A method for restoration of an insulation of a pipeline

Abstract

The present invention relates to a method for restoration of the insulation of pipelines, especially gas pipelines, buried underground. The innovative method comprises the primary cleaning of the dug up pipeline, removing the old insulation, followed by the secondary cleaning (of the pipeline till the required degree of cleanliness according to ISO 8501-1 is reached. Besides, the secondary cleaning of the pipeline is conducted by sand blasting cleaning, dry ice cleaning or high-pressure water jet cleaning. The pipeline cleaning is followed by restoration of the insulation of the pipeline, which includes wrapping of the insulation and protection tape spirally around the cleaned and treated with a primer outer surface of the pipeline.

Description

A METHOD FOR RESTORATION OF AN INSULATION OF A PIPELINEDESCRIPTIONField of the invention

[0001] The present invention relates to a method for restoration of the insulation of pipelines, of gas pipelines buried underground in particular.Background of the invention

[0002] The German patent application publication No. DE4404473 discloses a method for restoration of pipelines in which cleaning of a pipeline is conducted with ultrasound, and restoration of the insulation is carried out using a viscous synthetic material comprising fibreglass particles. A similar method for restoration of pipelines is disclosed in the international patent application publication No. W09808019. Said methods are labour consuming as the use of viscous synthetic materials requires many additional preparatory steps to be completed.

[0003] The Russian patent publication No. RU2325585 discloses a method for protection against corrosion of pipelines that transport gas or liquid. Method includes cleaning of external pipeline surface from old coating and rust, applying a layer of primer on pipeline external surface, spiral winding of insulating anticorrosive material and spiral winding an external layer of polymer tape on layer of insulating anticorrosive material, wherein spiral winding of the insulating anticorrosive material is done on wet primer and wherein the insulating anticorrosive material is a layer of bitumen -polymer mastic compound, which has reinforcing glass mesh in it. This method also requires additional preparatory steps, like preparation of the primer by heating and mixing, preparation of the layer of bitumen-polymer mastic compound. Moreover, the method requires a use of reinforcing glass mesh, which complicates application of this method even further.

[0004] The aim of the invention is to eliminate the above-mentioned drawbacks, namely, reducing costs, improving insulation restoration speed, the quality and service life of the restored insulation over the prior art.Summary of the invention

[0005] The aim of the invention is achieved through creation of a method for restoration of insulation of a gas pipeline buried underground with a reduced labour input as well as increase insulation quality by increasing its corrosion resistance and mechanical resistance.

[0006] The method of the present invention comprises the following steps. Step one is digging up of the gas pipeline. Digging up of the pipeline is conducted in such a manner that the outer surface of the pipeline can be accessed from all sides so that the further restoration steps of the gas pipeline insulation can be carried out. The next step is the cleaning of the gas pipeline by removing the old insulation from the outer surface of the gas pipeline. The old insulation is removed using mechanical means, e.g., it is torn off, cut off or removed in any other mechanical way known to the skilled person. Once the old insulation is removed, additional cleaning of the gas pipeline is conducted till the degree of cleanliness of the outer surface of the gas pipeline is reached such that it is not lower than ST / SA2 according to ISO 8501-1 or even ST2 / SA2' / 2 according to ISO 8501-1. The degree of cleanliness depends on the requirements set regarding cleanliness of the outer surface of the gas pipeline. Once step of cleaning of the outer surface of the pipeline is finished restoration of insulation of the gas pipeline can follow. Restoration of the insulation of the gas pipeline comprises the following steps. A primer is applied on the outer surface of the gas pipeline. The primer itself is made of gasoline as a solvent and contains butyl rubber as well as resins for adhesion. After application of the primer if dries of the gas pipeline and the next step as the primary insulation of the gas pipeline may follow. The primary insulation of the gas pipeline includes wrapping of a primary insulation and protection tape spirally around the outer surface of the pipeline. Wrapping of the primary insulation and protection tape spirally is carried out with overlapping, which falls within the range of 45 to 55%, preferably 45 to 50%. After the primary insulation a secondary insulation step follows. The secondary insulation includes wrapping of a secondary insulation and protection tape spirally around the outer surface of the pipeline, which is already wrapped by the primary insulation and protection tape. Wrapping of the secondary insulation and protection tape spirally is carried out with overlapping which falls within the range of 45 to 55%, preferably 45 to 50%. Once both insulation steps are completed, a porosity of the insulation is tested using high voltage testing devices known to the skilled person. After that the final method step is burying of the newly insulated gas pipeline.

[0007] The cleaning of the gas pipeline may be implemented through at least three cleaning methods. The cleaning can be conducted using sand blasting cleaning means, dry ice cleaning means or high-pressure water jet cleaning means respectively. Basically, cleaning of the gas pipeline includes mechanical cleaning methods known to the skilled person.

[0008] The thickness of the primary insulation and protection tape utilized in the process of restoration of the insulation of the gas pipeline falls within the range from 0.7 to 0.9 mm. The primary insulation and protection tape comprising at least three interconnected layers, where the middle layer is a carrier polymer, preferably made of polyethylene, film covered by a butyl rubber adhesive from both sides.

[0009] The thickness of the secondary insulation and protection tape utilized in the process of restoration of the insulation of the gas pipeline falls within the range from 0.4 to 0.6 mm. secondary insulation and protection tape comprising at least two interconnected layers, where the one layer is a carrier polymer, preferably made of polyethylene, film covered by a butyl rubber adhesive from one of its sides that faces already wrapped primary insulation and protection tape. The respective thickness and design of the primary and secondary tapes allow to provide the required protection against gas pipeline corrosion as well as the required protection against mechanical damage of the pipe, preserving convenience of tape wrapping at the same time.

[0010] Determination of parameters of the tapes can be performed by the test methods disclosed in standards ISO 4951 or ASTM D1000.

[0011] Moreover, the thickness of the carrier polymer film of the secondary insulation and protection tape is bigger than the thickness of the carrier polymer film of the primary insulation and protection tape. This further increases pipe protection against mechanical damage. It also improves abilities of the insulation of the pipeline to withstand pressure from the earth that is around and above the pipe when the pipe is buried.

[0012] In addition, the thickness of the inner adhesion layer of the primary insulation and protection tape is bigger than the thickness of the adhesion layer of the secondary insulation and protection tape that faces the primary insulation and protection tape.

[0013] The width of the primary and the secondary insulation and protection tape is between 8 to 17 cm, preferably 10 cm.

[0014] The materials of the adhesive layer as well as of the layer protecting the pipeline against corrosion and mechanical impact are selected so that in combination thereof a synergic effect is provided. Butyl rubber adhesive is selected as the adhesive layer. The layers protecting the pipeline against corrosion and mechanical impact, in their turn, are selected from the group comprising butyl rubber, polyethylene, polyisobutylene or combinations thereof, or similar materials.Brief description of the drawings

[0015] The drawing illustrates through example one embodiment of the invention falling within the scope of the invention as defined by the claims.

[0016] Fig. 1 illustrates a block scheme of the method for restoration of the insulation of a gas pipeline.Detailed description of the embodiments

[0017] The embodiment of the invention is described with reference to figure to illustrate the objectives, the advantages and efficiency of the present invention.

[0018] Fig. 1 illustrates a block scheme of the method for restoration of the insulation of the gas pipeline. The method for restoration of the insulation of the gas pipeline buried underground comprises the following steps: - digging up of the gas pipeline (1) having old insulation; - removing of the old insulation (2) from the gas pipeline by mechanical means; - cleaning (3) the gas pipeline till the degree of cleanliness of the outer surface of the pipeline is reached not lower than ST / SA2 according to ISO 8501-1, wherein the cleaning (3) of the pipeline is performed by sand blasting (31), dry ice cleaning (32) or high-pressure water jet cleaning (33); - application (4) of a primer on the outer surface of the gas pipeline; - primary insulation (5) of the pipeline by means of wrapping a primary insulation and protection tape spirally around the outer surface of the gas pipeline, wherein wrapping of the primary insulation and protection tape spirally is carried out with overlapping of 50%; - secondary insulation (6)includes wrapping of a secondary insulation and protection tape spirally around the outer surface of the pipeline, which is already wrapped by the primary insulation and protection tape, wherein wrapping of the secondary insulation and protection tape spirally is carried out with overlapping of 50%. After restoration of the insulation the respective gas pipeline is buried (7).

[0017] While the object of the invention may be susceptible to various modifications and alternative forms, it should be understood that the invention is not intended to be limited to the particular forms disclosed herein. Rather, the invention includes all the modifications, equivalents and alternatives falling within the scope of the object of the invention as defined by the claims.

Claims

CLAIMS1. A method for restoration of the insulation of a gas pipeline buried underground, wherein the method comprises the following steps:- digging up of the gas pipeline (1) having old insulation;- removal of the old insulation (2) from the gas pipeline;- cleaning (3) the gas pipeline till the degree of cleanliness of the outer surface of the gas pipeline is reached that is not lower than ST / SA2 according to ISO 8501-1, wherein the cleaning (3) of the pipeline is selected form the group comprising: sand blasting (31), dry ice cleaning (32) or high-pressure waterjet cleaning (33);- application of a primer (4) on the outer surface of the gas pipeline, wherein the primer is made of gasoline as a solvent and contains butyl rubber as well as resins for adhesion;- primary insulation (5) of the gas pipeline, which includes wrapping of a primary insulation and protection tape spirally around the outer surface of the pipeline, wherein wrapping of the primary insulation and protection tape spirally is carried out with overlapping which falls within the range of 45 to 55%, preferably 45 to 50%, and wherein the primary insulation (5) of the gas pipeline is implemented by the primary insulation and protection tape comprising at least three interconnected layers, where the middle layer is a carrier polymer, preferably polyethylene, film covered by a butyl rubber adhesive from both sides;- secondary insulation (6) of the gas pipeline, which includes wrapping of a secondary insulation and protection tape spirally around the outer surface of the pipeline, which is already wrapped by the primary insulation and protection layer, wherein wrapping of the secondary insulation and protection tape spirally is carried out with overlapping which falls within the range of 45 to 55%, preferably 45 to 50%, and wherein the secondary insulation (6) of the gas pipeline is implemented by the secondary insulation and protection tape comprising at least two interconnected layers, where the one layer is a carrier polymer film covered by a butyl rubber adhesive from one of its sides that faces already wrapped primary insulation and protection tape, and wherein the thickness of the carrier polymer film of the secondary insulation and protection tape is bigger than the thickness of the carrier polymer film of the primary insulation and protection tape; and- burying (7) of the gas pipeline with the restored insulation.

2. The method according to claim 1, wherein the cleaning (3) of the pipeline is conducted till the degree of cleanliness is reached such that it is not lower than ST2 / S A2'Z> according to ISO 8501-1.

3. The method according to claim 1 or 2, wherein the thickness of the primary insulation and protection tape is between 0.7 to 0.9 mm.

4. The method according to any of claims 1 to 3, wherein the thickness of the secondary insulation and protection tape is between 0.4 to 0.6 mm.

5. The method according to any of claims 1 to 4, wherein the width of the primary and the secondary insulation and protection tape is between 8 to 17 cm, preferably 10 cm.

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