RU2714021C2 - Method of trenchless sanitization of worn-out pipelines - Google Patents

Abstract

FIELD: pipelines.

SUBSTANCE: method involves preliminary cleaning of pipeline equipped with flanges of sanitized section with further broaching of non-metallic liner. Length of the liner, after drawing through the sanitized section of the pipeline, is made larger than the length of the named section by value l_k, determined by the proposed mathematical expression. Stretching is performed so that from each end of section of sanitized pipeline the liner projects outwards by value 0.5 l_k adjacent to both end steel flanges of the sanitized section of the pipeline. Metal yokes securing the liner section located inside the sanitized pipeline are installed on the sections of the liner projecting outside the flanges. Polyethylene bushings are welded to the ends of the liner protruding sections, after which the yokes are removed. Then liner bush, which has reducing properties under any climatic conditions of operations, expanding in diameter and reducing length under action of temperature deformation, tightly adjacent to surface of steel flanges of pipeline. Steel flanges of the sanitized sections of the pipeline are connected, for example, with a bolt joint, thus ensuring tightness of joints. Reclamation of pipeline sections up to 1000 m long is possible. Along the length of the liner, longitudinal furrows are made having depth that does not affect its strength. Liner can be a polyethylene liner with specified properties.

EFFECT: invention relates to repair and reconditioning of worn-out pipelines by trenchless method, as well as protection of new pipelines against corrosion and rivulets wear at performance of works in conditions of cold climate of Siberia.

5 cl, 4 dwg

Description

The invention relates to the repair and restoration of worn pipelines in a trenchless manner, as well as the protection of new pipelines from corrosion and brook wear in the oil and gas industry when working at low temperatures (up to minus 40 ° C) in cold climates, for example, the climate of Siberia.

A known method of restoring worn-out steel pipelines by a trenchless method, including preliminary cleaning of a flanged sanitized section of a pipeline, followed by drawing through a sanitized pipeline section of a non-metallic liner made of material with shape memory (Patent RU 2.419.020 “METHOD FOR PIPELINE REPAIR”, IPC F16L 55/16 published on December 27, 2007).

The known method has the following disadvantages.

In the process of broaching the liner, which is called a “stocking” in the said patent, before putting the “stocking” into the pipe being repaired, it is compressed through a narrowing ring, and the shape of the “stocking” is restored after it is installed inside the pipe being repaired. When pulled through a compression ring in a polyethylene "stocking" microcracks are formed due to tensile stress, which significantly reduces the performance of the "stocking".

A significant drawback is the inability to carry out repair work at temperatures below + 10 ° C, since the coupling connection (Celer couplings) used in the process of repairing the pipeline does not allow work at low temperatures. This temperature limitation prevents the repair work on the main oil and gas fields in Siberia in the conditions of high boggy, where repair and construction work due to the impassability of the swamps can only be carried out in winter after they are completely or partially frozen. In addition, the experience with this method shows that the butt joint of the polyethylene "stocking" by welding the ends with the subsequent connection of the sections of the steel pipeline using couplings is often broken. In addition to this, the implementation of the butt connection of the stocking with the coupling is a painstaking and time-consuming work. At the same time, at the junction, the bore of the pipeline narrows, which leads to the formation of deposits at the joint and around it.

It should also be noted that the use of Celer couplings is not possible with the "brook" wear of a steel pipe that has received an egg-shaped cross section, which is often observed in gas condensate fields.

An object of the invention is to develop a method that overcomes these disadvantages.

The technical result is the creation of an effective method of repair and restoration of worn pipelines at low temperatures.

The stated technical problem and the result are achieved by the fact that in the method of restoring worn steel pipelines by a trenchless method, which includes preliminary cleaning of the rehabilitated section of the pipeline equipped with flanges, followed by drawing through a sanitized section of the pipeline of a non-metallic liner made of material with shape memory, the length of the liner after drawing through the sanitized section of the pipeline make a longer length of the named area by the value of l _k , where:

l _k = (L ₀ × k ₁ -ΔL ₀ ) × k ₂ ,

L ₀ = L _article

L _article - the length of the steel pipe sanitized section of the pipeline with welded steel flanges,

L ₀ - the length of the non-metallic liner after a tight fit,

ΔL ₀ - thermal elongation of non-metallic liner,

ΔL ₀ = α × L ₀ (t _p -t _n ),

α is the coefficient of thermal expansion of the material used non-metallic liner,

t _p - operating temperature of the transported medium,

t _n - outdoor temperature at the time of rehabilitation,

k ₁ - coefficient of linear elongation of the liner after crimping in the rollers, depends on the physical properties of the liner material and the ambient temperature. It is determined empirically,

k ₂ - coefficient of linear reduction at the time of tight fit of the liner on the sanitized pipe, depends on the physical properties of the liner material with shape memory. It is determined empirically how the relative reduction of the liner in length when restoring the liner's outer diameter to the diameter of the sanitized pipe at the moment of tight fit, and the liner is drawn through the sanitized section of the pipeline so that the liner extends outward from each end of the section of the sanitized pipeline by 0.5 l _k adjacent to both end steel flanges of the pipeline section to be sanitized, metal clamp is installed on the sections of the liner protruding outward beyond the steel flanges of the pipeline s, fixing the section of the liner inside the sanitized pipeline, polyethylene sleeves are welded to the ends of the protruding sections of the liner, after which the clamps are removed, then the liners of the liner, which has restoration properties under any climatic conditions of work, expanding in diameter and shortening in length under the influence of memory properties tightly fit to the surface of the steel pipe flanges, the steel flanges of the sanitized sections of the pipeline are connected, for example, by a bolted connection, providing a seal I confirm the identity of joints rehabilitated sections of the pipeline. The method can be used to sanitize sections of the pipeline with a length of up to 1000 m. Longitudinal grooves having a depth that does not affect its strength are made along the length of the non-metallic liner. As a non-metallic liner, it is possible to use a polyethylene liner with desired properties. The length of the polyethylene liner is such that, upon completion of the joining of individual sections of the sanitized pipeline, the liner remains in tension for subsequent compensation of thermal elongation when filling the pipeline with a transported medium with a higher temperature. Before drawing the liner through the sanitized pipeline, it is crimped using rollers, and longitudinal grooves of a certain depth are made on its surface, which are used to release air during a tight fit on a steel pipe and to remove gases during operation of the sanitized pipeline.

The essence of the invention is illustrated by the diagrams presented in the drawings:

FIG. 1 is a drawing of a non-metallic liner through a sanitized section of a pipeline;

FIG. 2 - layout of the liner inside the sanitized section of the pipeline;

FIG. 3 is a view of the sanitized section of the pipeline with metal clamps that are temporarily placed on the liner sections protruding from the pipe.

FIG. 4 is a view of the end section of the sanitized pipeline, to the metal flange of which the plastic liner liner fits snugly.

The proposed method is implemented as follows.

On the repaired pipeline, a section of up to 1000 m is allocated, two pits are torn off at the ends of the allocated section, after which a pipe 1 is cut in each of the pits (Fig. 1). Non-metallic liner 2 is pulled through a sanitized pipe section, which is previously cleaned and calibrated, using a winch 3 located in one of the pits. Liner 2 with a length of up to 1000 m of non-metallic material with an external diameter slightly larger than the diameter of the sanitized pipe is preliminarily pulled using a hydraulic winch 3 through the installation of 4 crimp rollers (Rolldown) in order to temporarily reduce the outer diameter. Reducing the diameter of the liner makes it easy to drag the liner through a steel pipe with a hydraulic winch. Installation 4, having crimp rollers, is also equipped with cutters that make longitudinal furrows of a certain depth on the liner. Furrows are used to release air during a tight fit on a steel pipe and to remove gases during operation of the sanitized pipeline. Steel flanges 5 are welded to the ends of the section of the sanitized pipe (Fig. 2).

The length of the liner l _k , which is placed in the sanitized section of the pipe, is made longer than the length L _{article of the} named section (pipe length with welded steel flanges). The liner 2 is placed inside the pipe 1 in such a way that from both ends of the pipe the liner protrudes outward at a distance of 0.5 l _k . The liner length l _k is determined by the following relationship

l _k = (L ₀ × k ₁ -ΔL ₀ ) × k ₂ ,

L ₀ = L _article

L _article - the length of the steel pipe sanitized section of the pipeline,

L ₀ - the length of the non-metallic liner after a tight fit,

ΔL ₀ - thermal elongation of non-metallic liner,

ΔL ₀ = α × L ₀ (t _p -t _n ),

α is the coefficient of thermal expansion of the material used non-metallic liner,

t _p - operating temperature of the transported medium,

t _n - outdoor temperature at the time of rehabilitation,

k ₁ - coefficient of linear elongation of the liner after crimping in the rollers, depends on the physical properties of the liner material and the ambient temperature. It is determined empirically,

k ₂ - coefficient of linear reduction at the time of tight fit of the liner on the sanitized pipe, depends on the physical properties of the liner material with shape memory. This coefficient is determined empirically, as the relative reduction of the liner along the length when restoring (increasing) the outer diameter of the liner to the diameter of the sanitized pipe at the time of tight fit.

After broaching, the liner is clamped at both ends of the pipe near the steel flanges 5 using clamps 6. At the same time, 0.5 l _k shanks protrude outward on each side of the liner. This estimated length on each side of the liner is selected based on the reduction of the total liner length and tight fit, as well as taking into account the residual voltage in the liner to compensate for thermal expansion when the temperature in the pipeline that existed during the work and the working temperature when through the pipeline the transported medium is moving.

Then, polyethylene sleeves 7 are welded from two ends of the PE liner and the clamps are dismantled 6. The liner, the material of which has shape memory, being in specific temperature conditions, decreases in length and is drawn into the sanitized pipe until the polyethylene sleeves 6 sit tightly on the steel flanges 5 of the sanitized pipe 1.

In FIG. 2 shows the left end of the sanitized pipe 1 at the moment when the polyethylene sleeve 7 is already welded, and the collar 6 has not yet been removed. In the same FIG. 2 shows the right end of the pipe, which is already docked to another sanitized section of the pipeline. The flanges 5 of both sections are connected by means of a bolted connection (not shown).

A general view of the sanitized pipe section with bushings 6 fixed at both ends of the pipe is shown in FIG. 3.

During the tight fit of the liner as it expands inside the steel pipe, air bags may form in the gap between them. In this regard, to remove air in the annulus, as well as with slight diffusion of gas through the liner material from the transported medium, a vent valve 8 is installed on the steel pipe at a distance of 80-100 mm from the edge of the flange to discharge gas or air (Fig. 3 and 4).

The liner, tightly fitting the inner diameter of the metal pipe, creates a barrier protection against corrosion between the steel pipe and the transported medium. After completion of the rehabilitation of the pipeline, the flanges of the sections are connected with stainless bolts and waterproofed. Shaped parts of the pipeline (bends, tees, etc.) are also sanitized in the factory with subsequent installation for continuous barrier protection of the pipeline from aggressive transported medium.

It should be noted that the liner is previously calculated on the critical pressure P _crit in the annulus, at which the stocking can collapse along the cross section (collapse) due to a sharp drop in the pressure of the transported medium.

where P _crit is the critical external pressure in the annulus causing collapse,

H and m are factors affecting the density of the liner on the sanitized pipe. With a tight fit, H = 1, m = -2.2,

E is the modulus of elasticity in bending polyethylene,

D is the outer diameter of the PE liner,

t is the liner wall thickness,

k is the safety factor equal to 1.5,

ν is the Punch coefficient (0.48 for a polyethylene liner).

The method allows to reduce the deposits of salts and paraffins on the inner surface of the pipe. In this case, it is possible to increase the design throughput of the pipe after its sanitation to 10%, due to a decrease in hydraulic friction in a non-metallic liner compared to friction in a metal pipe before its sanitation.

This method allows you to block through the hole through the hole in the pipe (fistula) with a calculated ratio of the diameter of the through hole D to the liner thickness t (D / t) taking into account the pressure and temperature of the transported medium. Namely, based on these parameters established as a result of pipeline diagnostics, or on the basis of a conclusion on industrial safety, as well as taking into account throughput, the liner is designed, selected and calculated, for example, from polyethylene for sanitation of the pipeline.

The tests showed that the use of this method on condensate pipelines during gas production gives a great economic effect due to the reduction of abrasive brook wear of a polyethylene liner compared to a steel pipe (4 times). At the same time, temperature compensators on the repaired pipeline are not required due to the low heat transfer coefficient of polyethylene.

The accumulated experience in the application of the proposed method for pilot projects in Western Siberia has confirmed high efficiency in the performance of work and a large economic effect. At present, the service life of the pipeline in an aggressive environment of swamps and aggressive transported mixture, representing a mixture of oil, gas condensate, high concentration mineral water, is 3-5 years.

After the rehabilitation of the pipeline by the proposed method, its service life can be extended to 50 years. At the same time, repair costs make up no more than 60-80% of the cost of building a new pipeline, taking into account the fact that over 50 years it is necessary to repeat new construction 10 times. After the rehabilitation, there is no need for the cost of anti-corrosion measures.

The proposed method is applicable at any time of the year, allows you to work at sections of the intersection of the sanitized pipeline with roads, other pipelines, water barriers and other obstacles and communications without the corresponding labor-intensive work.

These facts confirm the industrial applicability of the proposed method.

Claims (16)

1. The method of trenchless sanitation of worn-out pipelines, including preliminary cleaning of the flanged section of the pipeline equipped with flanges, followed by drawing through the sanitized section of the non-metallic liner pipeline, characterized in that the length of the liner, after drawing through the sanitized section of the pipeline, makes the length of this section longer by l _k , Where: l _k = (L ₀ × k ₁ -ΔL ₀ ) × k ₂ ; L ₀ = L _Art ; L _article - the length of the steel pipe sanitized section of the pipeline; L ₀ - the length of the non-metallic liner after a tight fit; ΔL ₀ is the thermal elongation of the non-metallic liner; ΔL ₀ = α × L ₀ (t _p -t _n ); α is the coefficient of thermal expansion of the material used non-metallic liner; t _p - operating temperature of the transported medium; t _n - outdoor temperature at the time of rehabilitation; k ₁ - coefficient of linear elongation of the liner after crimping in the rollers, depends on the physical properties of the liner material and ambient temperature, is determined empirically; k ₂ is the linear reduction coefficient at the moment of tight fit of the liner on the sanitized pipe, depends on the physical properties of the liner material with shape memory and is determined empirically as the relative reduction of the liner in length when restoring the liner's outer diameter to the diameter of the sanitized pipe at the time of tight fit, broach through the rehabilitated pipe liner section is controlled so that with each end portion of the rehabilitated pipe liner projects outwardly by an amount 0,5 l _k is adjacent to two end Art metal flanges are installed on the sections of the liner protruding outward behind the steel flanges of the pipeline, fixing the portion of the liner located inside the sanitized pipeline, polyethylene sleeves are welded to the ends of the protruding sections of the liner, after which the clamps are removed, then the liners of the liner having restoration properties when any climatic conditions of work, expanding in diameter and decreasing in length under the action of memory properties, fit snugly surface of the steel pipe flanges, the flanges sanitized steel pipe sections are combined, e.g., by bolting, providing tightness joints sanitized pipeline sections. 2. The method according to p. 1, characterized in that sanitize sections of the pipeline up to 1000 m 3. The method according to p. 1, characterized in that as a non-metallic liner a polyethylene liner with desired properties is used. 4. The method according to p. 3, characterized in that the length of the polyethylene liner is such that upon completion of the joining of individual sections of the sanitized pipeline, the liner remains in tension for subsequent compensation of thermal elongation when filling the pipeline with a transported medium with a higher temperature. 5. The method according to p. 1, characterized in that before drawing the liner through the sanitized pipeline, it is crimped using rollers, and longitudinal grooves are made on its surface, which have a depth that does not affect the design strength of the liner, and are used to release air in the period tight fit on a steel pipe and to remove gases during operation of the sanitized pipeline.

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