Method for connecting large-caliber high-pressure fiber reinforced flexible composite pipe
Technical Field
The invention relates to a method for connecting a large-diameter high-pressure fiber-reinforced flexible composite pipe, belongs to the field of pipe transportation, and particularly relates to the field of fiber-reinforced thermoplastic pipelines.
Background
The Reinforced flexible composite pipe (RTP pipe for short) is a high-pressure plastic composite pipeline, has the characteristics of good flexibility, corrosion resistance, high pressure resistance, impact resistance, wear resistance, light weight, easiness in connection, coilable performance, long-distance joint-free quick laying and the like, can well overcome the corrosion problem of a steel pipe and the pressure resistance problem of a plastic pipeline, and can be applied to the field of petroleum and natural gas exploitation, high-pressure long-distance natural gas transmission and various pipelines needing high-pressure transmission media.
The RTP product is generally composed of three layers, wherein the inner layer and the outer layer are made of materials more than PE80 and PE100, and the outer layer can be white (ground surface laying anti-ultraviolet) or black (buried laying) according to requirements; the middle layer is a reinforced belt compounded by reinforced materials, and the reinforced materials can be high-strength fibers such as aramid fibers, polyester fibers or glass fibers.
The prior technical scheme takes various fibers as reinforcing layers to improve the pressure bearing capacity of the pipeline, and has more mature products. SYT 6662.2-2012 non-metallic composite pipe for oil and gas industry part 2: as described in the flexible composite high-pressure delivery pipe, the maximum inner diameter of the conventional universal flexible composite pipeline is 150mm, and the nominal pressure is 6.4MPa/2.5 MPa; the nominal pressure of the flexible composite pipeline with the inner diameter of less than 90mm can reach 12MPa at most. Some enterprises can process flexible composite pipelines with the caliber of more than 1m, but the pressure bearing capacity is low, and the flexible composite pipelines are mainly used for low-pressure water delivery.
The existing fiber reinforced flexible composite pipe connection mainly adopts two forms of metal joint and fusion joint. The metal joint is that the metal inner pipe is inserted into the pipeline, the outer part of the metal joint tightly clamps the end part of the pipeline through winding or taper sleeves, and the metal joint is connected through threads or flanges. The welding joint mainly refers to a capacitor joint, thermoplastic materials are arranged in the cylindrical joint, metal wires are embedded in the cylindrical joint, and the two ends of the welding joint are connected with pipelines in butt joint and then electrified to weld the pipeline protective layers.
The prior connecting technology mainly has the following problems: (1) the metal joint has local restraint on the end part of the pipeline, the deformation of the pipeline is not coordinated after pressure bearing, and the pressure bearing capacity is low; and the pipeline enhancement layer is extruded through the metal joint to transmit axial force, the extrusion force is too large and easily causes damage to fibers, and the extrusion force is too small and not enough, so that ideal connection strength is difficult to achieve in practical application. (2) The connecting part is provided with a sleeve and connected in a welding mode, the protective layers of the pipelines at two ends are directly fused with the joint, the reinforcing layers cannot be effectively connected, and the pipelines are easy to draw and lose efficacy under the action of axial force.
Since the 21 st century, the strategic development scheme of replacing steel with plastic is greatly promoted in the pipe transportation industry, and the flexible composite pipeline is taken as a key development direction with excellent performance and develops towards high pressure and large caliber. In the field of oil and gas transmission, the pipeline pressure is high, and meanwhile, clear requirements are placed on a large caliber. At present, a long-distance pipeline is mainly made of steel, the maximum caliber reaches 1216mm, and the nominal pressure exceeds 10 MPa; the existing flexible composite pipe connecting technology is difficult to adapt to high-pressure and large-caliber pipelines.
Based on the background, a novel fiber reinforced flexible composite pipe connecting method is developed, the requirements of large caliber and high pressure are met, and the method has practical significance.
Disclosure of Invention
The purpose of the invention is as follows: the problems that the existing fiber reinforced flexible composite pipe joint is low in pressure-bearing capacity and is not suitable for large-caliber and high-pressure pipelines are solved; the problem of discontinuous force transmission of the reinforcement layer of the flexible composite pipeline joint is fundamentally solved.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows.
The method for connecting the large-caliber high-pressure fiber reinforced flexible composite pipe is characterized by comprising the following steps of:
(1) centering the fiber reinforced flexible composite pipe to be butted, and then welding the lining layer of the butted pipeline;
(2) winding the reinforced layers to a butt joint area layer by layer along the rotating direction of the reinforced layer fibers, wherein the fibers of the reinforced layers on two sides of the butt joint area are mutually overlapped, and the rotating directions of the fibers of the same layer of the reinforced layers on two sides of the butt joint area are the same and are mutually contacted;
(3) and adding a protective layer outside the joint part in a winding mode, or adding the protective layer in an extrusion molding mode, or arranging a mold outside the joint part and adding the protective layer in an injection molding mode.
Before the step (1), the winding distance of the reinforcing layer at the end part of the pipeline is set to be longer than the inner lining layer of the reinforcing layer by a certain distance, and the distance is more than 0.2 time of the inner diameter of the inner lining layer.
Before the step (1), expanding the diameter of the end part of the lining layer at the butt joint part.
Before the step (1), heating and softening the connecting part of the end part of the lining layer, and then upsetting the end part of the lining layer.
And (3) after the step (1) and before the step (2), removing the flange outside the welding area of the lining layer.
In the step (2), the overlapping length of the fibers of the inner layer of the reinforcing layer is large, the overlapping length of the fibers of the outer layer is small, and the overlapping length is gradually reduced from the inner layer to the outer layer.
In the step (2), an adhesive is applied when the fibers of the reinforcing layer are wound.
And (3) after the step (2) and before the step (3), carrying out positive and negative spiral winding on the connecting area by using fibers or fiber belts.
The protective layer in the step (3) is selected from one or a mixture of more of rubber, polyethylene, nylon, polyvinylidene fluoride, polyphenylene sulfide, polyether-ether-ketone, polyether-ketone or foamed polyethylene.
The invention has the beneficial effects that: (1) according to the invention, the enhancement layer is uniformly and interactively wound according to the rotating direction of each layer, the interlayer extrusion force can achieve the self-tightening effect of each layer, and the connection is convenient; (2) the reinforced layers are overlapped in a multi-layer mode, so that the strength of the reinforced layer at the joint part is effectively enhanced; (3) the joint part reinforcing layer is flexibly constrained, so that the problem of stress concentration of the reinforcing layer caused by a metal joint can be avoided, and the problem of insufficient strength of a welded joint is solved; (4) the technical scheme of the invention can effectively and high-strength connect the large-caliber high-pressure fiber reinforced flexible composite pipe, and meet the requirements of oil and gas pipe transmission and other application occasions.
Drawings
FIG. 1 is a schematic view of a fiber reinforced flexible composite pipe after welding of an inner liner.
FIG. 2 is a schematic view of the fiber reinforced flexible composite pipe after welding the liner layer and removing the outer flange.
Fig. 3 is a schematic winding diagram of a reinforcing layer of a fiber reinforced flexible composite pipe.
FIG. 4 is a schematic view of a multi-layer overlapping wrap of a fiber reinforced flexible composite pipe reinforcement layer.
In the figure: 1. an inner liner layer; 2. an enhancement layer; 3. and a protective layer.
Detailed Description
The present invention is not limited to the following embodiments, and the specific embodiments may be determined according to the technical solution and the practical situation of the present invention. The positional relationship of up, down, left, right, front, back, inside, outside, etc. is determined according to the layout directions of the drawings 1 and 4 in the specification.
The method for connecting the large-caliber high-pressure fiber reinforced flexible composite pipe is characterized by comprising the following steps of:
(1) centering the fiber reinforced flexible composite pipe to be butted, and then welding the lining layer 1 of the butted pipeline. As shown in figure 1, the direct welding mode of the lining layer 1 is adopted, the problem of discontinuity of the lining layer 1 is effectively avoided, and the enhancement layer 2 is prevented from contacting with the medium in the pipe.
(2) The reinforcing layers 2 are wound to the butt joint area layer by layer along the rotating direction of the fibers of the reinforcing layers 2, the fibers of the reinforcing layers 2 on two sides of the butt joint area are overlapped, and the fibers of the same layer of the reinforcing layers 2 on two sides of the butt joint area have the same rotating direction and are in contact with each other. As shown in fig. 3, the plurality of layers of fibers are overlapped with each other, so that the tensile force between the fibers can be directly transmitted, and the continuity of the reinforcing layer 2 is ensured; while avoiding that the rigid joint adversely affects the fibres of the reinforcement layer 2.
(3) And adding the protective layer 3 outside the joint part in a winding mode, or adding the protective layer 3 in an extrusion molding mode, or arranging a mold outside the joint part and adding the protective layer 3 in an injection molding mode. The outer side of the joint part is provided with a protective layer 3 which isolates the enhancement layer 2 from the external environment and prevents ultraviolet rays and external media from damaging the enhancement layer 2.
Before the step (1), the winding distance of the reinforcing layer 2 at the end part of the pipeline is set to be longer than that of the lining layer 1 by a certain distance, and the distance is more than 0.2 time of the inner diameter of the lining layer 1. When the pipelines are butted, the fibers of the reinforcing layer 2 pass through the lining layer 1 of the original pipeline and are wound on the butted pipeline, so that the load borne by the fibers can be effectively transferred.
Before the step (1), the end of the inner liner 1 at the butt joint part is expanded in diameter. Therefore, after the pipeline lining layer 1 is butted, the influence of the inner convex edge on the pipe diameter is small, and a pipe cleaner can be used for cleaning the ball.
Before the step (1), heating and softening the connecting part of the end part of the lining layer 1, and then upsetting the end part. After the connecting part is thickened, the strength of the joint part can be improved.
After step (1) and before step (2), the outer flange of the welding area of the lining layer 1 is cut off. As shown in fig. 2, after the convex edge is cut off, the fiber winding of the reinforcing layer 2 is carried out, and the fiber is smoothly transited at the joint part, thereby being beneficial to the stress of the fiber.
In the step (2), the overlapping length of the fibers of the inner layer of the reinforcing layer 2 is large, the overlapping length of the fibers of the outer layer is small, and the overlapping length is gradually reduced from the inner layer to the outer layer. As shown in FIG. 4, the multi-layer fibers are mutually tightened, and the fibers are smoothly transited layer by layer, so that the stress of the fibers is facilitated, and the fibers are not easy to loosen.
In the step (2), an adhesive is applied when the fibers of the reinforcing layer 2 are wound. Through the adhesive, each layer of fiber is convenient to wind, and the adjustment of the fiber pre-tightening force is facilitated.
And (3) after the step (2) and before the step (3), carrying out positive and negative spiral winding on the connecting area by using fibers or fiber belts. The joint part is reinforced by the mode, the strength of the joint part is improved, and meanwhile, the fiber loosening of the joint part can be prevented.
The protective layer 3 in the step (3) is one or a mixture of more of rubber, polyethylene, nylon, polyvinylidene fluoride, polyphenylene sulfide, polyether ether ketone, polyether ketone and foamed polyethylene.
Embodiment 1
1 pipeline internal diameter 700mm of inner liner, 1 polyethylene pipe that adopts wall thickness 26mm of inner liner, aramid fiber is chooseed for use in enhancement layer 2, and enhancement layer 2 contains 10 layers of fibre total thickness 20mm, and 2 fibre winding directions in enhancement layer are 55 with pipeline axis contained angle, between the adjacent layer of enhancement layer 2, fibre winding direction is opposite. The overlapping length of the innermost layer of the fiber at the joint part is 1300mm, the overlapping length of the outermost layer of the fiber is 900mm, and the overlapping lengths of the middle layers are in uniform transition. After the enhancement layer is wound, a polyethylene adhesive tape is wound on the outer side of the butt joint to serve as a protective layer 3, and the thickness of the protective layer 3 is about 4 mm.
Through experiments and finite element analysis by means of the Tsai-Wu rule, the burst pressure of the pipeline in the embodiment 1 is close to 34MPa, the strength of the joint part is far higher than that of the pipeline, and the fiber strains of all layers of the joint part are uniform and slowly changed, so that the stress state is good. (1) Performing simulation analysis according to the form of the existing metal joint structure, applying displacement constraint to the lining layer 1 at the joint part, and applying uniformly distributed pressure load of 1.6MPa to the outer side of the protective layer 3; the analysis shows that the burst pressure of the pipeline is about 25MPa, and the damage parts are concentrated at the metal buckling parts; the technical scheme of the invention improves the pressure-bearing capacity of the pipeline joint by about 36 percent and avoids the contact between the medium in the pipeline and the metal joint. (2) According to the analysis of the existing welded joint, a cylindrical rigid sleeve is arranged on the outer side of the protective layer 3, a lining layer which is the same as the protective layer 3 is arranged in the rigid sleeve, and the welding length of two ends of the joint is 200 mm; analysis shows that the internal pressure of the pipeline reaches 9 MPa, and the joint is pulled out and loses efficacy.
To summarize: according to the invention, the reinforcing layer 2 is uniformly and interactively wound according to the rotating direction of each layer, the interlayer extrusion force can achieve the self-tightening effect of each layer, and the layers are overlapped, so that the strength of the reinforcing layer 2 at the joint part is effectively enhanced; by the scheme of the invention, the problem of stress concentration of the enhancement layer 2 caused by the metal joint is avoided, and the problem of insufficient strength of the welded joint is solved. By adopting the technical scheme, the large-caliber high-pressure fiber reinforced flexible composite pipe can be effectively and strongly connected, and the requirements of oil-gas pipe transmission and other application occasions are met.