RU2246068C9 - Pipe, method and device for enhancement of reliability of pipelines - Google Patents

Abstract

FIELD: pipeline engineering.

SUBSTANCE: pipeline comprises pipes provided with at least one optical conducting spiral member set in the screw groove in the pipe surface. The method comprises inspecting pipeline under pressure with optical pulses passing through the conducting spiral member. The defects are indicated by measuring variations of the pulse parameters. The device comprises pickup, monitor, power source, converter of the direct voltage to the alternative voltage, and optoelectronic pair connected with the pickup of the fiber-optical line which forms conducting spiral member. The first input of the monitor is connected with the optoelectronic pair. The second input is connected with the output of the converter.

EFFECT: enhanced reliability of detecting defects.

8 cl, 6 dwg

Description

The invention relates primarily to pipeline technology and can be used in aviation, gas, oil, space rocket, shipbuilding and other industries.

Known pipes collected in pipelines by welding, mechanical interference or thread [1]. Moreover, pipes with a threaded connection contain a cylindrical shell and end threads.

The disadvantage of all of these facilities is the low availability of control and the high complexity of repairs, which often require stopping the operation of pipelines, which leads to enormous losses in the national economy.

This is due to the lack of proper functions in shell structures and the low technical and economic level of existing technologies for monitoring and repairing facilities.

Known pipe with a conductive spiral for monitoring the condition of the underwater hose [2], containing a rubber tube with coatings, between them a wire and a fiber optic element associated with the equipment.

The solution is insensitive to electromagnetic interference, but does not reveal damage to the pipe surfaces, as the element is located inside its wall, and is limited to use in rubber products.

A known method of monitoring oil pipelines is that a sensor cable is mounted near the pipeline, a sensor cable is connected to the monitor and, according to the testimony of the monitor, a leak is detected in the pipeline section [3].

The method determines through defects without stopping the pipeline and access to the structure. It is based on the separation of the conductors of the sensor cable by a synthetic insulator dissolving in oil. It changes the conductive properties of this sensor, cyclically tested by a computer, which is recorded, processed and presented on the display screen by the hardware and software of the monitor. Leak detection (pipeline failure) can be severely delayed. For example, in the cold season, when a small leak occurs, when the soil behind the pillow around the pipe freezes, the oil leaving the pipeline thickens and its mobility worsens, which is important for oil fields in the North of Russia. This mainly depends on the temperature of the volume flowing out per unit time, the product propagation velocity, the distance from the leak to the sensor and the dissolution rate of such a dielectric. Although non-through pipe damage is more common, the method “sees” only a violation of the dividing function of the shell during operation. The leak point is not precisely identified by them, which complicates and increases the cost of repairing the site. Finally, the solution does not work on water, steam pipelines and other facilities.

A device for implementing the method comprises a serially connected perforated tube, a sensor cable containing two insulated conductors, and a monitor [3].

It is ineffective due to the influence of electromagnetic interference. They are excluded using a control cable. Hydrocarbons do not interact with its dielectric. The monitor subtracts the signals from the cables. The leak signal arising on one cable is recorded without problems.

The closest in technical essence to the proposed one is a method of monitoring oil and gas pipelines, which consists in inspecting the pipeline with a piston mechanically moving in it, recording its location along the length of the pipe and the values of the physical fields of the wall with the control equipment of the piston, and after the inspection, wall defects and their characteristics in the pipeline [4, 5].

The method identifies developing and dangerous of them (critical) wall defects, since it is possible to determine the size, increments, development speed and location of damage. Thus, the exclusion of failures is supposed, but the operating costs for monitoring and repairing facilities are poorly taken into account when eliminating the found defect and missing it. It requires internal access to the pipe, equipping it with start-up cameras, a computer network, and thorough software and metrological support. The disadvantage of this method is its low reliability:

1) The coefficient of detectability of defects _Kd does not reach the limiting values here. Basically, due to the signal-to-noise ratio of electrical measurements, as well as the methodological and instrumental errors of non-destructive testing, including problems of comparing the defect with the standard (shape, size, orientation and location relative to the welds, heat-affected zones and the pipe generators - upper, lower), errors in measuring the distance to the defect, etc.

2) Inspection by a piston is much longer than testing a cable sensor by a computer and does not reveal the transition of a developing defect to a hazardous category. The transition occurs when the defect reaches the near-critical size (Griffiths condition), but is not defined in time. The spread of physical and mechanical properties of the material, wall thickness, corrosion, static-dynamic load, etc. The minimum period of the method is set by the sum of the times of monitoring the site, returning to the starting point and preparing the piston for a new examination without taking into account the time of reset and processing of information in the network. The real survey period of objects is more than 2-3 years. But such a universally recognized defect as a crack, which, in particular, is a potential source of failures and severe accidents in gas pipelines, grows up by random jumps and it is not known when. Moreover, the speed of the jump, yielding to the speed of ultrasound in steel, exceeds the speed of movement of the piston by 2-3 orders of magnitude. The magnitude of the jump is not limited: 10%, 400-500 or more% of the critical size - the so-called main crack near the transition point. In case of accidents at gas pipelines, it reaches a kilometer length, at oil pipelines - several meters;

3) The reliability of the piston is hindered by its complexity. It contains: an airtight sectional structure under pressure from an environment with explosion, fire, toxic, and other properties; a drive with a location measuring device; high-precision analog-to-digital channels; special EMV with programs; stable power supplies, printed circuit boards, connectors and soldering; ultrasonic, electromagnetic, and other types of sensors for detecting anomalies in the wall material; magnetizing device, etc. Moreover, all this should work in conditions of an annual temperature difference of 70-90 ° C, which complicates the matter.

Also known is a method and apparatus for repairing pipelines [6], based on the external hardening of the pipe.

In this method, the place of damage to the pipeline is localized to the formation of a main crack, and the pipeline is strengthened before sealing damage after pressure is reduced.

The device contains at least two seals in the form of reinforcing spiral elements wound on the pipe on both sides of the crack, and there are other details.

The disadvantage of such restoration of facilities is the relative complexity and duration of the work, since transport of equipment and workers to the place of damage is required, excavation of the soil around the pipe by an excavator, repair itself, and the like.

In light of the foregoing, well-known technical solutions for the functions, structures, methods and devices for monitoring and repairing facilities potentially do not ensure trouble-free operation of oil and gas pipelines, which in Russian conditions leads (and will lead) to significant material, production, raw materials, monetary and financial, etc. important losses. There are plenty of examples.

The objective of the invention is to increase the fault tolerance of pipelines by identifying and strengthening the defective wall in real time.

Subtasks:

- giving the objects the property of industrial control suitability, including the possibility of timely and accurate determination of the location, size and rate of development of defects;

- properties of wall restoration and reduction of repair volume on pipelines.

The problem is solved in that the pipe having at least one conductive spiral element is characterized in that a helical groove is made on the surface of the pipe, the conductive spiral element is fixed in the helical groove and is designed to interact with a crack on the pipe surface. The helical groove ensures that the spiral element is flush-mounted so that it does not protrude above the pipe surface and therefore does not undergo intensive abrasive wear on the part of the substance flowing through the pipe. The fastening of the spiral element in the helical groove allows direct control of the surface of the pipe, since the spiral element "works" in tension with the pipe. The pipeline according to the invention is characterized in that it is made of these pipes, the conductive spiral element is made of glass that transmits optical vibrations to interact with a defect in the wall of the pipeline. The implementation of the spiral element of glass, conducting optical vibrations, makes it possible to register a defect in the wall of the pipeline, which (defect) extends to the spiral element itself, and the optical pulse detects the defect of the element, thereby determining the defect of the pipeline. A method of monitoring pipelines is that they inspect the pipeline under pressure, record the characteristics of the pipeline wall and determine its defects, characterized in that helical grooves are formed in the pipeline wall and filled with glass, forming at least one conductive spiral element in the pipeline, inspect it optical pulses, and wall defects are determined by the change in the parameters of the pulses. In addition, the screw pitch of the said spiral element is chosen no more than the length of the critical crack of the pipeline, which makes it possible to register all cracks whose size is equal to or greater than the size of the critical cracks. The distance to the defect is found by the product of the length of the pipeline by the ratio of the travel times of the pulses after and before the appearance of the defect, which makes it possible to detect the location of the defect and its prompt correction. Spiral elements of different deformability are formed, and the pipeline failure period is determined by calculation by the values of the deformability of spiral elements and the pipe wall and the time of destruction of the spiral elements. At the same time, the device for implementing the method [3], comprising a sensor and a monitor, is characterized in that it is equipped with an uninterruptible power supply unit connected in series, a DC / AC converter and an optoelectronic pair, which is connected to the sensor by a fiber optic line forming a conductive spiral pipe element , and the first input of the monitor, the second input of which is connected to the output of the voltage to AC converter. Another variant of the device has a laser emitter in the optoelectronic pair, which provides the emission of optical pulses of sufficient power.

The invention is presented in figures 1-6.

Figure 1 shows the options for a pipe with a conductive spiral element, where 1 is a pipe (pipeline), 2 is a wall, 3 is an external screw groove, 4 is an internal screw groove, 5 is a helical pitch of a groove having a value of h;

Figure 2 shows the trapezoidal section of the groove 6;

Figure 3 shows a triangular section of the groove 7;

Figure 4 shows, respectively, sections of an optical fiber, an epoxy matrix, and a double element in a groove 10.

Figure 5 is an approximated diagram of the tensile steel, where σ _in - tensile strength, δ is the elongation at break, 11 is the joint area for loads and strains of pipes and optical fiber.

Figure 6 - diagram and device for implementing the method. The designations of the circuit correspond to Figure 1. The device contains a series-connected uninterruptible power supply unit 12, a voltage-to-AC converter 13, an optoelectronic pair 14 and a monitor 15, connected to the output of the converter 13 by a different input. The pair 14 is connected to the element 8. A welded pipe joint is indicated at 16.

The invention is as follows.

A helical groove is made on the surface of the pipe (see FIG. 1), a conductive spiral element is firmly fixed in this groove and is designed to interact with a crack on the wall surface.

The pipeline is made of these pipes, the conductive spiral element is made, for example, of glass, which transmits optical vibrations, for interacting with wall surface defects in order to, including industrial control of the object in the following way.

A helical groove (positions 3, 4 of Figure 1) is formed in the pipe (item 1 of FIG. 1), for example, by knurling, tap or evaporation of a part of the wall (position 2 in the same place) with a focused laser beam. Filling the grooves with glass (position 8 of Figure 2) is carried out, in particular, by winding optical communication fiber (FOCL) into it, bonded to the wall with adhesion (including epoxy adhesive - position 9). Formed conductive helical layer (PVA) can be performed, for example, with a piston with a snap, in the factory - with productive equipment (threading, winding and other means). There is more metal waste in the threaded groove. The internal element (position 4 in FIG. 1) reveals the abrasive wear of the gas pipeline by mechanical impurities in the natural gas stream, since the surface of the wall is scratched by hard grains of sand and gradually thins.

The formation is carried out along a helical line, the step of which (position 5 of Figure 1) is limited, in particular, to half the length of a critical crack of a cylindrical shell loaded with internal pressure, which allows timely determination of 100% of dangerous longitudinal cracks in the pipeline and its other operational defects. The value of this step is calculated, for example, by the formula

h≤WE / πσ ² ,

where W is the specific work of the destruction of the pipeline;

E - Young's modulus of elasticity of the material;

σ is the average tensile stress.

The knurling (groove) is given, in particular, a trapezoidal cross section (position 6 of FIG. 2) with an average width of 1-10% of its helical pitch. This cross-sectional shape is better than a triangular one (position 7 of Figure 3), since it requires less machining accuracy when placing a finished profile in the optical cable groove and less stress concentrates the pipe wall.

The depth (height) of the groove is set for several reasons. For example, the wall thickness of the manufactured pipes is selected according to the conditions of strength and reliability, i.e. so that the thread and grooves do not reduce the cross section that can withstand design pressures; FOCL did not go outside the wall of the pipe to exclude damage during the construction of the pipeline and transportation of pipes. Monofilament needs a shallow groove, for example 0.3-0.7 mm. Pipes can have factory (construction) insulation.

The beginning (development) of plastic deformations of the pipeline corresponds to the mechanical destruction of glass (see Fig. 5), which is coordinated, for example, by placing a fiber optic link in the groove of pipes pressed by internal pressure. Fiberglass is fixed by its walls, by winding tension and aggregate adhesion (positions 8, 9 of FIG. 2), and since the glass and epoxy matrix are compressed well, the difference in their linear expansion slightly interferes with the operation of the pipe and layer in the temperature range. FOCL does not require identical strength of batches of optical fiber: the physical quantity is inside the “plastic” zone of the steel pipe. The pressure level is set when testing the production of pipes according to the values of the yield area of pipe steel (position 11 of Figure 5) and the deformation of the fiber (2-5%) at the time of its destruction. The operation is carried out, for example, after calibration (expansion) of thin-walled pipes in diameter.

Layers of two PVA (position 10 of Figure 4) with different elongations at break (deformability) additionally determine the rate of development of the defect, because two time counts (t ₁ , t ₂ ) become known at the time of destruction of the layers. The first tear layer with a lower deformability (δ ₁ ), the second - with a larger (δ ₂ ). For example, if the heat supply pipeline is made of steel with deformability δ ₃ , the condition δ ₁ <δ ₂ <δ _{3 is} met. It is believed that the object is operating in a stationary mode.

Assuming a linear model of the tubular steel yield area, the forecast of the pipeline failure time, for which the distance to the defect according to measurements using 2 layers coincided, is calculated. For example, (t ₃ -t ₂ ) = (t ₂ -t ₁ ) × (δ ₃ -δ ₂ ) / (δ ₂ -δ ₁ ). If we assume that (t ₂ -t ₁ ) = 10 days, (δ ₂ -δ ₁ ) = 5%, (δ ₃ -δ ₂ ) = 10%, then the estimated time (t ₃ -t ₂ ) is 20 days . Prior to the expiration of this period from time t ₂ , in particular, with a 2-3-day supply, all necessary measures and activities are performed to prevent an accident. What is important for especially dangerous objects located within the city, at the intersection with the railway, etc.

Get a sample witness (control sample) of damage to the object. The metrology of the proposed approach is based on the metric properties of helical surfaces, the theory of brittle coatings, the laws of fracture mechanics for a long cylindrical shell with a defect loaded with internal pressure, and the possibility of observing (examining) the state of a witness specimen in space and time.

This sample is examined by optical vibrations, in particular, passing optical pulses through it with known parameters. For a high-quality pipeline, an electromagnetic wave propagates in a PVA with some linear attenuation without encountering any tangible obstacles (for example, for a fiber optic communication line with a diameter of 125 μm, the attenuation coefficient of 0.2 dB / km at a wavelength of about 1.6 μm is known). At the end of the pipeline, the wave is reflected at the surface boundary and runs back (back). This periodic process weakens and ceases over time. Register direct or reverse survey electromagnetic wave at points at the ends of the object.

A direct wave is recorded at a point on the opposite end of the pipeline (section) relative to the point of entry of the pulse. The reflected wave is directly at the point of entry. Separation of direct and reflected waves is carried out on a temporary basis. Other separation methods or the use of several methods are possible.

A damaged layer, for example, in the event of a defect in the pipe during operation, reflects part of the wave at the point of discontinuity of the material, part passes further. The ratio of parts depends on the nature of the damage, that is, on the parameters of the defect. When controlled by the direct wave method, its amplitude at the pick-up point accordingly decreases. But this decrease may be the result of several violations of the PVA (for example, a chain of disparate defects). The defect depth is not recorded, that is, this value should be considered larger than the diameter of the used optical fiber (or the depth of the groove into which it is laid), which does not give false positives for minor defects that can occupy a large surface of the object, for example, initial corrosion.

For accurate monitoring of the pipeline, endowed with the property of industrial suitability, the calculated value of the step is set, for example, ... 0.2h, 0.3h, ... 0.7h ... kh, i.e. they control the size of a non-dangerous defect and predict the residual life of the object. The coefficient k≤1 can be correlated with the industry factor of safety factor of the shell structure. The failure-free operation of the pipeline is ensured by timely reduction of the working pressure in it, for example, by a factor of 1.5–2 by the automatic actions of the product transportation control system based on, for example, the absence (i.e., change) of the inspection wave (direct, reflected) at the corresponding points of the pipeline.

After registering the vibration parameters, depending on the situation “there is / is not a change in the parameter”, the presence or absence of a defect in the object is established. The geometric size of a detected defect under the conditions specified in the description text is about h. In some cases, depending on the shape and location of the defect relative to the PVA coils, the “fragility” of the layer material, the size will be smaller, for example, for a surface crack symmetrical to the coil.

The distance to the defect is found by the product of the length of the pipeline by the ratio of the optical pulse travel times in the PVA after and before the appearance of the defect. For example, for a pipeline with a length of L = 1 km and pulse travel times after and before a crack appears, respectively, t = 25 μs, T = 1000 μs, it will be, as follows from the mathematical formula X = Lt / T, from one of the pipe ends 0.025 km . The pulse repetition is determined by the alarm time: once per second, minute, etc., which also allows you to specify the time moment of the interaction of the layer and the defect.

The advantage of point-to-point input, which independently takes into account the separation of PVA into parts, is the absence of the need for urgent layer repair. What is important from the point of view of ease of use of a spatially distributed system, which is the pipeline. The equality of the number of entry points to the number of crane platforms (compressor, pumping stations) of the facility is possible. This will probably be the best solution due to duplication (reservation) of input points.

If the surface of the butt weld (position 16 of Fig.6) is without PVA, then for a 12 m section with 2 cm edges, the calculated _Kd = 0.996 (6), with 1 cm edges - 0.998 (3). For a fully formed layer, _Kd = 1. During the installation of the butt joint 16 PVA spliced by welding.

In the stated control method for repairing the defective wall, the crack is covered by reducing the working pressure in the pipeline 1, which prevents the development of the defect during the subsequent action, and the heat transmitted by the layer of optical vibrations transmitted through the crack is used.

The attenuation in the whole part of the PVA is small and the focused radiation propagating in such a waveguide is automatically concentrated by the groove in the crack opening and there relaxes due to multiple reflections and associated losses. The crack faces are expanded by thermal expansion of the metal, for example, in structures of aluminum and its alloys and interact in contact.

Temperature, speed, and heating time are controlled by the flow of heat in the opening. For example, the switching on time of oscillations from two entry points, including so that there are no new breaks in the PVA and loss of reflection waves, using emitters of higher energy power.

The crack boundary is melted and smoothed, which reduces the wall discontinuity at the weld point. In the process of cooling, the voltage of the wall is reduced by choosing the duration, number and amplitude, for example, of laser pulses transmitted by the PVA per second. Under certain conditions, it is possible to join the edges of the crack by soldering.

A device for implementing the method works as follows (see Fig.6). An uninterruptible power supply unit 12 (batteries in combination with a power line, a gas station and a rectifier) supplies the elements of the device with energy regardless of interruptions in power supply. The Converter 13 generates the specified oscillations (pulses) using an optoelectronic pair 14 (made, for example, with a laser emitter, photodetector and prism) in FOCL 3 (4) —pipeline sensor 1, and from the line to the monitor 15 (sample-storage device, analog-to-digital converter, computer, system and subject software, drivers). The parameters of the optical pulses do not change while the damage growing during the operation of the object is less than h. When the size of any damage reaches h, the PVA breaks at the defect point and the pulse travel time decreases. In proportion to the position of the defect along the pipeline. This is recorded and recounted by means of the monitor in the distance according to the mathematical formula of the description. The laser of the semiconductor pair 14 emits short and powerful optical pulses without thermal overheating. The error in finding the distance to the defect (longitudinal coordinate) is specified only by the PVA step, since the relative error of laser measurements (second standards ~ 10 ^-12 , meters ~ 10 ^-10 ) is small. The error of the angular coordinate can be less than 1-3 °. The recovery of the defective wall is provided by the device emitter.

The effect is maximum at the main gas and oil pipelines operating under high internal pressure. Less on heating mains, where fracture failure does not prevail. Failures of objects and their emergency stop for repair are practically excluded.

Costs for the economic effect, taking into account the completeness and implementation options, are expected to be up to 10% of the cost of pipes of a similar pipeline without the proposed functions.

Thus, the invention improves the reliability of pipelines, improves the ecology in the field and the preservation of the human environment.

Sources of information

1. NATIONAL STANDART OF CANADA. CAN3-Z163-M86. OIL PIPELINE SYSTEMS./ CANADIAN NATIONAL STANDARD. CAN3-Z183-M86. OIL PIPELINE SYSTEMS. (TRANSFER). (Translation made by the scientific and technical center "Oil and Gas Diagnostics") SAMARA. Publishing House "Samara House", 1994, 196 p.

2. Application for European patent EP 0025344 A1,18.03.1981.

3, 4. Kollakot R. Diagnosis of damage. Per. from English - M .: Mir, 1989, p. 220-222, 440-443 (prototype).

5. Technical means of diagnosis. Reference book / Under the general. ed. V.V. Klyueva. - M.: Mechanical Engineering, 1989, p. 601-612.

6. Patent No. 2118738 for the invention “Method and device for repair of pipelines”. Posted on 09/10/98. Bull. Number 25.

Claims (8)

1. A pipe having at least one optical conductive spiral element, characterized in that a helical groove is made on the surface of the pipe, the conductive element is fixed in the helical groove and is designed to interact with a crack on the surface of the pipe. 2. The pipeline, characterized in that it is made of pipes according to claim 1, the conductive element is made of glass that transmits optical vibrations, for interaction with a defect in the wall of the pipeline. 3. The method of monitoring pipelines, which consists in inspecting the pipeline under pressure, recording the wall characteristics and determining its defects, characterized in that helical grooves are formed in the pipeline wall and filled with glass, forming at least one conductive spiral element in the pipeline, they are examined by optical pulses, and wall defects are determined by a change in the parameters of the pulses. 4. The method according to claim 3, characterized in that the helical step of the said spiral element is chosen no more than the length of the critical crack of the pipeline. 5. The method according to claim 3 or 4, characterized in that the distance to the defect is found by the product of the length of the pipeline by the ratio of the travel times of the pulses after and before the appearance of the defect. 6. The method according to claim 3, or 4, or 5, characterized in that the spiral elements of various deformability are formed, and the pipeline failure time is determined by calculation by the values of the deformability of the spiral elements and the pipe wall and the time of destruction of the spiral elements. 7. A device for implementing the methods according to claims 3 to 6, comprising a sensor and a monitor, characterized in that it is equipped with a series-connected uninterruptible power supply unit, a voltage to AC converter and an optoelectronic pair, which is connected to the sensor by a fiber optic line forming a conductive spiral element pipeline, and with the first input of the monitor, the second input of which is connected to the output of the DC-to-AC converter. 8. The device according to claim 7, characterized in that in the optoelectronic pair, the pulse emitter is made in the form of a laser.

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