The way to protect pipelines from corrosion

 

The invention relates to construction and is used in the construction and repair of pipelines. Put anti-corrosive coating on the inner surface of the pipe, place the pipe in the connection of the protective sleeve, provided with anti-corrosive coating. On the outer surface around the edges of each sleeve is made of an annular groove with a sealing ring of elastic material, and in the center of the annular groove is filled with insulating material. The area of the weld is located between the sealing rings are filled under pressure with low corrosivity plastic liquid by pressure testing of the pipeline with the use of this liquid. Improves the reliability of the pipeline. 3 C.p. f-crystals, 2 Il.

The invention relates to methods for protecting pipelines from corrosion and pipeline transport and can be used in the construction of pipelines with an internal protective coating.

There is a method to protect the pipeline from corrosion, comprising forming the ends of the tubes in the sockets, the application of internal protective coating, installation inside sockets response cylindrical sleeve with namename, placed on the cylindrical section of the sleeve, and comply with the circular groove is placed opposite the weld, which is filled with insulating material (U.S. Pat. Of the Russian Federation No. 21116549, CL F 16 L 13/02, publ. 27.07.98).

The disadvantage of this method is the high complexity of its implementation, due to the need of forming the ends of the tubes in the sockets, and low efficiency of the protection pipe joints from corrosion due to insufficient reliable sealing zones of welded joints from penetration of aggressive transported medium. The latter is due to the fact that the sealing elements (rings) are located on the cylindrical section of the sleeve and is pressed against the socket and the sleeve only by the elastic deformation of rings that were created with the input of the bushings in the ends of the pipes. Aggressive environment under high pressure, overcomes the elastic deformation of these rings and penetrates to the interface.

The closest in technical essence to the present invention is a method of protecting pipelines from corrosion, comprising applying to the inner surface of the pipe with a thermoplastic coating, the inside of the pipe ends of the sleeve with the inner surface having an annular groove located at the edges of the sleeve to seal the al, installing over thermoplastic material between the ends of the cover insulating ring and the connection of pipes by butt welding. When welding pipes due to the generated heat is melting and welding of the ends of thermoplastic coating with the same material in the Central groove of the sleeve, which should provide additional sealing of the joint (U.S. Pat. Of the Russian Federation No. 2157479, CL F 16 L 13/02, publ. 10.10.00, bull. N28).

The disadvantage of this method is low efficiency of protection related to the fact that the process of melting and welding of the ends of the cover pipe with a ring of thermoplastic material of the sleeve is blind and without quality control, and the o-rings are placed on the cylindrical section of the sleeve, as shown above, cannot resist the internal pressure of the transported liquids. As a result of this there is the possibility of penetration of the corrosive environment to the joints of pipes and corrosion damage. In addition, the melting and welding of the ends of the cover with thermoplastic ring sleeve is possible only in the case of thermoplastic coating of the pipe, and when using thermosetting coating this process is excluded.

The objective of the invention is to protect the pipelines from corrosion, including the application of anti-corrosive coating on the inner surface of the tube, placing the tube in the connection of protective sleeves, fitted with anti-corrosive coating and having on the outer surface along the edges of the ring grooves with o-rings made of elastic material and in the center of the annular groove filled with insulating material, pipe welding, according to the invention, to increase the effectiveness of the corrosion protection of the pipeline zone of the weld between the sealing rings under pressure fill with low corrosivity plastic liquid by pressure testing of the pipeline with the use of this liquid.

In addition, on the outer surface of one or both of the sealing rings of the sleeve is applied through longitudinal grooves across the top of the pipe.

As the pressing fluid can be used oil with the structural-mechanical properties or sustainable reverse water-oil emulsion.

The pressure test should be performed in several cycles by reducing the pressure in the intervals between cycles to the minimum possible value.

The method is illustrated in the drawing, the ENES corrosion when using the internal anti-corrosion coating.

In Fig.1 shows an embodiment of the method, where the sealing ring 4 of the sleeve 3 is hermetically isolate the zone of the welded joint 5 from the cavity of the pipe 1.

In Fig.2 shows a variant in which the o-rings are provided with longitudinal grooves 8 opposite the top of the pipe.

The method is as follows.

On the inner surface of the pipe 1 (see Fig.1) put anti-corrosive polymeric coating 2 in a known manner. Before connecting pipes between the end of one of the pipes enter the half-cylindrical protective sleeve 3, all surfaces of which are also equipped with anti-corrosive coating (not shown). The edges of the sleeve has an annular groove in which is placed a sealing ring 4, and in the center opposite the weld seam 5 - ring groove, which is filled with insulating material 6, a fixed steel ring casing 7. On the protruding end of the sleeve skewer end of the second pipe and make pipe welding. In this part of the pipe coating in the weld seam area (up to 10 cm on either side of the weld in the case of coatings based on epoxy resins) is destroyed. According to the invention, produce a fill zone of the welded joint between the seal is which has an initial shear stress (movement of such fluid begins only after overcoming the shear stress). Thus fluid under pressure, which is always higher than the working pressure, overcomes the resistance of the elastic deformation of the sealing rings 4 and penetrates into the joint space between the two sealing rings and fills it. In the upper part of this space remains compressed air, which at the start of the pipeline in operation will displace part of the plastic fluid in the pipeline that carries the aggressive environment under working pressure. However, the pressure of the plastic fluid in that space will always be higher than the operating pressure due to the resistance to elastic deformation of the sealing rings and shear stress of the liquid. For this reason, aggressive fluid cannot penetrate into the joint area.

As nishinasuno plastic fluid use dehydrated oil with a high content of asphaltenes, waxes and resins, which has the structural-mechanical properties (that is, shear stress). You can also use stable natural or artificial reverse water-oil emulsion, in which the external phase (dispersion medium) is a non-corrosive oil. This emulsion regardless sotvorimosti-active substances (surfactants), high-molecular compounds (CPA) and/or fine powders. Some natural oil-water emulsions contain natural stabilizers (e.g., asphaltenes, paraffins), and are therefore sustainable.

To facilitate filling of the areas of the joints nishinasuno plastic fluid and the displacement of these zones of gas on top of one or both of the sealing rings create longitudinal grooves 8 a cross-section in the working position of the rings is not more than 2-3 mm2.

Weight displacement gas (air) from the areas of the joints increases with cyclic pressure tests of piping plastic fluid. When the pressure of the pressurization gas is compressed and when the pressure drop to the minimum possible value of a compressed gas, overcoming the resistance of the sealing rings or through special grooves in them, goes into the cavity of the pipeline. Two or three such cycles can be almost completely displace gas from the areas of the joints, which will lead to stagnation and the best persistence plastic fluid in these areas.

Specific example

On the inner surface of steel pipe outer diameter 159 mm, wall thickness 5 mm, the ends of which previously have calibrated to the inner diameter 152 the other of 0.25 mm. The same coating was applied to all surfaces of the cylindrical protective bushing outer diameter of 150 mm, an inner diameter of 134 mm, 400 mm in length, with both ends of the groove depth of 6 mm and a width of 40 mm and in the centre of the ring groove depth of 5 mm, a width of 100 mm grooves set of sealing rings made of nepristoinoi of rubber of width of 40 mm, the inner and outer diameters in a free state, respectively 137,5 and 153 mm On the outer surface of each ring formed on one longitudinal groove width of 3 mm, depth 1 mm Grooves were oriented so so were in a straight line parallel to the axis of the sleeve. The Central groove of each sleeve wrapped asbestos fabric with a total thickness of 3 mm and put a steel ring split casing. Protective sleeve placed in the ends of adjacent pipes of the longitudinal grooves of the sealing rings up and made the welding joints. After the completion of all construction work pipeline filled natural back water-oil emulsion without free (detached) water produced pumping the emulsion through the pipeline within the estimated time at a speed of 2 m/s for the ousting of air, choked both ends Truboplast for 2 h produced the drain pressure up to atmospheric at the point of connection between the pump and kept at this pressure 0.25 h, then again increased the pressure up to 4 MPa for 2 hours Just completed 3 of such cycle. Then put the pipeline into operation for the transportation of stratified oil-water mixtures in the field, in which the aqueous phase is highly corrosive. Inspection of the three cut after six months of operation zones of the joints showed that the space between the sealing rings of all three joints were completely filled with emulsion, no signs of corrosion of the exposed sections of pipe were not.

Claims

1. The way to protect pipelines from corrosion, including the application of anti-corrosive coating on the inner surface of the tube, placing the tube in the connection of protective sleeves, fitted with anti-corrosive coating and having on the outer surface along the edges of the ring grooves with o-rings made of elastic material and in the center of the annular groove filled with insulating material, pipe welding, characterized in that to increase the effectiveness of the corrosion protection of the pipeline zone of the weld between the sealing rings under pressure fill with low corrosion Akti is 1, characterized in that on the outer surface of one or both of the sealing rings of the sleeve is applied through longitudinal grooves across the top of the pipe.

3. The method according to p. 1 or 2, characterized in that as the pressing of the liquid used oil with the structural-mechanical properties or sustainable reverse oil emulsion.

4. The method according to any of paragraphs.1-3, characterized in that the moulding is produced in several cycles by reducing the pressure in the intervals between cycles to the minimum possible value.

 

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EFFECT: enhanced reliability.

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