A method for opening a large-diameter gas pipeline under pressure

Abstract

The present invention relates to a method for hot-dip tapping of large-diameter gas pipelines, comprising the following steps: Step 1: Construction preparation and pipe wall thickness verification; Step 2: Welding of branch saddle short pipes; Step 3: Installation of a sector-shaped blind plate valve and a tapping tool; Step 4: Nitrogen displacement and sealing test; Step 5: Pressure cutting of the main pipe to open a hole; Step 6: Closing the sector-shaped blind plate valve and removing the tapping tool. By combining the sector-shaped blind plate valve with the tapping tool, the present invention enables the connection of new gas pipelines to a large gas pipeline network while maintaining normal operation. Safety measures such as pipe wall thickness verification ensure the safety and reliability of the hot-dip tapping process.

Description

Technical Field

[0001] The invention relates to the technical field of industrial installation, in particular to a method for opening a large-diameter gas pipeline under pressure. Background Art

[0002] To meet market demand and further increase production capacity, industries such as metallurgy, refining, and chemical engineering are gradually optimizing their industrial structures through renovation and expansion projects based on existing facilities. This involves extensive pipeline interconnection and connection work between new and existing facilities, significantly disrupting the normal production and operation of existing facilities. Gas, the primary energy source in large industrial parks, often requires shutting down gas pipelines and replacing them with nitrogen before drilling can begin. This not only wastes significant resources and construction costs, but also impacts the normal operation of various user facilities within the gas network. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for opening a large-diameter gas pipeline under pressure. By using a fan-shaped blind plate valve in conjunction with a hole opener, a new gas pipeline network can be connected to the large-scale gas pipeline network under the premise of normal operation. Safety measures such as pipeline wall thickness verification ensure that the opening process under pressure is safe and reliable.

[0004] The technical solution adopted by the present invention to solve the technical problem is to provide a method for tapping a large-diameter gas pipeline under pressure, which specifically includes the following steps:

[0005] Step 1: Construction preparation and pipe wall thickness verification;

[0006] Make a short branch saddle pipe with a height H controlled at 100-150mm. Pre-install and check whether the gap between the branch pipe saddle surface and the main pipe contact surface is in good contact. At the same time, check the main pipe wall thickness. When the pressure P for pressurized welding is greater than the designed operating pressure, pressurized welding is allowed. The formula is as follows: P = 2δ(tC)F / D.

[0007] P-the pressure of the operating pipeline allowed for pressurized welding (MPa);

[0008] δ- minimum yield strength of pipe (MPa);

[0009] t-actual wall thickness of the pipe at the welding point (mm);

[0010] C—Wall thickness correction caused by welding (mm);

[0011] D—outer diameter of the pipe (mm);

[0012] F—safety factor, 0.5 for gas pipelines;

[0013] Step 2: Weld the branch saddle short pipe;

[0014] Weld the prepared branch saddle short pipe to the designated position of the main pipe;

[0015] Step 3: Install the fan-shaped blind plate valve and hole opener;

[0016] The fan-shaped blind plate valve is fixed to the branch saddle short pipe with a flange, and the hole opener cylinder flange is fixedly connected to the fan-shaped blind plate valve;

[0017] Step 4: Nitrogen replacement and sealing test;

[0018] Open the fan-shaped blind plate valve to make the branch saddle short pipe, fan-shaped blind plate valve, and hole opener form a whole. Use the nitrogen bottle to fill 0.1MPa nitrogen into the chamber through the hole opener ventilation valve to conduct a sealing test. After passing the test, open the hole opener ventilation valve to empty the nitrogen in the chamber. Use the nitrogen bottle to fill the chamber with 0.1MPa nitrogen again to reduce the oxygen content in the chamber to below 1%;

[0019] Step 5: Press and cut the main pipe opening;

[0020] Step 6: Close the fan-shaped blind plate valve and remove the hole opener;

[0021] After lifting the hole opener cutter to the sector blind valve, use the hole opener center positioning drill to bring the cut pipe wall out to the sector blind valve, close the sector blind valve, empty the gas in the hole opener, remove the connecting flange between the hole opener and the sector blind valve, and install the blind plate behind the valve.

[0022] As a supplement to the technical solution described in the present invention, in the step 2, when installing the branch saddle short pipe, it is necessary to ensure that the flange surface is parallel to the pipe to be drilled, the deviation shall not be greater than 1mm, the welding current should not be too large, and after welding is completed, PT is performed to detect the quality of the fillet weld.

[0023] As a supplement to the technical solution described in the present invention, in the step three, when the fan-shaped blind plate valve is opened, the valve disc can be completely retracted into the valve chamber to ensure that the cylinder knife of the hole opener can pass through the valve chamber freely.

[0024] As a supplement to the technical solution described in the present invention, the specific steps of step five are as follows: start the hole opener to perform pressure hole opening operation. During the hole opening process, the feed speed must be uniform to avoid damaging the cutter head; then adjust the hole opener cylinder knife distance to cut the pipe wall. The pipe cutting surface is an arc surface, and the cutting is intermittent cutting. The contact surface between the cylinder knife and the running pipe must be uniform to prevent bending; when the hole opener cylinder knife runs to the predetermined size, it stops, and then manually operate the hole opener to advance the cylinder knife about 5 mm to confirm that the pipe wall has been completely cut. The tool must not be retracted directly.

[0025] As a supplement to the technical solution described in the present invention, in the step five, when the positioning drill bit drills through the pipeline and the hole opener pressure gauge displays, each connection point is checked with a CO alarm. If leakage is found, the hole opener connection plate bolts must be further tightened until there is no leakage.

[0026] Beneficial effects: The present invention relates to a method for tapping a large-diameter gas pipeline under pressure, which has the following advantages:

[0027] 1. The use of sector blind plate valves in conjunction with hole openers for opening holes in gas pipelines ensures the sealing of newly added gas branches while ensuring the safe advance and retreat of the hole opener's cutter. Furthermore, the normal operation of the main gas pipeline network is not affected during the hole opening process.

[0028] 2. By checking the wall thickness of the main gas pipeline and replacing the air in the hole opener chamber, the safety of the gas pipeline opening process is further guaranteed. By adjusting the size of the hole opener cylinder, it can adapt to the opening operation of gas pipelines with multiple diameters, and the cutting efficiency and safety are higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a construction flow chart of the present invention;

[0030] Figure 2 It is a structural schematic diagram of the present invention. DETAILED DESCRIPTION

[0031] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0032] The embodiment of the present invention relates to a method for opening a large-diameter gas pipeline under pressure, such as Figure 1-2 As shown, the specific steps include:

[0033] Step 1: Construction preparation and pipe wall thickness verification;

[0034] Make a branch saddle short pipe 2, with the short pipe height H controlled at 100-150mm. Pre-install and check whether the gap between the branch pipe saddle surface and the main pipe 1 is in good contact. At the same time, check the wall thickness of the main pipe 1. When the pressure P for pressurized welding is greater than the designed operating pressure, pressurized welding is allowed. The formula is as follows: P = 2δ(tC)F / D;

[0035] P-the pressure of the operating pipeline allowed for pressurized welding (MPa);

[0036] δ- minimum yield strength of pipe (MPa);

[0037] t-actual wall thickness of the pipe at the welding point (mm);

[0038] C—Wall thickness correction caused by welding (mm);

[0039] D—outer diameter of the pipe (mm);

[0040] F—safety factor, 0.5 for gas pipelines;

[0041] Step 2: Weld the branch saddle short pipe 2;

[0042] Weld the prepared branch saddle short pipe 2 to the designated position of the main pipe 1. When installing the branch saddle short pipe 2, ensure that the flange surface is parallel to the pipe to be drilled, with a deviation of no more than 1mm. The welding current should not be too large. After welding is completed, perform PT to test the quality of the fillet weld.

[0043] Step 3: Install the fan-shaped blind plate valve 3 and the hole opener 4;

[0044] When the fan-shaped blind plate valve 3 is opened, the valve disc can be completely retracted into the valve chamber 6, ensuring that the cylinder knife 5 of the hole opener 4 can freely pass through the valve chamber 6; the fan-shaped blind plate valve 3 is fixed to the branch saddle short pipe 2 with a flange, and the cylinder flange of the hole opener 4 is fixedly connected to the fan-shaped blind plate valve 3;

[0045] Step 4: Nitrogen replacement and sealing test;

[0046] Open the fan-shaped blind plate valve 3 to make the branch saddle short pipe 2, the fan-shaped blind plate valve 3, and the hole opener 4 form a whole. Use the nitrogen bottle to fill the chamber with 0.1MPa nitrogen through the hole opener ventilation valve 8. After the sealing test is passed, open the hole opener ventilation valve 8 to exhaust the nitrogen in the chamber. Use the nitrogen bottle to fill the chamber with 0.1MPa nitrogen again to reduce the oxygen content in the chamber to below 1%;

[0047] Step 5: Press and cut the main pipe 1 to open a hole;

[0048] Start the hole opener 4 to perform the pressure hole opening operation. During the hole opening process, the feed speed should be uniform to avoid damaging the cutter head. When the positioning drill bit drills through the pipe and the hole opener pressure gauge 7 shows a display, use the CO alarm to check each connection point. If leakage is found, the hole opener 4 connection plate bolts must be further tightened until there is no leakage. Then adjust the hole opener barrel cutter 5 distance to cut the pipe wall. The pipe cutting surface is an arc surface and the cutting is intermittent. The contact surface between the barrel cutter 5 and the running pipe must be uniform to prevent bending. When the barrel cutter 5 of the hole opener 4 runs to the predetermined size, stop the machine, and then manually operate the hole opener 4 to advance the barrel cutter 5 about 5 mm to confirm that the pipe wall has been completely cut. The tool must not be directly retracted.

[0049] Step 6: Close the fan-shaped blind plate valve 3 and remove the hole opener 4;

[0050] After lifting the hole opener cutter 5 to the sector blind valve 3, use the center positioning drill of the hole opener 4 to bring the cut pipe wall out to the sector blind valve 3, close the sector blind valve 3, empty the gas in the hole opener 4, remove the connecting flange between the hole opener 4 and the sector blind valve 3, and install the blind plate behind the valve.

[0051] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0052] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0053] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0054] The above is a detailed introduction to a method for pressure-opening a large-diameter gas pipeline provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core ideas of the present application. At the same time, for those skilled in the art, according to the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A method for tapping a large-diameter gas pipeline under pressure, characterized by: The specific steps include: Step 1: Construction preparation and pipe wall thickness verification; Make a branch saddle short pipe (2), and control the short pipe height H to be 100-150mm. Pre-install and check whether the gap between the branch pipe saddle surface and the main pipe (1) is in good contact. At the same time, check the wall thickness of the main pipe (1). When the pressure P of the pressure welding is greater than the design operating pressure, the pressure welding is allowed. The formula is as follows: P = 2δ(tC)F / D; P-the pressure of the running pipeline allowed for pressure welding; δ- minimum yield limit of pipe; t-actual wall thickness of the pipe at the welding point; C—Wall thickness correction caused by welding; D—outer diameter of the pipe; F—safety factor, 0.5 for gas pipelines; Step 2: Welding the branch saddle short pipe (2); Weld the prepared branch saddle short pipe (2) to the designated position of the main pipe (1); Step 3: Install the fan-shaped blind plate valve (3) and the hole opener (4); The fan-shaped blind plate valve (3) is fixed to the branch saddle short pipe (2) by a flange connection, and the cylinder flange of the hole opener (4) is fixedly connected to the fan-shaped blind plate valve (3); Step 4: Nitrogen replacement and sealing test; Open the fan-shaped blind plate valve (3) to make the branch saddle short pipe (2), the fan-shaped blind plate valve (3) and the hole opener (4) form a whole. Fill the chamber with 0.1MPa nitrogen gas using a nitrogen bottle through the hole opener ventilation valve (8). After the sealing test is passed, open the hole opener ventilation valve (8) to empty the nitrogen in the chamber. Fill the chamber with 0.1MPa nitrogen gas again using the nitrogen bottle to reduce the oxygen content in the chamber to below 1%; Step 5: Press and cut the main pipe (1) to open a hole; Step 6: Close the fan-shaped blind plate valve (3) and remove the hole opener (4); After the hole opener knife (5) is lifted to the sector blind plate valve (3), the cut pipe wall is brought out to the sector blind plate valve (3) using the center positioning drill of the hole opener (4), and the sector blind plate valve (3) is closed. The gas in the hole opener (4) is evacuated, the connecting flange between the hole opener (4) and the sector blind plate valve (3) is removed, and the rear blind plate of the valve is installed.

2. A method for tapping a large-diameter gas pipeline under pressure according to claim 1, characterized in that: In the step 2, when installing the branch saddle short pipe (2), it is necessary to ensure that the flange surface is parallel to the pipe to be drilled, the deviation shall not be greater than 1mm, and the welding current shall not be too large. After the welding is completed, the quality of the fillet weld is tested by PT.

3. The method for tapping a large-diameter gas pipeline under pressure according to claim 1, characterized in that: In the step 3, when the fan-shaped blind plate valve (3) is opened, the valve disc can be completely retracted into the valve chamber (6), ensuring that the cylindrical knife (5) of the hole opener (4) can freely pass through the valve chamber (6).

4. The method for tapping a large-diameter gas pipeline under pressure according to claim 1, characterized in that: The specific steps of step five are as follows: start the hole opener (4) to perform the hole opening operation under pressure. During the hole opening process, the feed speed must be uniform to avoid damaging the cutter head; then adjust the distance of the hole opener tube knife (5) to cut the pipe wall. The pipe cutting surface is an arc surface, and the cutting is intermittent cutting. The contact surface between the tube knife (5) and the running pipe must be uniform to prevent bending; when the tube knife (5) of the hole opener (4) runs to the predetermined size, stop the machine, and then manually operate the hole opener (4) to make the tube knife (5) advance 5mm to confirm that the pipe wall has been completely cut. The tool must not be directly retracted.

5. A method for tapping a large-diameter gas pipeline under pressure according to claim 4, characterized in that: In the step 5, when the positioning drill bit drills through the pipeline and the hole opener pressure gauge (7) shows a display, each connection point is checked with a CO alarm. If leakage is found, the hole opener (4) connection plate bolts must be further tightened until there is no leakage.

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