Method and arrangement to detect an oil leakage between sections of a hydraulic cylinder

Abstract

Provided is an arrangement and a method to detect an oil leakage between a first section and a second section of a hydraulic cylinder. A movable piston is arranged between the first and second section in a way that the piston changes position between the sections. The change in position is done in dependency of a difference between a first force, which acts at the first section on a first cross sectional area of the piston, and a second force, which acts at the second section on a second cross sectional area of the piston. The first section comprises hydraulic oil with a predefined first pressure, while the first force is calculated based on this pressure and based on the first area. The second section comprises hydraulic oil with a predefined second pressure, while the second force is calculated based on this pressure and based on the second area.

Claims

1. A method comprising: receiving an error report sequence from a wind turbine, the error report sequence including: (i) a pumping time becoming prolonged, (ii) a temperature of the hydraulic oil starting to increase, and (iii) an unwanted pitch tracking occurring during operation of the wind turbine; and initiating a detection of an oil leakage between a first section of a hydraulic cylinder and a second section of the hydraulic cylinder in response to the receiving the error report sequence, wherein an arrangement of the wind turbine is used to detect the oil leakage, the arrangement comprising: a movable piston arranged between the first section and the second section in a way that the movable piston changes a position between the first section and the second section dependent on a difference between a first force, which acts at the first section on a first cross sectional area of the movable piston, and a second force, which acts at the second section on a second cross sectional area of the movable piston; wherein the first section comprises hydraulic oil with a predefined first pressure, while the first force is calculated based on the predefined first pressure and based on the first cross-sectional area, and the second section comprises hydraulic oil with a predefined second pressure, while the second force is calculated based on the predefined second pressure and based on the second cross-sectional area; wherein the first section is connected with a remote controlled first valve, which is closed for the leakage detection; wherein a sensor is coupled with the movable piston in a way that any change in position is detected, while a change of the position results from the difference of the first force and the second force resulting from closing the remote controlled first valve and from an alignment of the first pressure to the second pressure due to the leakage between the first section of the hydraulic cylinder the second section of the hydraulic cylinder; wherein the sensor is coupled with a control unit, which is prepared and arranged to detect the leakage of oil based on the change of the position.

2. The method according to claim 1, wherein the sensor coupled with the movable piston is located remote from the hydraulic cylinder.

3. A wind turbine comprising: a plurality of rotor blades; a hydraulic pitch drive system for aligning a rotor blade of the plurality of rotor blades into incoming wind; and an arrangement for detecting an oil leakage between a first section and a second section of a hydraulic cylinder of the hydraulic pitch drive system, the arrangement comprising: a movable piston of the hydraulic cylinder that interacts, via a position of the movable piston, with the rotor blade to turn the rotor blade to specific pitch angles, wherein the movable piston is arranged between the first section and the second section in a way that the movable piston changes the position between the first section and the second section dependent on a difference between a first force, which acts at the first section on a first cross sectional area of the movable piston, and a second force, which acts at the second section on a second cross sectional area of the movable piston; wherein the first section comprises hydraulic oil with a predefined first pressure, while the first force is calculated based on the predefined first pressure and based on the first cross-sectional area, and the second section comprises hydraulic oil with a predefined second pressure, while the second force is calculated based on the predefined second pressure and based on the second cross-sectional area; wherein the first section is connected with a remote controlled first valve, which is closed for the leakage detection; wherein a sensor is coupled with the movable piston in a way that any change in position is detected, while a change of the position results from the difference of the first force and the second force resulting from closing the remote controlled first valve and from an alignment of the first pressure to the second pressure due to the leakage between the first section of the hydraulic cylinder the second section of the hydraulic cylinder; wherein the sensor is coupled with a control unit, which is prepared and arranged to detect the leakage of oil based on the change of the position; wherein detecting the oil leakage is initiated in response to the wind turbine reporting a sequence of errors including: (i) a pumping time becomes prolonged, (ii) a temperature of the hydraulic oil starts to increase, and (iii) an unwanted pitch tracking occurs during operation of the wind turbine.

4. The wind turbine according to claim 3, wherein the remote controlled first valve is connected with the control via a first control signal, thus hydraulic oil is provided in and out of the first section in a remote controlled manner.

5. The wind turbine according to claim 3, wherein a remote controlled second valve is connected with the control via a second control signal, thus hydraulic oil is provided in and out of the second section in a remote controlled manner.

6. The wind turbine according to claim 3, wherein the pitch angle is chosen between values, which are most relevant for wear and tear of the blade, the pitch angle being between 0° and 15° for detecting a leakage of oil.

7. The wind turbine according to claim 3, wherein the control unit is the control unit of the wind turbine, providing the control signals and performing the oil leakage detection automatically in response to the reporting of the sequence.

Description

BRIEF DESCRIPTION

(1) Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:

(2) FIG. 1 shows a schematic view of an arrangement in accordance with embodiments of the present invention; and

(3) FIG. 2 shows a schematic view of a wind turbine, which is equipped with the oil leakage detection in accordance with embodiments of the present invention.

DETAILED DESCRIPTION

(4) FIG. 1 shows the arrangement.

(5) A hydraulic cylinder HC comprises a first section S1, while hydraulic oil HO is provided in and out of the first section S1 by a predefined first pressure P1.

(6) The hydraulic cylinder HC even comprises a second section S2, while hydraulic oil HO is provided in and out of the second section S2 by a predefined second pressure P2.

(7) The hydraulic cylinder HC comprises a movable piston MP, which is arranged between the first section S1 and the second section S2 in a way that the movable piston MP changes its position POS between the sections S1 and S2.

(8) The hydraulic oil HO is applied to these sections S1 and S2 thus respective forces F1 and F2 are created.

(9) A first force F1 is created at the first section S1 according to this formula:
F1=P1*A1.

(10) P1 is the first pressure at the first section S1, which acts on a first cross sectional area A1 of the movable piston MP.

(11) A second force F2 is created at the second section S2 according to this formula:
F2=P2*A2.

(12) P2 is the second pressure at the second section S2, which acts on a second cross sectional area A2 of the movable piston MP.

(13) For this example, the effective cross-sectional areas A1 and A2 show this dependency:
A2=A1−AROD
while AROD is the cross-sectional area of a rod ROD, being part of the movable piston MP.

(14) The first section S1 is connected with a first valve V1, which is opened or closed remote controlled by a first control signal CS1.

(15) The second section S2 is connected with a second valve V2, which is opened or closed remote controlled by a second control signal CS2.

(16) A sensor SEN is coupled with the movable piston MP in a way that any change in the position POS of the movable piston MP is detected. The Sensor SEN is coupled with a control unit CONT, which is prepared and arranged to detect a leakage of hydraulic oil HO based on the change of the position POS.

(17) Let's assume a leakage LKG between the first section S1 and the second section S2 exists, i.e. due to a faulty seal of the movable piston MP.

(18) For the cylinder leakage test the first valve V1 is closed remote controlled by the controller CONT.

(19) Thus, in case of a hydraulic cylinder HC without faults the pressure P1 should be somehow “frozen” in its value.

(20) Due to the leakage LKG the first pressure and the second pressure will adapt to each other thus finally the first pressure P1 will show the same value than the second pressure P2:
P1=P2

(21) For the respective forces this situation results in:
F1=P1*A1
F1=P2*A1
and for
F2=P2*A2
F2=P2*(A1−AROD).

(22) By comparison of the forces F1 and F2 it is shown that for a leaking LKG in the hydraulic cylinder HC:
F1>F2
as the second (active) area A2 is smaller in its value than the first (active) area A1.

(23) Thus, the movable piston MP will change its position into the direction of the second section S2.

(24) Summoned up if there is a leakage LKG in the cylinder HC the pressures P1 and P2 will be equate and due to the known active areas A1 and A2 the movable piston MP will change its position POS.

(25) The change of the position POS will be detected by the sensor SEN, resulting in the knowledge that the hydraulic cylinder HC shows an internal leakage LKG.

(26) FIG. 2 shows details of a wind turbine WT, which is equipped with the oil leakage detection according to embodiments of the invention.

(27) The movable pistons MP (as described in FIG. 1) of i.e. two hydraulic cylinders HC1, HC2 interact with the blade BL thus the blade BL is turned into specific pitch angles PA.

(28) For the leakage detection the pitch angel PA is chosen between 0° and 15°, thus the surface of the rotor blade BL is aligned and turned in an optimum manner into the incoming wind W.

(29) These blade pitch angles are most relevant for wear and tear of the blade.

(30) The hydraulic cylinders HC1, HC2 are part of a hydraulic pitch drive system HPS of the wind turbine WT.

(31) The wind turbine control CONT is used to provide the control signals CS1, CS2 and to perform the oil leakage detection automatically.

(32) Although the invention has been illustrated and described in greater detail with reference to the preferred exemplary embodiment, the invention is not limited to the examples disclosed, and further variations can be inferred by a person skilled in the art, without departing from the scope of protection of the invention.

(33) For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.