High-pressure main throttle valve bolt buckling and disassembling method

Abstract

The invention discloses a high-pressure main throttle valve bolt meshing and buckling dismounting method. When an oxide film is pulled broken, burrs are pulled out on the surface of a thread, the thread is seized, disassembly is difficult, and the phenomenon of bolt breakage is found in the overhaul process. The method comprises the following steps that a screw is cut off at the position 10 mm away from the joint face of a main throttle valve shell and a control valve shell through a portable cutting machine, two bolts are reserved at the symmetrical positions, and a special blocking plate is machined; a special blocking plate is additionally installed on the door body and tightened through a nut, a magnetic drill is attracted to the blocking plate, and after centering is conducted, a drill bit with the inner diameter smaller than that of a bolt by about 10 mm is adopted for drilling a hole; two symmetrical screw holes after the bolts are removed are found, the replacement bolts are inserted after tapping, the special blocking plate is arranged on the door body again, and the remaining two bolts are taken according to the method; after the bolt is detached, the bottom hole is cleaned with compressed air, and a flange opening needs to be reliably blocked in the cleaning process to prevent impurities from entering the steam guide pipe; and tapping by using a screw tap. The method is applied to high-pressure main throttle valve bolt snap-fastener disassembly.

Description

Technical Field

[0001] The invention relates to a method for disassembling a high-pressure main steam valve bolt. Background Art

[0002] During the maintenance of the steam turbine, metal inspection found that the hardness of the main steam valve and regulating valve joint surface bolts exceeded the standard or the bolts were damaged by seizure and needed to be replaced. During the disassembly and replacement process, because the main steam valve and regulating valve bolts had not been disassembled for many years during an overhaul cycle, the bolts had been working at high temperatures for a long time, and the surface oxide scale was thick, which caused a large extrusion force between the bolts and the thread buckle, and the surface oxide scale was concentrated together to form a hard oxide film. When the oxide film was broken, burrs were pulled out on the thread surface, causing the thread to be seizure and difficult to disassemble. In addition, bolts were found to be broken during the maintenance. In view of the above situation, a lot of work was done on the bolt maintenance, and a set of feasible bolt disassembly methods were explored. Summary of the invention

[0003] The purpose of the present invention is to solve the above-mentioned problems, thereby providing a method for disassembling the high-pressure main steam valve bolt bite.

[0004] The above purpose is achieved through the following technical solutions: A method for removing a high-pressure main steam valve bolt from being bitten, the method comprising the following steps: (1) Use a portable cutting machine to cut off the screw at a position 10 mm away from the joint surface of the main steam valve and the regulating valve housing, leaving two bolts at symmetrical positions, and process a special plugging plate; (2) Install the special plugging plate on the door body, tighten it with a nut, attach the magnetic drill to the plugging plate, find the center, and use a drill bit that is about 10mm smaller than the inner diameter of the bolt to drill a hole. The depth should be such that it does not damage the door body. (3) Contact a skilled gas welder to cut the remaining part of the bolt after drilling into four pieces, taking care not to damage the bottom wire, and then use an iron-handled screwdriver to close the end and slowly remove it; (4) Find the two symmetrical thread holes after removing the bolts, tap them and insert the replacement bolts, put the special blocking plate back on the door body, and remove the remaining two bolts in the same way; (5) This method reduces the workload and is more efficient when removing bolts. In addition, due to the small amount of cutting and removal, the material of the valve body is less affected. After a certain amount of disassembly, we have accumulated and summarized experience and applied it to the disassembly of the main steam valve and regulating valve bolts. The effect is good and the disassembly progress is further accelerated. (6) After the bolts are removed, clean the bottom hole with compressed air. Pay attention to reliably sealing the flange opening during the cleaning process to prevent debris from entering the steam pipe; (7) Use a tap to tap.

[0005] The method for disassembling the high-pressure main steam valve bolt bite is that the plugging plate is an A3 steel plugging plate with a thickness of δ=20mm.

[0006] The specific process of step (7) of the method for removing the high-pressure main steam valve bolt from being bitten is as follows: due to the thick oxide scale, tapping will be more laborious. Use a tap head first, but do not use too much force to prevent the tap from breaking. During the tapping process, the tap should be returned several times, and lubricant should be added while tapping. After the tap head taps to the bottom, use a second tap to tap again. Before reinstalling, test all the bolts. The bolts should be qualified if they can be easily screwed in and out. Beneficial Effects

[0007] 1. The disassembly and maintenance method of the main steam valve and regulating valve of the steam turbine in the case of the screw thread buckle being stuck reduces the maintenance time, greatly reduces the work intensity, has high efficiency, and has little impact on the door body material. 2. Due to the thick oxide scale, tapping will be more laborious. Use the tap head first, but do not use too much force to prevent the tap from breaking. During the tapping process, the tap should be returned several times, and lubricant should be added while tapping. After the tap head is tapped to the bottom, use the second tap to tap again. Before reinstalling, test all the bolts, and the bolts should be qualified if they can be easily screwed in and out. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a schematic diagram of the blocking plate structure; Figure 2 It is a schematic diagram of bolt cutting. DETAILED DESCRIPTION

[0009] Reference Figure 1-Figure 2 A method for removing a high-pressure main steam valve bolt bite buckle is disclosed, the method comprising the following steps: (1) Use a portable cutting machine to cut off the screw at a position 10 mm away from the joint surface of the main steam valve and the regulating valve housing, leaving two bolts at symmetrical positions, and process a special plugging plate; (2) Install the special plugging plate on the door body, tighten it with a nut, attach the magnetic drill to the plugging plate, find the center, and use a drill bit that is about 10mm smaller than the inner diameter of the bolt to drill a hole. The depth should be such that it does not damage the door body. (3) Contact a skilled gas welder to cut the remaining part of the bolt after drilling into four pieces, taking care not to damage the bottom wire, and then use an iron-handled screwdriver to close the end and slowly remove it; (4) Find the two symmetrical thread holes after removing the bolts, tap them and insert the replacement bolts, put the special blocking plate back on the door body, and remove the remaining two bolts in the same way; (5) This method reduces the workload and is more efficient when removing bolts. In addition, due to the small amount of cutting and removal, the material of the valve body is less affected. After a certain amount of disassembly, we have accumulated and summarized experience and applied it to the disassembly of the main steam valve and regulating valve bolts. The effect is good and the disassembly progress is further accelerated. (6) After the bolts are removed, clean the bottom hole with compressed air. Pay attention to reliably sealing the flange opening during the cleaning process to prevent debris from entering the steam pipe; (7) When using a tap to tap, due to the thick oxide scale, tapping will be more laborious. Use the head tap first, but do not use too much force to prevent the tap from breaking. During the tapping process, the tap should be returned several times, and lubricant should be added while tapping. After the head tap has tapped to the bottom, use the second tap to tap again. Test all the bolts before reinstalling. The bolts should be qualified if they can be easily screwed in and out.

[0010] The plugging plate is an A3 steel plugging plate with a thickness of δ=20 mm. The size of the plugging plate diameter φ is determined according to the size of the main steam valve and the regulating valve body.

Claims

1. A method for disassembling a high-pressure main steam valve bolt, characterized in that: The method comprises the following steps: (1) Use a portable cutting machine to cut off the screw at a position 10 mm away from the joint surface of the main steam valve and the regulating valve housing, leaving two bolts at symmetrical positions, and process a special plugging plate; (2) Install the special plugging plate on the door body, tighten it with a nut, attach the magnetic drill to the plugging plate, find the center, and use a drill bit that is about 10mm smaller than the inner diameter of the bolt to drill a hole. The depth should be such that it does not damage the door body. (3) Contact a skilled gas welder to cut the remaining part of the bolt after drilling into four pieces, taking care not to damage the bottom wire, and then use an iron-handled screwdriver to close the end and slowly remove it; (4) Find the two symmetrical thread holes after removing the bolts, tap them and insert the replacement bolts, put the special blocking plate back on the door body, and remove the remaining two bolts in the same way; (5) This method reduces the workload and is more efficient when removing bolts. In addition, due to the small amount of cutting and removal, the material of the valve body is less affected. After a certain amount of disassembly, we have accumulated and summarized experience and applied it to the disassembly of the main steam valve and regulating valve bolts. The effect is good and the disassembly progress is further accelerated. (6) After the bolts are removed, clean the bottom hole with compressed air. Pay attention to reliably sealing the flange opening during the cleaning process to prevent debris from entering the steam pipe; (7) Use a tap to tap.

2. The method for removing the high-pressure main steam valve bolt bite according to claim 1 is characterized by: The blocking plate is an A3 steel blocking plate with a thickness of δ=20 mm.

3. The method for removing the high-pressure main steam valve bolt bite according to claim 2 is characterized by: The specific process of step (7) is as follows: due to the thick oxide scale, tapping will be more laborious. Use a tapping head first, but do not use too much force to prevent the tap from breaking. During the tapping process, the tap should be returned several times, and lubricant should be added while tapping. After the tapping head is tapped to the bottom, use a tapping head again. Before reinstalling, test all the bolts. The bolts should be qualified if they can be easily screwed in and out.

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