Method for hot stretching of bolts of a motor-driven primary pump of a passive advanced pressurized water reactor reactor coolant shield

Abstract

The application discloses a method for hot stretching of a bolt of a reactor coolant shielding motor main pump of a non-active advanced pressurized water reactor, and the method is suitable for installation and tightening of large full-thread bolts and nuts, can be installed by using the thermal expansion and cold shrinkage characteristics, and is suitable for equipment operating at high temperature; the heating rod of the method can be installed in the bolt, so that the space requirement of the mechanical equipment required for installation equipment is reduced, and the method can be used in a narrow space; the required elongation is divided into two times of hot stretching and one time of balance stretching, the first time of hot stretching can eliminate the influence of the compressible amount between the pump shell and the main pump, the second time of hot stretching is carried out on the bolts according to the stretching law, and the last balance stretching is carried out by the stretching law to stretch the bolts to the position, so that all the bolts can obtain the same stretching amount.

Description

Technical Field

[0001] This invention relates to the field of bolt hot stretching technology, and mainly to a method for hot stretching bolts of main pumps of coolant shielded motors in passive advanced pressurized water reactors. Background Technology

[0002] In some engineering constructions, such as nuclear power plant equipment, the main pump of the reactor coolant shielded motor is the heart of the system, while the pump casing is the fixed, pressure-bearing, and protective shell of the main pump. The two are closely integrated to form an inseparable key piece of equipment.

[0003] In the prior art, the connection of equipment is mainly accomplished by welding and bolts. The main pump and the pump casing require large bolts and nuts, which are mainly fastened or disassembled by hydraulic wrenches or thermal stretching. However, the inventors of this application have found that both of the above methods have some problems in the process of connecting the main pump and the pump casing.

[0004] One of the problems with hydraulic wrenches for tightening or disassembling is that as the bolt size increases, the required torque also increases. It is not possible to find a suitable hydraulic wrench for large bolts and nuts. When applying torque, hydraulic wrenches require a certain amount of space to install the corresponding device.

[0005] One of the problems with hot stretching is that the bolts expand after being heated during the hot stretching process, and their length changes. In order to keep the locking force on the equipment in the circumferential direction consistent, the shortening of the connecting bolts in the equipment needs to be basically consistent. However, due to factors such as the compressibility of the reactor coolant shielded motor main pump and pump casing, the different physical properties of the bolts, and the different stretching sequences, the elongation of each group of bolts will be different after one stretching, and the elongation will be inconsistent due to the heating effect of the surrounding adjacent bolts. Summary of the Invention

[0006] This invention aims to solve at least one problem existing in the prior art. Therefore, the object of this invention is to propose a method for hot-stretching the main pump bolts of the coolant shielding motor in a passive advanced pressurized water reactor.

[0007] To achieve the above objectives, this invention proposes a method for hot-stretching the main pump bolts of the coolant shielded motor in a passive advanced pressurized water reactor, comprising:

[0008] S1. Numbering: Number all bolt holes on the pump casing and all bolts that need to be installed.

[0009] S2. Grouping: Group the numbered bolt holes and the numbered bolts.

[0010] S3. Set the planned elongation. Set a planned elongation of B1. B1 must satisfy the elongation of a single bolt A, and also satisfy the average elongation of all bolts C.

[0011] S4. First hot stretching: Perform the first hot stretching on the bolts according to their group.

[0012] S5. Second hot stretching: Perform a second hot stretching on the bolts according to their group.

[0013] S6. Thermal balance stretching: Perform thermal balance stretching on bolts that do not meet the planned elongation B1 until all bolts meet the planned elongation B1.

[0014] Furthermore, there are 24 bolt holes on the pump casing, numbered 1#-24#; correspondingly, there are also 24 bolts, numbered 1-24.

[0015] Furthermore, bolt holes numbered 1#, 4#, 7#, 10#, 13#, 16#, 19#, and 22# are classified as the first group of bolt holes; bolt holes numbered 2#, 5#, 8#, 11#, 14#, 17#, 20#, and 23# are classified as the second group of bolt holes; and bolt holes numbered 3#, 6#, 9#, 12#, 15#, 18#, 21#, and 24# are classified as the third group of bolt holes. Correspondingly, bolts numbered 1, 4, 7, 10, 13, 16, 19, and 22 are classified as the first group of bolts; bolts numbered 2, 5, 8, 11, 14, 17, 20, and 23 are classified as the second group of bolts; and bolts numbered 3, 6, 9, 12, 15, 18, 21, and 24 are classified as the third group of bolts.

[0016] Furthermore, the specific steps for the first hot stretching in step S4 are as follows:

[0017] S401. The first hot stretching of the third group of bolts: The third group of bolts is installed into the bolt holes of the first group. The nut is pre-installed on the third group of bolts. The third group of bolts is heated using a bolt heater. After heating, the nut E1 is rotated. After cooling, the third group of bolts is measured using a measuring instrument. The elongation of the third group of bolts during the first hot stretching is measured to be B2.

[0018] S402. Weld the first part of the C-type connection surface between the pump casing and the main pump that is not covered by bolts;

[0019] S403. The first thermal stretching of the second group of bolts: The second group of bolts is installed into the bolt holes of the second group of bolts. The nuts are pre-installed on the second group of bolts. The bolt heater is used to heat the second group of bolts. After heating, the nuts E2 are rotated. After cooling, the second group of bolts is measured with a measuring instrument. The elongation of the second group of bolts during the first thermal stretching is measured to be B3.

[0020] S404. The transposition and thermal stretching of the third group of bolts: The third group of bolts is disassembled and installed on the third group of bolt holes. The nut is pre-installed on the third group of bolts. The third group of bolts is heated using a bolt heater. After heating, the nut E3 is rotated. After cooling, the third group of bolts is measured using a measuring instrument. The elongation of the third group of bolts during transposition and thermal stretching is measured to be B4.

[0021] S405. Weld the second part of the C-type connection surface between the pump casing and the main pump that is not covered by bolts;

[0022] S406. First thermal stretching of the first group of bolts: Install the first group of bolts into the first group of bolt holes, pre-install the nuts on the first group of bolts, use a bolt heater to heat the first group of bolts, rotate the nuts E4 after heating, and after cooling, use a measuring instrument to measure the first group of bolts. The elongation of the first group of bolts during the first thermal stretching is measured to be B5.

[0023] Furthermore, the specific steps for the second hot stretching in S5 are as follows:

[0024] S501. Measurement of the elongation of the second and third groups of bolts: The elongation of the second and third groups of bolts is measured using a measuring instrument. The elongation of the second group of bolts is B6 and the elongation of the third group of bolts is B7.

[0025] S502, the second heat stretching of the second group of bolts, the remaining stretch of the second group of bolts is B8=B1-B6, according to the stretching law, the corresponding nut rotation angle is E5, the bolt heater is used to reheat the second group of bolts, and the nut of the second group of bolts is rotated by E5.

[0026] S503. For the second hot stretching of the third group of bolts, after the second hot stretching of the second group of bolts has cooled, the elongation of the third group of bolts is measured to be B9 using a measuring instrument. Therefore, the remaining elongation of the third group of bolts is B. 10 =B1-B9, according to the stretching law, the corresponding nut rotation angle is E6. Use a bolt heater to reheat the third group of bolts and rotate the nut of the third group of bolts by E6.

[0027] S504. After the second hot stretching of the first group of bolts and cooling of the third group of bolts, the elongation of the first group of bolts is measured using a measuring instrument and is determined to be B. 11 Then the remaining tensile strength of the first set of bolts is B. 12 =B1-B 11 Based on the stretching law, the corresponding nut rotation angle is E7. The first group of bolts is reheated using a bolt heater, and the nuts of the first group of bolts are rotated by E7.

[0028] Furthermore, the specific steps in S6 are as follows:

[0029] S601. Remeasure the elongation. After the first group of bolts has cooled following the second hot stretching, remeasure the elongation of each group of bolts using a measuring instrument. The elongation of the first group of bolts is B. 13 The elongation of the second set of bolts is B. 14 The elongation of the third group of bolts is B. 15 ;

[0030] S602. Comparison of elongation with planned elongation, B 13 B 14 B 15 Compare with B1 to see if the elongation meets the requirements of the planned elongation B1;

[0031] S603. Thermal equilibrium stretching: Perform thermal equilibrium stretching on bolts that do not meet the planned elongation requirements, and calculate the remaining elongation of all bolts that do not meet the planned elongation B1. The remaining elongation of the first group of bolts is B. 16 =B1-B 13 Based on the stretching law, the rotation angle of the corresponding nut is E8, and the remaining stretch of the second group of bolts is B. 17= B1-B 14 Based on the stretching law, the rotation angle of the corresponding nut is E9, and the remaining stretch of the third group of bolts is B. 18 =B1-B 15 Based on the stretching principle, the rotation angle of the corresponding nut is E. 10 ;

[0032] S604. For bolts that do not meet the planned elongation B1, use a bolt heater to heat stretch them and rotate them to the corresponding angle. After cooling, use a measuring instrument to measure them again. There is no limit to the number of times the heat balance stretching is performed until the elongation of all bolts reaches the planned elongation B1.

[0033] Furthermore, before the first hot stretching installation of the bolts, a bolt of the same specification is placed in the equipment as a check bolt. The initial length of all bolts and the check bolt is measured once using a measuring instrument. While the bolts are waiting to cool after hot stretching, the check bolt is measured again using the measuring instrument. The two measurements are compared to check the accuracy of the measuring instrument.

[0034] Furthermore, when all bolts are first heat-stretched and installed into the bolt holes, it is necessary to ensure that the length of the bolt extending out of the pump casing flange face meets the extension amount D.

[0035] Furthermore, the stretching law is that for every E rotation of the nut, the bolt's stretch increases by Y.

[0036] Furthermore, the measuring instrument is a flange bolt depth gauge.

[0037] Compared with the prior art, the beneficial effects of the present invention are:

[0038] This method is applicable to the installation and tightening of large fully threaded bolts and nuts. It can utilize the characteristics of thermal expansion and contraction for installation and is suitable for equipment operating at high temperatures.

[0039] This method allows the bolt heater to be installed inside the bolt and uses a thermal stretching method. It can be used to replace hydraulic wrenches with open plates to install and tighten nuts, reducing the space requirements of the mechanical equipment and enabling its use in confined spaces.

[0040] This method divides the required elongation into two hot stretching operations and one balanced stretching operation. The first hot stretching operation can eliminate the influence of the compressibility between the pump casing and the main pump. The second stretching operation is performed by grouping the bolts according to the stretching law. The final balanced stretching operation is performed by stretching the bolts as a whole according to the stretching law, so that all bolts can obtain the same amount of stretching.

[0041] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0042] Figure 1 This is a three-dimensional structural diagram of the main pump and pump casing of the present invention;

[0043] Figure 2 This is a bottom view of the pump casing of the present invention.

[0044] Figure 3 This is a diagram illustrating the requirements for the bolts of this invention;

[0045] Figure 4 Demonstration of the bolt tensioning method of the present invention Figure 1 ;

[0046] Figure 5 Demonstration of the bolt tensioning method of the present invention Figure 2 ;

[0047] Figure 6 Demonstration of the bolt tensioning method of the present invention Figure 3 ;

[0048] Figure 7 Demonstration of the bolt tensioning method of the present invention Figure 4 ;

[0049] Figure 8 Demonstration of the bolt tensioning method of the present invention Figure 5 ;

[0050] Figure 9 Demonstration of the bolt tensioning method of the present invention Figure 6;

[0051] Figure 10 Demonstration of the bolt tensioning method of the present invention Figure 7 ;

[0052] Figure 11 Demonstration of the bolt tensioning method of the present invention Figure 8 ;

[0053] Figure 12 Demonstration of the bolt tensioning method of the present invention Figure 9 ;

[0054] Figure 13 Demonstration of the bolt tensioning method of the present invention Figure 10 ;

[0055] Figure 14 Demonstration of the bolt tensioning method of the present invention Figure 10 one;

[0056] Figure 15 Demonstration of the bolt tensioning method of the present invention Figure 10 two;

[0057] Figure 16 Demonstration of the bolt tensioning method of the present invention Figure 10 three;

[0058] Figure 17 Demonstration of the bolt tensioning method of the present invention Figure 10 Four;

[0059] Figure 18 Demonstration of the bolt tensioning method of the present invention Figure 10 five;

[0060] Figure 19 Demonstration of the bolt tensioning method of the present invention Figure 10 six;

[0061] Figure 20 Demonstration of the bolt tensioning method of the present invention Figure 10 seven;

[0062] Figure 21 Demonstration of the bolt tensioning method of the present invention Figure 10 eight;

[0063] Figure 22 Demonstration of the bolt tensioning method of the present invention Figure 10 Nine;

[0064] Figure 23 Demonstration of the bolt tensioning method of the present invention Figure 2 10 (All bolts satisfy B1).

[0065] In the picture:

[0066] 100. Main pump;

[0067] 200. Pump casing;

[0068] 1. One of the bolts in the first group (or bolt number 1);

[0069] 2. One of the bolts in the second group (or bolt number 2);

[0070] 3. One of the bolts in the third group (or bolt number 3);

[0071] 4. Bolt heater;

[0072] M. First part;

[0073] N. Second part;

[0074] Bolt holes #1-24. Detailed Implementation

[0075] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0076] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses consistent with some aspects of this application as detailed in the appended claims.

[0077] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. Unless otherwise defined, the technical or scientific terms used in this application should be understood in their ordinary sense by one of ordinary skill in the art to which this invention pertains. The words “a” or “one” and similar terms used in this specification and claims do not indicate a limitation of quantity, but rather indicate the presence of at least one. “A plurality” includes two, equivalent to at least two. The words “comprising” or “including” and similar terms mean that the element or object preceding “comprising” or “including” covers the element or object listed following “comprising” or “including” and its equivalents, and does not exclude other elements or objects. The words “connected” or “linked” and similar terms are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect. The singular forms “a,” “the,” and “the” used in this specification and appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0078] like Figure 1-23 As shown, the method for thermally stretching the main pump bolts of the passive advanced pressurized water reactor reactor coolant shielding motor of one or more preferred embodiments of this application will be disclosed and described in the following description.

[0079] A method for hot stretching bolts of the main pump of the reactor coolant shielded motor in a passive advanced pressurized water reactor is applicable to the hot stretching of large equipment and large bolts, such as the connection between the main pump 100 and the pump casing 200 of the reactor coolant shielded motor. This method involves two stages of hot stretching and thermal equilibrium stretching. In the first hot stretching, each bolt receives a certain amount of stretch, which eliminates the influence of the compressibility between the main pump 100 and the pump casing 200. In the second hot stretching, a certain amount of stretch is obtained, and since the influence of compressibility has been eliminated in the first hot stretching, the relationship between the bolt stretch and the nut rotation angle can be derived from the stretching data, i.e., the stretching law: for every nut rotation E, the bolt stretch increases by Y. The remaining stretch after the two stretching stages is calculated based on the planned elongation. Using the stretching law, all main bolts are stretched to their proper positions through thermal equilibrium stretching.

[0080] In this embodiment, the method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor includes the following steps:

[0081] S1. Numbering: Number all bolt holes on the pump casing 200 clockwise, and number all bolts that need to be installed.

[0082] In this embodiment, please refer to the following for details. Figure 2 The pump casing 200 has 24 bolt holes, so the bolt holes are numbered 1#-24#; correspondingly, 24 bolts are required, so the bolts are numbered 1-24, and each bolt is also equipped with a corresponding nut.

[0083] S2. Grouping: Group the numbered bolt holes into three groups. Group the bolt holes numbered 1#, 4#, 7#, 10#, 13#, 16#, 19#, and 22# into the first group; group the bolt holes numbered 2#, 5#, 8#, 11#, 14#, 17#, 20#, and 23# into the second group; and group the bolt holes numbered 3#, 6#, 9#, 12#, 15#, 18#, 21#, and 24# into the third group (bolt holes 3). Similarly, group the numbered bolts into three groups: group the bolts numbered 1, 4, 7, 10, 13, 16, 19, and 22 into the first group (bolt 1); group the bolts numbered 2, 5, 8, 11, 14, 17, 20, and 23 into the second group (bolt 2); and group the bolts numbered 3, 6, 9, 12, 15, 18, 21, and 24 into the third group (bolt 3).

[0084] In this embodiment, the bolt is a hollow M125-1340 bolt (nominal diameter 125mm, bolt length 1340mm) made of ASME SA-540 B23. Based on the bolt and material, the tensile law can be calculated: for every 1° rotation of the nut, the bolt's tensile strength increases by 0.0065mm.

[0085] Method for verifying the tensile law: After the initial hot stretching of the three sets of bolts, ensure that the main pump 100 can be wound gasket is compressed into place. Under the same environment (consistent with the actual hot stretching temperature of the bolts), hot stretch the three sets of bolts again, rotate the nut 160°, and after cooling, measure and calculate the tensile amount of the three sets of bolts. Divide the tensile amount of the three sets of bolts by 160° individually, and take the average of the results to obtain the tensile law. The test can be repeated multiple times to ensure accuracy. The average value of the data from multiple tests can be taken.

[0086] In this embodiment, a 0-360° scale can be made on the circumferential plane of one of the bolts or nuts, and an indicator line can be marked on the other, which makes it easier for the operator to accurately rotate the nut at the correct angle.

[0087] S3. Set the planned elongation amount. Please refer to the following for details. Figure 3 Set a planned elongation of B1, which must satisfy the elongation of a single bolt A, and also satisfy the average elongation of all bolts C.

[0088] In this embodiment, the elongation A of a single bolt is 1.58mm to 1.82mm, and the average elongation C of all bolts is 1.65mm to 1.75mm. Therefore, the planned elongation B1 is 1.65mm to 1.75mm, and the intermediate value of 1.70mm can be selected. In this embodiment, B1 is 1.70mm.

[0089] It should be noted that the tensile amount A of a single bolt and the average tensile amount C of all bolts can be modified according to different production and construction requirements.

[0090] S4. First hot stretching: Perform the first hot stretching on the bolts according to their groups. In this embodiment, taking each group of bolt holes and one bolt hole and one bolt from each group of bolts as an example, the specific steps are as follows:

[0091] For the first thermal stretching of bolt 3 in group S401, please refer to the following: Figure 4-6 Insert the third set of bolts 3 into the first set of bolt holes, ensuring that the length of the bolts extending out of the flange face of the pump housing 200 meets the requirement of D. Pre-install the nut on the third set of bolts 3, making the nut tightly against the lower surface of the main pump 100. Use the bolt heater 4 to heat the third set of bolts 3, causing the third set of bolts 3 to elongate. After heating is complete, rotate the nut E1. After cooling, use a measuring instrument to measure the third set of bolts 3, and measure the elongation of the third set of bolts 3 during the first thermal stretching as B2.

[0092] S402. Weld the first part of the C-shaped connection surface between the pump casing 200 and the main pump 100 that is not covered by bolts. See details for further information. Figure 7 At this point, only the third set of bolts 3 is installed, while the second set of bolts 2 and the third set of bolts 3 are not installed, thus reducing bolt interference. This makes it easier for the welding head to weld the pump casing 200 to the main pump 100 at the first part M.

[0093] For the first thermal stretching of S403 and the second set of bolts 2, please refer to the following: Figure 8-10 Insert the second set of bolts 2 into the second set of bolt holes, ensuring that the length of the bolts extending out of the flange face of the pump housing 200 meets the requirement of D. Pre-install the nut on the second set of bolts 2, making the nut tightly against the lower surface of the main pump 100. Use the bolt heater 4 to heat the second set of bolts 2, and the second set of bolts 2 will elongate. After heating is complete, rotate the nut E2. After cooling, use a measuring instrument to measure the second set of bolts 2. The elongation of the second set of bolts 2 during the first thermal stretch is measured to be B3.

[0094] For the transposition and thermal stretching of S404 and the third group of bolts 3, please refer to the following: Figure 11-13Remove the third set of bolts 3 and install them into the holes of the third set of bolts 3, ensuring that the length of the bolts extending out of the flange face of the pump housing 200 meets the requirement of D. Pre-install the nut on the third set of bolts 3, making the nut close to the lower surface of the main pump 100. Use the bolt heater 4 to heat the third set of bolts 3, and the third set of bolts 3 will elongate. After heating is complete, rotate the nut E3. After cooling, use a measuring instrument to measure the third set of bolts 3. The elongation of the third set of bolts 3 after thermal stretching is measured to be B4.

[0095] S405. Weld the second part N of the C-type connection surface between the pump casing 200 and the main pump 100 that is not covered by bolts. See details for further information. Figure 14 Since the third set of bolts 3 is removed, the second part N in S401, which was covered by the third set of bolts 3, will be exposed, reducing bolt interference. This makes it easier for the welding head to weld the pump housing 200 and the main pump 100 at the second part N. The first part M and the second part N are exactly covered on the C-shaped connection surface of the pump housing 200 and the main pump 100, which can ensure the welding effect.

[0096] For details regarding the first thermal stretching of bolt 1 in group S406, please refer to [link / reference needed]. Figure 15-17 Install the first set of bolts 1 into the first set of bolt holes, ensuring that the length of the bolts extending out of the flange face of the pump housing 200 meets the requirement of D. Pre-install the nut on the first set of bolts 1, making the nut tightly against the lower surface of the main pump 100. Use the bolt heater 4 to heat the first set of bolts 1, and the first set of bolts 1 will elongate. After heating is completed, rotate the nut E4. After cooling, use a measuring instrument to measure the first set of bolts 1. The elongation of the first set of bolts 1 during the first heat stretch is measured to be B5.

[0097] For details, please refer to the following: Figure 18 When all bolts are installed into the bolt holes during the first heat stretching, it is necessary to ensure that the length of the bolt extending 200mm from the flange face of the pump housing meets the extension amount D. In this embodiment, the extension amount D is 1129.6±2.5mm.

[0098] It should be noted that the extension amount D can be modified according to different production and construction requirements.

[0099] It should be noted that the specific rotation angles of E1, E2, E3, and E4 can be adjusted according to the experience of those skilled in the art. In short, the nut should be able to initially fit tightly against the lower surface of the main pump 100.

[0100] S5. Second Hot Stretching: The bolts are subjected to a second hot stretching according to their group. This second hot stretching is based on the first hot stretching. Since the hot stretching of the bolts will affect the elongation of adjacent bolts, it is necessary to remeasure the bolts adjacent to the first bolt after the hot stretching. The specific steps are as follows:

[0101] S501, the measurement of the elongation of the second group of bolts 2 and the third group of bolts 3. In S4, the last step is the thermal stretching of the first group of bolts 1. Therefore, it is necessary to use a measuring instrument to measure the elongation of the second group of bolts 2 and the third group of bolts 3. The measured elongation of the second group of bolts 2 is B6, and the elongation of the third group of bolts 3 is B7.

[0102] For details regarding the second thermal stretching of bolts S502 and the second set of bolts 2, please refer to [link / reference needed]. Figure 19-22 The remaining tension of the second set of bolts 2 is B8 = B1 - B6. According to the tension law, the corresponding nut rotation angle is E5. The bolt heater 4 is used to reheat the second set of bolts 2 and rotate the nut of the second set of bolts 2 by E5.

[0103] S503, the second hot stretching of the third group of bolts 3: After the second hot stretching of the second group of bolts 2 has cooled, the elongation of the third group of bolts 3 is measured to be B9 using a measuring instrument. Therefore, the remaining elongation of the third group of bolts 3 is B. 10 =B1-B9, according to the stretching law, the corresponding nut rotation angle is E6. The bolt heater 4 is used to reheat the third group of bolts 3, and the nut of the third group of bolts 3 is rotated by E6.

[0104] S504. After the second hot stretching of bolt 1 in the first group and cooling of bolt 3 in the third group, the elongation of bolt 1 in the first group is measured using a measuring instrument and is B. 11 Then the remaining tensile strength of the first bolt 1 is B. 12 =B1-B 11 According to the stretching law, the corresponding nut rotation angle is E7. The bolt heater 4 is used to reheat the first group of bolts 1 and rotate the nut of the first group of bolts 1 by E7.

[0105] S6. Thermal equilibrium stretching: After the second thermal stretching, some bolts may not meet the elongation requirements of the second thermal stretching. For bolts that do not meet the planned elongation B1, thermal equilibrium stretching is performed until all bolts meet the planned elongation B1. The specific steps are as follows:

[0106] S601. Remeasure the elongation. After the first group of bolts 1 has cooled following the second hot stretching, remeasure the elongation of each group of bolts using a measuring instrument. The elongation of the first group of bolts 1 is B. 13 The elongation of the second bolt 2 is B. 14 The elongation of bolt 3 in the third group is B. 15 ;

[0107] S602. Comparison of elongation with planned elongation, i.e., B 13 B 14 B15 Compare with B1 to see if the elongation meets the requirements of the planned elongation B1;

[0108] S603. Thermal equilibrium stretching: Perform thermal equilibrium stretching on bolts that do not meet the planned elongation requirement, and calculate the remaining elongation of all bolts that do not meet the planned elongation B1. For example, if bolt 1 in the first group does not meet the planned elongation B1, then the remaining elongation of bolt 1 in the first group is B. 16 =B1-B 13 Based on the stretching law, the corresponding rotation angle of the nut is E8. For example, if the second bolt 2 does not meet the planned elongation B1, then the remaining elongation of the second bolt 2 is B. 17= B1-B 14 Based on the stretching law, the corresponding rotation angle of the nut is E9. For example, if the third bolt 3 does not meet the planned elongation B1, then the remaining stretch of the third bolt 3 is B. 18 =B1-B 15 Based on the stretching principle, the rotation angle of the corresponding nut is E. 10 .

[0109] S604. For bolts that do not meet the planned elongation B1, use bolt heater 4 for hot stretching and rotate them at the corresponding angle. After cooling, remeasure using a measuring instrument. There is no limit to the number of times the hot stretching is performed until the elongation of all bolts reaches the planned elongation B1. See details for further information. Figure 23 .

[0110] It should be noted that this application does not show a demonstration diagram of the second thermal stretching and thermal equilibrium stretching of the remaining bolts.

[0111] Assume that after the second hot tensile test and cooling of bolt No. 1 in the first group of bolts 1, the B value of bolt No. 2 in the second group of bolts 2 during the second hot tensile test is measured. 14 The remaining tensile strength of bolt #2 in the second group of bolts 2 is 1.635mm, which is less than the 1.70mm of bolt B1. 17= B1-B 14 The difference is 1.70mm - 1.635mm = 0.05mm. Therefore, the nut corresponding to bolt number 2 in the second group of bolts 2 needs to be rotated by an angle E9 = B. 17 / 0.0065=10°, which means that bolt number 2 in the second group of bolts 2 needs to be tightened by 10°.

[0112] To ensure the accuracy of the measuring instrument, it needs to be calibrated. Before the first hot-stretch installation of the bolts, a bolt of the same specification is placed inside the equipment (passive advanced pressurized water reactor coolant shielded motor) as a calibration bolt. The initial length of all bolts and the calibration bolt is measured once using the measuring instrument. Under the condition of the same specification, the initial length of all bolts and the calibration bolt should be consistent. As time changes and affected by environmental factors, the measuring instrument may make false calls. Therefore, while the bolts are waiting for cooling after hot stretching, the calibration bolt is measured again using the measuring instrument. The two measurements are compared to check the accuracy of the measuring instrument. If the difference between the two measurements reaches a certain threshold (this threshold can be set according to the actual situation), it indicates that there is a problem with the measuring instrument, and the measuring instrument needs to be replaced and the measurement repeated.

[0113] In this embodiment, the measuring instrument is a flange bolt depth gauge, which can be inserted into the hollow cavity of the bolt to measure its length, and the measurements are all performed after the bolt has been heated and cooled.

[0114] In this embodiment, the bolt heater 4 is an electric heating rod. The heating temperature of all bolts (including mounting bolts, check bolts and test bolts) is between 350℃ and 400℃, specifically 380℃. It can be changed according to the actual situation, as long as the heating temperature of all bolts (including mounting bolts, check bolts and test bolts) is the same and within the heating temperature range.

[0115] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for hot-stretching the main pump bolts of the coolant shielded motor in a passive advanced pressurized water reactor, characterized in that... Including the following steps: S1. Numbering: Number all bolt holes on the pump casing and all bolts that need to be installed. S2. Grouping: Group the numbered bolt holes and the numbered bolts. S3. Set the planned elongation. Set a planned elongation of B1. B1 must satisfy the elongation of a single bolt A, and also satisfy the average elongation of all bolts C. S4. First hot stretching: Perform the first hot stretching on the bolts according to their group. S5. Second hot stretching: Perform a second hot stretching on the bolts according to their group. S6. Thermal balance stretching: Perform thermal balance stretching on bolts that do not meet the planned elongation B1 until all bolts meet the planned elongation B1. There are 24 bolt holes on the pump casing, so the bolt holes are numbered 1#-24#; correspondingly, there are also 24 bolts, so the bolts are numbered 1-24; Bolt holes numbered 1#, 4#, 7#, 10#, 13#, 16#, 19#, and 22# are classified as the first group of bolt holes; bolt holes numbered 2#, 5#, 8#, 11#, 14#, 17#, 20#, and 23# are classified as the second group of bolt holes; and bolt holes numbered 3#, 6#, 9#, 12#, 15#, 18#, 21#, and 24# are classified as the third group of bolt holes. Correspondingly, bolts numbered 1, 4, 7, 10, 13, 16, 19, and 22 are classified as the first group of bolts; bolts numbered 2, 5, 8, 11, 14, 17, 20, and 23 are classified as the second group of bolts; and bolts numbered 3, 6, 9, 12, 15, 18, 21, and 24 are classified as the third group of bolts. The specific steps for the first hot stretching in step S4 are as follows: S401. The first hot stretching of the third group of bolts: The third group of bolts is installed into the bolt holes of the first group. The nut is pre-installed on the third group of bolts. The third group of bolts is heated using a bolt heater. After heating, the nut E1 is rotated. After cooling, the third group of bolts is measured using a measuring instrument. The elongation of the third group of bolts during the first hot stretching is measured to be B2. S402. Weld the first part of the C-type connection surface between the pump casing and the main pump that is not covered by bolts; S403. The first thermal stretching of the second group of bolts: The second group of bolts is installed into the bolt holes of the second group of bolts. The nuts are pre-installed on the second group of bolts. The bolt heater is used to heat the second group of bolts. After heating, the nuts E2 are rotated. After cooling, the second group of bolts is measured with a measuring instrument. The elongation of the second group of bolts during the first thermal stretching is measured to be B3. S404. The transposition and thermal stretching of the third group of bolts: The third group of bolts is disassembled and installed on the third group of bolt holes. The nut is pre-installed on the third group of bolts. The third group of bolts is heated using a bolt heater. After heating, the nut E3 is rotated. After cooling, the third group of bolts is measured using a measuring instrument. The elongation of the third group of bolts during transposition and thermal stretching is measured to be B4. S405. Weld the second part of the C-type connection surface between the pump casing and the main pump that is not covered by bolts; S406. First thermal stretching of the first group of bolts: Install the first group of bolts into the first group of bolt holes, pre-install the nuts on the first group of bolts, use a bolt heater to heat the first group of bolts, rotate the nuts E4 after heating, and after cooling, use a measuring instrument to measure the first group of bolts. The elongation of the first group of bolts during the first thermal stretching is measured to be B5.

2. The method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor according to claim 1, characterized in that, The specific steps for the second hot stretching in S5 are as follows: S501. Measurement of the elongation of the second and third groups of bolts: The elongation of the second and third groups of bolts is measured using a measuring instrument. The elongation of the second group of bolts is B6 and the elongation of the third group of bolts is B7. S502, the second heat stretching of the second group of bolts, the remaining stretch of the second group of bolts is B8=B1-B6, according to the stretching law, the corresponding nut rotation angle is E5, the bolt heater is used to reheat the second group of bolts, and the nut of the second group of bolts is rotated by E5. S503. For the second hot stretching of the third group of bolts, after the second hot stretching of the second group of bolts has cooled, the elongation of the third group of bolts is measured to be B9 using a measuring instrument. Therefore, the remaining elongation of the third group of bolts is B. 10 =B1-B9, according to the stretching law, the corresponding nut rotation angle is E6. Use a bolt heater to reheat the third group of bolts and rotate the nut of the third group of bolts by E6. S504. After the second hot stretching of the first group of bolts and cooling of the third group of bolts, the elongation of the first group of bolts is measured using a measuring instrument and is determined to be B. 11 Then the remaining tensile strength of the first set of bolts is B. 12 =B1-B 11 Based on the stretching law, the corresponding nut rotation angle is E7. The first group of bolts is reheated using a bolt heater, and the nuts of the first group of bolts are rotated by E7.

3. The method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor according to claim 2, characterized in that, The specific steps in S6 are as follows: S601. Remeasure the elongation. After the first group of bolts has cooled following the second hot stretching, remeasure the elongation of each group of bolts using a measuring instrument. The elongation of the first group of bolts is B. 13 The elongation of the second set of bolts is B. 14 The elongation of the third group of bolts is B. 15 ; S602. Comparison of elongation with planned elongation, B 13 B 14 B 15 Compare with B1 to see if the elongation meets the requirements of the planned elongation B1; S603. Thermal equilibrium stretching: Perform thermal equilibrium stretching on bolts that do not meet the planned elongation requirements, and calculate the remaining elongation of all bolts that do not meet the planned elongation B1. The remaining elongation of the first group of bolts is B. 16 =B1-B 13 Based on the stretching law, the rotation angle of the corresponding nut is E8, and the remaining stretch of the second group of bolts is B. 17 =B1-B 14 Based on the stretching law, the rotation angle of the corresponding nut is E9, and the remaining stretch of the third group of bolts is B. 18 =B1-B 15 Based on the stretching principle, the rotation angle of the corresponding nut is E. 10 ; S604. For bolts that do not meet the planned elongation B1, use a bolt heater to heat stretch them and rotate them to the corresponding angle. After cooling, use a measuring instrument to measure them again. There is no limit to the number of times the heat balance stretching is performed until the elongation of all bolts reaches the planned elongation B1.

4. The method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor according to claim 1, characterized in that, Before the first hot stretching installation of the bolts, a bolt of the same specification is placed in the equipment as a check bolt. The initial length of all bolts and the check bolt is measured once using a measuring instrument. While the bolts are waiting to cool after hot stretching, the check bolt is measured again using the measuring instrument. The two measurements are compared to check the accuracy of the measuring instrument.

5. The method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor according to claim 1, characterized in that, When all bolts are first heat-stretched and installed into the bolt holes, it is necessary to ensure that the length of the bolt extending out of the pump casing flange face meets the extension amount D.

6. The method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor according to claim 4, characterized in that, The stretching law is that for every E rotation of the nut, the bolt's stretch increases by Y.

7. The method for hot-stretching the main pump bolts of the passive advanced pressurized water reactor coolant shielding motor according to claim 1, characterized in that, The measuring instrument is a flange bolt depth gauge.

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