Locking type sawtooth threaded sleeve of pressure vessel and machining method

Abstract

The invention relates to a pressure vessel locking type sawtooth threaded sleeve and a machining method, mainly aims at solving the problem of installation of a large overweight and ultrahigh pressure device connecting piece, and particularly designs a three-petal bolt pair connection 3-degree / 45-degree sawtooth thread stress threaded sleeve, threads are arranged at the two ends of the threaded sleeve, one end of the threaded sleeve is positively buckled, the other end of the threaded sleeve is reversely buckled, and stress surfaces are opposite to each other. The threaded sleeve has the advantages that the threaded sleeve can be mounted and dismounted in a sectioning manner, looseness of the threaded sleeve can be prevented by pressing each sectioning bolt pair for connection, the threaded sleeve can be machined by a vertical lathe, a flat plate needs to be cushioned in the middle after sectioning during machining, workpiece machining precision is guaranteed, and the threaded sleeve is not easy to break and easy to machine.

Description

Technical Field

[0001] This invention belongs to the field of mechanical manufacturing technology and relates to a pressure vessel locking sawtooth thread sleeve and its machining method. Background Technology

[0002] my country is currently vigorously developing high-precision ultra-high pressure devices to advance various experiments, such as deep-earth simulation, deep-sea simulation, and flight simulation. Because these devices operate at pressures exceeding 100 MPa and have inner diameters exceeding 200 mm, the components are quite heavy. Therefore, the sealing connections require a type of connector that is easy to disassemble, can withstand significant stress, and is not prone to loosening to ensure the stable operation of the ultra-high pressure device. This necessitates the design of a suitable threaded sleeve that is easy to disassemble, can withstand significant stress, is not prone to loosening, and is easy to manufacture. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pressure vessel locking sawtooth threaded sleeve that is easy to disassemble, can withstand great pressure, and is not easy to loosen, as well as a machining method thereof, and the threaded sleeve is easy to process.

[0004] The objective of this invention is achieved as follows: A pressure vessel locking sawtooth threaded sleeve includes a threaded sleeve circumferentially divided into three segments, each segment with a 10mm gap. Each segment is connected by at least four bolt pairs. The segmented threaded sleeve is assembled or disassembled onto a mating cylinder and end plug separately. After the threaded sleeve is assembled with the cylinder and end plug, the connecting bolt pairs are tightened to press each segment of the threaded sleeve firmly against the mating cylinder and end plug, increasing the pressure on the threaded surface and preventing the threaded sleeve from loosening with the cylinder and end plug. The threads connecting each threaded sleeve are standard 3° and 45° sawtooth threads with a 3° angle on the force-bearing surface. This type of thread can withstand greater force and also plays an efficient transmission role, which is conducive to tightening and loosening the threaded sleeve. The threads at both ends of the threaded sleeve connecting each threaded sleeve are reversed at one end and opposite at the other end, and the force-bearing surfaces are opposite to each other, so as to ensure that rotating the threaded sleeve can achieve the tightening and separation of the cylinder and the end plug. A threaded hole for hoisting is machined in the middle of the circumferential end face of each threaded sleeve.

[0005] A machining method for a pressure vessel locking sawtooth thread sleeve, the specific machining method is as follows: Step 1) Determining the size of the threaded sleeve: Based on the internal pressure of the ultra-high pressure device, the pressure-bearing diameter, and the required outer diameter of the thread on the sleeve, which matches the thread of the threaded sleeve, determine the size of the threaded sleeve according to the relevant force formulas for threaded sleeves in section D.3.9 of GB / T34019-2017 and the bolt pair installation requirements. Step 2) Determining the dimensions of the bolt assembly: Calculate the minimum bolt diameter using the following formula. In the formula, n represents the number of bolt pairs used per segment of the threaded sleeve (4). Let W be the allowable stress of the bolt material at the design temperature, and W be the resultant force on the four bolt pairs. The calculation is based on Table 2 of GB / T150.1-2024 (which needs to be listed in the examples), and the resultant force W is calculated according to the following formula: In the formula , The dimensions are the major diameter of the sawtooth thread on the threaded sleeve and the dimensions of the relief groove in the sawtooth thread on the threaded sleeve. , , , The coefficient is obtained during the calculation of the threaded sleeve size, and is calculated according to formula D.99 in GB / T34019-2017 to determine the minimum bolt diameter. Then, select the tooth base diameter ratio For thread types with a diameter 0.5-2mm larger, add 2mm to the outer diameter of the selected thread type to determine the inner diameter of the bolt hole for the threaded sleeve. At the same time, select the nut size according to the thread type and GB / T41-2000, and finally determine the overall size of the threaded sleeve.

[0006] Step 3) Machining: Semi-finish machining of the tempered blank using a vertical lathe, and ultrasonic testing of the machined blank according to NB / T47013.3-2023 standard, achieving a grade I qualification. The workpiece is then sawn into three circumferential segments using a sawing machine. Each segment's rough surface is milled off using a gantry milling machine with a 10mm gap width. Considering the machining allowance for the inner and outer diameters, bolt holes are drilled and reamed using a gantry milling machine according to the finishing drawing requirements. A 10mm thick plate is placed in the gap, and the three segments are tightly connected using bolt sets. The connected three-segment threaded sleeve blank is then machined into a threaded sleeve according to the finished dimensions using a vertical lathe. The bolts and nuts are removed, and the threaded surface is polished using a hand-held polishing machine with a polishing disc, ensuring a surface roughness of Ra1.6. Finally, the three-segment threaded sleeve is reconnected using brand-new bolts and nuts and is ready for use.

[0007] The present invention has the following positive effects: the segmented threaded sleeve designed in this invention can be installed and disassembled in segments, and the threaded sleeve can be prevented from loosening by tightening the bolt pairs connecting each segment. The threaded sleeve designed and manufactured in this way solves the installation problem of large and heavy threaded connections such as cylinders and end caps of pressure vessels, and the processing and manufacturing of this type of threaded sleeve can be realized. Attached Figure Description

[0008] Figure 1 This is a front view of the threaded sleeve of the present invention.

[0009] Figure 2 This is a schematic diagram of the left or right view of the threaded sleeve of the present invention. The left and right views of this threaded sleeve are identical.

[0010] Figure 3 This is a K-direction view of the present invention, showing the dimensions of the bolt and nut mounting hole.

[0011] Figure 4 This is an enlarged schematic diagram of the sawtooth thread on the threaded sleeve of the present invention.

[0012] Figure 5 This is a schematic diagram of the assembly of the threaded sleeve, cylinder, and end plug of the present invention.

[0013] 1 is the cylinder body, 2 is the threaded sleeve, 3 is the end plug, 4 is the sealing ring, 5 is the bolt pair, which consists of a standard double-headed bolt and a matching nut, and 6 is the threaded hole. Detailed Implementation

[0014] like Figure 1 , 2 As shown in Figures 3 and 4, a pressure vessel locking sawtooth threaded sleeve includes a threaded sleeve 2. The threaded sleeve 2 is circumferentially divided into three segments, with a 10mm gap between each segment. Each segment is connected by at least four bolt pairs 5. The segmented threaded sleeve can be assembled or disassembled onto the mated cylinder 1 and end plug 3. After the threaded sleeve 2 is assembled with the cylinder 1 and end plug 3, the bolt pairs 5 for connection are tightened. The bolt pairs are standard double-headed bolts and matching nuts. The purpose of this design is that the threaded sleeve 2 can be assembled onto the mated cylinder 1 and end plug 3 in segments, or it can be disassembled in segments.

[0015] Each segment of the threaded sleeve is pressed tightly against the mating cylinder 1 and end plug 3 to increase the pressure on the threaded surface and prevent the threaded sleeve 2 from loosening with the cylinder 1 and end plug 3. The threads connecting each segment of the threaded sleeve are standard 3° and 45° sawtooth threads with a 3° angle on the force-bearing surface. This type of thread can withstand greater force and also plays an efficient transmission role, which is conducive to tightening and loosening the threaded sleeve. The threads at both ends of the threaded sleeve connecting each segment are reversed at one end and opposite at the other, with the force-bearing surfaces facing each other, ensuring that rotating the threaded sleeve can achieve the tightening and separation of the cylinder and end plug. A threaded hole 6 for lifting is machined at the middle position of the circumferential end face of each segment of the threaded sleeve, as detailed in the appendix. Figure 2 .

[0016] There is a 10mm gap between each segment of the threaded sleeve. The purpose of this design is to ensure that after the threaded sleeve is assembled with the cylinder and end plug, the connecting bolt pair is tightened again to press each segment of the threaded sleeve onto the cylinder 1 and end plug 3 that it mates with, thereby increasing the pressure on the threaded surface and effectively preventing the threaded sleeve 2 from loosening with the cylinder 1 and end plug 3.

[0017] The thread of threaded sleeve 2 is a standard 3° / 45° sawtooth thread with a 3° angle on the force-bearing surface (see details). Figure 4 This type of thread can withstand greater forces and also plays an efficient transmission role, making it easy to tighten and loosen the threaded sleeve.

[0018] The threaded sleeve 2 has threads at both ends, one end with a positive thread and the other end with a negative thread, and the force-bearing surfaces are opposite each other. See details. Figure 1 , Figure 4 The purpose of this design is that by rotating the threaded sleeve, the cylinder and the end plug can be tightened and separated.

[0019] Each segment of the threaded sleeve 2 has a threaded hole 6 machined at the center of its circumferential end face for lifting. For details on the specific machining location of the lifting threaded holes, please refer to [link to details]. Figure 2 .

[0020] A machining method for a pressure vessel locking sawtooth thread sleeve, the specific machining method is as follows: Step 1) Determining the size of the threaded sleeve: Based on the internal pressure of the ultra-high pressure device, the pressure-bearing diameter... (See details) Figure 5 The dimensions of the threaded sleeve are determined based on the relevant force formulas for threaded sleeves in section D.3.9 of GB / T34019-2017 and the bolt pair installation requirements. Step 2) Determining the dimensions of the bolt assembly: Calculate the minimum bolt diameter using the following formula. In the formula, n represents the number of bolt pairs used per segment of the threaded sleeve (4). Let W be the allowable stress of the bolt material at the design temperature, and W be the resultant force on the four bolt pairs. The calculation is based on Table 2 of GB / T150.1-2024, and the resultant force W is calculated using the following formula: In the formula , The dimensions are the major diameter of the sawtooth thread on the threaded sleeve and the relief groove size of the sawtooth thread on the threaded sleeve, see details. Figure 4 As shown, , , , The coefficient is obtained during the calculation of the threaded sleeve size, and is calculated according to formula D.99 in GB / T34019-2017 to determine the minimum bolt diameter. Then, select the tooth base diameter ratio For thread types with a diameter 0.5-2mm larger, determine the inner diameter of the threaded sleeve bolt hole by adding 2mm to the outer diameter of the selected thread type; at the same time, select the nut size according to the thread type and GB / T41-2000, and finally determine the overall size of the threaded sleeve. Step 3) Machining method is as follows: ① First, use a vertical lathe to turn the end face, outer circle, and inner hole of the tempered blank, ensuring that the outer circle and length dimensions are 10mm larger than the precision machining dimensions, and the inner hole is 10mm smaller than the precision machining dimensions; ② Perform ultrasonic testing on the turned blank according to NB / T47013.3-2023 standard, with a pass level of I, to ensure that the workpiece is free of internal defects; ③ Use a saw to cut the workpiece into three evenly circumferential sections, and use a gantry milling machine to mill away the rough surface of each saw cut surface with a 10mm gap width; ④ Considering the machining allowance for the inner and outer circles, use a gantry milling machine to drill and ream bolt holes according to the precision machining drawing requirements; ⑤ Make a workpiece with the same dimensions as the bolt holes, and with the same position as the milled surface at the gap. Place three 10mm thick flat plates with four small holes of equal diameter; place the three plates in the three gaps, and then use bolts to tightly connect the three segments; ⑥ On the connected three-segment threaded sleeve blank, turn one end face flat on a vertical lathe, turn the outer circle and inner hole (including the relief groove) to the finished size, and turn the other end face to ensure that the total length is consistent with the finished product. Then, use a threading tool with a 1:1 ratio to the gap between the sawtooth threads to turn the threads at both ends according to the finished size; ⑦ Remove the bolts and nuts, use a hand-held polisher with a polishing disc to polish the thread surface to ensure that the thread surface roughness reaches Ra1.6; ⑧ After connecting the three-segment threaded sleeve with brand new bolts and nuts, it can be put into use.

[0021] Example: The design and machining of the threaded sleeve of an ultra-high pressure reactor made of 36CrNi3MoVR steel with a design pressure of 150MPa, a design temperature of 200℃, a pressure inner diameter of 400mm, and an outer diameter of 600mm for the cylindrical thread is as follows.

[0022] The specific processing steps are as follows: Step 1) The threaded sleeve is divided into 3 segments circumferentially, and each segment is connected by a bolt pair. The purpose of this design is that the threaded sleeve can be assembled into the pre-connected cylinder or end plug in segments, or it can be disassembled in segments. Step 2) Select a standard 3° / 45° sawtooth thread with an angled force-bearing surface for the threaded sleeve. This type of thread can withstand greater force and also play an efficient transmission role, which is conducive to tightening and loosening the threaded sleeve. Step 3) The threaded sleeve has threads at both ends, one end is a positive thread and the other end is a negative thread. The purpose of this design is that by rotating the threaded sleeve, the cylinder and the end plug can be tightened and separated. Step 4) There is a 10mm gap between each piece of the threaded sleeve. The purpose of this is to ensure that after the threaded sleeve is assembled with the cylinder and end plug, the connecting bolt pair is tightened again to press each piece of the threaded sleeve onto the cylinder and end plug that it mates with, increasing the pressure on the threaded surface and effectively preventing the threaded sleeve, cylinder and end plug from loosening. Step 5) A lifting hole is machined at the middle position of the two circumferential end faces of each segment of the threaded sleeve for lifting the threaded sleeve. The dimensions of the lifting hole and the matching lifting eye are determined according to GB / T825-1988 standard: Based on the outer diameter of the threaded sleeve of 730mm, the minor diameter of the internal thread of 580mm, and the total length of 496mm, the weight of each segment of the threaded sleeve is initially calculated to be 200Kg. According to GB / T825-1988 standard, an M12 lifting eye screw is selected, and an M12 lifting hole is machined. Step 6) Determining the threaded sleeve size: Based on the design pressure of 150MPa, and the yield strength of 36CrNi3MoVR material at 200℃ according to GB / T34019-2017 standard. The pressure is ≥783MPa. The pressure-bearing diameter of the ultra-high pressure device is Φ400mm, and the major diameter Do of the sawtooth thread is 600mm. Based on the stress analysis and the relevant formulas for threaded sleeves in section D.3.9 of GB / T34019-2017, it was confirmed that L must be greater than or equal to 8F, and (D-Do) / 2 must be greater than or equal to F. Through multiple trials, the outer diameter D of the threaded sleeve was found to be 730mm, and the length L was 496. The sawtooth thread pitch is 20mm, and the thread height h is 10mm. The length is 40mm. Preliminary calculations show that the bolt thread is M24×2, and the nut diagonal is 42mm, so F is taken as 62mm. R is equal to half of F, which is 31mm; B is equal to L / 4, which is 145.5mm; 2F is equal to 124mm, so B is greater than 2F; C is equal to 1.5F, which is 93mm. At this point, 8F is 496, satisfying the requirement that L is greater than or equal to 8F; the bolt hole diameter d is equal to the selected thread outer diameter plus 2mm, so 26mm is selected. E is directly taken as 50mm; again, according to the relevant formulas for threaded sleeves in section D.3.9 of GB / T34019-2017 standard, the stress analysis is checked and the requirements are met; at this point... It equals 0.009786. Because each segment is connected by four bolts, and the bolt material is the same as the threaded sleeve (36CrNi3MoVR), the yield strength of 36CrNi3MoVR material at 200℃ is specified in GB / T34019-2017 standard. ≥783MPa, belonging to martensitic high alloy steel. The calculations are based on Table 2 of GB / T150.1-2024. Therefore, the minimum diameter of the bolt Because of the selection of tooth base diameter ratio For thread sizes 0.5-2mm larger, the root diameter of the M24×2 thread is 21.835mm, and the bolt secondary thread selection meets the requirements; Step 7) Machining: ① First, use a vertical lathe to turn the end face, outer diameter, and inner hole of the tempered blank, ensuring that the outer diameter and length dimensions are 10mm larger than the precision machining dimensions, and the inner hole is 10mm smaller than the precision machining dimensions; ② Perform ultrasonic testing on the turned blank according to NB / T47013.3-2023 standard, with a pass level of I, ensuring that the workpiece is free of internal defects; ③ Use a saw to cut the workpiece into three evenly circumferential sections, and use a gantry milling machine to mill away the rough surface of each section with a 10mm gap width; ④ Considering the machining allowance for the inner and outer diameters, use a gantry milling machine to drill and ream bolt holes according to the precision machining drawing requirements; ⑤ Make four small holes of the same size and diameter as the bolt holes, with the same position and diameter as the milled surface at the gap. Three 10mm thick flat plates are used to fill the hole. The dimensions of the flat plates are specified. The three flat plates are placed in the three gaps, and then the three segments are tightly connected with bolts. The connected three-segment threaded sleeve is then machined flat on one end face with a lathe. The outer circle and inner hole (including the relief groove) are machined to the finished size. The other end face is machined to ensure that the total length is consistent with the finished product. Then, a threading tool is ground with a 1:1 ratio between the tooth gaps of the 20mm pitch sawtooth thread, and the threads at both ends are machined according to the finished size. The bolts and nuts are removed, and the thread surface is polished with a hand-held polishing machine and polishing discs to ensure that the thread surface roughness reaches Ra1.6. After connecting the three-segment threaded sleeve with brand new bolts and nuts, it can be put into use.

[0023] By following the above requirements, without using external cylindrical grinding equipment, the tube body with high precision requirements on the outer diameter was successfully machined on a CNC lathe.

[0024] The threaded sleeve was applied to an ultra-high pressure reactor made of 36CrNi3MoVR steel with a design pressure of 150MPa, a design temperature of 200℃, a pressure-bearing inner diameter of 400mm, and an outer diameter of 600mm for the cylinder thread. After a pressure test, the threaded sleeve showed no abnormalities and was easy to disassemble, thus meeting the requirements.

[0025] This type of threaded sleeve is typically assembled together with the sleeve body and end plug. See details. Figure 5 .

Claims

1. A pressure vessel locking sawtooth threaded sleeve, comprising a threaded sleeve, characterized in that: The threaded sleeve is circumferentially divided into three segments, with a 10mm gap between each segment. Each segment is connected by at least four bolt pairs. The segmented threaded sleeve is assembled or disassembled onto the mating cylinder and end plug separately. After the threaded sleeve is assembled with the cylinder and end plug, the connecting bolt pairs are tightened to press each segment of the threaded sleeve onto the mating cylinder and end plug, increasing the pressure on the threaded surface and preventing the threaded sleeve from loosening. The threads between each segment of the threaded sleeve are standard 3° and 45° sawtooth threads with a 3° angle on the force-bearing surface. This type of thread can withstand greater force and also provides efficient transmission, facilitating the tightening and loosening of the threaded sleeve. The threads at both ends of the threaded sleeve mating are reversed at one end and opposite at the other, with the force-bearing surfaces facing each other, ensuring that rotating the threaded sleeve achieves the tightening and separation of the cylinder and end plug. A threaded hole for lifting is machined at the middle of the circumferential end face of each segment of the threaded sleeve.

2. A machining method for a pressure vessel locking sawtooth thread sleeve, characterized in that: The specific processing method is as follows: Step 1) Determining the size of the threaded sleeve: Based on the internal pressure of the ultra-high pressure device, the pressure-bearing diameter, and the required outer diameter of the thread on the cylinder, which is consistent with the thread of the threaded sleeve, the size of the threaded sleeve is determined according to the relevant force formula of the threaded sleeve in Chapter D.3.9 of GB / T34019-2017 standard and the bolt pair installation requirements. Step 2) Determining the dimensions of the bolt assembly: Calculate the minimum bolt diameter using the following formula. In the formula, n represents the number of bolt pairs used per segment of the threaded sleeve (4). Let W be the allowable stress of the bolt material at the design temperature, and W be the resultant force on the four bolt pairs. The calculation is based on Table 2 of GB / T150.1-2024, and the resultant force W is calculated using the following formula: In the formula , The dimensions are the major diameter of the sawtooth thread on the threaded sleeve and the size of the relief groove in the sawtooth thread on the threaded sleeve. , , , The coefficient is obtained during the calculation of the threaded sleeve size, and is calculated according to formula D.99 in GB / T34019-2017 to determine the minimum bolt diameter. Then, select the tooth base diameter ratio For thread types with a diameter 0.5-2mm larger, add 2mm to the outer diameter of the selected thread type to determine the inner diameter of the bolt hole for the threaded sleeve. At the same time, select the nut size according to the thread type and GB / T41-2000, and finally determine the overall size of the threaded sleeve. Step 3) Machining: Semi-finish machining of the tempered blank using a vertical lathe, and ultrasonic testing of the machined blank according to NB / T47013.3-2023 standard, achieving a grade I qualification. The workpiece is then sawn into three circumferential segments using a sawing machine. Each segment's rough surface is milled off using a gantry milling machine with a 10mm gap width. Considering the machining allowance for the inner and outer diameters, bolt holes are drilled and reamed using a gantry milling machine according to the finishing drawing requirements. A 10mm thick plate is placed in the gap, and the three segments are tightly connected using bolt sets. The connected three-segment threaded sleeve blank is then machined into a threaded sleeve according to the finished dimensions using a vertical lathe. The bolts and nuts are removed, and the threaded surface is polished using a hand-held polishing machine with a polishing disc, ensuring a surface roughness of Ra1.

6. Finally, the three-segment threaded sleeve is reconnected using brand-new bolts and nuts and is ready for use.

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