High temperature gas cooled reactor ring bridge frame integral hoisting method

Abstract

The present application belongs to the technical field of high temperature gas cooled reactor, and particularly relates to a high temperature gas cooled reactor ring suspension bridge frame integral hoisting method. The method comprises the following steps: step 1, fixing a trolley on the bridge frame; step 2, connecting the ring suspension trolley hoisting rigging; the ring suspension trolley hoisting uses 4 high-strength ring hoisting ropes, 4 shackles, one end of the hoisting rope is hung on the crane hook, and the other end is connected with the equipment 4 plate lifting lugs through the shackles; and step 3, trial hoisting and leveling. The method has the beneficial effects that the ring suspension component bridge frame and the trolley are assembled on the ground, and are hoisted integrally to the designated position at one time, the hoisting frequency of the ring suspension is reduced, the influence on other specialities of the reactor building is reduced, and the ring suspension can be hoisted at the target node.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature gas-cooled reactor technology, specifically relating to a method for the overall hoisting of a ring-type bridge frame for high-temperature gas-cooled reactors. Background Technology

[0002] High-temperature gas-cooled reactors (HTGRs) are advanced nuclear energy technologies with fourth-generation characteristics. They possess inherent safety features and have a wide range of applications. The overall construction of the ring-type cable tray is a challenging aspect of the installation process and a critical factor affecting the overall construction quality of the nuclear power plant.

[0003] Researching how to effectively shorten the overall hoisting period of the ring-type cable tray, improve safety and efficiency, ensure safety, and enhance its construction quality is of great significance for improving the engineering construction level and market competitiveness of high-temperature gas-cooled reactor nuclear power plants. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the overall hoisting of the ring-type cable tray of a high-temperature gas-cooled reactor. By assembling the ring-type cable tray and trolley together on the ground in advance, the entire cable tray can be hoisted to the designated position in one go, solving the problems of lacking hoisting tools that meet the requirements for the overall hoisting of the ring-type cable tray and significantly reducing the construction period.

[0005] The technical solution of the present invention is as follows: a method for overall hoisting of a high-temperature gas-cooled reactor ring crane, comprising the following steps: Step 1: Secure the trolley to the bridge frame; Step 2: Connect the lifting slings of the ring crane trolley; The ring trolley uses four high-strength ring slings and four shackles for lifting. One end of the sling is attached to the crane hook, and the other end is connected to the four plate lifting lugs of the equipment through the shackles. Step 3: Trial hoisting and leveling; Four ground anchors are set at the four corners of the ring crane using counterweights or cement supports. The ring crane is then anchored to the ground anchors using auxiliary cables, which include hand-operated hoists and lifting slings. Four guide ropes are symmetrically tied at the wheel positions of the gantry crane and the hook is lifted by the heavy machine; After the ring crane is completely detached from the support, stop lifting the hook and loosen the auxiliary cable.

[0006] Step 1 includes: Step 11: Reinforce the lifting lugs of the cable tray body; Step 12: Secure the trolley; Step 13: Connect the slings.

[0007] Step 11 includes welding two circular steel plates onto the shaft hole steel plates of the eight lifting lugs of the main beam, with the circular plates having a 45° bevel and being fully welded to the shaft hole steel plates; and welding a steel plate onto the bottom of the four bolt-type lifting lugs on the inner side of the two main beams, followed by 100% PT according to the standard.

[0008] Step 12 includes ensuring the brake of the trolley running mechanism is closed, placing the trolley in a designated position; setting two wheel stoppers at the wheel positions and fixing them to the trolley track with bolts; fixing the trolley to the trolley bridge using the wheel stoppers; wrapping one end of a lifting sling around the trolley wheel outrigger and connecting the other end to a hand-operated hoist; connecting another lifting sling to the hand-operated hoist, and securing the trolley by placing it on the bridge lifting lugs, using soft padding to protect the lifting sling at the sealing point; setting up a leveling counterweight placement frame on the mechanical beam of the trolley bridge, and pre-adding counterweights to the placement frame; using rubber or wooden padding to protect the contact point between the bottom of the counterweight frame, which acts as a limit, and securing it with sealing tools.

[0009] Step 13 includes the use of one balance beam, two φ130mm×16m steel wire ropes, eight φ96mm×30m steel wire ropes, and eight custom-made tools for the overall hoisting of the ring crane. The upper sling connection of the balance beam uses two φ130mm×16m steel wire ropes. The two ends of each steel wire rope are respectively hung on both sides of the single anchor hook of the crane's double anchor hook, and the middle is connected to the upper lifting lug of the balance beam. Both steel wire ropes are used in double folds. The lower part of the balance beam is connected to the lifting slings. The lower part of the balance beam is directly connected to the pin shaft. Each pin shaft is connected to one end of two φ96mm×30m steel wire ropes. The other ends of the eight φ96mm×30m steel wire ropes are connected to the eight plate-type lifting lugs of the equipment through eight customized tooling.

[0010] Step 13 includes the use of one support beam, four φ32mm×10m steel wire ropes, four φ32mm×15mm steel wire ropes, two φ180mm×33mm seamless steel wire rope loops, four lifting slings, four slings, four 25mm shackles, two 700mm shackles, four 300t shackles, and eight custom-made tooling for the overall hoisting operation. The auxiliary suspension sling connection of the support beam uses 4 φ32mm×10m steel wire ropes. The middle of each steel wire rope is hung in the double anchor hook groove of the crane. The 4 steel wire ropes correspond to 4 grooves. The ends are connected to 4 φ32mm×15m steel wire ropes. The middle of the φ32mm×15m steel wire ropes is hung on the tubular lifting lug of the balance beam. The ring crane sling connection uses two φ180mm×33m seamless steel wire rope loops. The end of each steel wire rope is hung on the double anchor hook of the crane. At 1 / 3 of the length of the steel wire rope, it is placed on both sides of the support beam, and the end is connected to the pin end of a 700t shackle. On the other side of each 700t shackle, two 150t×44m lifting slings are connected to one end for double use. The other end of each 150t×44m lifting sling is connected to a 300t shackle. The other end of each 300t shackle is connected to a 100t×22m sling for double use. The other end of the 100t×22m sling is connected to a plate lifting lug through a custom tool.

[0011] Step 3 includes using measuring instruments to measure the longitudinal and transverse levelness of the main beam of the ring crane. Based on the tilt state of the ring crane, the number or position of counterweights on the ring crane beam is adjusted. If significant tilting is found, the equipment is returned to the supports and leveled using counterweights or sandbags. The leveling items are secured to the equipment using a sealing tool to prevent displacement during hoisting. After leveling, the crane operator lifts the equipment until the bottom is completely 0.2m away from the support surface and holds it stationary for 5 minutes. During this process, the equipment should remain stable. During the trial lift, a comprehensive inspection of the equipment's sling connections and the crane foundation is conducted. If no abnormalities are found, the next step is performed. The crane slowly lifts the hook, so that the bottom platform of the ring crane is 2 meters above the surrounding obstacles, at which point it is 48 meters above the ground. At the same time, the guy ropes attached to the equipment are knotless. The front and rear cranes move along the direction of the laid roadbed box, with the front crane moving from west to east and the rear crane moving from north to south. During the synchronous movement of the front and rear cranes, the crane boom rotates to the left. When the crane reaches the positioning point, the front and rear cranes stop moving. When the ring crane is about to be rotated above the nuclear island, the top of the outer wall of the nuclear island is monitored. After the rotation stops, the luffing operation is carried out. When the remaining distance is less than 2 meters, the hook is lifted and the luffing is adjusted until the ring crane is directly above the nuclear island.

[0012] The beneficial effects of this invention are as follows: by assembling the ring crane components (bridge and trolley) on the ground and hoisting them to the designated position in one go, the number of ring crane hoisting operations is reduced, the impact on other specialties in the reactor building is reduced, and the ring crane can achieve hoisting at the target node is ensured; since the center of gravity of the equipment provided by the manufacturer does not coincide with the center, by adding and fixing counterweights, the hoisting difficulty and risk are reduced, and the hoisting quality is improved; the lower part of the adjusting balance beam can be adjusted and rotated back and forth through pins, yokes, lifting rings, and connecting parts, preventing hoisting difficulties caused by equipment tilting due to deviation of the lifting center position, and meeting actual hoisting requirements. Attached Figure Description

[0013] Figure 1 Schematic diagram of the wheel stop tooling; Figure 2 Schematic diagram of the stop wheel tooling installation; Figure 3 Schematic diagram for fixing the counterweight frame; Figure 4 This is a schematic diagram of the counterweight frame; Figure 5 Main view of the hoisting sling connection; Figure 6 Side view of the hoisting sling connection; Figure 7 This is a schematic diagram of a balance beam; Figure 8 This is a schematic diagram of the overall lifting lug layout for the ring crane; Figure 9 A schematic diagram showing the connection of auxiliary suspension slings for the supporting beam; Figure 10 This is a schematic diagram of the overall lifting sling connection for a ring crane.

[0014] In the diagram: 21 Wheel, 22 Wheel stop fixture, 23 Bolts and nuts, 24 Rail, 31 Counterweight frame position, 51 Wire rope, 52 Balance beam, 53 Wire rope, 54 Custom fixture, 81 Double folded wire rope, 82 Shackle, 83 Double folded wire rope, 101 Support beam, 102 Shackle, 103 Double folded high-strength lifting sling, 104 Shackle, 105 Double folded high-strength lifting sling, 106 Custom fixture. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] The high-temperature gas-cooled reactor ring crane bridge assembly hoisting method and special tooling provided by this invention uses wheel chocks to fix the trolley to the ring crane bridge assembly, and uses lifting straps to connect the bridge assembly lifting lugs for sealing and fixing the trolley, thus achieving overall hoisting of the ring crane assembly; a leveling counterweight placement frame is set on the mechanical beam of the ring crane bridge assembly to level the overall center of gravity of the equipment and make it coincide with the center; a special hoisting tooling for overall hoisting of the ring crane assembly assembly - an adjustable balance beam - is designed, with the lower part of the crossbeam being movable and hinged to adjust the tilt caused by the asymmetry of the lifting center position.

[0017] For the overall hoisting of the ring crane, first fix the trolley to the bridge frame, and then hoist it by connecting the bridge frame to the hoisting lugs using slings. First, ensure that the brake of the ring crane trolley's running mechanism is in the closed state, place the ring crane trolley in the designated position, and after placement, set two wheel stop fixtures at the front and rear of each wheel position, and use bolts to fix them to the trolley track to limit the trolley's displacement on the track. Fix the trolley to the ring crane bridge frame using the wheel stop fixtures, use a hoisting sling to wrap one end around the trolley wheel and the outrigger, and connect the other end to a hand chain hoist. Connect another hoisting sling to the hand chain hoist, and put the hoisting sling on the bridge frame hoisting lugs to seal and fix the trolley. Use soft padding to protect the hoisting sling at the sealing point.

[0018] Because the center of gravity of the equipment does not completely coincide with the center, a leveling counterweight placement frame is set on the mechanical beam of the ring crane bridge, and a 3t counterweight is added in advance in the placement frame. The bottom of the counterweight frame, which serves as a limit, is protected by rubber or wooden boards at the contact point with the ring crane, and is fixed with a vehicle sealing tool.

[0019] The lifting tool for the ring crane component has eight pressed steel wire rope locks suspended at the bottom. These eight steel wire rope locks are connected to eight lifting lugs on the main beam of the ring crane cable tray via shackles, enabling the overall lifting of the cable tray. The adjustable balance beam has a hollow cylindrical structure, with lifting lugs installed on the upper part of the beam. Shackles and steel wire ropes can be used to connect to the crane hook. The lower part of the beam is hinged, allowing for forward and backward adjustment and rotation via pins, yokes, lifting rings, and connectors. This is used to correct tilting caused by asymmetrical lifting center of gravity.

[0020] The method for hoisting the ring-type cable tray of a high-temperature gas-cooled reactor includes the following steps: Step 1: Secure the trolley to the cable tray, specifically including: Step 11: Strengthen the lifting lugs of the cable tray body Two 8mm thick circular steel plates are welded onto the shaft hole steel plates of the eight lifting lugs of the main beam. The circular steel plates are fully welded to the shaft hole steel plates with a 45° bevel, and the weld leg height is 6mm. A 400×150×16mm steel plate is welded to the bottom of the four bolt-type lifting lugs on the inner side of the two main beams. The weld appearance is free of obvious defects such as slag inclusions, porosity, and oxides. After welding, 100% PT is performed according to the standard. Step 12: Secure the trolley Ensure the brake of the ring crane trolley traveling mechanism is in the closed state, and place the ring crane trolley in the designated position; Two wheel stop fixtures 22 are installed at the front and rear of each wheel 21 and fixed to the trolley track with bolts to limit the displacement of the trolley on the track. The trolley is then fixed to the ring crane bridge using the wheel stop fixtures. A lifting sling is wrapped around the outrigger of the trolley wheel and the other end is connected to a hand chain hoist. Another lifting sling is connected to the hand chain hoist and placed on the lifting lug of the bridge for sealing and fixing. The sealing point is protected by soft padding. A leveling counterweight placement frame 31 is set on the mechanical beam of the ring crane bridge, and a 3t counterweight is added in advance inside the placement frame. The bottom of the counterweight frame, which acts as a limit, is protected by rubber or wooden padding at the contact point with the ring crane and is fixed with sealing tools.

[0021] Step 13: Connecting the slings Method 1: The overall hoisting of the ring crane uses one 600t-class balance beam 52, two φ130mm×16m steel wire ropes 51 (length after double folding), eight φ96mm×30m steel wire ropes 53, and eight 90t custom-made tooling pieces 54.

[0022] Connection of slings to the upper part of the balance beam: Two φ130mm×16m steel wire ropes (length after being folded in half) are selected. The two ends of each steel wire rope are respectively hung on both sides of the single anchor hook of the double anchor hook of the 3600t crane, and the middle is connected to the upper lifting lug of the balance beam. Both steel wire ropes are used in double folds. Connection of slings at the bottom of the balance beam: The lower part of the balance beam is directly connected to the pin shaft, and each pin shaft is connected to one end of two φ96mm×30m steel wire ropes (a total of 8 ropes). The other ends of the 8 φ96mm×30m steel wire ropes are connected to the 8 plate lifting lugs of the equipment through 8 90t customized tooling.

[0023] Method 2: The hoisting operation used a 2000t-class support beam 101, four φ32mm×10m steel wire ropes, four φ32mm×15mm steel wire ropes, two φ180mm×33mm seamless steel wire rope loops, four 150t×44m lifting slings, four 100t×22m slings, four 25mm shackles, two 700mm shackles, four 300t shackles, and eight custom-made tooling.

[0024] Auxiliary suspension sling connection for support beam: Four φ32mm×10m steel wire ropes are selected. The middle of each steel wire rope is hung in the double anchor hook groove of the crane. The four steel wire ropes correspond to four grooves. The ends are connected to the ends of four φ32mm×15m steel wire ropes through 25t. The middle of the φ32mm×15m steel wire rope 83 is hung on the tube lug of the balance beam. Ring crane sling connection Two φ180mm×33m seamless steel wire rope loops are selected. The end of each steel wire rope is hung on the double anchor hook of the crane. About 1 / 3 of the steel wire rope is placed on both sides of the support beam, and the end is connected to the pin end of a 700t shackle. Each 700t shackle is connected to one end of two 150t×44m lifting slings with double folding on the other side. The other end of each 150t×44m lifting sling with double folding is connected to a 300t shackle. The other end of each 300t shackle is connected to one end of a 100t×22m sling with double folding on the other side. The other end of the 100t×22m sling with double folding is connected to a plate lifting lug through a 90t custom tool 106.

[0025] Step 2: Connecting the lifting slings of the ring crane trolley The lifting trolley uses four 80mm×15m high-strength ring slings and four 35t shackles. One end of the sling is attached to the crane hook, and the other end is connected to the four plate-type lifting lugs of the equipment through the 35t shackles.

[0026] Step 3: Trial hoisting and leveling Four ground anchors are set near the four corners of the ring crane using counterweights or cement supports. The ring crane is then anchored to the ground anchors using auxiliary cables, which consist of a 10t hand-operated hoist and lifting straps. Four guide ropes, each no less than 10m long, are symmetrically tied at the wheel position of the 3600t crane, and the hook is slowly lifted by the 3600t crane. At four ground anchor locations, dedicated personnel were assigned to assist in loosening the hand chain hoists to prevent the ring crane from swinging excessively when it leaves the support. After the ring crane is completely freed from the support, stop lifting the hook and loosen the auxiliary cable; Use measuring instruments to measure the longitudinal and transverse levelness of the main beam of the ring crane. Adjust the number or position of the counterweights on the ring crane beam according to the tilt state of the ring crane. If the equipment is found to be significantly tilted, put the equipment back on the support and use counterweights or sandbags to level it. Use a vehicle sealing tool to fix the leveling items on the equipment to prevent displacement during the hoisting process. After leveling, the crane operator will lift the equipment until it is completely 0.2m off the support surface and hold it stationary for 5 minutes, ensuring the equipment remains stable throughout the process. During the trial lift, a comprehensive inspection of the equipment's sling connections, crane foundation, etc., should be conducted. If no abnormalities are found, proceed to the next step. The crane slowly lifted the hook, so that the bottom platform of the ring crane was 2 meters above the surrounding obstacles. At this time, it was about 48 meters above the ground, and the guy ropes attached to the equipment were knotless. The 3600t crane travels along the paved roadbed, with the front crane moving from west to east and the rear crane moving from north to south.

[0027] During the synchronous movement of the front and rear vehicles, the crane boom rotates to the left until it reaches the designated position, at which point the front and rear vehicles stop moving.

[0028] When the hoisting component is about to be moved above the nuclear island, workers should be assigned to monitor the top of the outer wall of the nuclear island to prevent the hoisting component from colliding with the outer wall of the nuclear island or any protrusions. After the slewing stops, the luffing operation is carried out. When the margin is less than 2m, the hook is lifted and the luffing is adjusted until the ring lifting component is directly above the nuclear island.

[0029] After the equipment was roughly positioned on top of the nuclear island, the crane slowly lowered its hook and made minor adjustments. When the equipment is about 5m above the landing point, the equipment is swayed by the guy ropes until it is lowered to less than 2m above the landing point. According to the installation plan, the equipment positioning was checked. Before lifting, 4.75t shackles and 5t lifting straps were set on the outer lugs of the rotating mechanism trolley group at the four corners of the ring crane. 56 hand chain hoists were hung on the brackets at the farthest position of the bridge frame in advance for the ring crane positioning adjustment. When the ring is lowered to 200mm above the positioning point, connect the rigging and fine-tune the positioning position using the pulley until the requirements are met. There are no strict directional requirements for the equipment positioning, and the installation positioning conditions are met. After checking the equipment's positioning and confirming that the 3600t crane can be unhooked, the crane will slowly lower the hook until it is released, and the slings will be disconnected from the equipment. When removing the shackle, a fall arresting rope should be attached to prevent the shackle from falling directly to the bottom of the nuclear island.

Claims

1. A method for the overall hoisting of a ring-shaped cable tray for a high-temperature gas-cooled reactor, characterized in that, Includes the following steps: Step 1: Secure the trolley to the bridge frame; Step 2: Connect the lifting slings of the ring crane trolley; The ring trolley uses four high-strength ring slings and four shackles for lifting. One end of the sling is attached to the crane hook, and the other end is connected to the four plate lifting lugs of the equipment through the shackles. Step 3: Trial hoisting and leveling; Four ground anchors are set at the four corners of the ring crane using counterweights or cement supports. The ring crane is then anchored to the ground anchors using auxiliary cables, which include hand-operated hoists and lifting slings. Four guide ropes are symmetrically tied at the wheel positions of the gantry crane and the hook is lifted by the heavy machine; After the ring crane is completely detached from the support, stop lifting the hook and loosen the auxiliary cable.

2. The method for integral hoisting of the high-temperature gas-cooled reactor ring crane as described in claim 1, characterized in that, Step 1 includes: Step 11: Reinforce the lifting lugs of the cable tray body; Step 12: Secure the trolley; Step 13: Connect the slings.

3. The method for integral hoisting of the high-temperature gas-cooled reactor ring crane as described in claim 2, characterized in that: Step 11 includes welding two circular steel plates onto the shaft hole steel plates of the eight lifting lugs of the main beam, with the circular plates having a 45° bevel and being fully welded to the shaft hole steel plates; and welding a steel plate onto the bottom of the four bolt-type lifting lugs on the inner side of the two main beams, followed by 100% PT according to the standard.

4. The method for integral hoisting of the high-temperature gas-cooled reactor ring crane as described in claim 2, characterized in that: Step 12 includes: determining that the brake of the ring crane trolley running mechanism is in the closed state; placing the ring crane trolley in the designated position; setting two wheel stop fixtures at the wheel positions and fixing them to the trolley track with bolts; fixing the trolley to the ring crane bridge frame using the wheel stop fixtures; wrapping one end of a lifting sling around the outrigger of the trolley wheel and connecting the other end to a hand chain hoist; connecting another lifting sling to the hand chain hoist, and sealing the trolley by putting the lifting sling on the bridge frame lifting lugs, using soft padding to protect the lifting sling at the sealing point; setting up a leveling counterweight placement frame on the ring crane bridge mechanical beam, and adding counterweights in advance inside the placement frame; The contact point between the bottom upright of the counterweight frame, which serves as a limit, and the ring crane is protected by rubber or wooden padding and secured with a vehicle sealing tool.

5. The method for integral hoisting of the high-temperature gas-cooled reactor ring crane as described in claim 2, characterized in that: Step 13 includes the use of one balance beam, two φ130mm×16m steel wire ropes, eight φ96mm×30m steel wire ropes, and eight custom-made tooling for the overall hoisting of the ring crane. The upper sling connection of the balance beam uses two φ130mm×16m steel wire ropes. The two ends of each steel wire rope are respectively hung on both sides of the single anchor hook of the crane's double anchor hook, and the middle is connected to the upper lifting lug of the balance beam. Both steel wire ropes are used in double folds. The lower part of the balance beam is connected to the lifting slings. The lower part of the balance beam is directly connected to the pin shaft. Each pin shaft is connected to one end of two φ96mm×30m steel wire ropes. The other ends of the eight φ96mm×30m steel wire ropes are connected to the eight plate-type lifting lugs of the equipment through eight customized tooling.

6. The method for integral hoisting of the high-temperature gas-cooled reactor ring crane as described in claim 2, characterized in that: Step 13 includes the use of one support beam, four φ32mm×10m steel wire ropes, four φ32mm×15mm steel wire ropes, two φ180mm×33mm seamless steel wire rope loops, four lifting slings, four slings, four 25mm shackles, two 700mm shackles, four 300t shackles, and eight custom-made tooling for the overall hoisting operation. The auxiliary suspension sling connection of the support beam uses 4 φ32mm×10m steel wire ropes. The middle of each steel wire rope is hung in the double anchor hook groove of the crane. The 4 steel wire ropes correspond to 4 grooves. The ends are connected to 4 φ32mm×15m steel wire ropes. The middle of the φ32mm×15m steel wire ropes is hung on the tubular lifting lug of the balance beam. The ring crane sling connection uses two φ180mm×33m seamless steel wire rope loops. The end of each steel wire rope is hung on the double anchor hook of the crane. At 1 / 3 of the length of the steel wire rope, it is placed on both sides of the support beam, and the end is connected to the pin end of a 700t shackle. On the other side of each 700t shackle, two 150t×44m lifting slings are connected to one end for double use. The other end of each 150t×44m lifting sling is connected to a 300t shackle. The other end of each 300t shackle is connected to a 100t×22m sling for double use. The other end of the 100t×22m sling is connected to a plate lifting lug through a custom tool.

7. The method for integral hoisting of the high-temperature gas-cooled reactor ring crane as described in claim 1, characterized in that: Step 3 includes using measuring instruments to measure the longitudinal and transverse levelness of the main beam of the ring crane. Based on the tilt state of the ring crane, the number or position of counterweights on the ring crane beam is adjusted. If significant tilting is found, the equipment is returned to the supports and leveled using counterweights or sandbags. The leveling items are secured to the equipment using a sealing tool to prevent displacement during hoisting. After leveling, the crane operator lifts the equipment until the bottom is completely 0.2m away from the support surface and holds it stationary for 5 minutes. During this process, the equipment should remain stable. During the trial lift, a comprehensive inspection of the equipment's sling connections and the crane foundation is conducted. If no abnormalities are found, the next step is performed. The crane slowly lifts the hook, so that the bottom platform of the ring crane is 2 meters above the surrounding obstacles, at which point it is 48 meters above the ground. At the same time, the guy ropes attached to the equipment are knotless. The front and rear cranes move along the direction of the laid roadbed box, with the front crane moving from west to east and the rear crane moving from north to south. During the synchronous movement of the front and rear cranes, the crane boom rotates to the left. When the crane reaches the positioning point, the front and rear cranes stop moving. When the ring crane is about to be rotated above the nuclear island, the top of the outer wall of the nuclear island is monitored. After the rotation stops, the luffing operation is carried out. When the remaining distance is less than 2 meters, the hook is lifted and the luffing is adjusted until the ring crane is directly above the nuclear island.

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