Method for operating a multi-pump system with dynamic running time adjustment of the pumps, and multi-pump system

Abstract

This invention relates to a method for operating a multi-pump system comprising two or more pumps which convey fluid in a common pressure line, the pumps being operated alternately, so that precisely one of the pumps is active or only some of the pumps are simultaneously active in order to convey fluid, characterised in that the individual running time of each or at least some of the pumps is determined dynamically depending on a varying state of the relevant pumps during operation of the system.

Description

[0001] The invention relates to a method for operating a multi-pump system comprising two or more pumps, in particular centrifugal pumps, which convey fluid into a common pressure line, wherein the pumps are operated alternately, so that exactly one of the pumps is active or only a part of the pumps are active at the same time to convey fluid.

[0002] Multi-pump systems consist of several pumps connected in parallel, which typically deliver the fluid to a common pressure line. One application is in heating systems. In buildings and industrial settings, they are frequently used as dual pumps in redundant operation, meaning that usually only one pump is active at a time. If the active pump fails, the system switches to the remaining pump to ensure a continuous fluid supply. Normally, both pumps should be ready for operation. To keep the operating time of both pumps as equal as possible, they alternate according to a defined cycle. For example, the active pumps might change every 24 hours. In certain special cases, both pumps in the multi-pump system can be operated synchronously, for example, to cover peak loads or to take advantage of the more energy-efficient parallel operation of both pumps.

[0003] Another application for multi-pump systems is pressure boosting systems with several pumps connected in parallel, for example, up to six pumps. Such pressure boosting systems are used, for instance, in waterworks. Due to the highly variable flow rate requirements, the number of synchronously operating pumps can be flexibly adjusted during operation. If one pump fails due to a defect, one of the inactive pumps is activated.

[0004] All the aforementioned multi-pump systems have in common that the pumps are operated alternately during regular operation to ensure even wear. Up to now, this has been done based on fixed cycle times; that is, one or some of the pumps are operated for a fixed active period (e.g., 24 hours), while the remaining pumps remain inactive. After the active period has elapsed, the inactive pumps are started, and the previously running pumps are switched off. A cycle is defined as a time interval after which all pumps have run at least once.

[0005] This approach ensures that all pumps wear out evenly, provided their operating hours were identical when the system was commissioned. However, this process does not account for the case where a pump had to be replaced prematurely, for example, due to a defect. In this case, the pumps in the system will have different degrees of wear, which cannot be adjusted using the previous approach with fixed replacement cycle times.

[0006] US 2020 / 003218 A1 discloses a method and system for determining the real-time flow rate in a wastewater pumping station using analog level sensor technologies. US 2020 / 063741 A1 discloses a special dual-pump unit. EP 3 643 922 A1 discloses a method for optimizing a pumping system. US 6 516 249 B1 discloses a fluid distribution system with a plurality of autonomously controlled valves and pumps interconnected by a data communication network.

[0007] The object of the present invention is to demonstrate an optimized method for the operation of a multi-pump system, by means of which different degrees of wear of the pump can be adapted to one another over the operating period of the system.

[0008] This problem is solved by a method according to the features of claim 1. Advantageous embodiments of the method are the subject of the dependent claims. The problem is also solved by a multi-pump system according to claim 8 and a control system according to claim 9.

[0009] According to the invention, it is proposed to further develop the existing method for operating a multi-pump system such that an individual runtime for at least one pump is dynamically determined depending on a state that varies during the pump's runtime. The core aspect of the invention therefore departs from the rigid runtime interval of the pumps in a multi-pump system and instead proposes to dynamically change the runtime of at least one pump during system operation. Specifically, this dynamic adjustment is to be made depending on a specific operating parameter or state value of the pump. The operating parameter or state value of the pump is a value that changes dynamically during system operation.

[0010] Preferably, the varying pump condition is the number of operating hours already accumulated by the pump and / or the age of the pump. If the number of operating hours is used as the basis for adjusting the runtime, the operating time of the pumps in a multi-pump system can be varied using the method according to the invention in such a way that the pumps ultimately have an identical or at least similar number of operating hours. Based on this, an identical or similar degree of wear can be assumed. This is also possible, at least to a limited extent, if the age of the pump is taken into account.

[0011] By adjusting operating times and / or wear levels, the probability of system failure can be reduced, as this prevents a pump from failing prematurely due to excessive wear. For example, if the number of operating hours or the age of a pump is higher than the operating hours or age of the other pumps in the multi-pump system, it is advisable to reduce the operating time of this pump relative to the remaining pumps, so that its wear level can be adjusted to match the wear level of the other pumps. Alternatively, or in addition to this, the operating time of the remaining pumps can be increased.

[0012] In particular, it is proposed to operate the pumps of the multi-pump system alternately during a defined cycle, with each pump having a definable active duration. For example, during a cycle, each pump is activated at least once for a specified duration, while all or at least some of the remaining pumps are inactive. After the active duration has elapsed, the pump is deactivated, and another pump of the multi-pump system is put into operation for the specified duration. According to a preferred embodiment, it is proposed to dynamically adjust this active duration so that at least one of the pumps uses a pump-specific active duration. Alternatively or additionally to adjusting the active duration, it is also possible to vary the frequency with which a pump is activated during a cycle.For example, it is also conceivable that the active duration for all pumps is kept identical, but the frequency of activation is varied, for example in such a way that at least one pump is not activated during a cycle or at least one other pump is activated more frequently during a cycle than the remaining pumps of the multi-pump system.

[0013] It is possible to vary the operating duration or frequency of activation of only one pump depending on the pump's operating state. It is also conceivable to dynamically adjust the operating duration or frequency of activation for multiple pumps, preferably for all pumps in the multi-pump system.

[0014] The activation duration and / or the frequency of activation cycles can be adjusted before each cycle. It is also conceivable to repeat the adjustment after predefined time intervals or, for example, after a defined number of completed cycles.

[0015] According to the invention, an initial active duration is predefined for all pumps. This initial active duration is initially identical for all pumps. Based on this predefined, identical active duration, dynamic, pump-specific adjustments are then made to obtain a pump-specific actual active duration. The adjustment of the initial active duration depends on the varying pump state of each pump. A weighting factor is determined based on the varying pump state of at least one pump. By multiplying this weighting factor by the initial active duration, the actual active duration of the at least one pump can then be calculated.

[0016] For example, it is conceivable that the weighting factor for at least one pump could be increased if its operating hours and / or age are lower than the operating hours and / or age of at least one other pump in the multi-pump system. Instead of comparing it to another pump, the average operating hours and / or average age of all pumps could also be used for comparison. Increasing the weighting factor extends the active operating time by a certain amount, thus allowing the younger pump, or the pump with the fewest operating hours per cycle, to remain active for a longer period. Overall, this results in the pump's operating time being adjusted to the average over time.

[0017] Alternatively or additionally, the weighting factor for at least one pump can be reduced if its operating hours and / or pump age are greater than the operating hours and / or pump age of at least one other pump. Alternatively, the average operating hours or average age of all pumps can be used for comparison. This approach ultimately protects the pump with the longest operating time or the oldest pump age.

[0018] It makes sense to require a minimum difference between the number of operating hours or the age of the respective pump and the reference values, i.e., the values ​​of at least one other pump or the average values, for adjusting the weighting factor. This has the advantage that an adjustment of the operating duration or frequency is not made for all pumps, but only for those pumps whose number of operating hours or pump age show larger deviations from the other pumps.

[0019] The invention extends not only to a method for operating a multi-pump system, but also to a multi-pump system as such, in particular consisting of several centrifugal pumps. The multi-pump system can preferably be designed as a double-pump system. It is also conceivable to design it as a pressure boosting system with two or more than two pumps operated in parallel.

[0020] According to the invention, the multi-pump system comprises a control unit configured to execute the inventive method. Accordingly, the multi-pump system offers the same advantages and properties as those already described above with reference to the method. Therefore, a repetitive description is omitted.

[0021] In addition to the multi-pump system, the present invention relates to a control system for a multi-pump system. The control system comprises at least one communication interface for controlling and communicating with at least two pumps of the system. According to the invention, the control system is configured to carry out the method according to the present invention.

[0022] Further advantages and features of the invention will be shown below with reference to an exemplary embodiment and corresponding drawings. The drawings show: Figure 1: a block diagram to illustrate the method according to the invention using a multi-pump system according to the invention implemented as a double pump, Figure 2a: a diagram showing the operating state of the double pump over time, Figure 2b: a diagram showing the operating hours of the double pump over time, Figure 2c: a diagram showing the difference in operating hours of the two pumps of the double pump over time, and Figure 2d: a diagram showing the weighting factor k over time.

[0023] An embodiment of the multi-pump system according to the invention is explained below using a double pump as an example. The in Figur 1A multi-pump system in the form of a double pump 10, visualized by means of a block diagram, is shown. The individual pumps of the double pump 10 are centrifugal pumps with a common suction and discharge connection. Each pump of the double pump 10 is driven by its own motor, which can, for example, be connected to its own frequency converter. In the illustrated embodiment, all pumps are identical in construction. Likewise, the motors and frequency converters can be identical in construction; however, this is not essential for the concept of the invention.

[0024] At least during normal operation of the dual pump, both pumps operate cyclically, meaning each pump is active for a set duration (e.g., 24 hours) during a cycle, while the other pump is switched off. After the active duration has elapsed, the pump is switched off and the second pump is started. At the end of the cycle, each pump has operated for at least one full active duration.

[0025] In the illustrated embodiment, an initial operating time, e.g., 24 hours, is defined for the pumps. This initial operating time is multiplied by a factor k, which is calculated based on the operating hours of each pump. The factor k is always 1 as long as the difference in operating hours between the two pumps is less than a certain threshold h. If this threshold is exceeded, the factor k is increased to a value greater than 1 (e.g., 2), but only while the pump with the fewer operating hours is running. When the pump with the more operating hours is running, k is again 1. In this way, the operating hours of the pumps gradually converge.

[0026] The process described above is shown again in the block diagram of the Figur 1To clarify: First, the difference between the operating hours (1) of the first pump and the operating hours (2) of the second pump is calculated. This data is transmitted from the pumps to a control unit via a communication interface for the difference calculation. In the next step, the value (4) of the difference (3) is calculated, and in block 5, the threshold adjustment takes place. If the difference (4) is less than or equal to the threshold (h), the factor (k) is set to 1; if the difference (4) is greater than the threshold, the factor (k) is doubled and set to 2.

[0027] The effects of the procedure will be illustrated using the time diagrams of the Figures 2a to 2d will be shown. Figur 2aThis diagram shows the operating state of the two pumps in the dual pump system, where state=1 describes a pump operating, while state=0 characterizes the pump's inactivity. The dashed line 11 describes the state of the first pump, while the solid line 12 describes the state of the second pump. The pump-specific active duration of the first pump 1 is therefore the time during which the first pump, or line 11, remains continuously in state 1. The active duration of the second pump is defined by line 12 in state=1.

[0028] The diagram clearly shows the Figur 2a that both pumps are always operated alternately, i.e., only one of the pumps is active at any given time, while the remaining pump is switched off. In the Figur 2bThe operating hours for each pump are recorded against time, with the dashed line 13 characterizing the first pump, while the solid line 14 represents the operating hours of the second pump.

[0029] The development of the difference between the two operating hour values ​​is shown in the Figur 2c The dashed line 15 plots the value against time. Additionally, the diagram also includes the threshold value h, which remains constant over time.

[0030] According to the procedure described here, the factor k changes as shown in the representation. 2D Figure to a higher value than 1, namely 2, as soon as the difference in operating hours exceeds the threshold h and only the pump with the lower number of operating hours is active, here the first pump (lines 11 and 13 in Figures 2a, 2bDoubling the factor k results in the active operating time of the first pump (the pump with fewer operating hours) also doubling. This makes the difference in operating hours between the two pumps progressively smaller (see Figur 2c The difference is reduced until it falls below the threshold h. From this point on, the factor k remains constant at 1, causing both pumps to run for the same duration.

[0031] The method described above using a twin pump as an example can be applied to pressure boosting systems with up to six pumps. One way to balance the operating hours in this case would be to always give the pump whose number of operating hours is lower than the average operating time of all pumps by a threshold value h a longer runtime or active duration.

[0032] Alternatively, the operating time for each pump could be individually configured, for example, depending on how their number of operating hours (Ti) relates to the average number of operating hours (Tmin) of all pumps. (The index i represents one of pumps 1-6 in the booster system, which has a total of six pumps.)

[0033] This gives each pump an individual factor ki, which is multiplied by the initial active duration as soon as the pump starts running. The following rules are followed: if T i > T min , then ki > 1; if T i < T min , then ki < 1.

[0034] In this way, the operating hours of the pumps in a pressure boosting system become more balanced. Alternatively, the activation duration could remain unchanged, and instead, the frequency with which a pump runs during a cycle could be adjusted. Currently, for example, in systems with six pumps, all pumps are switched on sequentially, and only after all pumps have been active once does the cycle begin again. If, for example, one of the pumps has significantly more operating hours, this pump could only be activated every other cycle, so that in this case, too, the operating hours of all pumps adjust over time.

[0035] When using the inventive method for pressure boosting systems, it is important to ensure that all pumps adhere to their minimum operating time. For example, in drinking water applications (waterworks), it is necessary for all pumps to operate within a specific time window to prevent the formation of germs in the water. To ensure this, as an alternative to increasing the operating time of a pump with low operating hours, the operating times of pumps with high operating hours could be reduced.

[0036] The advantage of the idea according to the invention can be summarized again briefly as follows: The pumps in a multi-pump system are generally replaced completely after a certain service life of the entire system. If there is a pump in this system that is still relatively new (for example, it was only recently replaced after a defect), this relatively new pump is also disposed of. With the method presented here, this new pump would already have run significantly more and thus relieved the other older pumps. This, in turn, reduces the probability of failure of the older pumps.

Claims

1. Method for operating a multi-pump system (10) comprising two or more pumps which convey fluid into a common pressure line, wherein the pumps are operated alternately, so that precisely one of the pumps is active or only some of the pumps are simultaneously active in order to convey fluid, wherein the individual running time of each or at least some of the pumps is defined dynamically depending on a state of the respective pumps that varies during operation of the system (10), wherein an identical active duration is initially established for all the pumps in advance, wherein the actual active duration for at least one pump is dynamically calculated in a pump-specific manner on the basis of the initial active duration and depending on the varying pump state of the pump, characterized in that a weighting factor k is determined on the basis of the varying pump state of at least one pump, and the pump-specific actual active duration of the at least one pump is preferably determined by multiplying the initial active duration by the determined weighting factor k.

2. Method according to Claim 1, characterized in that the varying pump state is the number of operating hours and / or the age of the respective pump.

3. Method according to either of the preceding claims, characterized in that the pumps are operated alternately during a cycle with a definable active duration for each pump, wherein the running time is adjusted by the dynamic adjustment of the pump-specific active duration of the pump during a cycle and / or the frequency of activation of a pump.

4. Method according to any of the preceding claims, characterized in that the weighting factor k for the at least one pump is increased if the number of operating hours and / or the age of the pump is less than the number of operating hours and / or the pump age of at least one further pump of the multi-pump system (10) and / or the average number of operating hours and / or the average age of all the pumps.

5. Method according to any of the preceding claims, characterized in that the weighting factor k for the at least one pump is reduced if the number of operating hours and / or the age of the pump is greater than the number of operating hours and / or the pump age of at least one further pump of the multi-pump system (10) and / or the average number of operating hours and / or the average age of all the pumps.

6. Method according to Claim 4 or 5, characterized in that the weighting factor k of the at least one pump is increased and / or reduced only in the case that the difference or absolute value of the difference between the number of operating hours and / or the pump age of the at least one pump and the number of operating hours and / or the pump age of at least one further pump and / or the average number of operating hours and / or the average age of all the pumps exceeds a, preferably definable, threshold value h.

7. Method according to any of the preceding claims, characterized in that the dynamic adjustment of the active duration is performed for all the pumps of the multi-pump system (10) or is performed only for those pumps of which the number of operating hours and / or pump age differs by more than the definable threshold value h from the average number of operating hours of all the pumps and / or the average pump age.

8. Multi-pump system (10), in particular double-pump system, configured with a controller for carrying out the method according to any of the preceding claims.

9. Controller for a multi-pump system (10) having a communication interface for actuating and communicating with at least two pumps, characterized in that the controller is configured to perform the method according to any of Claims 1 to 7.

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