RU2347970C1 - Method of antirust protection of metal pipe-to-inner polymer coating welded joint area - Google Patents

Abstract

FIELD: machine building, pipelines.

SUBSTANCE: invention relates to pipeline transport and can be used in construction and repair of pipelines with inner polymer antirust coating. A metal sleeve is press-fitted in the end of each pipe to be jointed together between the pipe and inner coating, the sleeve length exceeding the welding thermal effect area. Note that the sleeve features two inner tapered surfaces, widening towards the sleeve ends, and a funnel on its outer end, and an outer diameter is equal or exceeds the pipe ID. Note also that the coating end is extended. Fastening and sealing the coating end is performed by press-fitting the jamming ring into the coating end, within the area of the sleeve inner surface widening towards outside end. Note that the said jamming ring features an outer tapered surface matching the sleeve tapered surface outer end.

EFFECT: expanded performances.

2 cl, 2 dwg

Description

The invention relates to the field of pipeline transport and can be used in the construction, reconstruction and repair of pipelines in the oil and petrochemical industries, as well as in the housing and communal services system.

A known construction of a pipe with an inner plastic sheath (utility model of the Russian Federation No. 38497, F16L 9/02, bull. No. 17 dated 06/20/04), in which the ends of the plastic sheath are attached to the inner surface of the pipe using protective sleeves with tapered threads on their outer surface screwed into pipe ends.

The disadvantages of this method are poor tightness and low mechanical strength in the axial direction of the threaded connection between the protective sleeve and the plastic shell due to the large tolerances on the inner diameter and ovality of the pipes, which reduces the reliability of the fastening of the ends of the shell and the corrosion protection of the welded joint zone.

A known method of lining pipes having an external thread with a thermoplastic sheath (US Pat. RF No. 2143977, B29C 63/44, 57/06; F16L 9/02, bull. No. 1 from 01/10/2000), according to which a thermoplastic is introduced into the pipe the shell, leaving its ends protruding beyond the ends of the pipe, is threaded on the inner surface of the protruding ends of the shell, the sleeves with the outer flange are screwed into the ends of the shell until they stop, after heating the protruding ends of the shell, the sleeves are turned, forming flanges of the sleeves on the ends of the shell. The ends of the sheath are fixed from longitudinal movement by rings of corrosion-resistant metal placed outside the end of the pipe thread run-off.

The disadvantages of this method are:

- insufficient tightness of the threaded connection between the bushings and the shell due to the large tolerances on the inner diameter of the lined pipe;

- insufficient mechanical strength in the axial direction of the threaded connection between the bushings and the sheath due to the large tolerances on the inner diameter of the lined pipe, as a result of which the ends of the sheath are fixed from longitudinal movement by rings by their radial distribution;

- the possibility of thread breakage at the end of the thermoplastic sheath when forming end flanges on it when turning the sleeve due to the softening of the thermoplastic material after heating;

- the complexity and energy intensity of the process associated with the use of powerful press equipment when fixing the thermoplastic sheath with rings of corrosion-resistant metal, which makes it difficult to use this method in the field when reconstructing or repairing a pipe from pipes with an internal thermoplastic sheath.

The closest in technical essence to the proposed one is a method of fastening and sealing the inner lining at the ends of a metal pipe (RF patent No. 2216671, F16L 9/02, bull. No. 32 of 11/20/03), including the removal of the shell from the end sections of the pipes to a depth thermal influence that occurs during pipe welding, installation of clamping rings at the ends of the pipes with overlapping part of the shell, fixing and sealing of the ends of the shell by distributing the rings using a mandrel and a hydraulic press.

The disadvantages of this method are its high complexity and energy consumption associated with the need to use powerful press equipment, which makes it difficult to use this method in the field when reconstructing or repairing a pipe from lined pipes.

The objective of the invention is to reduce the complexity and energy consumption of the method of protection against corrosion of the weld zone of metal pipes with the inner polymer shell during reconstruction and repair of pipelines.

The problem is solved in that in the method of corrosion protection of the welded joint of metal pipes with the inner polymer shell, including removing the shell from the end sections of the pipes to the depth of the thermal effect that occurs during welding, installing clamping rings at the ends of the pipes with overlapping part of the shell, fixing and sealing the ends of the shell by mechanical action on the clamping rings, followed by connecting the ends of the pipes by butt welding, according to the invention, before removing the shell from the end a metal sleeve is pressed into the gap between the pipe and the shell on the section of each pipe, the outer diameter of which is smaller than the inner diameter of the pipe, longer than the heat-affected zone of welding, with two inner conical surfaces expanding to the ends of the sleeve, and a socket at the outer end, the outer diameter which is equal to or greater than the inner diameter of the pipe, while simultaneously pulling the end of the shell, and securing and sealing the end of the shell by pressing into the end of the shell in the the morning surface of the sleeve expanding toward the outer end of the pinched ring having an outer conical surface corresponding to expanding toward the outer end of the conical surface of the sleeve.

In this case, the bushings and jamming rings can be made of corrosion-resistant metal.

Figure 1 shows the initial position of the connected end of one of the pipes at the initial moment of insertion of the sleeve into the gap between the shell and the pipe.

Figure 2 shows the end of the pipe with a sheath attached to the inner conical surface of the sleeve with a pinched ring, ready to be connected to the similar end of another pipe by butt welding.

The method is as follows.

The end of the polymer shell 1 (see FIG. 1) mounted on the inner surface of the metal pipe 2 is cut with the formation of trapezoidal petals, which are pressed against the conical mandrel 3 by the outer ring 4. A sleeve 5 is put on the conical part of the polymer shell 1, the outer the diameter of which is smaller than the inner diameter of the pipe 2, and the length exceeds the heat affected zone of welding, with a socket 6 at the outer end and two inner conical surfaces 7 and 8, expanding to the ends of the sleeve 5. Outer diameter the bell 6 is greater than or equal to the maximum (taking into account the tolerances according to GOST) inner diameter of the pipe 2. While simultaneously pulling the polymer shell 1 with the help of a conical mandrel 3 and the outer ring 4, a sleeve 5 is introduced into the gap between the pipe 2 and the shell 1 until , while the end face of the socket 6 (see figure 2) of the sleeve 5, pressed into the end of the pipe 2, is not equal to its end. The socket 6 of the sleeve 5 is fixed relative to the end of the pipe 2 by tacks of electric arc welding. Then the end of the polymer shell 1 is cut to a depth L from the end of the pipe 2, exceeding the length of the zone of thermal destruction of the shell 1 when welding pipes. After that, a clamping ring 9 with an outer conical surface corresponding to the inner conical surface 8 of the sleeve 5 is pressed into the end of the polymer shell 1, and it is fixed relative to the sleeve 5 by tacks of electric arc welding. Thus, the end of the polymer shell 1 is firmly and tightly clamped between the conical surfaces of the sleeve 5 and the clamping ring 9, which eliminates the possibility of axial displacement of the shell 1 and penetration of the pumped medium into the gap between the shell 1 and the pipe 2. In order to avoid corrosion, the sleeve 5 and the clamping ring 9 are made of corrosion resistant metal. The end of the pipe 2 together with the socket 6 of the sleeve 5 pressed into it is connected to the similar end of the other pipe using the technology of welding bimetallic pipes.

The proposed method reduces the complexity and energy consumption of the method of protection against corrosion of the zone of the welded joint of metal pipes with the inner polymer shell during the reconstruction and repair of pipelines and increases its reliability.

Claims (2)

1. A method of protecting against corrosion of the welded joint zone of metal pipes with the inner polymer shell, including removing the shell from the end sections of the pipes to the depth of the thermal effect that occurs during welding, installing clamping rings at the pipe ends with overlapping part of the shell, fixing and sealing the ends of the shell by mechanical impact on the jamming rings and the butt ends of the pipes by butt welding, characterized in that before removing the shell from the end section of each of the pipes into the gap between the pipe and the shell a metal sleeve is pressed in with a sleeve, the outer diameter of which is smaller than the inner diameter of the pipe, with a length exceeding the heat affected zone of welding, with two internal conical surfaces expanding to the ends of the sleeve, and a bell at the outer end, the outer diameter of which is equal to or greater than the inner diameter of the pipe, at the same time, the end of the shell is pulled, and the end of the shell is fixed and sealed by pressing into the end of the shell in the area of the inner surface of the sleeve, expanding to th end, pinches the ring having an outer conical surface corresponding to the outer end of the expanding conical surface of the sleeve. 2. The method according to claim 1, characterized in that the bushings and jamming rings are made of corrosion-resistant metal.

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