Device for controlling a hydraulic machine

Abstract

Device for controlling a hydraulic machine in a hydropower plant with a guide apparatus and a device for performing an emergency shutdown, characterized by low energy consumption and high efficiency while ensuring all operational and safety-related requirements of a hydraulic machine and suitable for continuous control operation without deadband.

Description

[0001] The invention relates to a device for controlling a hydraulic machine in a hydroelectric power plant with a guide vane, in particular a device for controlling a turbine or a pump turbine with a Francis type impeller.

[0002] A generic device is disclosed in DE 10 2017 106 693 B3. The device disclosed therein is characterized by high energy efficiency, good environmental compatibility, ease of maintenance, and low acquisition and operating costs. Furthermore, the disclosed device is suitable for controlling many different types of hydraulic machines. Thus, both the stator blades and the impeller blades of hydraulic machines can be controlled. Furthermore, double-acting cylinders or differential cylinders can be actuated. The disclosed device is particularly efficient when controlled via a so-called deadband, since then no control movements are required over longer periods.

[0003] With the decentralization of energy generation toward renewable energy sources such as wind turbines and solar power plants, hydroelectric power plants will have to make a greater contribution to frequency control (also known as primary control) of the grids in the future. In most cases, the respective grid codes of the federal states still permit a certain deadband (range in which no reaction to setpoint changes takes place) even in frequency control. This means that the control device does not need to be moved within the frequency deadband, and thus the double pump, the device known from DE 10 2017 106 693 B3, is also inactive within the frequency deadband. Due to the ever-increasing grid fluctuations of renewable energy generators, this deadband will have to be set to zero more and more often for hydroelectric power plants in the future.This direct integration into the frequency control system means continuous control of the diffuser with a very slow adjustment movement. In the device known from DE 10 2017 106 693 B3, this results in continuous control operation of the drive and the associated double pump at low speeds, thus increasing the risk of increased pump wear.

[0004] The object of the invention is to optimize the device known from the prior art for use in controlling the guide vane of a hydraulic machine in a hydropower plant, wherein the device should be suitable for continuous control operation without dead band.

[0005] The object is achieved according to the invention by an embodiment according to the independent claim. Further advantageous embodiments of the present invention can be found in the subclaims.

[0006] The invention is explained below with reference to the figures. The figures show in detail: Fig. 1: Device according to the invention Fig. 2: Arrangement of two differential cylinders, which together act as a synchronous cylinder

[0007] In the presentation of the Fig. Figure 1 shows a schematic diagram of a device according to the invention for controlling a hydraulic machine. The device comprises a collection and equalization tank, designated 1, a pump arrangement, designated 2, a variable-speed pump drive, designated 3, an accumulator, designated 5, a hydraulic cylinder, designated 6, an emergency shut-off valve, designated 71, an emergency shut-off solenoid valve, designated 72, two pilot-operated check valves, designated 81 and 82, two pilot control valves, designated 91 and 92, three throttles, designated 10, 11, and 12, an optional solenoid valve, designated 20, two optional pressure relief valves, designated 30 and 31, and two optional connections, designated 40 and 50.The arrow below the hydraulic cylinder 6 indicates its closing direction.

[0008] The hydraulic cylinder 6 is a hydraulic cylinder that operates the guide vanes of a hydraulic machine. For this purpose, the hydraulic cylinder 6 usually engages the guide vane ring. Fig. The hydraulic cylinder 6 shown in Figure 1 is designed as a synchronous cylinder. More than one hydraulic cylinder can also be provided to actuate the guide vanes. Fig. 2 shows an example of an arrangement of two hydraulic cylinders, each hydraulic cylinder being designed as a differential cylinder, but connected in such a way that they act together as a synchronous cylinder.

[0009] The pump assembly 2 comprises exactly one pump with a reversible pumping direction. The pump of the pump assembly 2 is designed as a 4Q piston pump, optionally as a flushed 4Q piston pump (see below). In this case, one connection of the pump is connected to a control line of the hydraulic cylinder, so that in one direction of rotation of the shaft, the pump delivers hydraulic fluid into a first chamber of the hydraulic cylinder 6 and simultaneously draws hydraulic fluid from the other chamber of the hydraulic cylinder 6. In the other direction of rotation of the shaft, the situation is reversed. Fig. 1 the right connection of the pump (via the pilot-operated check valve 82) is connected to the closing side of the hydraulic cylinder 6 and the left connection of the pump (via the pilot-operated check valve 81) is connected to the opening side of the hydraulic cylinder 6.

[0010] The shaft of the pump assembly 2 is driven by the variable-speed pump drive 3, which can be operated in both directions. The pump drive 3 typically comprises an electric servomotor electrically powered by a frequency converter. Due to its design, the 4Q piston pump can generate maximum pressure indefinitely at very low speeds without an increased risk of wear, as is necessary for the continuous control of the distributor of the hydraulic machine, which participates in the frequency control of the transmission grid.

[0011] In this operating mode, i.e. when the 4Q piston pump is in continuous operation, the 4Q piston pump may need to be cooled. Whether such a pump needs to be cooled depends on the technical data of the hydropower plant in question. If a pump with cooling must be used, such a 4Q piston pump has a designated so-called flushing oil connection. Through this connection, the hydraulic oil of the collecting tank (1) can be used to flush the 4Q piston pump and thus to transport heat during continuous operation. To generate the required volume flow, a device according to the invention comprises a further pump arrangement, which in Fig. 1 is designated 8. To distinguish between pump arrangements 2 and 8, pump arrangement 2 is referred to as the “first pump arrangement” and pump arrangement 8 as the “second pump arrangement”.

[0012] The second pump arrangement 8 serves not only to flush the 4Q piston pump but also to charge the accumulator 5. The suction side of the second pump arrangement 8 is connected to the collection and equalization tank 1 and its pressure side to the accumulator 5. The line from the pressure side to the accumulator 5 is referred to below as the “accumulator charging line”. A check valve, designated 86, is arranged in the accumulator charging line. The check valve is arranged such that it prevents flow from the accumulator to the second pump arrangement. Between the second pump arrangement 8 and the check valve 86, a line branches off from the accumulator charging line, which is referred to hereinafter as the “flushing line” and is connected to the flushing connection of the first pump arrangement 2. A changeover valve, designated 85, is arranged in the flushing line.A throttle, designated 88, and an optional flow sensor, designated 89, are located in the flushing line. To better distinguish it from the other throttles, throttle 88 is referred to below as the "flushing throttle" and is preferably adjustable.

[0013] Optionally, another line can branch off from the flushing line between the changeover valve 85 and the flushing throttle 88, which is referred to below as the "return line" and which is connected to the collection and equalization tank 1. A pre-loaded check valve is arranged in the optional return line, which is marked 87. The pre-loaded check valve is arranged so that after overcoming a predefined force, hydraulic fluid can flow through the return line into the collection and equalization tank 1. When the changeover valve 85 is open, the second pump arrangement 8 can supply the first pump arrangement 2 with flushing oil in pressure-free circulation. The flushing oil volume flow is defined by the flushing throttle 88. Optionally, the flushing oil volume flow can be regulated as needed using an adjustable throttle 88 and the optional flow sensor 89.

[0014] The optional return line allows a portion of the volume flow to flow back to the collection and equalization tank 1 via the spring-loaded check valve 87. This allows for more flexible design of the elements used to flush the first pump assembly 2 and charge the accumulator 5. For example, the second pump 8 can be designed larger than would be necessary for pure flushing, allowing the accumulator 5 to be charged more quickly.

[0015] To charge accumulator 5, the switching valve 85 is closed. Both operating modes are described in more detail below. The position of the switching valve 85 is electrically controlled.

[0016] Optionally, a filter can be installed in the flushing line, which Fig. 1, designated 83, and a heat exchanger, designated 84, are arranged. The filter 83 serves to clean the hydraulic fluid, and the heat exchanger 84 can be used to cool or heat the hydraulic fluid. The elements 83 and 84 are arranged between the switching valve 85 and the flushing throttle 88.

[0017] The pilot-operated check valves 81 and 82, which are arranged in the connecting lines between the hydraulic cylinder 6 and the first pump assembly 2 in such a way that they prevent movement of the piston of the hydraulic cylinder when not unlocked, are each connected to one of the pilot valves 91, 92. These are each connected (via the valves 20 and 72) to the accumulator 5. Opening a pilot valve 91, 92 thus unlocks the corresponding check valve 81, 82. The opening of the pilot valves 91, 92 is caused by the (electrical) controller of the hydraulic machine by energizing them. Each of the pilot valves 91, 92 can be energized separately.

[0018] The accumulator 5 is connected to the closing side of the hydraulic cylinder 6. The emergency shut-off valve 71 is connected to the opening side of the hydraulic cylinder 6 and the collecting and equalizing tank 1 in such a way that a volume flow between the opening side of the hydraulic cylinder 6 and the collecting and equalizing tank 1 is only possible when the emergency shut-off valve 71 is open. The state of the emergency shut-off valve 71 is controlled via the emergency shut-off solenoid valve 72, which is located in a hydraulic line between the emergency shut-off valve 71 and the accumulator 5. The emergency shut-off solenoid valve 72 is also located in the lines between the pilot valves 91, 92 and the accumulator 5. In a preferred embodiment, the spring-loaded emergency shut-off solenoid valve 72 is always permanently energized during operation, whereby the emergency shut-off valve 71 is closed and the pilot valves 91, 92 are supplied with oil pressure by the accumulator 5 (i.e.the check valves 81, 82 can be unlocked in this state by the pilot valves 91, 92).

[0019] The throttle 10, also called the "basic throttle," is located in the line between the opening side of the hydraulic cylinder 8 and the check valve 81, but before the branch in this line to the emergency shut-off valve 71, i.e., in the immediate vicinity of the hydraulic cylinder 6. The throttle 11 is located in the line connecting the accumulator 5 to the rest of the device. The throttle 12 is located in the line between the emergency shut-off valve 71 and the collection and equalization tank 1. Both throttles 11 and 12 are optional (see the explanations on the emergency shut-off function).

[0020] Optionally, the device can also include additional emergency shut-off control valves (e.g., an overspeed valve, etc.). These can be connected via port 50, which is located in the same hydraulic line as the emergency shut-off solenoid valve 72.

[0021] Optionally, additional consumers can be connected to the accumulator 5 via connection 40. Connection 40 is located in the hydraulic line that connects the accumulator 5 to the rest of the device.

[0022] The Fig. The device according to the invention shown in Figure 1 comprises a single hydraulic cylinder 6, which is designed as a synchronous cylinder. As already mentioned, a device according to the invention can also comprise more than one hydraulic cylinder 6. Thus, the device according to the invention can comprise any number of hydraulic cylinders designed as synchronous cylinders. In this case, the hydraulic cylinders are hydraulically connected in parallel. The parallel connection then replaces the Fig. 1. In this case, a common basic throttle 10 and / or a separate basic throttle can be provided for each hydraulic cylinder. Hydraulic cylinders are also known in which a rod is arranged on only one side, but which nevertheless act as synchronous cylinders, i.e. have effective areas of the same size on both hydraulic sides. This type of hydraulic cylinder is usually referred to as a synchronous cylinder. In a device according to the invention, any desired number of synchronous cylinders can be used, which are arranged as described for the synchronous cylinders. In a device according to the invention, an even number of differential cylinders can also be used. In this case, two differential cylinders are connected hydraulically "in reverse" in parallel, so that they act together like a synchronous cylinder. Fig.Figure 2 shows such an arrangement of two differential cylinders. If more than two differential cylinders are used, the cylinder pairs are again hydraulically connected in parallel. All described hydraulic cylinder configurations are understood in this document to be "at least one hydraulic cylinder acting as a double-acting cylinder."

[0023] The following describes in more detail the modes of operation of the device according to the invention in the individual operating states of the hydraulic machine, and explains the advantages of the device. As an initial state, it is assumed that the accumulator 5, which is directly connected to the closing side of the hydraulic cylinder 6, is charged with a defined pressure and the hydraulic cylinder 6 is in any intermediate position. Normal operation of the hydraulic machine:

[0024] A distinction is made here between conventional control operation with an active deadband and control operation for frequency control with an inactive deadband. Conventional regular operation:

[0025] As long as the position of hydraulic cylinder 6 is to be maintained, the pilot solenoid valves 91, 92 controlled by the hydraulic machine's controller are de-energized. As a result, the pilot-operated check valves 81, 82 in the control lines to the opening and closing sides of hydraulic cylinder 6 are also closed, and cylinder 6 is held in its position without leakage. In this state, variable-speed drive 3 is switched off, preventing any energy loss (heat) from entering the system. If the device is used exclusively in conventional control mode, cooling of the hydraulic fluid is not required, which offers the advantage of significantly improved energy efficiency. In any case, in this state (holding the position), the second pump arrangement 8 can also be deactivated.

[0026] If a control action is now necessary (e.g., a setpoint change or the control deviation exceeds a certain value (dead band)), the pilot valves 91 and 92 are energized via the controller, causing the pilot-operated check valves to open. The hydraulic cylinder can now be positioned directly via the variable-speed pump drive 3.

[0027] The oil volume and thus the pressure in accumulator 5 remains nearly constant, so that the energy for an emergency shutdown is available over a long period of time, and charging of accumulator 5 does not need to occur very frequently. Accumulator 5 slowly empties when check valve 82 on the accumulator side is opened. This emptying is caused by the internal pump leakage of the piston pump. In addition, the control oil required for pilot valves 91 and 92 is drawn from accumulator 5, but this represents only a very small amount.

[0028] After reaching the desired position, the pilot valves 91, 92 are de-energized, whereby the cylinder 6 can again be held in its position without applying energy.

[0029] Since such a control process takes place very quickly in conventional control operation and sufficient time elapses between the individual control processes, flushing of the 4Q piston pump during such a control process can usually be dispensed with. Control operation for frequency control:

[0030] This mode of operation is characterized by the fact that a control process as just described is constantly taking place. The 4Q piston pump of the first pump assembly 2 must be continuously flushed by the second pump assembly 8. Emergency closure:

[0031] In order to ensure safe shutdown of the hydraulic machine in the event of a fault, an emergency shutdown function is preferably implemented, which allows the system to be shut down without a power supply (or in the event of a defect in the variable-speed drive 3). In the event of an emergency shutdown, the emergency shutdown solenoid valve 72, which is permanently energized during operation, is de-energized, whereupon the emergency shutdown valve 71 opens. This transforms the closed hydraulic control circuit into an open circuit. The accumulator 5 is connected to the closing side of the hydraulic cylinder 6, with the opening side now being diverted into the collection and equalization tank 1. At the same time, the pressure to the pilot valves 91, 92 is relieved, so that the pilot-operated check valves 81, 82 close. This reliably prevents, for example,due to a defect or leakage in the first pump arrangement 2, the storage volume could be mistakenly emptied and would therefore no longer be available for closing.

[0032] In this open circuit, accumulator 5 supplies a defined volume within defined pressure limits. Therefore, a defined closing time can be reliably set using the basic throttle 10. Safety can be further increased with an optional additional throttle 11 or 12 connected in series. If two additional throttles 11 and 12 connected in series are actually used, this results in greater flexibility and greater robustness against, for example, a line break in the line between the basic throttle 10 and the quick-closing valve 71, since the additional throttling effect is distributed across two throttles, only one of which (12) fails due to the line break.

[0033] When the hydraulic cylinder 6 is moved, the basic throttle 10 creates a back pressure against which the first pump arrangement 2 acts and which must therefore be kept within certain limits (nominal pressures of the lines and components to be maintained, power of the pump drive 3, etc.). This requires an individual design of the individual throttles 10, 11, 12. The focus must be on always realising the greatest possible proportion of the overall throttling effect and thus of the closing time via the basic throttle 10. One of the reasons for this is that the arrangement of the basic throttle 10 directly in the opening side of at least one hydraulic cylinder 6 ensures that the closing time is limited, even in the event of a line break on the opening control side (i.e. the line between the basic throttle 10 and the pump arrangement 2).

[0034] To protect the device against excessive pressure, optional pressure relief valves 30, 31 can be installed on the opening and closing sides of at least one hydraulic cylinder 6. It is clear that the pressure relief valve 31 can also be integrated into the accumulator 5. Storage loading function:

[0035] The accumulator charging function serves to replenish the hydraulic fluid removed from the accumulator 5 due to the internal pump leakage of the first pump arrangement 2 into the accumulator 5 and to maintain the accumulator pressure for the emergency closure function.

[0036] Accumulator 5 is monitored for its fill level and system pressure using appropriate level and pressure sensors. During operation, the hydraulic fluid volume and pressure in accumulator 5 are maintained within a defined pressure hysteresis, regardless of the position of hydraulic cylinder 6.

[0037] If the device according to the invention is used for frequency control, the second pump arrangement 8 is used most of the time to flush the first pump arrangement 2 if cooling thereof is necessary. In this case, the switching valve 85 is open. If the accumulator pressure drops too far, the switching valve 85 is closed, thereby interrupting the flushing process. Instead, the second pump arrangement 8 pumps hydraulic fluid into the accumulator 5 until the desired pressure is reached. If the second pump arrangement 8 is deactivated (e.g., during conventional control operation), it is activated to charge the accumulator.

[0038] Flushing the 4Q piston pump can be omitted during the short storage charging process without endangering the 4Q piston pump due to overheating. Once the charging process is completed, the previously active function of the second pump arrangement 8 is resumed.

[0039] The accumulator charging function is active during normal operation and when the hydraulic machine is at a standstill. This ensures that the appropriate safety is always provided in the event of an emergency shutdown, and that the accumulator is available as quickly as possible when the hydraulic machine is started up. Optional quick close function:

[0040] Normally, the first pump arrangement 2 is designed with regard to the size, speed and power of the pump so that the opening and closing times of the hydraulic cylinder 6 required for the respective application can be achieved via the pump drive 3 alone.

[0041] If, for example, large hydraulic cylinder volumes are available and, in contrast to the closing times, the opening times may be significantly longer, in order to keep the dimensions of the first pump arrangement 2 and the pump drive 3 as small as possible (space conditions, spare parts costs, etc.), these could be designed so that the hydraulic cylinder 6 can only be moved with the minimum opening time.

[0042] In order to achieve a faster closing time (e.g. in the case of a hydropower regulator during load shedding), the quick-closing solenoid valve 20 is optionally provided, which is located in the same hydraulic line as the emergency closing solenoid valve 72. By switching this valve 20, the accumulator volume can now be used to close. The quick-closing solenoid valve 20 is thereby energized, whereby the emergency closing valve 71 opens. At the same time, the pressure supply to the pilot valves 91 and 92 hydraulically separates, so that the pilot-operated check valves 81 and 82 in the control lines also close. The first pump arrangement 2 can now be controlled towards closing with maximum delivery during this process. With the support of the first pump arrangement 2, the oil volume that is withdrawn from the accumulator 5 is minimized. This has, among other things,the advantages that the accumulator 5 is emptied less and the closing time, which is defined via the basic throttle 10 directly on the hydraulic cylinder 6, can be set more precisely due to the smaller span between the initial and final pressure in the accumulator 5.

[0043] For example, to enable a water turbine to resynchronize after a load shedding, the quick-closing valve 20 is de-energized when a defined opening is reached. At the same time, the "fine control" is transferred back to the variable-speed pump drive 3, and the machine can be resynchronized.

[0044] In its current state, due to the closing process and the fact that the full volume could not be provided by the first pump assembly 2, the accumulator has been emptied by an amount less than the oil volume required to reach the corresponding hydraulic cylinder position. The pressure and oil volume in accumulator 5 are still high enough to allow any necessary emergency closure. Nevertheless, in this situation, accumulator 5 should be refilled as quickly as possible. This can easily be accomplished by the second pump assembly 8, as described above. Heating function:

[0045] If the oil temperature falls below a defined value, control via the first pump assembly 2 is initiated by opening the pilot-operated check valves 81 and 82. This leads to a slow discharge of the accumulator 5, initiating periodic accumulator charging processes. During accumulator charging, heat is generated that can be used to heat the system. Alternatively, the heat loss from the second pump assembly 8 in the unpressurized circulation or an optional heat exchanger 84 can be used to heat the system. List of reference symbols 1 collection and compensation tank 2 First pump arrangement 3 Variable speed pump drive 5 storage 6 hydraulic cylinders 8 Second pump arrangement 10 Thrush - “Basic Thrush” 11 Throttle 12 Throttle 20 Quick-closing solenoid valve 30 Pressure relief valve 31 Pressure relief valve 40 connection 50 connection 71 Emergency shut-off valve 72 Emergency closing solenoid valve 81 Pilot operated check valve 82 Pilot operated check valve 83 filters 84 heat exchangers 85 changeover valve 86 Check valve 87 Preloaded check valve 88 Throttle - “flushing throttle” 89 Flow sensor 91 Pilot valve 92 pilot valve

Claims

[1] A device for controlling a hydraulic machine with a distributor, comprising a first pump arrangement (2), a variable-speed pump drive (3), an accumulator (5), at least one hydraulic cylinder (6) which acts as a synchronous cylinder and actuates the distributor, an emergency shut-off valve (71), two releasable check valves (81, 82), and two pilot valves (91, 92) for releasably releasing the check valves (81, 82), and wherein the device further comprises a collecting and compensating reservoir (1), an emergency shut-off solenoid valve (72), and at least one throttle (10), and wherein a first connection of the first pump arrangement (2) is connected to the opening side of the hydraulic cylinder (6), and a second connection of the first pump arrangement (2) is connected to the closing side of the hydraulic cylinder (6), and wherein the collecting and compensating reservoir (1) is connected to the opening side, and the accumulator (5) is connected to the closing side of the hydraulic cylinder (6),and the emergency shut-off valve (71) is arranged in the line between the hydraulic cylinder (6) and the collecting and compensating tank (1), and a respective releasable check valve (81, 82) is located in one of the lines from the first pump arrangement (2) to the hydraulic cylinder (6) and is oriented such that hydraulic fluid can pass through in the direction of the hydraulic cylinder (6) in any state of the check valves (81, 82), and the device further comprises lines which connect the accumulator (5) to the two releasable check valves (81, 82) and the emergency shut-off valve (71) in order to be able to release the releasable check valves (81, 82) and close the emergency shut-off valve (71), wherein these lines form a single line at least over a section, in which section the emergency shut-off solenoid valve (72) is arranged such that it is continuous during operation of the hydraulic machine,and wherein the pilot valves (91, 92) are each arranged in the separately extending sections of the lines between the accumulator (5) and the releasable check valves (81, 82) and are designed to be electrically controllable, and wherein the at least one throttle (10) is located in the line to the opening side of the hydraulic cylinder (6) in order to be flowed through by hydraulic fluid during each movement of the hydraulic cylinder (6), , characterized byin that the first pump arrangement (2) comprises a pump which is designed as a 4Q piston pump and is connected to the pump drive (3) in such a way that the latter can drive the pump, and wherein the device comprises a second pump arrangement (8) which is connected with a suction side to the collecting and equalizing tank (1) and with a pressure side via a storage charging line to the accumulator (5), and wherein the device comprises a check valve (86) which is arranged in the storage charging line in such a way that it can prevent a flow from the accumulator (5) to the second pump arrangement (8). [2] Device according to claim 1, wherein the device comprises at least one further throttle (11, 12) which is located either in the line between the collecting and equalizing container (1) and the opening into the line from the first pumping arrangement (2) to the opening side of the hydraulic cylinder (6) or in the line between the accumulator (5) and the opening into the line from the first pumping arrangement (2) to the closing side of the hydraulic cylinder (6). [3] Device according to claim 2, wherein the device comprises at least two further throttles (11, 12), so that at least one throttle (11, 12) is located in each of the lines mentioned in claim 2. [4] Device according to one of the preceding claims, wherein the 4Q piston pump has a flushing oil connection, and wherein the device comprises a changeover valve (85) and a flushing throttle (88), and wherein a flushing line branches off from the accumulator charging line between the second pump arrangement (8) and the check valve (86), which flushing line is connected to the flushing oil connection, and wherein the changeover valve (85) and the flushing throttle (88) are arranged in the flushing line. [5] Device according to one of the preceding claims, wherein the device comprises two pressure relief valves (30, 31), one of which is connected to one of the lines between the pilot-operated check valves (81, 81) and the hydraulic cylinder (6). [6] Device according to one of the preceding claims, wherein the device comprises an electrically controllable solenoid valve (20) which is arranged in the same line as the emergency closure solenoid valve (72) and is designed such that it can decouple the pilot valves (91, 92) from the accumulator (5). [7] Device according to one of the preceding claims, wherein the device comprises a connection point (50) for further emergency closing valves, which is arranged in the same line as the emergency closing solenoid valve (72). [8] Device according to one of the preceding claims, wherein the device comprises a connection point (40) for further consumers of hydraulic fluid, which is arranged in the line from the accumulator (5) to the hydraulic cylinder (6). [9] Device according to one of claims 4 to 8, wherein a return line branches off from the flushing line between the switching valve (85) and the flushing throttle (88), which is connected to the collecting and equalizing tank (1), and wherein a prestressed check valve (87) is arranged in the return line so that, after overcoming a predefined force, hydraulic fluid can pass through the return line into the collecting and equalizing tank (1). [10] Device according to one of claims 4 to 9, wherein a filter (83) is arranged in the flushing line. [11] Device according to one of claims 4 to 10, wherein a heat exchanger (84) is arranged in the flushing line. [12] Device according to one of the preceding claims, wherein the emergency closing solenoid valve (72) is designed such that it is permanently energized during operation of the hydraulic machine and is continuous in this position. [13] Device according to one of the preceding claims in conjunction with claim 6, wherein the emergency closing solenoid valve (72) is designed such that, when electrically excited, it can open the emergency closing valve (71) and decouple the pilot valves (91, 92) from the accumulator (5).

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