Construction method for new and old pipeline joint in underground old cast iron gas pipeline reconstruction

Abstract

The application discloses a new and old pipeline joint construction method in the reconstruction of underground old cast iron gas pipeline, which is used for connecting a steel new pipeline and a cast iron old pipeline and comprises the following steps: step 1, excavating a soil body of a construction section until the cast iron old pipeline under the ground is completely exposed; step 2, judging the pipeline state of the cast iron old pipeline under the ground of the construction section; if it is a straight pipe section of the cast iron old pipeline, steps 3A to 6A are executed; if it is a connecting section of the cast iron old pipeline, steps 3B to 6B are executed; and the steel new pipeline and the cast iron old pipeline are connected in a gas-tight sealing mode through a steel bearing pipe or a steel insertion pipe. The construction method can be flexibly applied to different pipeline states under the ground of an excavation section, can eliminate the connection hidden danger of two pipelines made of different materials in the reconstruction process of the underground old cast iron gas pipeline and significantly improves the sealing performance and the shearing resistance of the connection between the new pipeline and the old pipeline.

Description

Technical Field

[0001] This invention relates to the field of gas pipeline construction technology, and in particular to a method for constructing pipe joints in the renovation of old underground cast iron gas pipelines. Background Technology

[0002] In existing technologies, common materials for buried gas pipelines of medium and low pressure include cast iron, steel, and polyethylene.

[0003] In the early renovation of (old) cast iron gas pipelines, short flanged or spigot-joint cast iron pipes were generally used as connectors between two sections of cast iron pipe. One end was typically connected to a steel pipe (or polyethylene pipe) using a flange structure, while the other end was connected to the cast iron pipe using a socket or spigot joint (the socket was used for connection to the spigot joint of the cast iron pipe; the spigot joint was used for connection to the socket joint of the cast iron pipe). However, due to the poor sealing performance of the connection method between cast iron pipes, gas leaks were very likely to occur. Therefore, in the current renovation of old underground cast iron gas pipelines, steel pipes or polyethylene pipes are gradually being used to replace cast iron pipes.

[0004] However, various situations may arise during the actual construction of renovating old underground cast iron gas pipelines. For example, there may be situations where it is necessary to cut off the old (cast iron) pipeline. In this case, if existing cast iron flanged or spigot-and-socket short pipes are still used to solve the connection problem between the old and new pipelines (e.g., using flanged connections), weak points in the connection will still be left, posing potential technical risks to the renovated gas pipeline.

[0005] Furthermore, in the specific construction environment of renovating old underground cast iron gas pipelines, a common situation arises: before excavation, the actual condition of the pipeline beneath the surface of the excavation section cannot be clearly known. It's possible that the pipeline beneath the surface is in a connecting section (a socket and spigot connection structure), or it's in a straight section (i.e., a plain straight pipe without a connecting structure). These two different pipeline conditions require different shapes, structures, and sizes of connectors during the subsequent renovation work. This often leads to delays in on-site construction of old underground cast iron gas pipeline renovations due to unsuitable connectors.

[0006] Therefore, how to better solve the connection problem between two different materials of pipelines during the renovation of old underground cast iron gas pipelines, and how to improve the applicability of connectors to adapt to different underground pipeline conditions after excavation, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the present invention provides a construction method for the joint of new and old pipes in the renovation of underground old cast iron gas pipelines. The technical objective is to be flexible to different underground pipeline conditions after excavation, and to improve the connection effect of two different materials of pipes in the renovation of underground old cast iron gas pipelines, especially in terms of sealing and shear resistance.

[0008] To achieve the above objectives, this invention discloses a construction method for connecting new and old pipe joints in the renovation of underground old cast iron gas pipelines, used to connect new steel pipes and old cast iron pipes; including the following steps:

[0009] Step 1: Excavate the soil in the construction section until the old cast iron pipeline under the ground is completely exposed;

[0010] Step 2: Determine the condition of the old cast iron pipeline beneath the ground in the construction section;

[0011] If it is a straight section of the old cast iron pipe, then proceed to steps 3A to 6A;

[0012] If it is a connection section of the old cast iron pipe, then proceed to steps 3B to 6B;

[0013] Step 3A: Cut the straight pipe section of the cast iron to form the cut end of the cast iron pipe;

[0014] Step 4A: Push a steel pressure roller with an outer conical surface into the outer circumference of the broken pipe end; then push in the sealing ring, the isolation ring, and the locking ring in sequence;

[0015] Step 5A: Place a steel socket between the new steel pipe and the old cast iron pipe;

[0016] The steel pipe includes a small-diameter straight pipe section, a large-diameter straight pipe section, and a tapered connecting section with an inner conical surface, all integrally formed.

[0017] The small-diameter straight pipe section is connected to the new steel pipe by welding to form an airtight connection between the steel pipe and the new steel pipe.

[0018] The large-diameter straight pipe section is used to accommodate the broken end of the cast iron pipe;

[0019] The inner conical surface of the tapered connecting section is roughly positioned to fit the outer conical surface of the steel pressure wheel;

[0020] Step 6A: By tightening the fasteners between the steel pressure roller and the tapered connecting section, the sealing ring, the isolation ring, and the locking ring are pressed in sequence to form an airtight connection between the steel bearing pipe and the broken end of the old cast iron pipe;

[0021] This allows the new steel pipe and the old cast iron pipe to achieve an airtight connection through the steel socket.

[0022] Step 3B: Remove the original cast iron insert of the connecting section, retaining the cast iron socket of the connecting section;

[0023] Step 4B: Place a steel insert between the new steel pipe and the cast iron socket;

[0024] The steel cannula comprises an integrally welded straight pipe section and a connector section.

[0025] The welded straight pipe section is connected to the new steel pipe by welding to form an airtight connection between the steel insert and the new steel pipe;

[0026] Step 5B: Push a steel pressure roller with an outer conical surface into the outer circumference of the insertion section; then push in the sealing ring, the isolation ring, and the locking ring in sequence;

[0027] Step 6B: By tightening the fasteners between the steel pressure roller and the cast iron socket, the sealing ring, the isolation ring, and the locking ring are pressed in sequence to form an airtight connection between the steel insert and the cast iron socket of the old cast iron pipe;

[0028] This allows for an airtight connection between the new steel pipe and the old cast iron pipe via the steel insert.

[0029] Furthermore, both the steel socket and the steel insert are wrapped with reinforced 3PE as an anti-corrosion layer.

[0030] Furthermore, the inner diameters of the locking ring, the isolation ring, and the sealing ring are respectively interference-fitted with the outer diameter of the broken pipe end or the insertion section.

[0031] Furthermore, the outer diameter of the locking ring is smaller than the outer diameters of the insulating ring and the sealing ring; the outer diameter of the insulating ring is smaller than the outer diameter of the sealing ring.

[0032] Furthermore, the inner diameter of the small-diameter straight pipe section matches the inner diameter of the new steel pipe.

[0033] The beneficial effects of this invention are:

[0034] The construction method of this invention uses specially shaped steel sockets or steel inserts to connect steel pipes and cast iron pipes. The prefabricated specially shaped steel sockets or steel inserts can be flexibly applied to different pipe conditions under the ground in the excavation section, and can eliminate the potential connection hazards between the old and new pipes of different materials during the renovation of old underground cast iron gas pipelines, significantly improving the sealing performance and shear resistance of the connection between the old and new pipes.

[0035] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0036] Figure 1 This diagram illustrates the connection structure between the steel pipe and the broken end of the old cast iron pipe in this invention.

[0037] Figure 2 It shows Figure 1 A schematic diagram of the structure of the pressure roller manufactured by China Steel Corporation.

[0038] Figure 3 It shows Figure 1 A structural schematic diagram of Sinosteel's pipe-bearing structure.

[0039] Figure 4 This diagram illustrates the connection structure between the steel insert and the cast iron socket of the old cast iron pipe in this invention.

[0040] Figure 5 It shows Figure 1 A schematic diagram of the structure of the steel cannula. Detailed Implementation

[0041] A specific embodiment of the construction method for the joint between old and new pipes in the renovation of underground old cast iron gas pipelines according to the present invention.

[0042] The construction method of this invention is mainly applied to the renovation of old underground cast iron gas pipelines, connecting new steel pipelines to old cast iron pipelines underground; it includes the following steps:

[0043] Step 1: Excavate the soil in the construction section until the old cast iron pipeline under the ground is completely exposed;

[0044] Step 2: Determine the condition of the old cast iron pipelines underground in the construction section;

[0045] If it is a straight section of an old cast iron pipe (i.e., a regular straight pipe without a socket joint), then proceed to steps 3A to 6A.

[0046] If it is a connection section of an old cast iron pipe (i.e., a joint with a socket), then proceed to steps 3B to 6B.

[0047] Specifically, when the excavated section of soil is followed by a straight section of an old cast iron pipeline (i.e., a standard straight pipe without a socket joint) below the ground, then see [reference needed]. Figure 1 As shown, in step 3A, the straight section of the old cast iron pipe is cut off, and a cut-off end A1 (also known as a "spigot") is formed in cast iron material after the pipe cutting operation.

[0048] Step 4A: On the outer circumference of the cut pipe end A1, push a steel pressure roller 51 with an outer conical surface (see...) towards the old pipe. Figure 2 (as shown); then push in the sealing ring 52, the isolation ring 53, and the locking ring 54 in sequence.

[0049] Preferably, the inner diameters of the locking ring 54, the isolation ring 53, and the sealing ring 52 are respectively interference-fitted with the outer diameter of the broken pipe end A1 to ensure airtight performance.

[0050] Preferably, the outer diameter of the sealing ring 52 is larger than the outer diameter of the isolation ring 53; the outer diameter of the locking ring 54 is smaller than the outer diameters of the isolation ring 53 and the sealing ring 52. Such dimensions facilitate the assembly of these components.

[0051] Step 5A: Place a steel socket 1 between the new steel pipe A2 and the broken end A1 of the old cast iron pipe; preferably, the steel socket 1 is wrapped with reinforced 3PE as an anti-corrosion layer to improve its anti-corrosion performance.

[0052] See Figure 3 As shown, the steel pipe 1 in this invention includes a small-diameter straight pipe section 11, a large-diameter straight pipe section 12, and a tapered connecting section 13 with an inner conical surface, all integrally formed.

[0053] The small-diameter straight pipe section 11 is connected to the new steel pipe A2 by welding to form an airtight connection between the steel socket 1 and the new steel pipe A2. Preferably, the inner diameter of the small-diameter straight pipe section 11 matches the inner diameter of the new steel pipe A2 to reduce gas flow resistance and ensure good gas flow within the pipe.

[0054] The large-diameter straight pipe section 12 is used to accommodate the broken end A1 of the old cast iron pipe.

[0055] The inner conical surface of the tapered connecting section 13 forms a rough positioning fit with the outer conical surface of the steel pressure roller 51, which plays a certain guiding role in the subsequent back pressure process of the steel pressure roller 51.

[0056] Step 6A: By tightening the fasteners 3 (in this embodiment, a bolt and nut connection structure is used) between the steel pressure roller 51 and the tapered connecting section 13, the sealing ring 52, the isolation ring 53, and the locking ring 54 are tightened in sequence to form an airtight connection between the steel bearing pipe 1 and the broken end A1 of the old cast iron pipe.

[0057] By employing the above-mentioned construction steps in conjunction with the steel pipe of this invention, and considering the situation where there is a cast iron straight pipe section below the ground after the excavation of the construction section, the construction method of this invention can quickly achieve an airtight connection between the new steel pipe and the old cast iron pipe, which has the advantages of short construction period, reliable and stable airtight performance, and stronger pipe shear resistance.

[0058] Specifically, if after excavating the construction section, the underground portion contains the connection section of an old cast iron pipeline (i.e., the location with a socket joint), then refer to... Figure 4 As shown, perform step 3B: remove the original cast iron insert of the connecting section (not shown in the figure), and retain the cast iron socket A3 of the connecting section;

[0059] Step 4B: Place a steel insert 2 between the new steel pipe A2 and the cast iron socket A3; furthermore, the steel insert 2 is wrapped with reinforced 3PE as an anti-corrosion layer to improve its anti-corrosion performance.

[0060] See Figure 5 As shown, the steel insertion tube 2 in this invention includes an integrally formed welded straight pipe section 21 and an insertion section 22;

[0061] The welded straight pipe section 21 is connected to the new steel pipe A2 by welding to form an airtight connection between the steel insert 2 and the new steel pipe A2. Preferably, the inner diameter of the welded straight pipe section 21 matches the inner diameter of the new steel pipe A2 to reduce gas flow resistance and ensure good gas flow within the pipe.

[0062] Step 5B: On the outer circumference of the insertion section 22, in the direction of the new steel pipe A2, push in a steel pressure roller 51 with an outer conical surface; then push in the sealing ring 52, the isolation ring 53, and the locking ring 54 in sequence.

[0063] Preferably, the inner diameters of the locking ring 54, the isolation ring 53, and the sealing ring 52 are respectively interference-fitted with the outer diameter of the insertion section 22 to ensure airtight performance.

[0064] Step 6B: By tightening the fasteners 3 between the steel pressure roller 51 and the cast iron socket A3, the sealing ring 52, the isolation ring 53, and the locking ring 54 are pressed in sequence to form an airtight connection between the steel insert 2 and the cast iron socket A3 of the old cast iron pipe.

[0065] By employing the above-mentioned construction steps in conjunction with the steel pipe of this invention, and considering the situation where the underground section after excavation is a cast iron connection section, the construction method of this invention can quickly achieve an airtight connection between the new steel pipe and the old cast iron pipe. It has the advantages of short construction period, reliable and stable airtight performance, and stronger pipe shear resistance.

[0066] In summary, the construction method of this invention utilizes specially shaped steel sockets or steel inserts to achieve an airtight connection between new steel pipelines and old cast iron pipelines. The prefabricated, specially shaped steel sockets or steel inserts are flexible enough to adapt to different pipeline conditions underground in the excavation section, and can eliminate potential connection hazards between new and old pipelines of different materials during the renovation of old underground cast iron gas pipelines, significantly improving the sealing performance and shear resistance at the connection point.

[0067] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. Construction method for connecting new and old pipe joints in the renovation of old underground cast iron gas pipelines; used to connect new steel pipes and old cast iron pipes; including the following steps: Step 1: Excavate the soil in the construction section until the old cast iron pipeline under the ground is completely exposed; Step 2: Determine the condition of the old cast iron pipeline beneath the ground in the construction section; If it is a straight section of the old cast iron pipe, then proceed to steps 3A to 6A; If it is a connection section of the old cast iron pipe, then proceed to steps 3B to 6B; Step 3A: Cut the straight pipe section of the cast iron to form the cut end of the cast iron pipe; Step 4A: Push a steel pressure roller with an outer conical surface into the outer circumference of the broken pipe end; then push in the sealing ring, the isolation ring, and the locking ring in sequence; Step 5A: Place a steel socket between the new steel pipe and the old cast iron pipe; The steel pipe includes a small-diameter straight pipe section, a large-diameter straight pipe section, and a tapered connecting section with an inner conical surface, all integrally formed. The small-diameter straight pipe section is connected to the new steel pipe by welding to form an airtight connection between the steel pipe and the new steel pipe. The large-diameter straight pipe section is used to accommodate the broken end of the cast iron pipe; The inner conical surface of the tapered connecting section is roughly positioned to fit the outer conical surface of the steel pressure wheel; Step 6A: By tightening the fasteners between the steel pressure roller and the tapered connecting section, the sealing ring, the isolation ring, and the locking ring are pressed in sequence to form an airtight connection between the steel bearing pipe and the broken end of the old cast iron pipe; This allows the new steel pipe and the old cast iron pipe to achieve an airtight connection through the steel socket. Step 3B: Remove the original cast iron insert of the connecting section, retaining the cast iron socket of the connecting section; Step 4B: Place a steel insert between the new steel pipe and the cast iron socket; The steel cannula comprises an integrally welded straight pipe section and a connector section. The welded straight pipe section is connected to the new steel pipe by welding to form an airtight connection between the steel insert and the new steel pipe; Step 5B: Push a steel pressure roller with an outer conical surface into the outer circumference of the insertion section; then push in the sealing ring, the isolation ring, and the locking ring in sequence; Step 6B: By tightening the fasteners between the steel pressure roller and the cast iron socket, the sealing ring, the isolation ring, and the locking ring are pressed in sequence to form an airtight connection between the steel insert and the cast iron socket of the old cast iron pipe; This allows for an airtight connection between the new steel pipe and the old cast iron pipe via the steel insert.

2. The construction method for the joint between old and new pipelines in the renovation of underground old cast iron gas pipelines according to claim 1, characterized in that, Both the steel socket and the steel insert are wrapped with 3PE as a reinforced anti-corrosion layer.

3. The construction method for the joint between old and new pipes in the renovation of underground old cast iron gas pipelines according to claim 1 or 2, characterized in that, The inner diameters of the locking ring, the isolation ring, and the sealing ring are respectively interference-fitted with the outer diameter of the broken pipe end or the insertion section.

4. The construction method for the joint between old and new pipelines in the renovation of underground old cast iron gas pipelines according to claim 3, characterized in that, The outer diameter of the locking ring is smaller than the outer diameters of the insulating ring and the sealing ring; the outer diameter of the insulating ring is smaller than the outer diameter of the sealing ring.

5. The construction method for the joint between old and new pipes in the renovation of underground old cast iron gas pipelines according to claim 1 or 2, characterized in that, The inner diameter of the small-diameter straight pipe section matches the inner diameter of the new steel pipe.

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