Fastening device

Abstract

This utility model provides a fastening device, including a main nut and multiple screws. The inner surface of the main nut has an internal thread that mates with the external thread of a mounting stud used to fix the casing of a steam turbine. Between the inner and outer surfaces of the main nut, multiple through holes with internal threads that mate with the external threads of the shanks of the screws are formed along the axial direction of the main nut. When the main nut is installed on the mounting stud, the shanks of the screws enter the through holes from the first end of the main nut and extend out from the second end of the main nut until the steam turbine casing provides a thrust to the screws in a direction parallel to the axis of the mounting stud and away from the steam turbine casing. By using multiple screws, this application increases the contact pressure between the internal thread of the main nut and the external thread of the mounting stud, enabling the upper and lower casings of the steam turbine to be fastened without heating, thereby ensuring the effectiveness of the blue coating detection.

Description

Technical Field

[0001] This utility model relates to the field of machining technology, and in particular to a fastening device. Background Technology

[0002] In the field of power generation technology using steam as the working fluid, the steam turbine is one of the key pieces of equipment, and its safe, efficient, and stable operation is extremely important in the power production process. The working fluid enters the steam turbine through the steam inlet pipeline system to complete the process of converting thermal energy into mechanical energy.

[0003] To ensure a tight fit between the upper and lower split surfaces of the turbine cylinder and prevent steam or oil leaks during operation that could affect the turbine's normal operation and performance, the turbine cylinder is typically blue-coated for inspection after the fastening nuts are installed and tightened on the studs that run through the upper and lower outer casings of the turbine.

[0004] However, current fastening nuts typically use thermal expansion nuts to ensure a tight fit in the high-temperature environment of steam turbine operation. However, during the blueing inspection process, heating the fastening nuts can cause the blue ink to melt, affecting the blueing effect. Utility Model Content

[0005] To address the aforementioned technical problems, this utility model provides a fastening device to at least solve or alleviate these problems.

[0006] According to a first aspect of the present invention, a fastening device is provided, comprising: a main nut and a plurality of screws; the inner surface of the main nut is provided with an internal thread that mates with the external thread of a mounting stud; between the inner surface and the outer surface of the main nut, a plurality of through holes having internal threads that mate with the external threads of the shanks of the plurality of screws are formed along the axial direction of the main nut; when the main nut is installed on the mounting stud, the shanks of the plurality of screws enter the through holes from the first end of the main nut and extend out from the second end of the main nut until the turbine casing provides a thrust to the plurality of screws in a direction parallel to the axis of the mounting stud and away from the turbine casing, so that the plurality of screws provide a fastening force to the main nut parallel to the direction of the thrust, thereby increasing the pressure between the internal thread of the main nut and the external thread of the mounting stud, thereby fixing the main nut on the mounting stud, wherein the first end of the main nut is opposite to the second end of the main nut.

[0007] Optionally, the fastening device further includes: a washer; the inner side of the washer is provided with an internal thread that mates with the external thread of the mounting stud; when the main nut and the washer are mounted on the mounting stud, the shank of the plurality of screws extends from the second end of the main nut and abuts against the first end of the washer, and the second end of the washer abuts against the outer casing of the steam turbine, wherein the first end of the washer is opposite to the second end of the washer.

[0008] Optionally, the outer diameter of the washer is equal to the outer diameter of the main nut.

[0009] Optionally, the through holes are arranged circumferentially along the main nut, and the spacing between adjacent through holes is the same.

[0010] Optionally, the diameters of the shanks of the plurality of screws are equal, and the diameters of the plurality of through holes opened on the main nut are equal.

[0011] Optionally, the shortest distance between the multiple through holes on the main nut and the outer side of the main nut is greater than 1 cm, and the shortest distance between the through holes and the inner side of the main nut is greater than 1 cm.

[0012] Optionally, when the shanks of the plurality of screws extend from the second end of the main nut and abut against the first end of the washer, the heads of the plurality of screws do not contact the first end of the main nut.

[0013] As can be seen from the above technical solution, by setting multiple screws, the contact pressure between the internal thread of the main nut and the external thread of the mounting stud can be increased, which can fasten the upper and lower casings of the turbine without heating, thereby ensuring the effect of the blue coating test. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0015] Figure 1 This is a schematic diagram of a fastening device according to an embodiment of this application;

[0016] Figure 2 This is a schematic diagram of a fastening device according to another embodiment of this application.

[0017] List of reference numerals in the attached diagram:

[0018] 10: Fastening device; 11: Main nut; 12: Screw

[0019] 13: Gasket; 20: Mounting stud; 30: Turbine casing Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art should fall within the protection scope of this utility model.

[0021] Figure 1 This is a schematic diagram of a fastening device according to an embodiment of this application, as shown below. Figure 1 As shown, the fastening device 10 includes a main nut 11 and a plurality of screws 12. The inner surface of the main nut 11 is provided with an internal thread that mates with the external thread of the mounting stud used to fix the turbine casing 30. Between the inner and outer surfaces of the main nut 11, a plurality of through holes with internal threads that mate with the external threads of the shanks of the plurality of screws 12 are formed along the axial direction of the main nut 11. When the main nut 11 is installed on the mounting stud, the shanks of the plurality of screws 12 enter the through holes from the first end of the main nut 11 and extend out from the second end of the main nut 11 until the turbine casing 30 provides a thrust to the plurality of screws 12, so that the plurality of screws 12 provide a fastening force to the main nut 11 according to the thrust, thereby increasing the pressure between the internal thread of the main nut 11 and the external thread of the mounting stud 20, thereby fixing the main nut 11 on the mounting stud 20. The first end of the main nut 11 is opposite to the second end of the main nut 11.

[0022] The steam turbine includes multiple mounting studs 20, which are used to secure the upper and lower outer casings 30 of the steam turbine together. Additionally, thermal expansion nuts are installed on the mounting studs 20. During turbine operation, these thermal expansion nuts, operating at high temperatures, further tighten the upper and lower outer casings 30. However, after installation, a blue coating test is typically performed to ensure there are no large gaps between the upper and lower outer casings 30. If the thermal expansion nuts are heated during this process to maintain the tightening effect, the blue coating oil used for the blue coating test will melt, affecting the blue coating effect. Therefore, a fastening device 10 can be installed on the mounting stud. During installation, the main nut 11 of the fastening device 10 is screwed onto the mounting stud, creating a small gap between the second end of the main nut 11 and the turbine casing 30. Then, multiple screws 12 are screwed into the through holes of the main nut 11 until the shanks of the screws 12 extend beyond the second end of the main nut 11 and abut against the turbine casing 30. After installation, the pressure exerted by the screws 12 on the turbine casing 30 causes a thrust from the turbine casing 30 towards the screws 12 in a direction parallel to the axis of the mounting stud 20 and away from the turbine casing 30. This thrust acts on the main nut 11. When the fastening device 10 is located below the turbine casing 30, the angle between the direction of gravity of the main nut 11 and the direction parallel to the axis of the mounting stud 20 and away from the turbine casing 30 is less than 90°. Therefore, the thrust will increase the pressure between the internal thread of the main nut 11 and the external thread of the mounting stud 20, thereby increasing the static friction between the internal thread of the main nut 11 and the external thread of the mounting stud 20, and thus making the main nut 11 and the mounting stud 20 more secure. When the fastening device 10 is positioned above the turbine casing 30, the angle between the gravity direction of the main nut 11 and the direction parallel to the axis of the mounting stud 20 and away from the turbine casing 30 is greater than 90°. At this time, by setting the torque for tightening multiple screws 12, it is ensured that the force after the thrust is offset by the gravity parallel to the axis of the mounting stud 20 is greater than the gravity parallel to the axis of the mounting stud 20. This ensures that the pressure between the internal thread of the main nut 11 and the external thread of the mounting stud 20 increases, thereby increasing the static friction between the internal thread of the main nut 11 and the external thread of the mounting stud 20. This makes the main nut 11 and the mounting stud 20 more secure, ensuring that the turbine casing 30 is fixed even when the main nut 11 does not move.

[0023] Specifically, the pitch of the threads of multiple screws 12 can be set to be smaller than the pitch of the external threads of the mounting stud 20, thereby improving the force transmission effect of the multiple screws 12 on the main nut 11. Alternatively, by increasing the number of multiple screws 12, the magnitude of the thrust borne by a single screw 12 in the direction parallel to the axis of the mounting stud 20 and away from the turbine casing 30 from the turbine casing can be reduced.

[0024] Specifically, the through holes are arranged circumferentially along the main nut 11, and the spacing between adjacent through holes is the same.

[0025] By setting through holes arranged circumferentially along the main nut 11 and with the same spacing between adjacent through holes, the multiple screws 12 that abut against the fixed end can exert a reverse thrust on the turbine casing 30 evenly on the main nut 11, thereby improving the uniformity of pressure between the internal thread of the main nut 11 and the external thread of the mounting stud 20, and thus improving the fastening effect.

[0026] Specifically, the diameters of the shanks of the multiple screws 12 are equal, and the diameters of the multiple through holes opened on the main nut 11 are equal.

[0027] By setting the diameter of the shank of the multiple screws 12 to be equal, the distance between the head of the multiple screws 12 and the first end of the main nut 11 can be equal after the shank of the multiple screws 12 contacts the turbine casing 30. This makes it easy to observe whether the multiple screws 12 have made contact with the turbine casing 30. By setting the diameter of the multiple through holes opened on the main nut 11 to be equal, it can be further ensured that the reverse thrust generated by the turbine casing 30 on the multiple screws 12 that abut against the turbine casing 30 is evenly applied to the main nut 11.

[0028] Specifically, the shortest distance between the multiple through holes on the main nut 11 and the outer side of the main nut 11 is greater than 0, and the shortest distance between the through holes and the inner side of the main nut 11 is greater than 1cm.

[0029] By setting the shortest distance between the multiple through holes on the main nut 11 and the outer and inner surfaces of the main nut 11 to be greater than 1 cm, the structural strength of the fastening device 10 can be improved and the possibility of cracking of the main nut 11 can be reduced.

[0030] In this embodiment, by setting multiple screws 12, the contact pressure between the internal thread of the main nut 11 and the external thread of the mounting stud 20 can be increased, which can fasten the upper and lower casings 30 of the steam turbine without heating, thereby ensuring the effect of the blue coating detection.

[0031] Figure 2 This is a schematic diagram of a fastening device according to another embodiment of this application, as shown below. Figure 2As shown, the fastening device 10 also includes a washer 13. The inner side of the washer 13 is provided with an internal thread that mates with the external thread of the mounting stud 20. When the main nut 11 and the washer 13 are installed on the mounting stud 20, the shanks of the plurality of screws 12 extend from the second end of the main nut 11 and abut against the first end of the washer 13. The second end of the washer 13 abuts against the outer casing 30 of the steam turbine. The first end of the washer 13 is opposite to the second end of the washer 13.

[0032] During installation, first screw the washer 13 into the mounting stud 20 until the second end of the washer 13 abuts against the turbine casing 30. Then screw the main nut 11 into the mounting stud 20 until the main nut 11 abuts against the washer 13. Then screw it a quarter turn in the opposite direction of screwing the main nut 11 into the mounting stud 20 to create a gap between the main nut 11 and the washer 13. Then, use a torque wrench to screw multiple screws 12 into the through holes on the main nut 11 according to the calculated torque until the shank of the multiple screws 12 extends out of the second end of the main nut 11 and abuts against the washer 13. After installation, the gasket 13 can provide pressure to the turbine casing 30, so that the turbine casing 30 generates a reverse thrust on the gasket 13. The gasket 13 transmits this thrust to the multiple screws 12. The thrust on the multiple screws 12 will act on the main nut 11, thereby increasing the pressure between the internal thread of the main nut 11 and the external thread of the mounting stud 20, thus making the main nut 11 and the mounting stud 20 more secure. Without the main nut 11 moving, the turbine casing 30 can be fixed.

[0033] Specifically, the number of screws 12 can be set to 12.

[0034] Specifically, the outer diameter of the washer 13 is equal to the outer diameter of the main nut 11.

[0035] By setting the outer diameter of the washer 13 to be equal to the outer diameter of the main nut 11, the same mold as the main nut 11 can be used to produce the washer 13. After production using the same mold, the washer 13 does not need to be drilled and can be directly cut into multiple pieces, thereby saving production costs.

[0036] Specifically, when the shanks of the plurality of screws 12 extend from the second end of the main nut 11 and abut against the first end of the washer 13, the heads of the plurality of screws 12 do not contact the first end of the main nut 11.

[0037] Specifically, the material of gasket 13 can be 2Cr12MoV alloy. This material has high strength and is resistant to high temperatures.

[0038] By setting the shanks of multiple screws 12 to extend from the second end of the main nut 11 and abut against the first end of the washer 13, the heads of the multiple screws 12 do not contact the first end of the main nut 11. This allows the reaction forces of the multiple screws 12 to be transmitted to the main nut 11 through the threads, thus avoiding the problem of the main nut 11 cracking and being damaged due to some of the reaction forces being transmitted to the first end of the main nut 11.

[0039] It should be noted that, Figure 2 The mounting stud 20 shown is a stud that penetrates the turbine housing 30. Therefore, in this case, a fastening device 10 needs to be installed above the upper housing and below the lower housing of the turbine housing 30. However, the mounting stud 20 can also be fixed to one of the housings of the turbine housing 30. In this case, the fastening device 10 only needs to be installed on the outside of the other housing.

[0040] In this embodiment of the application, by setting a shim 13, the shanks of multiple screws 12 can be prevented from directly contacting the turbine casing 30, thereby ensuring that the turbine casing 30 is fastened while protecting the turbine casing 30.

[0041] It should be noted that not all steps and modules in the above processes and system structure diagrams are mandatory; some steps or modules can be omitted as needed. The execution order of each step is not fixed and can be adjusted as required. The system structure described in the above embodiments can be a physical structure or a logical structure. That is, some modules may be implemented by the same physical entity, or some modules may be implemented by multiple physical entities, or they may be jointly implemented by certain components in multiple independent devices.

[0042] In this patent application, nouns and pronouns relating to people are not limited to specific genders.

[0043] In the above embodiments, the hardware modules can be implemented mechanically or electrically. For example, a hardware module may include permanent dedicated circuitry or logic (such as a dedicated processor, FPGA, or ASIC) to perform the corresponding operations. The hardware module may also include programmable logic or circuitry (such as a general-purpose processor or other programmable processor), which can be temporarily configured by software to perform the corresponding operations. The specific implementation method (mechanical, dedicated permanent circuitry, or temporarily configured circuitry) can be determined based on cost and time considerations.

[0044] The present application has been shown and described in detail above with reference to the accompanying drawings and preferred embodiments. However, the present application is not limited to these disclosed embodiments. Based on the above multiple embodiments, those skilled in the art will know that more embodiments of the present application can be obtained by combining the code review methods in the different embodiments above. These embodiments are also within the protection scope of the present application.

Claims

1. A fastening device (10) characterized by, The fastening device (10) includes: a main nut (11) and a plurality of screws (12); The inner side of the main nut (11) is provided with an internal thread that mates with the external thread of the mounting stud (20) used to fix the housing (30) of the steam turbine. Between the inner side of the main nut (11) and the outer side of the main nut (11), a plurality of through holes with internal threads that mate with the external threads of the shank of the plurality of screws (12) are provided along the axial direction of the main nut (11). When the main nut (11) is installed on the mounting stud (20), the shanks of the plurality of screws (12) enter the through hole from the first end of the main nut (11) and extend out from the second end of the main nut (11) until the turbine casing (30) provides a thrust to the plurality of screws (12) in a direction parallel to the axis of the mounting stud (20) and away from the turbine casing (30), so that the plurality of screws (12) provide a tightening force to the main nut (11) according to the thrust, which is parallel to the direction of the thrust, thereby increasing the interaction force between the internal thread of the main nut (11) and the external thread of the mounting stud (20), thereby fixing the main nut (11) on the mounting stud (20), wherein the first end of the main nut (11) is opposite to the second end of the main nut (11).

2. The fastening device (10) according to claim 1, characterized in that The fastening device (10) also includes: a gasket (13); The inner side of the washer (13) is provided with an internal thread that mates with the external thread of the mounting stud (20). When the main nut (11) and the washer (13) are mounted on the mounting stud (20), the shank of the plurality of screws (12) extends from the second end of the main nut (11) and abuts against the first end of the washer (13). The second end of the washer (13) abuts against the outer casing (30) of the steam turbine, wherein the first end of the washer (13) is opposite to the second end of the washer (13).

3. The fastening device (10) according to claim 2, characterized in that The outer diameter of the washer (13) is equal to the outer diameter of the main nut (11).

4. The fastening device (10) according to claim 1, characterized in that The through holes are arranged circumferentially along the main nut (11), and the spacing between adjacent through holes is the same.

5. The fastening device (10) according to claim 1, characterized in that The diameters of the shanks of the plurality of screws (12) are equal, and the diameters of the plurality of through holes opened on the main nut (11) are equal.

6. The fastening device (10) according to claim 1, characterized in that The shortest distance between the multiple through holes on the main nut (11) and the outer side of the main nut (11) is greater than 1 cm, and the shortest distance between the through holes and the inner side of the main nut (11) is greater than 1 cm.

7. The fastening device (10) according to claim 2, characterized in that When the shank of the plurality of screws (12) extends from the second end of the main nut (11) and abuts against the first end of the washer (13), the head of the plurality of screws (12) does not contact the first end of the main nut (11).

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