RU2594039C1 - Method of making metal pipe with internal plastic shell - Google Patents

Abstract

FIELD: pipeline transport.

SUBSTANCE: invention can be used in construction of pipelines of various purposes, transporting aggressive media. Metal pipe is lined with plastic shell. Ends of plastic shell are removed by length exceeding length of thermal destruction of plastic from point of welding. Ends of plastic pipe are attached to inner surface of metal pipe ends by expansion of inner and outer sleeves. At ends of pipe and on outer ends of inner and outer sleeves there are chamfers, wherein blunting for welding is performed only on internal sleeve. At ends of sleeves in assembly there is a conical funnel. Expansion of sleeves is carried out by successive movement of expander along axis of metal pipe from inside to support. Support has a support surface with angle equal to angle of face metal pipe and bushings for welding. Support also has a central hole with diameter equal to or larger than outer diameter of reamer and inner diameter of conical flared end sleeves by a value of not more than inner sleeve wall thickness.

EFFECT: method reduces cost of production of metal pipe with internal plastic shell and improves reliability of its anticorrosion protection.

1 cl, 3 dwg

Description

The invention relates to the field of pipeline transport and can be used in the construction of pipelines for various purposes, transporting aggressive environments.

A known method of manufacturing a steel pipe with an inner plastic lining, described in the description of patent RU No. 2238470, IPC F16L 9/02, publ. 10/20/2004. The method includes calibrating the ends of the steel pipe, lining the inner surface of the steel pipe with a polyethylene pipe, removing the ends of the plastic pipe by a length exceeding the length of the zone of thermal destruction of the plastic pipe from the place of welding. The ends of the plastic pipe are fixed by assembling from the outer and inner rings by the mandrel distribution method. The inner rings are made of stainless steel. Between the ends of the polyethylene pipe and the outer ring, a sealing ring of elastic material is installed.

The disadvantage of this method is that the distribution of assemblies from the outer and inner rings is carried out without stop, preventing the displacement of the bushings in the axial direction. In this case, the distribution in the radial direction can be carried out simultaneously along the entire length of the bushings using a high-power hydraulic press and a mandrel of complex design, which increases the cost of manufacturing the pipe. At the same time, sufficient tightness between the steel and polyethylene pipes is not achieved, as evidenced by the installation of additional sealing rings of elastic material, which leads to an increase in the cost of the pipe structure.

A known method of manufacturing a steel pipe with an internal plastic pipe for welding connections (patent RU No. 2525032, IPC F16L 13/02, published in Bul. No. 22 of 08/10/2014), including lining the inner surface of a metal pipe with a plastic pipe, removing the ends of the plastic pipe by a length exceeding the length of the zone of thermal destruction of the plastic pipe from the place of welding, fixing the ends of the plastic pipe to the inner surface of the steel pipe with bushings. Outer bushings made of the same metal as the pipe are installed inside the ends of the steel pipe to the end of their inner ends in the ends of the plastic pipe and secured by turning. Corrosion-resistant steel inner sleeves are installed inside the outer sleeves and at the ends of the plastic pipe. The ends of the plastic pipe are fixed by distributing the bushings using a hydraulic press equipped with a special expander. The inner sleeves, the outer sleeves and the ends of the plastic pipe are glued together with glue, mastic or sealant. Then, welding bevels are made at the ends of the pipe.

The disadvantage of this method is that the distribution of the bushings by means of a hydraulic press equipped with a special expander, is carried out without stop, preventing the displacement of the bushings in the axial direction. In this case, the distribution in the radial direction can be carried out simultaneously along the entire length of the sleeves using a high-power hydraulic press and an expander of complex design, which increases the cost of manufacturing the pipe. The adhesive materials proposed in the method, capable of gluing metal with metal and metal with plastics, have a high cost. The bonding technology, together with the phased sealing of the fixing of the sleeves, is complex and difficult to control, which can reduce the reliability of the corrosion protection of pipes in serial production. The disadvantage is that the chamfer for welding at the ends of the pipe is formed in a separate operation after installing the bushings, which also leads to an increase in its cost.

The technical objectives of the invention are to reduce the cost of manufacturing a pipe and increase the reliability of its anti-corrosion protection.

The problem is solved by a method including lining the inner surface of the metal pipe with a plastic shell, removing the ends of the plastic shell by a length exceeding the length of the zone of thermal destruction of the plastic shell from the weld point, securing the ends of the plastic shell to the inner surface of the ends of the metal pipe by expanding the inner and outer bushings using a hydraulic press equipped with a special expander.

New is that at the ends of the pipe and at the outer ends of the inner and outer sleeves, chamfers are made before welding to be assembled, and dulling for welding is performed only on the inner sleeve, while at the ends of the sleeves assembled, a cone socket is made, the bushings are expanded by sequential movement the extender along the axis of the metal pipe from the inside to the stop having a bearing surface with an angle equal to the angle of the chamfer of the metal pipe and the welding sleeves, and a central hole whose diameter is equal to or greater than n the outer diameter of the expander and the inner diameter of the conical socket of the bushings by an amount not more than the wall thickness of the inner sleeve.

In FIG. 1 shows an assembly of outer and inner bushings.

In FIG. 2 shows a longitudinal section through a metal pipe with an inner plastic sheath at the initial moment of expansion of the outer and inner bushings.

In FIG. 3 shows a longitudinal section through a metal pipe with an inner plastic sheath at the final moment of expansion of the outer and inner bushings.

The manufacture of a metal pipe with an inner plastic shell according to the proposed method can be carried out as follows (Fig. 1). Of the corrosion-resistant steel, inner sleeves 1 are made with a chamfer 2 at one of the ends having an angle α and a blunt “b” for welding. The outer sleeves 3 are made of carbon steel with a chamfer 4 at one of the ends having the same angle α, but without blunting for welding. The outer sleeves 3 are mounted on the inner sleeves 1 so that their chamfers 2 and 4 coincide. The metal pipe 5 (Fig. 2), having chamfers 6 without blunting for welding, is lined from the inside with a plastic sheath 7. The ends of the plastic sheath 7 are removed inside the ends of the metal pipe 5 on the length of the thermal effect of the heat of welding, at which the plastic shell 7 does not break. On the resulting assemblies (Fig. 1), a conical socket 8 is made from the inner 1 and outer 3 bushings from the side of the combined chamfers 2 and 4 (Fig. 2). Then, the assembly of the inner 1 and outer 3 bushings is put on the rod 9 of the hydraulic press (not shown in FIG. 2) so that the expander 10 mounted on the end of the rod 9 is located at the end of the inner sleeve 1 opposite the combined chamfers 2 and 4 ( Fig. 1). The rod 9 (Fig. 2) of the hydraulic press is moved so that the end face of the assembly of the inner 1 and outer 3 bushings, having chamfers 2 and 4 (Fig. 1), touches the supporting surface 11 (Fig. 2) of the stop 12 of the hydraulic press. The supporting surface 11 of the stop 12 is made in the form of a cone with an angle α equal to the angle of the chamfers of the metal pipe 5, the inner sleeve 1 (Fig. 1) and the outer sleeve 3. In the stop 12 (Fig. 2), a central hole 13 is made, the diameter of which is equal to or more than the outer diameter of the expander 10. This diameter is also equal to or greater than the inner diameter of the conical socket of 8 bushings 1 and 3, but not more than the wall thickness of the inner sleeve 1. With this diameter, the inner sleeve 1 is reliably fixed from axial shift around the perimeter of the central hole 13. If the diameter hole 13 will exceed the inner diameter of the cone socket 8 by two wall thicknesses of the inner sleeve 1, then the inner sleeve 1 will not abut against the supporting surface 11 of the stop 12. If the diameter of the hole 13 of the inner diameter of the cone socket 8 is between one wall thickness and two wall thicknesses the inner sleeve 1, the inner sleeve 1 will abut against the supporting surface 11 from half the thickness of its wall to zero. With such an emphasis, the inner sleeve 1 will move into the hole 13 due to the crushing of the supporting part of its wall in contact with the supporting surface 11 (corrosion-resistant steel is more plastic than simple carbon steel). The rod 9 of the hydraulic press together with the expander 10 and the assembly of the inner 1 and the outer 3 bushings pressed against the stop 12, is introduced into the end of the metal pipe 5 so that the end of the metal pipe 5 is in contact with the supporting surface 11 of the stop 12. After turning on the hydraulic press, the rod 9 (Fig. 3) moves the expander 10 towards the stop 12. In this case, the assembly of the inner 1 and outer 3 bushings, limited from the axial shift by the stop 12, undergoes expansion. With this expansion, the conical socket 8 (Fig. 2) is smoothed out, and the end of the plastic shell 7 (Fig. 3) and the outer sleeve 3 are tightly pressed against the inner surface of the metal pipe 5, sealing the cavity between the metal pipe 5 and the plastic shell 7. Since the diameter of the hole 13 is equal to or greater than the outer diameter of the expander 10 (equal with a positive tolerance), the expander 10 is freely removed from the expansion zone of the bushings 1 and 3 through the hole 13. When smoothing the conical socket 8 (Fig. 2) with the expander 10 (Fig. 3) the ends of the metal tr to 5, the inner sleeve 1 and the outer sleeve 3 are aligned on the support surface 11 (angle α) the stop 12, forming joint bevel for welding metal pipe 5 with bushings 1 and 3 assembly. In this case, the blunting “c” (Fig. 1) at the joint chamfer remains on its inner side, at the end of the inner sleeve 1 (Fig. 3) in accordance with the requirements of normative documentation for pipe welding (VSN 006-89, GOST 5264-80 and other). The proposed method has the following advantages:

- reliable fixation on the stop 12 of the assembly of the inner 1 and outer 3 bushings having a conical socket 5 (Fig. 2), prevents the possibility of their shift during expansion, which in turn provides high tightness of the cavity between the metal pipe 5 (Fig. 3) and a plastic sheath 7;

- high tightness eliminates the use of additional sealants and seals, prevents corrosion damage to the inner surface of the metal pipe 5, excluding its contact with the pumped medium;

- for the proposed technology of sequential expansion of the assembly of the inner 1 and outer 3 bushings on the stop 12 requires low-pressure press equipment, which reduces the cost of equipment, energy consumption;

- the use of low-power press equipment makes it possible to use the proposed method in the field during the construction and repair of a pipeline with an internal plastic shell;

- the formation after expansion of the common chamfer for welding at the ends of the metal pipe 5 with the inner plastic shell 7 assembly eliminates two additional operations of making bevels by turning.

Thus, the proposed method reduces the cost of manufacturing a metal pipe with an inner plastic sheath and increases the reliability of its corrosion protection.

Claims (1)

A method of manufacturing a metal pipe with an inner plastic shell, including lining the inner surface of a metal pipe with a plastic pipe, removing the ends of the plastic pipe by a length exceeding the length of the zone of thermal destruction of the plastic pipe from the weld point, fixing the ends of the plastic shell to the inner surface of the ends of the metal pipe by expanding the inner and outer bushings using a hydraulic press equipped with an expander, characterized in that at the ends of the pipe and on the external Before the assembly of the ends of the inner and outer sleeves, chamfers are made for welding, and blunting for welding is performed only on the inner sleeve, while the ends of the sleeves are assembled with a conical socket, the expansion of the sleeves is carried out by sequential movement of the expander along the axis of the metal pipe from the inside to the stop, which has a support a surface with an angle equal to the angle of the chamfer of the metal pipe and sleeves for welding, and a Central hole, the diameter of which is equal to or greater than the outer diameter of the expander and the inner diameter the conical socket of the bushings by an amount of not more than the wall thickness of the inner sleeve.

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