EP3612735B1 - Pressure compensation device designed for underwater applications - Google Patents

Description

The present invention relates to a pressure compensation device for a hydraulic system designed for underwater applications.

The use of hydraulic and / or electrical and / or mechanical components under water, in particular at great depths, is problematic because the components can be damaged by water, in particular sea water. In particular, the high ambient pressure of the water makes pressure compensation necessary. Hydraulic pressure compensators can be used for this, which can raise the pressure level of a hydraulic system used in the underwater area to the ambient pressure prevailing in the water. For this purpose, membranes can be used which are exposed to the surrounding seawater on one side and which are connected to a reservoir of the hydraulic system on the other side. A disadvantage of this arrangement is that if the membrane which forms an interface is damaged, seawater can penetrate the hydraulic system. In addition, it must be taken into account that the membrane can be loaded with a compression spring, the spring force of which can decrease and thus the maintenance-free operating time can be limited.

DE 10 2011 009276 A1 discloses a device for transmitting a hydraulic working pressure in a pressure fluid for pressure actuation of hydraulic devices of deep-sea systems, in particular a so-called "blow-out preventer" (BOP), which is arranged as a safety system in a deep water borehole at great depths of the sea. The working pressure in the cylinder arrangement is not generated or transmitted by means of the seawater acting directly on a piston arrangement, but a pressure accumulator is connected upstream of the cylinder arrangement, from which the cylinder arrangement can be supplied with an actuating fluid that is under deep sea pressure. The movable separating element of the Pressure accumulator before the actuating fluid with the existing deep sea pressure. An energy store for a single closing movement of the cylinder arrangement is thus disclosed. However, such a device is not set up to carry out pressure compensation for a hydraulic system even when ambient pressures change, in particular reduced again, as may be desired for movable devices, such as diving boats, ROVs ( Remotely Operated Vehicles ) or AUVs ( Autonomous Underwater) Vehicle ) .

U.S. 3,581,774 discloses another known device adapted for underwater applications.

Proceeding from this, it is the object of the present invention to create a pressure compensation device and to specify a use which alleviates or even avoids the disadvantages mentioned. In particular, the ingress of seawater into the hydraulic system is to be reliably prevented in a structurally simple manner. Furthermore, the service life of the pressure compensation device should be increased significantly.

These objects are achieved with a pressure compensation device and a use according to the independent patent claims. Further refinements of the invention are specified in the dependent claims. It should be pointed out that the description, in particular in connection with the figures, cites further details and developments of the invention which can be combined with the features from the patent claims.

A pressure compensation device, which is set up for applications under water, contributes to this. It serves to seal an interior of a housing, which itself forms an (inner) fluid area, from the surrounding seawater area, with the pressure compensation device being able to raise a pressure level of the fluid area to at least the ambient pressure prevailing in the seawater area. The hydraulic system, which is set up for applications under water, can consequently comprise an interior of a housing (for example a hydraulic and / or electrical component, such as an electric motor, a pump, a tank or the like), which forms a fluid area which is opposite the surrounding seawater area is sealed. For this purpose, the at least one hydraulic pressure compensation device is provided, which can raise the pressure level of the fluid (hydraulic fluid, transformer oil, lubricant, etc.) in the fluid area to at least the ambient pressure prevailing in the (surrounding) seawater area.

The pressure compensation device is constructed in two stages such that at least one accumulator with a flexible wall area and at least one piston accumulator with a displaceable piston are arranged in series.

The device proposed here with a fluid-filled system (or hydraulic system or electrical system with transformer oil or mechanical system with lubricant) arranged under water has the particular advantage that underwater pressure compensation with a double (redundant) barrier against penetration of Lake water is realized. The two barriers are arranged and connected in series. In other words, this means, in particular, that the at least one reservoir with the flexible wall area can be acted upon by the seawater, as a result of which the flexible wall can be moved in response to the seawater pressure. The movement of the flexible wall can then (separated from the direct influence of the seawater) be transferred to a movement of the piston in the piston accumulator located downstream. A transmission medium, in particular a liquid, can be used for this purpose. The (resulting) movement of the piston can (directly) lead to a pressure adjustment in the fluid area, for which purpose the piston is preferably in direct contact with the fluid area. As a result, with this arrangement, two separate component failures (the accumulator and the piston accumulator) would have to occur before seawater can penetrate the interior of the system. The device is therefore characterized by high reliability, so that the system z. B. is designed for 20 years and more operating time and requires a minimum, preferably no maintenance.

The internal fluid (e.g. a hydraulic medium, transformer oil or lubricant) is insulated and can therefore have a pressure that is essentially the same or even higher than that of the environment (e.g. seawater). The two barriers (flexible wall and piston) mean that the seawater has to pass two sealing points (membrane and piston seal) before it can penetrate the system (redundancy to prevent system errors). Another factor contributing to reliability is that no compression spring directly acts on or loads the flexible wall (e.g. in the manner of a membrane), which significantly increases the service life of the system.

Furthermore, the piston of the piston accumulator is loaded by at least one compression spring. The compression spring can be used to set a predeterminable bias, for. B. to set an increased pressure level on the fluid area compared to the pressure generated by the seawater. The piston is designed in particular with a rigid piston plate on which the compression spring acts. Damage or overloading of this rigid piston due to the compression spring load can thus be permanently avoided.

The fluid in the fluid area is preferably pretensioned at 0.5 to 10 bar with respect to the pressure of the surrounding seawater area. For this purpose, a correspondingly designed compression spring can be provided in the piston accumulator, with which the preload above the seawater pressure level can be adjusted.

The storage tank (in operative connection with the seawater) with a flexible wall area can be a membrane storage tank or a bladder storage tank. In the case of a diaphragm accumulator, a diaphragm can be provided which is essentially plate-shaped, the circumference of which is (firmly) connected to a memory wall, and which is movable radially inwardly in response to a pressure prevailing there. A bladder accumulator can be designed with a flexible wall which encloses a predeterminable bladder accumulator volume and can move axially and radially in response to a pressure prevailing there. The flexible wall and / or the membrane are in particular fluid-tight and resistant to contact with seawater under high pressure.

A displacement sensor is advantageously assigned to the piston of the piston accumulator. The displacement sensor is set up in particular to detect the current stroke or the current position of the piston with reference to a reference position or the piston accumulator. A displacement transducer in this sense is in particular a sensor by means of which a position of the piston can be determined or measured directly / indirectly. The sensor can comprise a limit switch, a pressure switch. This enables a possible leakage to be monitored by observing the position of the piston, e.g. B. if a movement of the piston is determined with unchanged pressure conditions.

The piston of the piston accumulator can comprise a plurality of sealing devices arranged downstream (in the effective direction of the pressure). The piston can preferably seal an opening of a second interior space of the piston accumulator with respect to the fluid area. The piston can additionally have at least one seal that can swell (on contact with seawater) compared to a cylinder tube (piston-cylinder housing).

It is preferred that with the at least one reservoir with a flexible wall area and the at least one piston reservoir, an intermediate space is formed which is filled with a transmission medium (fluid and / or gas). A (outlet-side) second interior space of a diaphragm or bladder accumulator and a (inlet-side) first interior space of a piston accumulator advantageously form an intermediate space (partially or completely) filled with a fluid and / or gas. The fluid (or transmission fluid) in the (output-side) second interior space of the accumulator with a flexible wall area and the (input-side) first interior space of the piston accumulator is preferably a hydraulic fluid, a mechanical grease-like medium or a dielectric transformer oil.

The fluid in the (outlet-side) second interior space of the piston accumulator and in the fluid area is advantageously an oil, in particular a transformer oil.

The pressure compensation device is further preferably designed in the manner of a hollow cylinder in such a way that an internal bladder accumulator is surrounded by an external piston accumulator. This enables a particularly compact design. In this way, seawater can expand / shrink the bladder accumulator inside the piston accumulator (axially and / or radially) according to the ambient pressure underwater. The resulting change in volume of the bladder accumulator shifts z. B. an externally lying (preferably essentially incompressible) transmission medium, which in turn results in a displacement (displacement) of the piston inwards / outwards. For this purpose, a piston plate can interact with the bladder accumulator loosely or only via the transmission medium.

An arrangement is expedient in which several pressure compensation elements are arranged in bores in the drum shell of a type of drum, through the central opening of which an adjusting axis of an electronic or hydraulic component can be guided. For this purpose, the drum can have a plurality of bores arranged distributed over a drum circumference and a central passage opening. The holes are suitable for holding pressure compensation elements. The pressure compensation elements can be connected in parallel and / or in series with one another in order to increase the redundancy in the event of a failure and / or to adapt the stroke compensation (jointly). The central passage opening can be arranged (sealing) around an adjusting axis of an electronic or hydraulic component (electric motor, pump, cylinder compensation, etc.).

According to another aspect, the use of a pressure compensation device proposed here (or the above arrangement with a drum) for applying pressure to at least one housing filled with fluid (e.g. with hydraulic fluid, oil, grease, lubricant, etc.) for a hydraulic adjusting axis of an electric motor, a Suggested pump and / or cylinder compensation. The at least one pressure compensation device is used in particular to apply ambient pressure (water pressure) to an integrated hydraulic adjusting axis (electric motor, pump, cylinder compensation) in its oil-filled housing. For this purpose, the (several) pressure compensators are preferably accommodated in a type of drum. The cylinder or a rod of the cylinder can be filled through the central opening of the drum, which enables a space-saving, integrated design.

The measures proposed here are based in particular on the idea of designing a two-stage pressure compensator with a bladder or diaphragm accumulator that forms the seawater / intermediate pressure space interface and a piston or spring-piston accumulator that makes contact with the hydraulic reservoir. Instead of one, there are now two interfaces; this increases the tightness and durability. In addition, a spring can be used to set a prestress in the piston or spring-piston accumulator which is above the seawater pressure level.

Fig. 1:

einen Schaltplan einer Druckkompensationseinrichtung mit - in Reihe angeordnet-einem Membranspeicher und einem Kolbenspeicher,

Fig. 2:

Blockschaltbild einer Druckkompensationseinrichtung zwischen Seewasser- und (innerem) Fluidbereich,

Fig. 3:

einen Schaltplan einer Druckkompensationseinrichtung mit zwei Membranspeichern und drei Kolbenspeichern, die jeweils parallel zueinander angeordnet sind,

Fig. 4:

eine konstruktive Ausführungsform einer Druckkompensationseinrichtung, und

Fig. 5:

eine Anordnung einer Mehrzahl von Druckkompensationseinrichtungen in einem gemeinsamen trommelartigen Halteelement.

The invention and the technical environment are explained in more detail below with reference to figures. The same components are identified by the same reference numerals. The representations are schematic and not intended to illustrate proportions. The explanations given with reference to individual details of a figure can be extracted and freely combined with facts from other figures or the above description, unless something else is mandatory for a person skilled in the art or such a combination is explicitly prohibited here. They show schematically:

Fig. 1:

a circuit diagram of a pressure compensation device with - arranged in series - a diaphragm accumulator and a piston accumulator,

Fig. 2:

Block diagram of a pressure compensation device between the seawater and (inner) fluid area,

Fig. 3:

a circuit diagram of a pressure compensation device with two membrane accumulators and three piston accumulators, which are each arranged parallel to one another,

Fig. 4:

a structural embodiment of a pressure compensation device, and

Fig. 5:

an arrangement of a plurality of pressure compensation devices in a common drum-like holding element.

Fig. 1 shows the basic representation of a circuit diagram of a pressure compensation device 1 with - arranged and connected in series - a memory 2 with a flexible wall area 4 and a piston memory 3 with a displaceable piston 5. The memory 2 with flexible wall area 4 is in the Fig. 1, 2 and 3rd using the example of a diaphragm accumulator and in the Fig. 4 and 5 explained using the example of a bladder accumulator. Furthermore, the flexible wall 4 is in the Fig. 1, 2 and 3rd using the example of an impenetrable membrane 9 and in the Fig. 4 and 5 explained using the example of an impenetrable bladder 23.

The diaphragm accumulator 2 has a first interior space 2.1 (on the inlet side) and a second interior space 2.2 (on the outlet side). on, which by a flexible wall area 4, z. B. an elastic metal membrane (or according to Fig. 4 a rubber bladder), separated from each other and sealed against each other. The piston accumulator 3 has a first inner space 3.1 (on the inlet side) and a second inner space 3.2 (on the outlet side), which are separated from one another by the displaceable piston 5 and sealed from one another by seals. 6 with a dash-dotted line denotes a schematic dividing line, on the right-hand side of which the seawater area 7 is located and on the left-hand side of which the (inner) fluid area 8 is located. A filter 35 for the seawater is upstream of the membrane storage tank. The seawater filter can be used to prevent dirt particles from clogging the bore to the membrane. Furthermore, a displacement sensor 10 is assigned to the displaceable piston 5 of the piston accumulator 3.

Fig. 2 illustrates a block diagram of the pressure compensation device 1, e.g. B. also according to Fig. 1 , between the seawater area 7 and the fluid area 8. The first interior space 2.1 of the membrane reservoir 2 is connected to the seawater area 7 and the second interior space 3.2. of the piston accumulator 3 is connected to the fluid area 8. The second interior 2.2 of the diaphragm accumulator 2 and the first interior 3.1 of the piston accumulator 3 functionally form a common interspace 11. In terms of construction, the interspace 11 can be designed as a single space. The intermediate space 11 can also consist of two individual spaces, that is to say of the second interior 2.2 and the first interior 3.1, which are connected to one another by a pipeline or the like. At 12 there is a first limit, e.g. B. a membrane 9, and with 13 is a second limit, z. B. a piston 5, designated. The two boundaries 12, 13 form a twofold security (redundancy) against the ingress of sea water into the fluid area 8.

The first interior space 2.1 of the membrane reservoir 2 is filled with seawater (first medium 27) which loads one side of the membrane 9 with the ambient pressure prevailing in the water. The water pressure in the sea water area 7 and in the first interior space 2.1 is the same. In the space 11 there is a second medium 28 (transmission medium), e.g. B. a hydraulic fluid, a fatty substance, a dielectric transformer oil or a gas, especially nitrogen. The second medium 28 is pressurized through the other side of the membrane 9, so that the intermediate space 11 forms an intermediate pressure space. The pressure of the medium 28 continues to load one side of the piston 5 of the piston accumulator 3. The second interior 3.2 of the piston accumulator 3 is filled with a third medium 29, preferably with transformer oil. Here, the other side of the piston 5 exerts pressure on the medium 29. This pressure also acts on the medium 29, which the (not shown) downstream devices such. B. tank, housing, fills. The pressure in the inner fluid area 8 and in the second interior 3.2 of the piston accumulator 3 is therefore the same.

The system device connected downstream of the pressure compensation device 1 can be designed as a container-like module, with several modules of this type being able to be deposited on the seabed. The container is filled with a dielectric liquid, e.g. B. a hydraulic oil, filled so that all components in the module are immersed in the liquid. The pressure compensation device 1 achieves pressure compensation between the interior of the container and the external environment (seawater area 7) in such a way that the liquid in the container is put under the same pressure as is prevailing in the external environment. For this purpose, the pressure compensation device 1 has two separating surfaces or boundary surfaces: a flexible separating element (membrane 9 or bladder) 23), which is in contact on one side with the sea water, and a piston 5, which is acted upon on its other side by the liquid in the container. The space 11 is arranged between the two separating elements. The pressure compensation device 1 presented here has the particular advantage that seawater that has unintentionally penetrated through the membrane 9 does not (directly) enter the container, but remains in the intermediate space 11, hindered by the piston 5, and can be removed there. There is thus a double security against ingress of sea water. An additional further safeguard is that the piston 5 of the piston accumulator 3 is secured by a compression spring 22 (see also Fig. 4 ) is applied, whereby the medium 29 is under a bias. The preload pressure is slightly greater than the ambient pressure, e.g. B. 0.5 to 10 bar, so that the ingress of seawater into the downstream device is prevented. In order to detect a leak in the piston accumulator 3, the piston 5 is assigned the displacement sensor 10, which monitors the position of the piston 5.

Fig. 3 shows a circuit diagram of a pressure compensation device, such as. B. also after Fig. 1 , but with two membrane accumulators 2a, 2b and three piston accumulators 3a, 3b, 3c, which are each arranged and connected parallel to one another. In this way, a larger volume of the interior spaces of the diaphragm accumulators 2a, 2b and the piston accumulators 3a, 3b, 3c is realized.

The Fig. 4 illustrates a structural embodiment of a pressure compensation device 1, in particular also according to the in FIG Fig. 1 shown circuit diagram. The embodiment is characterized in that the accumulator 2 with the flexible wall area 4 and the piston accumulator 3 are designed in the manner of a compact cylinder, whereby a particularly space-saving design is realized. The pressure compensation device 1 is designed like a hollow cylinder in such a way that an internal bladder accumulator 2 is surrounded by an external piston accumulator 3. How Fig. 4 illustrated, the piston accumulator 3 consists of a cylinder tube 14 and a piston 5 as a separating element. On a first end face 14.1 of the cylinder tube 14 there is a closure cover 15 which has a central through opening 16. On the other, second end face 14.2 of the cylinder tube 14, there is a central through opening 18 which opens with the inner fluid area. The piston 5 is sealed with seals 19 against the inner circumferential surface 14.3 of the cylinder tube 14. From the surface facing the opening 16 A first hollow cylinder 20 grows out of the piston 5, and a further hollow cylinder 21, the open ends of which overlap one another, grows out of the surface of the closure cap 15 facing the opening 18. A compression spring 22 is arranged between the outer first hollow cylinder 20 and the inner jacket surface 14.3, one end of which is supported on the closure cover 15 and the other end on the piston 5. In the inner cavity formed by the hollow cylinders 20 and 21 there is a bladder 23, for. B. made of an elastomer, a bladder accumulator 2, which serves as a partition. The bladder 23 has two (axially) opposite end regions, with the end regions facing the piston 5 or the closure cover 15 and the central region facing the hollow cylinders 20, 21, each at a distance, in such a way that an intermediate space 11 is formed. The lower end region of the bladder 23 merges into a hollow cylinder-like, continuous connection 24 with an opening 34 for the passage of seawater (first medium 27) which extends through the opening 16.

The mode of operation is that a first medium 27 (seawater) loaded with pressure fills the bladder 23, which expands under the pressure and thus in turn displaces a second medium 28 outside the bladder 23. This medium 28 is in turn clamped between the bladder 23 and the piston 5 and, by expanding the bladder 23 and the medium 28, drives it in the axial direction (cylinder function). The piston 5 additionally seals against the cylinder tube 14 by means of a piston seal 19 (redundant). The piston 5 is preloaded with a compression spring 22 and thus ensures that the system is pretensioned against the pressure from the first medium 27. Thus (on the output side) there is a medium on the piston side, which is a third medium 29 or the same medium as the second medium 28 can be separated from and loaded with a bias against the first medium 27.

Optionally, the pressure compensation can be safeguarded against a possible leakage of the first medium 27 by damaging the bladder 23 when the preload is fully discharged (piston 5 in end position) as well as with pressure compensation, e.g. B. Leakage of the piston seal 19 may be provided. The piston 5 of the pressure compensation moves into the end position by the spring 22 and thus closes the opening 18 at the outlet by an (ring-shaped) seal 25 on the piston 5. A cylindrical projection 30 on the piston 5 preferably engages in the opening 18 in a form-fitting manner.

Furthermore, protection can optionally be provided by an additional sealing ring 31 on the piston 5, which swells, for example, through contact with another medium, apart from the operating fluid or transmission fluid. The swelling of the sealing ring 31 results in a form fit, which creates a seal between the piston 5 and the cylinder tube 14.

The pressure compensation is used to balance two pressures in a system that work with media that are used separately, such as. B. Oil and water. As a result of this pressure compensation, one side with a higher pressure can be pretensioned by means of the spring 22 in order to prevent the other medium with a lower pressure from penetrating into the system. In addition, the separation is redundant, since here two different methods of separating liquid or gaseous media are arranged in series without requiring a large amount of space.

Fig. 5 shows an arrangement for a plurality of pressure compensation devices 1 (for example according to FIG Fig. 4 ) in a common holding element. The pressure compensation devices 1 are arranged parallel to one another in the longitudinal direction. This creates a larger volume for pressure compensation (redundancy). A hollow cylinder 32 in the manner of a drum - in Fig. 5 cut open in half - has a cylinder jacket 32.1 (hollow cylinder wall) and a cylinder interior 32.2. The cylinder jacket 32.1 is penetrated by a plurality of through bores 33.1, 33.2 aligned in the longitudinal direction parallel to the central axis, into each of which a pressure compensation device 1 is inserted in a form-fitting manner. In Fig. 5 only one pressure compensation device 1 arranged in a bore 33 - cut open in half - is shown. The hollow cylinder 32 is formed as a drum similar to a revolver magazine.

The pressure compensation device 1 according to Fig. 5 can be used to apply ambient pressure (water pressure) to an integrated hydraulic adjusting axis 17 (electric motor, pump, cylinder compensation) in its oil-filled housing. The (several) pressure compensators 1 are accommodated in a type of drum for this purpose. The cylinder or a rod of the cylinder can be guided through the central opening or the cylinder interior 32.2 of the drum, which enables a space-saving, integrated design.

List of reference symbols

1

Pressure compensation device

2, 2a, 2b

Storage with flexible wall area

2.1

first interior

2.2

second interior

3, 3a to 3c

Piston accumulator

3.1

first interior

3.2

second interior

4th

flexible wall area

5

piston

6th

parting line

7th

Seawater area

8th

Fluid area

9

membrane

10, 10a, 10b

Weggeber

11

Space

12th

first limit

13th

second limit

14th

Cylinder tube

14.1

first face

14.2

second face

14.3

Inner circumferential surface

15th

Sealing cap

16

opening

17th

Positioning axis

18th

opening

19th

poetry

20th

first hollow cylinder

21

second hollow cylinder

22nd

Compression spring

23

bladder

24

connection

25th

poetry

26th

poetry

27

first medium

28

second medium

29

third medium

30th

approach

31

Sealing ring

32

Hollow cylinder

32.1

Cylinder jacket

32.2

Cylinder interior

33.1, 33.2

Drilling

34

opening

35

filter

Claims (9)

1. Pressure compensation device (1) designed for underwater applications, by means of which an interior of a housing which forms a fluid region (8) can be sealed with respect to the surrounding seawater region (7), wherein a pressure level of the fluid region (8) can be raised at least to the ambient pressure prevailing in the seawater region (7) by means of the pressure compensation device (1), wherein the pressure compensation device (1) is constructed in two stages in such a way that

   - at least one accumulator (2; 2a, 2b) with a first interior (2.1) connected to the seawater region (7), with a second interior (2.2), and with a flexible wall region (4) therebetween, and also

   - at least one piston accumulator (3; 3a to 3c) with a displaceable piston (5), which seals a first interior (3.1) connected to the second interior (2.2) of the accumulator (2; 2a, 2b) with respect to a second interior (3.2) connected to the fluid region (8) and is loaded by means of at least one compressions spring (22), are arranged in series.
2. Pressure compensation device (1) according to Patent Claim 1, wherein the compression spring is designed in such a way that it sets a prestress of 0.5 to 10 bar in the piston accumulator (3; 3a to 3c).
3. Pressure compensation device (1) according to Patent Claim 1 or 2, wherein the accumulator with a flexible wall region (4) is a diaphragm accumulator or bladder accumulator.
4. Pressure compensation device (1) according to one of the preceding patent claims, wherein the piston (5) of the piston accumulator (3, 3a to 3c) is assigned a displacement transducer (10a, 10b).
5. Pressure compensation device (1) according to one of the preceding patent claims, wherein the piston (5) of the piston accumulator comprises a plurality of downstream sealing devices (19, 25, 31).
6. Pressure compensation device (1) according to one of the preceding patent claims, wherein an interspace (11), which is filled with a transmission medium, is formed by the at least one accumulator (2; 2a, 2b) with a flexible wall region (4) and by the at least one piston accumulator (3; 3a to 3c).
7. Pressure compensation device (1) according to one of Patent Claims 1-2, 4-6, wherein said device is designed in the manner of a hollow cylinder in such a way that an inner accumulator (2; 2a, 2b) with a flexible bladder (23) is surrounded by an outer piston accumulator (3).
8. Arrangement comprising a plurality of pressure compensation devices (1) according to one of the preceding patent claims, which are arranged in bores (33.1, 33.2) in a cylinder jacket (32.1) of a hollow cylinder (32) in the manner of a drum through whose central opening an actuating shaft (17) of an electronic or hydraulic component can be guided.
9. Use of the pressure compensation device (1) according to one of Patent Claims 1-7 for pressurizing at least one fluid-filled housing for an hydraulic actuating shaft of an electric motor, of a pump or of a cylinder compensator.

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