RU2342588C1 - Corrosion safety method of weld connection of metal pipes with internal corrosion-resistant coating - Google Patents

Abstract

FIELD: construction, pipeline.

SUBSTANCE: plug consisting of two telescopically connected with each other branch pipes, internal surface whereof is made of corrosion-resistant metal, is installed inside the end of the pipe at a depth exceeding length of the heat-affected zone. Sealing ring is preliminary set between the collar and inner face of the external branch pipe, external branch pipe is entered into the pipe at a depth equal or exceeding length of the heat - affected zone and is fixed to the pipe. Sealing ring is pressed between the collar and end face of the external branch pipe by power movement in axial direction of the internal branch pipe, and internal branch pipe is fastened to the external branch pipe.

EFFECT: simplified repairing of active pipelines.

4 cl, 3 dwg

Description

The invention relates to pipeline transport and can be used in the manufacture of pipes with an internal anti-corrosion coating, construction and repair of pipelines from such pipes.

A known method of protection against corrosion of the weld zone of the pipe with an internal protective coating, comprising installing in the connection zone of the protective sleeve having on the outer surface at the ends of the sealing rings and a layer of sealing curable composition (US Pat. RF No. 2209360, class. F16L 58/02, publ. . July 27, 2003, Bull. No. 21). The sealing composition can be pumped into the cavity between the pipe and the sleeve after connecting the pipes by welding through special holes (US Pat. RF No. 2195603, class. F16L 58/04, publ. 12/27/02, Bull. No. 36; US Pat. RF No. 2122150, class. F16L 58/02, publ. 20.11.98).

The disadvantage of this method is the impossibility of its use in the repair of existing pipelines, since the second end of the pipeline must be pushed onto the second half of the protective sleeve, which is not feasible with a large length of the pipeline. In addition, it does not provide reliable protection of the weld zone from the corrosive effects of the pumped aggressive medium, because the sealing compound does not always completely fill the gap between the pipe and the sleeve due to the complex configuration of the cavity.

There is also known a method of connecting pipes with an internal anti-corrosion coating during pipeline repair, including removing a damaged pipe section, installing a sleeve in the pipe ends in a corrosion-resistant version with sealing elements at the ends, placing adhesive material on the outer surface of the ends of the sleeve, installing a split insert pipe in the gap between the ends of the pipes, welding a split insert along two generators and the connection of the insert with the ends of the pipes by butt welding (utility model of the Russian Federation No. 19120, class F16L 13/02, publ. 10.08.01, Bull. No. 22).

The disadvantage of this method is the low reliability of the connection, due to the fact that the split insert, welded on two generators in the field, has low mechanical strength, especially with a large length of the damaged area. This also raises the problem of reliable insulation of the outer surface of the insert after welding work from the corrosive effects of the soil. In addition, the adhesive material does not provide reliable sealing of the zones of joints from the aggressive environment in the pipeline due to the lack of control of the continuity of its application around the entire perimeter of the pipe. This reduces the durability of the connection.

The closest in technical essence to the proposed is a method of protecting against corrosion of the welded joint of steel pipes with an internal anti-corrosion coating, implemented in the method of connecting such pipes, including calibration of pipe ends, installation of bushings made of corrosion-resistant steel having sealing layers on the outer surface, the ends of the pipes to be connected, the bushings are secured by their radical distribution by the cutting device until it comes into contact with the interference with the inner surface of the pipes, preparation of the ends lock and pipe for butt welding and welding of bushings and pipes (US Pat. RF No. 2262028, class F16L 13/02, publ. 10.10.05, Bull. No. 28).

The disadvantage of this method is the difficulty of its implementation in the repair of existing pipelines in the field, since heavy mobile equipment is required to calibrate the ends of the pipes and to drill the bushings.

The objective of the invention is to simplify the method when repairing existing pipelines, including the replacement of damaged sections.

The problem is solved in that in the method of corrosion protection of the welded joint of metal pipes with an internal anti-corrosion coating, comprising installing a sleeve having a sealing ring on the outer surface, inside the pipe end to a depth greater than the heat-affected zone of welding, fixing the sleeve and preparing the ends of the sleeve and butt welding pipes, according to the invention use a sleeve in the form of two telescopic interconnected pipes, the inner of which is made of corrosion metal and with a ring protrusion at the inner end, the sealing ring is placed in the gap between the annular protrusion and the inner end of the external pipe, the external pipe is inserted into the pipe to a depth equal to or greater than the length of the heat-affected zone of welding, and attached to the pipe, the sealing ring is pressed between an annular protrusion and an end face of the outer pipe by axially moving the inner pipe and the inner pipe is attached to the external pipe.

The surface of the annular protrusion facing the sealing ring may be conical.

A conical expansion may be formed on the outer surface of the outer end of the outer pipe, the diameter of which exceeds the inner diameter of the pipe.

The surface of the inner end of the outer pipe may be tapered.

The method is illustrated by drawings, which shows longitudinal sections of the upper halves of the end sections of the connected pipes.

Figure 1 shows the initial position of the means of protecting the welded joint zone from corrosion after they are inserted into the end of the pipe.

Figure 2 and 3 show the ends of the pipes to be connected after preloading the sealing ring and securing the nozzles (options).

The method is as follows.

At the end of the pipe 1 (see Fig. 1) with an internal anti-corrosion coating 2, the end of which is prepared for welding (the external and internal bevels are removed), a composite telescopic sleeve is introduced, consisting of an internal pipe 3 made of corrosion-resistant metal, an external pipe 4 and a sealing ring 5 of elastic material located between the annular protrusion at the inner end of the inner pipe and the end of the outer pipe.

An annular protrusion of the inner pipe is preferably formed with a conical surface facing the sealing ring 5. On the outer surface of the outer end of the outer pipe 4, a conical extension is formed for centering the outer pipe relative to the pipe axis and eliminating the gap between the pipe and the pipe at the end in the welding zone.

The external pipe 4 is introduced into the pipe to a depth equal to or greater than the length of the heat affected zone of the weld. In this case, the sealing ring 5 is located outside the zone of thermal destructive effect of welding on the coating of the pipe and the material of the ring.

After installing the external pipe until it stops tapered in the end of the pipe, attach it to the pipe by welding along the inner pipe facet with seam 6 (see Fig. 2) and remove the outer facet at the end of the pipe as an extension of the pipe facet. Using an auxiliary device (not shown), the inner pipe 3 is pulled from the pipe with a force of up to 5 tons, depending on the diameter of the pipe, to press the sealing ring against the inner surface of the pipe and the outer surface of the inner pipe. Attach the inner pipe 3 to the external pipe 4 by welding along the inner chamfer of the external pipe with a seam 6. After that, the chamfer at the end of the internal pipe is removed in the form of a continuation of the chamfers of the pipe and the external pipe.

In another embodiment, the surface of the inner end of the outer pipe 4 (see FIG. 3) is tapered, which enhances the pressure of the sealing ring 5 on the pipe’s inner surface over the entire width of the ring and, therefore, ensures the tightness of the weld zone at higher pressure in the pipe.

The connection of pipes with an internal anticorrosion coating with the proposed method of corrosion protection of the welded joint zone is carried out according to the technology of welding two-layer pipes - first, welding is carried out on the inner pipe with corrosion-resistant electrodes, then on the external pipe and pipe with conventional electrodes.

In the proposed method, the calibration of the ends of the pipe by the inner diameter is not required (in order to eliminate errors in the manufacture of pipes), since the scatter of the inner diameter and the ovality of the pipes compensates for the deformation of the elastically elastic sealing ring, the outer diameter of which increases sufficiently when the inner pipe is forcefully moved in the longitudinal direction. To move the inner pipe, the simplest device weighing no more than 10 kg is used. All this greatly simplifies the production of work in the field.

Claims (4)

1. A method of protecting against corrosion of the welded joint zone of metal pipes with an internal anticorrosion coating, comprising installing a sleeve having a sealing ring on the outer surface, inside the pipe end to a depth greater than the heat-affected zone of welding, securing the sleeve and preparing the ends of the sleeve and pipe for butt welding , characterized in that the sleeve is used in the form of two telescopically interconnected nozzles, the inner of which is made of corrosion-resistant metal and with an annular protrusion and the inner end, the sealing ring is placed between the annular protrusion and the inner end of the outer pipe, the outer pipe is inserted into the pipe to a depth equal to or greater than the length of the heat-affected zone of welding, and attached to the pipe, the sealing ring is pressed between the ring ledge and the end of the outer pipe by force moving the inner pipe in the axial direction and attach the inner pipe to the outer pipe. 2. The method according to claim 1, characterized in that the surface of the annular protrusion facing the sealing ring is tapered. 3. The method according to claim 1, characterized in that on the outer surface of the outer end of the outer pipe form a conical extension, the diameter of which exceeds the inner diameter of the pipe. 4. The method according to claim 1 or 2, characterized in that the surface of the inner end of the outer pipe is tapered.

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