the pressure sensors can be fixed to the component 30 from different directions in order to measure the pressure in channels having different dimensions.

[0053] JPEG2025093877000006.jpg36166

[0054] Needless to say, with respect to the measurement channel 16, instead of three measurement channels, only one, only two, four, or more channels can be provided. These can be connected in parallel as a group, and / or can be connected in series as a group. One or more measurement channels 16 can be arranged upstream of the eccentric screw pump, and one or more measurement channels 16 can be arranged downstream of the eccentric screw pump. Furthermore, it is also conceivable to use a further pump (for example, having a greater conveying capacity) in parallel with the pump 4 in order to convey the material from the filling material storage section 10 into the filling material receptacle 12. The measurement assembly 14 can be arranged outside the pump housing of the positive displacement pump 4, for example in a line system fluidly connected to the positive displacement pump 4. A person skilled in the art can obtain further advantages and modifications from the present disclosure.

Claims

1. A positive displacement pump (4) for conveying the material (8) to be conveyed, a measuring assembly (14) having at least one measuring channel (16, 16-1, 16-2, 16-3) through which at least a portion of the material (8) to be conveyed by the positive displacement pump (4) can flow, a positive displacement pump, wherein the at least one measurement channel (16, 16-1, 16-2, 16-3) has a non-circular cross-section (38, 38-1, 38-2, 38-3), and the measurement assembly (14) includes a pressure sensor assembly (18) that detects pressure acting at spaced positions in a flow direction (24) of the at least one measurement channel (16, 16-1, 16-2, 16-3) when at least a portion of the material (8) to be conveyed by the positive displacement pump (4) flows through the at least one measurement channel (16, 16-1, 16-2, 16-3).

2. 2. The positive displacement pump (4) according to claim 1, wherein a cross section (38, 38-1, 38-2, 38-3) of the at least one measuring channel (16, 16-1, 16-2, 16-3) has at least one straight section (39).

3. 3. A positive displacement pump (4) according to claim 2, wherein the cross sections (38, 38-1, 38-2, 38-3) are polygonal.

4. 4. A positive displacement pump (4) according to claims 2 and 3, wherein a cross section (38, 38-1, 38-2, 38-3) is rectangular, and each of the four sides of the rectangular cross section (38, 38-1, 38-2, 38-3) corresponds to one of the at least one straight line portions (39).

5. 5. The positive displacement pump (4) according to claim 2, wherein the pressure sensor assembly (18) is configured to detect a pressure acting on a sensor surface (34, 36) from inside the at least one measurement channel (16, 16-1, 16-2, 16-3), the sensor surface (34, 36) forming one of the at least one straight portion (39) in the cross section (38, 38-1, 38-2, 38-3) and extending in the flow direction (24) of the at least one measurement channel (16, 16-1, 16-2, 16-3) over a portion of a length of the at least one measurement channel (16, 16-1, 16-2, 16-3).

6. 6. A positive displacement pump (4) according to claim 5, wherein the cross sections (38, 38-1, 38-2, 38-3) have a height (h, h1, h2, h3) which is smaller than a width (a) of the cross sections (38, 38-1, 38-2, 38-3) and the sensor surfaces (34, 36) extend in the width direction of the cross sections (38, 38-1, 38-2, 38-3).

7. 7. The positive displacement pump (4) according to claim 1, wherein the at least one metering channel (16, 16-1, 16-2, 16-3) comprises a plurality of metering channels (16, 16-1, 16-2, 16-3) through which at least a portion of the material (8) to be conveyed by the positive displacement pump (4) can flow, the metering channels (16, 16-1, 16-2, 16-3) differing in their cross-sections.

8. 8. The positive displacement pump (4) according to claim 7, wherein the measurement channels (16, 16-1, 16-2, 16-3) are fluidly connected in parallel and the measurement assembly (14) comprises a component (30) in which each of the measurement channels (16, 16-1, 16-2, 16-3) is formed.

9. 9. A positive displacement pump (4) according to claim 7 or 8, wherein the flow directions (24) of the measuring channels (16, 16-1, 16-2, 16-3) run parallel to one another and / or the width directions of the cross sections (38, 38-1, 38-2, 38-3) of the measuring channels (16, 16-1, 16-2, 16-3) run obliquely to one another.

10. A pump system (2) comprising a positive displacement pump (4) according to any one of claims 1 to 9 and a control unit (6), the control unit (6) being configured to determine the viscosity of a conveying material (8) to be conveyed and / or the conveying speed of the positive displacement pump (4) based on the pressure detected by a pressure sensor assembly (18).

11. 11. The pump system (2) according to claim 10, wherein the control unit (6) is configured to determine a conveying speed of the positive displacement pump (4) based on a pump speed of the positive displacement pump (4) or / and a pump control signal for the positive displacement pump (4), in particular based on a pump characteristic curve known for the positive displacement pump (4), and to determine a viscosity of the conveying material (8) to be conveyed based on the conveying speed thus determined and the pressure detected by the pressure sensor assembly (18).

12. 12. The pump system (2) according to claim 10 or 11, wherein the control unit (6) outputting the determined conveying speed value or / and the determined viscosity value; - detecting wear of the positive displacement pump (4) based on the determined delivery speed and / or viscosity; detecting slippage of the positive displacement pump (4) based on the determined delivery speed and / or viscosity; controlling the positive displacement pump (4) based on the determined delivery speed and / or viscosity; - controlling a viscosity adapting device (26) based on the determined conveying speed and / or viscosity in order to adapt the viscosity of the conveying material (8) to be conveyed; - controlling a treatment plant (28) for treating the conveyed material (8) based on the determined conveying speed and / or viscosity, The pump system is further configured to perform one or more of the following:

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