EP3121450B1 - Pump for conveying a fluid with varying viscosity - Google Patents

Description

The invention relates to a pump for conveying a fluid with varying viscosity according to the preamble of the independent claim.

In single or multi-stage centrifugal pumps, very large hydraulic forces are often generated, which act in the axial direction, that is, in the direction of the longitudinal axis of the shaft of the pump. These forces must be absorbed by the axial bearing of the shaft. However, since these axial bearings should be kept as small as possible for practical and technical reasons, it is a well-known measure to provide a balance drum on the shaft of the pump to compensate for axial thrust. This comprises a typically essentially cylindrical rotor, which is connected to the shaft in a rotationally fixed manner, and a stator which is arranged coaxially thereto and which is stationary with respect to the pump housing. The stator can, for example, be designed as a separate sleeve or can also be formed by the housing itself. The rotor is dimensioned such that a narrow, annular relief gap is formed between the rotor and the stator. This is connected on the high-pressure side to the space behind the impeller or, in the case of multi-stage pumps, to the space behind the last impeller, so that a leakage flow of the pumped fluid can flow through the relief gap to the low-pressure side of the rotor. From there the fluid is then returned to the inlet of the pump. As a result of the pressure drop across the rotor, a force is generated in the axial direction, which is directed opposite to the hydraulic axial forces generated by the impeller, and thus considerably reduces the forces to be absorbed by the axial bearing.

In the design of the relief piston, the geometric dimensions are very important, in particular the diameter and the axial length of the rotor and the play between rotor and stator, which determines the width of the relief channel in the radial direction.

The leakage flow through the relief channel causes a loss of volume of the pumped fluid, which of course should be kept as low as possible, the leakage flow also having to be so large that the desired technical effects are achieved. As a further effect - and this applies particularly to highly viscous fluids - the fluid flow in the relief channel causes friction which can lead to a considerable and undesirable temperature increase in the relief channel.

In addition to the function of axial thrust relief, the fluid flowing through the relief channel can also contribute to the stabilization or stability of the pump rotor dynamics. Due to the effect known as the Lomakin effect, the fluid flowing in the relief channel generates forces centering the shaft, which have a positive effect on both the damping and the rigidity of the shaft bearings.

Other important parameters that must be taken into account when designing the relief piston are the rotational speed at which the pump is operated, the pressure difference generated, the density of the fluid and the internal friction, i.e. the viscosity, of the fluid being pumped.

When designing the pump hydraulics, efforts are made to achieve the best possible compromise between all these effects, with the fluid properties usually not being influenced and not sufficiently known and therefore only able to be estimated.

There are numerous applications in which the properties of the fluid being conveyed are not constant, but can change more or less quickly.

With multiphase pumps, for example, fluids are conveyed that contain a mixture of several phases, for example one or more liquid phases and one or more gaseous phases. Such pumps have long been well known and are made in numerous embodiments. These pumps can be used in a very wide range of applications, for example in the oil and gas industry for pumping or transporting crude oil or crude oil-natural gas mixtures. The fluid properties can change over time, e.g. B. the phase composition or phase distribution of the multiphase fluid to be pumped. The relative volume proportions of the liquid and the gaseous phase - for example in oil production - are subject to very large fluctuations, which is partly due to the natural source.

However, particularly in the case of crude oil and natural gas production, very strong changes in the viscosity of the fluid can also occur, which will be explained below using an example. When oil fields are exploited or siphoned off, the pressure naturally present in an oil field decreases over time - i.e. with increasing extraction. It is a known technology, when the natural pressure in the oil field decreases, to press water into the oil field by means of so-called injection pumps in order to increase the pressure at the borehole. However, this has the consequence that the pump with which the oil is pumped out of the borehole is confronted with a fluid of varying viscosity or internal friction over the period of the skimming: At the beginning of the skimming, it is usually the natural oil or oil Gas mixture that is being pumped. With increasing water entry into the oil field, the fluid changes at some point to a water-oil emulsion, which has a significantly higher internal friction, which can be orders of magnitude higher than that of the initially produced oil. With further skimming, the proportion of water in the pumped fluid then becomes so large that there is again a sharp drop in viscosity.

This clearly pronounced maximum, which occurs in the course of the viscosity over time when an oil field is siphoned off - usually only after a few years - sometimes makes it necessary to use the pumps with which the oil is extracted from the borehole or transported through pipelines or at least replace their hydraulics. This is of course not desirable for the operator of the oil production, also for economic reasons, he has the need that the pumps used for the production of the crude oil / natural gas can be operated efficiently over the entire period of the extraction of the oil field without replacing the pump or replacing the pump hydraulics .

This is particularly true for those applications in which the pumps are very difficult to access or only accessible with considerable effort. Submarine applications are an example. Nowadays, oil fields are increasingly being siphoned off which are located below the seabed and which can no longer be reached with the classic drilling platforms or can no longer be reached economically. There has therefore been a move towards placing parts of the production equipment, such as pumps, on the seabed near the exit of the borehole. From there, the extracted oil is then transported to processing or storage facilities, which are provided on land, on a drilling platform or on a ship as FPSO (Floating Production Storage and Offloading Unit). Especially in those cases in which the pump is designed as an underwater pump for operation on the seabed, it is of course desirable to have a pump available that can also efficiently and economically convey fluids with highly variable viscosity without having to be replaced for example the pump hydraulics is necessary.

One possible solution is to provide an adjustable valve in the return line, with which the fluid flowing through the relief channel is returned from the low-pressure side of the rotor of the relief piston to the inlet of the pump, so that the return can be throttled more or less strongly . In this way, at least in principle, it is also possible to influence the flow through the relief gap between the rotor and the stator. A throttling in the return line can, however, lead to a considerable reduction in the axial thrust compensation generated by the relief piston, because the pressure drop across the relief piston becomes significantly smaller. However, this means that the hydraulic thrust forces to be absorbed by the axial bearing of the shaft are greater for which this must be designed, because otherwise there is a risk that the axial bearing will be overloaded or subject to significantly higher wear. The documents DE 249 336 C , DE 43 13 455 A1 , WO 2009/135802 and JP H01 237394 A disclose similar arrangements for reducing axial thrust in turbo-machinery by means of relief pistons.

It is therefore an object of the invention to provide a pump that is suitable for efficiently and economically pumping fluids with greatly varying viscosity without having to replace the pump hydraulics, i.e. the impeller or impellers and / or the relief piston.

The subject matter of the invention which solves this problem is characterized by the features of the independent patent claim.

According to the invention, a pump for conveying a fluid with varying viscosity is proposed which has a housing with an inlet and an outlet for the fluid to be conveyed, and at least one impeller for conveying the fluid from the inlet to the outlet, which is arranged on a rotatable shaft , as well as a relief piston for axial thrust relief, wherein the relief piston comprises a rotor fixedly connected to the shaft with a high pressure side and a low pressure side, a stator stationary with respect to the housing, and a relief channel which extends between the rotor and the stator from the high pressure side to the Extends the low-pressure side of the rotor and wherein a return channel is also provided which connects the low-pressure side of the rotor to the inlet, at least one intermediate channel being provided which opens into the relief channel between the high-pressure side and the low-pressure side of the rotor, and where a Blocking member is provided for influencing the flow through the intermediate channel.

The length of the relief channel and thus also the effective length of the rotor of the relief piston can be changed through the intermediate channel and the blocking element. Since, as already mentioned, the diameter and the length of the rotor of the relief piston have a decisive influence both on the flow rate through the relief piston and on the temperature increase caused by friction in the relief channel, an adaptation to strong changes in the viscosity of the fluid can thus be carried out in a very simple manner through the intermediate channel. Functionally, you now have the possibility, as it were, of operating the pump with at least two different relief pistons of different lengths. With a comparatively lower viscosity of the fluid - for example at the beginning of the skimming of an oil field, when essentially only oil or an oil-gas mixture is being pumped - the intermediate channel can be shut off with the blocking element so that the leakage flow over the entire length of the relief piston is guided to the low pressure side of the rotor and discharged from there through the return duct. If there is a sharp increase in viscosity - for example, the described peak in the internal friction of the fluid, which is based on the formation of the oil-water emulsion - the blocking element and thus the intermediate channel are completely opened, so that essentially the entire leakage flow is discharged from the relief channel into the intermediate channel. Since the effective length, that is to say the part of the relief channel through which the flow is flowing, is shortened, the temperature increase generated in the relief gap by friction is also significantly reduced. This is proportional to the ratio of friction and leakage rate. In this way, the pump and in particular the relief piston can be adapted in a simple manner to strong changes in the viscosity of the fluid. It is particularly advantageous that the axial thrust relief generated by the relief piston experiences at least no substantial reduction, if at all, so that no greater load has to be absorbed by the axial bearing of the shaft.

The relief channel preferably comprises an annular space which surrounds the shaft and into which the intermediate channel opens. This ensures that when the intermediate channel is open, the fluid can flow particularly well and evenly from the relief channel into the intermediate channel.

According to a preferred embodiment, the relief channel has a constant width in the radial direction outside the annular space.

The relief channel is divided by the intermediate channel into a first partial channel and a second partial channel, which are arranged one behind the other in the axial direction. The relief channel outside the annular space in the first partial channel or in the second partial channel - particularly preferably in both partial channels - has a constant width in the radial direction. The width of the first partial channel can be the same as the width of the second channel or the first and second partial channels have different widths. Due to the different widths of the two sub-channels, the leakage rate through the relief channel can be easily increased or decreased.

The intermediate channel is preferably connected to the inlet so that the fluid flowing out via the intermediate channel is also returned to the inlet of the pump.

In a preferred embodiment, the intermediate channel opens into the return channel because this simplifies the structural design.

An advantageous measure is that the blocking element is designed as an adjustable flow valve. The flow in the intermediate channel can thus also be set to values between zero and the maximum flow.

Depending on the application, it can also be advantageous if a second blocking element is provided to influence the flow through the return channel. This means that the flow rate can also be actively influenced in the return duct.

According to a preferred embodiment, the blocking element is designed as a three-way valve which is flow-connected to the inlet, to the return channel and to the intermediate channel. Through this measure, the return channel or the intermediate channel can optionally be flow-connected to the inlet of the pump in a particularly simple manner in terms of apparatus.

In a likewise preferred embodiment, a switching element is provided, with which the return channel can be optionally connected to the inlet of the pump or to a source for a second fluid, so that the second fluid can be fed through the return channel to the low-pressure side of the rotor. It is thus possible, for example, to supply a second fluid through the return channel, which fluid can serve as a barrier fluid, for example.

It is of course also possible for the blocking element to be arranged and designed in such a way that the intermediate channel can be connected to a source for a second fluid, so that the second fluid can be introduced into the relief channel through the intermediate channel. The second fluid can e.g. B. be a demulsifier with which the viscosity of the fluid in the relief gap can be reduced. This is also a possibility of introducing a second fluid into the relief channel in order to reduce the viscosity of the fluid here.

Depending on the application, it can also be advantageous if several intermediate channels are provided, each of which opens into the relief channel between the high pressure side and the low pressure side. This measure allows even more different lengths of the relief channel to be implemented.

In particular for applications in places that are difficult to access - for example on the seabed, it is an advantageous measure if the blocking element or the second blocking element or the switching element can be operated by remote control. For this purpose, these organs can be designed, for example, as organs which can be actuated electrically or hydraulically or electro-hydraulically and which can then be remotely controlled, for example, via a signal line or, depending on the application, wirelessly.

The pump according to the invention can in particular also be designed as a multi-stage pump which has at least one second impeller arranged on the shaft for conveying the fluid.

It is also possible to configure the pump according to the invention as a multiphase pump.

The pump according to the invention can particularly preferably also be designed as a centrifugal pump for oil and gas production, in particular as an undersea pump for undersea oil and gas production.

Further advantageous measures and embodiments of the invention emerge from the dependent claims.

Fig. 1:

ein schematische Darstellung eines ersten Ausführungsbeispiels einer erfindungsgemässen Pumpe mit Ausbruch,

Fig. 2:

eine vergrösserte Schnittdarstellung des Entlastungskolbens des ersten Ausführungsbeispiels in einem ersten Betriebszustand,

Fig. 3:

eine vergrösserte Schnittdarstellung des Entlastungskolbens des ersten Ausführungsbeispiels in einem zweiten Betriebszustand,

Fig. 4:

wie Fig. 1, jedoch für eine erste Variante,

Fig. 5:

wie Fig. 1, jedoch für eine zweite Variante,

Fig. 6:

wie Fig. 1, jedoch für eine dritte Variante,

Fig. 7:

eine vergrösserte Schnittdarstellung des Entlastungskolbens in einem Betriebszustand der dritten Variante aus Fig. 6,

Fig. 8:

wie Fig. 1, jedoch für eine vierte Variante,

Fig. 9:

eine vergrösserte Schnittdarstellung des Entlastungskolbens in einem Betriebszustand der vierten Variante aus Fig. 8, und

Fig. 10:

wie Fig. 2 jedoch für ein zweites Ausführungsbeispiels einer erfindungsgemässen Pumpe.

The invention is explained in more detail below with the aid of exemplary embodiments and the drawing. In the drawing show, partly in section:

Fig. 1:

a schematic representation of a first embodiment of a pump according to the invention with a breakout,

Fig. 2:

an enlarged sectional view of the relief piston of the first embodiment in a first operating state,

Fig. 3:

an enlarged sectional view of the relief piston of the first embodiment in a second operating state,

Fig. 4:

how Fig. 1 , but for a first variant,

Fig. 5:

how Fig. 1 , but for a second variant,

Fig. 6:

how Fig. 1 , but for a third variant,

Fig. 7:

an enlarged sectional view of the relief piston in an operating state of the third variant Fig. 6 ,

Fig. 8:

how Fig. 1 , but for a fourth variant,

Fig. 9:

an enlarged sectional view of the relief piston in an operating state of the fourth variant Fig. 8 , and

Fig. 10:

how Fig. 2 but for a second embodiment of a pump according to the invention.

Fig. 1 shows a schematic representation of a first exemplary embodiment of a pump according to the invention, which is designated as a whole with the reference number 1 and is designed as a centrifugal pump or centrifugal pump. In Fig. 1 some parts of the pump 1 are shown in breakout. Fig. 2 shows some parts of the pump 1 in an enlarged sectional view.

The pump 1 has a housing 2 with an inlet 3 through which a fluid to be conveyed can be introduced into the pump 1, as indicated by the arrow E in Fig. 1 symbolizes. Furthermore, the housing 2 has an outlet 4, through which the fluid to be delivered leaves the pump 1, as indicated by the arrow O in FIG Fig. 1 symbolizes. In addition, the pump has a rotatable shaft 5, the longitudinal axis A of which defines an axial direction. In the following, when reference is made to the axial direction, the direction of the longitudinal axis A of the shaft 5 is always meant. The radial direction then means a direction perpendicular to the axial direction.

At least one impeller 7 for conveying the fluid is provided on the shaft 5, from which in Fig. 2 only the upper half is shown. The pump 1 according to the invention can be designed both as a single-stage pump with only one impeller 7 and as a multi-stage pump with at least two impellers 7, which are arranged axially spaced one behind the other on the shaft 5 in a manner known per se. When referring to the impeller 7 in the following, either the single impeller of a single-stage pump is meant or the last impeller 7 of a multi-stage pump, which is the impeller 7 which generates the highest pressure. The pump 1 according to the invention is preferably designed as a multistage centrifugal pump.

Furthermore, the pump 1 according to the invention can be designed as a single-phase pump or as a multi-phase pump. Multiphase pumps are designed for the delivery of multiphase fluids, so they can deliver fluids that contain a mixture of several phases, for example one or several liquid phases, e.g. B. in the form of an emulsion, and one or more gaseous phases. The pump 1 according to the invention is preferably designed as a multiphase pump.

The pump according to the invention is preferably a pump 1 for pumping highly viscous fluids, such as oil or petroleum. In the context of this application, highly viscous fluids mean fluids whose dynamic viscosity is at least 65 cP (centipoise), which corresponds to 0.065 Pa s (Pascal-second) in SI units.

In the following, reference is made, by way of example, to the application, which is important in practice, that the pump according to the invention is used in oil and gas production, for example as a feed pump with which the oil or oil-gas mixture is pumped from the borehole of an oil field or as a transport pump with which the oil or the oil-gas mixture is conveyed through a pipeline. In particular, the pump 1 according to the invention can be designed as an underwater (subsea) pump, which is operated, for example, when extracting oil and gas under the sea on the seabed. It goes without saying, however, that the invention is not restricted to such configurations and applications.

The first embodiment of the inventive pump 1 (see Fig. 1 and Fig. 2 ) has a relief piston 6 for axial thrust relief. With the relief piston 6, a force is generated in the axial direction, which is directed opposite to the axial hydraulic force that is generated by the impellers 7 when conveying the fluid.

The relief piston 6 has an essentially cylindrical rotor 61, which is connected to the shaft 5 in a rotationally fixed manner, as well as a stator 62 which is stationary with respect to the housing 2. The stator 62 can for example be designed as a cylindrical sleeve which is fixedly connected to the housing 2 or parts of the housing 2 itself can form the stator 62. The rotor 61 has a diameter D. It has a high pressure side 65 and a low pressure side 64. The end face on the high pressure side 65 of the rotor 61 is subjected to a high pressure. This is typically done by placing the high pressure side 65 of the rotor 61 with the under pressure standing fluid behind the impeller 7 or behind the last impeller 7 is applied. The high pressure side 65 is then essentially acted upon by the pressure which the fluid has at the outlet 4 of the pump 1. The low-pressure side 64 is subjected to a significantly lower pressure, typically the pressure which the fluid has at the inlet 3 of the pump. This can be implemented, for example, in such a way that the low-pressure side 64 of the rotor 61 is flow-connected to the inlet 3 of the pump via a return duct 8.

The diameter D of the rotor 61 and the inner diameter of the cylindrical stator 62 are dimensioned such that an annular relief channel 63 is formed between the outer surface of the rotor 61 and the inner outer surface of the stator 62, which according to the invention extends between the rotor 61 and the stator 62 from the high pressure side 65 extends in the axial direction up to the low pressure side 64. The width B1 or B2 of the relief channel 63 in the radial direction corresponds to the difference between the inner diameter of the stator 62 and the diameter D of the rotor.

The leakage flow Q through the relief channel 63 causes the following three effects, among others:
First, the leakage flow Q means a volume loss of the fluid delivered by the pump. It is therefore desirable that these leakage losses do not become too great.

Secondly - and this is particularly the case with highly viscous fluids - the fluid generates a considerable amount of heat when flowing through the relief channel 63 by adhering or by rubbing, in particular on the stator 62 and the rotor 61, which leads to significant temperature increases in the relief gap 63 or the components surrounding it. These temperature increases can be so strong, with very highly viscous fluids such. B. 100 ° C and more that the system can no longer be operated safely or that they can damage components of the pump 1.

Thirdly, in addition to the axial thrust relief, the leakage flow Q flowing through the relief channel 63 due to the Lomakin effect causes forces which center the shaft 5, stabilize it and dampen vibrations. This effect has a positive effect on the damping and the rigidity of the shaft bearing.

The leakage flow Q and its effects depend on a large number of parameters, on the one hand on the geometric dimensions of the relief piston 6, which for a given inner diameter of the stator 63 is mainly the diameter D of the rotor 61, which determines the width B1, B2 of the relief channel 63, and the length L of the rotor 63 in the axial direction, which determines the axial length of the relief duct 63. When designing the pump 1, these parameters must be specified for its later use, which often extends over an operating period of many years, and can then only be changed later by replacing the hydraulic components of the pump 1.

The leakage flow Q also depends on the pressure difference that drops across the rotor 61, on the speed, i.e. the speed of rotation of the pump 1, and of course the properties of the fluid to be conveyed, such as its density or viscosity.

When designing a pump 1, the aim is therefore to take all these effects into account and to design the pump so that it can be operated for the respective application for many years, if possible without replacing the hydraulic components.

In order that the pump 1 is particularly suitable for the continuous delivery of a fluid with strongly varying viscosity, it is proposed according to the invention to provide at least one intermediate channel 9 which opens into the relief channel between the high pressure side 65 and the low pressure side 64 of the rotor 61, as well as a blocking element 10 ( please refer Fig. 1 ) to influence the flow through the intermediate channel 9.

This measure allows the length of the relief gap 63 to be varied, which results in particularly good adaptability to variations in the viscosity of the fluid.

In the first exemplary embodiment of the pump 1 described here, the relief channel 63 comprises an annular space 66 which surrounds the shaft 5 and into which the intermediate channel 9 opens. The annular space 66 has a width in the radial direction which is greater than the width B1, B2 of the relief channel 63. Outside the annular space 66, the relief channel 63 has a constant width B1 or B2 in the radial direction as seen over its axial length. Of course, configurations are also possible in which these widths B1 or B2 vary.

The intermediate channel is as in Fig. 1 shown connected to the inlet 3 of the pump. The blocking element 10 is designed at least as an open-close valve which, in a first position, completely blocks the flow connection through the intermediate channel 9 to the inlet 3, and which in a second position completely opens the flow connection through the intermediate channel 9.

Fig. 2 shows the first embodiment of the pump 1 in a first operating state in which the blocking member 10 is in the first position, that is, the flow connection through the intermediate channel 9 closes while Fig. 3 the first embodiment of the pump 1 shows in a second operating state in which the blocking member 10 is in the second position, that is, the flow connection through the intermediate channel 9 opens completely.

The blocking element 10 is preferably designed as an adjustable flow valve 10 with which the leakage flow Q through the intermediate channel 9 can also be set to values between zero and the maximum flow.

Both the return channel 8 and the intermediate channel 9 are each designed, in particular with regard to their diameter, that they have at least no significant throttling effect on the leakage flow Q, ie the respective flow resistance of the return channel 8 and the intermediate channel 9 is dimensioned so that it is significantly smaller is than that Flow resistance of the relief channel 63. This makes it possible to ensure that essentially the entire pressure difference drops across the rotor 61 and that the rotor thus generates the greatest possible axial thrust relief.

The function of the pump 1 and in particular the adaptation to the varying viscosity of the fluid is described below using the example of skimming an oil field with the pump 1.

At the beginning of the skimming of an oil field, it is still under its original, natural pressure and the oil or the oil-gas mixture can often be conveyed with the pump 1 without additional measures. A typical value for the viscosity of the oil in this phase is, for example, 100-200 cP.

In this phase, pump 1 is in the in Fig. 2 first operating state shown. The flow connection through the intermediate channel 9 for the leakage flow Q is blocked with the blocking element 10. The relief channel 63, which has the total length L in the axial direction, is now the series connection of a first sub-channel 631 of the axial length L1, which extends from the high pressure side to the beginning of the annular space 66 and has a radial width B1, as well as a second Partial channel 632 of the axial length L2, which, viewed in the flow direction, extends from the axial end of the annular space 66 to the low-pressure side 64 and has a radial width B2. The effective length of the relief channel 63 is thus the sum of L1 + L2, with natural L1 + L2 being smaller than the total length L. The leakage flow Q therefore flows completely from the high pressure side 65 through the relief channel 63 to the low pressure side 64 and from there through the return channel 8 back to the inlet 3 of the pump.

The width B1 of the first partial channel 631 in the radial direction and the width B2 of the second partial channel 632 in the radial direction are preferably each constant over the axial length L1 of the first and L2 of the second partial channel. The widths B1 and B2 can be the same or different. If you design the widths B1 and B2 differently, this also results the possibility of changing the width of the relief channel, whereby one has another parameter for influencing the leakage flow Q available.

Different widths B1 and B2 can be implemented, for example, in that the rotor 61 has a different diameter D in the area in which it forms the first partial channel 631 than in the area in which it forms the second partial channel 632. Of course, it is also possible to make the diameter D of the rotor 61 constant over its entire axial length L and to configure the stator 62 in the area of the first sub-channel 631 with a different inner diameter than in the area of the second sub-channel 632. Furthermore, a combination of the two measures possible, so to design both the inner diameter of the stator 62 and the diameter D of the rotor over the respective axial length L differently.

As described at the beginning, the natural pressure in the oil field decreases as the oil field is increasingly extracted and, for example, water begins to be pressed into the oil field in order to increase the pressure in the oil field again or to compensate for the pressure drop. As a result of this water injection, the formation of an emulsion from the oil and the water increases with increasing time, and this emulsion must now be conveyed by the pump 1. The formation of the emulsion can be associated with a drastic increase in internal friction or viscosity, which can vary in the order of magnitude. This peak in viscosity over time when the oil field is siphoned off is known and, for example, can only occur after a few years of siphoning.

If the viscosity of the fluid now rises sharply, this on the one hand reduces the leakage flow Q but on the other hand leads to a drastic increase in the heat generated in the relief gap 63 and thus to a significant rise in temperature. In order to avoid this temperature rise in particular, the pump is now switched to the second operating state, which is shown in Fig. 3 is shown.

The blocking element 10 is now brought into the position in which it completely opens the flow connection through the intermediate channel 9 for the leakage flow Q. Since the intermediate channel 9 now represents the considerably lower resistance for the leakage flow Q than the second partial channel 632 of the relief channel 63, the predominant part of the leakage flow Q flows from the high pressure side 65 through the first partial channel 631 of length L1 into the annular space 66 and from there the intermediate channel 9 to the inlet 3 of the pump 1. The effective length of the relief channel 63 is now only the length L1 of the first sub-channel 631 and thus significantly smaller than in the first operating state. In this way it can be achieved that the leakage rate is increased and the heat generated in the relief channel 63 is considerably smaller, and thus also the resulting temperature increase. If, in addition, the first sub-channel 631 is designed with a greater radial width B1 than the second sub-channel 632, the effective width of the relief channel 63 is also increased, whereby the leakage flow Q can additionally be increased.

As the oil field continues to be skimmed off, the proportion of water in the pumped fluid becomes greater and greater, as a result of which the viscosity drops again drastically after passing through the maximum caused by the emulsion formation. The pump 1 can now be brought back into the first operating state by closing the locking member 10, which is shown in FIG Fig. 2 is shown.

The suitable choice of the ratios of the lengths L1 to L2 or L1 to L or L2 to L and the widths B1 or B2 in the radial direction depends on the particular application. Typically, before a new oil field is siphoned off, calculations are made with regard to the long-term behavior of the siphon. For example, on the basis of such calculations, a suitable value for L, L1, L2 and the widths B1, B2 of the relief duct 63 or the diameter D of the rotor 61 can then be determined with the aid of model calculations or simulations.

It goes without saying that deviating from the representation in Fig. 1 Configurations are also possible in which the intermediate channel 9 opens into the return channel 8 downstream of the blocking element 10.

Fig. 4 shows a first variant for the embodiment of the pump 1. In this variant, a second blocking element 12 is provided for influencing the flow through the return channel 8. The blocking element 12 can also be designed as an open-close valve 12 or as an adjustable flow valve with which the leakage flow Q through the return duct 3 can be adjusted.

Fig. 5 shows a second variant for the embodiment of the pump 1. In this second variant, the intermediate channel 9 opens into the return channel 8. The blocking element 10 is provided at this junction, the blocking element being designed as a three-way valve 10 which is flow-connected to the inlet 3, to the return duct 8 and to the intermediate duct 9. To implement the first operating state ( Fig. 2 ) the three-way valve 10 is switched so that it connects the return channel 8 with the inlet 3, so that the leakage flow Q can flow through the return channel 8 to the inlet 3. In this position, the intermediate channel 9 is blocked so that no leakage flow Q can flow out through it. To implement the second operating state ( Fig. 3 ) the three-way valve 10 is switched so that it connects the intermediate channel 9 with the inlet 3, so that the leakage flow Q can flow from the annular space 66 through the intermediate channel 9 to the inlet 3. In this position the return channel 8 is blocked so that no leakage flow Q can flow out through it.

Fig. 6 illustrates a third variant of the exemplary embodiment of the pump 1. In this third variant, a switching element 13 is provided in the return duct 8, with which the return duct 8 can be optionally connected to the inlet 3 of the pump 1 or to a source 15 for a second fluid, so that the second fluid can be fed through the return channel 8 to the low-pressure side 64 of the rotor.

Fig. 7 shows in one too Fig. 2 or. Fig. 3 analog representation of an operating state of the third variant Fig. 6 . In this operating state, the switching element 13 is set in such a way that it connects the return duct 8 to the source 15 for the second fluid and the flow connection to the inlet 3 of the pump 1 is blocked. The second fluid is, for example, a barrier liquid such as water or another suitable medium or a Cooling fluid, with which a counterpressure can be generated in the second partial channel 632 of the relief channel 63. In Fig. 7 the flow of the second fluid is indicated with dotted lines provided with arrows. The second fluid flows through the return duct 8 to the low-pressure side 64 of the rotor and from there through the second sub-duct 632 of the relief duct 63, counter to the leakage flow Q. The two fluids combine in the area of the annular space 66 and are discharged together through the intermediate channel. The second fluid can be used, for example, to generate a counterpressure in the relief channel 63 in order to reduce the flow rate of the leakage flow Q or to remove heat from the relief gap 63.

Fig. 8 shows a fourth variant of the first embodiment of the pump 1. In this fourth variant, the blocking element 10 is arranged and designed such that the intermediate channel 9 can be connected to a source 16 for a second fluid, so that the second fluid flows through the intermediate channel into the relief channel 63 can be brought in. The blocking element 10 is preferably designed here as a three-way valve 10, which optionally connects the intermediate channel 9 to the inlet 3 of the pump 1 or to the source for the second fluid.

Fig. 9 shows in one too Fig. 2 or. Fig. 3 analog representation of an operating state of the fourth variant Fig. 8 . In this operating state, the three-way valve 10 is set such that it connects the intermediate channel 9 to the source 16 for the second fluid and the flow connection to the inlet 3 of the pump 1 is blocked. The second fluid is, for example, a demulsifier with which the viscosity of the leakage flow Q can be reduced, or water to dilute the leakage flow Q, or a cooling fluid with which heat can be removed from the relief gap 63. In Fig. 9 the flow of the second fluid is indicated with dotted lines provided with arrows. The second fluid flows through the intermediate channel 9 into the annular space 66, where it connects with the leakage flow Q and flows together with the latter through the second sub-channel 632 of the relief channel 63 to the low-pressure side 64. From there, the leakage flow Q is discharged together with the second fluid through the return channel 8.

It goes without saying that the four variants described here or the measures explained can be combined with one another in any way.

Fig. 10 shows in one to Fig. 2 analogous representation of a second exemplary embodiment of a pump 1 according to the invention. In the following, only the differences from the first exemplary embodiment will be discussed. The reference symbols have the same meaning as already explained in connection with the first exemplary embodiment. The explanations relating to the first exemplary embodiment and all of its variants also apply in the same way or in a similar manner to the second exemplary embodiment.

In the second exemplary embodiment of the pump 1 according to the invention, a second intermediate channel 9 ′ is also provided, which likewise opens into the relief channel 63 between the high pressure side 65 and the low pressure side 64. A further blocking element 10 'is provided for this second intermediate channel 9', with which the leakage flow Q in the second intermediate channel 9 'can be influenced. In particular, the second intermediate channel 9 'can be blocked by means of the further blocking element 10' so that no leakage flow Q can flow through it and the second intermediate channel 9 'can be flow-connected to the inlet 3 of the pump 1 by means of the further blocking element 10', so that the Leakage flow Q can flow through the second intermediate channel 9 'to the inlet of the pump 1.

Furthermore, the relief channel 63 has a second annular space 66 'which surrounds the shaft and in which the second intermediate channel 9' opens.

In this configuration with the two intermediate channels 9, 9 ', the flow-related relief channel 63 corresponds to the series connection of three sub-channels, namely a first sub-channel 631 of axial length L1, which extends from the high pressure side 65 to the beginning of the annular space 66, of a second sub-channel 632 the axial length L2, which extends from the end of the annular space 66 to the beginning of the second annular space 66 'and a third sub-channel 633 of the axial length L3, which extends from the end of the second annular space 66' to the low-pressure side 64 of the rotor 61. The respective width B of the sub-channels 631, 632, 633 is in Fig. 10 For the sake of clarity, it is only referred to as B in summary. It goes without saying, however, that in the same way as in the first embodiment, each sub-channel 631, 632, 633 can have a different width in the radial direction, or that the same width is selected in the radial direction for two of the sub-channels and for the remaining sub-channel 631 or 632 or 633 have a different width. Of course, the same width B in the radial direction can also be selected for all three sub-channels 631, 632, 633. The width B is preferably constant within a sub-channel, but can also vary.

With this configuration, a total of three relief channels of different lengths can be implemented in the operating state. If the leakage flow Q is allowed to flow away through the return channel 8, the effective length of the relief channel 63 in the axial direction is L1 + L2 + L3, this effective length of course being smaller than the total length L.

If the leakage flow Q is allowed to flow off through the second intermediate channel 9 ', as shown in FIG Fig 10 is shown, then the effective length of the relief channel 63 in the axial direction is L1 + L2.

If the leakage flow Q is allowed to flow away through the first intermediate channel 9, then the effective length of the relief channel 63 is only L1.

In this way, several relief channels 63 can be implemented, all of which have different lengths in the axial direction and can also have different widths B in the radial direction.

Of course, the intermediate channels 9, 9 'or the return channel 8 can also be used here to supply a second fluid.

It goes without saying that, in a similar manner, more than two intermediate channels 9, 9 ′ can also be provided, each of which opens into the relief channel 63.

In the case of the pump 1 according to the invention, it is also possible to assemble the rotor 61 and / or the stator 62 from several parts. It is therefore by no means necessary for the rotor 61 or the stator 62 to be designed in one piece. It is also possible to design the rotor 61 or the stator 62 so that the relief gap 63 does not have a constant width B1, B2, B outside of the annular spaces 66, 66 ', but tapers or widens, for example, as seen in the axial direction. It is also possible to coat or structure the jacket surface of the rotor 61 or the inner jacket surface of the stator 62. Furthermore, it is possible to provide one or more swirl brakes on the high pressure side 65 in the area of the entrance to the relief channel 63 and / or in the relief channel 63, for example at the entrances to the respective sub-channels 631, 632, 633, with which the fluid flows be deflected in the circumferential direction around the shaft 5 in the axial direction.

The blocking element 10, 10 'and the second blocking element 12 can be designed as open-close valves with which the flow through the respective channel is either completely released or completely blocked. However, it is also possible to design the blocking element 10, 10 'or the second blocking element 12 as an adjustable flow valve with which the flow in the respective channel can be set to any values between zero and a maximum value.

The blocking element 10, 10 'or the second blocking element 12 or the switching element 13 can be designed so that they can be operated remotely, for example in the case of submarine applications via a signal line via which a preferably electrical or hydraulic signal is passed, which is the respective blocking element or Switching element switches or regulates in the respectively desired state. The remote-controlled operability can also be configured without signal lines.

Of course, such designs of the locking members 10, 10 ', 12 or the switching member 13 are also possible in which the respective member 10, 10', 12 or 13 is operated manually, that is to say by hand. For submarine applications, this manual setting can also be made with the help of diving robots.

Claims (15)

1. A pump for conveying a fluid with varying viscosity which has a housing (2) having an inlet (3) and having an outlet (4) for the fluid to be conveyed, as well as having at least one impeller (7) for conveying the fluid from the inlet (3) to the outlet (4), the impeller being arranged on a rotatable shaft (5), as well as having a balance drum (6) for the relief of axial thrust; wherein the balance drum (6) comprises a rotor (61) rotationally fixedly connected to the shaft (5), the rotor having a high pressure side (65) and a low pressure side (64), a stator (62) stationary with respect to the housing (2) and a relief passage (63) that extends between the rotor (61) and the stator (62) from the high pressure side (65) up to the low pressure side (64) of the rotor (61); wherein further at least one intermediate passage (9, 9') is provided which opens into the relief passage (63) between the high pressure side (65) and the low pressure side (64) of the rotor (61), and wherein a blocking member (10, 10') is provided for the influencing of the flow through the intermediate passage (9, 9'), characterized in that a return passage (8) is further provided which connects the low pressure side (64) of the rotor (61) to the inlet (3), and in that the relief passage (63) extends in the axial direction from the high pressure side (65) to the low pressure side (64).
2. A pump in accordance with claim 1, in which the relief passage (63) comprises a ring space (66, 66'), which surrounds the shaft (5) and into which the intermediate passage (9, 9') opens.
3. A pump in accordance with claim 2, in which the relief passage (63) has a constant width (B1, B2, B) in the radial direction outside of the ring space (9, 9') in a first part passage (61) of the relief passage (63) or in a second part passage (62) of the relief passage (63).
4. A pump in accordance with any one of the preceding claims, wherein the intermediate passage (9) is connected to the inlet (3).
5. A pump in accordance with any one of the preceding claims, wherein the intermediate passage (9) opens into the return passage (8).
6. A pump in accordance with any one of the preceding claims, wherein the blocking member (10) is configured as a settable through-flow valve.
7. A pump in accordance with any one of the preceding claims, wherein a second blocking member (12) is provided for the influencing of the flow through the return passage (8).
8. A pump in accordance with any one of the preceding claims, wherein the blocking member (10) is configured as a three-way valve which is connect-ed to the inlet (3), to the return passage (8) and to the intermediate passage (9) in a flow communicating manner.
9. A pump in accordance with any one of the preceding claims, wherein a switching member (13) is provided by means of which the return passage (8) can be selectively connected to the inlet (3) of the pump (1) or to a source (15) for a second fluid, in such a way that the second fluid can be supplied to the low pressure side (64) of the rotor (61) through the return passage (8).
10. A pump in accordance with any one of the preceding claims, in which the blocking member (10) is arranged and configured in such a way that the intermediate passage (9) can be connected to a source (16) for a second flu-id in such a way that the second fluid can be introduced into the relief pas-sage (63) through the intermediate passage (9).
11. A pump in accordance with any one of the preceding claims, wherein a plurality of intermediate passages (9, 9') are provided of which each opens into the relief passage (63) between the high-pressure side (65) and the low pressure side (64).
12. A pump in accordance with claims 1 or 7 or 9, in which the blocking member (10, 10') or the second blocking member (12) or the switching member (13) can be operated in a remote-controlled manner.
13. A pump in accordance with any one of the preceding claims, configured as a multi-stage pump that has at least one second impeller (7) arranged at the shaft for the conveyance of the fluid.
14. A pump in accordance with any one of the preceding claims, configured as a multi-phase pump.
15. A pump in accordance with any one of the preceding claims, configured as a centrifugal pump for the conveyance of oil and gas, in particular as a sub-sea pump for the sub-sea conveyance of oil and gas.

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