EP2669525A1 - Centrifugal pump assembly - Google Patents

Abstract

The centrifugal pump has an impeller that is rotatably mounted on a shaft, which is sealed off by seal (11) to a surrounding housing. The seal is opened towards a container (12) for the collection of the fluid, and is configured to detect fluid in or out of the container. The container is annular and is configured to surround the shaft. A sensor (20) configured for detecting the flow rate of drops. A discharge opening is followed by the tubes (21,22) formed by the sensor whose other end is open to the outside or to a discharge line.

Description

The invention relates to a centrifugal pump, in particular a multi-stage centrifugal pump, which is provided for driving by means of a motor designed as a dry rotor, which is connected via a coupling with the pump driving shaft.

Centrifugal pumps have at least one impeller which is rotatably mounted on a shaft which is sealed by means of at least one seal to a surrounding housing. In particular, in the aforementioned multi-stage centrifugal pumps, the unilaterally emerging from the pump housing drive shaft is sealed with a mechanical seal, which is to prevent leakage of the fluid located within the housing along the outside of the shaft. Especially in multi-stage pumps, the pressure in this area of the housing is comparatively high, so that a complete tightness can only be achieved with great difficulty. The higher the contact pressure of the seal is applied, the less liquid can escape through the sealing gap. However, as the sealing gap narrows, the frictional forces which must be additionally applied by the drive, which are converted exclusively to heat and which worsen the efficiency, grow. Also associated with increasing friction wear, which negatively affects the life of the seal. With this in mind, it has been found that in many applications, particularly those involving the pumping of water, it would be advantageous to accept a small flow of fluid through the seal, thereby minimizing frictional forces and to increase the service life of the seal. However, this assumes that the passage of fluid through the seal is monitored to ensure that it does not become unduly high.

Against this background, the invention has the object, a centrifugal pump in such a way that the liquid passage can be detected in the shaft seal.

According to the invention, this is achieved in a centrifugal pump having the features mentioned above in that a seal open towards the container is provided, which is designed and arranged so that it passes through the seal fluid, in particular passing through the seal liquid and means are further provided which detect the liquid in the container or from the container, d. H. Means that detect the liquid level within the container or the effluent from the container. An open towards the seal container in the context of the invention is a container which is open to the sealing gap between the seal and the shaft, d. H. that it can absorb liquid emerging along the shaft or on the seal.

The centrifugal pump according to the invention, which has at least one impeller which is rotatably mounted on a shaft which is sealed by means of at least one seal to a surrounding housing, has a container disposed in the housing and open at least to seal container for collecting passing through the seal Fluid and is equipped with means for detecting liquid in or out of the container.

The basic idea of the present invention is therefore to detect and monitor the passage of fluid through the seal, which is a prerequisite for safe operation, in which the passage of a certain amount of liquid is tolerated. This operation makes it possible to significantly reduce the frictional forces in the region of the seal and thus to improve the efficiency of the unit and continue to increase the service life of the seal. The arrangement according to the invention controls the fluid passing through the seal, in particular in liquid form, and thus monitors the seal during its operation. The arrangement according to the invention therefore not only has the aforementioned advantages in operation, but also provides a reliable function monitoring of the seal, so it determines early when the seal or the seals wear before they fail completely. The arrangement according to the invention can thus be used not only in pumps in which a liquid passage through the seal is deliberately accepted, but also in those pumps in which this is by no means desirable. So not only mechanical seals but also any other seals, such as O-rings can be monitored for their tightness out.

In order to reliably detect the liquid passing through the sealing gap, according to a development of the invention the container is annular, the shaft formed surrounding. Thus, the fluid emerging from the pump housing at the periphery of the shaft or at the seal can be collected in the annular container. It is possible either to detect the liquid in the container in terms of the amount, so typically the level height in the container or to provide a drain in the container and to detect the liquid passing through this drain.

Particularly advantageously, the liquid is detected by means of electrical contacts, so there are at least two mutually electrically insulated contacts provided, which are electrically connected by the liquid become. Such an arrangement is inexpensive, in operation not susceptible to interference, since there are no moving parts and easy to handle in terms of evaluation. Typically, two states are to be detected electronically, namely the state in which the contacts are connected by gas, typically the ambient air, and the state in which the contacts are connected by liquid. The ohmic resistances of these two states are sufficiently different, detection in the non-hazardous low voltage range is readily possible, the evaluation electronics can largely be done by digital logic devices.

In order to detect a liquid level within the container, according to a development of the invention, three or more contacts can be arranged at different heights within the container so that the liquid level within the container can be detected in stages.

Advantageously, the container has a drain opening, through which the liquid in the container is selectively discharged preferably to the outside. In particular, in the promotion of water a discharge of small amounts to the outside is usually unproblematic and tolerable.

It is particularly advantageous if a sensor for detecting the flow, in particular a sensor for detecting drops, is arranged in or at the drain opening, since this allows the quantity of outflowing liquid to be detected in a simple and effective manner. Such a drop sensor is sufficient, since in a preferred sealing gap dimensioning a liquid outlet is tolerated, which is at a few drops per minute or per hour.

According to one embodiment of the invention, such a sensor can be formed by means of two mutually electrically isolated contacts whose spacing is dimensioned so that they are electrically connected by a passing liquid drop. Here, in a similar manner, a resistance measurement, as already described in the introduction of the level detection.

To be particularly advantageous, it has been found to form the sensor by two mutually electrically insulated but electrically conductive, preferably metallic tubes which are coaxial with each other and in which the inner tube ends at a distance from the end of the outer tube. These tubes are tightly incorporated in the drainage opening of the container and preferably arranged approximately at an angle of 45 ° to the vertical. They typically consist of stainless steel and are electrically connected to the evaluation electronics. When a drop emerging from the container enters the discharge opening, it initially passes through the inner tube obliquely downwards and outwards until it reaches the outer tube at the end of the inner tube. In this case, the distance of the tubes is dimensioned so that the passage of the drop, a short circuit between the two tubes or an electrical connection through the drop, so the liquid is produced, which differs from the normal air connection resistance and thus is detectable. With this sensor, not only the dry state and a continuous drop can be detected, but also a continuous flow, ie when a trickle forms, which short-circuits the contacts permanently. By dimensioning the distance of the contacts to each other, the sensitivity of the sensor can be adjusted. If the distance is greater than that of a drop, then the sensor is only suitable for detecting rinses that permanently short the contacts.

The centrifugal pump or the centrifugal pump assembly formed therewith is particularly advantageously one in which the shaft is arranged vertically and the pump is sealed at the top with a mechanical seal in which the container is arranged between pump and motor and the container at the bottom Has drain opening, followed by the sensor formed by tubes, the other end opens into the open or in a drain line. Such a design is typically provided in multi-stage centrifugal pumps, such as those offered by the company Grundfos in the type series CR.

The container, which catches the fluid emerging through the seal and the means for detecting the liquid in or out of the container can be realized in particular in the above-described multi-stage pump with a few inexpensive to produce components, the arrangement in an already existing space is not a problem. In particular, for the use of mechanical seals, such an arrangement is advantageous because it allows a seal dimensioning, which allows a targeted low leakage, so as to improve the friction within the seal and the life of the seal can.

However, the arrangement is not limited to mechanical seals and can be used in the same way for monitoring O-rings or other seals. In this case, the sensor according to the invention has two mutually electrically insulating and conductive tubes which lie in one another and from which the inner tube ends at a distance from the end of the outer tube. Such a sensor can be provided not only on the above-described container but optionally also on other housing parts to detect leakage and not only qualitatively but also quantitatively. The sensor is inexpensive to manufacture, robust and long-term stable. The evaluation based on the changing resistance when overflowing a drop is technically less complex and easy to implement electronically.

Fig. 1

in vereinfachter perspektivischer Darstellung eine mehrstufige Kreiselpumpe mit angeschlossenem Antriebsmotor,

Fig. 2

den oberen Teil des Aggregats gemäß Fig. 1 in Seitenansicht,

Fig. 3

die Einzelheit III der Fig. 2,

Fig. 4

die Gleitringdichtung mit Behältnis, Sensor und Elektronikeinheit in perspektivischer Darstellung ohne das Pumpenaggregat und

Fig. 5

einen Schnitt durch das Behältnis und den Sensor in der Ablauföffnung.

The invention is explained in more detail with reference to an embodiment shown in the drawing. Show it:

Fig. 1

in a simplified perspective view of a multi-stage centrifugal pump with attached drive motor,

Fig. 2

the upper part of the unit according to Fig. 1 in side view,

Fig. 3

the detail III of Fig. 2 .

Fig. 4

the mechanical seal with container, sensor and electronic unit in perspective view without the pump unit and

Fig. 5

a section through the container and the sensor in the drain opening.

This in Fig. 1 Pump unit shown has a multi-stage centrifugal pump 1, whose shaft is not visible in the drawings is perpendicular and exits at the top of the pump housing 2, where it is connected via a coupling 3 with the shaft of an electric motor 4, which is mounted on a motor chair 5 on the Top of the pump housing 2 is flanged. The electric motor 4 is a dry runner.

The pump housing 2 has a base-side foot 6 with two inline connection flanges 7 and 8, one of which the Suction port and the other forms the pressure port of the pump 1. The individual pump stages are arranged within a stainless steel jacket, which extends between the foot 6 and an upper housing part 9, which also forms the motor chair 5. The housing parts 6 and 9 are clamped together in the usual way via tie rods 10.

In the upper housing part 9, which forms the pump head and has clearance for the coupling 3, the end of the shaft emerging from the pump housing 2 is sealed by means of mechanical seals with respect to the pump housing 2.

The mechanical seals are arranged in a cartridge-like housing 11, the so-called slide ring cartridge and correspond to the built-in example in the CR series Grundfos conventional seal cartridges, with which the pump shaft is sealed against the pump housing 2.

At the, surrounding the shaft seal housing 11, which includes the mechanical seals, closes up to a container 12, which is formed as an annular, upwardly open and lockable by a cover 13 housing. The container 12 has on its underside two concentric arranged in different planes grooves 14 and 15, which are directed downwards and are provided for receiving in each case an O-ring. By means of these lying in the grooves 14 and 15 O-rings a tight connection to the underlying seal housing 11 is ensured to ensure that all, exiting from the sealing gap in the shaft and mechanical seal fluid is fed into this container 2. Since a close seal of the underside of the container 12 is formed over the lying in the grooves 14 and 15 O-rings against the top of the seal housing 11, passes through the sealing gap in Beriech shaft and mechanical seal leaking fluid with increasing amount along the shaft through the central opening 16 and the annular gap formed between the shaft and this central opening 16 upwards into the container 12, where it has an inwardly outwardly sloping annular surface 17 in a circumferential and upwardly open groove 18 is led. This groove 18 has an installation opening in an obliquely downwardly extending drain opening 19, in which a sensor 20 is incorporated, which is formed from two metallic tubes 21 and 22, which are electrically insulated from each other. The inner tube 21, which immediately adjoins the drain opening 19, opens into an outer tube 22 which engages over the free end of the inner tube 21 and ends in the open air. The inner tube 21 and the outer tube 22 form electrical contacts, which are connected via an electrical cable 23 to a arranged in an electronics housing 24 evaluation electronics. In the installed position, the outer tube 22 projects obliquely downwards and outwards, so that liquid emerging therefrom passes into the side region of the pump housing. The electronics housing 24 is rotationally offset from the sensor 20 and mounted below the motor chair 5 within the upper housing part 9. From the electronics housing 24 lead from electrical connections, not shown, to the control electronics of the engine, which is arranged in the illustrated embodiment in a terminal box 25 which receives an electronic speed controller of the engine and the control electronics for it.

If during operation of the pump, so if due to the pressure generated within the pump discharge fluid through the mechanical seals, ie at the top of the seal housing 11 wellnahah, this can not be removed laterally due to the lateral seals of the container 12 in the seal housing 11, but rises to in the container 12, where it finally reaches the annular surface 17 after passage of the container bottom and gravity flows into the circumferential groove 18. From there, the liquid then enters the drain opening 19 and the sensor 20. A flowing into the sensor 20 Drop of liquid first flows through the inner tube 21 further down and out until it passes from the inner tube 21 into the outer tube 22 and thereby creates an electrical connection between the two tubes, whereby the contact resistance of previously changed air in the pumped liquid. This is registered by the evaluation electronics, so that when using this arrangement, it is firstly possible to reliably detect whether the shaft seal is leak-tight or allows fluid to pass through. If it lets fluid through it can be further detected, how much liquid this is. Small amounts will only be single drops, and the approximate amount can be determined by the time interval between the overflowing drops. Once a trickle forms, the electrical connection between the inner tube 21 and the outer tube 22 is permanently short-circuited by liquid, which is also registrable. Optionally, by arranging a further tube, the sensor can be refined, so that at least a coarse flow rate can be determined in a trickle formation. This is done by the distance between the inner and outer tube is further increased, the larger it is, the greater must be the passing amount of water, which causes a permanent short circuit between the pipes. In this way, the sensor can be refined in terms of its quantitative measurement properties.

Although the arrangement described above is illustrated and described with reference to a centrifugal pump unit with a multi-stage centrifugal pump of the inline type with vertical shaft, it is understood that according to the principle of the invention in a defined position of a pump with the inventive arrangement on the pump and a Variety of other pump types can be monitored with regard to the function of their seal.

LIST OF REFERENCE NUMBERS

1

rotary pump

2

pump housing

3

clutch

4

electric motor

5

motor bracket

6

Walk from the pump housing

7

flange

8th

flange

9

Upper housing part

10

tie rods

11

seal housing

12

container

13

Lid of 12

14

groove

15

groove

16

central opening

17

ring surface

18

upwardly open groove

19

drain hole

20

sensor

21

inner tube

22

outer tube

23

electric wire

24

electronics housing

25

terminal box

Claims (10)

Centrifugal pump, in particular multi-stage centrifugal pump (1) with at least one impeller, which is rotatably mounted on a shaft which is sealed by at least one seal (11) to a surrounding housing (2) with one on the housing (2) and at least container open to the seal (11) for collecting fluid passing through the seal (11) and means for detecting liquid in or out of the container (12). Centrifugal pump according to claim 1, wherein the container (12) is annularly formed surrounding the shaft. Centrifugal pump according to claim 1 or 2, wherein the means for detecting liquid at least two mutually electrically isolated contacts (21, 22), which are electrically connected by the liquid. Centrifugal pump according to one of the preceding claims, wherein three or more contacts are arranged at different heights within the container (12). Centrifugal pump according to one of the preceding claims, wherein the container (12) has a drain opening (19) to the outside. Centrifugal pump according to one of the preceding claims, wherein at the drain opening (19) a sensor (20) for detecting the Flow, in particular a sensor (20) for detecting drops is arranged. Centrifugal pump according to one of the preceding claims, wherein the sensor (20) has two mutually electrically isolated contacts (21, 22) whose spacing is dimensioned such that they are electrically conductively connected by a passing liquid drop. Centrifugal pump according to one of the preceding claims, wherein the sensor (20) by two mutually electrically insulated and electrically conductive preferably metallic tubes (21, 22) is formed coaxially with each other, wherein the inner tube (21) at a distance from the end the outer tube (22) ends. Centrifugal pump according to one of the preceding claims, wherein the shaft is arranged vertically and the pump is sealed at the top with a mechanical seal (11), wherein the container (12) between the pump (1) and a motor driving this (4) is arranged and below a drain opening (19), to which the tube (21, 22) formed sensor (20) connects, the other end opens into the open or into a drain line. Sensor, in particular for a centrifugal pump according to one of the preceding claims, comprising two mutually electrically insulated and conductive tubes (21, 22) which lie in one another and of which the inner tube (21) spaced from the end of the outer tube (22) ends.

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