Pump unit and method for monitoring the liquid situation in a seal assembly in a pump unit

Abstract

Pump unit comprising an electric drive motor (2) and at least one impeller connected to the drive motor (2) via a shaft (14), wherein the shaft extends between the drive motor (2) and the impeller through at least one sealing arrangement with a liquid reservoir (22), and a method for detecting a change in concentration in a liquid reservoir in a sealing arrangement in a pump unit, wherein at least one concentration sensor (30) for detecting a change in concentration in the liquid reservoir (22) and a second sensor (32) for detecting at least one further parameter of the liquid reservoir (22) are arranged on the liquid reservoir (22), which are connected to an evaluation device (34), and wherein the evaluation device (34) is configured such thatthat it performs an evaluation of at least one measurement value from the concentration sensor (30), taking into account at least one measurement value recorded by the second sensor (32).

Description

[0001] The invention relates to a pump unit and a method for monitoring or detecting a change in concentration in a liquid reservoir in a sealing arrangement in a pump unit.

[0002] In centrifugal pump units with a dry-running electric drive motor, it is necessary to seal the pump chamber with the impeller rotating therein from the drive motor. For this purpose, the drive shaft is passed through a sealing arrangement. It is known to use two spaced-apart seals with a liquid reservoir in between. Such liquid reservoirs can be filled with oil or a glycol-water mixture, for example. If the first seal, facing the pump chamber, fails, the medium to be pumped, for example water, penetrates the liquid reservoir. It is desirable to be able to detect this at an early stage so that the seal can be replaced. Sensors are known for oil reservoirs that can detect water ingress. However, when a glycol-water mixture is used in the liquid reservoir, it is significantly more difficult to detect water ingress.This requires detecting a change in water concentration. Due to changing operating and environmental conditions, this is not always easily possible.

[0003] US 2014 / 0116513 A1 discloses a seal flushing system in which a seal is flushed to prevent the penetration of substances into the seal and to ensure adequate lubrication of the seal. A concentration sensor is arranged in the seal flushing system. However, this system requires a system for circulating the fluid for flushing the seal.

[0004] From WO2017 / 221217, a pump unit with an electric drive motor and at least one impeller connected to the drive motor via a shaft is known, wherein the shaft extends between the drive motor and the impeller through at least one sealing arrangement with a liquid reservoir.

[0005] It is an object of the invention to provide an improved pump unit and a method for monitoring a liquid reservoir in a sealing arrangement of a pump unit, which reliably enable penetrating liquid in a liquid reservoir to be detected.

[0006] This problem is solved by a pump unit having the features specified in claim 1 and by a method for detecting a change in concentration in a liquid reservoir having the features specified in claim 18. Preferred embodiments emerge from the associated subclaims, the following description, and the attached figures.

[0007] The pump unit according to the invention comprises an electric drive motor and at least one impeller connected to the drive motor via a shaft. The shaft extends between the drive motor and the impeller through at least one sealing arrangement. This sealing arrangement has a liquid reservoir. For this purpose, the sealing arrangement has at least two seals, between which the liquid reservoir is designed in the form of a liquid-filled chamber. The liquid reservoir serves to detect leaks and prevent the direct penetration of water into the dry motor compartment. Furthermore, the liquid in the chamber can serve for cooling. In such a configuration, the electric drive motor is preferably designed to run dry. This meansThe sealing arrangement is located between the liquid-filled pump chamber, in which the impeller rotates, and the dry-located electric drive motor. The pump chamber can be filled with water, in particular, if the pump unit is designed to pump water, for example, fresh water or wastewater.

[0008] According to the invention, at least one concentration sensor for detecting a change in concentration in the liquid reservoir is formed on the liquid reservoir. The concentration sensor can, for example, be designed to detect the concentration of a second liquid in a first liquid in the liquid reservoir, in particular the concentration of water in glycol or vice versa. However, other liquid mixtures can also be used, in particular mixtures of more than two liquids. For example, an oil-glycol mixture may optionally contain further additives. The concentration sensor is designed to detect changes in an initially set concentration of the various liquids in the liquid reservoir. The concentration sensor can be designed such that it is immersed in the liquid or detects the concentration non-contact from the outside, e.g. through a partition wall.According to the invention, at least one second sensor for detecting at least one further parameter of the liquid reservoir is further arranged on or in the liquid reservoir. Both the concentration sensor and the at least one second sensor are connected to an evaluation device such that the evaluation device can receive and further process the measured values ​​recorded by the sensors.

[0009] The evaluation device can be integrated into an electronic control or regulating device arranged directly on the pump unit, in particular a control device for controlling or regulating the drive motor. For this purpose, the evaluation device can be arranged, for example, in an electronics housing of the pump unit. However, it is also possible to design the evaluation device as a separate electronic component or to arrange it further away from the sensor device or the pump unit, for example, as a cloud- or network-implemented evaluation device. The evaluation device or parts of the evaluation device could also be integrated directly into the sensor or a sensor housing of the first and / or second sensor. It is also conceivable to distribute the functionality of the evaluation device across multiple electronic units or processors in different components.

[0010] According to the invention, the evaluation device is designed such that it evaluates at least one measured value of the concentration sensor, taking into account at least one measured value detected by the at least one second sensor. This has the advantage that changes in the operating state that influence the measured value of the concentration sensor and can falsify its measurement result can be detected and taken into account or compensated for. The parameter detected by the second sensor can thus be a parameter that characterizes a specific operating state or characterizes changes in the operating states and / or ambient conditions. This makes it possible to compensate for or correct the changes in the measured value of the concentration sensor based on the measured values ​​of the at least one second sensor, thus enabling a more precise concentration measurement.It should be understood that multiple second sensors can also be provided, or a second sensor that measures more than one parameter simultaneously. For example, the second sensor can measure temperature and / or pressure, or alternatively or additionally, vibrations and / or structure-borne sound.

[0011] The at least one second sensor is a temperature sensor or a sensor that detects at least one temperature-dependent parameter. Such a temperature-dependent parameter can be any parameter that is dependent on the temperature, in particular, is proportional to the temperature. Such a temperature-dependent parameter thus enables indirect temperature detection.

[0012] The evaluation device is designed to evaluate at least one measured value from the concentration sensor, taking into account at least one temperature measurement or temperature-dependent parameter detected by the at least one second sensor. In particular, as already described above, the evaluation device is designed to correct or compensate for the measured value from the concentration sensor based on the temperature measurement or temperature-dependent parameter detected by the at least one second sensor. 10 In this way, the temperature influence on the concentration measurement can be eliminated. This correction can be based directly on a detected temperature measurement or on a temperature-dependent parameter, for example, a vibration signal. This results in direct or indirect temperature-dependent compensation.

[0013] The concentration sensor is designed as an optical sensor.

[0014] A first possible consideration of various operating states when detecting concentration changes by the concentration sensor can be achieved by designing the evaluation device such that it only evaluates a measured value from the concentration sensor if the measured value detected by the at least one second sensor, i.e., a temperature measured value detected by the second sensor, is below a predetermined maximum limit, preferably a predetermined maximum temperature limit. This means, for example, that the concentration measurement can be suspended above a certain operating temperature at which reliable measurement results can no longer be expected.

[0015] Alternatively or additionally, the evaluation device can be configured such that it only evaluates a measured value from the concentration sensor if the measured value detected by the at least one second sensor, i.e., a temperature measured value detected by the second sensor, is above a predetermined minimum limit, i.e., preferably above a predetermined minimum temperature limit. This can ensure, for example, that the concentration measurement is completely suspended at temperatures that are too low, at which an error-free measurement result cannot be expected.

[0016] According to one possible embodiment of the invention, the evaluation device is designed such that it outputs an alarm signal on the basis of a measured value detected by the concentration sensor when this at least one measured value or a characteristic value derived from the measured value reaches a predetermined concentration limit value. In addition, it is possible for the evaluation device to output a switching or control signal which can be detected by a control device and used to switch off the pump unit based on this signal in order to prevent further defects. Based on the alarm signal, it can be determined that the seals in the sealing arrangement need to be replaced. In particular, the evaluation device can be designed such that it detects a breakage or damage, for example based on the size of the change in concentration and / or the speed of the change in concentration.can detect the complete destruction of a shaft seal and issues an alarm signal when a break in the shaft seal is detected.

[0017] According to a further preferred embodiment, the evaluation device is designed such that it forms at least one measured value detected by the concentration sensor and one measured value detected by the at least one second sensor, i.e. a characteristic value derived from a temperature measured value. Such a characteristic value can be a concentration measured value corrected for the temperature influence, i.e. a concentration measured value which has been corrected such that a temperature-dependent influence on the measurement result has been eliminated or reduced. On the basis of such a characteristic value, a decision can then be made regarding the condition of the liquid reservoir. In particular, the characteristic value can be compared with a predetermined limit value for the concentration and, if this limit value is exceeded or not reached, an error signal can be output which signals maintenance or repair of the seals.

[0018] Thus, the evaluation device can preferably be configured such that, for example, if the temperature detected by the second sensor is too high and / or too low, it suspends the measured value acquisition or measured value evaluation for the concentration. The evaluation device is further preferably configured such that, if the measured value acquisition or measured value evaluation is suspended, it uses the last measured value recorded before the suspension as the basis for further processing. This means that in such a case, the evaluation device outputs, for example, the last permissible measured value recorded as the concentration value.

[0019] According to a further preferred embodiment, the evaluation device can be designed such that the measured values ​​of the concentration sensor are recorded at different times and an average of the recorded measured values ​​is calculated as a characteristic value. By calculating the average value, short-term fluctuations, which may be due, for example, to changes in the operating state of the pump unit, can be minimized, and only long-term influences can be taken into account in order to determine changes in the fluid supply that may necessitate maintenance or repairs to the seals.

[0020] Particularly preferably, the evaluation device can be designed to form a running average value or an average value over a specific time period as a characteristic value. The specific time period can, for example, be a specific time period back from the current point in time. For example, a running average value can be formed for a specific past time period starting from the current point in time, or a new average value can be formed at regular intervals as a characteristic value. This allows long-term changes in the characteristic value to be recorded, while short-term fluctuations due to the averaging are eliminated.

[0021] According to a further preferred embodiment of the invention, the evaluation device is designed such that it weights the measured values ​​of the concentration sensor when forming the average value as a function of the measured values ​​detected by the at least one second sensor and preferably as a function of the temperature measured values ​​detected by the second sensor and / or as a function of time. For example, concentration measured values ​​in operating states which are expected to result in more precise concentration measurements can be given a higher weighting when forming the average value than measured values ​​in operating states of the pump unit which are expected to result in less precise measurements. The operating states are represented by the measured value detected by the second sensor. In particular, these can be operating states at different temperatures ordifferent temperatures of the liquid reservoir, which are detected directly or indirectly by the second sensor as described above. In this way, concentration measurements in temperature ranges that enable more precise concentration detection can be given a higher weighting than concentration measurements recorded at other temperatures. Furthermore, for example, more recent measurements can be given a higher weighting than measurements taken further back. In addition, temporal recording is also possible in such a way that if, for example, measurement recording or evaluation is suspended due to the temperature being too high or too low, the last measurement value before the suspension is used. At the same time, a warning or information signal can be issued if necessary to indicate that no correct measurement could be carried out for a longer period of time.

[0022] Particularly preferably, the evaluation device can be designed such that measured values, i.e. concentration measured values, which are recorded at a lower temperature are given a higher weighting when calculating the average value than measured values ​​which are recorded at a higher temperature. This is done, for example, according to a linear function or an inverse sigmoid function. However, other mathematical functions can also be used to achieve this. In principle, for example, monotonically decreasing functions can be used in certain temperature intervals, such as the aforementioned linear functions and inverse sigmoid function. However, it is also possible to use monotonically increasing functions in certain temperature ranges, in particular at very low temperatures which are close to the freezing point.Thus, a monotonically decreasing function can be used preferably in a higher temperature range and a monotonically increasing function in a lower temperature range.

[0023] The higher weighting of measured values ​​recorded at low temperatures is particularly advantageous when using an ultrasonic sensor, since at low temperatures, changes in concentration lead to a greater change in the speed of sound through the medium, resulting in greater measurement accuracy. At higher temperatures, the speed differences become smaller, so greater measurement inaccuracies can occur in these ranges.

[0024] Alternatively or additionally, the evaluation device can comprise a neural network for evaluating the at least one measured value. Such a neural network has the advantage of enabling a learning evaluation that continuously adapts to changes in operating states and environmental conditions, allowing the evaluation of the measured value from the concentration sensor to be continuously improved and its accuracy increased.

[0025] According to one possible embodiment of the invention, the concentration sensor and the at least one second sensor can be integrated into a single sensor assembly. This applies in particular if the concentration sensor is an ultrasonic sensor and the at least one second sensor is a temperature sensor. This creates an integrated sensor assembly that can be easily integrated into a pump unit as a whole. In particular, it is also possible to use common electrical connections for both the concentration sensor and the at least one second sensor and, if necessary, to also transmit data via common lines.

[0026] According to a further possible embodiment of the invention, at least one third sensor is provided which is designed to detect an operating state of the pump unit. In particular, this at least one third sensor can be designed such that it detects whether the pump unit is in operation or not. For this purpose, the at least one third sensor can be, for example, a vibration or structure-borne sound sensor. The operating state can be easily detected from a vibration or structure-borne sound signal, and in particular whether the pump unit is switched on or off. The evaluation device is preferably designed such that it evaluates the signal from the concentration sensor only in predetermined operating states, for example when the pump unit is switched off. This can improve the measurement result. For example, air bubbles can occur in the liquid reservoir during operation, which falsify the measurement result.This can be detected by arranging a third sensor in the manner described, so that, for example, the evaluation of a signal from the concentration sensor only takes place in those operating conditions in which no impairment of the measurement result is to be expected.

[0027] As described above, the liquid reservoir is preferably filled with a liquid mixture containing oil or glycol. In particular, the liquid mixture can contain a mixture of glycol and water. The concentration sensor and the evaluation device are preferably designed to detect the water concentration in the liquid reservoir, so that water penetration can be detected and a warning message can be generated if the seal facing the pump chamber becomes leaky.

[0028] The pump unit is particularly preferably a water pump unit, and more preferably a wastewater pump unit. Such pump units can be designed as submersible pumps, and it is important that the motor compartment, in which the dry-running electric drive motor is located, is reliably sealed.

[0029] According to a further possible embodiment, the evaluation device is designed such that, based on the evaluation of the measured values ​​of the concentration sensor, it calculates or predicts a period of time until the next maintenance of the pump unit is due. Maintenance is understood to mean, for example, the replacement of a seal, i.e., a shaft seal. The evaluation device or a control device connected to the evaluation device can estimate the time for the next maintenance. This can be done based on an extrapolation based on the previously recorded measurements of the concentration sensor. For example, starting from essentially constant measured values, there may be a sudden increase, which indicates that the seal needs to be replaced in the near future. Here, an exponential trend can be present, which can be taken into account by the evaluation device and a connected control device.

[0030] In addition to the described pump unit, the invention further relates to a method for detecting a concentration change in a liquid reservoir in a sealing arrangement in a pump unit, in which at least one measured value from a concentration sensor arranged on the liquid reservoir is evaluated as a function of the temperature or a temperature-dependent parameter of the liquid reservoir. In this way, in particular, a temperature influence on the measurement result of a concentration sensor can be compensated. This can be done in the manner described above with reference to the pump unit. With regard to preferred method steps, reference is made to the preceding description of the pump unit. Method sequences described therein or method sequences resulting from the design of the pump unit are also preferably the subject of the method according to the invention.

[0031] Particularly preferably, in the method according to the invention, the evaluation of at least one measured value from the concentration sensor is suspended when the temperature of the liquid reservoir is above an upper limit or below a lower limit. This prevents measured values ​​recorded under ambient conditions that do not allow for accurate measurement from being taken into account in the concentration determination.

[0032] Particularly preferably, in the method according to the invention, an average value is calculated from a plurality of measured values ​​from the concentration sensor during the evaluation, wherein the individual measured values ​​are further preferably weighted differently depending on a further parameter and preferably depending on the respectively detected temperature and / or depending on the time. In particular, measured values ​​recorded at lower temperatures, as described above with reference to the pump unit, can be given a higher weighting.

[0033] The invention is described below by way of example with reference to the accompanying figures, which show: Fig. 1 a perspective view of a pump unit according to the invention, Fig. 2 a sectional view of the drive motor of the pump unit according to Fig. 1 , Fig. 3 an enlarged sectional view of the sealing arrangement on the drive motor according to Fig. 2 , Fig. 4 schematically shows the concentration measurement by means of ultrasound, Fig. 5 the speed of sound in the liquid reservoir as a function of the temperature for different concentrations, and Fig. 6 schematically shows the sequence of a preferred embodiment of the method according to the invention.

[0034] The pump unit according to the invention, which is exemplified in Figuren 1 and 2is shown, is designed as a submersible pump unit. The pump unit has, in a known manner, an electric drive motor 2 with an attached pump housing 4. The pump housing 4 has an inlet opening 6 and a radial pressure port 8 on its underside. At the axial end of the drive motor 2 facing away from the pump housing 4, the drive motor 2 has a terminal box or an electronics housing 10, in which control and regulating electronics for the drive motor 2 can be arranged and / or the electrical connection to a connecting line 12 for the power supply can be established.

[0035] The pump housing 4 contains, in a known manner, a pump chamber in which an impeller (not shown here) rotates. The impeller is connected in a rotationally fixed manner to the drive shaft or shaft 14 of the drive motor 6. In the drive motor 2, the shaft 14 is connected in a rotationally fixed manner to the rotor 16 of the drive motor, which rotates in a known manner inside the stator 18. The drive motor 6 is designed as a dry-running motor, i.e. the interior of the drive motor 2 is completely sealed off from the pump chamber inside the pump housing 4, for which purpose the shaft 14 is passed through a sealing arrangement 20. The sealing arrangement 20 has a liquid reservoir 22 inside a chamber delimited by a sealing housing 24. The sealing arrangement 20 also has two seals 26 and 28, which are designed as shaft seals and through which the shaft 14 is passed in a sealing manner.The seal 26 forms a first seal which faces the pump housing 4, while the seal 28 forms a second seal which faces the drive motor 2. The liquid reservoir 22 is located between the first seal 26 and the second seal 28. If the first seal 26 should fail, liquid from the pump housing 4 penetrates into the interior of the liquid reservoir 22, which can be detected. As expected, the first seal 26 will wear out sooner than the second seal 28, whereby the wear of the seal can be detected before liquid from the liquid reservoir 22 penetrates into the interior of the drive motor 2. The structure of the liquid reservoir 22 is explained in more detail below with reference to . Fig. 3 described.

[0036] The liquid reservoir 22 can preferably be filled with a liquid mixture containing oil or glycol, in particular with a glycol-water mixture. In addition to glycol and water, the mixture can also contain further additives. When water penetrates the liquid reservoir 22 from the pump chamber inside the pump housing 4 through the first seal 26, the glycol-water concentration in the liquid reservoir 22 changes. This is detected by a concentration sensor 30, which is inserted into the seal housing 24 of the seal arrangement 20. The concentration sensor 30 extends into the interior of the chamber in which the liquid reservoir 22 is located. In addition, a second sensor 32, which in this case is designed as a temperature sensor, is arranged on the seal housing 24.However, the second sensor 32 can also be designed as a combined sensor that detects multiple parameters, such as temperature and pressure and / or vibrations. Thus, as shown in . Figur 3 As shown, a vibration sensor 33 can be integrated into the second sensor as a third sensor. The vibration sensor 33 serves to detect whether the pump unit is in operation or not. Both the concentration sensor 30 and the second sensor 32 are connected to an evaluation device 34. The output signals of the vibration sensor 33 are also evaluated by the evaluation device 34 in order to, for example, suspend the evaluation of the other sensor in the event of excessive vibrations. The evaluation device 34 can be part of a control or regulation electronics 36 inside the electronics housing 10 (see Fig. 2 ), which controls the drive motor 2.

[0037] In this embodiment, the concentration sensor 30 is designed as an ultrasonic sensor, as can be seen from Fig. 4 The concentration sensor 30 has a transmitting / receiving unit 38, which transmits an ultrasonic signal into the interior of the liquid reservoir 22 toward an opposite wall 40. The signal is reflected at the wall 40 and sent back to the transmitting / receiving unit 38, where the signal is received again. The transmitting / receiving unit 38 is connected to the evaluation device 34, which can detect the signal propagation time of the ultrasonic signal between the transmitting / receiving unit 38 and the wall 40. The speed of sound in the liquid reservoir 22 changes depending on the concentration, so that changes in the concentration can be detected by the evaluation unit 34 from the propagation time and thus the speed of the signal in the liquid reservoir 22. The transmitting / receiving unit 38 can, for example, be designed as a piezo element.

[0038] In Fig. 5 Signal curves for the signal velocity within the liquid reservoir 22 are shown for four different concentrations conc0, concl, conc2 and conc3. Fig. 5 the speed u is plotted against temperature T. It can be seen that the speed differences between the individual concentrations decrease with increasing temperature T. This means that the measurement accuracy of the concentration decreases with increasing temperature. Above a temperature limit value Tg, an accurate measurement is no longer possible. Therefore, the invention provides that the evaluation device 34 suspends the evaluation of the measurement result of the concentration sensor 30, preferably when the temperature Tg is exceeded. A wastewater pump is generally not operated continuously but in intervals. During operation, the temperature rises. When the pump is then switched off again, the temperature drops again, so that during operation it may regularly happen that the temperature limit value Tg is exceeded, but then falls below it again. The concentration measurement orThe evaluation of the measured value of the concentration sensor 30 is then carried out by the evaluation device 34 only for measurements at temperatures below the temperature limit value Tg.

[0039] The concentration determination in the liquid reservoir 22 can be carried out by the evaluation device 34, for example, based on Fig. 6described manner. As input variables, a current concentration C i is detected by the concentration sensor 30 and a current temperature T i is detected by the temperature sensor 32. In step S1, a check is made as to whether the current temperature value T is below a limit value T thres (corresponds to T g ). If this is the case (Y), in step S2 a corrected concentration value C out is determined as a function of the measured concentration values ​​C i , the measured temperature values ​​T i and the time ti. For example, the concentration C out can be determined as a weighted average value of a large number of concentrations C i measured over a longer period of time, in particular as a running average. The weighting can be time- and / or temperature-dependent. In particular, the weighting is preferably carried out in such a way that measurements at low temperatures are given a higher weighting than measurements at higher temperatures.This can be done according to a linear function or an inverse sigmoid function or other suitable mathematical function.

[0040] If it is determined in step S1 that the temperature T i is above the set temperature limit value T thres (N), a check is carried out in step S3 as to whether the period t since the last determination of a concentration value C out is less than a predetermined interval t intervall. If this is the case (Y), C out is set to the last determined value in step A1. If it is determined in step S3 that the time interval t is equal to or greater than the predetermined interval t intervall (N), the concentration value C out is set to the last determined value in step A2 and at the same time a warning message is issued that no current measurement or concentration determination is possible.

[0041] Alternatively, the determination of the concentration C out (estimated or corrected concentration) based on the temperature T i and the measured concentration value C i could also be performed in another way, for example, using a neural network. Such a neural network could adapt to changes in the ambient and operating conditions and, in a learning manner, adjust the correction of the measured concentration value C i depending on the temperature.

[0042] Other algorithms or methods can also be used to correct or adjust the concentration measurement values ​​C i depending on the temperature in order to reduce or eliminate the temperature influence from the concentration measurement. List of reference symbols

[0043] 2- Drive motor 4- Pump housing 6- Inlet opening 8- Pressure nozzle 10- Electronics housing 12- Connecting cable 14- Shaft 16- Rotor 18- Stator 20- Seal arrangement 22- Liquid reservoir 24- Seal housing 26- First seal 28- Second seal 30- Concentration sensor 32- Second sensor / Temperature sensor 33Third sensor / Vibration sensor 34- Evaluation device 36- Control electronics 38- Transmitting / receiving unit 40- Wall T g , T thres - Temperature limit t- Time T- Temperature C- Concentration

Claims

1. A pump assembly with an electrical drive motor (2) and with at least one impeller which is connected to the drive motor (2) via a shaft (14), wherein the shaft extends between the drive motor (2) and the impeller through at least one seal arrangement (20) with a fluid reservoir (22), wherein the seal arrangement (20) comprises at least two seals (26, 28) between which the fluid reservoir (22) in the form of a chamber which is filled with fluid is formed, characterised in that at least one concentration sensor (30) in the form of an optical sensor for detecting a concentration change in the fluid reservoir (22) and at least one second sensor (32) for detecting at least one further parameter (22) of the fluid reservoir (22) are arranged on the fluid reservoir (22), wherein the second sensor is a temperature sensor (32) or a sensor which detects at least one temperature-dependent parameter, the concentration sensor (30) and the second sensor (2) are connected to an evaluation device (34), and that the evaluation device (34) is designed in a manner such that it carries out an evaluation of at least one reading of the concentration sensor (30) whilst taking into account at least one reading which is detected by the second sensor (32).

2. A pump assembly according to claim 1, characterised in that the evaluation device (34) is designed in a manner such that it only carries out an evaluation of a reading of the concentration sensor (30) when temperature reading which is detected by the at least one second sensor (32) lies below a defined maximal limit value.

3. A pump assembly according to claim 1 or 2, characterised in that the evaluation device (34) is designed in a manner such that it only carries out an evaluation of a reading of the concentration sensor (30) when the temperature reading which is detected by the at least one second sensor (32) lies above a defined minimal limit value.

4. A pump assembly according to one of the preceding claims, characterised in that the evaluation device (34) is designed in a manner such that given the skipping of a reading acquisition or reading evaluation, it takes the last reading which was detected before the skipping as a basis for the further processing.

5. A pump assembly according to one of the preceding claims, characterised in that the evaluation device (34) is designed in a manner such that it outputs an alarm signal on the basis of a reading which is detected by the concentration sensor (32) if this at least one reading or a characteristic value which is derived from the reading reaches a predefined concentration limit value.

6. A pump assembly according to one of the preceding claims, characterised in that the evaluation device (34) is designed in a manner such that it forms at least one characteristic value which is derived from the reading of the concentration sensor (30) and from a temperature reading which is detected by the at least one second sensor (32).

7. A pump assembly according to one of the preceding claims, characterised in that the evaluation device (34) is designed in a manner such that it detects readings of the concentration sensor (30) at different points in time and forms an average value of the detected readings as a characteristic value.

8. A pump assembly according to claim 7, characterised in that the evaluation device (34) is designed in a manner such that it forms a rolling average value or an average value over a certain time span, as a characteristic value.

9. A pump assembly according to claim 7 or 8, characterised in that the evaluation device (34) is designed in a manner such that on forming the average value, it weights the readings of the concentration sensor (30) in dependence on the readings which are detected by the second sensor (32) and preferably in dependence on the temperature readings which are detected by the at least one second sensor (32) and / or in dependence on the time.

10. A pump assembly according to claim 9, characterised in that the evaluation device (34) is designed in a manner such that on forming the average value, readings which are detected at a lower temperature are weighted higher than readings which are detected at a higher temperature, wherein this is preferably effected according to a linear function or an inverse Sigmoid function.

11. A pump assembly according to one of the preceding claims, characterised in that the evaluation device (34) comprises a neuronal network for evaluating the at least one reading.

12. A pump assembly according to one of the preceding claims, characterised in that the concentration sensor (30) and the at least one second sensor (32) are integrated in a sensor construction unit.

13. A pump assembly according to one of the preceding claims, characterised by at least one third sensor (33) which is designed to detect an operating state of the pump assembly.

14. A pump assembly according to one of the preceding claims, characterised in that the fluid reservoir (22) is filled with a fluid mixture which contains oil or glycol.

15. A pump assembly according to one of the preceding claims, characterised in that the concentration sensor (30) and the evaluation device (34) are designed for detecting the concentration of water in the fluid reservoir.

16. A pump assembly according to one of the preceding claims, characterised in that the pump assembly is a waste water pump assembly.

17. A pump assembly according to one of the preceding claims, characterised in that the evaluation device (34) is designed in a manner such that it computes a time interval until the next due maintenance of the pump assembly on the basis of the evaluation of the readings of the concentration sensor (30).

18. A method for detecting a concentration change in a fluid reservoir (22) in a seal arrangement (20) in a pump assembly, said seal arrangement comprising two seals (26, 28), between which the fluid reservoir (22) in the form of a chamber which is filled with fluid is formed, concerning which method at least one reading of a concentration sensor (30) in the form of an optical sensor which is arranged on the fluid reservoir (22) is evaluated in dependence on the temperature of or on a temperature-dependent parameter of the fluid reservoir (22).

19. A method according to claim 18, characterised in that the evaluation of the at least one reading is skipped if the temperature lies above an upper limit value or below a lower limit value.

20. A method according to claim 18 or 19, characterised in that on evaluation, an average value is formed from a plurality of readings of the concentration sensor (30), wherein the individual readings are weighted differently depending on a further parameter and preferably in dependence on the respectively detected temperature and / or in dependence on time.

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