Repair of pipelines in wetlands. Operation and repair of pressure pipelines Repair of pressure pipelines

An analysis of publications and a patent search for repair methods for damaged main and distribution pipelines made it possible to divide all existing methods into the following four groups according to technological features and equipment used:

1. Repair methods associated with the complete replacement of the defective section of the pipeline with a new pipeline.
2. Repair methods that involve sealing the damaged section of the pipe from the outside.
3. Repair methods in which sealing is carried out from the inside of the pipeline.
4. Repair methods according to the so-called "pipe in pipe" type, in which a new pipe of a smaller diameter is inserted into the damaged section of the pipeline.

The first group of repair methods is still a traditional technology. Given that the repair associated with the replacement of the damaged section with a new pipe is quite expensive, its expediency follows from the presence of large defects in the pipeline, or its complete wear. The considered methods are easier to implement for open pipelines. Here, the main difficulty is cutting off the pumping product in the defective area and removing its residues from the welding zones. In the case of underground pipelines, a complete opening of the damaged area is generally required, which significantly increases the complexity of the methods, especially in hard-to-reach places.

There are technologies for replacing a defective section of a pipeline with a new pipeline without opening. The essence of these technologies is that the old pipe is destroyed with the help of special devices, and its crushed segments are either removed or pressed into the ground with a conical expander, thereby freeing up a passage for laying a new pipe. The destruction of worn pipes is carried out in two ways - dynamic and static. The dynamic method is carried out using a pneumatic punch moving inside the old pipeline. The static method of pipeline destruction is carried out using a cutting working body, made either in the form of a conical head equipped with a flat knife made of high-strength steel, or in the form of a roller knife (cutter) with an expander. The drive of the cutting working body is carried out using special equipment. Currently, equipment for trenchless repair and replacement of pipelines is manufactured by more than twenty foreign companies. There is no serial production of such equipment in Russia. At the Odessa plant of construction and finishing machines, complexes of the MPS-01, MPS-01-01 type are manufactured to replace pipes with a diameter of 150-250 mm.

As you can see, these technologies are quite complex; they require complex and expensive mechanisms for the destruction of the old pipe and devices for pushing them. The defective section of the pipeline must be dilapidated for its complete and unhindered removal and, moreover, not very curved and extended.

When repairing underwater pipelines, the complexity of the considered methods belonging to the first group increases even more, which is associated not only with the release of the defective section of the pipeline from the soil, but often with its rise above the water level.

To solve the problem of mass repair of main pipelines with corrosion and other damage, focusing only on the technology of electric arc welding with the replacement of damaged sections across Russia in a short time is practically impossible and not economically efficient. Even with the availability of pipes and financial resources for the reconstruction, the replacement of all worn-out pipelines in the country will take decades. In addition, from the point of view of labor and material consumption, as well as manufacturability, the use of electric arc welding is not always advisable, so it is mainly applicable for reconstruction.

Despite the noted shortcomings, the technology under consideration is quite acceptable and effective for emergency repair of pipelines, which have access to damaged areas for their removal and replacement.

To eliminate local and minor corrosion, erosion and other defects, methods of restoring pipelines from the outside have become widespread. Compared with the previous group, these methods are less expensive and require less time to implement. However, the disadvantage associated with the opening of underground pipelines remains. Sealing from the outside can be carried out by various methods, depending on the diameter of the pipeline and the material from which it is made, as well as on the composition and parameters of the transported medium.

Well-known as a temporary, but quick measure to eliminate the leakage of liquid or gas from metal or plastic pipes, methods using metal clamps, couplings, and other clamping devices. As a sealant, ductile metals, rubber seals, sticky synthetic tape, clay plaster are used. In the presence of small cracks, repairs can be made using welding (for gas pipelines - with shutting off the gas supply and observing the relevant safety rules). As a patch, half-couplings can be used, which are welded to each other with longitudinal seams, and with annular seams with the pipeline, or couplings with through holes for welding to the pipe. In some cases, a sheathing is constructed around the defect and a hardening polymer material is injected into the cavity between it and the pipeline. In this case, the role of the coupling is played by a heat shrink tape.

Among the many ways to repair pipelines from the outside, belonging to the 2nd group according to the proposed classification, the leading place was taken by the method of eliminating defects using the “cold” welding technology using polymer composite materials. Based on the results of many years of research and field tests, Gaznadzor LLC tested various materials, identified effective technologies, developed structures with a guaranteed service life of up to 20 years for the repair of pipelines and equipment in the oil and gas industry using the "cold" welding method. Together with specialized institutes, Gaznadzor LLC developed departmental guidance documentation, which was approved by Gazprom and put into effect on October 1, 2000. In accordance with the repair flow chart, the surface of the pipe section with a defect is being prepared, the pipe geometry is being restored using a polymer composite material (PCM). Then, using a PCM adhesive, a glass-polymer composite tape (SPCL) is applied to it, which has a memory of the pipe diameter and strength properties that are higher than those of metal. Installation and fixing of the tape is carried out on the gas pipeline only when the pressure drops by at least 30% of the working one and without stopping the operation of the gas pipeline. The pressure drop is regulated by regulatory and technical requirements in order to ensure the safety of the repair, as well as to enable the repair structure to work. To achieve the necessary adhesion, the SPCL laid on the defect using a template corresponding to the curvature of the outer surface of the pipe is fixed with various clamping devices that provide the necessary force.

The described methods refer to open methods, which, in cases of repairing network gas pipelines in cities, towns or near them, require the opening of the roadway, lawns, the demolition of green spaces, the closure of city highways, followed by reclamation and restoration of disturbed landscaping. As a result, there is a violation of the usual rhythm of life in areas adjacent to the place of work. Thus, the considered group of repair methods is uneconomical due to significant costs.

Methods for repairing pipelines from the inside are trenchless. Sealing can be carried out by different methods. Repair devices are known that make it possible to introduce annular lining liners, special bushings, seals in the form of a flexible patch into the restored pipe, with a rapidly hardening composition with increased adhesiveness applied to its surface or in the form of a hose-like foil.

The largest number of methods in the 3rd group are methods in which the pipeline is sealed by applying a protective restorative coating to its inner surface. Such a coating is obtained in the following way. After preliminary cleaning and drying, a hardening material is injected into the defective section of the pipeline, and then a former is pulled through it, which displaces excess material, and on the inner surface of the pipe, a uniform protective layer of this material hardens over time. In some cases, the protective coating material is placed on the surface of an elastic sheath, which is introduced into the damaged area of ​​the pipeline and inflated. The material is pressed against the inner surface of the pipeline. After the material has cured, the elastic sheath is removed.

In cases of repair by the considered methods of pipelines of large diameters, special devices are offered for applying coatings to the inner surface of pipes. These devices contain a transport module, mechanisms for squeezing out the polymer filling mixture, mechanisms for its radial supply and application to the inner surface, and heating elements for polymerization.

Despite the main advantage of these methods, which is repair without opening the pipeline, they have the following disadvantages that limit their use, especially in the repair of gas pipelines, where high reliability and quality are required.

• The need for sophisticated equipment.
• The need to get the polymer material in the right place and ensure full and reliable contact.
• The strength of the polymer protective coating in cases of high pressure and significant defects, as well as high wear of the pipe, may be insufficient.
• The impossibility of quality control of repair work in the course of their implementation.
• The impossibility of high-quality repair of pipelines laid in soils with high humidity, as well as underwater pipelines.

Methods for repairing pipelines of the "pipe in pipe" type are relatively cheap and fast trenchless technologies, and these advantages often outweigh their main disadvantage - a decrease in the flow area of ​​the pipeline.

The use of metal pipes as repair pipes due to their high bending rigidity is possible only in cases where the worn section of the pipeline is practically straight, and there is also space for the formation of shafts of the required length for the introduction of repair pipes. Due to the noted limitations, repairs using metal pipes are carried out mainly on large-diameter pipelines. With an increase in the length of the repaired section of the pipeline, even if it has a slight curvature, the force required to pull the repair pipes increases. In order to reduce this force, centering guide roller elements are used. The support elements are proposed to be placed on the surface of the repair pipe along a helical line, and when an axial force is applied to the pipe, it is necessary to give it a rotational motion. In some cases, to facilitate installation, the repaired section of the pipeline is filled with water, and a new pipe, supported by a special floating pipe, or pontoons, is floated. After laying, water is removed from the pipeline. As a traction device, a winch and a cable are usually used, pulled through the repaired pipeline from the second opened end of it. Instead of this traditional method of moving sections of repair pipes, pressure can be applied to the inside of these sections, the front end of which is temporarily closed with a plug.

The use of plastic, in particular, polyethylene pipes for repair in this way expands its capabilities, since such pipes, compared to metal ones, have greater flexibility and lighter weight, which means they allow repairing pipelines that are longer and have a sufficiently large curvature. However, if the issue of obtaining the necessary flexibility of a plastic pipe is solved by reducing the wall thickness, then problems arise associated with a loss of strength both for abrasion when pulled into a repaired pipeline, and strength when loaded with internal pressure. This is the main disadvantage of using plastic pipes. It is impossible to prevent abrasion of a repair pipe against the walls of a worn, corroded pipeline, and to ensure strength when pumping a medium under pressure, an additional complex technological operation is required to fill the annulus with plugging material, for example, foam cement.

There are so-called "stocking technologies" of repair, which are assigned to the 4th group, since they are associated with pulling special sleeves into the repaired pipeline, sometimes called stockings. As a result, however, these methods are close to the methods of sealing pipelines from the inside with various polymer compositions.

As a stocking, for example, a synthetic sleeve with glue applied to its outer surface is used. After pulling the sleeve, it is pressed against the inner wall of the pipeline with special rollers or by applying pressure inside.

In other methods, combined sleeves made of composite materials are offered as a protective coating. These sleeves are introduced into the pipeline. Then, directly into them or into the auxiliary hose, a heated gaseous or liquid medium is supplied under pressure. The combined sleeve pressed against the inner surface of the pipe polymerizes and forms a sealed protective film. The auxiliary ru-kav is removed.

Quite close to the “stocking” is the “U-liner” technology, in which a U-shaped (maybe of a different shape) in cross section is pulled into the pre-cleaned repaired pipeline, plastic, most often polyethylene, with its subsequent straightening with the help of a coolant of a certain temperature and the formation of a new one-piece plastic pipeline.

The advantage that distinguishes "stocking technologies" and "U-liner" technologies among the methods of the 4th group is that the flow area of ​​the pipeline is practically preserved. but they are not without the shortcomings listed in relation to the methods of the 3rd group. In addition, one more disadvantage, already indicated for plastic pipes, is added - the possibility of damage to the sleeve or plastic pipe against the walls of a worn pipeline when pulled. And this drawback manifests itself the more, the greater the curvature of the defective section of the pipeline and the greater its length.

Noteworthy are the methods of repairing curved pipelines, in which corrugated pipes are used as a repair pipe. Corrugated pipes or sleeves have low bending stiffness, so they can be pulled (pushed) into. defective sections of highly curved pipelines, even containing bends and elbows. The reason limiting the use of corrugated pipes is the same as for plastic pipes - their low strength. Here we have in mind not only the pressure load strength, but also the contact strength, as well as the tensile strength required when pulling into the repaired pipe. This drawback is eliminated by supplying them with an external wire braid.

The described methods of repair of all four groups, with the exception of the methods of repair of the 2nd group, for minor damage require a mandatory stop of the pumping of the transported product. At the same time, there are quite a few situations when, despite a detected defect or through damage to the pipeline, it is impossible to stop pumping due to the emergence of significant technological and social problems (metallurgical, glass industry, petrochemistry, cooling system reactors of nuclear power plants, supply of heating boilers in winter, etc.).

There are ways to repair damage to pipelines without stopping pumping using cold tapping and bypass line installation.

The method of emergency repair of the pipeline without stopping the pumping includes two main stages (figure below):

1. Emergency shutdown of the damaged section of the pipeline.

Scheme of repair work with installation of a bypass line

a - installation of blocking devices to cut off the damaged area from the main line; b - bypass installation; c - removal of the damaged area and its replacement with a new one; d - dismantling of blocking devices and commissioning of the pipeline

2. Laying and inserting a temporary bypass line for continuous pumping.

The main restoration work on replacing the pipe section is carried out in the usual rhythm, which contributes to improving the quality of installation work. Simultaneously with the start of emergency recovery work to open the pipeline section, collect and pump out the flowing oil product, blocking devices are installed on both sides of the removed section of the pipeline (without emptying it) to cut off the damaged section from the main line, for which two types of complex and responsible operations:

1. Cutting holes in the pipeline.
2. Entering through them overlapping devices.

To do this, at the point of entry of the blocking devices, two branch pipes or split tees are welded to the pipeline, in the flanges of which there are special grooves for installing plugs after the completion of repair work. A special shut-off valve is attached to the branch pipes, to which a mechanism for cutting a hole is mounted. The design of the mechanism allows you to cut holes in the pipeline, which is under the pressure of the pumped product. Holes are drilled with a cylindrical tubular cutter with an end working part. The cutter must be installed very precisely along the axis of the intended hole, and the frame is attached to the flange.

The milling spindle is equipped with a special device that holds the cut piece of metal and allows it to be removed. The rotational movement of the cutter and its feed are provided by a pneumatic or hydraulic drive built into the frame. After cutting the holes, the mechanism is dismantled, the fittings are closed and a device for inserting overlapping devices is installed in its place. The blocking device is a plug in the form of a ribbed cone, mounted on rods, and allows you to keep the working pressure of the liquid in the pipeline.

After cutting holes in the pipeline and dismantling the drilling device, a bypass is connected to the valves, through which the flow of the pumped product is directed. The damaged section is removed and replaced with a new one, then the blocking devices are dismantled, the branch pipes are plugged with special segment plugs, the valves on the bypass line are closed, and the oil product flow is directed through the main pipeline.

In order to comply with safety requirements and fire safety standards during installation work, the pipeline cavity is sealed with various sealing devices.

The so-called "clay plugs" most widely used in low-pressure gas distribution systems are fireclay clay packed in elastic cloth bags and rammed into the pipeline cavity. The length of the plug depends on the nature of the terrain, the quality of the clay, the time of year, the diameter of the pipeline, etc., but must be at least two pipe diameters and guarantee the safety of manual hot work. The stuffing and tamping of the clay cork is usually done by hand. To seal the cavity of the pipeline, in addition to clay plugs, the creation of which is a very laborious and inefficient operation, other methods are also used, the principle of operation of which is based on the introduction of various balls, plugs, scrapers and other mechanical separators into the pipeline, used when replacing sections of oil pipelines in a planned manner.

In the event of an oil or gas leak, there is a high probability of further development of damage, cracks, negative development of the accident, which can lead to an unacceptable cessation of pumping through the damaged section of the pipeline, and therefore the issue of reducing the time of shutting off the damaged pipeline and building a temporary bypass line is very relevant.

Cutting holes with a tubular end cutter should be carried out at low speed so that the cutter teeth do not overheat, jam or break, and therefore at this technological stage there is no reserve for reducing the time of emergency pipeline repair.

Thus, only by reducing the installation time of a temporary bypass line, it is possible to reduce the total time for localization and liquidation of an emergency without stopping the pumping that occurred on the pipeline.

It is also necessary to try to improve the first technological stage - emergency shutdown of the damaged section of the pipeline with the possibility of further repair work in the usual mode.

It is necessary to develop technical means and technology for quickly eliminating the accident and restoring pumping by the trenchless method of the "pipe in pipe" type, as well as without stopping the pumping of the transported product.

A study of existing methods for repairing underground pipelines revealed that technologies that provide for the opening and repair of defective sections with a pumping stop are quite well developed and successfully applied to repair pipelines. But these technologies are quite expensive and not possible in all cases.

If it is necessary to repair pipelines in cramped conditions when finding places of damage under swamps, highways and other obstacles, the most effective are repair methods of the "pipe in pipe" type.

The use of a "cold tie-in" with the simultaneous construction of a bypass line does not solve the issue of reducing the time for the restoration of a damaged pipeline, preventing the occurrence of emergencies associated with the interruption of the supply of energy resources to industrial and social facilities of human activity, which are of a continuous nature.

Solving the problems of improving the accuracy and efficiency of methods for determining leaks, the formation of constrictions and blockages, creating efficient and fast technologies for repairing pipelines using the “pipe in pipe” method, as well as without stopping pumping, would significantly reduce the repair time, loss of transported hydrocarbons, reduce environmental pollution, which is very important.

We can handle tasks of any complexity: we will repair the water supply in a private house and a high-rise building, a commercial building and an industrial facility. We work with autonomous and centralized systems.

Repair of outdoor plumbing is not too difficult due to the availability of communications all year round. Underground networks are considered more problematic. If repair of the internal water supply is required, then the city housing and communal services use the trench method. At the same time, the terms of work are stretched for several weeks, the asphalt or concrete pavement of roads and pedestrian zones becomes unusable.

Trenchless laying of water supply

We offer modern and highly efficient work technology - trenchless repair of water pipes. This saves significant time and labor costs. A lot of specialized machinery and equipment is not required. The cost of services is adequate to short terms and high quality of work.

Use the services of our company and order a high-tech repair of water supply and sewerage using trenchless technology. ECOSERVICE XXI is high-quality services from professionals at affordable prices.

The pipeline, regardless of its purpose and features of use, requires periodic maintenance and repair. At the same time, the features of its operation, the characteristics of the operating conditions and the parameters of the working environment are always taken into account. Timely repair and replacement of underground pipelines allows minimizing the likelihood of an emergency, violations in the operation of heating systems, water supply.

In fact, there are few options for breakdowns that can lead to a system malfunction. The first step is to prevent leaks as much as possible. They can occur both at the joints and in case of mechanical damage to the pipe body. Replacing water pipes or fittings used for connection in this case will be the simplest, fastest and at the same time inexpensive method of restoration.

Special attention is required for outdoor systems that are laid underground. Stocking repair of pipelines is one of the main modern techniques that allows you to restore the operation of the existing system in such a way as to avoid the need to open the trench.

The main signs that require the rehabilitation of pipeline systems are:

• deterioration of physical and chemical parameters of water;
• reduction in their pressure, throughput;
• occurrence of water leaks;
• service life more than 20 years without repair.

Repair of the pipeline by the stocking method allows not only to eliminate the problems that have arisen, but also to carry out diagnostics of the existing system with high efficiency.

Thus it can be done:

• cleaning the inner surface from deposits formed during operation;
• examination of the state of the system;
• restoration with the use of a sleeve (stocking) coating.

As a result of the use of stocking technology, the repair and replacement of the heating pipeline are carried out with maximum efficiency and economy.

Heating main repair

Despite the apparent simplicity of the design of engineering systems, the repair of heating networks almost always becomes a rather difficult task, requiring the involvement of specialized specialists. One of the most effective methods of preventing emergencies is the timely implementation of repair and restoration work and regular preventive maintenance. With this approach, as practice shows, a complete replacement of heating systems will be required much less frequently, due to an increase in the service life by several times.

Features of the repair of heating networks in Moscow are determined based on the parameters of the system itself. First of all, the method of laying pipelines is taken into account. When using an open ("air") way, the technology for performing work, as a rule, is greatly simplified, which leads to a reduction in maintenance costs and the time required for troubleshooting, performing urgent emergency repairs of the heating main.

For pipelines laid in the ground today, the method of trenchless repair and restoration is most relevant. In its use, the overhaul of heating networks will be carried out as efficiently as possible, even taking into account the difficulties of performing any such work in the conditions of the capital. Its essence will be to destroy the old pipeline using a pneumatic punch, and then, advancing the polymer pipe, destroy the worn out old structures.

Plumbing repair

Timely preventive maintenance and high-quality troubleshooting of the water supply system is an effective way to increase the overall reliability of the entire system. At the same time, the repair of an external water supply system, as a rule, is done by the operating organization or contractors specializing in this area of ​​work. Increasingly, their implementation is done without dug trenches, damaged road surfaces, violations of the design of the adjacent territory.

Performing urgent repairs to the water supply, work is being done to eliminate leaks, the need to start the system after a long break in operation, the appearance of extraneous noise. Experience in this area convincingly proves that, if possible, it is worth eliminating faults as soon as possible in order to avoid high costs. Otherwise, the emergency repair of the water supply will be associated with a break in the water supply, the need for more complex restoration work and the elimination of flooding caused by a leak.

pipeline repair cost

There are several determining factors that affect the final cost of pipeline replacement and reconstruction.

1. The purpose of the pipeline system (sewerage, water, heat supply).
2. Type of system (collector, main, internal pipeline).
3. The material for the manufacture of pipes (the complexity of performing operations for welding, cutting, making connections depends on it).
4. The degree of contamination of the network (the estimate for the repair of a heating main or water supply may include additional cleaning of the system).
5. Depths of pipeline laying, relief features (prices for repair of heating mains, water supply networks increase significantly when working on rocky areas or sandy soils).
6. The complexity of the route (the presence of a large number of turns, building density).
7. seasonal factor.

Our company offers its services for the repair of pipelines. We are ready to offer the best prices for the repair of heating mains in Moscow with a guarantee of quality for all types of work. To complete the tasks in the shortest possible time, we have the whole range of necessary special equipment. Contact us!

Steel pipelines. Leaks in steel pipelines can be temporarily eliminated by applying bandages with rubber gaskets. Bandages are tightened with bolts on one or both sides or with a clamp. Small leaks are eliminated by welding linings to the pipeline. Individual holes can be plugged with a bolt. To do this, a hole with a diameter greater than the diameter of the fistula is drilled in the place of the leak, and a thread is cut with a tap. Then a bolt with a sealing gasket is screwed into the hole. Small fistulas and cracks are also welded with gas welding.

Damaged areas with large defects (fistulas, long cracks) are replaced. To do this, cut out the damaged section of the pipeline with a hacksaw or pipe cutter. An insert is cut off from a pipe of the same diameter, less than the length of the cut section by 8-10 mm. Two short threads are cut at the ends of the pipe. At one end of the insert, a long thread is cut and a lock nut and a coupling are driven onto it, at the other, a short thread and another coupling is screwed onto it. The insert is inserted into the pipe so that their axes coincide, and by rotating the insert, the sleeve is screwed onto the end of the pipe, then the second sleeve is driven off and the lock nut is screwed on.

Damaged sections of steel pipelines can be replaced using an adhesive bandage connection, which is a fiberglass impregnated with epoxy glue. Adhesive bandage connection of the pipeline is performed in the following sequence. First prepare the adhesive tape. To do this, fiberglass is cut into strips of certain sizes, depending on the outer diameter of the repaired pipeline. The length of the tape should be such that at least six layers fit in the winding, and the width is assumed to be 20-30% more than the diameter of the damaged pipeline. So that fringes do not form at the edges of the tape, before cutting, the places of cuts are impregnated with BF-2 or BF-4 glue.

Then the tapes are impregnated with epoxy glue. Epoxy glue is prepared directly at the place of work, as it is usable for 45-60 minutes at an ambient temperature of 20°C. Glue with a spatula is applied in an even thin layer on one side of the tape, which is placed on a flat surface covered with plastic wrap. In order for the glue to penetrate the fiberglass, a small force is applied to the spatula.

Before gluing, the outer surfaces of the pipes to be joined are cleaned of dirt, scale and rust. Cleaning is carried out with a mechanized tool or manually with metal brushes, sanding paper, etc. for the entire length of the seam to be glued (width of the tape). After cleaning the surface of the ends and ends of the pipes to be joined, they are degreased by wiping with a swab of rags moistened with gasoline or acetone, followed by open drying for at least 10-15 minutes. So that the pipes to be joined do not move during the work, including the time for the glue to harden, they must be fixed. To do this, the pipe joints are pre-tacked by welding at several points or fixed using various centering devices and fixtures. When using spot welding, the places of tacks must be cleaned and protrude above the surface by no more than 2 mm.

Then, a fiberglass tape with a layer of glue applied to it is wound around the ends of the pipes to be joined. The winding is carried out manually with interference in the radial direction without distortions. The middle of the tape should be located above the junction.

The adhesive bandage connection is kept in a fixed position until the adhesive has completely hardened and acquired the necessary strength.

When performing gluing work, workers should wear protective clothing: overalls or overalls made of thick fabric, hats, thin rubber or cotton gloves, and in some cases goggles. If glue or its components get on the skin, they are removed with cotton wool moistened with acetone, and then washed off with soap and water.

Cast iron pipelines. Methods for repairing cast-iron pipelines depend on their type: pressure or non-pressure. Damaged sections of pressure pipelines are repaired by replacing them. To do this, cut off the socket and remove the damaged area. Then, the insert of the required length is cut off, a sliding sleeve is put on it, and the smooth end is inserted into the socket of the insert. Next, the insert is centered relative to the pipe and the sleeve is shifted. After that, the socket is sealed with a resin strand and an asbestos-cement mixture or cement.

Damaged cast iron non-pressure pipelines are repaired by installing metal plates and rubber gaskets that are pressed against the pipe with wire twist or bolts.

Plastic pipelines. Plastic pipelines have less mechanical strength than metal pipelines, special care should be taken when repairing them - do not apply great efforts, do not overheat the pipes, do not subject them to shocks, do not scratch them. The method of repairing plastic pipelines is also chosen depending on their type: pressure or non-pressure.

Pressure pipelines are repaired by replacing damaged sections. It is not allowed to eliminate defects in welded joints of pressure pipelines by hot gas welding using a filler rod.

When replacing damaged sections, the pipeline is freed from fasteners. The places of the segments are marked with chalk, after which the damaged area is cut out with a hacksaw. Then, from a new pipe of the same diameter and type, an insert is cut out with a length of nine outer pipe diameters greater than the cut out damaged section, and a socket is formed on it. When forming sockets, the ends of the pipes are heated with a blowtorch or in a special bath.

Instead of sockets, a coupling can be welded to the ends of the insert by contact welding. In this case, the length of the insert is taken 10-12 mm less than the length of the cut out section. The insert is welded using a mandrel heated by an open flame of a blowtorch. The temperature of the mandrel is controlled with a thermal pencil or a piece of pipe material, which should melt, but not smoke. After checking the temperature of the welding tool, welding is performed.

You can also use welding in an oblique joint. To do this, the ends of the pipes to be joined are cut at an angle of 45 °, and welding is carried out under pressure applied perpendicular to the axis of the pipeline. When making such a connection, a set of devices is used, which includes a jig for performing a cut, a clamp for vertical clamping of the ends of the mating pipes, a fixing sleeve for temporarily fixing the ends of the pipes to be welded and inserts, a heating tool for melting the ends of the pipes to be welded.

Welding is performed as follows. The damaged area is cut with a hacksaw at a right angle, after which, using a conductor and a hacksaw, the ends of the pipeline are cut at an angle of 45 °. The distance between the upper points of the cut section of the pipeline is measured and a blank with oblique ends and a length of 20 mm longer than the cut section is cut out of the new pipe. One end of the insert is temporarily connected to the end of the pipeline with a fixing sleeve, the other is inserted into a clamp fixed to the pipeline. Then, a heating tool is placed between the end of the pipe and the insert, and it is pressed against the ends of the pipes with a clamp. The melted end of the insert is lifted with a clamp, the heating tool is removed, and the workpiece is lowered and pressed with a given pressure against the melted surface of the pipeline end. The welded joint is held for 5-10 minutes under load. After 20-30 minutes after the complete cooling of the weld, the clamp is removed and the second end is welded in the same way.

Non-pressure plastic pipelines are repaired by applying bandages, wrapping damaged areas with adhesive PVC or polyethylene tape, sticking slips on oil paint or universal adhesives for gluing plastics. Before repair, the edges of a crack or chip are carefully cleaned, degreased and dried.

When repairing pipes made of polyvinyl chloride (PVC) with a diameter of up to 100 mm, an adhesive is used, which includes, wt / h: perchlorovinyl resin - 14-16 and methyl chloride - 86-84. Pipes with a diameter of more than 100 mm are glued with glue, which includes, wt/h: perchlorovinyl resin - 14-16, methyl chloride - 72-76, cyclohexane - 10-12.

For large cracks in pipes (up to 0.6 mm), GIPC-127 glue is used, consisting of tetrahydrofuran (PVC solvent), polyvinyl chloride resin, silicon oxide.

The pipes are glued together at an ambient temperature of at least 5°C. Glued joints should not be subjected to mechanical stress for 5 minutes. The glued knots and pipes are kept for 2 hours before installation.

In some cases, punctures and small holes are repaired by bar welding. To do this, use special gas burners or an electric gun. In the absence of a welding rod, a strip 5-8 mm wide cut from the pipe to be welded can be used.

Heavily damaged sections and sockets of plastic pipelines are replaced in the same way as cast-iron socket pipes. When replacing, use pipes made of the same materials as the damaged pipe.

Threaded connections of steel pipes. When a threaded connection leaks as a result of a poor-quality seal, the connection is disassembled, the old seal is carefully removed, replacing it with a new one, and the connection is reassembled. Linen strand impregnated with red lead, FUM tape or silicone sealing material KLT-30 are used as sealing material.

Threaded connections that are in long-term operation are very difficult to dismantle due to corrosion and drying of the paint used as a sealant. To facilitate the disassembly of the threaded connection, it is heated with a blowtorch, gas burner or poured with boiling water. As a result of these actions, the seal burns out or softens and the connection can be disassembled.

It is unacceptable to tighten threaded connections that were in operation during repair, since a dried linen strand or a squeezed tape will not be able to reliably seal the connection for a long time.

Lock nut leaks occur when there is no groove on the inside of the coupling or there are bumps on the end face of the coupling, which causes the sealing material to extrude and rupture. When disassembling the connection, such a coupling is replaced with a new one. After unscrewing the locknut, remove the old sealing material and clean the joint from paint.

In case of leakage from under the coupling or other connecting part, after disassembling and cleaning the connection, the threads are covered with white. The strand is wound on the thread along its course from the beginning of the thread to the end. The beginning of the thread is considered the first thread on which the coupling will be screwed. Winding is done evenly, without thickening.

When the turns are broken on the long thread of the spur or on the lock nut, the latter, freely rotating on the pipe, does not tighten the sealing material. In this case, the nut or drive is replaced; in addition, the locknut can be replaced by a sleeve. To do this, an additional thread is cut with a die on the long thread of the drive, onto which the coupling is screwed. The additional sleeve rests against whole threads of the thread and, in the presence of sealing material, reliably seals the gap between the sleeves.

When the thread is broken at the end of the pipe, a piece is cut off with a length of at least. 100 mm with a defective thread and a new piece of threaded pipe is welded. If the pipe is located close to the wall and therefore it is impossible to turn the pipe for high-quality welding of the entire seam, then gas welding cuts a hole in the pipe. A burner is inserted into the hole and a part of the seam located near the wall is welded. Then the hole, side and front parts of the seam are welded.

A short thread at the end of the pipe can be extended by 4-5 turns with a die, and a long thread by 8-10 turns. After that, a compensation sleeve is installed, which passes through the defective section of the thread, relying on the newly cut turns.

Threaded connections of plastic pipes. Repair of such connections, made in the form of union nuts, is carried out by tightening them with special keys. It is forbidden to use pipe wrenches for these works and apply great efforts so as not to damage the parts. If the leak is not eliminated by tightening the nut, the connection is disassembled and the gasket is replaced with a new one, which is made of soft rubber.

In case of a leak in a threaded connection of a plastic part with a metal fitting, the connection is disassembled, the part is cleaned of the old sealing material and the connection is reassembled using FUM tape as a sealing material.

Welded pipeline connections. When repairing welded joints, use the same type of welding with which the joint was made. A defective weld seam must not be caulked.

Flanged pipeline connections. When repairing flange connections, bolts are tightened, gaskets are replaced, and flange distortions are eliminated. Tighten the bolts evenly around the perimeter of the flange, starting with the bolts closest to the leak.

In the event that tightening the bolts fails to eliminate the leak, replace the sealing gasket.

At ambient temperatures up to 105 ° C, heat-resistant rubber is used as a gasket, at higher temperatures - paronite 2-3 mm thick.

The flange connection is assembled as follows. The gasket is lubricated with graphite grease and installed in the gap between the flanges. Then bolts are inserted into the holes so that the bolt heads are located on one side of the connection. Nuts are screwed onto the bolts without interference, which, after aligning the gasket, are tightened with a wrench.

Pipe socket connections. Such connections are repaired in various ways, depending on the pressure inside the pipe (pressure or non-pressure) and the material from which it is made.

When repairing the socket joints of cast-iron pressure pipelines, the old sealing material is removed and the socket gap is cleaned, after which the socket is again sealed with a tarred hemp strand twisted into a bundle with a diameter of 7-8 mm, and caulked with an asbestos-cement mixture to a depth of 25-30 mm. The asbestos-cement mixture is prepared from asbestos fiber not lower than group IV (30% by weight) and Portland cement grade not lower than 400 (70% by weight). If cracks are found on the socket, it is replaced.

Repair of socket joints of cast-iron non-pressure pipelines is carried out similarly to the repair of pressure pipelines, but when sealing the joint, the tarred strand should fill 2/3 of the depth of the socket. The rest of the socket is filled with cement grade not lower than 400, which is moistened by adding 10-12% of water from the dry mass, and minted.

To seal the socket, waterproof expanding cement is also used.

Socket connections with rubber ring for plastic free-flow pipelines. When repairing such joints, the gaps in the socket are sealed with a linen strand or staple viscose impregnated with a solution of polyisobutylene in gasoline. The solution before use is aged for a day.

If it is impossible to eliminate the leak or damage to the socket, it is replaced in the same way as replacing the socket of cast-iron pipes. At the same time, the cut end of the pipe, so that it does not damage the rubber sealing ring, should be well prepared: the cut of the pipe must be perpendicular to its axis, on the outer surface of the pipe a chamfer is filed at an angle of 15 ° for a length of 7-8 mm.

Socket welded joints are repaired using bar welding.

The joint of polyethylene pipelines is sometimes restored by introducing a soldering iron heated to 250-300 ° C into the gap between the socket and the pipe wall at the place of the leak. After the material has melted, the soldering iron is removed, and the surfaces to be welded are kept pressed for 2-3 minutes.

Flexible plastic hoses. In case of water leakage at the junction of flexible pipes with a water supply network or fittings, repairs are carried out by replacing the sealing gasket. To do this, unscrew the plastic union nut with a special key and remove the gasket. The new one is made of soft rubber 3-5 mm thick. Before assembling the connection, inspect the threads on the pipe, fitting fitting and union nut.

If defects (burrs, breaks of the first turns) are found on the threads of pipes or branch pipes, it is corrected by screwing a die onto the thread (“driving” the thread). Burrs at the end of the pipe are removed with a file so that the plane of the end is equal and perpendicular to the axis of the pipe. If the thread on the cap nut is damaged, replace it. Instead of a plastic union nut, a metal one is used, which provides a more reliable connection. To install a new union nut, cut off the shoulder, remove the damaged plastic nut and put on a new one so that its thread is facing the end of the flexible hose. With a blowtorch, heat the end of the eyeliner to a temperature of 100 ° C and tear it onto a mandrel clamped in a vise. The liner is advanced along the mandrel until the edges of the pipe, which are in a plastic state, fill the annular groove of the mandrel. The edge of the molded shoulder is leveled with a split hammer. In this way, it is possible to make a new liner from a low-density polyethylene pipe type T with an outer diameter of 12 mm.

PAGE \* MERGEFORMAT 50

Pipe in a pipe

Application

New isolation

over

old

Insulation replacement

Replacement of insulation and partial replacement or restoration of pipes

pipeline section change

Restoration of old insulation

Overhaul of pipelines

With partial opening of the pipe

wires pulling new

polyethylene or steel

Pipeline inside the old

In a trench with a dig under

pipe

ON the trench berm

In a trench with pipe laying

On the beds

With cutting the pipeline into sections and repairing pipes at the base

With parallel strip

With the opening of the pipeline and the processing of old insulation with special and reducing agents

Without opening the pipeline, injection of reducing agents

1. Classification of the overhaul of main pipelines

Overhaul:

Repair or replacement of insulation;

Repair or replacement of linear fittings;

Cleaning the internal cavity;

Repair of transitions;

Repair or replacement of ECP

Overhaul

transillumination of welded seams;

2. Types of repair of main pipelines and their specifics

For emergency repairsinclude work related to the elimination of accidents resulting from the impact on the pipeline of underground corrosion; ruptures of welded joints or pipelines along the pipe body; blockages of the pipeline, leading to its complete or partial shutdown; faults in linear fittings - valves, gate valves, scraper receiving and launching chambers, etc.

After the completion of welding and restoration work on the linear part of the pipelines, the damage to the protective coatings found after opening the pipe is repaired, as well as the isolation of the zones of welded joints using heat-shrinkable tapes and cuffs made of epoxy, polyurethane and other liquid polymer compositions and paints and varnishes.

Maintenance - the minimum in terms of volume and content of scheduled repairs carried out during operation and consisting in systematic and timely work to prevent premature wear of linear structures, as well as to eliminate minor damage and malfunctions.

Current repair is subdivided:

Current repairs include:

Current repairs are divided into:

to preventive, quantitatively and qualitatively determined and planned in advance in terms of volume and implementation;

to the unforeseen, identified during the operation and carried out urgently.

Current repairs include:

maintenance work;

elimination of minor damage to the earth cover above the pipeline;

arrangement and cleaning of drainage ditches, cutting down bushes;

cleaning the internal cavity of pipelines from paraffin, dirt, water and air;

checking the condition and repairing the insulation of pipelines by drilling;

revision and repair of valves associated with the replacement of the stuffing box and lubricant;

repair of wells, fences, coastal fortifications, pipeline crossings through water barriers;

checking flange connections, fasteners, sealing rings, inspection of compensators;

measuring the thickness of the walls of pipelines with an ultrasonic thickness gauge;

preparation of linear pipeline facilities for operation in autumn-winter conditions, during the period of spring floods and elimination of minor damage caused by spring floods;

periodic painting of above-ground pipelines, fittings, metal and enclosing structures.

Measures for the maintenance and current repair of pipelines are carried out mainly without stopping the pumping.

Repair of damage to protective coatings detected during pitting and after ultrasonic thickness measurement is carried out using repair insulating materials similar to those used for applying the main insulating coating.

Overhaul- the largest in terms of volume and content of scheduled repairs, which are carried out when the limit values ​​​​of wear in linear structures are reached, and associated with the complete development, restoration or replacement of worn out or faulty components of structures.

The overhaul of the linear part includes:

all work performed during the current repair;

opening trenches, underground pipelines, inspection and partial replacement of insulation;

repair or replacement of defective sections of the pipeline and valves, their retesting and electrification of valves;

replacement of flange connections, brackets, supports and clamps with subsequent fastening of pipelines to them;

transillumination of welded seams;

cleaning the cavity and testing pipelines for strength and tightness;

painting of aboveground pipelines, fittings, metal and enclosing structures;

repair of wells and fences;

bank protection and bottom protection works at pipeline crossings through water barriers;

construction of protective casings at intersections with railways and highways;

repair and construction of new fire protection structures.

The technological set of works during the overhaul of pipelines approximately corresponds to the set of works for their construction. However, from the point of view of technology, organization and management, it is much more complicated and has its own specific features. In the organization of work, these features are as follows: opening, lifting, cleaning of old insulation, welding and restoration, insulation and laying works and backfilling of the pipeline cannot be combined in a specialized stream, but must be performed in a strict technological sequence .

Features in the technique and technology of work are as follows:

the specificity of the preparatory work, which consists in determining the position of the pipeline;

the presence of a complex of dismantling works preceding the implementation of all other repair and construction operations;

a smaller share of installation work and a larger share of lifting and stacking operations;

the presence of specific operations in the repair of the pipe wall, strengthening joints in the partial or complete replacement of the pipe, section or lash in certain sections of the pipeline;

the complexity and laboriousness of overburden operations where high qualification of the operator is required to prevent damage to the pipe wall by the bucket (or rotor) of the excavator, as well as a significant proportion of manual labor;

the complexity and laboriousness of preliminary cleaning of the pipeline from old insulation and corrosion products, a significant structural difference between special repair and construction machines from the same machines used in the construction of pipelines.

During the overhaul of the linear part of the pipelines, the following main technological works are performed: preparatory, loading and unloading, transport, excavation, lifting and cleaning, welding and restoration, insulation and laying and quality control of work.

3. The structure of the repair of main pipelines

1. Preparatory work

Preparatory work during the overhaul of main gas pipelines includes clarifying the position (in the horizontal and vertical planes) of the gas pipeline, laying out the right of way with cutting the roller and, if necessary, clearing the repair and construction strip from shrubs, trees and boulders.

The correct determination of the position of the pipeline before the start of excavation can significantly facilitate the conditions for opening and ensures the safety of the pipe body. Typically, the position of the pipeline along the route of the repaired section is determined using special route finders or by drilling.

Work on planning the section of the repaired pipeline begins after the allocation of land, obtaining permission to carry out work from the customer and determining the actual depth of the pipeline.

Planning work mainly consists in cutting (usually by a bulldozer) the roller, mounds, bumps, filling low-lying places, etc.

The width of the planning strip for the period of repair of the LCHMT is determined by the project for the production of works; it must be agreed with land users and forestries in advance.

Prior to the start of earthworks, it is necessary to disconnect all electrochemical protection devices and control and measuring columns, to clarify the intersections of the gas pipeline along the route with underground utilities that can be damaged during stripping. Works on the opening of the gas pipeline in the places where underground utilities pass are allowed to be carried out only after official (written) agreement with the organizations in charge of these communications.

2. Earthworks

Earthworks during the overhaul of the linear part of the main pipelines are carried out in strict accordance with the design documentation, based on the following provisions:

the use of the most rational means of mechanization;

timely completion of preparatory work and activities,
ensuring efficient excavation during the entire period;

organization of in-line stripping operations and maximum
their combination in time with lifting and cleaning and insulating and laying works;

compliance with safety regulations, industrial sanitation,

fire and environmental safety.

The type and brand of earth-moving equipment for opening a gas pipeline of various diameters should be selected depending on local geological and topographic conditions. - It is most expedient to carry out earthworks using a special overburden excavator with a shortened middle section, which allows opening the pipeline below the lower generatrix in one pass of the working body.

In the absence of special excavators, the opening of the gas pipeline should be carried out only with single-bucket excavators with a backhoe.

During overburden operations, a single-bucket excavator removes a layer of soil above the pipe and on the right side (along the gas flow) to a depth exceeding the initial laying depth of the pipeline by 80-100 mm, which, during the subsequent planning of the trench bottom, acts as a soft cushion.

Methods for opening the pipeline (fig.)mainly depend on the adopted pipeline repair technology and are carried out in accordance with the PPR. At the same time, one of the main requirements for the dimensions of the trench is the ability to freely perform individual operations in the trench.

Rice. Opening schemes of the main pipeline:

a - a single-bucket excavator on both sides; b - single-bucket excavator on one side; c - construction rotary excavator; g - special overburden excavator

An important requirement for the development of trenches during the overhaul of the linear part is the opening of the pipeline to its lower generatrix without damaging the pipe surface, as well as reducing the share of manual labor. For these purposes, a rotary overburden excavator is used, which opens the pipeline to its lower generatrix in one pass. At present, stripping operations on large-diameter pipelines are mainly carried out by single-bucket excavators.

The next technological operation is digging under the opened pipeline. Soil development in this case must be carried out with a special digging machine such as MPR NITC Rotor, MPT-1020 (720), PT-NN P and MPR.

A self-propelled digging machine is installed on an exposed pipeline and develops the soil under it, creating a technological gap for the normal operation of cleaning, priming and insulating machines. The rotor, developing the soil under the pipeline, moves it to the side pits.

The repaired section of the pipeline (after checking the quality of the insulation and drawing up an act for hidden work) is covered up in order to protect against mechanical damage and temperature influences. Backfilling of the pipeline with the formation of a roller, if necessary, is usually carried out by bulldozers, rotary trenchers or shovel excavators.

3. Lifting of the pipeline and cleaning of the old insulation

Lifting and cleaning works include:

lifting of the exposed section of the pipeline and installation of a cleaning machine;

cleaning of old insulation and visual inspection of the pipe;

bed laying.

The surface of the pipeline during repair is cleaned in two stages:

1. previously - when lifting the pipeline;
2. finally - after performing welding and restoration work.

Lifting and cleaning works are started immediately after opening the pipeline. With the help of lifting mechanisms (pipelayers), it is lifted and a cleaning machine is mounted on it to remove old insulation and corrosion products from the surface of the pipeline. After cleaning, the raised pipeline is laid on the edge of the trench on the beds, the distance between which is determined by calculation. The height of the beds should be sufficient to inspect the pipeline from all sides.

Works on laying the pipeline on supports and its preliminary cleaning are carried out immediately after the penetration of the digging machine.

The technological sequence of works for preliminary cleaning and laying of the gas pipeline includes:

maintenance of the exposed area (while maintaining its position) with a pipelayer and a nozzle on the pipe of a cleaning machine with a detachable working body;

cleaning (preliminary) from the old insulating coating and visual inspection of the cleaned pipe surface;

installation of the cleaned section of the gas pipeline on special supports of the UP type, hydraulic supports, wooden beds "Self-propelled lift - Atlant", etc., while maintaining its position.

With the flow organization of the repair of the gas pipeline, when it is not necessary to restore the pipeline wall, the work is carried out in one mechanized flow, without laying the pipe on supports.

Preliminary cleaning of the repaired gas pipeline consists in removing the old defective insulating coating, corrosion products, scale, dirt, etc. from its outer surface.

The technological operation for cleaning and laying on supports while maintaining the position of the repaired pipeline in the trench can be carried out using two pipe layers and special self-propelled supports.

4. Welding and restoration work

After the pipeline is cleaned of old insulation and corrosion products, the pipe rejection commission begins to work, which should consist of representatives of the customer, the contractor and the regional department of the State Gas Supervision Authority.

Before the inspection, the lashes of the gas pipeline cleaned and laid on the supports must be numbered, tied to the pickets and marked on the working drawings (route profile).

The entire surface of the gas pipeline must be examined to clarify the nature of the damage to the pipe wall. Damaged areas on the surface of the pipe should be clearly fixed with chalk or oil paint to measure their length and area. The dimensions of the defect (depth, length, width) are measured. A special mirror can be used to examine the pipe from below.

Damaged areas must be cleaned from corrosion products to a metallic sheen and clearly outlined along the contour with oil paint. The results of the decision of the working group on assessing the performance of technological facilities should be applied with oil paint on the gas pipeline in places of damage using the following designations: ШЛ - repair with grinding; CB - repair by welding; ZK - coil replacement; VZ - patch welding; PKM - repair with polymer composite couplings; MM - metal couplings.

Based on the results of the survey of the section of the gas pipeline being repaired, an act is drawn up in which specific data are given on the length of the section, the number of lashes, the footage of good, rejected and repairable pipes, and the nature of the damage (depth, length and area of ​​corrosion damage). The act is accompanied by a profile of the route and a survey log.

Welding and restoration work on the gas pipeline should be carried out after the production of work on the rejection of the gas pipeline laid on the beds. The welding and restoration work during the overhaul of the pipeline includes the following: grinding of defects; welding defects; patch welding; installation of sealing sleeves; replacement of coils, replacement of sections with temporary couplings made of various materials (metal, composite, etc.).

Welding of damaged areas must be carried out by manual arc welding.

Sections of the gas pipeline with unacceptable defects are subject to cutting and process coils or pipes are cut in their place.

In the production of welding and restoration work for welding fixed joints, self-propelled welding machines such as SDU AND SCHUA, AS41P, AEP52, etc. are used.

5. Insulating and laying works

Insulating and laying work is carried out in the following sequence: final cleaning of the outer surface of the pipeline, applying a primer (primer), applying a new insulating coating, laying the pipeline to the bottom of the trench or backfilling the repaired area with soil tamping under the pipeline.

6. Testing of the repaired pipeline

When overhauling main pipelines, the following should be carried out:

cavity cleaning, strength test and leak test
gas pipeline during repair with replacement of pipes;

strength test and leak test of the pipeline at
repair with welding and restoration work and replacement
insulating coating or only with the replacement of the insulating coating.

Testing of repaired areas should be done hydraulically.

In exceptional cases (lack of required volumes of water, large height differences, etc.), pneumatic testing is allowed provided that the necessary safety measures are taken, especially when performing pneumatic testing of areas located in energy corridors, in areas of minimum distances from buildings and structures, intersections with other gas and oil pipelines and communications, etc.

A hydraulic test is understood as a strength test and a leak test of a pipeline by creating an internal pressure in a non-working repaired pipeline section above the maximum operating pressure for a certain time using water as a test medium.

Pipelines must be tested according to the project according to a special work instruction drawn up by the construction and installation organization and the customer for each specific pipeline, taking into account local conditions for the production of work.

To conduct hydraulic tests, reliable communication must be equipped along the entire route of the test section (in the absence of uninterrupted communication, testing is not allowed).

The main works on hydraulic testing of the pipeline include:

1. preparation for the test;
2. filling the pipeline with water, removing air;
3. rise in pressure to test;
4. test of endurance;
5. depressurization to the design worker;
6. tightness test;
7. pressure relief up to 0.1-0.2 MPa (1-2 kgf/cm 2 );
8. removal of water from the pipeline.

The pipeline is considered to have passed the test forstrength and tightness test, if during the strength test the pipeline did not collapse (large fistulas and cracks did not open), and during the tightness test the pressure remained unchanged and there were no leaks.

4. Priority areas for overhaul of main pipelines.

The following should be considered as the main criteria for ranking LCMT sites in determining the priority of their withdrawal for major repairs:

1. The degree of importance of pipelines by functional purpose.
2. The technical condition of the pipeline.
3. pipeline operating conditions.
4. Assessment of the consequences of putting the pipeline section into overhaul.

The development of the priority of bringing LCMT sections into overhaul consists in determining the order in which sections of main pipelines are put into repair according to criterion 1.

First of all, those sections of pipelines are subject to repair, where possible accidents will be associated with a danger to human life. The following sections of main pipelines can be classified as priority areas for overhaul:

passing in close proximity to places of compact residence and activity of people;

within the territories of the CS, NS, GDS, SPHG and PRG, tank farms;

transporting oil and gas for export;

at crossings over roads and railways, at intersections with
overhead power lines with a voltage of 500 kV or more, etc.

The development of the priority of bringing LCMT sections into overhaul according to criterion 2 should take into account the service life of the pipeline, the condition of the metal and insulating coating of pipes, information about corrosion and failures of the pipeline.

The priority of sections according to criterion 3 should take into account the operating conditions of the pipeline section to be put into repair, namely:

pipeline design (pipe diameter and wall thickness, laying method, laying depth, presence of ballasting);

technological mode of operation (working pressure and temperature, productivity);

the natural and climatic zone of the pipeline passage (permafrost, swamps, mountainous areas, sea areas, etc.);

the presence of transitions through artificial and natural obstacles;

dimensions of the pipeline security zone (violation of the minimum allowable distances for the passage of the route);

ECP functioning parameters.

The development of priority according to criterion 4 should take into account the assessment of the consequences of the withdrawal of LCCT sites for major repairs, based on:

Volumes of possible shortages of oil and gas;

The cost of eliminating the consequences of a possible accident;

Overhaul costs, taking into account shortages of oil and gas.

The basic principle of overhaul ranking is a two-stage ranking.

At the first stage, it is necessary to evaluate the sections of pipelines to be taken out for repair, according to each of the four criteria indicated above. As a result, all sites will be divided into four groups (Table 1).

Tab. one

The P1 group includes sites that scored four criteria, the P2-3, PZ-2 and P-4 groups - one criterion.

The second stage is the ranking of all four groups of sites according to the degree of corrosion hazard with the allocation of areas of high corrosion hazard (HCR), increased corrosion hazard (HCR) and moderatecorrosion hazard (UCO). Further differentiation of pipeline sections is carried out according to table 2.

Tab. 2

5. Repair methods for the linear part of the main pipelines

1. Repair of the pipeline in a trench with digging under the pipe(Fig. 6.1). On the repaired section of the pipeline, earthen lintels (pillows) 3 m long are left every 10 m, and ten-meter sections are opened with a selection of soil under the pipe to a depth of 40-50 cm. Next, the pipeline is cleaned of old insulation and corrosion products, the pipe walls are restored and an appropriate type of insulation. After repair and backfilling of ten-meter sections, sections of three-meter jumpers are repaired; while all operations are performed manually.

Rice . 6.1. Technological scheme of pipeline repair in a trench

2. Repair of the pipeline with lifting and laying it on the trench berm(Fig. 6.2). The section of the repaired pipeline is opened and the joints are examined. Then the pipeline is lifted out of the trench and laid at a distance of 1.5 m from the edge of the trench on the beds. After pre-cleaning operations, restoration of the pipe wall and application of an insulating coating, the pipeline is lowered back into the trench and backfilled. This method is used mainly on pipelines of small diameters, since there is a risk of damage and rupture of the joints and the pipeline itself when it is lifted.

Rice. 6.2. Technological scheme of pipeline repair with lifting and laying it on the trench berm:

1 - device for clarifying the position of the pipeline; 2 - bulldozer; 3 - overburden excavator; 4 - mobile flaw detection laboratory; 5 - cleaning machine; 6 - pipelayer; 7 - trolley suspension; 8 - welding unit; 9 - lying; 10 - mobile power station; 11 - container for primer; 12 - priming machine; 13 - insulating machine; 14 - device for quality control of the insulating coating; 15 - insulated pipeline

3. Repair of the pipeline on the trench berm (with pipe cutting)(Fig. 63). This repair method is used when replacing damaged insulation and repairing pipes. The section of the pipeline to be repaired is turned off by closing the valves (gate valves) at the beginning and at the end of the section. After removal of the transported product from the pipeline, the section to be repaired is cut out of the pipeline from both ends. After these operations proceed to the main types of work. First, the route is leveled with bulldozers, then the pipeline is opened up to its lower generatrix by excavators, it is lifted onto the trench berm by pipelayers while the surface of the pipes is cleaned from old insulation and corrosion products by cleaning machines and the surface of the pipe is inspected. Next, the restored section of the pipeline is finally cleaned with cleaning machines of the OM type, a new insulating coating is applied using insulating machines of the IM or IL type and laid on the bottom of the trench. Backfilling of the trench is carried out with a roller device, and, if necessary, work is carried out on land reclamation. This method is most widely used in the repair of gas pipelines with the replacement of old or defective insulation using general construction equipment.

Rice. 63. Technological scheme of pipeline repair on the trench berm. (See Figure 6.2 for symbols.)

4. Repair of the pipeline with lifting and laying on the beds in the trench(Fig. 6.4). After laying the route, the pipeline is opened with a bulldozer with a special overburden excavator, lifted from the bottom of the trench by pipelayers, cleaned of old insulation and corrosion products with a special repair and cleaning machine and laid on beds in a trench at a height of 40-60 cm. Beds under the pipeline are placed with a special crane. After the pipes are rejected, welding and restoration work is carried out using mobile welding units, then the pipeline is finally cleaned with a cleaning machine and a new insulating coating is applied with a special repair and insulation machine. For the preparation of bituminous mastic in the repair and construction stream, there are bit-melting boilers. Cleaning and insulation of pipelines is carried out by special repair and construction machines designed for the repair of main pipelines. These machines differ from general construction machines in the design of the working body - they have a detachable one, which allows you to install the machine anywhere in the existing pipeline without cutting it. After laying the pipeline, the trench is backfilled. This method is most rationally applied during the overhaul of the linear part of long-distance main oil pipelines.

Rice. 6.4. Technological scheme of repair with lifting and laying of the pipeline on the beds in the trench:

1 - device for clarifying the position of the pipeline; 2 - bulldozer; 3 - single-bucket excavator; 4 - mobile flaw detection laboratory; 5 - digging machine; 6 - cleaning machine; 7 - supporting device; 8 - mobile power plant; 9 - welding unit; 10 - insulating machine; 11 - device for quality control of the insulating coating; 12 - machine for tamping soil under the pipeline

5. Repair of the pipeline with the laying of a new line parallel to the existing pipeline.Throughout the repaired section from the valve to the valve, or from the CS (NPS) to the CS (NPS), a new thread of the same diameter is laid parallel to the existing section of the pipeline. The whole range of works on laying a new line should be carried out in accordance with the current regulatory documents for the construction of pipelines and taking into account the accumulated experience of construction and installation work on previously constructed main pipelines. The distance between the threads (old and newly laid) is taken depending on the specific conditions of the route and the technical condition of the existing pipeline. After laying a new line, the existing pipeline is turned off and a newly laid line of the pipeline is cut into it. This repair method is used in cases where the pipeline is laid in one thread, or if the pipe has been subjected to severe corrosion damage and it is not advisable to repair it, as well as in cases where it is impossible to stop the section during the repair.

If the pipeline is laid in two threads, then the repair is carried out in three stages.

On I At the stage, along the entire length of the repaired section, a new line of the same diameter (looping) is laid parallel to the existing two lines of the pipeline. After that, one of the existing threads is turned off and a newly mounted thread is cut into the pipeline.

On II At the stage, the second line of the same repair section is disconnected (the first line and the looping pipeline are in operation) and cut out from the main, opened, lifted from the trench, cleaned of the old insulation and laid on the trench berm, examined the metal, while the defective sections of the pipe are cut out and replaced new ones, repair the old ones, finally clean them of rust, cover them with new insulation and lay them on the bottom of the trench. After backfilling, the pipe cavity is purged, the pipeline is tested and put into operation.

After turning on the repaired section of the second thread, work begins III stage. The section of the main pipeline to be dismantled is switched off from work by closing the taps (latches) at the beginning and end of the section. The product is completely removed from the pipeline section and the section is disconnected from the existing pipeline. At the cut points, spherical plugs are welded to the ends of the pipeline remaining in the ground, designed for the maximum working pressure in this section. Preparatory and excavation work, lifting and cleaning of the pipe from old insulation and its rejection are carried out in the same sequence as on II stage. The pipe is cut into lashes, the good ones are transported for further use in the construction and repair of subsequent sections, the rejected pipe sections are taken to a stationary base for repair with subsequent use, and the bad ones are taken to the railway station for shipment into scrap metal. Pipes to be repaired or scrapped are accepted according to the act. The remaining trench is covered, leveled and the land is reclaimed.

6. Technologies for performing emergency recovery work

Causes and types of destruction on gas and oil pipelines

The reasons for the destruction of pipelines are various, we will name the main ones.

1. Violation of the requirements of technology and state standards in the process of pipe production.

2. Deviations from the norms for the design and construction of pipelines.

3. Failure to comply with the rules for the operation of pipelines.

4. Influence of natural phenomena.

During testing and during the operation of pipelines, most of the ruptures and accidents occur as a result of the development of microcracks and fatigue stress of the metal. Any of the listed causes or their combination can serve as a source of microcracks.

As a rule, the destruction of pipelines intended for pumping liquid products (oil, oil products, water, etc.) extends over a section with a length of several tens of centimeters to several tens of meters. The destruction of gas pipelines can reach several kilometers.

Technology of elimination of accidents and damages

The following requirements are imposed on the technology of elimination of accidents:

reliable restoration of the tightness of the pipeline;

ensuring the design level of strength and bearing capacity of the repaired section of the pipeline;

ensuring standard pipeline downtime during repairs;

the least impact on the environment, neighboring communications and national economy facilities;

preservation of the design dimensions of the internal cavity of the pipeline in order to ensure the possibility of passing cleaning and diagnostic tools.

Emergency recovery work includes:

preparatory activities;

localization and collection of the pumped product (release of the localized area from gas);

excavation;

sealing the internal cavity;

welding and installation works;

control of welded joints;

pipeline insulation;

liquidation of the consequences of accidents;

other jobs.

In each case, depending on the nature and location of the accident, as well as depending on the intensity of the pipeline and other circumstances, an appropriate repair method must be selected, namely:

Oil pipelines and oil product pipelines:

The elimination of leakage as a result of the formation of fistulas on the body of the pipe is carried out by installing plugs or clamps. Plugs in the form of plugs are installed on single fistulas. A collar (Fig. 1) or a patch with a clamping device (Fig. 2) is applied to the fistula family and the area of ​​pitting corrosion.

Fistulas and cracks in welds are eliminated by applying and welding special fillet couplings (clamps) (Fig. 3).

Rice. 1. Emergency collar

Rice. 2. Clamping device:

1 - staples; 2 - slats; 3 - nut; 4 - handwheel; 5 - worm; 6 - heel; 7 - slats; 8 - gaskets (petrol-resistant rubber or lead); 9 - swivel; 10 - pipeline; 11 - welded seam.

Rice. 3. Fillet coupling:

1 - pipeline; 2 - clutch

Cracks along the pipe body with a length of less than 50 mm are eliminated by applying a patch or installing a clamp.

Cracks along the pipe body with a length of more than 50 mm, ruptures and corrosion-damaged sections of the pipeline over a length greater than the diameter of the pipe must be repaired by replacing the defective section of the pipeline with a new one (Fig. 4).

Rice. 4. Elimination of a rupture (crack) of the pipeline by inserting a coil (example):

I - pipe torn along the welded joint; II - cutting of an emergency joint and the introduction of clay plugs; III - fitting a new branch pipe (coil) and welding it into the pipeline;

1 - broken joint; 2 - branch pipe (coil); 3 - clay swabs; 4 - pipeline after the liquidation of the accident

Gas pipelines:

Fistulas formed in the gas pipeline are eliminated by welding, for which the edges of the fistula are carefully prepared for welding.

If cracks appear on the gas pipeline in welded joints or along the whole metal, then the defective sections are removed, and branch pipes are welded in their place.

Accidents that occurred as a result of jamming of devices passed inside the pipeline, are eliminated after determining the location of these devices and plugs by replacing the pipeline section.

Accidents at linear fittings are eliminated:

in stuffing boxes (adding packing of stuffing boxes) without stopping pumping with the help of special devices;

in flange connections (between the cover and the body, on bypasses) - with pumping stop, replacement of gaskets;

in case of depressurization of the valve body or loss of operability of the locking device - by cutting out the entire valve and replacing it with a new one.

In case of accidents on the connecting elements of the pipeline(tees, adapters, bends) restoration should be carried out by replacing the defective part with the corresponding new one in terms of parameters.

Preparatory activities

Emergency recovery work must be ensured by the implementation of preparatory measures:

clarification of the place of the accident and the detention of the product;

delivery of repair facilities and personnel to the accident site;

preparation of the repair site;

organization of drainage and drainage;

ensuring the safety of neighboring communications and objects of the national economy.

Localization and collection of spilled pumped oil

Upon receipt of a signal about an accident, the dispatcher must take all measures to reduce the volume of the resulting product:

stopping pumping through the damaged section of the pipeline;

determining the location of the accident;

overlap of linear valves that cut off the damaged section of the pipeline.

Excavation

Earthworks during the liquidation of an accident on the pipeline include:

arrangement of an earthen barn, construction of dams or embankments for collecting and trapping the product, trenches for diverting the pumped product;

preparation of a site for the production of ATS, auxiliary sites, arrangement of driveways, crossings, etc.;

creation of a repair pit and its backfilling.

Sealing the internal cavity of the pipeline

In order to prevent ignition of the pumped product and gases coming from the pipeline, as well as to prevent gas contamination of the place of production of AVR, it is necessary to reliably seal the internal cavity of the pipeline - isolate it with special means from the external environment for the entire period of welding and installation work.

Sealing is carried out using tampons or mechanical blocking devices. As materials for creating tampons, clay and quick-setting composite materials can be used, created from such common reinforcing materials as fiberglass and fiberglass, which have high mechanical strength, corrosion resistance, low density (1.6 - 1.8 g/cm3), etc. .d.

Welding and installation works

When preparing and performing welding and installation work, it is necessary to be guided by the requirements of VSN 006-89 (Construction of main and field pipelines. Welding.) and SNiP III-42-80 (Main pipelines. Rules for the production and acceptance of work.).

Weld control

The quality control of welding and installation works during the repair of pipelines is organized by the responsible work manager and is carried out:

step-by-step control carried out in the process of assembly and welding of joints;

visual inspection and measurement of the geometric parameters of welds;

checking the continuity of the deposited metal by non-destructive control methods.

Based on the results of the control, the quality of work is assessed and a conclusion is made on the readiness of the pipeline for launch.

Pipeline insulation

For anti-corrosion protection of the repaired section of the pipeline, reinforced insulation should be used.

Insulation for the repaired area should be applied to the cleaned surface of the pipeline. Cleaning is done in two steps:

preliminary - after opening the pipeline and creating a repair pit;

final - after completion of welding and installation work.

Elimination of consequences of accidents

After the restoration of the damaged section of the pipeline, the pumped oil product from the storage pits (earth pit, embankment or other containers) must be pumped into the repaired or other parallel pipeline by mobile pumping units PNA-1, PNA-2 or other high-pressure units, or transported in special containers to the nearest transfer station.

Elimination of the consequences of the ingress of the pumped oil product into water bodies should include water purification to the maximum permissible concentrations (MPC) of oil products in water.

Cleaning the surface of the swamp from the remnants of the oil product can be carried out by washing it off the surface of the swamp or burning it.

After the completion of emergency recovery work, the reclamation of lands damaged as a result of the accident should be carried out in accordance with RD 39-0147103-365-86 (Instruction for the reclamation of lands contaminated with oil).

Other jobs

A number of special requirements and operations should be carried out in case of accidents caused by natural phenomena in the mountains (landslides, erosion, earthquakes), as well as in case of accidents in desert areas, rocky soils and at road and railway crossings.