RU2204078C2 - Method of elimination of accidents in oil products pipe line - Google Patents

Abstract

FIELD: construction engineering; sealing-up oil products pipe lines during repair. SUBSTANCE: wells are drilled at boundaries of defective section of pipe line, after which tubes are inserted and cooling agent is fed for converting the oil products to solid state. After elimination of damage, heating agent is fed for converting the oil products to liquid state. EFFECT: enhanced safety of repair work. 1 dwg

Description

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

 Currently, various methods for solving the problem are known [1, 2, 3, and 4], but the method [1, p. 177-178], which consists in initially reducing the oil pressure in the pipeline by turning off the transfer pumps, has found the greatest practical application. , then turn off the emergency section using linear valves located both at the beginning and at the end of this section.

 After taking all the necessary precautions, they begin to open the pipeline at the place of damage, while removing, as a rule, all of the oil that was in this emergency section (in the pipeline between the stationary linear valves).

 The volume of oil products removed 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.

 If, due to the leakage of linear valves, the oil product continues to flow from the pipeline, then a hole is drilled in a lower place of the route compared to the place of damage, and the oil product is pumped through it. At the same time, a dug pit to access the pipe must be isolated from the oil product. After opening the pipe and inspecting the place of damage, a decision is made on how to eliminate the damage by installing a coil (installing a new piece of pipe instead of the destroyed one), a clamp or welding a crack or fistula.

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

 If the results of such tests are unsatisfactory, then almost the entire emergency operation procedure, starting with the release of the pipeline from oil products, is repeated. After the emergency work is completed, they begin to collect spilled oil product, as well as to clean and reclaim the territory.

 This technical solution [1, p. 177-178] adopted as the closest analogue of the claimed method.

 A significant drawback of this technical solution is that for its implementation, due to the significant distances between adjacent valves at the main oil pipelines, pumping into special containers and temporary storage of significant volumes of oil products are required. Since such containers are not always available, for example, in marshlands, they can be delivered to the accident site, often a significant part of oil products is poured onto the surface of the earth, worsening the ecological situation of entire regions.

 In addition, the production of fire (welding) work near oil reservoirs, especially in areas of spills of oil products on the ground, is very dangerous due to the high probability of large fires.

 To increase economic efficiency, fire and environmental safety of emergency recovery work on oil pipelines, a new way to solve this problem is proposed, according to which the damaged section is cut off from the rest of the pipeline without plugging oil from it with artificially created plugs.

 These plugs are created from the same oil product by lowering the viscosity and turning it from a liquid to a solid state by freezing the damaged area predominantly with liquid nitrogen passed through a heat exchanger located in the immediate vicinity of the damaged section of the oil product pipeline. Then this section of the pipeline is sealed by any of the known methods, after which a heat carrier, for example a hot solution of calcium chloride, is fed into the heat exchanger instead of liquid nitrogen, under the influence of which the previously cooled oil product is heated and passes from solid to liquid. At the same time, the artificially created cork disappears, then the transfer pumps are turned on, transferring the entire oil product pipeline to the normal operating state.

 New in the claimed invention is the operation of cutting off the damaged area from the entire oil pipeline with special plugs, which are created by reducing the viscosity of the oil and its transition from liquid to solid state by freezing this area mainly with liquid nitrogen passed through a heat exchanger located in the immediate vicinity of the damaged area oil product pipeline.

 After the damaged section of the pipeline is repaired by any of the known methods, for example, by welding, instead of liquid nitrogen, a coolant is fed into the heat exchanger mentioned above, under the influence of which the previously cooled oil is heated and passes from solid to liquid, the artificially created plug disappears, the oil pipeline is ready for further exploitation.

 These new features are not identified from the existing level of technology, which allows us to conclude that the claimed invention meets the criterion of "inventive step".

New features in the aggregate can significantly improve technical and economic indicators, fire and environmental safety of emergency recovery work on oil pipelines due to
- a significant reduction in the time and cost of emergency repairs due to the low cost of liquid nitrogen, which is a waste product of steelmaking, is made in huge quantities, its cost is about 1900 rubles per ton (in 2000 prices);
- reduction of oil spills;
- performing hot work in a gaseous environment with a high nitrogen content.

 The invention is illustrated by the following example of a device that implements the claimed method. In this example, a pipe section laid in a swamp and destroyed by soil electrochemical corrosion is presented as an emergency oil product 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 oil product pipeline 1 having a damaged section 2, heat exchangers are used in the form of successively connected wells 3, 4 and 5, each of which is equipped with an internal pipe 6. In addition, a cold source in the form of a cryogenic tank 7 and pipelines are provided for supplying liquid nitrogen 8, pipelines 9 and 10 are used to remove gasified nitrogen. To supply heat, a heat source is provided - a heat generator 11, supplying 12 and return 13 pipelines. For switching pipelines, valves 14, 15 and 16 are provided. In order to increase fire safety when performing hot work, a special light tent 17 made, for example, of plastic film can be provided.

 The method is as follows: when a place of oil product exit to the surface is detected, this place is fenced with wells 3, 4 and 5, wells are drilled, which are then supplied with liquid nitrogen from the cryogenic tank 7 through pipelines 8 with open 14 and 15 and closed 16 valves. Liquid nitrogen, entering through the pipe 6 to the base of the well 3, comes into thermal contact, through the walls of the well, through the surrounding soil, through the walls of the oil product pipeline 1 with the oil product.

Due to the fact that liquid nitrogen boils at a very low temperature (-196 ^o C) in the area of well 3, the oil product cools down, in which the latter passes from liquid to solid, forming in this case a tight plug separating the emergency section in a limited section of pipeline 1 2 from the rest of the oil product pipeline 1. In order to save cold, gas, gasified in the well, is passed sequentially through wells 4 and 5 and first released into the atmosphere through pipelines 9 and 10, and then into the pit, reducing the content e oxygen in the air.

 At the same time, swampy soil around wells 3,4 and 5 is frozen, after which the oil product pipe 1 is opened at the site of damage 2. Soil frozen in this way eliminates any influx of water into the pit.

 After opening the pipe and inspecting the place of damage, a decision is made on how to repair the damage. If it is necessary to carry out hot work (welding), for example, installing a coil, a tent 17 is installed above the foundation pit and gasified nitrogen is supplied to it via pipeline 10. Welding in a nitrogen atmosphere eliminates the possibility of a fire. Of course, in this case, the welder must be provided with special devices for breathing in a nitrogen atmosphere.

 After sealing the oil pipeline 1, the supply of liquid nitrogen to the wells 3,4 and 5 is stopped by closing the valves 14 and 15, and the liquid coolant 11 (hot water, an aqueous solution of calcium chloride and etc.), opening the valves 16, through pipelines 12 and 8, through wells 5, 4 and 3 and return pipelines 8 and 13.

 Under the influence of the coolant, the previously cooled oil product is heated and passes from solid to liquid, the artificially created cork disappears, after which the oil product pipeline is put into operation, having previously tested it for working pressure. Then, the repaired section 2 of the oil product pipeline 1 is isolated, manually sprinkled with soft soil and the foundation pit is finally covered. The pipes of the wells 3, 4 and 5 are removed for reuse.

LIST OF SOURCES
1. Galeev V. B., Karpachev M.Z. Harlamenko V.I. Trunk oil pipelines. - M .: Nedra, 1988, pp. 177-178 - prototype.

 2. Galeev VB, Kharlamenko VI, Soshchenko EM 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 B.C. Storage of petroleum products. Environmental issues. - M .: Chemistry, 1987.

Claims (1)

 A method for eliminating accidents in an oil product pipeline by opening, cutting off and sealing a damaged area, characterized in that the damaged area is cut off with oil plugs, which are created by reducing its viscosity and transition from a liquid to a solid state, for this purpose, wells are drilled at the boundaries of the defective pipeline section, in them pipes, into which a cooling agent is supplied, mainly liquid nitrogen, which, entering through the said pipes to the base of the wells, comes into thermal contact through the walls of the wells the surrounding soil and the walls of the oil product pipeline with the oil product, while the latter passes from liquid to solid, forming impermeable plugs on a limited section of the pipeline, separating the emergency section from the rest of the oil product pipeline, then open the oil product pipe and repair the damage therein, after sealing the oil product supply coolant agent into the wells is stopped and the coolant is supplied to the same wells, as a result of which the oil is heated and passes from solid to the liquid state, the artificially created plug disappears, after which the oil product pipeline is put into operation, having previously tested it for working pressure.