RU2241170C2 - Method of repairing pipelines - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: pressure in the pipeline is lowered down to 6 MPa. The damaged part of the pipe line is provided with round temporary openings with thread, and liquid carbon anhydride is supplied into the pipeline. During phase transition, dry ice is generated and plugs the cross-section of the pipeline thus sealing the damaged part. After the end of repairing, the dry ice is sublimated thus removing obstacle for flowing the fluid through the repaired pipeline.

EFFECT: simplified method of repairing.

1 dwg

Description

The invention relates to techniques for the construction and operation of trunk and local pipelines transporting gas, oil and oil products, as well as pumping stations, and is intended to seal the said pipelines in the process when performing repair and restoration work, for example: eliminating leaks in the pipeline, when repairing or replacing shut-off -regulating pipe fittings (valves, valves, etc.); when creating new nodes of connections to existing pipelines.

Currently, various methods are known for solving the problem [1-4], namely, that initially reduce the pressure in the pipeline by turning off the transfer pumps, then turn off the emergency section using linear valves located both at the beginning and at the end of this section.

After taking all necessary precautions, they begin to open the pipeline at the site of damage, while removing all, for example, oil that was in this emergency section, followed by steam blowing of this section.

However, in practice it is not always possible to completely remove the oil from the pipe. The volume of removed oil products can be quite large, since the distance between adjacent valves is 10-15 km, and the diameter of the oil pipeline can be in the range of 200-1200 mm. In addition, this operation is often impossible to perform due to leaking linear valves.

In this case, another method is used to eliminate the accident in pipelines, in which, to completely isolate the cut from the internal cavity of the pipe, two windows are cut down at the ends of the dismantled section and clay plugs are driven through them.

Before stuffing, the clay is thoroughly mixed until a thick pasty state. In winter conditions, in order to avoid clay freezing, solid oil and diesel oil are added to it while stirring. The clay cork is packed tightly using rammers to prevent the release of gases and product [5, p. 289].

Before the start of hot work in the pit, they take air samples, prepare welding works and fire equipment. After eliminating the damage, the linear valves are opened, the entire pipeline is filled and tested for leaks.

This technical solution [5, p. 289] was adopted as the closest analogue to the claimed method.

A significant drawback of this technical solution is that for its implementation it is necessary to cut down special windows for stuffing clay plugs into the pipeline, which after restoration work must be eliminated: windows by means of hot work - welding, clay plugs - by washing with a moving product. Special filters must be provided to clean the clay contaminated product.

To increase the economic efficiency, fire safety and environmental safety of emergency recovery works on technological pipelines, a new method is proposed for solving this problem, according to which the damaged section is cut off from the rest of the pipeline, without removing product from it, by artificially created temporary plugs of solid carbon dioxide (dry ice) .

These plugs are created by stopping the movement of the product in the pipeline and supplying liquid carbon anhydride (СО ₂ ), otherwise liquefied carbon dioxide, to both ends of its emergency section; for this, special threaded holes are previously created. Carbonic anhydride, when the pressure decreases, due to evaporation, absorbs a lot of heat and turns into a solid white mass (dry ice). Accumulating, this mass of dry ice in the pipeline forms plugs that hermetically block the emergency section. After this operation, they begin fire work to eliminate the accident at the pipeline, at the end of which the supply of liquid carbonic anhydride is stopped; plugs are screwed into previously made holes; the pipeline is heated, under the action of heat, the plugs from dry ice are sublimated (they pass from a solid state to a gas, bypassing the liquid phase), restoring the patency of the repaired pipeline along the entire length.

New in the claimed invention is the operation of cutting off the damaged section from the entire pipeline with special plugs, which are created by phase transition of carbonic anhydride from liquid to solid.

The specified new feature is not identified from the existing level of technology, which allows us to conclude that the claimed invention meets the criterion of "inventive step".

The new feature allows to significantly improve the technical and economic indicators, fire and environmental safety of emergency recovery work on process pipelines due to:

- a significant reduction in the time and cost of emergency repairs due to the low cost of liquid coal anhydride, which is widely used in the food industry;

- ease of storage, transportation and supply of liquid carbonic anhydride, which is stored in steel cylinders at a pressure of about 6 MPa, which ensures its supply to the emergency section by gravity without any pressure devices;

- safety of coal anhydride. It is not toxic, does not burn, does not explode.

The invention is illustrated by the following example of a device that implements the claimed method. In this example, a section of an oil pipeline laid in a swamp and broken as a result of pipe subsidence is presented as an emergency process pipeline.

The implementation scheme of the claimed invention by the example of the specified emergency recovery operation is shown in the drawing.

To restore the pipeline 1. having a damaged section 2, use steel cylinders 4 filled with carbonic anhydride 5, which is in a liquid and partially gaseous state under a pressure of about 6 MPa at ordinary temperature. To supply liquid carbonic anhydride, pipelines 6 with valve 7 are provided.

The method is as follows: when detecting the place of oil exit to the surface in the emergency section of oil pipeline 1, reduce the pressure to values not exceeding 6 MPa (preferably up to 2-3 MPa, maximum to atmospheric pressure), free this section from soil, insulation and find a gap in the pipe 2. Then, to the left and to the right of this gap, small holes 3 with a diameter of 20-25 mm are drilled and a thread is cut into them.

Steel cylinders 4 with liquid carbonic anhydride are turned upside down and connected via pipeline 6, valve 7, through opening 3 to the internal cavity of oil pipeline 3. Next, valves 3 are opened and liquid carbonic anhydride under pressure (about 6 MPa) of the gas cushion enters the oil pipeline 1 where, due to a sharp decrease in pressure, liquid carbonic anhydride boils up, while about 570 kJ / kg of heat is absorbed (at atmospheric pressure). In this case, carbonic anhydride is cooled to a temperature of minus 78 ° С and turned into a dense solid mass (dry ice), which fills the internal cavity of the oil pipeline, forming plugs of dry ice and hermetically disconnecting the working part of the pipeline from the emergency section. After sealing the emergency section of the pipeline 1, close the gap 2 in the pipeline, for example, by electric welding. Next, close the valve 7 and stop the flow of liquid carbonic anhydride, disconnect the pipeline 6 from the oil pipeline 1. After that, the oil pipe 1 is heated at the locations of the plugs. Dry ice, of which plugs 8 consists, is sublimated by heat, i.e. the solid state directly passes into the gaseous state, the resulting gas escapes through holes 3. When oil appears, plugs are screwed into these holes. As a result, the emergency section of the pipeline was restored, previously created plugs of dry ice were turned into gas, the remains of which can be removed from the pipeline without problems through stationary gas-air collectors. The oil pipeline is included in the work, having previously tested it for working pressure.

Similarly, damaged gas pipelines, oil products pipelines and other pipelines transporting explosive and environmentally hazardous products can be repaired.

Sources of information

1. Galeev VB, Karpachev MZ, Kharlamenko V.I. Trunk oil pipelines. - M .: Nedra, 1988.

2. Galeev VB and other. Operation of trunk oil pipelines. - M .: Nedra, 1973.

3. Chernikin V.I. Transfer of viscous and solidifying oils. - M.: Gostoptekhizdat, 1958.

4. Yakovlev V.S. Storage of petroleum products. Environmental issues. - M.: Chemistry, 1987.

5. Durov V.S. and others. Operation and repair of technological pipelines. Reference book. - M.: Chemistry, 1976.

Claims (1)

A method for eliminating an accident at a process pipeline by opening, cutting off plugs and sealing the damaged area, characterized in that the pressure in the said pipeline is reduced to values not exceeding 6 MPa, then round temporary threaded holes are created at the boundary of the damaged area and fed through each of them into the pipeline liquid carbon dioxide (CO _2), resulting in a phase transition liquid - solid obtained dry ice, which is filled with an open area of the pipeline, creating therefrom samples and and seal the damaged area, and after the reconstruction sublimed dry ice and remove the obstacles for passage of product through the restored conduit.