Ductile cast iron micro-top pipe and pouring forming structure thereof

Abstract

The utility model discloses a nodular cast iron micro-top pipe and pouring forming structure thereof relates to pipeline technical field, aims at solving the problem of big investment of traditional micro-top pipe mould, pipe source ellipse sensitivity, sleeve no protection and poor length adaptability. Micro-top pipe includes cutting into target length and the double pipe section of inserting pipe of cement mortar lining of inner wall being equipped, and its one end sleeve area sealing rubber ring, the double bearing sleeve of support block, the outer glass steel protection cover of common sleeve, the annular cavity of three interstices fills cement mortar and forms the protective layer. Forming method is: cutting pipe source and assembling pipe body foundation, install outer glass steel protection cover, through the concentric positioning of support block and positioning pin, install the plug after pouring cement mortar, steam health care solidification. The utility model does not need to customize mould, adapts the short pipe demand of special site, and the corrosion and wear resistance are strong, and the production efficiency and product life are improved.

Description

Technical Field

[0001] This utility model relates to the field of pipeline technology, specifically to a ductile iron micro-jacking pipe and its casting and molding structure. Background Technology

[0002] One important application of ductile iron pipes is trenchless construction, which involves laying and replacing ductile iron pipelines without excavating the surface. Trenchless construction offers advantages such as environmental friendliness and minimal disruption to traffic. Ductile iron pipe jacking primarily involves casting and curing a layer of high-strength, wear-resistant concrete over the ductile iron pipe. This concrete layer effectively protects the external anti-corrosion coating of the ductile iron pipe from damage during jacking. Furthermore, the internal steel reinforcement within the concrete layer further enhances its strength and ensures excellent adhesion between the concrete layer and the outer wall of the ductile iron pipe. Due to these advantages, ductile iron jacking is increasingly used in urban areas, historical sites, agricultural and vegetation protection zones, and for crossing highways and railways. These applications lead to varying lengths of ductile iron jacking pipes, requiring customized production based on site conditions. Traditionally, the effective length of ductile iron pipes is primarily 6 meters, largely driven by market demand. For pipe jacking production, a single 6m length cannot meet all needs, especially when there is not enough space in special sites and only 1m or 2m micro-jacking pipes can be used.

[0003] Traditional micro-jacking pipe production processes involve casting first and then assembling. Casting requires a large investment in molds, and the molds and pipe sections are susceptible to elliptical deformation during assembly, leading to issues such as inability to fit and material leakage, affecting production efficiency and product appearance quality. After the cast semi-finished product and sleeve are installed, the outer surface of the entire sleeve lacks a cement mortar outer protective layer, making the anti-corrosion coating prone to damage during jacking construction, thus affecting the service life of the micro-jacking pipe. This utility model mainly designs a new casting and molding method for ductile iron micro-jacking pipes, eliminating the need for mold investment, being insensitive to the ellipticity of the pipe source, and ensuring that the entire finished product is protected by a cement mortar outer protective layer and a fiberglass pipe outer sheath, effectively guaranteeing wear resistance and service life. Utility Model Content

[0004] The purpose of this invention is to provide a ductile iron micro-jacking pipe and its casting structure to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a casting and molding structure for ductile iron micro-jacking pipes, comprising double-insertion pipe segments cut to target lengths, one end of each double-insertion pipe segment being fitted with a double-bearing sleeve, the double-bearing sleeve and the double-insertion pipe segments being fitted together with an outer fiberglass protective sleeve, the annular cavity formed between the outer fiberglass protective sleeve, the double-bearing sleeve and the double-insertion pipe segments being filled with cement mortar, the outer fiberglass protective sleeve being kept coaxial with the double-insertion pipe segments by a coaxial positioning structure, and a plug being fitted at the bottom end of the outer fiberglass protective sleeve for sealing the annular cavity.

[0006] Preferably, the coaxial positioning structure includes multiple support blocks and positioning pins. The support blocks are evenly distributed in the middle of the double-bearing sleeve. The inner wall of the outer fiberglass protective sleeve abuts against the support blocks. The side wall of the positioning pin is provided with a socket. The top of the outer fiberglass protective sleeve is inserted into the socket. The end of the positioning pin abuts against the inner wall of the double-insertion tube section.

[0007] Preferably, the plug includes a plug shell and a plug rubber component. The outer fiberglass protective sleeve is inserted into the plug shell and sealed by the plug rubber component. The plug rubber component is an inflatable rubber tire that expands when inflated and wraps around the outer fiberglass protective sleeve.

[0008] This utility model also provides a ductile iron pipe formed by the above-mentioned casting structure, as follows:

[0009] The ductile iron micro-jacking pipe includes a double-insertion pipe section, a double-sleeve sleeve, and an outer fiberglass protective sleeve. The inner wall of the double-insertion pipe section is lined with cement mortar, and the annular cavity is filled with cement mortar to form a cement mortar protective layer.

[0010] A sealing ring is installed inside the socket of the double-socket sleeve. The sealing ring fills the gap between the socket and the double-socket section, thus providing a seal.

[0011] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0012] 1. This utility model constructs a composite structure of "inner double-insertion pipe section + middle cement mortar protective layer + outer fiberglass protective sleeve". Compared with the traditional micro-jacking pipe design that only relies on the pipe body itself for corrosion protection and has no protection outside the sleeve, it achieves all-dimensional protection of "internal protection against media corrosion and external protection against construction friction and underground environment erosion".

[0013] 2. The plug at the socket of the double-socket sleeve can completely seal the gap between the sleeve and the double-insertion pipe section, preventing leakage of the medium inside the pipe during pouring. The support block on the outer wall of the double-socket sleeve cooperates with the positioning pin at the end of the pipe body to achieve concentric positioning of the entire pipe foundation and the outer fiberglass protective sleeve, ensuring uniform filling of cement mortar in the annular cavity and avoiding hidden dangers such as uneven local stress and cracking of the protective layer caused by eccentricity. Attached Figure Description

[0014] Figure 1 This is a cross-sectional view of a ductile iron micro-jacking pipe.

[0015] Figure 2 A schematic diagram of ductile iron micro-jacking pipe casting;

[0016] Figure 3 This is a schematic diagram of the positioning pin structure;

[0017] Figure 4 This is a schematic diagram of the plug structure.

[0018] In the diagram: 1. Double-insertion pipe section; 2. Cement mortar protective layer; 3. Outer fiberglass protective sleeve; 4. Cement mortar inner lining; 5. Double-bearing sleeve; 6. Sealing ring; 7. Support block; 8. Plug shell; 9. Plug rubber part; 10. Positioning pin; 11. Socket. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] The ductile iron micro-jacking pipe described in this embodiment is suitable for municipal trenchless construction scenarios (such as narrow urban roads, historical site protection areas, and underpasses under highways). Especially for micro-jacking pipes requiring short lengths such as 1m and 2m, its overall structure adopts a three-layer integrated design of "inner pipe body + intermediate protective layer + outer sheath." Specific components and specifications are as follows (in conjunction with...). Figure 1 (Sectional view)

[0021] The double-insertion pipe section 1 is made of QT450-10 ductile iron. The original pipe length is 6m (market standard pipe source). After cutting, the target length is 1m / 2m. The outer diameter is DN300-DN1000 (suitable for commonly used municipal pipe diameters). As the core load-bearing component, it undertakes the jacking force and media transportation function in pipe jacking construction.

[0022] The cement mortar lining 4 uses cement, sand and water to make cement mortar with a thickness of 4mm-6mm. It is prefabricated on the inner wall of the double-insertion pipe section (the pipe source comes with the pipe itself) to prevent the corrosion of the ductile iron pipe by the medium inside the pipe (such as water and sewage) and improve the smoothness of the inner wall.

[0023] The double-sleeve sleeve 5 is made of QT450-5 material, with a diameter matching the double-insertion pipe section and a length of 150mm. It is a key component for connecting adjacent micro-jacking pipes, enabling rapid docking between pipe sections.

[0024] The sealing ring 6 is made of nitrile rubber or styrene-butadiene rubber with a rectangular cross-section. One ring is provided for each set of double-sleeve sleeves. It is used to seal between the double-sleeve sleeve and the double-insertion pipe section during assembly to prevent leakage of the medium inside the pipe.

[0025] The support block 7 and the double-bearing sleeve 5 are integrally formed. The outer fiberglass protective sleeve 3 is evenly distributed around the center of the outer wall of the double-bearing sleeve to ensure the concentricity of the pipe foundation and the outer sleeve and to ensure the uniform thickness of the annular cavity.

[0026] The outer fiberglass protective sleeve is made of glass fiber reinforced plastic, using a composite molding process of "glass fiber + epoxy resin". The outer layer provides corrosion and wear-resistant protection, resisting soil friction and underground corrosive media erosion during construction.

[0027] The cement mortar protective layer 2 uses M30 strength grade cement mortar as an intermediate structural layer to enhance the overall rigidity of the pipe body and protect the anti-corrosion coating on the outer wall of the double-insertion pipe section from damage by the jacking force.

[0028] The plug includes a plug shell 8 and a plug rubber part 9. The plug shell 8 is made of steel and its inner diameter matches the outer diameter of the outer fiberglass protective sleeve 3. The plug rubber part 9 is 3mm thick and seals the bottom of the outer protective sleeve during pouring to prevent cement mortar leakage.

[0029] The positioning pin 10 has a socket 11 at one end, with a total of 4 pins. The top of the outer fiberglass protective sleeve 3 is inserted into the socket 11. The other end of the positioning pin 10 abuts against the outer wall of the double-insertion pipe section 1 to fix the concentricity of the pipe body base socket end and the outer protective sleeve. It works with the support block 7 to achieve concentric positioning of the entire pipe section.

[0030] The specific steps of the above-mentioned method for casting and molding ductile iron micro-jacking pipes are as follows:

[0031] This embodiment takes "a DN400 ductile iron micro-jacking pipe with a target length of 1m" as an example to explain the molding process in detail. The equipment required includes: plasma cutter, rubber hammer, steam curing room, measuring tape, level, etc.

[0032] S1: Pipe preparation and assembly (forming the foundation of the pipe body)

[0033] Pipe cutting: Select a 6m long DN400 standard ductile iron pipe (with a 4mm thick cement mortar lining on the inner wall). According to the construction drawings, use a plasma cutter to cut it into 0.98m long double-insertion pipe sections 1. After cutting, chamfer the edges and grind the burrs at both ends of the pipe section with an angle grinder to ensure that the end face is flat and to avoid damaging the sealing rings to be installed later.

[0034] Pre-treatment of double-bearing sleeve: Take DN400 ductile iron double-bearing sleeve 5, clean the inside of the sleeve assembly end to ensure it is clean; install the rubber ring 6 into the socket of sleeve 1, press along the circumference of the rubber ring with your fingers to ensure that the rubber ring is completely in contact with the groove wall without twisting or protrusion.

[0035] Pipe assembly: Slowly insert one end of the double-insertion pipe section 1 into the socket of the double-socket sleeve 5, with the insertion depth reaching the bottom of the socket. During the insertion process, keep the pipe section and the sleeve coaxial to avoid displacement of the rubber ring. After assembly, use a feeler gauge to check the gap between the outer wall of the spigot and the inner wall of the socket sleeve to ensure that the rubber ring has not fallen off or shifted, thus forming the pipe body foundation of "double-insertion pipe section 1 + double-socket sleeve 5 + sealing rubber ring 6".

[0036] S2: Installation of outer fiberglass protective sleeve

[0037] Socket end positioning: The socket end of the pipe body foundation (the end where the double-socket sleeve is located) is positioned by the support block 7, and the outer apex of the 5 support blocks is in close contact with the inner wall of the outer fiberglass protective sleeve 3.

[0038] Socket end positioning: At the socket end (free end of double-insertion pipe section 1) of the pipe body foundation, the top of the outer fiberglass protective sleeve 3 is inserted into the socket 11, and the other end of the positioning pin 10 abuts against the outer wall of the socket end of the double-insertion pipe section 1 to achieve socket end positioning.

[0039] S3: Plug installation (to prevent leakage during pouring)

[0040] Plug assembly: Fit the plug rubber part 9 into the groove on the inner wall of the plug shell 8. The plug rubber is designed as an inflatable rubber tire. After installation, it will inflate and expand, wrapping around the outer fiberglass sheath to achieve a seal at the bottom.

[0041] Vertical fixing and sealing: The "pipe body base + outer sheath" that has been concentrically positioned is placed vertically (pipe body axis is perpendicular to the ground) with the bottom facing down. The plug shell 8 is inserted into the end of the outer fiberglass protective sleeve 3 from the bottom, with an insertion depth of 30mm. At this time, the plug rubber part 9 is squeezed between the protective sleeve and the plug shell to form a seal.

[0042] S4: Filler pouring (forming a cement mortar protective layer)

[0043] Mortar preparation: Weigh the raw materials according to the cement mortar mix ratio, mix with a forced mixer to ensure that the mortar is uniform and free of lumps, and the mortar fluidity is 130-160mm.

[0044] Pouring operation: Slowly inject the mixed cement mortar into the annular cavity through the pouring port at the top of the outer fiberglass protective sleeve 3 to avoid the mortar flowing too fast and causing air bubbles to form in the cavity; when the mortar is poured to 10mm away from the pouring port, stop pouring, remove the positioning pin 10, and continue pouring to the pouring port.

[0045] S5: Health Preservation and Consolidation

[0046] Steam curing: Place the cast components into the steam curing chamber, close the door, and start the steam system. Set the curing parameters as follows: temperature 70℃±5℃, relative humidity ≥95%, curing time 12h. Check the temperature and humidity in the curing chamber every 2 hours during the curing process. If the humidity is lower than 95%, add steam. At the same time, observe the appearance of the components. If any leakage is found in the sheath, stop the curing process immediately and repair it.

[0047] Natural Cooling and Testing: After curing, turn off the steam system, open the curing room door, and allow the components to cool naturally to room temperature; after cooling, remove the plug and check the cement mortar protective layer 2. The surface should be free of cracks and hollows, and the thickness deviation should be ≤1mm; at the same time, check that the sealing ring 6 is not displaced and the outer fiberglass protective sleeve 3 is not deformed. If it is qualified, it is a ductile iron micro jacking pipe.

[0048] Example Effect Verification

[0049] The 0.98m long DN400 ductile iron micro-jacking pipe prepared in this embodiment meets the following performance requirements after testing:

[0050] Structural performance: The bonding strength between the cement mortar protective layer and the double-inserted pipe section and the outer fiberglass protective sleeve is ≥1.5MPa, and it can withstand a jacking force of ≥1350kN (meeting the requirements for municipal trenchless pipe jacking construction).

[0051] Corrosion resistance: After immersion in a 5% sodium chloride solution for 30 days, the pipe body showed no rust and the outer fiberglass protective sleeve showed no cracks.

[0052] Construction adaptability: No special molds are required. Casting is achieved only through the outer sheath and plugs, which increases the tolerance for pipe ellipticity, improves production efficiency, and the finished product can be directly used for micro-jacking construction in narrow spaces, avoiding the problem that traditional 6m pipe sections cannot be brought into the site.

[0053] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A casting structure for a ductile iron micro-jacking pipe, characterized in that: The device includes a double-insertion tube segment (1) cut to the target length. One end of the double-insertion tube segment (1) is fitted with a double-bearing sleeve (5). The double-bearing sleeve (5) and the double-insertion tube segment (1) are fitted with an outer fiberglass protective sleeve (3). The annular cavity formed between the outer fiberglass protective sleeve (3), the double-bearing sleeve (5) and the double-insertion tube segment (1) is used to fill cement mortar. The outer fiberglass protective sleeve (3) is kept coaxial with the double-insertion tube segment (1) by a coaxial positioning structure. A plug is fitted at the bottom of the outer fiberglass protective sleeve (3). The plug is used to seal the annular cavity.

2. The casting and molding structure of the ductile iron micro-jacking pipe according to claim 1, characterized in that: The coaxial positioning structure includes multiple support blocks (7) and positioning pins (10). The support blocks (7) are evenly distributed in the middle of the double bearing sleeve (5). The inner wall of the outer fiberglass protective sleeve (3) abuts against the support blocks (7). The side wall of the positioning pin (10) is provided with a socket (11). The top of the outer fiberglass protective sleeve (3) is inserted into the socket (11). The end of the positioning pin (10) abuts against the inner wall of the double insertion tube section (1).

3. The casting and molding structure of the ductile iron micro-jacking pipe according to claim 1, characterized in that: The plug includes a plug shell (8) and a plug rubber component (9). The outer fiberglass protective sleeve (3) is inserted into the plug shell (8) and sealed by the plug rubber component (9). The plug rubber component (9) is an inflatable rubber tire that expands when inflated and wraps around the outer fiberglass protective sleeve (3).

4. A ductile iron micro-jacking pipe cast using the casting structure described in any one of claims 1-3, characterized in that: The ductile iron micro-jacking pipe includes a double-insertion pipe section (1), a double-bearing sleeve (5), and an outer fiberglass protective sleeve (3). The inner wall of the double-insertion pipe section (1) is lined with cement mortar (4), and the annular cavity is filled with cement mortar to form a cement mortar protective layer (2).

5. The ductile iron micro-jacking pipe according to claim 4, characterized in that: A sealing ring (6) is installed inside the socket of the double-socket sleeve (5), and the sealing ring (6) fills the gap between the socket and the double-socket section (1).

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