DE2746598A1 - CENTRIFUGAL PUMPS IN A SERIES - Google Patents

Description

Centrifugal pumps connected in series

The invention relates to centrifugal pumps connected in series, which are used in Systems through which the conveying medium flows, such as B. Heating systems occur. Several centrifugal pumps can be installed in series or in parallel. In the former case, this is done for reasons the regulation (addition of the delivery head), in the second case also for reasons of regulation (addition of the delivery flows) or in the event of failure a centrifugal pump to switch to a replacement pump. With a parallel arrangement of z. B. two centrifugal pumps must be complex so-called Y-pipes with non-return organs or the like can be provided, the automatic or manual reversal of the promotion from the one to allow the other pump. The pumps can then also be reversed at a certain interval in order to achieve uniform running times. The pumps can also be in operation together to increase the flow rate.

These options are available for centrifugal pumps that are connected in series are not given without further ado, because always z. B. the standing pump would have to be traversed and with the already low loss levels of such a system and thus at the low head of each working centrifugal pump a part of the head in its flowed through Housing and impeller parts would be destroyed.

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There would also be the risk of increased, undesirable noise generation due to the complicated flow paths and also the risk is lower Rotor speeds and thus bearing wear. On the other hand, with pumps connected in series, the Y-pipes can be omitted, as well the lateral installation space requirement would be less.

A unit consisting of two alternately and alternatively jointly operable, centrifugal pumps connected in series has already become known (DT-PS 18 08 411), but this is required like the one at the beginning called parallel connection of two centrifugal pumps expensive additional measures in the form of additional pipes or additional housings.

To eliminate the disadvantages of pumps connected in series and thus to take advantage of a cheap, space-saving arrangement can, is the object of the invention, the solution with pumps of the type mentioned in an automatically actuated bypass with in the direction Pressure chamber opening non-return element between the respective suction and the respective pressure chamber exists, which occurs when the impeller and thus higher pressure in the spiral housing closes the suction nozzle against the same, so that the respective pump works normally. This can be done automatically actuatable bypass z. B. a passage on a partition between the the respective suction nozzle and the respective spiral housing are used, into which the respective impeller feeds.

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1 to 6 show conventional designs and embodiments of the centrifugal pumps connected in series according to the invention, 1 schematically shows a conventional series connection with pumps 1 and T, FIG. 2 shows a parallel connection of these pumps 1 and 1 'by means of complex Y-pipes together with a non-return device 3 for reversing the delivery from one pump to the other.

3 and 3 α, however, show an embodiment of a series connection according to the invention with a bypass 8 with non-return member 9 on a partition 4 between the suction nozzle 5 and z. B. the Volute casing 6 into which the impeller 7 feeds. The non-return device 9 closes the suction nozzle 5 against the same when conveying the impeller and thus high pressure in the volute casing, so that normal pump work is guaranteed is.

When the pump 1 is stationary and the second pump T connected in series is in operation, the pressure in the suction nozzle of the stationary pump is greater than that in its spiral housing space 6, as a result of which the non-return element 9 opens. As a result, the pump that is in operation can also flow through the non-return element 9, in addition to the stationary impeller, with the advantage of very small head losses and low flow velocities through the stationary impeller and thus less noise and less tendency to follow. When the pump is started up again, the non-return element 9 closes and the process is repeated for the other pump, which is now connected in series.

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When two pumps are in operation, both non-return devices 9, in the case of both pumps standing and z. B. gravity operation of the heating system, open both non-return organs 9 and thus reduce the resistance of the upright pumps installed in the line.

An opening between the suction and pressure chamber is already, for. B. at Heating circulation pumps, for regulating the pump characteristics of the working Pump with a manually or automatically adjustable passage size has become known. By large dimensions of such a passage can the pump in question, however, only designed by hand for a correspondingly large passage of the flow rate when the pump is at a standstill will. An automatic opening of this passage is not possible in the known design, since it is either to be set permanently Size is designed or as a kind of check valve, which for the purpose according to the invention opens in the wrong direction (DT-OS 21 27 449).

It is possible to expand the scope of the invention To arrange non-return device 9 in addition to the known bypass control or to combine to form a common device (for example to an optionally adjustable control bypass) by lifting the non-return device 9 and then fully automatic opening of the non-return valve with the pump at standstill with external flow or as described above, alone the non-return device 9 to be arranged. This non-return member 9 can encompass the entire annular surface between the suction and pressure chamber or else only part of it.

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Another exemplary embodiment is shown in FIG. 4, according to which in a Heating circulation pump in canned motor design z. B. the entire pump motor rotor when the pump is stationary by an axially acting force (e.g. magnetically, mechanically, etc.) in the direction of the motor side is, whereby a sufficiently large passage gap 11 on the impeller neck 10 from the suction nozzle into the pressure chamber so that the above-mentioned flow rate finds additional passage. When back in operation the pump is overcoming the aforementioned axial force by a The axial force introduced by the motor pulls the rotor back in the direction of the pump, causing the impeller neck to move into the sealing gap on the suction side submerges and normal pump operation resumes.

This shift can also be done solely by the impeller, which is in the Standstill is shifted towards the pressure side by the compulsion of an axial force on the shaft and during operation by the axial force of the Impeller again against the force mentioned - which is smaller than the axial force - is pressed into the normal axial position.

Both in the case of the axial displacement of the entire rotor as well as the Impeller alone, a pair of permanent magnets can serve, which in turn act as a thrust bearing when the pump is operated with a repelling magnet arrangement can function (there is no need for any other costly and power-intensive axial force relief) and, moreover, if the axial force is desired Displacement of one magnet from the outside drives the impeller or the entire rotor in the direction of the pressure side in front of it and thereby additionally acts as a Bypass regulator (via the vacated suction side gap 11) is used.

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If the magnet position remained unchanged, the * pump would remain in operation Constant bypass control; when the pump is at a standstill, the impeller displacement would also provide the desired value for the series arrangement once again enlarged flow cross-section 11 at the suction-side sealing gap result. Of course, it can be storage, regulation and in general The displacement device can also be mounted, for example, via a control mandrel with hard metal that can be adjusted from the suction side, and a spring combination can be used.

An additional example (Fig. 5) shows the impeller on its hub side Cover disk 13 on the pressure side with very large passage openings 14 against which a valve disk 15 rests in normal operation of the centrifugal pump, which closes the passage openings 14 during operation of the pump due to the higher pressure in the pressure-side wheel side space and thus the normal one Characteristic curve causes. Only when the pump is at a standstill and the other, connected pump flows through it, does this valve disk open and releases the desired passage openings 14. This valve disk 15 can, in turn, with small ones attached to the normal impeller Relief holes are provided.

Another advantageous exemplary embodiment according to FIG. 6 allows the Expand bypass control and combine it with an additional passage 18 to enable a series-connected Pump arrangement.

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For this purpose, an already known response in the direction of the suction side (pressure in the spiral space greater than in the suction space), manually or automatically operated control valve disc Io (DT-OS 21 27 449), according to the inventive idea, a second valve disk 17 responding in the direction of the pressure side is attached, which when operating the pump because of the higher pressure in the spiral space opposite the suction chamber, the openings 18 in the first-mentioned control valve te Her 16 keeps closed. Only when the pump has stopped and the second series-connected pump flows through it again does it open Control valve disk 17 and releases the openings 18. This control valve disk 16 can be a circular ring or only at one point on the circumference be formed between the suction and pressure chamber, the control valve disk also as a second circular ring or only at one point on the circumference to be ordered.

All possible solutions described can vary from case to case can be sensibly combined with each other.

The inventive design of the centrifugal pumps, which can be switched one after the other, allows, regardless of the inventive concept, the use as individual pumps while retaining all the advantages of uniform manufacturing and storage, without the additional devices according to the invention then having a disruptive effect.

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Claims (5)

Klein, Schanzlin & Becker Aktiengesellschaft Claims M. ! Centrifugal pumps connected in series, marked by an automatically operated bypass (8, 11, 14, 18) with in the direction Pressure chamber opening non-return member (9, 10, 15, 17) between the respective suction and the respective pressure chamber. 2. Series-connected centrifugal pumps according to claim 1, characterized characterized in that a passage (8) on the partition (4) between the respective suction nozzle (5) and the respective spiral housing is used as a bypass (6) is used. 3. Series-connected centrifugal pumps according to claim 1, characterized by one of the motor side to be mechanical or magnetically axially displaceable motor pumps I on it (7) and one at The passage gap (11) on the impeller neck (10) is present as a bypass between the suction chamber and the pressure chamber. 909816/0605 4. Series-connected centrifugal pumps according to claim 1, characterized characterized in that the rotor (7) on a hub-side, pressure-side Cover plate (13) with large passage openings (14) and with a pressure-side operating pressure or suction-side overpressure in relation to these openings in the direction of the closing or opening. Open position actuatable valve disc (15) is provided. 5. Series-connected centrifugal pumps according to claim 1, characterized characterized that as a bypass with automatic control one in the direction Suction-side responsive control valve disk (16) with passage (18) and an additional valve disk (17) responsive towards the pressure side to serve. 909816/0505