EP3163086A1 - Pump drive unit for process fluid conveying - Google Patents

Abstract

There is proposed a pump-drive unit for conveying a process fluid, comprising a common housing (4) having a pump (2) with an impeller (21) for rotation about an axial direction (A) and a drive (3) for the pump (2) encloses, with a shaft (5) for driving the impeller (21) which connects the drive (3) with the pump (2), and with a throttle (13) which surrounds the shaft (5 ), which is provided between the impeller (21) and the drive (3), wherein the housing (4) comprises a pump inlet (22) and a pump outlet (23) for the process fluid, wherein an inlet (43) for a barrier fluid is provided, through which the barrier fluid in the drive (3) can be introduced, and an outlet (44) for the barrier fluid, through which the barrier fluid from the housing (4) can be discharged, and wherein on the shaft (5) in Region between the throttle (13) and the drive (3) a plurality of storage chambers (11) for the barrier fluid before It is seen which storage chambers (11) are arranged one behind the other with respect to the axial direction (A), wherein in each case two adjacent storage chambers (11) are in fluid communication with one another.

Description

The invention relates to a pump-drive unit for conveying a process fluid according to the preamble of the independent claim.

Pump-drive units in which a pump with an impeller and a drive for the pump are enclosed by a common housing, are often used for those applications in which the pump is completely or completely in a liquid, eg. As water immersed, or when the pump is operated in hard to reach places or in difficult conditions or environmental conditions.

An example of application for this are pumps which are used for the ebullated bed process in the hydrocarbon processing industry. These methods are used, for example, heavy hydrocarbons, eg. As heavy oil, or refinery residues to clean or break up into better usable volatile hydrocarbons. This is often done by charging the heavy hydrocarbons with hydrogen, the mixed components are swirled in a reactor and there with the aid of catalysts, the heavy hydrocarbons are broken. In order to circulate the process fluid, which usually consists mostly of heavy hydrocarbons, in the boiling-bed or fluidized-bed reactor, special pump-drive units are used, for which the term Ebullator pump (ebullating pump) has been naturalized. These Ebullatorpumpen are provided as circulation pumps for the process fluid usually directly on the reactor and are Process designed such that the pump is arranged with respect to the vertical above the drive. Ebullator pumps have to work as reliably as possible under extreme challenging conditions and over a long period of time in continuous operation.

Because typically the process fluid is due to the process under a very high pressure of for example 200 bar or more, and has a very high temperature of more than 400 ° C, z. B. 460 ° C. Therefore, the housing of such pump-drive units is designed as a pressure housing, which can withstand these high operating pressures. The drive is usually designed as an electric motor, which is also exposed to the high operating pressure within the housing. The motor must be sufficiently protected against the ingress of process fluid, which is why the motor is usually filled with or flowed through a barrier fluid, which additionally serves for lubrication and heat removal from the engine. In this case, embodiments are possible as completely oil-filled motors or as canned motors (canned motor) or as so-called "cable wound" motors.

In engines that are completely filled with oil, both the rotor and the stator are completely surrounded by the barrier fluid or submerged in it. Therefore, for this embodiment, the barrier fluid must be a dielectric fluid, e.g. a dielectric oil to avoid a short circuit in the motor.

In the case of the canned motor, a gap tube is provided between the stator and the rotor, which terminates the stator hermetically with respect to the rotor, wherein the rotor is usually also protected by a jacket. In the embodiment as a canned motor, the barrier fluid is usually passed through the gap between the rotor and the can.

In the case of the cable-wound motor, the electrical cables with which the stator winding is wound are surrounded by an electrically insulating jacket.

Since the canned motor and the cable-wound motor caused by the barrier fluid short circuit is not possible in these Embodiments, a different barrier fluid may be used as a dielectric fluid. This is advantageous for many applications, among others, for the reason that you can choose a barrier fluid with the best possible cooling and lubricating properties, without taking into account its electrical conductivity properties.

Embodiments are also known in which the process fluid itself is used as a barrier fluid for cooling and lubricating the engine, but for many applications it is essential that the engine is sufficiently protected against ingress of the process fluid. For example, heavy hydrocarbons as process fluid, which are left as residues in the distillation of petroleum, very often contain chemically aggressive and / or abrasive substances, so that the process fluid can cause significant damage, especially in the drive or in the bearings.

An important function of the barrier fluid is thus, in addition to the lubrication and cooling to protect the drive of the pump sufficiently against the ingress of process fluid. Very often, the barrier fluid is guided in a cooling circuit. The barrier fluid is introduced through an inlet in the drive, flows through the drive, for example through the gap between the rotor and the can, and the pump-side radial bearing of the shaft and is then discharged in the area between the drive and the pump through an outlet. From this outlet, the barrier fluid flows back to the inlet via a heat exchanger. In order to ensure the circulation of the barrier fluid in the cooling circuit, it is known to provide an auxiliary impeller on the side of the drive facing away from the pump, which is set in rotation by the shaft driven by the motor and thereby causes the circulation fluid to circulate in the cooling circuit.

Frequently, an injection device for refilling blocking fluid is additionally provided, with which additional blocking fluid either outside the housing in the cooling circuit or through a separate inlet opening directly into the drive can be introduced. This additional introduction of barrier fluid serves primarily to compensate for losses caused by the fact that a mostly minor flow rate of the barrier fluid is provided in the process fluid. When the barrier fluid flowing out of the drive flows along the shaft, the barrier fluid is not completely exhausted through the outlet, but a part flows or creeps along the shaft into the pump and mixes there with the process fluid. This process is intended and desirable, because by this flow of the barrier fluid into the pump, it can be reliably avoided that inversely flows from the pump process fluid along the shaft in the direction of the drive or penetrates into the drive. The barrier fluid thus blocks by the flow in the pump the reverse path for the process fluid from the pump into the drive.

In order to limit the flow of barrier fluid into the pump or to limit it to an appropriate value, a device for generating a controlled leakage flow is provided on the shaft in the vicinity of its entry into the pump. This device can be configured for example in the form of a mechanical seal, in which known direct physical contact between a non-rotatably connected to the shaft part and a stationary relative to the housing part, or in the form of a throttle, in which no direct physical contact between rotating and stationary parts exists. This non-contact throttle device is for example a throttle bushing.

Since, as already mentioned, such pump-drive units in many applications must work extremely reliably and usually maintenance-free over a long period in continuous operation, the reliability of the pump is of tremendous importance. In particular, aggressive or damaging process fluids must ensure that the drive is adequately protected against the process fluid. This should be the case even if there are disruptions in the system. A possible and critical accident, for example, a failure or failure of the injection device for the barrier fluid, because there is a risk that an excessive amount of process fluid enters the drive and damage it. If the cooling circuit for the barrier fluid is still working properly, the pump-drive unit may work in principle without the injection device, but only if no changes in the operating state of Pump drive unit or occur in the cooling system. A failure or a malfunction of the barrier fluid injection must therefore not necessarily cause a shutdown of the pump-drive unit. It is quite possible to continue operating the unit for at least a period of time, and to remedy the malfunction of the injection device during this period.

If, however, the failure of the injection system, for example, to a reduction in the volume of the barrier fluid in the drive or in the cooling circuit, the process fluid is sucked into the drive virtually and there leads to significant damage. In Ebullatorpumpen, where usually the drive is arranged below the pump, this effect can be supported by the gravity. A volume reduction of the barrier fluid may occur in addition to unwanted leaks, e.g. For example, the temperature of the cooling water commonly used in the heat exchanger to cool the barrier fluid may decrease, causing the barrier fluid to cool and thermally contract. Or if the rotational speed of the pump is reduced, this also leads to a volume reduction of the barrier fluid. Even if the pump-drive unit has to be switched off, this ultimately leads to a reduction in volume of the barrier fluid. Thus, there is the considerable risk that the drive is damaged by the process fluid or even irreparably destroyed.

This problem is addressed by the invention. It is therefore an object of the invention to provide a pump-drive unit for conveying a process fluid, in which it is ensured even in the event of a fault in the supply of barrier fluid that there is no damage to the drive by the process fluid. In particular, this pump-drive unit should also be used as Ebullatorpumpe.

The object of the invention solving this object is characterized by the features of the independent claim.

According to the invention, therefore, a pump-drive unit for conveying a process fluid is proposed, with a common housing, which a pump with an impeller for rotation about an axial direction and a drive for the pump encloses, with a shaft for driving the impeller, which connects the drive to the pump, and with a throttle, which extends around the shaft, and which is provided between the impeller and the drive, the housing having a pump inlet and a pump outlet for the process fluid, wherein an inlet for a barrier fluid is provided, through which the barrier fluid is introduced into the drive, and an outlet for the barrier fluid through which the barrier fluid can be discharged from the housing, and wherein a plurality of storage chambers for the barrier fluid is provided on the shaft in the region between the throttle and the drive, which storage chambers are arranged one behind the other with respect to the axial direction, wherein each two adjacent storage chambers are fluidly connected to each other.

Now comes to an operating condition, for example, by a disturbance in the supply for the barrier fluid, in which no longer sufficient volume of barrier fluid in the drive or in the housing is available to flow from the barrier fluid through the throttle in the pump to allow the process fluid along the shaft to exit the pump, passes through the restrictor and into the first of the storage chambers. Since this is still filled with the pure barrier fluid, it comes here to a mixing of the process fluid with the barrier fluid, whereby the process fluid is greatly diluted. This mixture of process fluid and barrier fluid then passes as contaminated barrier fluid in the next storage chamber, which is still filled with pure barrier fluid. In this storage chamber, the process fluid is then further diluted by the pure barrier fluid. In the last storage chamber, which is closest to the drive, the process fluid is then diluted the most. Even if then the process fluid contaminated barrier fluid should subsequently penetrate into the drive, so the process fluid is so heavily diluted that it does not lead to damage to the drive.

When such a disturbance occurs, in which there is no longer sufficient volume of barrier fluid available, there are two options. The first possibility is that the disorder is so serious that it can not be remedied in a short time. Then the pump drive unit needs be switched off, which is ensured by the inventive design that when switching off the pump - if anything - only a small amount of highly diluted process fluid in the form of contaminated barrier fluid can penetrate into the drive, but this does not lead to damage to the drive. Thus, a safe shutdown of the pump-drive unit is ensured, without causing the drive is damaged by penetrating process fluid.

The second possibility is that the disturbance can be remedied relatively quickly. In this case, the pump-drive unit does not have to be shut down. As described above, when the disturbance occurs, the process fluid is successively diluted in the storage chambers arranged one behind the other in the axial direction. If the fault is now remedied, then there is again a sufficient amount of pure barrier fluid available. This then pushes out the contaminated barrier fluid from the storage chambers towards the pump so that the contaminated barrier fluid from the storage chambers is flushed into the pump. This applies analogously to the same case also for the case that already a certain amount of process fluid contaminated barrier fluid has penetrated into the drive. This is then removed by the supply of pure barrier fluid from the drive, so that damage to the drive is effectively prevented by the process fluid.

Thus, in any event, it is ensured that upon occurrence of such a disturbance damage to the drive by the process fluid is prevented, either by a resumption of the supply of pure barrier fluid or by a controlled and safe shutdown of the pump-drive unit.

A particular advantage of the inventive design with the storage chambers is the fact that there is no need for a seal assembly on the shaft between the drive or the drive on the pump side provided radial bearing and the pump, in which there is a direct physical contact between a rotating part - So rotatably connected to the shaft part - and a stationary part with respect to the housing comes, so for example a mechanical seal. The throttle and the storage chambers function non-contact in the sense that they are the rotating shaft not touched. This is particularly advantageous in those embodiments in which the process fluid is under a very high pressure, for. B. at least 200 bar, and / or has a very high temperature, for. At least 400 ° C. In particular, in such applications, namely mechanical seals are problematic and less reliable, for example, because it comes with a decrease in the volume of the barrier fluid in the drive to form a back pressure, which rests on the mechanical seal. The contactless design according to the invention is characterized by the opposite by a higher reliability and a lower susceptibility to interference.

For manufacturing reasons, it is preferred if each storage chamber is designed as an annular space around the axial direction.

According to a preferred embodiment, in each case two adjacent storage chambers are flow-connected through a throttle gap, wherein the shaft forms a respective Bregrenzungsfläche of the throttle gap.

The appropriate number of storage chambers depends of course on the particular application or on the specific design of the pump-drive unit from, for example, the volume that is available in the drive for the barrier fluid, the size and performance of the pump or to promoting process fluid. In practice, it has proven useful if at least three and at most ten storage chambers are provided.

In a preferred embodiment, at least one of the storage chambers is provided in the housing, for example as an annular groove which extends around the shaft.

There are also such embodiments possible, in which at least one of the storage chambers is provided in the shaft, for example as an annular groove which extends over the circumference of the shaft.

For manufacturing reasons, it is particularly preferred if all storage chambers are provided in the housing.

In a preferred embodiment, the outlet and the inlet for the barrier fluid are connected by a conduit, so that a cooling circuit for the barrier fluid is formed, wherein the cooling circuit comprises a heat exchanger.

In order to enable the most compact and simple design, it is advantageous if the heat exchanger for the cooling circuit is mounted on the housing. The heat exchanger can be fastened to the housing, for example, by means of a flange connection or by screwing.

According to a preferred embodiment, an injection device is provided for refilling barrier fluid.

A suitable dimension of the storage chambers of course depends on the particular configuration of the pump-drive unit and in particular on the volume available for the barrier fluid and is therefore to be determined for the specific application. Preferably, the storage chambers have a total volume which is at least as large, and preferably twice as large, as the thermally induced volume change of the barrier fluid in the cooling circuit at a temperature decrease of the barrier fluid by a predetermined value. In the particular application, it is thus possible, for example, first of all to determine the volume which is provided for the blocking fluid in the entire cooling circuit, including the volume available in the drive. Furthermore, one estimates the temperature change, which can typically occur in the operating state in the barrier fluid in the cooling circuit. For the barrier fluid used in the application, it is now possible with the help of the thermal expansion coefficient to calculate the volume change of the barrier fluid, which is caused by such a temperature change. The total volume of all storage chambers is then chosen to be at least as large and preferably twice as large as the determined volume change of the barrier fluid.

For many applications, it is advantageous if the total volume of all storage chambers at least 0.5% and at most 4%, preferably at most 3%, of the volume available in the cooling circuit for the barrier fluid.

In a preferred embodiment, the housing is designed as a pressure housing, preferably for an operating pressure of at least 200 bar.

For many practical applications, it is advantageous if the pump-drive unit is designed for a process fluid having a temperature of more than 400 ° C.

The inventive design is particularly suitable for such a pump-drive unit, wherein the drive is arranged with respect to the vertical below the pump or is arranged with respect to the horizontal next to the pump. Related to the normal position of use of the pump-drive unit, this means that the pump is arranged in the common housing above or next to the drive.

A particularly important embodiment for practice is when the pump-drive unit is designed as an Ebullator pump for the circulation of a process fluid.

Further advantageous measures and embodiments of the invention will become apparent from the dependent claims.

Fig. 1:

ein teilweise schematische Schnittdarstellung eines Ausführungsbeispiels einer erfindungsgemässen Pumpen-Antrieb-Einheit,

Fig. 2:

eine vergrösserte Schnittdarstellung der Drossel und der Speicherkammern des Ausführungsbeispiels aus Fig. 1 an der Welle zwischen Antrieb und Pumpe,

Fig. 3:

wie Fig. 2, aber für eine erste Variante der Drosseleinrichtung,

Fig. 4:

wie Fig. 2, aber für eine zweite Variante der Drosseleinrichtung, und

Fig. 5:

ein Diagramm zur Veranschaulichung der Konzentration des Prozessfluids in den Speicherkammern beim Auftreten einer Störung.

In the following the invention will be explained in more detail by means of embodiments and with reference to the drawing. In the schematic drawing show, partly in section:

Fig. 1:

a partially schematic sectional view of an embodiment of an inventive pump-drive unit,

Fig. 2:

an enlarged sectional view of the throttle and the storage chambers of the embodiment Fig. 1 on the shaft between drive and pump,

3:

as Fig. 2 but for a first variant of the throttle device,

4:

as Fig. 2 but for a second variant of the throttle device, and

Fig. 5:

a diagram illustrating the concentration of the process fluid in the storage chambers in the event of a fault.

Fig. 1 shows in a partially schematic sectional view of an embodiment of an inventive pump-drive unit for conveying a process fluid, which is generally designated by the reference numeral 1. The pump drive unit 1 comprises a pump 2, which is designed as a centrifugal pump, and a drive 3, which is designed as an electric motor. The pump 2 and the drive 3 are arranged in a common housing 4, which encloses the drive 3 and the pump 2. The housing 4 comprises an upper housing part 41 and a lower housing part 42, which are sealingly connected to each other by not shown screwed connections or a flange connection.

In particular, the pump drive unit 1 in this embodiment is configured as an ebullating pump. As mentioned earlier, ebullator pumps are pump-drive units used for the fluidized bed or ebullated bed process in the hydrocarbon processing industry. These processes are used to clean heavy hydrocarbons, which remain, for example, in the oil refinery in the bottom of the separation columns, for example, to desulfurize and / or break up into lighter hydrocarbons, which are then used more economically as distillates. As an example of heavy hydrocarbons here is called heavy oil, which remains at the refinery of petroleum. In a known method, the starting material, ie the heavy hydrocarbons such. As heavy oil, heated, mixed with hydrogen and then as a process fluid in the fluidized bed or Siedebettreaktor (ebullated bed reactor). In the reactor, the purification or breaking up of the process fluid then takes place with the aid of catalysts which float in the reactor be kept to ensure intimate contact with the process fluid. To supply the reactor with the process fluid or for the circulation of the process fluid, an Ebullator pump is used, which is typically mounted directly to the reactor.

Since the process fluid is due to the process under a very high pressure of, for example, at least 200 bar and a very high temperature, for example, above 400 ° C, and the Ebullatorpumpe must be designed for such pressures and temperatures. In particular, in this case, the housing 4 of the designed as a pump-drive unit Ebullatorpumpe 1, which encloses the pump 2 and the drive 3, designed as a pressure housing that can safely withstand these high operating pressures, for example, 200 bar or more. In addition, the Ebullatorpumpe is also designed so that they can promote a hot process fluid, which has a temperature of more than 400 ° C, safely.

In the following, reference will therefore be made, with an exemplary character, to the application which is important for practice, that the pump-drive unit 1 is designed as such an ebullator pump. It is understood, however, that the invention is not limited to such embodiments or applications. The inventive pump-drive unit 1 can also be designed for other applications, for example as a submersible pump, which during operation in whole or in part in a liquid, eg. As water immersed. In particular, the invention is suitable for such pump-drive units, in which the drive 3 with respect to the vertical below the pump 2 is arranged (vertical pump), or in which the drive 3 with respect to the horizontal next to the pump 2 is arranged (horizontal pump). A representation of an embodiment as a horizontal pump corresponds to z. B. a representation that is characterized by rotation of the Fig. 1 by 90 ° results.

At the in Fig. 1 illustrated embodiment of the inventive pump-drive unit 1 as Ebullatorpumpe is the pump 2 with respect to the normal position of use, in Fig. 1 is shown, arranged above the drive 3. The pump 2 is designed as a centrifugal pump with an impeller 21 having a plurality of wings and in the operating state by a axial direction A rotates. The housing 4 has a pump inlet 22, which is arranged here above the impeller 21, and a pump outlet 23, which is arranged here laterally on the housing 4. The impeller 21 promotes the process fluid, so here the fluid with the heavy hydrocarbons, eg. As heavy oil, from the pump inlet 22 to the pump outlet 23, which is connected directly to the reactor.

For driving the impeller 21 of the drive 3 is provided, which is designed here in a conventional manner as an electric canned motor (canned motor). The drive 3 comprises an inner rotor 31 and an outer stator 32 surrounding the rotor 31. A gap tube 33 is provided between the rotor 31 and the stator 32 which hermetically seals the stator in a known manner with respect to the rotor 31. The rotor 31 is rotatably connected to a shaft 5 which extends in the axial direction A and on the other hand rotatably connected to the impeller 21 of the pump 2, so that the pump 2 is driven by the drive 3.

With respect to the axial direction A immediately above and immediately below the drive 3, a radial bearing 6 for the radial mounting of the shaft 5 is provided in each case. Below the lower radial bearing 6 as shown, a thrust bearing 7 is provided for the shaft 5. Furthermore, a circulation impeller 8 is provided for a barrier fluid at the bottom end of the shaft 5 as shown, which is also rotatably connected to the shaft 5 and which is designed as a radial impeller. Its function will be explained later. The circulation impeller 8 may also be provided between the pump 2 and the drive 3 on the shaft 5.

During operation of the pump 2, this promotes the process fluid from the pump inlet 22 to the pump outlet 23. In the case of heavy hydrocarbons such. As heavy oil as a process fluid but also in other process fluids, such as chemically aggressive substances or contaminated fluids, it is necessary to take measures that the process fluid can not or at least not penetrate in a harmful amount in the drive 3. Such penetration would be possible, for example, if the process fluid emerges from the pump 2 along the shaft 5 and subsequently penetrates into the drive 3 along the shaft 5. For this reason, a barrier fluid is provided, for example an oil, in particular a lubricating or cooling oil, a function of which is to prevent the penetration of process fluid into the drive 3. In addition, the barrier fluid also fulfills the function of dissipating heat as cooling fluid and lubricating the drive 3 as well as the radial bearings 6 and the thrust bearing 7 as lubricant. The heat to be dissipated by the barrier fluid comprises both the heat which is generated by the latter during operation of the drive 3 and heat which is transferred from the hot process fluid to the shaft 5 or to the housing 4. While the process pressure in the drive 3 and in the pump 2 is substantially the same, the operating temperature in the pump 2 is significantly higher than in the drive 3. While, for example, the impeller 21 assumes substantially the same temperature as the process fluid, so here, for example above 400 ° C, the temperature in the drive 3 is significantly lower, for example in the range of 60 ° C. Thus, the barrier fluid also has the function to dissipate the heat transferred from the hot impeller 21 to the shaft 5.

For the supply of the barrier fluid, both an inlet 43 for the barrier fluid is provided on the housing 4, through which the barrier fluid in the drive 3 can be introduced and an outlet 44 for the barrier fluid, through which the barrier fluid from the housing 4 can be discharged. Preferably - as in Fig. 1 illustrated, the outlet 44 via a line 91 to the inlet 43 fluidly connected, so that the barrier fluid is guided in a cooling circuit. This cooling circuit further comprises a heat exchanger 9, which is provided outside the housing 4, and in which the barrier fluid gives off its heat to a heat transfer medium, for example water.

The inlet 43 for the barrier fluid is provided according to the representation at the lower end of the housing 4, so that the barrier fluid flows through not only the drive 3, but also the two radial bearings 6 and the thrust bearing 7, whereby they are lubricated and cooled. As shown, above the upper radial bearing 6, the barrier fluid is then guided to the outlet 44 and passes via the line 91 to the heat exchanger 9, where the barrier fluid gives off heat. From the heat exchanger 9, the barrier fluid is then through the Line 91 led back to the inlet 43, whereby the cooling circuit closes.

The already mentioned circulation impeller 8, which is driven by the shaft 5, serves to circulate the barrier fluid through the cooling circuit. The inlet 43 is disposed opposite to the circulation impeller 8, so that the circulation impeller 8 sucks the barrier fluid in the axial direction A through the inlet 43. The funded by the circulation impeller 8 barrier fluid flows through the thrust bearing 7 and the lower radial bearing 6, is then introduced into the drive 3, flows through the gap between the rotor 31 and the can 33, exits the drive 3, flows through the upper radial bearing 6 and is then directed to outlet 44, from where the barrier fluid is circulated through line 91 and heat exchanger 9 back to inlet 44.

The circulation fluid circulating in the cooling circuit prevents the penetration of process fluid into the bearings 6, 7 and in particular into the drive 3, since the flowing barrier fluid shuts off the passage for the process fluid along the shaft 5 into the drive 3.

In order to increase the reliability of the pump-drive unit 1 even more and to compensate, for example, volume fluctuations of the barrier fluid in the cooling circuit, an injection device 92 is further provided for refilling or for feeding barrier fluid in the cooling circuit. The injection device 92, which is not shown in detail, comprises a source or reservoir for the barrier fluid and is connected to the cooling circuit via a check valve 93. It is possible - as in Fig. 1 shown - that the injection device 92 is connected to the outside of the housing 4 arranged part of the cooling circuit, so for example with the line 91, or on the housing 4, a separate inlet opening is provided, through which the barrier fluid from the injection device 92 can be introduced into the cooling circuit ,

During normal, ie, trouble-free operation of the pump drive unit 1, the injector device 92 is used to provide a desired and controlled leakage flow of the barrier fluid along the shaft 5 into the pump 2 balance. The emerging from the drive 3 and flowing through the upper radial bearing 6 barrier fluid is not completely discharged through the outlet 44. A portion of the barrier fluid generates a leakage flow along the shaft 5 in the pump 2 and mixes there with the process fluid, but this has no negative effects. By means of this leakage flow into the pump 2, it is effectively prevented that process fluid can flow out of the pump 2 along the shaft 5 in the opposite direction. The amount of barrier fluid necessary for this leakage flow is continuously supplied to the refrigeration cycle by the injection device 92, ie in normal operation, the injection device 92 replaces the amount of barrier fluid introduced into the process fluid by the leakage flow. Furthermore, the injection device 92 compensates for volume changes of the barrier fluid in the cooling circuit. Such volume changes may occur, for example, with changes in the speed of the pump 2, or with temperature changes or during startup or shutdown of the pump-drive unit. 1

The leakage current is usually not particularly strong and is for example in normal operation about 20 to 30 liters / hour

If there is now a malfunction in the injection device 92 or in the injection system for the barrier fluid, for example a failure of the injection device 92, so that the injection device 92 can supply no or insufficient barrier fluid in the cooling circuit, this does not inevitably lead to the risk that the drive 3 is damaged by penetrating the process fluid, because sufficient blocking fluid is still circulated in the cooling circuit in order to keep the process fluid away from the drive 3.

If, in such a disturbance of the injection device 92, in addition to a volume reduction of the barrier fluid still present in the cooling circuit, a state may arise in which insufficient volume of barrier fluid is available in the drive 3 or in the housing 4, respectively Flow from the process fluid along the shaft 5 from the pump 2 out in the direction of the drive 3 to prevent. Such a decrease in volume can have several causes. For example, the temperature of the heat carrier, such as cooling water, decrease, on which the barrier fluid emits heat in the heat exchanger 9, or the speed, ie, the rotational speed of the pump 2 decreases, or the pump drive unit 1 is turned off.

In order to protect the drive 3 in a sufficient manner against ingress of process fluid even in those conditions in which there is a reduction in volume of the barrier fluid in the cooling circuit, according to the invention on the shaft 5 in the region between the pump 2 and the drive 3 a Combination provided, which is generally designated by the reference numeral 10 and a throttle 13 and a plurality of storage chambers 11 includes. Fig. 2 shows an enlarged sectional view of this combination 10 of the embodiment Fig. 1 , The combination 10 includes a plurality, here five, of storage chambers 11 for the barrier fluid, which are arranged one behind the other with respect to the axial direction A, wherein two adjacent storage chambers 11 are fluidly connected. This flow connection is preferably as in Fig. 2 illustrated, designed as a throttle gap 12, wherein the shaft 5 each forms a boundary surface of the throttle gap 12. In Fig. 2 is denoted by the reference numeral 12 only for the two upper storage chambers 11 according to the illustration. Of course, the other storage chambers 11 are fluidly connected by such a throttle gap 12.

Between the storage chamber 11, which is closest to the pump 2 and the impeller 21, according to the representation of the uppermost storage chamber 11, and the impeller 21 of the pump 2, the throttle 13 is arranged, which is designed here as a throttle bushing 13, which is in extends in known manner around the shaft 5, without touching the shaft 5. The throttle bushing 13 is stationarily mounted with respect to the housing 4. The throttle bushing 13 is designed such that in the normal, ie trouble-free operation of the pump drive unit 1, it limits the volume flow of the barrier fluid into the pump 2 to a controlled leakage flow. It is understood that the design of the throttle as a throttle bushing 13 is to be understood only as an example. Suitable throttle 13 is any device known per se with which a controlled leakage flow of the barrier fluid can be generated in a contact-free manner. So can For example, the shaft 5 facing surface of the throttle 13 can be designed smooth or unstructured. But it is also possible that the throttle 13 is configured as a labyrinth throttle 13, which has in known manner on its surface facing the shaft a plurality of grooves and webs which form a comb-like profile, which is commonly referred to as a labyrinth.

The five storage chambers 11 (see Fig. 2 ) are each configured here as an annular space which extends around the shaft 5 around. In this case, all the storage chambers 11 are provided in the housing 4 or in a component which is stationary with respect to the housing and the shaft 5 surrounds. The storage chambers 11 can be produced, for example, by machining processes in the housing 4.

In the in Fig. 2 5, the total volume of all storage chambers 11 is five times the volume of a storage chamber 11. It is understood that it is not necessary that all storage chambers 11 have the same volume, it is quite possible to design the storage chambers 11 with different volumes.

In normal, trouble-free operation of the pump-drive unit 1, as already described, the barrier fluid is circulated in the cooling circuit by means of the circulation impeller 8, the return of the barrier fluid to the outlet 44, for example, as in FIG Fig. 1 shown schematically - out of that storage chamber 11 out, which is closest to the drive 3. But it is also possible to provide the return at another location, for example between the drive 3 and the storage chamber 11 closest to it.

However, the barrier fluid is not returned completely through the outlet 44, but there is a controlled leakage flow of the barrier fluid from the drive 3 through the five storage chambers 11 and the throttle bushing 13 into the pump 2 inside. This leakage current reliably prevents process fluid from flowing in the opposite direction from the pump 2 along the shaft 5 in the direction of the drive. The Volume of barrier fluid that is introduced by the controlled leakage flow in the pump 2 and thus in the process fluid is lost to the cooling circuit, but is replaced by the injection device 92 by new barrier fluid, which is introduced into the cooling circuit.

If, as already described, a disruption in the subsequent delivery of the barrier fluid occurs, for example a failure of the injection device 92, so that no or not enough blocking fluid can be replenished to the cooling circuit, and then to a state that leads to a decrease in volume of the barrier fluid leads in the cooling circuit, the inventive embodiment with the storage chambers 11 for the barrier fluid protects the drive 3 in a sufficient manner against ingress of the barrier fluid, as in the following with reference to Fig. 2 is explained.

A failure of the subsequent delivery of barrier fluid associated with a decrease in volume of the barrier fluid in the cooling circuit causes the process fluid can now escape from the pump 2 along the shaft 5, or depending on the circumstances in the direction of the drive 3 is sucked. This is in Fig. 2 indicated by the arrows provided with the reference symbol P. The process fluid then passes first into the first storage chamber 11, which is closest to the pump 2. This storage chamber 11 is still, like all other storage chambers 11 also filled with pure barrier fluid, which is stored there. As a result, mixing of the process fluid with the barrier fluid occurs in this first storage chamber 11, as a result of which the process fluid is greatly diluted. The process fluid is in Fig. 2 symbolically represented by the small dashes (without reference numeral) in the storage chambers 11. The already significantly diluted process fluid passes through the throttle gap 12 in the next storage chamber 11, which is initially completely filled with pure barrier fluid. In this storage chamber 11, the already diluted process fluid is further diluted by the barrier fluid before this further diluted mixture can penetrate via the next throttle gap 12 in the adjacent storage chamber 11. This process continues into the storage chamber 11 which is closest to the drive 3. In this last storage chamber 11 in front of the drive 3, the process fluid is diluted most. Only from this last storage chamber 11, the highly dilute process fluid like this may be the arrow labeled P1 in FIG Fig. 2 indicates pass through the radial bearing 6 in the drive 3.

As a result of this mixing with the pure barrier fluid, the process fluid in the last storage chamber 11 in front of the drive 3, which may possibly penetrate into the drive 3, is already so severely diluted that for the time being it can cause no damage to the drive 3.

In order to effect the best possible mixing of the process fluid with the barrier fluid in the storage chambers 11, it may be advantageous to design the flow path for the process fluid by the combination 10 with further measures such that turbulence occurs in order to mix the process fluid promote the located in the storage chambers 11 barrier fluid. In the embodiment according to Fig. 2 For this reason, a plurality of annular grooves 111 are provided in the shaft 5, each of which is arranged opposite one of the storage chambers 11.

Now, if the fault is corrected when refilling the barrier fluid in the cooling circuit, so for example, the injection device 92 is working properly again, so by the newly supplied barrier fluid contaminated with the process fluid barrier fluid from both the drive 3 (if it has penetrated up to there) as also successively pressed out of the storage chambers 11 and conveyed into the pump 2. After this flushing of the drive 3 and the storage chambers 11 then the drive 3 and the storage chambers 11 are again filled with pure barrier fluid, so that the normal operation can be continued.

Of course, effective protection of the drive depends on the duration of the disturbance in the subsequent delivery of barrier fluid into the refrigeration cycle. Should it take too long until this fault is corrected, or, for example, an undesired leakage in the cooling circuit caused by damaged lines or leaking joints, it still allows the inventive design that the pump-drive unit can be switched off without the There is danger that at Shutdown Process fluid can penetrate into the drive in an amount that is harmful to the drive 3.

Fig. 5 illustrates the effect of the inventive design of the combination 10 with the storage chambers 11 in the event of a fault. In the concrete example, that in Fig. 5 is shown, the fault is that the injection device fails, so that no new barrier fluid can be introduced into the cooling circuit. In addition, it comes in the cooling circuit to a cooling of the barrier fluid to 10K, for example, by reducing the speed of the drive 3 and / or by a change in temperature in the heat transfer medium, eg. As cooling water, the heat exchanger 9. The five storage chambers 11 (see Fig. 2 ) have a total volume, which is about 1.3% of the volume of the cooling circuit, wherein the volume of the cooling circuit is composed of the volume that is the barrier fluid in the drive 3 available, as well as the volumes in the heat exchanger 9, the line 91 and all connections between the inlet 43 and the outlet 44. As barrier fluid, an oil is used, which has a volume-related thermal expansion coefficient of 0.7 · 10 ^-3 / K.

The diagram in Fig. 5 shows the time evolution of the relative volume VP of the process fluid for the five storage chambers 11 (see Fig. 2 ). On the horizontal axis, the time T is plotted and on the vertical axis, the relative volume VP of the process fluid in one of the storage chambers 11. The curve K1 shows the relative volume VP for the first storage chamber 11, which is the storage chamber 11, that of the pump second or the impeller 21 is closest. In Fig. 2 The curves K2, K3, K4, K5 show in an analogous manner the relative volume of the process fluid in the adjacent storage chambers 11, wherein the numbering of the storage chambers 11 of their in Fig. 2 corresponds to the order shown. Ie. the curve K2 indicates the relative volume VP of the process fluid in the second storage chamber 11 located immediately adjacent to the first storage chamber 11, etc. Accordingly, the curve K5 indicates the relative volume VP of the process fluid in the storage chamber 11 which is closest is located on the drive 3.

On the time axis t1 indicates the time at which the process fluid begins to enter the first storage chamber 11 upon the occurrence of the above-described disturbance, i. just before the time t1 just all five storage chambers 11 are filled with pure barrier fluid. From time t1, the process fluid enters the first storage chamber 11 at a constant flow rate. This flow rate is approximately such that per time interval t2-t1 an amount of process fluid enters the first storage chamber 11, which corresponds to approximately one quarter of the volume of the first storage chamber 11.

The diagram in Fig. 5 clearly illustrates the increasing dilution effect from storage chamber to storage chamber resulting from the mixing of the process fluid with the barrier fluid. At a time t10, according to the curve K1, the relative volume fraction of the process fluid in the first storage chamber 11 has already risen to more than 90%, while according to the curve K5 the relative volume fraction of the process fluid in the last storage chamber 11 is only about a quarter, that is about 25% lies.

This ensures that over a longer period of time, if at all, only highly diluted process fluid can penetrate into the drive 3, which usually does not lead to damage to the drive 3.

A particular advantage of the inventive design is that between the drive 3 and the upper radial bearing 6 and the pump 2 no seal assembly is necessary, which is based on a direct physical contact between rotating and stationary parts. In particular, so here can be dispensed with mechanical seals, which have proven especially at high temperatures and / or high process pressures as problematic and prone to failure.

The following are based on the Fig. 3 and Fig. 4 two variants for the design of the storage chambers 11 described. It is only on the differences to the in Fig. 2 illustrated embodiment received. All previous explanations apply mutatis mutandis to the same way for these two variants.

At the first in Fig. 3 a total of four storage chambers 11 are arranged one behind the other with respect to the axial direction, each of which is designed as an annular space about the axial direction A. All storage chambers 11 are provided in this embodiment in the shaft 5.

At the second in Fig. 4 a total of six storage chambers 11 are arranged one behind the other with respect to the axial direction, each of which is designed as an annular space about the axial direction A. In this embodiment, the storage chambers 11 are provided alternately in the housing 4 or in a part which is stationary relative to the housing and in the shaft 5. The storage chambers 11 provided in the housing 4 have a different volume, in this case a larger volume than that provided in the shaft 5.

The in the Fig. 2-4 illustrated embodiments of the combination 10 with the throttle 13 and the storage chambers 11 are of course only to be understood as an example. Here are many modifications possible, of which only a few are mentioned below.

The designed as an annular space storage chambers 11 in the shaft 5 or in the housing 4 are in the Fig. 2-4 each shown with a rectangular cross-section in a section along the axial direction A. Of course, this cross section may have other shapes, for example, the cross section may be U-shaped or V-shaped.

Also, the storage chambers 11 may be configured as sector-shaped recesses in the housing 4 and / or in the shaft, i. the storage chambers 11 do not have to extend over the entire circumference around the shaft 5 around.

Also, the volumes of the individual storage chambers 11 may be different (see, eg Fig. 3 ), Also, the volumes of those storage chambers 11 which are arranged in the housing 4, or those storage chambers 11 which are arranged in the shaft.

A suitable choice of the number of storage chambers 11 depends on the particular application. For very many embodiments, it is advantageous if at least three storage chambers 11 and at most ten storage chambers 11 are provided.

Also, the total volume of all storage chambers 11 can be adapted to the particular application. As already mentioned, it is possible to determine an advantageous overall volume of the storage chambers 11 on the basis of the volume reduction of the barrier fluid in the cooling circuit to be expected during operation or in the event of a fault. For very many applications, it has proved to be advantageous if the total volume of all storage chambers 11 is at least 0.5% and at most 4%, preferably at most 3% and especially at most 2% of the volume available in the cooling circuit for the barrier fluid.

Claims (15)

Pump-drive unit for conveying a process fluid with a common housing (4), which has a pump (2) with an impeller (21) for rotation about an axial direction (A) and a drive (3) for the pump (2) comprising a shaft (5) for driving the impeller (21) which connects the drive (3) to the pump (2) and a throttle (13) which extends around the shaft (5), and which is provided between the impeller (21) and the drive (3), the housing (4) having a pump inlet (22) and a process fluid pump outlet (23), wherein a barrier fluid inlet (43) is provided, by which the barrier fluid can be introduced into the drive (3), and an outlet (44) for the barrier fluid, through which the barrier fluid from the housing (4) can be discharged, characterized in that on the shaft (5) in the region between the Throttle (13) and the drive (3) is provided a plurality of storage chambers (11) for the barrier fluid is t, which storage chambers (11) with respect to the axial direction (A) are arranged one behind the other, wherein each two adjacent storage chambers (11) are fluidly connected to each other. Pump-drive unit according to claim 1, wherein each storage chamber (11) is designed as an annular space around the axial direction (A). Pump-drive unit according to one of the preceding claims, wherein each two adjacent storage chambers (11) are flow-connected through a throttle gap (12), wherein the shaft (5) each forms a Bregrenzungsfläche the throttle gap (12). Pump-drive unit according to one of the preceding claims with at least three and at most ten storage chambers (11). Pump-drive unit according to one of the preceding claims, wherein at least one of the storage chambers (11) in the housing (4) is provided. Pump-drive unit according to one of the preceding claims, wherein at least one of the storage chambers (11) is provided in the shaft (5). Pump-drive unit according to one of the preceding claims, wherein all storage chambers (11) are provided in the housing (4). A pump-drive unit as claimed in any one of the preceding claims, wherein the outlet (44) and the inlet (43) for the barrier fluid are interconnected by a conduit (91) such that a cooling circuit is formed for the barrier fluid, the cooling circuit comprising Heat exchanger (9) comprises. Pump-drive unit according to one of the preceding claims, in which an injection device (92) is provided for refilling barrier fluid. Pump-drive unit according to claim 8 or 9, wherein the storage chambers (11) have a total volume which is at least as large, and preferably twice as large, as the thermally induced volume change of the barrier fluid in the cooling circuit at a temperature decrease of the barrier fluid by one predefinable value. Pump-drive unit according to one of claims 8-10, wherein the total volume of all storage chambers (11) is at least 0.5% and at most 4%, preferably at most 3%, of the volume available in the cooling circuit for the barrier fluid. Pump-drive unit according to one of the preceding claims, wherein the housing (4) is designed as a pressure housing, preferably for an operating pressure of at least 200 bar. Pump-drive unit according to one of the preceding claims, designed for a process fluid having a temperature of more than 400 ° C. Pump-drive unit according to one of the preceding claims, wherein the drive (3) with respect to the vertical below the pump (2) is arranged or with respect to the horizontal next to the pump (2) is arranged. Pump-drive unit configured as Ebullatorpumpe for the circulation of a process fluid.

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