Filling the annular space. Methods and technologies for cementing wells: how to prepare and fill grouting slurry

The invention relates to the construction of pipelines. The method is designed to eliminate temperature stresses in pipe-in-pipe pipelines in the hermetically sealed working state of the inner pipeline (in the absence of excess pressure in the annular space) without installing special expansion joints inside. The method consists in placing in the annular space of the sealing units made in the form of tightly wound spiral sleeves to each other. The sleeves are made of elastic material, impermeable to air; they are wound with a small gap at the ends of a pipe-in-pipe pipeline onto an internal pipeline in the form of two spirals, each with a length not less than the internal diameter of the pipeline. Coils are brought into the annular space, the sleeves are filled with air, the ends of the annular space are closed with annular plugs rigidly connected to the outer pipeline, which provide free movement of the outer and inner pipelines relative to each other in the absence of excess pressure in the annular space. The technical result of the invention is to improve the reliability of protection environment... 2 c.p. f-ly.

The invention relates to the construction of pipelines, mainly underwater crossings, and is intended to eliminate temperature stresses in pipelines of the "pipe-in-pipe" type in working condition without installing special expansion joints inside and to prevent the ingress of liquid hydrocarbons pumped through the internal pipeline into the environment in case of leakage of the internal pipeline ...

It is known to construct pipe-in-pipe pipelines, in which the annular space is sealed by filling spiral hoses loosely wound towards each other along the entire length of the inner pipeline with hardening cement mortar. Temperature stresses in the internal pipeline are extinguished by arranging special compensators in the form of closed metal cavities spirally wound towards each other (AS USSR No. 1460512, class F16L 1/04, 1989).

The disadvantage of sealing the annular space in this case is the mandatory installation of temperature stress compensators inside the pipe-in-pipe pipeline, which significantly complicates and increases the cost of the entire known pipe-in-pipe pipeline design.

Essentially the closest technical solution is to seal the cavity of the pipelines, in which the seals are made in the form of tightly wound spiral sleeves, the sleeves are filled with incompressible fillers (RF patent, No. 2025634, CL F16L 55/12, 1994).

In this case, complete sealing of the space is not ensured with a sufficiently large excess pressure in front of the seal. This pressure can be in front of the sleeve seal if it is installed in the annular space. In the event of damage (leakage) of the internal piping of the pipe-in-pipe system, polluting liquid can seep through spiral gaps between tightly wound non-deformable under pressure hoses with an incompressible filler round in cross-section and enter the environment. Such sealing of the pipeline cavity has a limited area of ​​application and can only be used at a pressure in front of the sleeve seal close to atmospheric, i.e. only when holding renovation works elimination (cutting) of damaged sections of conventional (not "pipe in pipe") pipelines.

The purpose of the invention is reliable protection of the environment from liquid hydrocarbon spills in case of leakage of the internal pipeline of the pipe-in-pipe system and ensuring compensation of temperature stresses in the internal pipeline in working condition (without breaking its tightness) due to free axial movement of the internal pipeline relative to the external one in good condition of the pipe-in-pipe system pipe ".

Reliable protection of the environment is achieved due to the fact that the sealing of the annular space is performed by installing tightly wound spiral-shaped sleeves made of an elastic air-tight material into the annular space, which are filled with a compressible filler (air). If the tightness of the inner pipeline is broken, the excess pressure in the annular space rises, squeezes and tightly presses the spirally wound sleeves with air to the walls of the outer and inner pipelines, thus ensuring complete tightness of the annular space.

Provision of compensation of temperature stresses of the inner pipeline in working condition (in the absence of excessive pressure in the annular space) is achieved due to the fact that air is supplied to the spiral wound sleeves at low pressure, close to atmospheric, at which there are practically no friction forces between the sleeves and the walls of the inner pipeline preventing the relative longitudinal movement of the external and internal pipelines in good condition.

The method is implemented as follows. The sleeves are made of elastic material, impermeable to air, they are wound with a small gap at the ends of the pipe-in-pipe pipeline onto the inner pipeline in the form of two spirals each with a length of at least the inner diameter of the pipeline, spirals are inserted into the annular space, the sleeves are filled with air, the ends of the annular space closed with annular plugs rigidly connected to the external pipeline, providing free movement of the external and internal pipelines relative to each other in the absence of excess pressure in the annular space. To eliminate temperature stresses in a pipe-in-pipe pipeline, impermeable sleeves wound in a tight spiral onto the inner pipeline are filled with air at a pressure that ensures free movement of the pipelines relative to each other in the absence of excess pressure in the annular space.

To exclude spontaneous unwinding of the spirals when they are inserted into the annular space, the ends of the spirals are connected with a flexible connection or their ends are limited by annular bushings.

CLAIM

1. A method of sealing the annular space of pipelines of the "pipe-in-pipe" type, including the placement in pipelines of sealing units made in the form of tightly wound spiral sleeves with fillers, characterized in that the sleeves are made of an elastic material impermeable to air, they are wound with with a small gap at the ends of the pipe-in-pipe type pipeline to the internal pipeline in the form of two spirals each with a length of at least the internal diameter of the pipeline, spirals are inserted into the annular space, the hoses are filled with air, the ends of the annular space are closed with annular plugs rigidly connected to the external pipeline, providing free movement of the external and internal pipelines relative to each other in the absence of excess pressure in the annular space.

2. The method according to claim 1, characterized in that in order to eliminate temperature stresses in a pipe-in-pipe pipeline, impermeable sleeves wound in the form of dense spirals on the inner pipeline are filled with air at a pressure that ensures free movement of the pipelines relative to each other in the absence of excess pressure in the annular space.

3. The method according to claim 1, characterized in that in order to prevent spontaneous unwinding of the spirals when they are inserted into the annular space, the ends of the spirals are connected by a flexible connection or their ends are limited by annular bushings.

Transport vehicle for the delivery of the winder and accessories

Coiling machine (transportation by truck)

Hydraulic unit for coiling machine (transport by truck)

Generator (transport by truck)

Wheel forklift

Tool:

Bulgarian

Chisel, chisel, chisel

Backing material (branded Blitzd? Mmer® product)

Thinner (eluent) and pore-forming additive

2. Preparation of the construction site

Site preparation implies safety measures road traffic, provision of sites for machine tools and a warehouse for equipment and materials, as well as a supply of water and electricity.

Flow regulation

During the winding process, depending on specific situation you can refuse to take safety measures in case of filling the sanitized collector with water up to 40%.

A small flow can be used later for better movement of the pipe during coiling and for fixing the pipe during backfilling.

Collector cleaning

Cleaning the manifold using the winding method is usually done by high pressure flushing.

TO preparatory work Relining also includes the removal of obstacles such as hardened deposits, inserts of other communications, sand, etc. Their elimination is carried out, if necessary, manually using a cutter, a sledgehammer and a chisel.

Inserts of other communications

The branches of the channels flowing into the collector to be refurbished must be plugged before starting the restoration work.

Quality control and quantity of materials and equipment

Upon delivery of the necessary materials and equipment to the construction site, their completeness and quality are checked. In this case, for example, the profile is checked for compliance with the data according to the quality certificate for its marking, sufficient length, as well as possible damage caused by transportation; Blitzd? mmer® proprietary backing material is in turn checked for sufficient quantity and proper storage conditions.

Before installing the coiling machine, it may be necessary to partially or completely remove the base of the chamber to ensure alignment between the machine and the collector to be refurbished. Removal is carried out, as a rule, by opening the base of the camera with a perforator or manually using a sledgehammer and chisel.

Pipe winding can be carried out both upstream and upstream, depending on the size of the well chamber and the possibilities of access to it.

In our case, the winding of the pipe is carried out against the flow, since the chamber of the well at the lowest point is large, which greatly facilitates the installation of the winding machine.

3. Installation of the coiling machine

Delivery of the coiling machine

The hydraulically driven coiling machine used in our example is designed for lining pipelines with diameters from DN 500 to DN 1500. Coiling boxes of different diameters are used depending on the diameter of the pipeline into which the new pipe is wound.

First, the coiling machine, disassembled into its component parts, is delivered to the starting well. It consists of a tape drive mechanism and a winding box.

Lowering machine parts into the shaft and installing the coiling machine

The component parts of the winding box are lowered manually into the starting shaft and mounted there.

For diameters up to 400 DN, the machine can be lowered into the shaft fully assembled.

Before lowering the hydraulically driven tape drive into the starter shaft, remove the transport legs of the tape drive.

The hydraulically driven belt conveyor is mounted on the winding box directly in the starting shaft. In this case, the receiving part of the coiling machine must be below the level of the neck of the well to ensure the unhindered supply of the profile to the tape drive mechanism.

Installation work is completed by connecting the hydraulic drive of the winding machine to the hydraulic unit located near the starting shaft.

Then it is necessary to check the alignment of the coiling machine and the collector to be refurbished, otherwise, during the winding process, the coiled pipe may get stuck against the collector walls or experience strong resistance from them, which can negatively affect the length of the refurbished section.

4. Preparing the profile

Unwinding and cutting a profile

In order for the first turn of the coiled pipe to be under the right angle to the pipe axis, it is necessary to cut the profile using a "grinder" in accordance with the pipe diameter. To do this, it is necessary to unwind part of the profile from the spool located on the bed.

Profile feed

The cut profile is fed by means of a guide roller, fixed on the arm of the manipulator or other device, into the starting shaft.

First round

The profile is fed into the tape drive mechanism, passes along the inner side of the winding box (make sure that the profile falls into the grooves on the rollers; if necessary, correct the profile manually) and then is connected to each other using the so-called latch lock (loss in diameter due to thickness profile about 1-2 cm).

Profile in stock

Diameter range from DN 200 to DN 1500.

5. Winding process

A small flow raises the coiled pipe and reduces friction against the lower part of the collector to be refurbished.

The profile forming the pipe is progressively fed from the winding box with rotational movements in the direction of the collector to be sanitized. In this case, it is necessary to ensure that the winding pipe does not undergo strong friction against the walls of the old channel and does not cling to joints, tie-ins, etc.

Glue feed.

Long-term waterproofness of the coiled pipe is achieved by feeding a special PVC glue into the latches of the individual turns of the profile.

Locking technology.

The glue is fed into the groove on one side of the profile, after which the lock is immediately snapped into place on the other side of the profile and thus there is a reliable adhesion of both parts of the latch lock. This view the connection is also called the "cold welding" method.

6. Backfilling / Overlap of the annular space with mortar

Dismantling the machine and adjusting the pipe.

According to the footage marked on the back of the profile, the length of the wound pipe can be calculated. After winding the pipe of the required length, check whether the distance from the end of the pipe to the receiving well coincides with the length of the pipe protruding from the starting well.

If they match, then the wound pipe is cut off in the starting well using a grinder.

The coiled pipe, supported by the flow in the collector, is easily pushed by two workers from the starting well towards the receiving well, so that the edges of the pipe exactly coincide with the edges of both wells.

These actions allow you to save material, as the length of the wound pipe exactly corresponds to the length of the collector to be rehabilitated, taking into account the part of the pipe protruding into the starting well and later pushed into the collector.

Then the coiling machine is again dismantled into separate parts and removed from the starting well.

Overlap of the annular space

The overlap of the annular space between the old pipe and the coiled pipe is achieved by internally cementing a space of about 20 cm from the edge of the well with sulphate-containing cement mortar. Depending on the level groundwater and the diameter of the pipe, there may be a need for a larger number of pipes for filling the solution and releasing air.

Overlap of the annular space at the highest point.

First, the annular space is overlapped at the highest point (in this case, it is a receiving well). After plugging the annular space and inserting air outlet pipes into the base and the top of the cement floor, the waste flow is temporarily blocked (flow control), so that work in the well chamber can be carried out without any influence from the waste water. Waste water, which is still in the annular space, flows down towards the lowest point, thus, the annular space is emptied and ready for grouting. After completion of the work to shut off the annular space, waste water is let through the wound pipe of the sanitized collector.

Raising the water level in the coiled pipe.

During this process the waste flow is also regulated, during which the coiled pipe is closed by means of a so-called bubble with a through profiled pipe and a pipe for adjusting the water level in the coiled pipe. Thus, the water level in the coiled pipe is raised and the pipe is fixed to the bottom of the old channel during the process of two-phase filling of the annular space. This ensures that the angle of inclination is maintained and the possibility of bending is eliminated.

Overlap of the annular space at the lowest point

Then, the annular space is overlapped at the lowest point (in our case, this is the starting well).

If necessary, pipes for pouring the solution are mounted in the ceiling vault, and branch pipes for venting air into the ceiling and base of the ceiling. The pipe integrated into the bubble has a profiled outer coating and does not provide complete tightness, which allows a certain amount of waste water to flow out. With the help of a water level detection pipe, it is always possible to monitor the wastewater level in the coiled pipe.
The first stage of backfilling.

In our case, backfilling of the annular space is carried out from the lowest point in two stages. To do this, a tank is installed at the edge of the well for kneading the backing material, to which a hose for supplying the solution is connected. Mixing of Blitzd? Mmer branded backing material is carried out according to the manufacturer's recommendations in special tanks of various volumes.

Next, the valve of the mixer tank is opened, and the Blitzd? Mmer solution, without external pressure, is freely poured into the annular space between the old channel and the new wound pipe. Waste water filling the coiled pipe prevents it from floating up.

The process of mixing and supplying the solution continues until the solution begins to flow out of the air exhaust pipe installed in the floor sole at the lowest point.

By comparing the amount of used back-filling solution with the calculated amount, it is possible to check whether the solution remains in the annular space or goes into the ground through the fistulas in the old channel. If the consumed amount of the solution coincides with the calculated one, the backfilling process continues until the solution begins to flow out of the air outlet pipe mounted in the ceiling at the lowest point. The first stage of backfilling is considered complete.

The second stage of backfilling.

The hardening of the backing material lasts 4 hours, while there is a slight sediment of the solution in the annular space. After the mortar has hardened, mixing of the Blitzd? Mmer backfilling material begins for the second backfilling phase. The process of filling the intertubular space can be considered complete when the solution begins to flow out of the air exhaust pipe installed in the ceiling roof at the highest point.

For quality control, a sample is taken of the backfill solution flowing from the air outlet in the receiving well.

Then, the pipes for filling the solution and the air outlet pipes in the starting and receiving wells are dismantled. Through holes in the slabs are cemented.

7. Final work

Restoration of the sole.

The partially cracked bottom of the well chamber is being repaired.

The integration of the tie-ins into the new channel is carried out by a robot.

Quality control

To control the quality of the renovation work, an inspection of the pipeline itself is carried out, as well as a tightness test in accordance with DIN EN 1610.

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Bortsov Alexander Konstantinovich. Construction technology and methods for calculating the stress state of underwater pipe-in-pipe pipelines: silt RSL OD 61: 85-5 / 1785

Introduction

1. Construction of a subsea pipe-in-pipe pipeline with an annular space filled with cement stone 7

1.1. Two-pipe piping structures 7

1.2. Feasibility study of the underwater crossing of the pipe-to-pipe pipeline 17

1.3. Analysis of the work performed and formulation of research tasks 22

2. The technology of cementing the annular space of pipelines "pipe in pipe" 25

2.1. Materials for cementing the annular space 25

2.2. Selection of cement slurry formulation 26

2.3. Cementing equipment 29

2.4. Filling the annular space 30

2.5. Calculation of cementing 32

2.6. Experimental verification of cementing technology 36

2.6.1. installation and testing of a two-pipe horse rubbing 36

2.6.2. Cementing the annular space 40

2.6.3. Strength tests of the pipeline 45

3. Stress-strain state of three-layer pipes under the action of internal pressure 50

3.1. Strength and deformation properties of cement stone 50

3.2. Stresses in three-layer pipes when the cement stone perceives tangential tensile forces 51

4. Experimental studies of the stress-strain state of three-layer pipes 66

4.1. Experimental research methodology 66

4.2. Model manufacturing technology 68

4.3. Test bench 71

4.4. Method for measuring strains and testing 75

4.5. Influence of overpressure of cementing the mec-pipe space on the redistribution of stresses 79

4.6. Checking the adequacy of theoretical relationships 85

4.6.1. Experiment Planning Technique 85

4.6.2. Statistical processing of test results! ... 87

4.7. Testing of natural three-layer pipes 93

5. Theoretical and experimental studies of the bending stiffness of pipe-in-pipe pipelines 100

5.1. Calculation of the bending stiffness of pipelines 100

5.2. Experimental studies of bending stiffness 108

Conclusions 113

General conclusions 114

Literature 116

Appendices 126

Introduction to work

In accordance with the decisions of the XXII Congress of the CPSU in the current five-year period, the oil and gas industries are developing at an increased rate, especially in the regions of Western Siberia, in the Kazakh SSR and in the north of the European part of the country.

By the end of the five-year plan, oil and gas production will amount to 620-645 million tons and 600-640 billion cubic meters, respectively. meters.

For their transportation, it is necessary to carry out the construction of powerful main pipelines with high degree automation and operational reliability.

One of the main tasks in the KP five-year plan will be the further accelerated development of oil and gas fields, the construction of new and capacity building of the existing gas and oil transportation systems going from the regions of Western Siberia to the main places of consumption of oil and gas - to the Central and Western regions of the country. Long-distance pipelines on their way will cross a large number of different water barriers. Crossings over water barriers are the most difficult and critical sections of the linear part of the main pipelines, on which the reliability of their operation depends. If the underwater crossings fail, huge material damage is inflicted, which is defined as the amount of damage to the consumer, the transport company and from environmental pollution.

Repair and restoration of underwater crossings are challenging task requiring significant forces and resources. Sometimes the cost of repairing a crossing exceeds the cost of building it.

Therefore, ensuring high reliability transitions are given a lot of attention. They must work without failures and repairs during the entire design life of the pipelines.

At present, to improve reliability, crossings of main pipelines through water barriers are constructed in two-line design, i.e. parallel to the main line, at a distance of up to 50 m from it, an additional - reserve line is laid. Such redundancy requires double capital investment, but, as operating experience shows, it does not always provide the required operational reliability.

Recently, new design schemes have been developed that provide increased reliability and strength of single-strand transitions.

One of such solutions is the construction of a pipe-in-pipe underwater pipeline crossing with an annular space filled with cement stone. A number of pipe-in-pipe crossings have already been built in the USSR. Successful experience in the design and construction of such crossings indicates that the smoldering theoretical and constructive solutions for the technology of installation and laying, quality control of welded joints, testing of two-pipe pipelines are sufficiently developed. But, since the annular space of the constructed crossings was filled with liquid or gas, the issues related to the peculiarities of the construction of underwater crossings of pipe-in-tube pipelines with the annular space filled with cement stone are essentially new and poorly studied.

Therefore, the purpose of this work is to scientifically substantiate and develop a technology for the construction of underwater pipe-in-pipe pipelines with an annular space filled with cement stone.

To achieve this goal, a large program was carried out

theoretical and experimental research. Shown the possibility of using for filling the annular space under-

water pipelines "pipe in pipe" materials, equipment and technological methods used in cementing wells. An experimental section of this type of pipeline has been built. Formulas are derived for calculating stresses in three-layer pipes under the action of internal pressure. Experimental studies of the stress-strain state of three-layer pipes for main pipelines have been carried out. A formula is derived for calculating the bending stiffness of three-layer pipes. The bending stiffness of the pipe-in-pipe pipeline was determined experimentally.

On the basis of the performed studies, "Temporary instructions for the design and construction technology of pilot-industrial underwater gas pipelines with pressures of 10 MPa or more of the" pipe-in-pipe "type with cementing of the annular space" and "Instructions for the design and construction of offshore subsea pipelines according to the structural scheme" were developed. pipe-in-pipe "with cementing of the annular space", approved by Mingazprom in 1982 and 1984

The results of the dissertation were practically used in the design of the underwater crossing of the Urengoy - Uzhgorod gas pipeline across the Pravaya Khetta river, the design and construction of oil product pipelines Dragobych - Stryi and Kremenchug - Lubny - Kiev, the offshore pipelines Strelka 5 - Bereg and Golitsyno-Bereg.

The author thanks the head of the Moscow underground gas storage station of the production association "Mostransgaz" OM, Korabelnikov, head of the laboratory of strength of gas pipelines at VNIIGAZ, Cand. tech. Sciences N.I. Anenkov, head of the well casing detachment of the Moscow Region Deep Drilling Expedition O.G. Drogalin for help in organizing and conducting experimental research.

Feasibility study of the underwater crossing of the pipe-to-pipe pipeline

Crossing of the pipeline "pipe in pipe" Crossings of main pipelines through water barriers are among the most critical and difficult sections of the route. Failures of such transitions can cause a sharp decrease in productivity or a complete stop of the pumping of the transported product. Repair and rehabilitation of subsea pipelines is complex and costly. Often, the costs of repairing a crossing are commensurate with the costs of building a new crossing.

Underwater crossings of main pipelines in accordance with the requirements of SNiP 11-45-75 [70] are laid in two lines at a distance of at least 50 m from one another. With such redundancy, the probability of failure-free operation of the transition as a transport system as a whole increases. The cost of building a backup line usually matches or even exceeds the cost of building a main line. Therefore, it can be considered that increasing reliability through redundancy requires doubling the capital investment. Meanwhile, operating experience shows that this method of increasing operational reliability does not always give positive results.

The results of studying the deformations of channel processes have shown that the deformation zones of the channels significantly exceed the distances between the threads of the transitions being laid. Therefore, the erosion of the main and reserve lines occurs almost simultaneously. Consequently, an increase in the reliability of underwater crossings should be carried out in the direction of careful consideration of the hydrology of the reservoir and the development of structures of crossings with increased reliability, in which an event leading to a breach of the pipeline tightness was taken for the failure of an underwater crossing. In the analysis, the following design solutions were considered: two-strand one-pipe structure - pipelines are laid in parallel at a distance of 20-50 m from one another; solid subsea pipeline concrete pavement; pipeline construction "pipe in pipe" without filling the annular space and with filling with cement stone; crossing constructed by directional drilling.

From the graphs shown in Fig. 1.10, it follows that the highest expected probability of failure-free operation is at the underwater crossing of a pipe-in-pipe pipeline with the annular space filled with cement stone, with the exception of the crossing constructed by the directional drilling method.

Experimental studies of this method and the development of its main technological solutions are currently being carried out. Due to the complexity of creating drilling rigs for directional drilling, it is difficult to expect in the near future the widespread introduction of this method into the practice of pipeline construction. Besides, this method can be used in the construction of crossings of only a short length.

For the construction of crossings according to the "pipe-in-pipe" design with the annular space filled with cement stone, it is not required to develop new machines and mechanisms. When installing and laying two-pipe pipelines, the same machines and mechanisms are used as in the construction of one-pipe pipelines, and for the preparation of cement slurry and filling the slurry of the annular space, cementing equipment is used "used for casing oil and gas wells. Currently, in the system of Shngazprom and Minnefteprom several thousand cementing units and cement mixing machines are in operation.

Main technical and economic indicators of underwater pipeline crossings various designs are given in Table 1,1, Calculations were performed for the underwater passage of the experimental section of the gas pipeline at a pressure of 10 MPa, excluding the cost of valves. The length of the crossing is 370 m, the distance between parallel lines is 50 m. The pipes are made of steel X70 with a yield point (fl - 470 MPa and a tensile strength of Є6р = 600 MPa. The thickness of the pipe walls and the necessary additional ballasting for options I, P and Ш are calculated according to SNiP 11-45-75 [70]. The thickness of the casing wall in option III is determined for the pipeline of the third category. Hoop stresses in the pipe walls from the working pressure for these options are calculated using the formula for thin-walled pipes.

In a pipe-in-pipe pipeline structure with an annular space filled with cement stone, the wall thickness inner pipe determined by the method described in [e], the thickness of the outer wall is taken as 0.75 of the thickness of the inner one. Hoop stresses in pipes are calculated according to formulas 3.21 of this work, the physical and mechanical characteristics of cement stone and pipe metal are taken the same as when calculating table. 3.1. The most common two-strand one-pipe transition design with ballasting with cast-iron weights was taken as the standard of comparison ($ 100). As you can see from the table. І.І, metal consumption of the pipe-in-pipe pipeline structure with the annular space filled with cement stone for steel and cast iron is more than 4 times

Cementing equipment

Specific features of the production of works on cementing the annular space of pipelines "pipe in pipe" determine the requirements for the cementing equipment. The construction of crossings of main pipelines through water barriers is carried out in various regions of the country, including remote and inaccessible ones. Distances between construction sites reach hundreds of kilometers, often in the absence of reliable transport communications. Therefore, cementing equipment must be highly mobile and convenient for transportation over long distances in off-road conditions.

The amount of cement slurry required to fill the annular space can reach hundreds of cubic meters, and the pressure when pumping the slurry can reach several megapascals. Consequently, the cementing equipment must have high productivity and power to ensure the preparation and pumping into the annular space of the required amount of solution for a time not exceeding the time of its thickening. At the same time, the equipment must be reliable in operation and have a sufficiently high efficiency.

The set of equipment designed for cementing wells meets the specified conditions most fully [72]. The complex includes: cementing units, cement mixing machines, cement trucks and tank trucks, a station for monitoring and control of the cementing process, as well as auxiliary equipment and warehouses.

Mixing machines are used to prepare the solution. The main units of such a machine are a hopper, two horizontal unloading augers and one inclined loading auger and a vacuum-hydraulic mixing device. The bunker is usually installed on the chassis of an off-road vehicle. The augers are driven by the vehicle's traction motor.

The solution is pumped into the annular space by a cementing unit mounted on. the chassis of a powerful truck. The unit consists of a cementing pump high pressure for pumping a solution, a pump for supplying water and an engine to it, measuring tanks, a pump manifold and a collapsible metal pipe.

Control of the cementing process is carried out using the SKTs-2m station, which allows you to control the pressure, flow rate, volume and density of the injected solution.

With small volumes of the annular space (up to several tens of cubic meters) for cementing, you can also use mortar pumps and mortar mixers used for the preparation and pumping of mortars.

Cementing of the annular space of underwater pipe-in-pipe pipelines can be carried out both after they have been laid in an underwater trench, and before laying - on the shore. The choice of the cementing site depends on the specific topographic conditions of the construction, the length and diameter of the crossing, and the availability of special equipment for cementing and laying the pipeline. But it is preferable to cement pipelines laid in an underwater trench.

Cementing of the annular space of pipelines passing in the floodplain (on the shore) is carried out after laying them in a trench, but before backfilling with soil. If additional ballasting is required, the annular space can be filled with water before cementing. The solution is fed into the inter-pipe space from the lowest point of the pipeline section. The outlet of air or water is carried out through special branch pipes with valves installed on the external pipeline at its upper points.

After complete filling of the annular space and the beginning of the solution outlet, the rate of its supply is reduced and the injection is continued until the solution with a density equal to the density of the injected begins to emerge from the outlet pipes. Previously, back pressure is created in the internal pipeline, which prevents the loss of stability of its walls. Upon reaching the required excess pressure in the annular space, close the valve on the inlet pipe. The tightness of the annular space and the pressure in the internal pipeline are maintained for the time required for the cement slurry to harden.

When filling, the following methods of cementing the annular space of pipelines can be used: straight; with the help of special cementing pipelines; sectional. cement mortar, which displaces the air or water in it. The supply of the solution and the outlet of air or water are carried out through branch pipes with valves mounted on the external pipeline. The entire section of the pipeline is filled in one step.

Cementing with the help of special cementing pipelines With this method, small-diameter pipelines are installed into the annular space, through which cement slurry is fed into it. Cementing is carried out after the two-pipe pipeline has been laid in an underwater trench. The cement slurry is fed through the cementing pipelines to the lower point of the laid pipeline. This method of cementing allows for the highest quality filling of the annular space of the pipeline laid in an underwater trench.

Sectional cementing can be used in the event of a lack of cementing equipment or high hydraulic resistances when pumping a solution, which does not allow cementing the entire section of the pipeline at one time. In this case, the cementing of the annular space is carried out in separate sections. The length of the cementing sections depends on technical characteristics cementing equipment. For each section of the pipeline, separate groups of nozzles are installed for pumping the cement slurry and releasing air or water.

To fill the annular space of pipe-in-pipe pipelines with cement mortar, it is necessary to know the amount of materials and equipment required for cementing, as well as the time of its carrying out.

Stresses in three-layer pipes during the perception of tangential tensile forces by a cement stone

The stressed state of a three-layer pipe with an annular space filled with cement stone (concrete) under the action of internal pressure was considered in their works by P.P. Borodavkin [9], A.I. Alekseev [5], R.A. of the formulas, the authors accepted the hypothesis that the cement stone ring perceives tensile tangential forces and does not crack under loading. Cement stone was considered as an isotropic material having the same moduli of elasticity under tension and compression, and, accordingly, the stresses in the cement stone ring were determined by Lamé's formulas.

Analysis of the strength and deformation properties of the cement stone showed that its tensile and compressive moduli are not equal, and the tensile strength is much lower than the compressive strength.

Therefore, in the dissertation work, a mathematical formulation of the problem is given for a three-layer pipe with an annular space filled with a multi-modular material, and an analysis of the stress state in three-layer pipes of main pipelines under the action of internal pressure is carried out.

When determining the stresses in a three-layer pipe from the action of internal pressure, we consider a ring of unit length cut from a three-layer pipe. The stress state in it corresponds to the stress state in the pipe, when (En = 0. The tangential stresses between the surfaces of the cement stone and pipes are taken equal to zero since the adhesion forces between them are negligible. We consider the inner and outer pipes as thin-walled. A ring made of cement stone in the annular space is considered to be thick-walled, made of a material of different modulus.

Let the three-layer pipe be under the action of the internal pressure PQ (Fig. 3.1), then the internal pressure P and the external P-g act on the internal pipe, caused by the reshuffle of the external pipe and cement stone to the movement of the internal one.

On the outer tube the internal pressure Pg acts due to the deformation of the cement stone. The cement stone ring is under the influence internal R-g and external 2 pressures.

Tangential stresses in the inner and outer pipes under the action of the pressures PQ, Pj and Pg are determined: where Ri, & i, l 2, 6Z are the radii and wall thicknesses of the inner and outer pipes. Tangential and radial stresses in a cement stone ring are determined by the formulas obtained for solving the axisymmetric problem of a hollow cylinder made of a multi-modulus material under the action of internal and external pressures ["6]: cement stone under tension and compression. In the above formulas (3.1) and (3.2) unknown values ​​of pressure Pj and P2. We find them from the conditions of equality of radial displacements of the surfaces of interfaces of the cement stone with the surfaces of the inner and outer pipes. The dependence of relative tangential deformations on radial displacements (and) has the form [53] Dependence of relative deformations from stresses for pipes G 53] is determined by the formula

Test bench

Alignment of pipes (Fig. 4.2) inner I and outer 2 and sealing of the annular space were performed using two centering rings 3 welded between the pipes. In the outer pipe vva-. Two chokes 9 were installed - one for pumping cement slurry into the annular space, the other for air outlet.

The annular space of models with a volume of 2G = 18.7 liters. filled with a solution prepared from backfill Portland cement for "cold" wells of the Zdolbunovsky plant, with a water-cement ratio W / C = 0.40, density p = 1.93 t / m3, spreading along the AzNII cone at = 16.5 cm, the beginning of setting t = 6 hours 10 clays, the end of setting t „_ = 8 hours 50 minutes", the ultimate strength of two-day samples of cement stone for bending & pcs = 3.1 Sha. These characteristics were determined according to the method of standard tests for oil well Portland cement for "cold" wells (_31j.

Compression and tensile strengths of cement stone samples by the beginning of testing (30 days after filling the inter-tube space with cement mortar) b = 38.5 MPa, b c = 2.85 Sha, modulus of elasticity in compression EH = 0.137 TO5 Sha, Poisson's ratio ft = 0.28. Compression testing of cement stone was carried out on cubic specimens with ribs of 2 cm; in tension - on specimens in the form of eights with a cross-sectional area in the constriction of 5 cm [31]. For each test, 5 samples were made. The samples were solidified in a chamber with 100% relative humidity. To determine the modulus of elasticity of cement stone and Poisson's ratio, the method proposed by millet was used. K.V. Ruppenyt [_ 59 J. The tests were carried out on cylindrical specimens with a diameter of 90 mm and a length of 135 mm.

The solution was fed into the annulus of the models using a specially designed and manufactured installation, the diagram of which is shown in Fig. 4.3.

Cement slurry was poured into the container 8 with the cover 7 removed, then the cover was installed in place and the solution was forced out with compressed air into the intertubular space of model II.

After complete filling of the annular space, valve 13 at the outlet of the sample was closed and an excess cementing pressure was created in the annular space, which was monitored with a pressure gauge 12. When the design pressure was reached, valve 10 at the inlet was closed, then the excess pressure was released and the model was disconnected from the installation. During the hardening of the mortar, the model was in an upright position.

Hydraulic tests of models of three-layer pipes were carried out on a stand designed and manufactured at the Department of Metal Technology of the Ministry of National Economy and the State Enterprise named after V.I. I.M.іubkin. The stand layout is shown in Fig. 4.4, general form- in fig. 4.5.

The model pipe II was placed into the test chamber 7 through the side cover 10. The model installed with a slight slope was filled with oil from the tank 13 by a centrifugal pump 12, while valves 5 and 6 were open. After filling the model with oil, these valves were closed, valve 4 was opened, and high pressure pump I was turned on. The excess pressure was released by opening valve 6. The pressure was monitored with two exemplary pressure gauges 2 designed for 39.24 Mia (400 kgf / sg). Multicore cables 9 were used to display information from the sensors installed on the model.

The stand made it possible to carry out experiments at pressures up to 38 MPa. The high-pressure pump VD-400 / 0.5 E had a small flow - 0.5 l / h, which made it possible to carry out smooth loading of the samples.

The cavity of the inner pipe of the model was sealed with a special sealing device that excludes the influence of axial tensile forces on the model (Fig. 4.2).

The tensile axial forces arising from the action of pressure on the pistons 6 are almost completely absorbed by the rod 10. As the strain gages have shown, a small transfer of tensile forces (about 10%) occurs due to friction between the rubber sealing rings 4 and the inner tube 2.

When testing models with different inner diameters of the inner tube, pistons of different diameters were also used. different methods and funds

where ς is a coefficient that takes into account the distribution of the load and the support reaction of the base, ς = 1.3; P pr is the calculated external reduced load, N / m, determined, respectively, by the formulas above, for different options backfilling, as well as the absence or presence of water in the polyethylene pipeline; R l is a parameter characterizing the rigidity of the pipeline, N / m 2:

where k e is a coefficient that takes into account the effect of temperature on the deformation properties of the pipeline material, k e = 0.8; E 0 - modulus of creep of the pipe material under tension, MPa (during operation for 50 years and stress in the pipe wall of 5 MPa E 0 = 100 MPa); θ is a coefficient that takes into account the combined action of the base resistance and internal pressure:

where E gr is the modulus of deformation of the backfill (backfill), taken depending on the degree of compaction (for CR 0.5 MPa); Р - internal pressure of the transported substance, Р< 0,8 МПа.

Sequentially substituting the initial data into the main formulas above, as well as into the intermediate ones, we obtain the following calculation results:

Analyzing the results of calculations for this case, it can be noted that in order to reduce the value of P pr, it is necessary to strive to reduce the value of P "z + P to zero, that is, equality in the absolute value of the values ​​of P" z and P. This can be achieved by changing the degree filling a polyethylene pipeline with water. For example, with a filling equal to 0.95, the positive vertical component of the water pressure force P on the inner cylindrical surface will be 694.37 N / m at P "z = -690.8 N / m. Thus, by adjusting the filling, one can achieve data equality quantities.

Summing up the results of checking the bearing capacity according to condition II for all variants, it should be noted that the maximum permissible deformations do not occur in the polyethylene pipeline.

Checking the bearing capacity according to condition III

The first stage of the calculation is to determine the critical value of the external uniform radial pressure P cr, MPa, which the pipe can withstand without losing its stable cross-sectional shape. The smaller of the values ​​calculated by the formulas is taken as the value of P cr:

P cr = 2√0.125 P l E gr = 0.2104 MPa;

P cr = P l +0.14285 = 0.2485 MPa.

In accordance with the calculations by the formulas above, a smaller value of P cr = 0.2104 MPa is taken.

The next step is to check the condition:

where k 2 is the coefficient of pipeline operating conditions for stability, taken equal to 0.6; R vac - the value of the possible vacuum at the repair section of the pipeline, MPa; Р Гв - external groundwater pressure above the top of the pipeline, according to the condition of the problem Р Гв = 0.1 MPa.

The subsequent calculation is carried out by analogy with condition II for several cases:

• for the case of uniform backfilling of the annular space in the absence of water in the polyethylene pipeline:

thus, the condition is fulfilled: 0.2104 MPa >> 0.1739 MPa;

• the same in the presence of filler (water) in the polyethylene pipeline:

thus, the condition is met: 0.2104 MPa >> 0.17 MPa;

• for the case of uneven backfilling of the annular space in the absence of water in the polyethylene pipeline:

thus, the condition is fulfilled: 0.2104 MPa >> 0.1743 MPa;

• the same in the presence of water in the polyethylene pipeline:

thus, the condition is fulfilled: 0.2104 MPa >> 0.1733 MPa.

Checking the bearing capacity according to condition III showed that the stability of the circular shape of the cross-section of the polyethylene pipeline is observed.

As a general conclusion, it should be noted that the implementation construction works the backfilling of the annular space for the corresponding initial design parameters will not affect the bearing capacity of the new polyethylene pipeline. Even in extreme conditions(with uneven backfilling and high level groundwater), backfilling will not lead to undesirable phenomena associated with deformation or other damage to the pipeline.

selection of pipes and materials for the construction and reconstruction of water supply pipelines

at the facilities of Mosvodokanal JSC

1. At the design stage, depending on the laying conditions and the method of work, the material, the type of pipe (pipe wall thickness, standard dimensional ratio (SDR), ring stiffness (SN), the presence of external and internal protective coating of the pipe) are selected, the issue of strengthening the laid pipes using a reinforced concrete clip or a steel case. For all pipe materials, it is necessary to carry out a strength calculation for the effect of the internal pressure of the working medium, soil pressure, temporary loads, the own weight of the pipes and the mass of the transported liquid, atmospheric pressure with the formation of vacuum and external hydrostatic pressure of groundwater, determination of the axial pulling force (punching).

2. Before choosing a reconstruction method, technical diagnostics of the pipeline is carried out in order to determine its condition and residual life.

3. The choice of the pipeline material must be justified by a comparative technical and economic calculation. The calculation is carried out taking into account the requirements of Mosvodokanal JSC. When crossing existing engineering communications or the location of the pipeline in their security zone, the requirements of third-party operating organizations are taken into account. The feasibility study and strength calculations of the pipeline are included in the design and estimate documentation and are presented when the project is considered.

4. All materials used for laying water supply networks (pipes, thin-walled liners, sleeves and internal spray coatings) must undergo additional tests for the general toxic effect of constituent components that can diffuse into water in concentrations hazardous to public health and lead to allergenic, skin and irritating, mutagenic and other negative effects on humans.

5.When laying polyethylene pipes without a reinforced concrete cage or a steel case in urbanized and industrial areas, the environmental safety of the surrounding soil along the design route must be confirmed. In the case of unacceptable contamination in the soil and groundwater(aromatic hydrocarbons, organic chemicals, etc.) soil reclamation is carried out.

6. Steel pipes previously used not for drinking water supply pipelines are not allowed for the installation of water supply bypasses.

7. Recovered previously used steel pipes are not allowed for new laying and reconstruction of water pipelines (pipes for the working environment). It is possible to use them for the device of cases.

8. Steel spiral pipes (in accordance with GOST 20295-85 with volumetric heat treatment) may be used when constructing cases, bypass lines.

9. When laying pipes in cases, the annular space is backfilled with a cement-sand mortar.

10.With new construction steel pipelines open-laid water pipelines (without steel cases and reinforced concrete clips) provide, if necessary, simultaneous protection of the pipe from electrochemical corrosion according to GOST 9.602-2005.

11. During the reconstruction of steel pipelines (without steel cases and reinforced concrete clamps) without destroying the existing pipe and during the prompt restoration of local and emergency sections of pipelines using methods that do not have bearing capacity, provide, if necessary, the simultaneous protection of the pipe from electrochemical corrosion in accordance with GOST 9.602-2005.

12. It is allowed to use cast fittings made of ductile iron with internal and external epoxy-powder coating, permitted for use in drinking water supply systems (certificate of state registration, expert opinion on the compliance of products with the Unified Sanitary-Epidemiological and Hygienic Requirements for Goods Subject to Sanitary-Epidemiological supervision).

13. Specialists of Mosvodokanal JSC have the right to visit factories supplying pipes and get acquainted with the conditions for organizing production and quality control of products, as well as inspect the supplied products.

14. Tests of polyethylene pipes are carried out on samples made of pipes.

14.1. The characteristics of the pipe material must correspond to the following values:

Thermal stability at 200 ° C - not less than 20 minutes;

Mass fraction of technical carbon (soot) - 2.0-2.5%;

Distribution of carbon black (soot) or pigment - type I-II;

Elongation at rupture of a pipe sample - not less than 350%.

14.2. When checking a welded seam, the destruction of the sample should occur when the relative elongation reaches more than 50% and be characterized by high ductility. The break line must run over the base material and not intersect the weld plane. The test results are considered positive if, when tested for axial tension, at least 80% of the samples have a ductile type I fracture. The remaining 20% ​​of the samples may have a type II fracture pattern. Destruction of type III is not allowed.

2.Technical requirements for the use of pipes and materials

for the construction and reconstruction of the sewerage system at the facilities of JSC "Mosvodokanal"

MGSN 6.01-03
	For diameter over 3000 mm		2.2.3.1.B. Installation of fiberglass pipes for relining, Fiberglass pipes made by the technology of continuous winding of fiberglass based on polyester binders; Hobas "quality DA", manufactured by centrifugation, with an inner liner based on a vinyl ester binder with a thickness of at least 1.0 mm at a sleeve connection with pipe centering. Ring stiffness of pipes is not less than SN 5000 N / m2. GOST R 54560-2011, GOST ISO 10467-2013, SP 40-105-2001, MGSN 6.01-03
	2.2.3.2.B Installation of composite elements made of polymer concrete MGSN 6.01-03
	Pressure sewer pipelines
	New construction of pressure pipelines
		Trenching	Trenchless laying
3.1.T. Laying of pipes made of ductile iron with spheroidal graphite (VChShG) with external zinc coating and internal chemically resistant coating GOST R ISO 2531-2012, SP 66.133330.2011	3.1.B. Installation of pipes made of ductile iron with spheroidal graphite (VChShG) on a permanent joint with an outer zinc coating and an inner chemical-resistant coating in a case with centering. MGSN 6.01-03
		3.2.T. Laying longitudinal steel pipes with an inner cement-sand coating and outer insulation of a very reinforced type in accordance with GOST 9.602-2005 with a simultaneous electrical protection device, if necessary. GOST 20295-85, MGSN 6.01-03	3.2.B. Installation of longitudinal steel pipes with an internal cement-sand coating and external insulation of a very reinforced type in accordance with GOST 9.602-2005 in a case with centering. Diameter up to 500mm - steel grade St20 Diameter 500mm and more - steel grade 17G1S, 17G1SU GOST 10704-91, GOST 10705-80, GOST 10706-76, GOST 20295-85, MGSN 6.01-03
		3.3.T. Laying: Fiberglass pipes made using FLOWTITE technology by continuous fiberglass winding using unsaturated polyester resins. The ring stiffness of the pipes to be laid is at least SN 10,000 N / m2. Coupling connection. Gasket in a reinforced concrete cage or case. GOST R ISO 10467-2013, SP 40-105-2001	3.3.B... Mounting: Hobas "quality DA" fiberglass pipes, manufactured by centrifugation, with an inner liner based on a vinyl ester binder with a thickness of at least 1.0 mm; The ring stiffness of the pipes to be laid is at least SN 10,000 N / m2. Coupling connection. Gasket in pre-padded case with centering.
		3.4.T. Laying of single-layer polyethylene pipes made of PE100 on a welded joint in a reinforced concrete cage or case	3.4.B. PE100 on a welded joint in a pre-laid case.
		3.5.T For diameters up to and including 300mm: Laying of pressure pipes made of polyethylene PE100 in soils with a bearing capacity of at least 0.1 MPa (sands) and foundation and backfilling in accordance with the requirements of the "Regulations for the use of polyethylene pipes for the reconstruction of water supply and drainage networks" (section 4). GOST 18599-2001, SP 40-102-2000	3.5.B. For HDD method - PE100-MP GOST 18599-2001, MGSN 6.01-03, SP 40-102-2000
	Reconstruction of existing pressure pipelines
	Reconstruction with destruction of the existing pipe		4.1.1.B. Installation of pipes made of ductile iron with spheroidal graphite (VChShG) on a permanent joint with an outer zinc coating and an inner chemically resistant coating GOST ISO 2531-2012, SP 66.133330.2011, MGSN 6.01-03
			4.1.2.B. Installation of steel pipes with an internal cement-sand coating and external insulation of a very reinforced type in accordance with GOST 9.602-2005. Diameter up to 500mm - steel grade St20 Diameter 500mm and more - steel grade 17G1S, 17G1SU GOST 10704-91, GOST 10705-80, GOST 10706-76, GOST 20295-85, MGSN 6.01-03
			4.1.3.B. Installation of pressure pipes made of polyethylene PE100-MP with external protective coating from mechanical damage based on mineral-filled polypropylene. The connection is welded. GOST 18599-2001, MGSN 6.01-03, SP 40-102-2000
			4.1.4.B. Mounting: Hobas "quality DA" fiberglass pipes, manufactured by centrifugation, with an inner liner based on a vinyl ester binder with a thickness of at least 1.0 mm; Fiberglass pipes made using FLOWTITE technology by continuous fiberglass winding using unsaturated polyester resins. Ring stiffness of the pipes to be laid, not less SN 10,000 N / m2. Coupling connection. GOST R ISO 10467-2013, MGSN 6.01-03
	Reconstruction without destruction of an existing pipe		4.2.1.B. Installation of pipes made of ductile iron with spheroidal graphite (VChShG) on a permanent joint with an outer zinc coating and an inner chemically resistant coating with pipe centering.
			4.2.2.B. Installation of steel pipes with an internal cement-sand coating and external insulation of a very reinforced type in accordance with GOST 9.602-2005 with pipe centering. Diameter up to 500mm - steel grade St20 Diameter 500mm and more - steel grade 17G1S, 17G1SU GOST 10704-91, GOST 10705-80, GOST 10706-76, GOST 20295-85, MGSN 6.01-03
			4.2.3.B. Installation of pressure pipes made of polyethylene PE100 on a welded joint. Preliminary preparation of the inner surface of the pipeline should exclude unacceptable damage to the pipe during pulling through. GOST 18599-2001, MGSN 6.01-03, SP 40-102-2000
			4.2.4.B... Mounting: Hobas "quality DA" fiberglass pipes, manufactured by centrifugation, with an inner liner based on a vinyl ester binder with a thickness of at least 1.0 mm; Fiberglass pipes made using FLOWTITE technology by continuous fiberglass winding using unsaturated polyester resins. The ring stiffness of the pipes to be laid is at least SN 10,000 N / m2. Coupling connection with pipe centering. GOST R ISO 10467-2013, MGSN 6.01-03
			4.2.5.B... Inverting polymer-fabric and composite sleeves with subsequent vulcanization using a heat carrier or ultraviolet radiation: Polymer sleeves manufactured using the Aarsleff technology (Denmark); Complex hose manufactured using Bertos technology (Russia) TU 2256-001-59785315-2009; A thermosetting composite reinforced sleeve manufactured using the COMBILINER TUBETEX KAWO technology (Czech Republic). The ring stiffness of the sleeves is taken by calculation or by regulatory documents depending on the residual resource of the pipeline. MGSN 6.01-03
	Laying of siphons
	5.1. Trenchless laying of a working pipe in a case with centering	5.1.1. Polyethylene pressure pipes PE100 GOST 18599-2001, MGSN 6.01-03, SP 40-102-2000
		5.1.2. Longitudinal steel pipes with an internal cement-sand coating and external insulation of a very reinforced type in accordance with GOST 9.602-2005 Diameter 500mm and more - steel grade 17G1S, 17G1SU
		5.1.3. Pipes made of ductile iron with spheroidal graphite (VChShG) permanently connected with an outer zinc coating and an inner chemical resistant coating with pipe centering. GOST ISO 2531-2012, SP 66.133330.2011, MGSN 6.01-03
		5.1.4. Mounting: Fiberglass pipes made by the technology of continuous winding of fiberglass based on polyester binders; Fiberglass pipes made using the "Steklokompozit" technology on the basis of polyester resins; Hobas "quality DA" fiberglass pipes, manufactured by centrifugation, with an inner liner based on a vinyl ester binder with a thickness of at least 1.0 mm; Fiberglass pipes made using FLOWTITE technology by continuous fiberglass winding using unsaturated polyester resins. The ring stiffness of the pipes to be laid is at least SN 5000 N / m2 (for gravity networks) and SN 10000 N / m2 (for pressure pipelines). Coupling connection. GOST R 54560-2011 (for gravity networks), GOST R ISO 10467-2013, MGSN 6.01-03, SP 40-105-2001
	5.2. HDD laying	5.2.1. Pipes made of ductile iron with spheroidal graphite (VChShG) permanently connected with an outer zinc coating and an inner chemical resistant coating. GOST ISO 2531-2012, SP 66.133330.2011, MGSN 6.01-03.
		5.2.2. Polyethylene pressure pipes PE100-MP with an outer protective coating against mechanical damage based on mineral-filled polypropylene. The connection is welded. GOST 18599-2001, MGSN 6.01-03, SP 40-102-2000
	5.3. Works are performed from the surface of the water	5.3.1 ... Longitudinal steel pipes with an inner cement-sand coating and an outer protective concrete ballast coating, made in the factory. Diameter up to 500mm - steel grade St20