GB2176263A

GB2176263A - Method of protection of the inner surface of pipeline against corrosion

Info

Publication number: GB2176263A
Application number: GB08613639A
Authority: GB
Inventors: Shishkin Viktor Vasilievich; Kryazhevskikh Nikol Fedorovich
Original assignee: Trest Juzhvodoprovod
Current assignee: Trest Juzhvodoprovod
Priority date: 1984-10-17
Filing date: 1985-10-16
Publication date: 1986-12-17
Also published as: WO1986002429A1; AU5195086A; GB8613639D0; DE3590521C2; CA1282308C; FR2571822B1; DE3590521T; FR2571822A1

Abstract

The method consists in inserting into the pipeline a flexible sleeve, moving and pressing it to the inner surface of the pipeline by means of creation of an excessive pressure inside a hollow between the sleeve and the pipeline. Simultaneously with the pressing of the sleeve onto the inner surface of the pipeline, the latter is heated from inside and the difference between the pressures on both sides of the sleeve inserted into the pipeline is controlled.

Description

SPECIFICATION Method of internal anticorrosive protection of pipelines Technical Field This invention relates to construction and operation of pipelines and, in particular, to a method of internal protection of pipelines against corrosion.

Prior Art At present protection of the internal surface of pipelines is a pressing problem in many technical fields. Particularly aurgent is protection of active pipelines since their internal surface is constantly wetted by some liquid, water, for example.

Conventionally, the internal surface of a pipe has to be dried before applying a protective coating. The drying process has to immediately precede the application process or otherwise the internal surface gets wet again by moisture precipitated from the atmosphere.

At present, there are known various methods and devices for internal protection of pipelines against corrosion.

Known in the art is a method for coating the internal suface of a pipe by a cement-and-sand mixture (cf., for example, AMERON Co. pamphlet, New York, 1978, pp. 54#601).

This method is deficient in that it is inefficient since one installation can coat 690 m or a 700 mm pipe.

Also known in the art is a method for internal protection of a pipeline against corrosion, consisting in that a hose of a polymer material is fed into a pipeline, the pipe is heated and the polymer hose is pressed from the inside to the surface of the pipe.

The device realizing this method comprises a means for feeding the polymer hose into the pipeline, a system for feeding a working medium into the pipeline and a heater installed on the pipeline from outside (cf., for example, USSR Inventor's Certificate No. 1 024 653, IPC F16 L 58/ 16,1980).

A serious disadvantage of this method consists in what it cannot be used for coating active pipeline.

This method can only be used by the manufacturer when the heater is moved along the external surface of the pipe.

Disclosure of the Invention This invention is to provide a method for internal anticorrosive protection of pipelines, which ensures effective heating of the internal surface of an acting pipeline and substantial simplification of the pipeline protection technology.

This object is achieved in that in a method for internal anticorrosive protection of pipelines, comprising the steps of feeding a flexible hose into the pipeline, securing the end of said hose, which is turned inside out, to the internal wall of the pipeline, moving the hose along the pipeline, pressing said hose againstthe internal surface of the pipeline by producing an excessive pressure in the space defined by the hose and the pipe, and heating the pipe, according to the invention, the pipe is heated from inside and hose is simultaneously pressed against the internal surface of the pipe, the pressure differential on both sides of the hose fed into the pipeline being suitably adjusted.

This method provides a protective coating of active pipelines and those under construction. This is achieved in that the pipeline is heated from inside.

Simultaneous pressing of the hose to the pipe wall and its heating produce a reliable bonding of the hose and the pipe. The quality of the coating thus made is extremely high, which makes the service life of the pipeline much longer.

This method can be used to provide a protective coating of active pipelines and those still being laid, both on the surface and buried ones.

Since the pressure difference on both sides of the hose fed into the pipeline can be adjusted, the feeding speed can be controlled, and the force with which the hose is pressed against the wall of the pipe can be regulated. This rules out ruptures of the hose and adds to the better quality of the pipe coating.

In the preferred embodiment of the invention the pipeline is heated simultaneously with the hose being fed into the pipe. The quality of the coating this formed is much better because the temperature in the zone where the hose is pressed against the internal surface of the pipe is constant.

It is advisable that the pressure differential is regulated by regulating the pressure of the working medium in the pipeline before the hose fed into the pipe.

This permits prevention of hydraulic and pneumatic shocks on the hose in the pipeline.

In one of the embodiments of the invention the pressure differential is regulated by lowering the pressure in the pipeline before the moving hose and simultaneous communication of the space between the hose and pipe with atmosphere. In this manner ruptures of the hose can be prevented, if they are due to irregular movement of the hose. The vacuum produced in the pipeline in front of the hose provides better conditions for drying the walls of the pipe, the adhesion of the hose to the wall of the pipe is substantially improved. Power is also saved since the pressure drop is localized within the pipeline.

This protects the hose against ruptures and improves the quality of the protective coating.

It is advisable that protectors made of a material capable of producing, in combination with the pipe metal, an electrochemical potential are installed into the annular gap between the hose and pipe simultaneously with the feeding of the hose into this pipe.

This makes the pipeline more reliable since the mechanical protection of the pipeline is supplemented by the additional electrochemical protection which can ward off corrosion even when the hose is not tight.

In one of the embodiments of the invention, after the polymer hose is introduced into the pipeline, another hose made of a non-thermoplastic material is introduced in this pipeline. When the pipe is heated, the polymer hose melts.

This produces a durable and corrosion-proof protective coating made of, for example, a carbonfilled plastic or glass fiber.

In another embodiment of this invention, slip is applied on the internal surface of the pipe before the hose is fed into it, and, after the glass cloth hose has been placed into the pipe, it is heated until the slip melts.

This embodiment provides a stronger and more reliable coating for protection of the pipeline against corrosion in gressive media.

When the slip melts, pores are formed in the coating. But the pressure built up in the glass cloth hose in the process of heating the slip completely prevents formation-of pores in the coating and, consequently, improves the reliability of the pipeline.

It is advisable that the pipeline is heated from inside by pumping heated gas through the internal hose made from a non-thermoplastic material.

In this manner the processes of drying and heating the internal surface of the pipeline can be combined and made simplier.

It is also advisable that the heated gas should be fed in the pipeline to meet the hose introduced into the pipe and released through the pipe into atmosphere. This embodiment of the invention makes drying of the pipe and regulation of the pressure differential on both sides of the hose a much simpliertask.

In accordance with another embodiment of the invention, the pipe is heated simultaneously with the introduction of the hose into it by feeding a combustible mixture into the pipe and igniting it thereafter.

This method provides a build-up of pressure inside the pipeline. This makes the device realizing the method much simplier.

The hose is heated and pressed against the pipe wall atthe same time. The quality of the coating becomes better sincethe hose fills all pores and pits in the pipe wall. The wall of the pipeline cools off prnc#icaIly simultaneouslythroughoutthe length of the pipeline. Relaxation stresses in the coating are reduced and its quality becomes better. In this way the costof the coating is cut down and the coating application process becomes more effective since the hose is pushed forward and pressed against the pipeline walls by the force of the combustible mixture.

In accordance with one of the embodiments of the invention a protective alloy is applied onto the internal surface of the pipeline before the hose is pressed thereto.

This provides an additional electrochemical protection of the pipeline in case the hose is ruptured. Besides, the dissolution products of the protective alloy, for example, an Aluminum-Gallium alloy, are deposited on the wall of the pipeline and form an oxide film which protects the pipeline against corrosion for many years to come.

Other objects and advantages of the invention will become apparent from the following description of preferred embodiments thereof, taken in conjunction with the accompanying drawing. Best Mode of Carrying out the Invention A method of internal anticorrosion protection of pipelines consists in introducing a flexible hose into the pipeline, securing the forward end of the hose, which is turned inside out, on the internal surface of the pipeline, and then moving the hose and pressing it against this internal surface of the pipeline. The hose is pushed along the pipeline and pressed against its walls by the excess pressure built up in the space between the turned out end of the hose and the pipe. The pipeline is heated at the same time as the hose is pressed against the wall thereof.

EXAMPLE 1 A polyethylene hose is introduced into a pipeline, the leading end of the hose being turned inside out and secured to the internal surface of the pipeline.

Air compressed to 0.3 MPa is pumped into the space between the hose and the pipe. A heater is installed into the pipe in front of the hose which pushes it along the pipe. In this way the hose and the heater are moving simultaneously in the pipe.

The internal surface of the pipeline is heated to 150 C. Compressed air presses the hose to the wall ofthe pipe and welds itreliably to this wall. Asthe hose is pushed along the pipeline, a pressure of 0.15 MPa is produced in the space before the hose. This pressure is produced by compressed air fed into the pipe space before the hose end. The air is released to atmosphere through an opening made in the pipe at the end of the coated section. The pressure can be built up by pumping the air out of the pipe space in front of the hose. Prior to installation, the hose is reinforced with wire made of an aluminum alloy.

The pipeline is heated by supplying a hot gas through the hose and, consequently, the pipeline.

The hot gas can be either supplied at the end of the pipeline in the direction opposite to the movement of the hose or at the beginning of the pipeline in the same direction. In both cases the hot gas is released to atmosphere through the hose.

EXAMPLE 2 A polyethylene hose is introduced into a pipeline, a carbon-filled plastic hose being inserted inside the first hose. The leading ends of both hoses are turned inside out and secured to the internal surface of the pipeline. After that, air heated to 150 C at a pressure of 0.2 MPa is pumped into the hose and it starts moving along the pipeline drying and heating the walls. The polyethylene hose melts as it is heated furtheron and, when cooling, itweldsthe internal hose to the wall of the pipeline.

Hot air can also be pumped into the pipeline in the opposite direction to the movement of the hose and released through the internal hose.

EXAMPLE 3 Initially, slip is pumped through the pipeline. After that, using the method described in Example 2, two hoses are introduced into the pipeline. The external hose is made of polyethylene, the internal one of glass cloth.

When two hoses are introduced into the pipeline, the internal wall thereof is heated to 500 C.

The heat melts the slip and welds both hoses to the wall of the pipe.

EXAMPLE 4 Initially, slip is pumped through the pipeline.

Then, two hoses are introduced into the pipeline as described in Example 3. The working medium is pumped into the pipeline is a mixture of oxygen and propane taken in a proportion 1 to 4 by weight. After the hoses are in the pipeline, the mixture is ignited.

The heat produced by the burning mixture heats the internal wall of the pipeline and the hoses are welded thereto.

EXAMPLE 5 A polyethylene hose is introduced into the pipeline as in Example 1.

Prior to introducing the polymer hose into the pipeline, a layer of a protective alloy is sprayed over the internal surface of the pipe. The protective alloy comprises the following, parts by weight: Magnesium~1; Gallium-0,5; The balance--Aluminum.

This alloy is preheated to a temperature of 950 C.

Then the melt is sprayed over the wall of the pipeline using approximately 80 g of the melt for one square meter of the internal surface. Then a polyethylene hose is introduced into the pipeline.

The hose is melted and a protective coating is formed through the heat of the wall of the pipeline.

EXAMPLE 6 A polyethylene hose is introduced into the pipeline as described in Example 1.

When the hose is manufactured, it is reinforced with wire made of a protective alloy, Al-Ga alloy, for example, as described in Example 5.

In case the hose is ruptured, an electrochemical potential is produced between the metal of the pipe wall and the wires. This potential protects the pipeline against corrosion.

The wire in the place of rupture is dissolved and the dissolution products are deposited on the pipe wall as an oxide film which protects the pipeline against corrosion.

Industrial Applicability This invention can be used most advantageously for protection of the internal surface of trunk and distribution pipelines against corrosion. It can be used for anti-corrosion protection of delivery and low-pressure pipelines utilized in land reclamation, public and process water supply systems, and in heat and power generation systems.

In addition, the invention can be used for protection of pipelines for water supply to gas and oil wells and for pumping of chemical products.

The invention can be used both during laying of new pipelines and for protection of active pipelines.

Claims

1. A method of internal anticorrosive protection of a pipeline, comprising the step of introducing a flexible hose into said pipeline pushing forward and pressing said hose to said internal surface of the pipeline by building up an excess pressure in the space between said pipeline and said hose whose end is turned inside out and secured to an internal surface of said pipeline, and heating said pipeline from inside characterized in that the pipeline is heated from inside and at the same time the hose is pressed to the internal surface of the pipeline and adjusting the pressure on both sides of the hose introduced into the pipeline.

2. A method as claimed in claim 1, characterized in that the pipeline is heated simultaneously with the introduction of the hose therein.

3. A method as claimed in claim 2, characterized in that the pressure differential is regulated by adjusting the pressure of a working medium in the pipeline before the hose being introduced therein.

4. A method as claimed in claim 1, characterized in that the pressure differential is regulated by lowering the pressure in the pipeline before the moving hose and, simultaneously, providing communication of the space between the hose and the pipe wall with atmosphere.

5. A method as claimed in claims 1-4, characterized in that protectors are inserted in the annular gap between the hose and the pipe simultaneously with the introduction of the hose into the pipeline, said protectors being made of a material capable of producing, in combination with the pipe metal, an electrochemical potential.

6. A method as claimed in claim 1 and 2, characterized in that a hose made of a nonthermoplastic material is inserted into the polymer hose after the latter has been introduced into the pipeline, the polymer hose being melted by the heated pipe.

7. A method as claimed in claims 1 to 4, characterized in that wherein slip is applied onto the internal surface of the pipeline prior to introducing the hose into said pipeline, and then, after a hose of glass cloth in inserted into the polymer hose, the pipe is heated until the slip melts.

8. A method as claimed in claim 6, characterized in that the pipeline is heated by hot gas pumped through the internal hose.

9. A method as claimed in claim 8, characterized in that hot gas is pumped at the end of the pipeline in the direction opposite to that in which the hose moves and released through the internal space of said hose into atmosphere.

10. A method as claimed in claims 1,2,3 and 7, characterized in that the hose is pushed into the pipeline and heated by first supplying a combustible mixture into said hose and then igniting said combustible mixture.

11. A method as claimed in claims 1 to 10, characterized in that a protective alloy is applied on the internal surface of the pipeline prior to pressing the hose thereto.