A method for demolishing an oil pipeline under a bridge

Abstract

The present invention discloses a method for demolishing an oil pipeline under a bridge, including: S1: Construction preparation; S2: Steam purging of the pipeline: Steam purging and warming the pipeline to wake up the oil stored in the oil pipeline; S3: Nitrogen pigging to clean the pipeline: Cleaning and emptying the oil pipeline through a pig; S4: Cutting and hoisting the expansion elbow: After the oil pipeline is cleaned and emptied, inspect the construction platform, overhead crane and track, re-reinforce the rusted and weld-cracked parts, cut the expansion elbow with a water jet, and then hoist the cut expansion elbow; S5: Cutting and hoisting the straight pipe. The present invention combines the conventional structure of the existing oil pipeline under the bridge, and proposes a set of general and effective demolition methods for the problems of complex construction environment and narrow construction space it faces. The overall construction cost is relatively low, the construction is convenient, and at the same time, the impact on the bridge during the demolition process is effectively reduced, providing reference for similar projects and having extremely high promotion value.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge deck construction, and particularly relates to a method for removing an oil pipeline under a bridge. Background Art

[0002] An oil pipeline system, that is, a pipeline system for transporting petroleum and petroleum products, mainly consists of an oil pipeline, an oil transfer station, and other auxiliary related equipment. It is one of the main equipment in the petroleum storage and transportation industry and is also the most important conveying equipment for crude oil and petroleum products. Compared with railway and road oil transportation, which are also land transportation methods, pipeline oil transportation has the characteristics of large transportation volume, good airtightness, low cost, and high safety factor.

[0003] An oil pipeline (also called a pipeline or a pipeline network) is composed of an oil pipe and its accessories. The pipe material of the oil pipeline is generally steel pipe, and long-distance pipelines are connected by welding and flange and other connecting devices. When the oil pipeline passes through waters such as a river, the oil pipeline is usually arranged under the bridge deck and fixedly connected to the bridge through corresponding fixing devices to achieve the fixing of the oil pipeline. As the service time of the bridge increases, some bridges face the problem of reconstruction or even demolition. It is necessary to first remove the oil pipeline to not affect the normal construction of the bridge. However, for the removal of the oil pipeline under the bridge, due to limited construction space, different from the removal of the oil pipeline set on the ground, there is no effective removal method, and there is an urgent need for a relatively general method for removing the oil pipeline under the bridge for reference in future similar projects. Summary of the Invention

[0004] In order to solve the problems existing in the above-mentioned prior art, a method for removing an oil pipeline under a bridge is provided.

[0005] The technical solution adopted by the present invention to solve its technical problems is:

[0006] The present invention provides a method for removing an oil pipeline under a bridge. The oil pipeline includes a plurality of straight pipes and a plurality of expansion elbows, and both ends of the expansion elbows are connected to the straight pipes in a communicating manner;

[0007] The removal method includes the following steps:

[0008] S1: Construction preparation: A track is fixedly connected under the bridge along the length direction of the bridge, and a truss crane is slidably connected to the track. The truss crane is used to build a construction platform at the expansion elbow;

[0009] S2: Steam purging of the pipeline: Steam purging and warming the pipeline to wake up the oil stored in the oil pipeline;

[0010] S3: Nitrogen purging of the pipeline with a pig: The oil pipeline is purged and emptied through a pig;

[0011] S4: Cutting and lifting the expansion elbow: After the oil pipeline is cleaned and emptied, inspect the construction platform, trolley and track, reinforce the rusty and weld-cracked parts, cut the expansion elbow with a water jet, and then lift the cut expansion elbow.

[0012] S5: Cutting and lifting the straight pipe: Cut off the connection seat between the straight pipe and the bridge, install guiding devices at both ends of the straight pipe, and use a winch to tow the straight pipe along the length direction of the straight pipe to the outside of the bridge. During the demolition process, the straight pipes on both sides of the bridge are demolished symmetrically section by section at the same time.

[0013] Preferably, in S2, a flange blanking plate is fixedly connected to the end of the intake end of the oil pipeline. The flange blanking plate is provided with a through hole, and a steam inlet pipe is fixedly connected in the through hole. The steam inlet pipe is communicated with the oil pipeline. The steam inlet pipe includes a steam inlet and a drain port.

[0014] Preferably, in S2, a flange blanking plate is fixedly connected to the end of the outlet end of the oil pipeline. The flange blanking plate is provided with a through hole, and a steam outlet pipe is fixedly connected in the through hole. The steam outlet pipe is communicated with the oil pipeline. The steam outlet pipe is sequentially connected with a steam stop valve and a steam trap, and the other end of the steam outlet pipe is communicated with an oil storage tank.

[0015] Preferably, a blanking plate is fixedly connected to the other end of the steam outlet pipe. The blanking plate is provided with an oil drain hole. The oil storage tank is arranged below the oil drain hole, and the oil drain hole is connected with an oil drain valve; steam is conveyed into the oil pipeline through the steam inlet pipe. Every interval of T time, check the oil waking situation through the oil drain hole. After the oil waking is completed, open the oil drain valve to drain the oil.

[0016] Preferably, in S3, the pigging ball is a water-filled rubber ball. A pig launcher and a pig receiver are respectively arranged on both sides of the oil pipeline. The pig launcher and the pig receiver are both connected with a vent valve and a pressure gauge. The pig receiver includes a blowdown port and an exhaust hole. The blowdown port is connected with a blowdown valve. One side of the pig launcher and the pig receiver is detachably connected with a blind plate. The pig launcher is communicated with a nitrogen storage tank and a high-pressure pump through a connecting pipe, and the connecting pipe is connected with an intake valve.

[0017] Preferably, the method for purging the pipeline with nitrogen includes:

[0018] S11: First, open the blind plate on the pig launcher, send the pigging ball into the pig launcher, open the vent valve on the pig launcher for venting, and ensure that the pressure in the pig launcher is 0 through the pressure gauge;

[0019] S12: Close the vent valves on the pig launcher and the pig receiver, and open the blowdown valve on the pig receiver;

[0020] S13: Open the outlet valve of the nitrogen storage tank and the high-pressure pump in sequence, inject nitrogen by opening the intake valve on the connecting pipe, and send the pigging ball.

[0021] S14: After the first pigging ball reaches the pig receiver, close the intake valve, close the blowdown valve on the pig receiver, open the vent valve on the pig receiver to relieve pressure until the pressure is zero. After completion, open the blind flange of the pig receiver, take out the pigging ball and inspect, describe, and record it.

[0022] S15: Observe the wear, scratches, and deformation of the pigging ball, repeat the pipeline pigging until no water is discharged from the blowdown port and there is no debris accumulation, which means the cleaning is qualified.

[0023] Preferably, in the S4, the cutting and hoisting method of the expansion elbow includes:

[0024] S21: Use a chain block and a hoop to hang the expansion elbow under the transverse rib of the main beam of the bridge.

[0025] S22: Use a wire brush to clean the rust and debris at the cutting part of the expansion elbow. After cleaning, install a flexible track and a water jet cutting machine, adjust the vertical adjustment shaft, align the axis of the nozzle of the water jet cutting machine with the cutting plane, and perform cutting. When the water jet cutting machine goes around the expansion elbow for one week, the cutting work of the expansion elbow is completed, and it is detected with a combustible gas detector.

[0026] S23: After cutting both ends of the water jet cutting machine, make the expansion elbow an open container, and manually clean the oil stain inside the expansion elbow.

[0027] S24: Use gas cutting to cut the expansion elbow into several sections, then lower it to the construction platform, use a truss crane to move it horizontally to the outside of the bridge, and use a bridge deck truck crane to hoist it to the bridge deck and transport it to the storage site uniformly.

[0028] Preferably, in the S5, the cutting and hoisting method of the straight pipe includes:

[0029] S31: Set several winches for pipeline dragging and hoisting on both sides of the common pier of the bridge, and set several groups of fixed pulleys on the end cross beam of the bridge.

[0030] S32: Install a roller support for the straight pipe sliding every N meters below the straight pipe.

[0031] S33: Use an angle grinder to cut off the connection between the straight pipe and the bridge connection seat, install a guiding device at the end of the straight pipe, and fix it with bolts. The towing wire rope of the winch is connected to the end of the pipeline along the guiding device, and the straight pipe is towed along the length direction of the straight pipe to the common pier through the winch.

[0032] S34: Use a water cutter to cut the straight pipe into several sections, fix both ends of the straight pipe with steel wire ropes and hoop respectively, and lower it vertically to the ground by a winch for centralized storage.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] Combined with the conventional structure of the existing oil pipeline under the bridge, the present invention proposes a set of general and effective demolition methods for the problems of complex construction environment and narrow construction space it faces. The overall construction cost is relatively low, the construction is convenient, and at the same time, the impact on the bridge during the demolition process is effectively reduced, providing reference for similar projects and having extremely high popularization value. Description of the Drawings

[0035] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0036] Figure 1 is the overall flow chart of the present invention;

[0037] Figure 2 is the schematic diagram of the steam inlet pipe of the present invention;

[0038] Figure 3 is the schematic diagram of the steam outlet pipe of the present invention;

[0039] Figure 4 is the schematic diagram of the structure of the pig launcher of the present invention;

[0040] Figure 5 is the schematic diagram of the structure of the pig receiver of the present invention;

[0041] Figure 6 is the schematic diagram of the lifting points of the expansion elbow of the present invention;

[0042] Figure 7 is the schematic diagram of the setting of the winch and pulley block of the present invention;

[0043] Figure 8 is the schematic diagram of the structure of the guiding device of the present invention;

[0044] Figure 9 is the schematic diagram of the vertical towing and lowering of the straight pipe of the present invention.

[0045] Description of the Reference Numerals:

[0046] 1 Oil pipeline; 2 Pig; 3 Connecting pipe; 4 Bleed valve; 5 Steel pipe; 6 Pressure gauge; 7 Pig launcher; 8 Flange head; 9 Exhaust hole; 10 Deceleration layer; 11 Pig receiver; 12 Blind plate. Detailed Embodiments

[0047] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where like or similar reference numerals denote like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0048] As Figures 1-9 shown, this embodiment proposes a method for removing an oil pipeline under a bridge. The oil pipeline 1 includes a plurality of straight pipes and a plurality of expansion elbows, and both ends of the expansion elbows are connected to the straight pipes. The function of the expansion elbows is as follows: when the pipeline is heated, it will deform due to thermal expansion and contraction, and the expansion elbows can offset this deformation of the pipeline to prevent the pipeline from being damaged by extrusion due to deformation. Therefore, expansion elbows are provided at regular intervals.

[0049] The removal method includes the following steps:

[0050] S1: Construction preparation: A track is fixedly connected under the bridge along the length direction of the bridge, and a trolley is slidably connected to the track. The trolley is used to set up a construction platform at the expansion elbow.

[0051] S2: Steam purging of the pipeline: Steam purging and warming the oil in the oil pipeline 1 are carried out.

[0052] S3: Nitrogen pigging to clean the pipeline: The oil pipeline 1 is cleaned and emptied through a pigging ball.

[0053] S4: Cutting and lifting of the expansion elbow: After the oil pipeline 1 is cleaned and emptied, the construction platform, trolley and track are inspected, and the rusted and welded joint cracking parts are re-reinforced. The expansion elbow is cut by a water jet, and then the cut expansion elbow is lifted.

[0054] S5: Cutting and lifting of the straight pipe: The connection seat between the straight pipe and the bridge is removed, guiding devices are installed at both ends of the straight pipe, and the straight pipe is pulled to the outside of the bridge along the length direction of the straight pipe by a winch. During the removal process, the straight pipes on both sides of the bridge are removed symmetrically section by section at the same time to reduce the impact on the bridge.

[0055] In S1, usually, an inspection walkway, a trolley and a track are also provided on one side of the oil pipeline 1 under the bridge. The track is arranged along the length direction of the bridge, and the trolley is slidably connected to the track. Before construction, the inspection walkway, trolley and track are first inspected, and the damaged and rusted parts are reinforced to ensure walking safety during construction.

[0056] With the help of the trolley, a construction platform is set up at the expansion elbow for personnel operation and pipeline lifting, and at the same time, it is checked whether the oil pipeline 1 has damage, deformation and other conditions.

[0057] When removing the oil pipeline 1, since the oil pipeline 1 has usually been placed for a period of time before removal and there is residual oil in the pipeline, steam purging and warming the pipeline to wake up the oil are carried out first to facilitate the subsequent disassembly work.

[0058] In S2, a flange blanking plate is fixedly connected to the end of the intake end of the oil pipeline 1. The flange blanking plate is provided with a through hole, and a steam inlet pipe is fixedly connected in the through hole. The steam inlet pipe is communicated with the oil pipeline 1. The steam inlet pipe includes a steam inlet and a drain port. At the same time, a pressure relief port and a pressure gauge are also connected to the steam inlet.

[0059] In S2, a flange blanking plate is fixedly connected to the end of the outlet end of the oil pipeline. The flange blanking plate is provided with a through hole, and a steam outlet pipe is fixedly connected in the through hole. The steam outlet pipe is communicated with the oil pipeline 1. The steam outlet pipe is sequentially connected with a steam stop valve and a steam trap. The other end of the steam outlet pipe is communicated with an oil storage tank.

[0060] A blanking plate is fixedly connected to the other end of the steam outlet pipe. The blanking plate is provided with an oil drain hole. The oil storage tank is arranged below the oil drain hole, and the oil drain hole is connected with an oil drain valve; steam is conveyed into the oil pipeline 1 through the steam inlet pipe. Every T hours, check the situation of waking up the oil through the oil drain hole. After waking up the oil is completed, open the oil drain valve to drain the oil.

[0061] Use a steam vehicle to carry out steam purging on the oil pipeline 1. The steam pressure is controlled at 0.3 - 0.5 Mpa, and the steam flow rate is 4 m3 / h. Steam is passed through the pipeline section for 24 hours to warm the pipeline. Open the oil drain hole every T hours to check the situation of waking up the oil. After waking up the oil is completed, open the oil drain valve to drain the oil, where T is two hours.

[0062] Before purging, conduct a detailed inspection on the steam pipeline to be purged, temporary piping, pipe supports, valves, vent pipes, etc., and confirm that each component is firm and reliable.

[0063] Before pipeline purging, fully warm the pipeline and pay attention to draining water to prevent water hammer phenomenon. When introducing steam to warm the pipeline in the first cycle of purging, pay attention to checking whether the pipeline thermal expansion, pipeline sliding, and bracket deformation are normal.

[0064] In S3, a pig launcher 7 and a pig receiver 11 are respectively arranged on both sides of the oil pipeline 1. The pig launcher 7 and the pig receiver 11 are both connected with a vent valve 4 and a pressure gauge 6. The pig receiver 11 includes a blowdown port and an exhaust hole 9. The blowdown port is connected with a blowdown valve. A blind plate 12 is detachably connected to one side of the pig launcher 7 and the pig receiver 11. The pig launcher 7 is communicated with a nitrogen storage tank and a high-pressure pump through a connecting pipe, and the connecting pipe is connected with an inlet valve.

[0065] Among them, both ends of the oil pipeline 1 are connected to the pig launcher 7 and the pig receiver 11 through the connecting pipes 3 respectively, and the diameters of both the pig launcher 7 and the pig receiver 11 are larger than that of the oil pipeline 1. The pigging ball 2 is a water-filled rubber ball, and the interference of the pigging ball 2 is 4-8%. Then calculate the required nitrogen gas volume.

[0066] Among them, the pig launcher 7 is also connected to a steel pipe 5, and the other end of the steel pipe 5 is connected to an air suction pump. The vent valve 4 can be set on the steel pipe 5. By opening the vent valve 4 and the air suction pump, the air suction work of the pig launcher 7 can be realized to ensure that the pressure in the pig launcher 7 is 0 during operation.

[0067] Blind plates 12 are connected to both sides of the pig launcher 7 and the pig receiver 11. A flange head 8 is arranged on one side of the blind plate 12, and the flange head 8 is used to block the pig launcher 7 and the pig receiver 11. At the same time, a deceleration layer 10 is arranged in the pig receiver 11, and the deceleration layer 10 is used for the deceleration work of the pigging ball 2.

[0068] The method for purging the pipeline with nitrogen includes:

[0069] S11: First, open the blind plate 12 on the pig launcher 7, send the pigging ball 2 into the pig launcher 7, open the vent valve 4 on the pig launcher 7 for venting, and ensure that the pressure in the pig launcher 7 is 0 through the pressure gauge 6;

[0070] S12: Close the vent valve 4 on the pig launcher 7 and the pig receiver 11, and open the drain valve on the pig receiver 11;

[0071] S13: Open the outlet valve of the nitrogen storage tank and the high-pressure pump in sequence, inject nitrogen through the inlet valve on the connecting pipe, and send the pigging ball 2;

[0072] S14: When the first pigging ball 2 reaches the pig receiver 11, close the inlet valve, close the drain valve on the pig receiver 11, open the vent valve 4 on the pig receiver 11 for pressure relief until the pressure is zero. After completion, open the blind plate 12 of the pig receiver 11, take out the pigging ball 2 and check, describe, and record;

[0073] S15: Observe the wear, scratches, and deformation of the pigging ball 2, and repeat the pipeline purging until no water is discharged from the drain port and no sundries are accumulated, which means the cleaning is qualified.

[0074] Lay a plastic anti-oil cloth and a temporary oil receiving barrel on the construction platform at the expansion elbow to prevent polluted liquid and exposed plastic of the insulation layer from falling into the river or scattering to the surrounding area, causing pollution to the river and the surrounding environment.

[0075] The construction platform is installed by being transported to the bottom of the bridge by a barge and then hoisted into place. After demolition, the oil pipelines are lifted by a crane or a winch and placed on the ship in sections for transportation to the designated location. For the oil pipelines near the temporary bridge, they can be lifted onto the temporary bridge and transported away. Through checking calculations, it is determined whether the rail I-beams, hangers, connecting bolts and welds of the platform hanger meet the construction requirements. If not, corresponding reinforcement work is carried out in a timely manner.

[0076] In S4, the cutting and hoisting method for the expansion elbow includes:

[0077] S21: Use a chain block and a hoop to hang the expansion elbow under the transverse rib of the main beam of the bridge;

[0078] S22: Use a wire brush to clean the rust and debris at the cutting part of the expansion elbow. After cleaning, install a flexible track and a water jet cutting machine, adjust the vertical adjustment shaft, align the axis of the nozzle of the water jet cutting machine with the cutting plane, and perform cutting. When the water jet cutting machine goes around the expansion elbow for one week, the cutting work of the expansion elbow is completed, and it is detected with a combustible gas detector;

[0079] S23: After cutting both ends of the water jet cutting machine, make the expansion elbow an open container, and manually clean the oil stain inside the expansion elbow;

[0080] S24: Use gas cutting to cut the expansion elbow into several sections, each section being 0.5 meters long. Then lower it to the construction platform, use the overhead crane to move it horizontally to the outside of the bridge, and hoist it to the bridge deck by the bridge deck truck crane for unified external transportation to the storage site.

[0081] Figure 7 Among them, 1 of the 3 winches, a 10-ton winch, is used for longitudinal traction, and 2 of the 3-ton winches are used for vertical hoisting. 1 group of longitudinal traction pulleys among the 3 groups of fixed pulleys is arranged in the B1 cross beam at the beam end, and the remaining 2 groups of fixed pulleys are arranged under the C-shaped cross rib, with a pulley spacing of 7.5 meters.

[0082] In S5, the cutting and hoisting method for the straight pipe includes:

[0083] S31: Set several winches for pipeline dragging and hoisting on both sides of the common pier of the bridge, and set several groups of fixed pulleys on the cross beam at the beam end of the bridge;

[0084] S32: Install a roller support for the straight pipe sliding every N meters below the straight pipe;

[0085] S33: Use an angle grinder to cut off the connection between the straight pipe and the bridge connection seat, install a guiding device at the end of the straight pipe, and fix it with high-strength bolts. The towing wire rope of the winch is connected to the end of the pipeline along the guiding device, and the straight pipe is towed along the length direction of the straight pipe to the common pier by the winch;

[0086] S34: Cut the straight pipe into several sections using a water cutter, each section being 10 meters long. Fix the two ends of the straight pipe using steel wire ropes and hoop fasteners respectively, and lower it vertically to the ground by a winch for centralized storage.

[0087] Among them, the roller support is used for the support and guiding of the straight pipe. The roller support includes several rollers. The straight pipe is placed on the rollers, and the rollers facilitate the pulling of the straight pipe.

[0088] The structure of the guiding device is as Figure 8 shown, including a channel steel. The channel steel is connected to the oil pipeline 1 by high-strength bolts. The outside of the channel steel is wrapped with a steel plate, and a lifting eye bolt is fixedly connected to the outside of the steel plate. The traction steel wire rope of the winch is connected through the lifting eye bolt.

[0089] Since the bridge is generally a semi-floating system, the stress influence of the dragging construction of the oil pipeline 1 on the main girder of the whole bridge is relatively uniform. During the dragging construction of the oil pipeline, the opening and closing amount of the expansion joint, the displacement of the upper steel plate of the bearing, and the displacement of the tower top are monitored in real time. If the deformation amount is greater than the calculated value (3 mm), immediately stop dragging and find out the reason to prevent excessive dragging force from causing adverse effects on the structure. In particular, check whether there is any jamming phenomenon between the oil pipeline and the roller support.

[0090] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for demolishing an oil pipeline under a bridge, characterized in that, The oil pipeline includes a number of straight pipes and a number of expansion elbows, and both ends of the expansion elbows are connected to the straight pipes; Demolition method, including the following steps: S1: Construction preparation: A track is fixedly connected under the bridge along the length direction of the bridge, and a truss crane is slidably connected to the track. Use the truss crane to build a construction platform at the expansion elbow; S2: Steam purging of the pipeline: Steam purging and warming the pipeline to wake up the oil stored in the oil pipeline; S3: Nitrogen pigging to clean the pipeline: Clean and empty the oil pipeline through a pigging ball; S4: Cutting and hoisting of the expansion elbow: After the oil pipeline is cleaned and emptied, check the construction platform, truss crane and track built at the expansion elbow, re-reinforce the rusted and weld-cracked parts, cut the expansion elbow with a water jet, and then hoist the cut expansion elbow; In S4, the cutting and hoisting method of the expansion elbow includes: S21: Use a chain block and a hoop to hang the expansion elbow under the transverse rib of the main beam of the bridge; S22: Use a wire brush to clean the rust and debris at the cutting part of the expansion elbow. After cleaning, install a flexible track and a water jet cutting machine, adjust the vertical adjustment shaft, align the axis of the nozzle of the water jet cutting machine with the cutting plane, and perform cutting. When the water jet cutting machine goes around the expansion elbow for one week, the cutting work of the expansion elbow is completed, and it is detected with a combustible gas detector; S23: After cutting both ends of the water jet cutting machine, make the expansion elbow an open container, and manually clean the oil stain inside the expansion elbow; S24: Cut the expansion elbow into several sections by gas cutting, then lower it to the construction platform, use the truss crane to move it horizontally to the outside of the bridge, and hoist it to the bridge deck by a truck-mounted crane on the bridge deck and transport it to the storage site uniformly; S5: Cutting and hoisting of the straight pipe: Remove the connection seat between the straight pipe and the bridge, install guiding devices at both ends of the straight pipe, and use a winch to tow the straight pipe along the length direction of the straight pipe to the outside of the bridge. During the demolition process, the straight pipes on both sides of the bridge are removed symmetrically section by section at the same time.

2. A method for removing an oil pipeline under a bridge according to claim 1, characterized in that, In S2, a flange blanking plate is fixedly connected to the end of the intake end of the oil pipeline. The flange blanking plate is provided with a through hole, and a steam inlet pipe is fixedly connected in the through hole. The steam inlet pipe is connected to the oil pipeline. The steam inlet pipe includes a steam inlet and a drain port.

3. A method for removing an oil pipeline under a bridge according to claim 2, characterized in that, In S2, a flange blanking plate is fixedly connected to the end of the outlet end of the oil pipeline. The flange blanking plate is provided with a through hole, and one end of a steam outlet pipe is fixedly connected in the through hole. The steam outlet pipe is connected to the oil pipeline. The steam outlet pipe is successively connected with a steam stop valve and a steam trap. The other end of the steam outlet pipe is connected to an oil storage tank.

4. A method for removing an oil pipeline under a bridge according to claim 3, characterized in that, The flange blanking plate is provided with an oil drain hole. The oil storage tank is arranged below the oil drain hole, and the oil drain hole is connected with an oil drain valve; Steam is conveyed into the oil pipeline through the steam inlet pipe. Every T time interval, check the situation of waking up the oil through the oil drain hole. After waking up the oil, open the oil drain valve to drain the oil.

5. A method for removing an oil pipeline under a bridge according to claim 1, characterized in that, In S3, the pigging ball is a water-filled rubber ball. A pig launcher and a pig receiver are respectively arranged on both sides of the oil pipeline. The pig launcher and the pig receiver are both connected with a vent valve and a pressure gauge. The pig receiver includes a blowdown port and an exhaust hole. The blowdown port is connected with a blowdown valve. One side of the pig launcher and the pig receiver can be detachably connected with a blind plate. The pig launcher is communicated with a nitrogen storage tank and a high-pressure pump through a connecting pipe, and the connecting pipe is connected with an inlet valve.

6. The method for removing an oil pipeline under a bridge according to claim 5, characterized in that, The method for purging the pipeline with nitrogen includes: S11: First, open the blind plate on the pig launcher, send the pigging ball into the pig launcher, open the vent valve on the pig launcher for venting, and ensure that the pressure in the pig launcher is 0 through the pressure gauge; S12: Close the vent valves on the pig launcher and the pig receiver, and open the blowdown valve on the pig receiver; S13: Open the outlet valve of the nitrogen storage tank and the high-pressure pump in sequence, inject nitrogen by opening the inlet valve on the connecting pipe, and send the pigging ball; S14: After the first pigging ball reaches the pig receiver, close the inlet valve, close the blowdown valve on the pig receiver, open the vent valve on the pig receiver for pressure relief until the pressure is zero. After completion, open the blind plate of the pig receiver, take out the pigging ball and inspect, describe and record it; S15: Observe the wear, scratches and deformation of the pigging ball, repeat purging the pipeline until no water is discharged from the blowdown port and no sundries are accumulated, which means the cleaning is qualified.

7. A method for removing an oil pipeline under a bridge according to claim 1, characterized in that, In S5, the straight pipe cutting and hoisting method includes: S31: Install a number of winches for pipeline dragging and hoisting on both sides of the common pier of the bridge, and install several groups of fixed pulleys on the end crossbeam of the bridge; S32: Install a roller support for straight pipe sliding every N meters below the straight pipe; S33: Cut off the connection between the straight pipe and the bridge connection seat with an angle grinder, install a guiding device at the end of the straight pipe and fix it with bolts. The traction steel wire rope of the winch is connected to the end of the pipeline along the guiding device, and the straight pipe is pulled to the common pier along the length direction of the straight pipe through the winch; S34: Cut the straight pipe into several sections by water cutting, fix both ends of the straight pipe with steel wire ropes and hoop respectively, and vertically lower it to the ground for centralized storage through the winch.

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