RU2261394C1 - Steel pipe with plastic lining - Google Patents

Abstract

FIELD: pipe-line transport, may be applicable in production of pipes and construction of pipe-lines transporting aggressive madia.

SUBSTANCE: inside the ends of the pipe lined by a plastic envelope concentrically arranged fastened to it are the outer and inner bushes. The outer bush is made of the pipe metal and is double-stage in the outside diameter. The stage of the smaller diameter of this bush is positioned in the zone of lining, and the stage of the larger diameter - between the end faces of the lining and pipe. The inner bush length exceeds that of the outer and is made of corrosion-resistant steel, a sealing ring is installed between the lining and the inner bush. The inner end of the inner bush may be made with annular shoulder on the outside surface, and the sealing ring is positioned between the annular shoulder and the end face of the outer bush. The outer end of the inner bush may be made with an annular shoulder on the outer surface.

EFFECT: enhanced serviceability of the pipe.

5 cl, 3 dwg

Description

The invention relates to pipeline transport and can be used in the production of pipes and the construction of pipelines with internal plastic lining.

A pipe with an inner plastic shell is known, comprising perforated tread and protective sleeves concentrically located at the end of the pipe and fastened to each other and with the pipe, and annular gaps made between the pipe and the outer surface of the tread sleeve and between the inner surface of the last and outer surfaces of the protective sleeve composite material (Pat. RF No. 1572141, 1987; Pat. RF No. 2095675, class F 16 L 9/02, publ. 10.11.97, Bull. No. 31).

The disadvantage of this pipe is its low service life during transportation of oilfield fluids, due to the fact that the perforations of the protective sleeve are clogged by heavy oil components and mechanical impurities blocking the protective effect of the tread sleeve. In this case, intense corrosion destruction of the end zones of the pipe (protective sleeve, weld and heat-affected zone of the pipe) occurs.

Closest to the technical nature of the proposed technical solution is a pipe with an inner plastic shell containing concentrically located at each end of the pipe and fastened with the outer and inner rings, the inner ring being made of corrosion-resistant metal, the outer ring made of the same metal as and a pipe with a wall thickness not exceeding the shell thickness. Between the inner surface of the end of the shell and the outer surface of the inner ring can be placed a sealant of an elastic material. On the outer surface of the inner ring can be made protrusions, the height of which does not exceed the wall thickness of the shell (US Pat. RF No. 2141598, CL F 16 L 9/02).

The disadvantage of this pipe is its low working capacity, due to the fact that the inner ring due to the small wall thickness (thickness is limited for reasons of saving stainless steel) does not provide reliable pressing of the end of the plastic shell to the inner surface of the pipe, as a result of which, at low temperatures, the shell shrinks more strongly than steel pipes (thermal expansion coefficients of plastics are many times higher than the coefficient for steel), leaves the pinch zone, exposing the surface of the pipe. Placing a sealant made of an elastic material between the inner surface of the end of the shell and the outer surface of the inner ring, increasing the tightness of the pinch zone, only worsens the mechanical fixation of the end of the shell (friction is reduced). The implementation of the inner ring with the outer protrusions in the pinch zone of the end of the shell, aimed at enhancing this fixation, does not completely solve the problem, since the protrusions perform their function to the necessary extent only when they are supported by a rigid ring. Moreover, the protrusions are usually obtained by turning the ring with a large initial wall thickness, which contradicts the saving of expensive stainless steel.

The objective of the invention is to improve the health of steel pipes with internal plastic lining.

The problem is solved in that in a steel pipe with an inner plastic lining, containing the outer and inner sleeves concentrically located at each end of the pipe and the outer sleeve being fastened with it, the outer sleeve being made of pipe metal and the inner sleeve longer than the outer one and made of corrosion-resistant steel, and a sealing ring made of an elastic material, according to the invention, the outer sleeve is made two-stage in outer diameter, while the step of a smaller diameter is located in not facing, and the step of greater diameter - between the ends of the lining and the pipe, and a sealing ring is arranged between the lining and the inner sleeve near the internal end of the outer sleeve.

In addition, the inner end of the inner sleeve can be made with an annular protrusion on the outer surface, and a sealing ring is located between the annular protrusion and the end face of the outer sleeve.

The outer end of the inner sleeve may be made with an annular protrusion on the outer surface.

Annular protrusions on the outer surface of the sleeve can be formed by bending the ends of the sleeve to its outer surface.

The inner sleeve can be made of a rectangular sheet by convolution and welding of its joined edges.

The drawing shows longitudinal sections (upper halves) of one of the ends of the pipe (the other end is identical) with the smooth ends of the inner sleeve (figure 1), with the inner annular protrusion of the inner sleeve (figure 2) and with ring protrusions on both ends of the inner sleeve ( figure 3).

The steel pipe 1 (see Fig. 1) is internally lined with a plastic sheath 2, the ends of which in the heat-affected zone of the weld are cut off and fixed by pressing (pinching) to the inner surface of the pipe by distributing the outer 3 and inner 4 bushings by the burnishing method. The outer sleeve 3 is made two-stage in outer diameter, and a smaller diameter step is located in the pinch zone of the shell 2. To prevent contact of the aggressive environment in the pipeline with the inner end of the outer sleeve made of pipe metal (this is ordinary carbon or low alloy steel), between the lining 2 and the inner sleeve 4 next to the inner end of the outer sleeve 3 is a sealing ring 5 of elastic material. The inner sleeve 4 is made of stainless steel, so contact with an aggressive environment is not dangerous for it.

To increase the reliability of fixing the sealing ring 5 (see figure 2) from the inside of the pipe with a small wall thickness of the inner sleeve (in order to save expensive stainless steel, they try to minimize this thickness), make an annular protrusion on the outer surface of the inner end of the inner sleeve.

With a small wall thickness of the inner sleeve there is a problem of high-quality welding of the inner sleeves of the two pipes when they are connected. In this case, burn-through of the bushings and dilution of the stainless metal of the weld of the bushings with the metal of the pipe are possible. Therefore, the outer end of the inner sleeve 4 (see FIG. 3) can also be made with an annular protrusion 7, increasing the wall thickness of the inner sleeve at the weld point.

The annular protrusions 6 and 7 (see Fig. 2 and 3) can be formed by bending the ends of the sleeve on its outer surface. And the inner sleeve itself can be made by folding a rectangular sheet and welding its edges to be joined together with subsequent heat treatment (to avoid cracking in the weld when the sleeve is distributed) or without heat treatment (if the materials used and the welding mode exclude the possibility of cracking).

The proposed pipes are interconnected by butt welding using the well-known technology for welding two-layer metals consisting of an outer layer of carbon (or low alloy) and an inner layer of corrosion-resistant steel.

In the proposed technical solution, the main clamping force of the ends of the cladding creates the thinned end of the outer sleeve of ordinary steel, so reducing the wall thickness of the inner sleeve of stainless steel does not reduce, unlike the prototype, the reliability of the fastening of the ends of the plastic lining. This generally increases the performance of the pipe with a small wall thickness of the inner sleeve (less than 3-4 mm).

An example of a specific implementation.

The ends of the steel pipe with an outer diameter of 273 mm and a wall thickness of 9 mm in accordance with GOST 8732-78 were calibrated by an inner diameter of up to 261 mm - the maximum size allowed by GOST, which eliminates the displacement of the inner edges of the ends of the connected pipes having large tolerances in inner diameter, welding. Then, the inner surface of the pipe was lined by lining with a polyethylene pipe with a diameter of 254 mm and a wall thickness of 6 mm. The ends of the polyethylene pipe were cut at a distance of 150 mm from the ends of the steel pipe inward to exclude the thermal effect of welding on the polyethylene.

By rolling a sheet of 3 mm thick from 08Kh18N10T stainless steel and welding the aligned edges (along the generatrix), an inner sleeve was made with an outer diameter of 229 mm and a length of 460 mm. At the inner end of the sleeve, an annular protrusion of 3 mm high and 8 mm wide was formed by bending one of the edges of the sheet onto the supposed outer surface before rolling it. Using a turning method, a two-stage outer sleeve was manufactured from the tube billet, the inner step of which 300 mm long has an outer diameter of 240 mm, and the outer step 145 mm long has a diameter of 252 mm. The inner diameter of this sleeve is 230 mm. The outer sleeve was put on the inner sleeve, their outer ends were leveled, and in the interval between the annular protrusion of the inner sleeve and the end face of the outer one, a ring of oil-resistant rubber (the pipe is used for pumping waterlogged oil in the oil field) with a thickness of 6 mm was installed.

The resulting assembly was placed inside the end of the pipe and distributed by a mandrel with a diameter of 235 mm.

Similarly, the second end of the polyethylene sheath was fixed.

Inspection and testing showed that the ends of the polyethylene sheath are securely pinched, and the inner ends of the outer bushings are hermetically isolated from the aggressive environment. In this case, the problem of corrosion destruction of pipe joints is completely solved with a minimum consumption of stainless steel.

Claims (5)

1. A steel pipe with an inner plastic lining, containing the outer and inner sleeves concentrically located at each end of the pipe and fastened with it, the outer sleeve being made of pipe metal and the inner sleeve longer than the outer one and made of corrosion-resistant steel, and a sealing ring made of an elastic material, characterized in that the outer sleeve is made two-stage in outer diameter, while a step of a smaller diameter is located in the cladding zone, and a step of a larger diameter tra - between the ends and the cladding tube and the sealing ring is arranged between the lining and the inner sleeve near the internal end of the outer sleeve. 2. The steel pipe according to claim 1, characterized in that the inner end of the inner sleeve is made with an annular protrusion on the outer surface, and a sealing ring is located between the annular protrusion and the end of the outer sleeve. 3. The steel pipe according to claim 2, characterized in that the outer end of the inner sleeve is made with an annular protrusion on the outer surface. 4. The steel pipe according to claim 3, characterized in that the annular protrusions on the outer surface of the sleeve are formed by bending the ends of the sleeve to its outer surface. 5. Steel pipe according to any one of claims 1 to 4, characterized in that the inner sleeve is made of a rectangular sheet by convolution and welding of its joined edges.

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