EP2505843A1 - Centrifugal pump assembly - Google Patents

Abstract

The centrifugal pump arrangement comprises a centrifugal pump unit (60) and a suction device (70) for generating additional low pressure in a suction pipe (64) connected with the suction side of the centrifugal pump unit. The suction device is arranged in the suction pipe adjoining a suction connection (10) of the centrifugal pump unit and is connected with the suction pipe. The centrifugal pump unit is formed in a regenerative manner.

Description

The invention relates to a centrifugal pump arrangement with at least one centrifugal pump unit.

Centrifugal pumps, in particular multi-stage centrifugal pumps are used to convey liquids. The problem is that such centrifugal pump units are usually not self-priming. In special embodiments, in particular the first stages of multi-stage centrifugal pump units, it is possible to give the centrifugal pump units self-priming properties. However, in certain applications, such as in ships' fire-fighting equipment, it is necessary to ensure automatic suction at higher altitudes in a very short time to achieve full pumping performance within a short time.

In view of this problem, it is an object of the invention to provide a centrifugal pump assembly, which allows a quick startup and a quick startup of the pump unit when aspirating liquid.

This object is achieved by a centrifugal pump assembly having the features specified in claim 1. Preferred embodiments will become apparent from the subclaims, the following description and the accompanying figures.

The centrifugal pump arrangement according to the invention has at least one centrifugal pump unit. To support the suction process In addition, in the centrifugal pump arrangement, a suction device for generating a negative pressure on the suction side of the centrifugal pump assembly or in a suction line connected to the suction side is provided. This suction device generates a negative pressure in the suction line, which causes suction of liquid in the suction line to the centrifugal pump assembly. Thus, even a centrifugal pump unit, which has no self-priming properties, are put into operation. A self-priming centrifugal pump unit can be supported by such an additional suction in the suction, so that the suction and commissioning of the Kreiselpumpenaggrates is accelerated. The suction device is either arranged in the suction line itself or is connected to this suction line.

In this case, the suction device is preferably arranged adjacent to a suction connection of the centrifugal pump assembly in the suction line or connected adjacent to the suction connection with the suction line. By this arrangement it is achieved that the additional negative pressure in the suction line is generated near the suction nozzle of the centrifugal pump unit, so that from the suction means, the liquid can be sucked up to the suction port of the centrifugal pump assembly. Alternatively, it would also be possible to integrate the additional suction device in the centrifugal pump unit or to connect directly in the centrifugal pump unit in the region of the intake with the flow path. In this way, the liquid can be conveyed as close as possible to the first impeller by a negative pressure generated by the suction device.

Particularly preferably, the centrifugal pump assembly is self-priming. Thus, the additional suction only serves to support the self-priming properties of the centrifugal pump unit, so when commissioning the centrifugal pump unit a very fast suction is achieved, so that the full capacity of the pump unit can be achieved quickly.

According to a first preferred embodiment of the invention, the suction device has a support tank designed for receiving liquid, which has on its upper side a suction connection which is connected to the suction line and has a discharge opening on its underside. By opening the drain opening liquid will flow from this support tank due to gravity, so that at the top of the support tank, a negative pressure is generated, which is passed through the suction port to the suction and thus generates in this the above-described supporting negative pressure, sucked by which liquid in the suction line can be.

In order to be able to open the discharge opening in a targeted manner, the discharge opening is preferably provided with a valve for opening and closing the discharge opening. To fill the support tank, the drain opening is closed and only opened when the negative pressure is to be generated by draining the liquid in the support tank.

The discharge opening preferably opens in a second vertically lower liquid tank. This can in turn be connected to the suction line, so that the liquid which drains from the support tank is then sucked in and conveyed by the pump unit. Ie. Preferably, the support tank is filled with the same liquid which is to be conveyed by the pump unit, for example water.

For filling the support tank this is further preferably connected via a filling line with a pressure side of the centrifugal pump assembly. Thus, the support tank during operation of the centrifugal pump unit be filled with the funded by the centrifugal pump unit liquid. Thus, the support tank is filled in normal operation of the centrifugal pump assembly and then after taking out the centrifugal pump unit filled ready for recommissioning of the centrifugal pump unit, so that he can then generate the required negative pressure in the suction line when starting the centrifugal pump unit by draining the liquid.

The filling line may preferably open into the discharge opening of the support tank, d. H. the support tank is then filled via the filling line from below.

For this purpose, a three-way valve, which is designed such that it connects the discharge opening optionally to the filling line or a discharge line, can be arranged on the discharge opening. The drain line then leads, for example, to the second vertically lower liquid tank or to another area in which the liquid is to be drained from the support tank. Thus, the filling of the support tank and the discharge can be controlled via a valve. For filling, the three-way valve is brought into a first position in which the drain line is closed and can flow through the filling line liquid into the interior of the support tank. To open the drain opening for draining the liquid, the three-way valve is brought into a second switching position in which the filling line is closed and the drain line is released, so that the liquid can flow out of the support tank. In order to prevent backflow of the liquid from the support tank into the filling line when decommissioning of the pump unit, a backflow preventer can be arranged in this. Alternatively, it is possible to position the support tank in its vertical height so that its upper side is located below the connection of the filling line with the centrifugal pump unit. So, even if the fill line is connected to the underside of the support tank, do not pour the liquid back into the centrifugal pump unit via the filling line.

More preferably, a check valve or a backflow preventer is arranged in the connection of the suction connection with the suction line. This check valve prevents that during operation of the centrifugal pump unit this liquid sucks on the suction line from the support tank.

According to a second preferred embodiment of the invention, the suction device has an aspirator or a venturi nozzle, wherein the venturi nozzle is connected to the suction line via a vacuum line opening at a constriction in the nozzle. In the Venturi nozzle preferably a compressed gas, in particular compressed air is passed. This compressed gas or compressed air flow is accelerated in the constriction of the nozzle in a known manner, so that a negative pressure is generated in the environment, which is transmitted through the opening into the constriction of the nozzle vacuum line to the suction line and so in this one negative pressure for suction generated by liquid. The vacuum line opens into the suction line, preferably in the vicinity or directly adjacent to the suction opening or the suction nozzle of the centrifugal pump unit. Alternatively, this vacuum line can also open directly into the suction nozzle in the centrifugal pump assembly.

More preferably, a check valve is arranged between the suction side of the centrifugal pump assembly and the additional suction in the suction line. By this check valve prevents liquid is sucked from the centrifugal pump assembly by the suction pressure generated by the suction during startup of the centrifugal pump assembly. The check valve stops thus ensuring that liquid is sucked in only via the suction line and does not flow out of the centrifugal pump assembly counter to the usual direction of flow. This would make it difficult or prevent the commissioning of the centrifugal pump unit.

The centrifugal pump assembly may be formed in several stages and have at least two wheels, which are preferably arranged on a common shaft and are driven by them by a motor, in particular an electric motor.

The multi-stage centrifugal pump assembly is preferably constructed so that it has two successive impeller groups in the flow direction, ie groups of pump stages, in each of which at least one impeller is present. The first impeller group in the flow direction is designed so that it allows a self-priming behavior of the centrifugal pump. For this purpose, a return flow channel is present in the first impeller group, which connects the output side of the first impeller group with its input side. This return flow channel makes it possible for a fluid flow through the return flow channel and through the impeller to be effected within the first impeller group by means of the at least one impeller. Ie. in the first impeller group a limited amount of liquid can be circulated. This circulating amount of liquid causes in the first impeller group sufficient suction to suck in more liquid. This allows the entire centrifugal pump unit to automatically draw in liquid. It is only preferred that in the first impeller group, in particular in the return flow channel, a limited amount of liquid is always present to ensure that the circulating flow through the impeller of the first impeller group and the return flow channel can be used when the pump is in operation.

The return flow channel preferably opens into the suction mouth of a first stage of the first impeller group. It is thereby achieved that the liquid flowing through the return channel is returned to the inlet side of the impeller of the first stage, so that a circulating flow is achieved here.

More preferably, at least one valve for closing the return flow channel is present in the return flow channel. Through this valve, the return flow channel can be closed when the pump has reached its normal operating state. Under normal operating conditions, when the pump set is delivering fluid, an open return flow channel and a steady fluid return would degrade the efficiency of the centrifugal pump assembly. By closing the valve, this can be prevented after the pump has started up, so that the pump then works like a conventional multistage centrifugal pump.

Preferably, the valve is designed such that it closes the return flow channel upon reaching a predetermined fluid pressure in the return flow channel or on the output side of the first impeller group. The achievement of the predetermined fluid pressure is detected as a normal operating state or an operating state in which there is already a sufficient flow rate when aspirating additional liquid. The fluid pressure in the return flow channel, ie, on the output side of the first impeller group, is preferably detected by the valve. The valve is preferably designed as a spring element, wherein it is kept open by spring action against the prevailing in the return flow fluid pressure. When the fluid pressure exceeds the spring force, the valve is closed. Thus, an opening may be provided in the return flow, in front of the flow direction in which a spring plate is located, which is curved so that the sheet is spaced in its rest position from the opening. Due to increased fluid pressure, the sheet can against his Federvors be deformed so that it is pressed against the opening and closes it.

More preferably, the first impeller group is formed at least two stages with two successively arranged in the flow direction impellers. In this case, the return flow channel is arranged so that it leads from the output side of the second impeller to the input side of the first impeller. By the two-stage first impeller group sufficient flow and sufficient suction can be achieved by conveying the liquid in the circuit through the return flow channel to produce a total vacuum in the suction or suction of the centrifugal pump assembly sufficient negative pressure for the suction of liquid.

On the output side of the first impeller group, a separating element is preferably arranged, which is designed to separate air and liquid. Especially when starting the pump unit when initially only a small amount of liquid is conveyed through the return flow channel, the centrifugal pump unit will also suck in air through its suction line, with air and liquid ideally mixing on entering the first impeller. Therefore, it is expedient to separate the air from the liquid on the output side of the first impeller group in order to return preferably exclusively liquid through the return channel to the input side of the first impeller group. This prevents dry running of the return flow channel.

Therefore, the separation element is more preferably arranged relative to the return flow channel so that the liquid emerging from the separation element enters the return flow channel. This ensures that the liquid flowing in from the return flow channel into the first impeller group, when it exits the first impeller group again, substantially completely back into the return channel, so as to create a cycle.

On the input side of the first impeller group, a check valve or a non-return valve is preferably arranged, which prevents liquid from the centrifugal pump assembly can run back into a suction line. This prevents that the centrifugal pump unit can run completely dry, it is held by the check valve even when decommissioning of the centrifugal pump assembly liquid in the interior of the centrifugal pump unit, which allows the Rückanlaufen and re-aspiration. The check valve may be integrated directly into the centrifugal pump unit, but may also be recognized as a separate component to the suction nozzle of the centrifugal pump assembly.

According to a further preferred embodiment, at least one liquid reservoir is arranged between the first and the second impeller group. The liquid storage is designed so that it fills with liquid during normal operation of the centrifugal pump assembly. When decommissioning the centrifugal pump unit or in the event that the centrifugal pump unit should promote bubbles, can be ensured by the liquid in the liquid storage that the conveying effect of the centrifugal pump assembly is not completely suspended, but that there is always enough liquid in the centrifugal pump unit to re-aspirate To allow liquid through the suction nozzle or the suction line of the centrifugal pump unit.

The liquid reservoir preferably has at least one outlet opening, which is arranged such that it faces an inlet opening of the reflux channel in such a way that liquid can flow out of the liquid store into the reflux channel. This is how it is achieved first the return flow channel is filled through the liquid storage or this is kept filled. The liquid from the reflux channel then flows to the input side of the first impeller of the first impeller group and enters this, so that this impeller can immediately achieve a conveying effect and can suck in more liquid through the suction line. As liquid enters the first impeller from the suction line, as described above, the liquid in the return flow channel is first circulated in the first impeller group.

The centrifugal pump assembly is preferably formed so that the axis of rotation of the wheels extends vertically. The liquid storage device described above is then preferably designed so that its outlet opening is arranged on the underside, so that the liquid can escape from the liquid storage due to gravity down and enter the return flow channel. The liquid reservoir is preferably filled from above via the liquid flowing to the pump stages arranged behind the liquid reservoir or above the liquid reservoir. The return flow channel preferably has an upwardly directed opening, so that the liquid can enter from the liquid reservoir from above into this opening.

According to a further preferred embodiment, at least two liquid stores can be arranged such that an outlet opening of the second liquid store opens into an opening of a first liquid store. Thus, two or more liquid reservoirs can be arranged one behind the other in the flow or conveying direction between the first impeller group and the second impeller group. In this case, the liquid flows from the first or lower liquid storage, as described above, preferably in the return channel. The liquid from the second or subsequent liquid storage first flows into the first liquid storage and from this then in the return channel. Accordingly, liquid from a third Transfer liquid storage in the second liquid storage. All liquid reservoirs preferably have an outlet opening at the bottom and an inlet opening at the top.

Particularly preferably, the at least one liquid reservoir is designed as an annular pot with an open top, which surrounds a shaft driving the wheels. Ie. the pot is annular or torus-shaped and has an opening in the middle, through which the shaft extends. The opening also serves as a flow path for the conveyed liquid from the first impeller group to the second impeller group. For this purpose, a space around the shaft is provided in the opening. The cup-shaped liquid storage is open at its top, so that the liquid flowing through the central opening can run over the edge of the opening from above into the pot-shaped liquid storage. The described at least one outlet opening is preferably formed on the underside. In the arrangement of a plurality of liquid storage, the outlet openings of the subsequent liquid storage are arranged so that they are located above the top of the respective preceding liquid storage, so that the liquid from the outlet opening runs in the preceding liquid storage. From the first, d. H. lowermost liquid storage, the liquid from the outlet opening, as described, runs in the return line. The outlet openings are sized in size so that the liquid reservoirs empty slowly.

According to a particularly preferred embodiment, the individual impellers of the second impeller group are each arranged in a step module, wherein all stage modules have the same axial height, and the at least one impeller of the first impeller group is also arranged in such a step module having an axial height, the axial height or an integral multiple of the height of a step module of the second impeller group corresponds. This modular design with a fixed grid of the axial heights or lengths of the individual modules has the advantage that from the modules very simple centrifugal pump units of different performance, in particular different conveying and suction heights can be realized. Also, the first self-priming impeller group can be easily integrated into conventional multi-stage centrifugal pumps, since the parts of the first impeller group in their axial length have the same grid as the modules of the second impeller group. For example, the same tightening straps can be used to hold the modules together as used in conventional multi-stage centrifugal pumping units. Thus, the required part variety can be reduced.

Also preferably, the arranged between the two impeller groups liquid storage or spacer elements each have an axial height, which corresponds to the axial height or an integral multiple of this height of a step module of the second impeller group. Thus, it is also achieved with respect to these components that the axial height in the existing grid of the axial height of the individual pump stages, which are arranged in the second impeller group fits.

Fig. 1

eine Schnittansicht eines selbstansaugenden Kreiselpumpenaggregates,

Fig. 2

eine Detailansicht der ersten Laufradgruppe des Kreiselpumpenaggregates gemäß Fig. 1,

Fig. 3

in einer teilweise geschnittenen Detailansicht ein Ventil im Rücklaufkanal,

Fig. 4

in einer Schnittansicht die Flüssigkeitsspeicher des Kreiselpumpenaggregates gemäß Fig. 1,

Fig. 5

eine Ansicht einer Kreiselpumpenanordnung gemäß einer ersten Ausführungsform der Erfindung und

Fig. 6

eine Kreiselpumpenanordnung gemäß einer zweiten Ausführungsform der Erfindung.

The invention will now be described by way of example with reference to the accompanying drawings. In these shows:

Fig. 1

a sectional view of a self-priming centrifugal pump unit,

Fig. 2

a detailed view of the first impeller group of the centrifugal pump assembly according to Fig. 1 .

Fig. 3

in a partially sectioned detail view of a valve in the return channel,

Fig. 4

in a sectional view of the liquid storage of the centrifugal pump assembly according to Fig. 1 .

Fig. 5

a view of a centrifugal pump assembly according to a first embodiment of the invention and

Fig. 6

a centrifugal pump assembly according to a second embodiment of the invention.

The centrifugal pump unit described by way of example has a total of eight stages, d. H. eight wheels on. Of these, two wheels 2 are arranged in a first impeller group 4 and six impellers 6 in a second impeller group 8. The first impeller group 4 faces the inlet or suction nozzle 10 of the pump unit. The second impeller group 8 is connected downstream of the first impeller group in the flow or conveying direction. As in known multistage centrifugal pump units, the liquid to be conveyed flows through the individual impellers one after the other and is fed to the discharge port 14 on the output side of the last impeller 6 via the annular pressure channel 12. All wheels 2 and 6 are driven by a common shaft 16. The shaft 16 is connected at its shaft end 18 with a motor, not shown here, for example, an electric motor for driving.

The first impeller group 4 is designed to be self-priming in the manner described below, so that the centrifugal pump via the suction nozzle 10 can suck liquid even if the suction nozzle 10 and an upstream subsequent suction line are not filled with liquid.

The self-priming effect of the first impeller group 4 is determined by the basis of Fig. 2 achieved embodiment explained in more detail. On the output side of the second impeller 2 in the flow direction of the first impeller group 4, a separating element 20 is arranged. This is designed so that liquid and air are separated from each other. This happens because the liquid is accelerated radially outward, so that the air exits from the separating element 20 in the central region near the shaft 16 and the liquid in the peripheral region near the peripheral wall 22. The liquid emerging from the separating element 20 flows over the circumferential wall 22 at its upper edge and enters a return flow channel 24. The return flow channel 24 leads on the outer circumference of the first impeller group 4 back in the direction of the suction nozzle 10. Via openings 26 in a bottom plate, the return flow channel leads to the suction mouth 28 of the first impeller 2 in the flow direction of the first impeller group 4. Thus, a closed liquid circuit on the two wheels. 2 of the separating element 20 is realized back through the return flow channel 24 to the suction mouth 28 of the first impeller 2.

To start the pump, a small amount of liquid is sufficient to take the circuit described by the two wheels 2 and the return flow channel 24 in operation. As a result, the wheels 2 generate a negative pressure, through which 10 further liquid can then be sucked through the suction nozzle. When commissioning the pump unit for the first time, it is necessary to bleed the pump unit like conventional centrifugal pump units. H. to fill with a certain amount of liquid.

In order to be able to maintain the described circuit via the return line 24, it is important that the pump is formed as airtight as possible in the region of the first impeller group 4. For this purpose, various seals are arranged. The seals 30 seal the Return passage 24 against the pressure channel 12 from, so that prevents fluid from the pressure side via the return passage 24 in normal operation can flow to the suction side. In the interior of the separating element 20, a bearing 32 is arranged, which is in contact with the outer circumference of the shaft 16. This also serves to seal the separator 20 with respect to the shaft 16 to prevent air from the separator 20 from flowing back to the impellers 2. The seal 34 seals the axial end of the shaft 16 to prevent air from flowing from the pressure side of the pump via the shaft to the suction side. The seal 36 also serves to separate the pressure side of the suction side, that is, to seal the discharge nozzle 14 against the suction nozzle 10.

In order to prevent liquid from flowing back into the suction side via the return flow channel 24 after reaching the normal operating state, in which liquid is sucked in through the suction nozzle 10, a valve 38 is arranged in the return flow channel 24. This valve 38 is designed so that when it reaches a predetermined pressure on the output side of the second impeller 2, d. H. On the output side of the separating element 20 and in the return flow channel 24 closes the return flow channel. Ie. after reaching this predetermined pressure, the reflux channel 24 is closed and the liquid flows exclusively to the following wheels 6 of the second impeller group eighth

The design of the valve 38 is described in more detail with reference to Fig. 3 explained. Fig. 3 shows a detailed view of the separating element 20. The separating element 20 defines between the outer periphery of the peripheral wall 22 and a radially outer annular wall 40, a first portion of the return flow channel 24, which forms an inlet region of the return flow channel 24. The second portion of the return flow channel 24 is defined between the outer periphery of the wall 40 and a radially spaced sleeve 42 (see FIG Fig. 2 ) Are defined. In the wall 40 are a plurality of holes 44 are formed, which allow the passage from the inlet region of the return flow channel 24 in the second portion of the return flow channel 24 between the wall 40 and the sleeve 42. At the openings 44 valve elements in the form of spring plates 46 are arranged. These spring plates 46 can take two positions, namely once an open position, which in Fig. 3 designated by the reference numeral 46 '. In this position, the spring plate 46 'extends chord-shaped to the inner circumference of the wall 40 and is thus spaced from the opening 44, so that it is released. Now increases the pressure in the region of the return flow channel 24 which is located between the peripheral wall 22 and the wall 40, the spring plate 46 'is pressed radially outward and abuts against the inside of the wall 40 via the opening 44, so that the Opening 44 is closed.

In order to ensure the safe operation of the centrifugal pump assembly even if larger air bubbles pass through the system, 8 three liquid storage 48 are arranged between the first impeller group 4 and the second impeller group. These are in detail in Fig. 4 shown. The liquid reservoirs 48 are formed as annular or toroidal pots which surround the shaft 16. The shaft 16 extends through a central opening 50 of the liquid reservoir 48, wherein the wall of the opening 50 is radially spaced from the outer periphery of the shaft 16. Thus, the opening 50 also serves as a flow path for the conveyed liquid from the first impeller group 4 to the second impeller group 8. The peripheral walls 52 of the openings 50 have in the direction of the longitudinal axis X a length which is shorter than the axial length of the outer walls of the liquid storage 48. Thus, the liquid reservoirs 48 are opened at their upper side, so that liquid which flows through the openings 50 can flow over the peripheral walls 52 into the interior of the liquid reservoirs 48. Thus, the liquid storage 48 in the normal operation of the Pump unit, when liquid flows from the first impeller group 4 to the second impeller group 8, filled.

Each liquid reservoir 48 has on its underside an outlet opening 54 with a small diameter. The outlet openings 54 are radially spaced from the longitudinal axis X so far that they lie above the free space between the peripheral wall 22 and the wall 40 of the separating element 20. So the liquid runs out of the first, d. H. From the two other liquid reservoirs 48, the liquid first passes through the associated outlet opening 54 into the liquid reservoir 48 located below. The fact that the liquid from the liquid reservoirs 48 runs slowly through the small outlet opening 54 can also be then, if larger air bubbles or gas bubbles flow through the pump unit, ensure that in the pump unit still a sufficient amount of liquid is present to at least the starting circuit through the first impeller group 4, d. H. through the return channel 24 in the manner described above again to put into operation.

In addition to these measures, a check valve or non-return valve 55 is still arranged on or in the suction nozzle 10. Here, the check valve 55 is arranged directly in the suction nozzle, but it could also be recognized as a separate component to the suction nozzle 10. About such a can be prevented that when the suction pipe 10 adjoining the suction line runs dry, the liquid from the pump unit through the suction nozzle 10 runs back into the suction line. Thus, a certain amount of liquid can always be kept in the pump unit, via which at least the starting circuit in the first impeller group 4 can be put back into operation, then more liquid through the suction port 10 to suck. In this way, the entire centrifugal pump unit is self-priming.

As in Fig. 1 can be seen, the pump unit is a total modular design, this modular design is based on an axial length grid, which is defined by the axial length of the pump stages formed by the wheels 6. These pump stages each have a circumferential jacket 56, which forms the jacket of the individual stage modules. These stage modules are placed axially one on top of the other. The liquid reservoirs 48 have the same axial length as the sheaths 56 of the stage modules of the second impeller group 8. In addition, a jacket 58, which surrounds the first impeller 2, has the same axial length. The separating element 20 has an axial length in the direction of the longitudinal axis X, which corresponds to twice the axial length of the sheaths 56 and 58. Thus, the entire first impeller group 4 has an axial length which corresponds to three times the length of a step module of the second impeller group 8. This uniform length grid favors the modular design, since clamping bands, which hold the individual stage modules in the axial direction, only in different lengths, which are defined by this underlying grid, must be kept. Thus, a variety of pumps can be assembled with different numbers of wheels, fluid reservoirs 48 and, if necessary, the first impeller group 4 to ensure the self-priming properties.

The centrifugal pump assembly according to the first embodiment of the invention, which in Fig. 5 is shown, has a centrifugal pump unit 60, which in the reference to the FIGS. 1 to 4 can be configured described manner. Ie. it may in particular be a self-priming centrifugal pump unit. The centrifugal pump unit 60 has a pressure line 62 and at its pressure connection his suction nozzle 10, a suction line 64. Adjacent to the suction nozzle 10, a check valve 66 is arranged in the suction line 64, which prevents liquid can flow back from the centrifugal pump assembly 60 in the suction line 64. Instead of the check valve 66 could also be arranged in the suction nozzle 10 check valve 55, as shown in FIG Fig. 1 and Fig. 2 is shown, find use.

From the suction line 64 branches off near the check valve 66 and adjacent to the check valve 66 on the suction nozzle 10 side facing away from a vacuum line 68, which opens at the top in a support tank 70 at its top. The support tank 70 has on its underside an outlet opening on which a three-way valve 72 is arranged. The three-way valve has in addition to the support tank 70 two ports, one is connected to a drain line 74, which can flow to a liquid tank or liquid reservoir, not shown here, from which, for example, the suction line 64 sucks liquid. A second connection of the three-way valve is connected to a filling line 76, which is connected at the top of the centrifugal pump assembly 60 with its pressure side.

When the three-way valve is in a position in which the filling line 76 is connected to the interior of the support tank 70, during operation of the centrifugal pump assembly 60 of the support tank 70 is filled via the filling line 76 with liquid. When the centrifugal pump unit is taken out of service, the liquid from the support tank 70 via the filling line 76 can not flow back into the centrifugal pump unit 60, since the connection of the filling line 76 is located on the centrifugal pump unit 60 above the top of the support tank 70. At the top of the support tank 70, an automatic vent valve 78 is also arranged, through which air can escape from the support tank 70 when it is passed over the filling line 76. However, the vent valve 78 acts only in one direction, ie it is not possible that air flows through the vent valve 78 back into the support tank 70. This is important for the commissioning of the centrifugal pump unit 60th

To this, the three-way valve 72 is brought into a position in which the filling line 76 is closed and the interior of the support tank 70 is connected to the drain line 74. This causes the liquid in the interior of the support tank 70 to flow into the drain line 74 due to gravity. By the drainage of the liquid in the support tank 30, a negative pressure is generated in this, which acts via the vacuum line 68 to the suction line 64 and causes 64 liquid is sucked through the suction line. This is then sucked further by the centrifugal pump unit 60. Thus, the support tank 70 supports by an additional negative pressure, the suction of the centrifugal pump assembly 60 at its startup, so that the suction is accelerated and the normal operating state with full capacity of the centrifugal pump assembly 60 can be achieved faster. In order to prevent that in this normal operation, the centrifugal pump unit 60 sucks the liquid from the support tank 70 via the vacuum line 68, a further check valve 80 is arranged in the vacuum line 68, which liquid flow only from the suction line 64 into the pressure line 68, but not in the opposite direction.

The FIG. 6 shows a second possible embodiment of an additional suction device. Also in this embodiment, a centrifugal pump unit 60 can be used, as it is based on the FIGS. 1 to 4 has been described, ie in particular a self-priming A centrifugal pump unit. Also in Fig. 6 shown centrifugal pump unit 60 is connected to a pressure line 62 and has at a suction nozzle 10, a suction line 64, in which adjacent to the suction nozzle 10, a check valve 66 is arranged, which prevents when decommissioning of the centrifugal pump unit 60 liquid from the centrifugal pump assembly back into the suction line 64 leads. Also in the embodiment according to Fig. 6 branches off from the suction line 64 from a vacuum line 68.

In this vacuum line 68, a Venturi nozzle 82, ie an aspirator is arranged in this embodiment, in which via a compressed air line 84 compressed air is introduced, which is accelerated in the nozzle and thus generates a negative pressure in the vicinity of the nozzle, which via the vacuum line 68 is transmitted to the suction line 64. The compressed air is passed together with any sucked liquid in an outlet line 86, which as the drain line 74 in the embodiment according to Fig. 5 can lead to a liquid tank or reservoir. To start the centrifugal pump assembly according to Fig. 6 the centrifugal pump unit 60 is put into operation and simultaneously compressed air in the Venturi nozzle 82 passed, so that in the vacuum line 68, a negative pressure is generated, which exerts a suction on the suction line 64. Due to the check valve 66 is prevented that liquid is sucked from the centrifugal pump unit 60, so that a suction only takes place via the suction line 64. The negative pressure supports any self-priming properties of the centrifugal pump assembly 60, so that liquid can be sucked faster via the suction line 64 and flow into the centrifugal pump unit 60, so that this accelerates to its normal operating state.

In both embodiments, both in Fig. 5 as well as in Fig. 6 It is essential that the additional suction on the suction side the centrifugal pump unit 60 is arranged. Thus, this suction direction is prevented from being damaged by the pressure generated by the centrifugal pump unit 60 at the normal delivery rate of the centrifugal pump assembly 60.

LIST OF REFERENCE NUMBERS

2

impellers

4

First wheel group

6

impellers

8th

Second impeller group

10

suction

12

pressure channel

14

pressure port

16

wave

18

shaft end

20

separating element

22

Peripheral wall of the separating element

24

Backflow channel

26

openings

28

saugmund

30

seals

32

camp

34, 36

seals

38

Valve

40

wall

42

shell

44

openings

46

Spring plate / valve

48

liquid storage

50

opening

52

peripheral walls

54

outlet

55

check valve

56, 58

coat

60

A centrifugal pump unit

62

pressure line

64

suction

66

check valve

68

Vacuum line

70

support tank

72

Three-way valve

74

drain line

76

filling line

78

vent valve

80

check valve

82

Venturi nozzle

84

Compressed air line

86

outlet pipe

X

longitudinal axis

Claims (13)

Centrifugal pump assembly having at least one centrifugal pump unit (60) characterized by at least one suction device (70, 82) for generating an additional negative pressure in a connected to the suction side of the centrifugal pump assembly (60) suction line (64), wherein the suction device (70, 82) in the suction line (64) is arranged or connected to the suction line (64). Centrifugal pump assembly according to claim 1, characterized in that the suction device (70, 82) adjacent to a suction port (10) of the centrifugal pump assembly (60) in the suction line (64) is arranged or connected to the suction line (64). Centrifugal pump assembly according to claim 1 or 2, characterized in that the centrifugal pump assembly (60) is self-priming. Centrifugal pump arrangement according to one of the preceding claims, characterized in that the suction device has a support tank (70) designed for receiving liquid, which has on its upper side a suction connection (68) which is connected to the suction line (64) and on its underside a Has discharge opening. Centrifugal pump assembly according to claim 4, characterized in that the discharge opening is provided with a valve (72) for opening and closing the discharge opening. Centrifugal pump assembly according to claim 4 or 5, characterized in that the discharge opening opens into a second vertically lower liquid tank. Centrifugal pump assembly according to one of claims 4 to 6, characterized in that the support tank (70) via a filling line (76) is connected to a pressure side of the centrifugal pump assembly (60). Centrifugal pump assembly according to claim 7, characterized in that the filling line (76) opens into the discharge opening of the support tank (70). Centrifugal pump assembly according to claim 8, characterized in that at the discharge opening a three-way valve (72) is arranged, which is designed such that it connects the discharge opening optionally with the filling line (76) or a discharge line (74). Centrifugal pump arrangement according to one of claims 4 to 9, characterized in that in the connection (68) of the suction connection to the suction line (64), a check valve (80) is arranged. Centrifugal pump arrangement according to one of claims 1 to 3, characterized in that the suction device has a Venturi nozzle (82) which is connected via a opening at a constriction of the nozzle vacuum line (68) with the suction line (64). Centrifugal pump assembly according to claim 11, characterized in that the venturi nozzle (82) can be flowed through by a compressed gas, in particular compressed air. Centrifugal pump assembly according to one of the preceding claims, characterized in that between the suction side of the centrifugal pump assembly (60) and the suction device (70, 82) in the suction line (64) a check valve (66) is arranged.

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