EP1731684B1 - Method for sewage lifting and sewage lifting device therefor - Google Patents

Description

The invention relates to a method for adjustment and operation of a equipped with a centrifugal pump sewage lifting plant, which serves to promote fäkalienhaltigem or faecal-free wastewater and optionally of surface water in a channel system, wherein the preferably via a check valve, in particular a non-return valve in a pipeline to be pumped wastewater occurs below a defined backflow level for the channel system, and wherein a minimum flow rate is specified for the promotion. In addition, the invention relates to the wastewater lifting plant itself.

Wastewater lifting plants, which have to promote accumulating water below the backflow level of a sewer system, are usually arranged in residential buildings. Above all, they serve to extract sewage-containing wastewater, which accumulates in the cellars of such residential buildings. Therefore, they are often referred to as Fäkalienhebeanlagen.

For the design of such systems, the existing geodetic head and the dynamic losses due to the flow are determined first. Based on this data, a pipeline characteristic is determined. Now, the minimum and maximum flow rates are calculated from the minimum and maximum flow rates prescribed by the standard and entered in a prepared diagram. In the diagram, the characteristics of several available lifting systems are conveniently drawn. One within the permissible range, the point of intersection between the lifting system and the piping characteristic gives the sought-after indication of a suitable lifting system.

Although the effort required to design a lifting system can be minimized by a computer program; but there is still the risk of over-dimensioning of the lifting system due to excessively estimated losses. As a result, the system operates outside allowable flow rates and produces unwanted noise. In addition to the flow noise in the pipeline, if the volume flow of the pump is too high, a sniffing operation may occur when the minimum fluid level is reached, which also generates disturbing noises in the building.

The invention has for its object to provide a method that overcomes the indicated problems of interpretation and provides a particular application adapted and working without disturbing noise sewage lifting system.

This object is achieved for a system of the type mentioned according to the invention by a method which initially determined for different significant operating points rotational speeds of the centrifugal pump with the help of one equipped with a programmable frequency converter, the centrifugal pump driving electric motor in a fully installed lifting system, which together with the resulting data stored in a central unit controlling the plant and their further operation are based.

The inventive method determined by itself all relevant parameters of the concrete system and adjusts the lifting system accordingly. This self-adjustment has the advantage that the lifting system is operated in the optimum flow velocity range and thus do not cause the mentioned noise.

The hitherto necessary for the design of the plant effort is saved. The requirement of the standard for certain flow velocities is certainly met. Moreover, the plant can be used in a wider range of applications, which reduces the number of necessary variants of lifting equipment, which in turn brings savings for manufacturing and warehousing.

The control used for self-adjustment can additionally take on a variety of monitoring tasks to self-help.

An expedient embodiment of the method according to the invention provides that when a first or recommissioning of sewage lifting the centrifugal pump is ramped up to a maximum speed and turned off before reaching a still suitable for promoting minimum sewage levels, then switched on with closed check member, the centrifugal pump again and whose speed is steadily increased, the speed reached when opening the check member is stored as the zero speed corresponding height speed, whereupon the predetermined minimum flow speed corresponding speed is determined and stored.

The determination of the predetermined minimum flow speed corresponding speed can be done in different ways. On the one hand, the speed can be determined by calculation. In this case, the system characteristic curve (defined by the determined zero-point delivery head) and the pump characteristic curve are cut at a quantity point which corresponds to the minimum flow rate. On the other hand, the speed in question can also be determined by a flow meter arranged in the pipeline. Conveniently, a non-return valve designed according to the dynamic pressure principle is used as a flow meter.

In a further advantageous embodiment of the invention, it is proposed that the switching off of the centrifugal pump via a preset speed ramp takes place. This has the beneficial effect that the non-return member closes slowly, a hard loud closing noise is thus avoided.

As already mentioned, a lifting system operating with the method according to the invention is also capable of undertaking monitoring tasks during operation. Thus, the method recognizes due to a suitably designed evaluation scheme, a blockage of the check member or a flow disturbance in the pipeline, and it can derive a remedial action. Thus, when a detected disturbance of the flow, the speed of the centrifugal pump can be increased, so to speak, a purge flow caused. Only after exceeding a predetermined period of time, a shutdown signal and / or a warning signal is then given to persist the fault.

Finally, it is proposed that when the delivery rate changes to a predetermined peak load range, a speed increase takes place, in each case the permissible flow rate being maintained. This makes it possible, with appropriate dimensioning of the centrifugal pump, to save a hitherto necessary peak load pump.

A sewage lifting plant using a method according to the invention with a centrifugal pump for conveying sewage-containing or faecal-free wastewater and / or surface water into a sewer system has an electric motor equipped with a programmable frequency converter for driving the centrifugal pump. To facilitate the adjustment of the lifting system, the non-return valve connected downstream of the centrifugal pump may be equipped with a sensor which signals the opening of the non-return valve. It is also advantageous when using the method according to the invention if the non-return valve can be used as a flow meter according to the dynamic pressure principle. This facilitates the adjustment, since this can be used to determine the achievement of the prescribed minimum flow rate. In addition, a constant control of the operation of the lifting system is possible with the flow meter.

The EP 1 138 950 A1 discloses a pressure booster to which consumers are connected. A liquid pump is driven by an electric motor and a controller is used to compare an actual value of an output pressure of the liquid pump with a predetermined setpoint of Output pressure. As is usual with booster systems, the controllability of the pump power by varying the pump drive speed is used to cover fluctuating consumption values at constant pressure or sliding pressures according to predetermined criteria. By caused by a control circuit unusual operation of the controller this is placed in a kind of oscillating state in which consumption levels near zero, the actual value exceeds the setpoint of the pressure, resulting in a Abregeln the engine and thus to a pump shutdown. The initially described problems of a sewage lifting plant, is promoted in the sewage or surface water in a sewer system, are by the EP 1 138 950 A1 unsolved.

DE 35 20 538 A discloses a plant for the delivery of milk, wherein a centrifugal pump is designed with frequency converter. The control of the plant deals with the problem of cavitation.

Fig. 1

eine Fäkilienhebeanlage, bei der das erfindungsgemäße Verfahren anzuwenden ist;

Fig. 2

ein Diagramm, wie es für die Auslegung von Hebeanlagen der vorbekannten Art benutzt wurde;

Fig. 3

eine mit dem erfindungsgemäßen Verfahren justierte und arbeitende Fäkalienhebeanlage.

Reference to an embodiment of the invention will be explained in more detail. The drawing shows in

Fig. 1

a Fäkilienhebeanlage, in which the method according to the invention is to be applied;

Fig. 2

a diagram as used for the design of lifting systems of the known type;

Fig. 3

a Fäkalienhebeanlage adjusted and working with the method according to the invention.

The in the Fig. 1 shown system is arranged for the most part below the backflow level 1, which is characterized here by a triangle. The plant comprises a collecting container 2, which is connected to a sewer line 3, and a delivery line 4, which opens into a sewer 5. In the collecting container 2 a - not shown - centrifugal pump is arranged, which promotes from the sewer 3 flowing fäkalalienhaltiges and fäkalienfreies wastewater via a check valve 6 in the sewer 5.

The interpretation of such a plant was done so far in a reference to the diagram of Fig. 2 in an illustrative way. In a first step the respective given geodetic head and the dynamic losses were determined by the flow or determined on the basis of empirical values. From this a pipeline characteristic was calculated. - The diagram shows a piping characteristic marked with the number 7. - Then the minimum flow rate Q _min and the maximum flow rate Q _{max were} calculated from the minimum and maximum flow velocities prescribed by the valid standard and transferred to the diagram. Now, based on the characteristics of the available lifting systems, in the exemplary embodiment, these are HA 1 to HA 3, a suitable system can be selected. For this purpose, the point of intersection of the lifting system characteristic curve had to lie within the permissible range between Q _min and Q _max , this is true in the diagram of FIG Fig. 2 to the plant H 2 too.

The disadvantage of a designed in the manner described plant was not only the design effort to be driven. More important still was the risk that the system was wrongly dimensioned due to wrong assumptions about the losses to be considered. To be on the "safe side" here, i. To design a plant that works anyway was estimated to be too high rather than too low. But this had the consequence that the permissible flow velocities were exceeded and thereby caused disturbing noises through the system. In addition, when the minimum fluid level was reached, the large volume flows of the pumps led to a snor- ing operation, which also produced disturbing noises in the building.

The method according to the invention not only eliminates problems with the design. This procedure also allows plant operation with continuous self-checking and automatic correction of minor disturbances, which, if not remedied, could lead to major disruptions or even equipment failure. This is based on in the Fig. 3 outlined sewage lifting unit explains:

The lifting system is equipped with a centrifugal pump 8 whose electric motor 9 is provided with a programmable frequency converter 10. The centrifugal pump 8 can therefore be operated at different speeds. The centrifugal pump 8 is followed by a check valve 11, which is equipped with an opening of the check valve 11 reporting sensor. The Lifting system has a collecting container 12, in which a level sensor 13 is provided, which responds to three different preset fluid levels: at a minimum fluid level, it gives the signal "Abpumpbetrieb OFF", at a normal high water level, it gives the signal "Abpumpbetrieb ON", and at a he reports "flood ALARM" the water level exceeding the latter level.

When a first or recommissioning receives at a correspondingly high level of fluid in the reservoir 12, the control of the frequency converter 10 from the level sensor 13, the command "Abpumpbetrieb ON". The centrifugal pump 8 is now moved by the frequency converter 10 on a ramp, i. with a continuous increase in speed, started up. The maximum speed is reached when the maximum geodetic height including the dynamic losses for the lifting station is safely overcome. After a time dependent on the volume of the collecting container 12 period and before the minimum liquid level is reached, the centrifugal pump is switched off. Now, the check valve 11 closes and the liquid column of the pipeline located above is static pressure on the check valve eleventh

In the next step, the centrifugal pump 8 is raised again on a speed ramp, wherein the speed is stored at which the sensor of the check valve 11 "Open" reports. The speed stored here is directly related to the zero-point head, which in turn corresponds to the geodetic head.

In the further course of the speed is steadily increased until the prescribed minimum flow rate is reached safely. The speed increase necessary for this can be calculated from the now known system characteristic curve or by a flow meter, as the u.a. the check valve 11 could function with the appropriate equipment according to the dynamic pressure principle can be specified.

With the process described so far, the lifting system is adjusted for further operation. However, the method according to the invention is also suitable to optimize this further operation and to protect against various disturbances:

For example, the method can be used to effect a gentle closing of the non-return valve 11 by shutting down the centrifugal pump 8 via a speed ramp. Incidentally, the system operating with the method or the control equipped accordingly is capable of detecting a blockage of the non-return valve 11 or an incipient clogging within the hydraulic part and reacting appropriately thereto. If a short-term speed increase with the flushing effect achieved thereby is not sufficient to eliminate the fault, the system can trigger a warning and / or a switch-off signal.

In systems that were equipped with conventional design with an additional peak load pump, if necessary, can be dispensed with when using the method according to the invention on a second pump. This requires only a larger-sized pump that runs in normal operation with reduced speed, but at peak load by increasing the speed of the requirements. It is of course to ensure compliance with the permissible flow rate.

Claims (12)

1. Method for adjusting and for operating a sewage lifting plant which is equipped with a centrifugal pump and which serves for the conveyance of faeces-containing or faeces-free sewage and, if appropriate, of surface water into a conduit system, the sewage to be conveyed via a check member (6, 11), in particular a swing check valve, in a pipeline (4) occurring preferably below a backpressure plane (1) defined for the conduit system (5) and a minimum flow velocity being stipulated for conveyance, characterized in that, in a ready-installed lifting plant, first the rotational speeds of the centrifugal pump (8) which are significant for various prominent operating points - maximum geodetic height, including the dynamic losses, geodetic delivery head and attainment of the prescribed minimum flow velocity - are determined with the aid of an electric motor (9) equipped with a programmable frequency converter (10) and driving the centrifugal pump (8) and, together with the data resulting from this, are stored in a central unit controlling the plant and are taken as a basis for the further operation of the plant, and the characteristic curve of the sewage lifting plant is prepared, using the data determined, and the rotational speed corresponding to the stipulated minimum flow velocity is determined on the basis of this characteristic curve.
2. Method according to Claim 1, characterized in that, in the first commissioning or recommissioning of the sewage lifting plant, the centrifugal pump (8) is run up continuously to a maximum rotational speed and is switched off before a minimum sewage level still suitable for conveyance is reached, and then, with the check member (11) closed, the centrifugal pump (8) is switched on again and its rotational speed is run up continuously, the rotational speed reached when the check member (11) is opened being stored as the rotational speed corresponding to the zero-point delivery head, whereupon the rotational speed corresponding to the stipulated minimum flow velocity is determined and stored.
3. Method according to Claim 1 or 2, characterized in that the rotational speed corresponding to the stipulated minimum flow velocity is determined by means of a flowmeter arranged in the pipeline.
4. Method according to Claim 3, characterized in that a swing check valve (11) operating according to the dynamic pressure principle is used as a flowmeter.
5. Method according to one of the preceding claims, characterized in that the centrifugal pump (8) is switched off via a preset rotational-speed ramp.
6. Method according to one of the preceding claims, characterized by an evaluation diagram detecting a blockage of the check member (11) and having an action derived from this.
7. Method according to one of the preceding claims, characterized by an evaluation diagram detecting a fault in the throughflow in the pipeline (4) and having an action derived from this.
8. Method according to Claim 6 or 7, characterized in that, when a fault in the throughflow is found, the rotational speed of the centrifugal pump (8) is increased, a shutdown signal and/or a warning signal being given after a stipulated time span is exceeded and if the fault continues to be present.
9. Method according to one of the preceding claims, characterized in that, in the case of a transition of the delivery rate into a stipulated peak-load range, an increase in rotational speed takes place, in each case the permissible flow velocity being maintained.
10. Sewage lifting plant for carrying out the method according to one of Claims 1 to 9, the sewage lifting plant comprising a collecting tank (2) connected to a sewage line (3) and a conveying line (4) issuing into a sewage conduit (5), the sewage lifting plant being equipped with a central unit controlling the sewage lifting plant and with a centrifugal pump (8), the electric motor (9) of which is provided with a programmable frequency converter (10), and the centrifugal pump (8) being followed by a swing check valve (11) provided in the conveying line (4), characterized in that the centrifugal pump (8) is arranged in the collecting tank (2) and is operated by the method according to one of Claims 1 to 9.
11. Sewage lifting plant according to Claim 10, characterized in that the swing check valve (6) is equipped with a sensor signalling the opening of the latter.
12. Sewage lifting plant according to Claim 10 or 11, characterized in that the swing check valve (6) is designed according to the dynamic pressure principle as a flowmeter.

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