RU2313720C2 - Method of deposition of the polymeric coating on the steel pipelines - Google Patents

Abstract

FIELD: chemical industry; petrochemical industry; oil-producing industry; natural gas industry; methods of deposition of the polymeric coating on the steel pipelines.

SUBSTANCE: the invention is pertaining to construction of the pipeline transportation and may be used at the hot deposition of the polymeric protecting coating on the steel pipes, and also in the trace conditions at repairs of the pipelines having the industrial polymeric coatings. The method provides that preliminarily clean and heat up the being isolated surface, put on it by the spiral winding with the simultaneous rolling by the roller the strip of the thermo-shrinking polymeric material of the protecting coating with the adhesive thermoplastic layer out of the adhesive composition. The heating of the surface is conducted up to the fusion point of the adhesive composition. On the being isolated surface additionally put by winding the strip of the adhesive thermoplastic material reinforced by the mesh. For the protecting coating use the double-layer thermally contracting strip put with the strain in front of the pressing roller. After this deposition the surface of the double-layer thermally contracting strip is additionally heated up to the shrinking temperature by means of the radiant heating. The invention allows to increase stability of the protecting coating against the shift loadings.

EFFECT: the invention ensures the increased stability of the protecting coating against the shift loadings.

Description

The invention relates to the field of protection of metals from corrosion and can be used when hot applying a polymer protective coating to steel pipes, as well as when repairing pipelines with a factory polymer coating under route conditions.

A known method of applying a protective coating to steel pipes based on mastic tapes, for example of the type "LIAM", with the separate application of the mastic reinforced layer and the polymer protective coating with the mastic layer when cold applied to pipes with preliminary primer application on the surface (V. Ryabov and Mastic-bitumen and other coatings for protecting pipelines - Properties of coatings, technology and equipment for their application, Sat. Development and implementation of technologies, equipment and materials for repair of insulation coatings and defective pipe sections, including KRC defects, on the gas pipelines of OAO Gazprom. Materials of the Scientific and Technical Council of OAO Gazprom. Ukhta, OOO Severgazprom, October 28-30, 2003, in 2 volumes. Volume 1. M.: IRC Gazprom LLC, 2004, p. 54-65).

However, the characteristics of a cold coating coating and its durability are lower than that of a hot coating.

A known method of applying a polymer protective coating on the insulated surface of steel pipes in the factory, including heating the insulated surface and forming insulation on it from a polymer heat-shrinkable material with a thermoplastic adhesive layer. The contact of the polymer material with the insulated surface is created by winding simultaneously with the rolling along the entire width of the insulated section (AS USSR No. 1536154, F16L 58/00, publ. 15.01.1990).

The disadvantage of this method is that the coating obtained by the known method does not always provide cohesive peeling of the insulating material on the surface of the pipe.

The closest technical solution adopted for the prototype is the method of applying a polymer protective coating on the insulated surface of steel pipelines (Khallyev N.Kh., Seliverstov V.G. et al. Repair of local sections of pipelines. / Review. Inform. - Series Pipeline repair. - M.: IRC Gazprom LLC, 2001, p.24-28). The method includes cleaning the surface of the pipe, applying the applicator to the heat-affected zone, heating the insulated surface in the inductor and winding the tape from a polymer heat-shrinkable material with an adhesive thermoplastic layer with simultaneous rolling.

However, this method does not always provide reliable insulation of the pipe surface in the presence of caverns (corrosion recesses) on it, as well as in the area of transition from the weld to the pipe surface, due to the possible formation of heat-affected "tent" zones caused by the tension of the polymer tape after thermal shrinkage. In addition, local isolation of the heat-affected zone (application of applicators) mechanized in route conditions is difficult.

The technical problem solved by the invention consists in the formation of a monolithic non-porous coating with elevated operating temperatures (up to 100 ° C) in route conditions, directly on the pipeline, using heat-shrinkable tapes with an adhesive layer, ensuring high resistance of the coating to shear loads over the entire surface pipeline, including zones of longitudinal and transverse seams, and moisture resistance.

The problem is solved due to the fact that in the method of applying a polymer protective coating on the insulated surface of steel pipelines, mainly under route conditions, including preliminary cleaning and heating of the insulated surface, applying it by spiral winding while simultaneously rolling the tape with a heat-shrinkable polymer coating material with a thermoplastic layer from the adhesive composition according to the invention, the surface is heated to the melting temperature of the adhesive composition layer and the adhesive surface is additionally wound with a tape of adhesive thermoplastic material reinforced with a mesh, and for the protective coating use a two-layer heat-shrink tape and apply it with tension in front of the press roller, and after application, the surface of the two-layer heat-shrink tape is additionally heated to a shrink temperature using a source radiant heating.

When insulating pipelines, it is necessary to reliably protect with insulation material the surface of the pipeline and the area of welded joints. The quality of the insulation coating obtained by applying to a heated pipe using appropriate materials is higher than when applying a coating based on cold-applied materials.

On a pre-cleaned and heated surface of the pipeline in series, a layer is applied on the layer of an adhesive thermoplastic layer in the form of a mesh-reinforced tape and a layer of polymer protective coating in the form of a tape with an adhesive thermoplastic layer. The reinforcement of the adhesive layer with a mesh is necessary to give the tape equal strength in length and width and the possibility of its minimum tension when applied to prevent sagging.

Both layers are applied sequentially using two rolls of materials located diametrically relative to the axis of the pipe by spiral winding the tapes along the length of the pipeline, providing tension to the polymer protective coating in front of the elastic press roller. When in contact with a heated pipe, the first layer (adhesive) goes into a thermoplastic state and, under the pressure of the press roller acting through the protective polymer coating layer, fills cavities and other irregularities on the pipeline surface, eliminating the formation of voids in the transition zone from the reinforcement of the weld to the pipe surface. In addition, during rolling, air bubbles are eliminated between the coating layers and gluing overlays of the polymer protective tape. After rolling, the heat-shrinkable polymer protective coating is heated from the outside, which ensures its shrinkage and, as a consequence, the normative adhesion of the coating to the pipe metal and between its layers. This ensures complete isolation of the outer surface of the pipeline from the harmful effects of the external environment, including guaranteed protection of welded joints.

The method is as follows. On a pipeline with a prepared surface (after sandblasting), an annular detachable heating chamber is installed, the drive of which is a device that ensures uniform movement of the chamber. After the heating chamber, in the direction of the insulating complex, an insulating machine is installed on the pipeline, equipped with two spools and two additional rolling devices. A roll of tape with an adhesive thermoplastic reinforced mesh layer and a second roll of a two-layer heat-shrinkable tape for applying a polymer protective coating are installed on the spools. The spools and presser are located on one side of the machine. Their mutual axial location is such that the adhesive thermoplastic reinforced layer with an overlap of at least 10 mm is first applied, a polymer protective layer with an overlap of at least 30 mm and with an elastic roller at the time of application of the heat-shrinkable tape to the pipe is applied over it 90 ° around the circumference. And then, with another press roller, through 90 °, an additional rolling of the coating is carried out with an already softened adhesive layer. In this case, after the insulating machine, a shrink annular heating chamber is placed on the pipeline. When this equipment complex moves along the pipeline, a continuous process of heating the pipeline, applying and heat shrink the coating, which provides reliable protection of the surface of the pipeline and the zones of welded joints. A process stop is provided for changing rolls of insulating materials.

The proposed method was tested when applying a protective insulating coating on a section of the gas pipeline "Bukhara-Ural" with a diameter of 1020 mm

After cleaning it, an annular detachable movable heating chamber was mounted on the pipeline section. After the heating chamber along the movement of the insulating complex, an IMM-1020 insulating machine was installed, equipped with two rolls of tapes and two stitching devices. As an adhesive thermoplastic layer, a reinforced aggregate tape made of a polyethylene copolymer 430 mm wide with a reinforcing fiberglass mesh impregnated with an organic composition providing moisture resistance of the fiberglass mesh was used, and a TERMA-STMP two-layer heat-shrinkable tape was used as a protective polymer coating 450 mm The materials were applied sequentially layer by layer by spiral winding of overlapping tapes in the outer layer of at least 30 mm by tensioning a heat-shrinkable tape in front of an elastic press roller with a force of at least 15 n / cm, while rolling was carried out by an elastic rubber roller when applying a protective coating to the pipe with an effort not less than 30 n / cm. After rolling, the protective coating was heated in a chamber with infrared radiation for its shrinkage and reliable protection of the pipeline.

The productivity of insulation work was 30 m / h. Tests of the obtained coating showed that the adhesion to the pipe metal is 100-130 n / cm. Peeling of the coating over the entire surface of the pipe occurred according to the cohesive type. All other coating tests were carried out in accordance with GOST R51164-98, the standard values of the coating were obtained.

Using the proposed method will guarantee the protection of the surface of pipelines and zones of welded joints in the conditions of major repairs of extended sections of trunk pipelines when applying a protective coating using mechanized route equipment.

Claims (1)

The method of applying a polymer protective coating on the insulated surface of steel pipelines, mainly in route conditions, including preliminary cleaning and heating of the insulated surface, applying it by spiral winding while simultaneously rolling the tape of the heat-shrinkable polymer material of the protective coating with an adhesive thermoplastic layer from the adhesive composition, characterized in that the surface is heated to the melting temperature of the adhesive composition and on the insulated surface additionally, a tape of adhesive thermoplastic material reinforced with a mesh is applied by winding, and a double-layer heat-shrinkable tape is used for the protective coating and applied with tension before the press roller, and after application, the surface of the double-layer heat-shrinkable tape is additionally heated to a shrink temperature using a radiant heating source.