Patent Publication Number: US-2022226859-A1

Title: Device for robotic internal insulation of a pipeline welded joint

Description:
FIELD OF THE INVENTION 
     The invention relates to pipeline construction and can be used for internal insulation of the pipeline welded joint with inside protective coating. 
     BACKGROUND OF THE INVENTION 
     There is a device for implementing Chuiko&#39;s method for internal monolithic insulation of the welded pipeline connection (RU 2667856, published on 24 Sep. 18) that involves the coaxial installation of a steel protective bushing inside the joined pipes; after the pipe joint is welded, the end annular gaps between the protective bushing and the joined pipes are sealed so that an annular cavity is made between the bushing outer surface, welded joint inner surface and the adjacent surfaces of the joined pipes, then air is pumped out from the annular cavity and it is filled with the compound. 
     The device for sealing end annular space is equipped with a power unit comprising a cylindrical elastic actuator and a shell of elastic anti-adhesion material coaxially installed on the actuator&#39;s surface. The actuator is pressurized inside, the actuator is radially expanded, and the shell is pressed against the protective busing and the surfaces of the joined pipes on both sides of the protective bushing. When the compound polymerization process is completed, the pressure inside the actuator is decreased, the shell is disconnected from the protective bushing and the inner surfaces of the connected pipes, then the sealing device is dismantled from the pipeline. The device for sealing end annular space is not equipped with a special device for filling the annular space with compound. 
     The device for underground pipeline repair (U.S. Pat. No. 4,861,248 A, 29 Aug. 1989) that consists of a cylindrical elastic shell with rigid cylindrical plugs inserted at its ends, which form a closed airtight circuit together with the shell, is the closest to the proposed technical solution. The plugs inside the device cavity are connected to each other by a rope that limits their movement relative to each other. There is a through hole in one of the plugs with a hose connection for supplying compressed air into the device inner cavity. In the central part of the elastic shell, a sleeve or bushing is hard mounted on its surface, these parts cannot be separated from each other. This way, the shell middle section is made stiffer. 
     In addition, at the first option of the device, two parallel tubes are inserted into the device inner cavity through the end plug. The two components of the two-component compound can be fed through these tubes by separate channels. In the central part of the device inner cavity, these two tubes are interconnected. A third short, curved tube connecting these two tubes to the nozzle is connected to the point of the two tubes connection. The short, curved tube serves as a static mixer. In turn, the nozzle mounted in the middle of the elastic shell, through its central opening, extends the connected tube channel to the device outer cylindrical surface. 
     The first option device operates as follows. The device is inserted into the pipe cavity. The device center is placed in the center of the area to be isolated. Compressed air is pumped into the device inner cavity. The peripheral parts of the elastic shell inflate and press against the pipeline inner surface. Annular space is created between the outer surface of the elastic shell central part and the inner surface of the pipeline insulated part. The two components of the two-component compound are fed into the device inner cavity through two tubes. The compound components enter a short, curved tube in the immediate vicinity of the device center, and there they are combined into one flow. The author claims this short tube with a curve operates as a static mixer. The released mixture fills the annular space cavity and hardens. After the compound is polymerized, compressed air pressure is released in the device cavity, the elastic shell shrinks and comes out of contact with the pipeline walls and the polymerized compound surface. The device is removed from the pipeline cavity. 
     The first option of the device has the following shortcomings:
         1) The annular space cavity created by the device has only one channel through which the compound is pumped into it. As the compound fills the annular gap cavity, the residual air is compressed and, as a result, the internal pressure in the cavity increases. When the air pressure inside the annular space cavity reaches the level of the injected compound pressure, the annular space stops filling. The annular space cavity is only partially filled. And due to the law of universal gravity, the compound fills only the lower part of the cavity. The upper part of the annular space cavity is left empty. The device in question is not suitable for isolating defective sections of pipelines.   2) There is no effective option for controlling over the mixing quality of the compound components in the device at all. The quality of the compound components mixing when they pass through the short, curved tube of the device is many times worse than the quality of the compound mixing when it passes through even one section of a static mixer practically of any level. For this reason, the annular space cavity is filled with a stratified mixture of compound components obviously unsuitable for annular space isolation.   3) The invention does not have its own built-in dispensing equipment. Therefore, it is necessary to use a third-party dosing unit to fill the annular space cavity with compound, and it is usually not possible to place it in very close proximity in the pipeline inner cavity. In order to feed the compound components from the dosing unit to the device, one should use quite long hoses. When almost any two-component compound dosing unit is turned on, the two compound valves open synchronously. Most two-component compounds use a volume proportional mixing ratio that is different from the 1:1 ratio. Therefore, with the dosing unit in operation, the cavities of the feed hoses and tubes are filled asynchronously. The compound component with the higher proportional mixing volume ratio fills the feed hose cavity and begins to flow into the short, curved tube and into the annular space cavity. As the annular cavity is pressurized because there is no second channel, the first component starts to fill the cavity of the hose supplying the second component of the compound at the same time. When the cavity of the second hose is fully filled, the compound components start mixing inside the hose feeding the component with the lower mixing ratio. This results in compound polymerization in the second hose making the device inoperable. The annular space cavity is either completely filled with one component of the compound, or with a compound with an unacceptable mixing ratio. For example, if the two-component compound B9M10+CG9900875MF is used for the inner insulation of a pipeline welded joint and the material is supplied from the dosing unit to the welded joint over a distance of 40 m through 9 mm hoses, more than 4 liters of CG9900875MF will be supplied until the mixture reaches the annular space cavity.   4) Since the device does not have temperature control, it cannot be used at temperatures other than those specified by the manufacturer for the compound.   5) There is no control over the thickness of the filling of the annular space cavity with compound.   6) There is no control over the quality of the compound that fills the annular space.   7) It is impossible to remove low-quality compound from the circuit feeding it into the annular space cavity.   8) It is impossible to wash the device feeding hoses and tubes once the process of filling the annular space with compound is finished.       

     At the second option of the device, two parallel tubes are inserted into the device inner cavity through the end plug. The two components of the two-component compound can be fed through these two tubes by separate channels. In the central part of the device inner cavity, these two tubes are radially extended into the cavity of a special hydraulic cylinder with a piston. The hydraulic cylinder piston is connected to the pneumatic cylinder rod. The open side of the hydraulic cylinder is installed on an elastic cylindrical casing. The hydraulic cylinder cavity is coupled to the device&#39;s outer surface. The hydraulic cylinder cavity serves as a static mixer. 
     The second option device operates as follows. The device is inserted into the pipe cavity. The device center is placed in the center of the area to be isolated. Compressed air is pumped into the device inner cavity. The peripheral parts of the elastic shell inflate and press against the pipeline inner surface. Annular space is created between the outer surface of the elastic shell central part and the inner surface of the pipeline insulated part. The two components of the two-component compound are fed into the device inner cavity through two tubes. In the device middle part, the compound components are fed into the hydraulic cylinder cavity, where they are combined into one flow. The author claims that flows are mixed in the hydraulic cylinder cavity. The released mixture fills the annular space cavity and hardens. After the compound is polymerized, compressed air pressure is released in the device cavity, the elastic shell shrinks and comes out of contact with the pipeline walls and the polymerized compound surface. The device is removed from the pipeline cavity. 
     The second option of the device has all the disadvantages of the first version with two more specific disadvantages:
         1) There is no static mixer at all.   2) The hydraulic device for mechanical cleaning of the unit for supplying sealing material into the annular space cavity must be repaired after each isolation cycle as the compound inevitably polymerizes in the hydraulic cylinder cavity.       

     SUMMARY OF THE INVENTION 
     The invention solves the technical problem through the creation of a device for robotic internal insulation of a pipeline welded joint that provides a full cycle of high-quality monolithic insulation of a welded joint in a pipeline inner cavity at minimum cost. 
     The technical problem is solved by a device for internal isolation of a pipeline welded joint that comprises a sealing unit including a cylindrical casing and coaxially mounted cylindrical actuator designed to expand radially when excess pressure is created in its cavity, a compound feeding unit, compound dosing unit and pneumatic automation unit located in the casing, dosing unit operating cavities for each compound component are connected to the compound feeding unit, the elastic actuator has a channel for feeding the compound in an annular space in the area of the welded joint, the annular space being connected with the compound feeding unit and with a channel for gas evacuation from the annular space, and the pneumatic automation unit is designed to control operation of the dosing unit and the compound feeding unit and to control creating excess air pressure in the sealing unit actuator cavity. 
     Moreover, preferably, the actuator comprises the actuator comprises an elastic sleeve and an elastic shell made of an anti-adhesion material located on the sleeve, and the channel for feeding the compound into the annular space in the area of the welded joint and the channel for evacuating gas from the mentioned annular space are made in the elastic shell. 
     The preferred design includes the elastic sleeve has annular protrusions on the end sections on the inside, located in annular grooves on the outside of the sealing unit casing, and on each end section of the elastic sleeve on the outside there is a retaining bushing in contact with an end of the elastic shell. 
     It is advisable to have a film heater located on the outer surface of the sealing unit casing. 
     Moreover, the dosing unit comprises a cylindrical casing with a piston assembly installed in it, which includes two pistons mounted hermetically in the casing, the pistons are connected by a rod installed hermetically inside an annular cavity separator mounted on the inside surface of the casing, the rod has an axial channel connected to the pneumatic automation unit and radial channels connected to the axial channel with their outputs located near the first piston located at the compound feeding unit side. 
     The sealing unit casing forms the dosing unit casing in the preferable design. 
     In addition, the compound feeding unit comprises a casing in which a static mixer, a valve assembly with valves integrated into the casing of the compound feeding unit, and a washing fluid tank connected to channels for supplying compound components to the static mixer. 
     The preferred design has the compound feeding unit casing made of two cylindrically shaped parts of different diameters, the static mixer is coaxially located inside said casing, the valves of the valve assembly are located in the part of the casing of larger diameter, and the washing fluid tank is a hydraulic accumulator formed by outer surface of the part of the casing of smaller diameter and the cylindrical membrane fastened to said casing. 
     Besides, a piston operating cavity of the dosing unit is located between the end face of the compound feeding unit and the first piston of the piston assembly and is connected to an inlet cavity of the first valve of the valve assembly through a channel designed in the compound feeding unit casing; a rod operating cavity of the dosing unit is located between the second piston of the piston assembly and the annular separator and is connected to an inlet cavity of the second valve of the valve assembly through channels in the sealing unit casing and in the compound feeding unit casing; output cavities of the first and second valves of the valve assembly are connected to an inlet of the static mixer through channels in the casing of the compound feeding unit, an outlet of the static mixer is connected to a channel for compound feeding into the annular space, said channel is designed in the elastic shell of the sealing unit, and the washing fluid tank is connected through the third valve of the valve assembly to output cavities of the first and second valves of the valve assembly. 
     Moreover, the pneumatic automation unit comprises a casing with a pneumatic valve island, at least one working channel of the pneumatic valve island is connected to the piston operating cavity of the dosing unit located between the second piston and the end face of the pneumatic automation unit; other operating channels of the pneumatic valve island are connected through channels in the sealing unit casing respectively to the actuator cavity of the sealing unit, to the cavity of the washing fluid tank and to valve drives of the valve assembly, and a position sensor of the piston assembly connected with the pneumatic valve island is located at the end face of the pneumatic unit casing, which faces the piston assembly. 
     Moreover, an outlet of the static mixer of the compound feeding unit is connected to the compound feeding channel of the sealing unit actuator by means of an elastic tube with the first pinch valve installed on it; also said outlet of the static mixer is connected to an elastic tube for poor-quality compound removal with the second pinch valve installed, and a channel for evacuating air from the annular space of the sealing unit actuator is connected to an elastic pumping tube with the third pinch valve installed, and the pinch valves are located in the compound feeding unit casing, and other operating channels of the pneumatic valve island are connected through channels in the sealing unit casing to the pinch valve drives. 
     The preferred design has the channel for gas evacuation from the annular space is connected to a vacuum trap. 
     In this case, it is advisable that the elastic tube for poor-quality compound removal and the elastic pumping tube are connected to a vacuum trap. 
     In the preferred design, the vacuum trap includes a cylindrical casing divided by a partition wall with an opening for smaller and larger chambers; there is a tank in the larger chamber, which is suspended in the casing on load cells and which has an opening on the side facing the partition wall and on the opposite side the tank is connected to flexible discharge and evacuation tubes, while there is an air filter in the smaller chamber between the opening in the partition wall and an outlet nozzle. 
     This invention solves the following problems:
         1) The operation for delivering and mounting the protective bushing to the pipeline welded joint inside its cavity is automated.   2) The operation for sealing the end annular space of the annular space cavity between the protective bushing and the inner walls of the pipeline is automated.   3) The operation for evacuating air from the annular space cavity of the pipeline welded joint is automated.   4) The operation for monitoring the annular space cavity tightness between the protective bushing and the pipeline inner walls is automated.   5) The delivery of the compound components to the insulated welded joint inside the pipeline cavity is automated.   6) The suggested device has a built-in thermal control system that ensures maintenance of the compound specified temperature at ambient temperatures ranging from +40 to minus-50 degrees Celsius.   7) The suggested device incorporates a high-precision automated system for dosing and injecting two-component compound into the annular space cavity between the protective bushing and the pipeline inner walls.   8) A highly efficient static two-component compound mixer is built into the suggested device, which makes it possible to control the mixing quality in a broad range.   9) The suggested device has a built-in tank (hydraulic accumulator) for delivery, storage and discharge of washing fluid and automatic maintenance of the internal pressure at a pre-set level.   10) The suggested device is equipped with a system providing automatic washing of the static mixer and compound supply channels in the annular space cavity between the protective bushing and the pipeline inner walls.   11) A distributed microprocessor control unit is built into the suggested device.   12) The suggested device incorporates a system for automatic control of filling the annular space cavity between the protective bushing and the pipeline inner walls with compound.   13) The suggested device incorporates an automated system for removing poor-quality compound before it is injected into the cavity of the annular space between the protective bushing and the pipeline inner walls.   14) The suggested device is equipped with an automated system for detecting compound with gas inclusions in the annular space cavity and its removal from there.   15) The suggested device integrates a system for continuous monitoring of the compound components reserves.   16) The proposed device incorporates a system for monitoring the flow of compound components and washing fluid at the static mixer inlet.   17) The suggested device is equipped with a system for monitoring the flow of compound and washing fluid at the static mixer outlet.   18) The use of the suggested device eliminates the human factor impact on the process duration and the quality of the internal insulation of the pipeline welded joint.   19) The usage of the suggested device eliminates the impact of weather and climatic conditions on the process duration and the quality of the pipeline welded joint inner insulation.   20) With the suggested device, it is possible to internally insulate welded joints of above-ground, underground and underwater pipelines.       

    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1 . General view of the suggested device. 
         FIG. 2  General view of the suggested device with a vacuum trap. 
         FIG. 3  Main units of the suggested device. 
         FIG. 4  Location of the suggested device and its main units in the pipeline cavity in course of the pipeline welded joint internal insulation. 
         FIG. 5  Axial section of the annular space in the area of the pipeline welded joint formed by the suggested device. 
         FIG. 6 . Diagram of the suggested device assembly/disassembly. 
         FIG. 7 . The sealing unit axial section. 
         FIG. 8 . General view of the sealing unit. 
         FIG. 9 . The sealing unit casing design. 
         FIG. 10 . Axial section of the sealing unit casing along the plane passing through the axis of a radial hole on its outer surface. 
         FIG. 11 . Appearance of the elastic shell with bedding for the protective bushing. 
         FIG. 12 . Local section of the sealing unit along the plane passing through the axis of the channel for feeding compound into the welded annular space and the axis of the channel for gas evacuation from the mentioned space. 
         FIG. 13 . Local section of the sealing unit casing along the plane passing through the axis of a radial hole on its outer surface. 
         FIG. 14 . Axial section of the suggested device assembly in a horizontal plane. 
         FIG. 15 . Axonometric view of the drive piston cavity of the compound components dosing unit. 
         FIG. 16 . Axonometric view of the piston assembly of the compound components dosing unit with a cutout. 
         FIG. 17 . Scheme of the compound components dosing unit in the piston assembly intermediate position during impregnation of the annular space in the welded joint area. 
         FIG. 18 . Scheme of the compound components dosing unit in the initial position of the piston assembly ready for impregnation of the annular space in the welded joint area. 
         FIG. 19 . Scheme of the compound components dosing unit after completion of the annular space impregnation in the welded joint area. 
         FIG. 20 . Scheme of the pneumatic automation unit assembly/disassembly. 
         FIG. 21 . Axial section of the pneumatic automation unit along the plane passing through the reverse valve axis  59 . 
         FIG. 22 . Axonometric view of the pneumatic automation unit with a cutout. 
         FIG. 23 . Frontal section of the suggested device along the plane passing through the channel axis  62  in  FIG. 22 . 
         FIG. 24 . Axonometric view of the compound feeding unit. 
         FIG. 25 . Scheme of the compound feeding unit assembly/disassembly. 
         FIG. 26 . Scheme for assembly/disassembly of static mixer with the valve assembly at the inlet. 
         FIG. 27 . Static mixer actuator. 
         FIG. 28 . Valve regulating the liquid component flow at the static mixer inlet, in closed position. 
         FIG. 29 . Valve regulating the liquid component flow at the static mixer inlet, in open position. 
         FIG. 30 . Axonometric view of a static mixer with the valve assembly at the inlet with the lid removed. 
         FIG. 31 . Axonometric view of a static mixer with the valve assembly at the inlet with a cutout in two mutually perpendicular planes. 
         FIG. 32 . Axonometric view of the static mixer with the valve assembly at the inlet with a cutout on a plane passing through the longitudinal axes of channels  93  and  94 , and on a plane passing through axes of radial channels connected to cavities above pistons ( FIG. 28  and  FIG. 29 ) of pneumatic drives of the valves  73 ,  74  and  75 . 
         FIG. 33 . Axonometric view of the static mixer with the valve assembly at the inlet with a cutout on a plane passing through the axes of channels  96  and  97 , and on a plane passing through axes of radial channels connected to the cavities under pistons ( FIG. 28  and  FIG. 29 ) of pneumatic drives of the valves  73 ,  74  and  75 . 
         FIG. 34 . Axonometric view of the static mixer with the valve assembly at the inlet with a cutout on a horizontal plane passing through axis of channel  99 , and on a plane passing through arc-shaped axes of radial channels connected to pressure spaces  87 ,  88  and  89  ( FIG. 28  and  FIG. 29 ) of valves  73 ,  74  and  75 . 
         FIG. 35 . Static mixer section with the valve assembly at the inlet by plane passing through axes of valves  73 ,  74 . 
         FIG. 36 . Axonometric view of the static mixer with the valve assembly at the inlet with a cutout on a horizontal plane passing through axes of valves  73 ,  74  and on a plane passing through axes of channels  112  and  113  ( FIG. 35 ). 
         FIG. 37 . Axonometric view of the static mixer with the valve assembly at the inlet with a cutout on a plane passing through axes of channels  95  and  101 , and on the perpendicular plane passing through axes of channels  102  and  107 . 
         FIG. 38 . Hydraulic accumulator design. 
         FIG. 39 . Axonometric view of the suggested device with a cutout on a plane passing through axes of channels  27  and  120  which connect the air cavity of the hydraulic accumulator with the pneumatic automation unit. 
         FIG. 40 . Axonometric view of a hydraulic accumulator with a cutout on a plane passing through axes of the compressed air discharge channels. 
         FIG. 41 . Axonometric view of a hydraulic accumulator with a cutout and view of channel  105  in the hydraulic cavity. 
         FIG. 42 . Axonometric view of the suggested device with a complex cutout on the planes passing through axes of channels that connect the piston operating cavity of the compound components dosing unit with a channel  101  and a quick-release coupling  71 . 
         FIG. 43 . Axonometric view of a compound feeding unit with a complex cutout on planes that pass through axes of channels that connect the inner contour of the hydraulic accumulator to a channel  100  and a quick-release coupling  70 . 
         FIG. 44 . Axonometric view of a compound feeding unit fragment with a complex cutout on planes of passing channels from a quick-release coupling  69  to a channel  103 . 
         FIG. 45 . Axonometric view of the compound feeding unit from the flange side without the static mixer and the valve assembly and without the hydraulic accumulator. 
         FIG. 46 . Axonometric view of the compound feeding unit from the pinch valves side without the static mixer and the valve assembly and without the hydraulic accumulator. 
         FIG. 47 . Cross section of a flange  126  of the flow control assembly at the static mixer outlet on a plane passing through axes of channels connected to cavities above and below pistons of pneumatic actuators of the pinch valves  129  and  130 . 
         FIG. 48 . Axonometric view of the compound feeding unit from the side of the pinch valves without the static mixer and the valve assembly and without the hydraulic accumulator with a complex cutout on planes passing through axes of channels that connect a cavity above a piston of a pneumatic actuator of the valve  132  with an opening extending to a flange surface. 
         FIG. 49 . Axonometric view of the compound feeding unit from the side of the flange  126  without the static mixer and valve assembly and without the hydraulic accumulator with a complex cutout on planes passing through axes of channels that connect a cavity under the piston of the pneumatic actuator of the valve  132  with the opening extending to the flange surface. 
         FIG. 50 . Section of the compound feeding unit passing through axes of channels feeding compound to the annular space. 
         FIG. 51 . Axonometric view of the compound feeding unit from the side of the pinch valves without the static mixer and the valve assembly and without the hydraulic accumulator with a complex cutout along the planes passing through axes of bypass loop channels that connect the central opening of the compound feeding nozzle  141  to said annular space with the nipple  131  of the pinch valve  132 . 
         FIG. 52 . Local section of the compound feeding unit along a plane passing through axes of the compound feeding channels—the pinch valve  130  open. 
         FIG. 53 . Local section of the compound feeding unit along the plane passing through axes of the compound feeding channels—pinch valve  130  shut. 
         FIG. 54 . Vacuum trap. 
         FIG. 55 . Schematic diagram of the suggested device. 
         FIG. 56 . Location of replaceable tubes and quick-release couplings for refueling the suggested device. 
         FIG. 57 . Suggested device with the vacuum trap in condition to prepare it to be inserted into the pipeline cavity to perform welded joint inner insulation. 
         FIG. 58 . Suggested device in the state of engaging the protective bushing on the elastic shell bedding. 
         FIG. 59 . Suggested device with a vacuum trap in the pipeline cavity in the position ready to perform welded joint isolation. 
         FIG. 60 . View of the suggested device in the pipeline cavity after pressure increase in the sealing unit actuator. 
         FIG. 61 . View of the compound feeding unit at the stage of air evacuation from the annular space of the pipeline welded joint. 
         FIG. 62 . Local longitudinal section of the device inside the pipeline cavity along the plane passing through the axes of channels  20  and  21  of the elastic shell in the condition prepared for starting the process of filling the annular space in the joint area. 
         FIG. 63 . Local longitudinal section of the device inside the pipeline cavity along the plane passing through axes of the valves  73  and  74  in the open state. 
         FIG. 64 . View of the suggested device in the pipeline cavity after pressure drop in the sealing unit actuator. 
         FIG. 65 . View of the internally insulated welded joint after the suggested device removal from the pipeline cavity. 
     
    
    
     EXAMPLES OF PREFERRED EMBODIMENTS OF THE INVENTION 
       FIG. 1  shows a general view of the suggested device  1  with external connections. To avoid overloading the drawings, wheels, an electrical power cable and control cables are not shown in all figures. The suggested device is designed for robotic internal insulation of a pipeline welded joint. The device  1  ( FIG. 1 ) is equipped with a tube  2  for connection to a compressed air source, an elastic tube  3  for connection to an air pumping system and an elastic tube  4  for removing poor quality compound generated at the beginning of compound feeding into the annular space and products of washing the system after the filling process of the annular space with compound is over. 
       FIG. 2  shows a general view of the suggested device  1  equipped with a vacuum trap  5 . The vacuum trap  5  is connected to the device  1  through tubes  3  and  4  by means of fittings  6  and  7  located on one end of the vacuum trap  5 . The vacuum trap  5  has fitting  8  mounted on the opposite end. The vacuum trap  5  is connected to a vacuum pump through a connector  8  and a tube  9 . The main purpose of the vacuum trap  5  is to protect the vacuum pump from contaminants such as compound, washing fluid and their vapors. To solve this problem, the vacuum trap  5  catches poorly mixed compound generated at the beginning of its preparation; catches excess compound at the final stage of filling the annular space in the welded joint area; catches products of mixing system cleaning and compound feeding into the annular space in the welded joint area at the final stage of impregnation in the process of washing the static mixer and channels for feeding compound into the annular space cavity. 
       FIG. 3  shows an axonometric view of the device  1  with a partial cutout without the image of the pipeline welded joint. The device  1  is comprised of four main units: a sealing unit  10  that serves multiple functions including the formation of a tight annular space in the welded joint area; a piston assembly  11  of a compound component dosing unit; unit  12  of compound feeding into the annular space in the welded joint area and a pneumatic automation unit  13 . 
       FIG. 4  shows an axonometric view of the suggested device  1  with a partial section in operating condition with an image of the pipeline  14  and the welded joint  15 . The protective bushing  16  is coaxially mounted in the pipeline  14  inner cavity around the welded joint  15 . The sealing unit  10  incorporates a cylindrical elastic actuator, which comprises an elastic sleeve  17  and an elastic shell  18  tightly placed on it. The elastic sleeve  17  is pressed against the elastic shell  18  by compressed air pressure, in turn securing the spatial position of the protective bushing  16 . The protective bushing  16  limits the local radial expansion of the elastic shell  18  and the elastic sleeve  17  of the actuator, as a result an annular space  19  is generated in the area of the welded joint  15 . Outside the protective bushing  16  at both ends of the protective bushing  16 , the elastic sleeve  17  firmly presses the elastic shell  18  against the inner walls of the pipeline  14  by means of compressed air pressure. This way the annular gaps between the inner surface of the pipe walls  14  and the protective bushing  16  are sealed on both ends of the bushing. The creation of the annular space  19  is explained further by the image shown in  FIG. 5 . Two airtight inlets  20  and  21  are integrated into the end section of the elastic shell  18  ( FIGS. 4 and 5 ). The internal channels of airtight inlets  20  and  21  are directly connected to the cavity of the annular space  19  in the area of the welded joint  15 . The airtight inlet  20  is designed to evacuate air from the annular space  19 . The airtight inlet  21  is designed to feed the compound into the cavity of the annular space  19 . 
       FIG. 6  illustrates a diagram for assembly/disassembly of the device  1  from its integral assemblies. During assembly, at the first stage, the piston assembly  11  of the compound components dosing unit is mounted in the middle part of the inner cavity of the sealing unit  10 . Then, the compound feeding unit  12  is inserted into the inner cavity of the sealing unit  10  from one of its ends and pushed up to the stop. The pneumatic automation unit  13  is inserted from the second end of the sealing unit  10  and pushed to the stop. There are integrated flanges on the unit  12  and unit  13 , they are used to provide rigid bolted connection to the sealing unit  10 . 
       FIG. 7  shows an axial section of the sealing unit  10 . The sealing unit  10  involves a cylindrical casing  22  with an actuator coaxially mounted on it, which includes the elastic sleeve  17  and the elastic shell  18  with the integrated airtight inlets  20  and  21 . The design of the sealing unit  10  is clarified by its general view shown in  FIG. 8 . The casing  10  is the supporting and sealing element of the sealing unit  10 . The casing  22  is simultaneously the main supporting element of the entire suggested device  1 . There is a film heater  23  on the surface of the casing  22 , regardless of its operating conditions, it provides a comprehensive temperature control of all units of the device  1  installed on its sealing unit  10 . The elastic sleeve  17  is mounted on top of the film heater  23 . The specially profiled end parts of the elastic sleeve  17  are tightly connected to the casing  22  and clamped by fixation bushings  24  and  25 , it creates closed tight circuit between the outer surface of the casing  22  and the inner surface of the elastic sleeve  17 . The elastic shell  18  firmly adjoins at either side of the ends of the fixation bushings  24  and  25  ( FIG. 7 ), this way it is protected from displacement along the axis of the device  1 . 
       FIG. 9  shows the casing  22  of the sealing unit  10 . The casing  22  has a honed cylindrical inner surface  26 . There are longitudinal channels  22  in the wall of the casing  22 . On both ends of the cylindrical casing  22 , there are annular grooves  28  for annular seals of O-ring type around the outlets of all channels  27 . The casing  22  has a blind hole  29  on the external surface of the casing  22 . There are also threaded fastening openings  30  on both ends of the casing  22 . There are annular grooves  31  on the outer surface of the casing  22  at both ends, these grooves  31  are designed for fixation and ensuring tightness of the connection between the elastic sleeve  17  and the casing  22 . On the outer surface of the casing  22 , there is a cylindrical groove  32 , which occupies the most of its area. This groove  32  is designed for the installation of the film heater  23  ( FIG. 7 ). An annular cavity separator  33  of the compound components dosing unit is mounted in the cavity of the casing  22  on its inner surface  26  by means of press fit method with cooling of the gripped part in liquid nitrogen. There is a groove  34  on the outer cylindrical surface of the cavity separator  33 . After the cavity separator  33  is mounted, the groove  34  with the inner surface  26  of the casing  22  creates a closed annular space. At the stage of production of the casing  22 , this closed annular space is filled with compound through the technological holes (not shown in the drawing), and then the compound is polymerized. This guarantees a tight connection between the cavity separator  33  and the casing  22 . 
       FIG. 10  illustrates a longitudinal section of the casing  22  along the plane passing through its axis and an axis of a radial opening  29  ( FIG. 9 ). The radial opening  29  ( FIG. 10 ) is connected on one side with a blind longitudinal channel  35  created in the casing  22 , while it extends to the outer surface of the casing  22  on the other side. At the opposite end of the casing  22 , there is a longitudinal channel  36  connected with a radial channel  37  that goes on the inner surface of the casing  22  directly at the end wall of the cavity separator  33  of the compound components dosing unit. Such layout enables using the walls of the casing  22  to the fullest extent possible in order to create through longitudinal channels  27  ( FIG. 9 ) inside. 
       FIG. 11  shows an image of the elastic shell  18  external surface fragment from the side of the airtight inlets  20 ,  21 . There is a bedding  38  on the outer surface of the elastic shell  18 , it is made in the shape of a cylindrical recess with the length equal to the length of the protective bushing  16  with side stoppers  39 . The bedding  38  is designed for placement of the protective bushing  16  ( FIG. 5 ) on it. The side stoppers  39  ( FIG. 11 ) limit the protective bushing  16  ( FIG. 5 ) from the axial displacement in the elastic shell  18 . There is an arc-shaped transverse groove  40  ( FIG. 11 ) next to the bedding  38  directly near an edge of the stopper  39 . 
       FIG. 12  shows a fragment of the longitudinal section of the sealing unit  10  on the sealed inlet  20  side. The transverse groove  40  is connected to the airtight input channel  20 . The elastic shell  18  is designed similarly on the side of the airtight inlet  21 . The design of the sealing unit  10  provides a reliable connection of the channels of airtight inlets  20  and  21  with the cavity of the annular space  19  ( FIG. 5 ) in the welded joint area.  FIG. 12  also explains the design solution for sealing the connection between the elastic sleeve  17  and the casing  22  of the seal assembly  10 . The fixation bushing  24  tightly presses the elastic sleeve  17  to the casing  22  of the sealing unit  10 . The fixation bushing  24  prevents the elastic shell  18  from shifting in the axial direction toward the location of the airtight inlets  20  and  21 . The film heater  23  of the suggested device  1  provides continuous heating to a preset temperature of the elastic sleeve  17  and the elastic shell  18  with integrated airtight inlets  20  and  21 . 
       FIG. 13  illustrates a fragment of a longitudinal section of the sealing unit  10  on the side opposite to the location of airtight inlets  20  and  21  on a plane that passes through the axes of a radial opening  29  and a channel  35  ( FIG. 10 ). The fixation and sealing of the elastic sleeve  17  on the casing  22  of the sealing unit  10  is made in the same way as its opposite side. The profiled end of the elastic sleeve  17  is installed in the annular groove  31  of the casing  22 . The fixation bushing  25  presses the elastic sleeve  17  to the casing  22  of the sealing unit  10 . This provides a guaranteed tightness of the connection and fixation of the elastic sleeve  17 . The fixation bushing  25  prevents axial displacement of the elastic shell  18  to the side opposite to the location of the airtight inlets  20  and  21 . The film heater  23  mounted on the casing  22  contains a pass-through opening  41 . The film heater  23  is adhered so that its opening  41  is coaxial to the radial opening  29  in the casing  22  and remains in place during operation. This way, the channel  35  on one side extends to the face of the casing  22  of the sealing unit  10 . On the other side, the channel  35  is connected to the radial opening  29  in the casing  22  and through the opening  41  in the film heater  23  is connected to the closed airtight circuit made up by the elastic sleeve  17  and the outer surface of the casing  22 . 
     The suggested device is equipped with a built-in dosing unit for compound components of the volumetric piston type. The suggested device in its preferred design is configured in such a way that all its main components also constitute an integral part of the integrated compound dosing unit. This made it possible to reduce the number of parts, detachable joints and static seals to achieve weight reduction and compactness of both the dosing unit itself and the suggested device as a whole, and significantly increase their reliability. The design of the dosing unit for compound components is illustrated by the image shown in  FIG. 14 . The casing  22  ( FIG. 14 ) of the sealing unit  10  ( FIG. 3 ) serves as both the body of the dosing unit of two-component compound and as a cylinder containing the piston assembly  11 . The film heater  23  ( FIG. 14 ) provides continuous temperature control of the compound components dosing unit that allows to operate the suggested device  1  practically under any weather conditions. The integrated cavity separator  33  in the casing  22  is equipped with PTFE rod seals manufactured by Freudenberg Sealing Technologies GmbH &amp; Co. KG. The cavity separator  33  is placed in the center of the inner cavity of the compound components dosing unit and divides it into two equal parts. At the same time, a part of the dosing unit inner cavity located on one side of the cavity separator  33 , is designed for dispensing of one component of the compound, and the second part of the dosing unit inner cavity located on the other side of the cavity separator  33 , is designed for dispensing of another component of the compound. Both parts of the dosing unit inner cavity are airtight. The end face of the compound feeding unit  12  that faces the cavity separator  33  is at the same time the front cover of the compound components dosing unit. On the opposite side, the inner cavity of the compound components dosing unit is confined by the pneumatic automation unit  13 . The end surface of the pneumatic automation unit  13  that faces the side of the cavity separator  33  is at the same time the rear cover of the compound components dosing unit that has a hard-mounted position sensor  42  of the piston assembly  11 . The piston assembly  11  is equipped with a high-precision non-contact magnetostrictive linear position sensor Temposonics MH series manufactured by MTS Sensor Technologie GmbH &amp; Co. KG. 
     The inner cavity of the compound components dosing unit is separated into two parts and connected to three channels. The first channel  43  ( FIG. 14 ) connects the compound feeding unit  12  with the adjacent part of an inner cavity of the compound components dosing unit. The second channel  44  ( FIG. 15 ) joins the second part of the inner cavity of the compound components dosing unit with the pneumatic automation unit  13 . The third channel  37  ( FIG. 10 ) in the casing  22  ( FIG. 14 ), located directly at the end face of the cavity separator  33  on the side that faces the pneumatic automation unit  13 , connects the second part of the inner cavity of the dosing unit with a channel  36  ( FIG. 10 ) that extends to the end face  22  ( FIG. 8 ) of the sealing unit  10 . 
     The piston assembly  11  ( FIG. 14 ) has two pistons and a rod. The design of the piston assembly is explained in the image presented in  FIG. 16 . The first piston  45  is firmly connected to the second piston  46  by the rod  47 . This first piston  45  and rod  47  are designed as a monolithic unit, which significantly reduces the risk of leaks and mixing of the two components of the compound in the dosing unit inner cavity. This facilitates operation and greatly increases the compound components dosing unit reliability. To make it possible to mount the piston assembly  11  in the inner cavity of the dosing unit, the second piston  46  is designed as a removable bolted assembly. The rod  47  has a blind axial channel  48  connected to radial channels  49 , the outputs of these channels are located on the surface of the rod  47  directly at the lateral surface of the first piston  45 . On the end of the rod  47  ( FIG. 16 ), there is a bolted assembly of the magnet  50  of the sensor  42  for the position of the piston assembly  11  ( FIG. 14 ) produced by MTS Sensor Technologie GmbH &amp; Co. KG. The pistons  45  and  46  are equipped with PTFE seals manufactured by Freudenberg Sealing Technologies GmbH &amp; Co. KG. 
     The installation of the piston assembly  11  is conducted as follows. Before installing the piston assembly  11  ( FIG. 14 ), the compound components unit  12  and pneumatic automation unit  13  should be removed from the casing  22  of the sealing unit  10 . The piston  46  is removed from the piston assembly  11  ( FIG. 16 ). Rod seals are mounted on the cavity separator  33  ( FIG. 14 ). Piston seals are installed on pistons  45  and  46  ( FIG. 16 ). The piston assembly  11  is inserted into the cavity of the casing  22  ( FIG. 14 ) on the mounting side of the compound feeding unit  12  with the rod  47  inserted forward. Then, the second piston  46  is inserted into the inner cavity of the casing  22  from the side of the pneumatic automation unit  13  fitting; then its installation is completed. The position sensor  42  of the piston assembly  11  is installed on the pneumatic automation unit  13 . When assembled, the pneumatic automation unit  13  is inserted into the cavity of the casing  22 , pushed to the stop and secured by bolting. The compound feeding unit  12  is assembled. 
     The principle of operation of the dosing unit of the components of the compound and the fundamentals to determine its geometric parameters are explained by three diagrams shown in  FIG. 17 ,  FIG. 18  and  FIG. 19 . 
     The main function of the dosing unit is to synchronously dispense the two components of the compound in proportions strictly in accordance with the proportions specified by the compound manufacturer. The second most important function of the dosing unit is to deliver the compound components to the point of the pipeline welded joint insulation in sufficient volume to ensure a full cycle of operation. 
     The dosing should correspond to the volume.  FIG. 17  illustrates a diagram of the compound components dosing unit with the piston assembly  11  in an intermediate operating position. The intermediate position of the piston assembly  11  is described by two parameters: the stroke length reserve L 1  and the travel distance L 2  ( FIG. 17 ). For both parts of the dosing unit inner cavity separated by the cavity separator  33  ( FIG. 17 ), the values of the stroke length reserve L 1  and the travel distance L 2  correspond to each other. The dosing unit cavity enclosed between the compound feeding unit  12  ( FIG. 17 ), the first piston  45  and the walls of the casing  22 , is called the piston operating cavity  51 . Said cavity  51  is designed to be filled with the first component of the compound with a higher proportional value by volume, as specified by the manufacturer of the two-component compound. The channel  43  ( FIG. 14 ) extends into the piston operating cavity  51 . The dosing unit cavity enclosed between the cavity separator  33 , second piston  46 , rod  47  and walls of the casing  22  is called the rod operating cavity  52 . The second component of the compound, which has a smaller proportional value by volume, specified by the manufacturer of the two-component compound, is filled into the rod operating cavity  52  of the dosing unit. The channel  37  ( FIG. 10 ) goes into the rod operating cavity  52 . 
     The dosing unit cavity enclosed between the pneumatic automation unit  13 , the second piston  46  and the walls of the casing  22  is called the piston drive cavity  53  of the dosing unit. Compressed air is pumped into this cavity through the channel  44  ( FIG. 15 ). The dosing unit cavity enclosed between the cavity divider  33 , first piston  45 , rod  47  and walls of the casing  22  is called the rod drive cavity  54  of the dosing unit. The piston drive cavity  53  and the rod drive cavity  54  are connected to each other by an axial channel  48  and radial channels  49  in the rod  47  ( FIG. 16 ). When compressed air is pressurized into the piston drive cavity  53 , the pressure in the rod drive cavity  53  increases synchronously. This rules out possible underpressure in the rod drive cavity  54  and significantly increases the total force of action of compressed air on the piston assembly  11  and, accordingly, the pressure in the operating cavities  51  and  52  of the dosing unit. 
     In the course of operation of the suggested device the position of the dosing unit piston assembly  11  is continuously monitored by a sensor  42  equipped with a sensing element located in the discharge tube  55  ( FIG. 17 ). When the piston assembly  11  displaces, the magnet  50  ( FIG. 16 ) of the sensor  42  ( FIG. 17 ) travels coaxially along the axis of the injection tube  55 , and the sensing element  42  inside it generates a corresponding signal. The signal is processed by the electronic unit of the sensor  42 , so the location of the piston assembly  11  ( FIG. 14 ) is determined. The diameter and depth of the axial channel  48  in the rod  47  ( FIG. 16 ) are made in accordance with the requirements of the manufacturer of the piston assembly position sensor  42 . 
     Compound components dosing unit has three basic geometric parameters: diameter D of pistons  45 ,  46 , piston assembly  11  ( FIG. 17, 18, 19 ); diameter d of the rod  47  of the piston assembly  11  ( FIG. 17, 18, 19 ); length L of the full stroke of the piston assembly  11  ( FIGS. 18, 19 ). 
     The diameter D of pistons  45 ,  46  is assumed to be equal to the diameter of the inner opening of the sealing unit  10  of the casing  22  ( FIG. 7 ). The diameter d of the rod  47  of the piston assembly  11  is computed according to the ratio of the two compound components dispensing. The main parameter of the dosing unit is the numerical value of the volumetric proportional ratio of dosing of the compound components. A deviation of this parameter from the set value entails a decrease in the quality of the polymerizing compound until it becomes completely unusable. The proportional ratio of the operating area of the rod operating cavity  52  of the dosing unit to the working area of the piston operating cavity  51  of the dosing unit must be equal to the respective volume ratio of the lower volume fraction compound component to the higher volume fraction compound component, as specified by the compound producer. As the first piston  45  and the second piston  46  are tightly connected by one rod  47  ( FIG. 17 ), the stroke of the piston assembly  11  does not affect the dosing unit proportional volume ratio. 
     The second critical parameter of the dosing unit is its total capacity or the total volume of the two compound components fit into the total piston operating cavity  51  ( FIG. 18 ) and the total rod operating cavity  52  of the dosing unit when it is completely filled. In this position of the piston assembly  11 , the length of the stroke reserve L 1  is equal to the length L of the full working stroke of the piston assembly  11 . The minimum length L of the full stroke ( FIG. 19 ) of the piston assembly  11  is calculated so that at full discharge of the piston and rod operating cavities  51  and  52  of the dosing unit, at the end of the impregnation stage (at L 2 =L), a partial discharge of the compound from the annular space  19  through a sealed inlet  20  ( FIG. 5 ) can be at least reached to evacuate air from the annular space  19  in the area of the welded joint  15 . In order to calculate the minimum full stroke length of the piston assembly  11 , the compound consumption required to fill the cavities and channels of the device at the beginning of the technological cycle of impregnation of the annular space  19  in the area of the welded joint  15  must also be taken into account. Moreover, it is necessary to consider the consumption of the compound that is forcibly removed at the initial stage of impregnation due to its low-quality components, due to the inertia of the static mixer output to a steady mode of the compound components mixing. 
     When the compound components dosing unit is produced with a length L of the full stroke of the piston assembly  11  less than the minimum allowable value, the quality isolation of the welded joint  15  of the pipeline  14  cannot be guaranteed. At the same time, the extremely excessive length L of the full stroke of the piston assembly  11  leads to an increase in weight and size properties of the dosing unit and the device in general. 
     To conduct an experiment, we chose a two-component polyurethane produced by Covestro, which consists of two components:
         1) Isocyanate B9 M10 with a mixing volume fraction 38.5;   2) Polyol CG9 9008 75 MF with a mixing volume fraction 100.       

     The inner diameter of the sealing unit  10  casing  22  is taken as 90 mm. The diameter of pistons  45 ,  46  was taken equal to the inner diameter of the casing  22 . The rod diameter  47  was computed according to the required rod-to-piston operating area ratio equal to 0.385 (or 38.5:100). The rod  47  diameter was taken as 70.58 mm. The rod seals were fabricated according to a custom order. Tolerable inaccuracy in dosing the compound components must not exceed 1%. The estimated dosing inaccuracy for the suggested device is less than 0.0012%. The actual dosing inaccuracy for the suggested device depends only on the manufacturing accuracy of the piston assembly  11  and was 0.066%, which is much less than the permissible value. The length L of the full operating stroke of the test sample is taken to be 85 mm. The full capacity of the dosing unit is 0,748 liters. 
       FIG. 20  shows the pneumatic automation unit  13  assembly/disassembly diagram. The pneumatic automation unit  13  comprises a pneumatic valve island  56 , e.g. type 10CPV by Festo, O-Ring seals  57  for the operating channels of the pneumatic valve island  56 , casing  58 , two reverse pneumatic valves  59 , e.g. H-QS-4 type by Festo, and seals  60  for the casing  58 . The sensor  42  indicating the position of the piston assembly  11  with the pressure tube  55  is mounted on the end part of the casing  58 . The design of the pneumatic automation unit  13  is explained by the images in  FIG. 21  and  FIG. 22 . There are annular grooves that accommodate O-ring seals  57  on the surface of the casing  58  horizontal platform. Sealing of the operating channels of the pneumatic valve island  56  is provided by fastening the pneumatic valve island  56  with mounting bolts to the horizontal platform with the installed O-ring seals  57 . Vertical channels  61  are drilled coaxially to the annular grooves in the casing  58 ; these channels are connected to horizontal channels  62  integrated in the casing  58 , which pass through the bottom of the casing  58  to a flange  63 . The flange  63  ( FIG. 22 ) has blind openings  64  extending to its surface that faces toward the casing  58  ( FIG. 20 ). The openings  64  are located on a circle with a diameter corresponding to the diameter of a circle of location of the channels  27  ( FIG. 9 ) on the casing  22  of the sealing unit  10 . The spacing between the openings  64  on the flange  63  of the pneumatic automation unit  13  corresponds to the spacing of openings  27  ( FIG. 9 ) on the casing  22  of the sealing unit  10 . Channels  65  ( FIG. 22 ) made in the flange  63  connect the horizontal channels  62  with the blind openings  64 . When the pneumatic automation unit  13  is mounted in the annular grooves  28  ( FIG. 9 ), sealing rings are mounted in the end face of the casing  22  of the sealing unit  10 . The pneumatic automation unit  13  is inserted into the cavity of the casing  22  of the sealing unit  10  and pushed to the stop. The openings  64  ( FIG. 22 ) on the casing  58  of the pneumatic automation unit  13  are aligned with the channels  27  ( FIG. 9 ) on the casing  22  of the sealing unit  10 . Then the flange  63  ( FIG. 22 ) is fastened to the casing  22  of the sealing unit  10  with bolts at the location of mounting openings  30  ( FIG. 9 ) on the casing  58  of the pneumatic automation unit  13 .  FIG. 23  represents a section of the suggested device, along a plane passing through axes of the channels  62 . So, operating channels of the pneumatic valve island  56  ( FIG. 21 ) are first taken out on the flange  63  ( FIG. 23 ) of the pneumatic automation unit  13 , then they are connected to a flange of the compound feeding unit  12  through the channels  27  in the casing  22  of the sealing unit  10 . 
     The compound feeding unit  12  ( FIG. 6 ), as one of the main components of the suggested device, is represented in  FIG. 24 . The compound feeding unit  12  comprises a static mixer with a valve assembly  66  at the inlet ( FIG. 24 ); washing fluid reservoir, preferably as a hydraulic accumulator  67 ; a flow control unit  68  at the static mixer outlet; and three quick-release couplings  69 ,  70  and  71 . The diagram for the assembly/disassembly of the compound feeding unit  12  is shown in  FIG. 25 . 
     The design and composition of the static mixer with a valve assembly  66  at the inlet is illustrated by the diagram for its assembly/disassembly ( FIG. 26 ). The static mixer with inlet valve assembly  66  comprises: an integral static mixer  72  comprising a set of separate mixing elements made of anti-adhesion material (e.g., fluoroplastic), three spool valves  73 ,  74  and  75 , a casing  76 , a cover  77  and a flange  78  integrated with the casing  76 . Separate mixing elements  79  are made according to the technical solution described in U.S. Pat. No. 3,583,678. The mixing elements  79  are assembled in the cavity of the casing  76  and pressed by the cover  77 . The mixing elements  79  are firmly connected to each other and to the walls of the casing  76 . When assembled, the built-in static mixer  72  has no dead spots. The static mixer  72  is easy to disassemble and rinse. 
     An axonometric view of a mixing element  79  is presented in  FIG. 27 . Each mixing element  79  has four through openings  80 . The suggested device is designed to enable highly efficient control over static mixing intensity of the compound components and to obtain the highest quality of the mixture. The control over the mixing intensity of the compound is provided by varying the number of individual mixing elements  79  in the set of the integrated static mixer  72 . As the number of the mixing elements  79  increases, the number of streams to be mixed increases exponentially. As flows pass through each mixing element  79 , each flow is divided into 4 streams. Two incoming jets of the compound passed through the first mixing element  79  are divided into eight streams; those passed through the second element  79  are divided into 32 streams; those passed through the third element  79  are divided into 128 streams; those passed through the fourth element are divided into 512 streams; those passed through 16 elements are divided into more than 8.5 billion finest streams. The high efficiency of the built-in static mixer  72  is guaranteed in a wide range of viscosities of the used compounds. 
       FIG. 28  illustrates the design of the integral spool valves  73 ,  74  and  75  used in the suggested device with pneumatic drives in closed position. Each valve  73 ,  74  and  75  has a spool  81 ,  82 ,  83  firmly connected to a piston  84 ,  85 ,  86 . The valves  73 ,  74  and  75  are equipped respectively with supercharge cavities  87 ,  88  and  89  and discharge cavities  90 ,  91  and  92 . The pneumatic drive of each valve  73 ,  74  and  75  has a cavity above the piston and below the piston, respectively. The spool valves  73 ,  74  and  75 , along with a set of mixing elements  79  of the static mixer  72  ( FIG. 26 ) are combined in one common casing  76  and closed by one common cover  77 . In  FIG. 29  a cross-section of one of the spool valves  73 ,  74  and  75  is shown in the open position. 
     The mutual positioning in the common casing of the integral valves  73 ,  74  and  75  and the set of individual mixing elements  79  of the integral static mixer  72  is clarified by the axonometric view of the static mixer  72  with the inlet valve assembly  66  with the cover taken off, shown in  FIG. 30 . 
     The design of the casing  76  of the static mixer  72  with the inlet valve assembly  66  is clarified by its axonometric view with a cutout shown in  FIG. 31 ; along its periphery, nine longitudinal channels  93 - 101  are made in the casing  76 . On the end face of the flange  78 , the longitudinal channels  93 - 101  extend outward. Therefore, a channel  102  in the flange  78  of the casing  76  is connected at one end to the longitudinal channel  99  and at the other end to a channel  103  extending to the outer surface. There is a special cavity along the axis of the casing  76  that accommodate the individual mixing elements  79  of the integrated static mixer  72 . 
       FIG. 32  shows an axonometric view of the static mixer  72  with an inlet valve assembly  66  with a cutout on a plane passing through longitudinal axes of channels  93  and  94 , and through a plane passing through axes of radial channels connected to the cavities above pistons ( FIG. 28  and  FIG. 29 ) of the pneumatic drive valves  73 ,  74 ,  75 . The three longitudinal channels  93 ,  94  and  95  of the casing  76  are connected to the cavities of the pneumatic valve drives  73 ,  74  and  75  which are located above the pistons. In the flange  78  of the casing  76 , the longitudinal channel  93  extends to the outer surface. The longitudinal channels  93  and  94  in the flange  78  of the casing  76  are interconnected with a hidden channel  104 . The longitudinal channel  95  and a through opening  105  in the flange  78  of the casing  76  are connected by a hidden channel  106 . 
       FIG. 33  shows an axonometric view of the static mixer  72  with an inlet valve assembly  66  with a complex cutout on a plane passing through longitudinal axes of channels  96  and  97 , and through a plane passing through axes of radial channels connected to the cavities below pistons ( FIG. 28  and  FIG. 29 ) and to pneumatic drives of the integrated valves  73 ,  74 , and  75 . The three longitudinal channels  96 ,  97  and  98  of the casing  76  are connected to the cavities of the pneumatic valve drives  73 ,  74  and  75  below the pistons. In the flange  78  of the casing  76 , the longitudinal channels  96  and  97  are connected to each other with a channel  107 . 
       FIG. 34  shows an axonometric view of the static mixer  72  with the inlet valve assembly  66  with a cutout on a horizontal plane passing through an axis of channel  99 , and through a plane passing through axes of arc-shaped channels connected to the supercharge cavities  87 ,  88 ,  89  ( FIG. 28 ,  FIG. 29 ) of valves  73 ,  74  and  75 . The longitudinal channel  99  is connected to the supercharge cavity  87  of the integrated valve  73 . On the flange side  78  of the casing  76 , the channel  99  is connected through an inner channel to the channel  103  extending to the surface. The longitudinal channel  101  is connected to the supercharge cavity  88  of the valve  74 . The longitudinal channel  100  is connected to the supercharge cavity  89  of the valve  75 . 
       FIG. 35  shows a section of the static mixer  72  with an inlet valve assembly  66  plane passing through the axes of the valves  73  and  74  (in the open position). The through channel  43  in the cover  77  of the casing  76  is connected to the supercharge cavity  87  of the valve  73 . At the same time, the through channel  43  is connected through the supercharge cavity  87  of the valve  73  to the longitudinal channel  99  ( FIG. 34 ) in the casing  76 . 
     The discharge cavity  91  of the valve  74  is connected by a radial channel  108  to a channel  109  that enters the integrated static mixer  72  adjacent to the cover  77 . 
     The discharge cavity  90  of the valve  73  is connected by a radial channel  110  to a channel  111  that enters the static mixer  72  adjacent to the cover  77 . A channel  112  comes out into the upper part of the discharge cavity  91  of the valve  74 . A channel  113  comes out into the upper part of the discharge cavity  90  of the valve  73 . In the flange  78  of the casing  76 , an outlet opening  114  is located. 
       FIG. 36  shows an axonometric view of the static mixer  72  with an inlet valve assembly  66  with a cutout on a horizontal plane passing through axes of the valves  73  and  74  and on a plane passing through axes of the channels  112  and  113  ( FIG. 35 ). The discharge cavities  91 ,  92  of the valves  74  and  75  are interconnected by the channel  112  ( FIG. 36 ). The discharge cavities  90 ,  92  of the valves  73  and  75  are interconnected by the channel  113 . 
     Axonometric view of the static mixer  72  with the inlet valve assembly  66  with a cutout on the plane that passes through axes of the channels  95  and  101 , and a plane perpendicular to said plane, passes through the channels  102  and  107  in the flange  78 , presented in  FIG. 37 , clarifies the design of channels in the flange  78  of the casing  76 . As it was noted above, the longitudinal channels  93  and  94  are interconnected and have one common outlet on the outer surface of the flange  78  of the casing  76 . The longitudinal channels  96  and  97  are also interconnected and have one common outlet on the outer surface of the flange  78  of the casing  76 . The other five longitudinal channels  95 ,  98 ,  99 ,  101  and  100  that extend peripherally around the casing  76  are isolated from each other and have separate outlets on the outer surface of the flange  78  of the casing  76 . 
     The hydraulic accumulator  67  ( FIGS. 24, 25 ) is integrated into the compound feeding unit  12 .  FIG. 38  shows the design of the hydraulic accumulator  67 . The main components of the suggested device that are located in the area of the hydraulic accumulator  67  at the same time constitute its integral part. The movable operating unit of the hydraulic accumulator  67  is a cylindrical diaphragm  115  ( FIG. 38 ). Both end areas of the diaphragm  115  are equipped with special reinforced profiles which provide easy fixation and sealing of both circuits of the hydraulic accumulator  67 . The central casing part of the hydraulic accumulator  67  is the casing  76  of the static mixer  72  with flow control valve assembly  66  at the inlet. Two special flanges  78  and  116  are profiled on the casing  76 . The diaphragm  115  is placed coaxially to the casing  76 . Reinforced profiles on the ends of the diaphragm  115  are mounted on the outer profiled surfaces of the flanges  78  and  116  of the casing  76 . The diaphragm  115  and casing  76  with flanges  78  and  116  constitute the inner circuit of the hydraulic accumulator  67 . The ends of the diaphragm  115  are secured by special rings  117  and  118  with special profiles on the inner surface matching the profile of the end sections of the diaphragm  115 . The ring  117  is bolted to the side surface of the reinforced part of the casing  76 . The ring  118  is also bolted to the adjacent side surface of the flow control assembly  68  at the static mixer  72  outlet. When the membrane  115  is fastened, its thickened profiles are compressed on the end sections. This ensures that the connections are sealed. The diaphragm  115 , rings  117  and  118 , and the casing  22  of the sealing unit  10  constitute the outer circuit of the hydraulic accumulator. There are grooves on the outer surface of the rings  117  and  118  which are used to fit O-type sealing rings  119 . Tightness of the inner circuit is provided entirely by tightness of connections between the diaphragm  115  and flanges  78  and  116  of the casing  76 . Tightness of the outer circuit is achieved by sealing connections between the diaphragm  115  and the rings  117  and  118 , and the two O-rings  119  that seal a gap between the casing  22  of the sealing unit  10  and the rings  117 ,  118 . 
     The hydraulic accumulator  67  cavity created by an internal sealed circuit is intended to deliver washing fluid to the suggested device. The cavity created by the outer sealed circuit is designed to inject compressed air into this cavity and thereby create and maintain the pressure of the washing fluid in the inner circuit of the hydraulic accumulator  67  at a required level. 
     The compressed air from the pneumatic automation unit  13  is fed to the external circuit of the hydraulic accumulator  67  by one of the longitudinal channels  27  ( FIG. 39 ) in the casing  22  of the sealing unit  10 . The ring  118  ( FIG. 40 ) has a through opening  120  that extends into the outer circuit of the hydraulic accumulator  67 . The opening  120  is coupled to one of the longitudinal channels  27  ( FIG. 40 ) in the casing  22  of the sealing assembly  10  through a channel  121  in the flow control assembly  68  at the outlet of the static mixer  72 . The through opening  105  ( FIG. 41 ) connected to the longitudinal channel  100  ( FIG. 37 ) of the casing  76  of the static mixer  72  with the inlet valve assembly  66  goes out into the inner circuit of the hydraulic accumulator  67 . The channel  100  ( FIG. 41 ) is connected to the supercharge cavity  89  of the valve  75 . 
     The suggested device is filled with two components of the compound and washing fluid through quick-release couplings  69 ,  70  and  71  ( FIG. 24, 25 ). The models of quick-release couplings FEM-121-2 FB and FEM-122-2 FB produced by Parker equipped with return valves preventing leakage during connection, impregnation, and disconnection after refueling are used. 
     The quick-release coupling  71  is designed to fill the rod operating cavity  52  of the compound components dosing unit.  FIG. 42  shows an axonometric view of the suggested device with a complex cutout on the planes that pass through the axes of the channels that connect the quick-release coupling  71  with the rod operating cavity  52  and static mixer  72  with the valve assembly  66  (rod and pistons are not shown in  FIG. 42 ). The quick-release coupling  71  is connected to the rod operating cavity  52  of the dosing unit by means of channels  122 ,  36  and  37 . The quick-release coupling  71  is also connected to the longitudinal channel  101 , which is connected to the supercharge cavity  88  of the valve  74  ( FIG. 34 ). 
     The quick-release coupling  70  is used to fill the inner circuit cavity of the hydraulic accumulator  67  with washing fluid.  FIG. 43  shows an axonometric view of a compound feeding unit  12  with a complex cutout along planes that pass through axes of channels that connect the inner circuit of the hydraulic accumulator  67  to the channel  100  and the quick-release coupling  70 . The quick-release coupling  70  ( FIG. 43 ) is connected by means of a channel  123  to the through opening  105  that goes into the inner circuit of the hydraulic accumulator  67 . In turn, the opening  105  is connected to the channel  100 , which is coupled to the supercharge cavity  89  of the valve  75  ( FIG. 34 ). 
     The quick-release coupling  69  is designed to fill the piston operating cavity  51  of the compound components dosing unit.  FIG. 44  shows an axonometric view of a compound feeding unit  12  fragment with a complex cutout along the channel planes from quick-release coupling  69  to channel  103 . The quick-release coupling  69  is connected through channels  124  and  125  to the channel  103 . In turn, the channel  103  ( FIG. 34 ) is connected through the channel  99  to the supercharge cavity  87  of the valve  73 , which communicates through the opening  43  ( FIGS. 35, 14, 19 ) with the piston operating cavity  51  of the dosing unit. This way, the quick-release coupling  69  is connected to the piston operating cavity  51  of the integrated dosing unit. 
     At the outlet of the static mixer  72 , the flow of the mixed two-component compound must be controlled. In this case, regardless of the actual position of the piston assembly  11  of the dosing unit and static mixer  72  relatively to the position of the impregnated annular space  19  in the area of the pipeline welded joint  15 , it is extremely important to control the flow of the compound in the immediate vicinity of the insulated welded joint  15 . Failure to observe this condition makes it impossible to wash the compound supply system in the cavity of the annular space  19  in time and results in compound polymerization both in its supply hoses and in the equipment itself thus rendering them inoperable. 
     When the valves  73  and  74  ( FIG. 35 ) are opened at the inlet to the static mixer  72 , both components of the compound first fill the channels in the space from the discharge cavities  90  and  91  of the open valves  73  and  74  to the static mixer  72 . Due to the unequal ratio of volumetric doses of the components, the component with the higher mixing volume ratio flows first into the static mixer  72 . Therefore, the first dose of mixed material has a significant deviation from the required proportional ratio of the compound components. When this low-quality material enters the annular space  19  in the area of the welded joint  15 , the volume of the compound with a composition that has an unacceptable deviation from the required ratio of its components dosage slightly increases due to the movement of streams in the cavity. This significantly reduces quality of the welded joint insulation. At the start of the passage of the compound components through the built-in static mixer  72 , the mixing process instability can be observed. Reaching the steady state of the static mixer  72  is an inertial process. Moreover, as a rule, residual wash fluid remains in the static mixer  72  and in the channels for feeding the compound into the annular space  19  in the area of the welded joint  15 . The first dose of the compound cleans the cavities and channels all the way from the discharge cavities  90  and  91  of the valves  73  and  74  at the inlet to the static mixer  72  up to the cavity of the annular space  19  in the area of the welded joint  15 . At the same time, the first dose of the compound passed through is saturated with foreign fluids. For these reasons, the first dose of compound should be directed through a different channel bypassing the cavity of the annular space  19  in the area of the welded joint  15 . Once the poor-quality compound is removed, the flow of material must be redirected into the cavity of the annular space  19  in the area of the welded joint  15 . Once the process of filling the cavity of the annular space  19  is over, the channels of compound feeding and air evacuation must be shut off. Meanwhile, the cavities and channels of the static mixer  72  and the channels for feeding the material into the cavity of the annular space  19  in the area of the welded joint  15  get filled with high-quality compound. Failure to remove the remaining compound from the static mixer  72  and channels in time inevitably leads to its polymerization and failure of the suggested device. In order to constantly keep the equipment in working order, the static mixer  72  and the channels for feeding the compound in the cavity of the annular space  19  must be washed at the end of the impregnation process. This requires a supply of washing fluid at the inlet to the static mixer  72  instead of the compound components. And the washing fluid and products of system flushing should be drained into a special circuit to be disposed of before reaching the cavity of the annular space  19  in the area of the welded joint  15 . 
     The full operating volume of the compound components dosing unit must be greater than the volume of the annular space  19  in the area of the insulated welded joint  15  by at least twice the working volume of static mixer  72  and twice the volume of the compound feeding channels from the static mixer  72  to the annular space  19 . 
     Compliance with this condition enables the initial filling of the cavities and channels of the static mixer  72  and the channels of the compound feeding into the annular space  19  and removing the first batch of low-quality compound from the feed circuit. The amount of low-quality material removed must be at least equal to the volume of the compound that the static mixer  72  and the feed loop channels contain between the static mixer  72  and the annular space  19 . After the low-quality material is removed from the feeding circuit, the cavity of the annular space  19  is filled with a compound with the composition complying with the manufacturer&#39;s requirements. This guarantees the quality of the welded joint insulation. 
       FIG. 45  shows an axonometric view of the flow control assembly  68  at the outlet of the static mixer  72  from the side of the channel outlet on the flange  126  surface. On the surface of the flange  126  ( FIG. 45 ), there are channels  127 , intended for connection to the static mixer  72  with the valve assembly  66 ; a channel for supplying compressed air to the hydraulic accumulator  67  outer circuit; channels intended for coupling with the sealing unit  10 . The flow control assembly  68  at the outlet of the static mixer  72  includes: a nipple  128  that supplies compound to the annular space  19  in the area of the welded joint  15 ; a third pinch valve  129  to evacuate air from the annular space  19 ; a first pinch valve  130  to supply compound to the annular space  19 ; a nipple  131  ( FIG. 46 ) of the bypass circuit; and a second pinch valve  132  of a discharge circuit. 
     The pinch valves  129 ,  130  and  132  are equipped with pneumatic drives.  FIG. 47  shows a cross section of the flange  126  of the flow control assembly  68  at the static mixer  72  outlet on a plane passing through axes of channels connected to the cavities above and below the piston cavities of the pneumatic actuators of the pinch valves  129  and  130 . The channel  133  ( FIG. 47 ) is connected to the cavity of the valve  129  above the piston. The channel  134  is connected to the cavity of the valve  129  below the piston. The channel  135  is connected to the cavity of the valve  130  above the piston. The channel  136  is connected to the cavity of the valve  130  below the piston. 
     The channel  137  ( FIG. 48 ) connected to the channel extending to the surface of the flange  126  of the flow control assembly  68  extends into the cavity of the valve  132  below the piston. 
     The channel  138  ( FIG. 49 ) connected to the channel extending to the surface of the flange  126  of the flow control assembly  68  extends into the cavity of the valve  132  above the piston. 
     The design of the flow control assembly  68  is clarified in  FIG. 50 . A channel  139  ( FIG. 50 ) located in the center of the flow control assembly  68  at the outlet of the static mixer  72  on the side of the flange  126  has an annular groove to mount an O-ring and connect to the channel  114  ( FIG. 35 ) in the casing  76  of the static mixer  72  with the valve assembly  66  at the inlet. A channel  140  ( FIG. 50 ) connects the channel  139  to the inner opening of a nozzle  141 . There is an annular space between the outer surface of the nozzle  141  and the inner surface of the nipple  128  that connects channels  142  and  143  of a bypass circuit. Actuators of the pinch valves  129 ,  130  and  132  are rods  144 ,  145  and  146 , respectively, each has a specially profiled end face. A cover  147 ,  148  and  149  of each pinch valve  129 ,  130  and  132  has a special integrated stop. The rod  144 ,  145  and  146  of each pinch valve  129 ,  130  and  132  is driven by a piston  150 ,  151  and  152 , respectively. The image shown in  FIG. 51  illustrates passage of bypass circuit channels  153  and  154  that connect the channels  142 ,  143  to the channel of the nipple  131 .  FIG. 52  illustrates a sectional view of the flow control assembly  68  with the pinch valve  130  in the open position. An elastic tube  155  for feeding the compound that connects the nipple  128  to the sealed inlet is located between the rod  145  and the cover  148  of the pinch valve  130  with a stop.  FIG. 53  illustrates a sectional view of the flow control assembly  68  with the pinch valve  130  in the closed position. 
     The pinch valves  129  and  132  have similar design and are installed, respectively, on elastic tubes for evacuating gas out of the annular space  19  and for discharging the compound and washing fluid. 
       FIG. 54  shows the design of the vacuum trap  5  ( FIG. 2 ). The vacuum trap  5  includes a casing  156  that has a cylindrical shape. The internal cavity of the casing  156  is divided by a built-in partition into small and large chambers. The large chamber is covered by a cover  157  and the small chamber is covered by a cover  158 . The casing  156  and the covers  157 ,  158  constitute an airtight housing. The fittings  6  and  7  are installed in the cover  157 . The tubes  3  and  4 , respectively, are inserted into the inner cavity of the large chamber through the fittings  6  and  7 . The fitting  8  is installed in the cover  158 . The tube  9  is inserted into the small chamber cavity through the fitting  8 . There is a thin-walled shell  159  in the inner cavity of the large chamber placed coaxially to the casing  156 . The shell  159  is hung to the casing  156  on load cells  160  by means of swivel joints  161 . There is a reservoir in the inner cavity of the shell  159  directly on its surface that consists of a cylindrical body  162  and easily removable covers  163 ,  164 , made of anti-adhesion material, such as polyethylene. The tubes  3  and  4  are inserted into the reservoir cavity through two holes in the cover  163 . There is an opening  165  in the cover  164  that provides a connection of the cavity of the small chamber with the cavity of the large chamber and the cavity of the reservoir through the opening  166  in the partition of the casing  156 . The air filter  156  is installed in the cavity of the small chamber coaxially to the casing  167 . 
     The principal scheme of the suggested device equipped with a vacuum trap is shown in  FIG. 55 . The suggested device is equipped with a distributed microprocessor system (not shown in the diagrams and drawings). The distributed microprocessor system is based on the following microcontrollers: TM4C1294NCPDT by Texas Instruments and microsensors MEMS. 
     The above layout ( FIGS. 3, 4, 14 ) of the device  1  ( FIG. 1 ) is the most universal and suitable for inside insulation of the pipeline welded joint in the widest range of diameters. In this case, said layout is practically the only layout, which can be used in the device  1  designed for internal insulation of the pipeline welded joint with a diameter not exceeding 159 mm. This layout provides the most compact and tight placement of all the components and units of the device  1  in the inner cavity of the cylindrical casing  22  ( FIGS. 7 and 14 ) of the sealing unit  10  ( FIG. 3 ), while the cavity serves as the casing of the device  1 . This allows for the smallest possible dimensions of the device  1 . When using said layout, the minimum size of the device  1  is determined by the size of the used valves  73 ,  74 ,  75  ( FIG. 26 ) of the compound feeding unit  12  and the pneumatic valve island  56  ( FIG. 20 ) of the pneumatic automation unit  13 . The small-sized pneumatic valve island  56  (10 CPV by FESTO) and valves  73 ,  74 ,  75  of special design used in the device  1  for the pipeline welded joint insulation have a surplus flow capacity, many times greater than the capacity required. Therefore, designs of different sizes of devices  1  for the welded joint inner insulation intended for pipelines of different diameters can be used with the same sizes of the pneumatic valve island  56  ( FIG. 20 ) and valves ( 73 ,  74 ,  75 ). Thus, excess space is formed in the device  1  designed for the pipeline welded joint inner insulation with a diameter greater than 159 mm in the inner cavity of the casing  22  ( FIG. 14 ) in the area of the pneumatic automation unit  13  and compound feeding assembly  12 . Moreover, the larger the diameter of the pipeline device  1  is designed for, the larger the diameter of the casing  22  is used, the larger the volume is the internal cavity of the casing  22 , and more free space is formed in the cavity of the casing  22 . As the diameter of the casing  22  grows, the total capacity of the dosing unit increases accordingly. With the pipeline diameter increase the amount of compound needed to fill the cavity of the annular space  19  ( FIG. 5 ) increases as well. However, with the increase in the pipeline diameter, and accordingly, the casing  22  diameter, the rate of increase in the total volume of the dosing unit exceeds the rate of increase in the amount of compound required to fill the increasing volume of the annular space  19 . Due to the above, it is possible to significantly reduce the total volume of the dosing unit at the expense of reducing the total stroke L and/or diameter D of the pistons  45 ,  46  in the piston assembly ( FIGS. 17, 18, 19 ). 
     The free space in the inner cavity of the casing  22  makes it easy to change the layout of the device  1 . For example, the compound feeding unit  12  can be combined with the pneumatic automation unit  13 , or sequential placement of components along one axis can be avoided and the dosing unit, compound feeding unit  12  and pneumatic automation unit  13  can be arranged in three parallel axes offset radially from the device  1 , it will help reduce the length of the device  1  at least by half. However, with the reduction of the device  1 , the length of the elastic shell  18  ( FIG. 4 ) of the sealing unit  10  ( FIG. 3 ) also decreases. Excessive reduction in the length of the elastic shell  18  inevitably results in significant deterioration of the quality of the annular space  19  sealing of the welded joint  15  and deterioration of the operation ability of the device  1  sealing unit  10 . The most optimal length of the elastic shell  18  is the length of the protective bushing  16  by a factor of two or three. In this case, the elastic shell  18  with the minimum length can be used to insulate the pipeline welded joints that have a high quality of the inner surface. It is highly advisable to use the device  1  with a longer elastic shell  18  on pipelines with unstable or poor quality of the inner surface. Compliance with these recommendations prevents the deterioration of the sealing unit  10  of the device  1 . In this way, the minimum permissible length of the device  1  is mainly determined by the length of the elastic shell  18  of the sealing unit  10 . However, reduction of the device  1  length by changing its layout can only be possible if the condition of minimum/optimal length of the elastic shell  18  is observed. 
     It is experimentally established that the option of the device  1  layout described above and shown in  FIG. 14 , has the most significant advantages. At the same time, the device  1  designed for internal insulation of the pipeline welded joints with a diameter over 159 mm allows to integrate additional components and/or devices (compressed air cylinder; air reducer; mini compressor; built-in vacuum pump; vacuum trap, etc.) into the casing of the pneumatic automation unit  13  and/or into the casing of the compound feeding unit  12 . 
     So, the layout of the device  1  presented above ( FIG. 14 ) is not the only possible, but also the most universal and preferable for almost all diameters of the pipeline. With the increase in the device  1  diameter, the preferred layout significantly increases the device functionality. The multifunctionality of the main units  10 ,  12  and the unit  13  ( FIG. 3 ) results in a significant reduction in the number of parts and detachable connections in the device  1 , which significantly increases the reliability of the equipment and reduces its weight and dimensions. 
     The inner insulation of the pipeline welded joint  15  was performed in two options:
         1) by means of the proposed device equipped with a vacuum trap ( FIG. 2 );   2) by means of the proposed device without a vacuum trap ( FIG. 1 ).       

     The inner welded joint  15  was insulated in both options on the pipeline with an outer diameter of 159 mm and a wall thickness of 6 mm. Thin-walled cylindrical protective bushings  16  of stainless steel 304 with an outside diameter of 141 mm and a wall thickness of 0.55 mm were used for insulation. The length of the protective bushings was 180 mm. 
     The two-component hydrolysis-resistant polyurethane system cured at room temperature was used as a compound: Polyol CG9 9008 75 MF+Isocyanate B9 M10 by Covestro. Mixing ratio by volume was 38.5:100. The lifetime of the compound after mixing its components at 23 degrees Celsius is 7 . . . 10 minutes. A solvent was used as a washing liquid. 
     The device used for the internal insulation of the welded joint had an integrated dosing unit of the two-component compound with the following features: piston  45  and  46  diameter—90 mm; rod  47  diameter—70.58 mm; ratio of rod working area to piston working area 38.5:100; full working stroke length of piston assembly  11 —85 mm; full volume of the dosing unit—0.748 liters, volume of the hydraulic accumulator  67 —0.525 liters. 
     The inner insulation of the pipeline welded joint  15  was performed at an ambient temperature of minus 26 degrees Celsius. The temperature of the compound components inside the dosing unit and of the washing fluid inside the hydraulic accumulator  67  was maintained between plus 23 and 25 degrees Celsius during the entire process of the pipeline welded joint  15  insulation. The suggested device was thermoregulated by means of a film electric heater  23  ( FIG. 58 ) of 2.8 kW power. Heating and operation of the suggested device inside the pipeline  14  cavity was controlled by the built-in distributed microprocessor system based on the program uploaded into the control system internal memory. Before initiating the inner insulation process, an electric band heater (not illustrated in the drawings) with an autonomous power supply and temperature controller was installed on the outside of the pipeline  14  at the joint to be insulated. The heating temperature was set to +30 degrees Celsius. The electric band heater was dismantled in 30 minutes after removing the suggested device from the pipeline  14  cavity. 
     The first option of the pipeline welded joint inner insulation with the use of the suggested device, equipped with a vacuum trap, was performed as follows. 
     Stage 1. Works on stage 1 involved service personnel. The suggested equipment was prepared for work on the welded joint  15  inner insulation. In the initial position of the device  1 , the valves  73 ,  74 ,  75  ( FIG. 55 ) were in the closed state. The valves  129 ,  130 ,  132  ( FIG. 55 ) were forced into the open state. New elastic tubes  3 ,  4  and  155  ( FIG. 56 ) were installed on the device  1  designed for operating in vacuum and withstanding operation at overpressure up to 10 bar at temperatures ranging from minus 40 to plus 40 degrees Celsius. The integrated dosing unit was filled using a mobile dosing unit (not shown in the diagram). Two hoses of the refueling device with appropriate quick couplings were connected to the quick-release couplings  69  and  71  ( FIG. 56, 55 ) of the suggested device  1 . CG9 9008 75 MF polyol hose was connected to the quick-release coupling  69 , and B9 M10 isocyanate hose was connected to the quick-release coupling  71 . The integrated quick couplings  69  and  71  prevent any other connection thereby eliminating the possibility of improper dispensing. Isocyanate and polyol were filled synchronously until the piston and rod cavities  51 ,  52 ,  53 ,  54  of the dosing unit were completely filled at 6 bar. As the dosing unit was being filled, the flow of polyol CG9 9008 75 MF through the quick-release coupling  69  flowed sequentially through channels  125  and  124  ( FIG. 44 ) in the flow control assembly  68  at the static mixer  72  outlet. The polyol flow was directed from the channel  124  to the channel  103  in the casing  76  ( FIGS. 31, 26 ) of static mixer  72  with valve assembly  66 . Then, the polyol flow passed through the channels  102  and  99  ( FIG. 31 ) in the casing  76 . Polyol passed through the channel  99  ( FIG. 34 ) into supercharge cavity  87  of the valve  73 . From the supercharge cavity  87  of the valve  73 , polyol was pumped through the channel  43  ( FIGS. 35, 14 ) into the piston operating cavity  51  ( FIG. 17 ) of the dosing unit. 
     B9 M10 isocyanate was fed through the quick-release coupling  71  ( FIG. 42 ) to the channel  122  constructed in the flow control assembly  68  at the static mixer  72  outlet. The flow of isocyanate from the channel  122  passed through the longitudinal channel  36  along the casing  22  of the sealing assembly  10  to the radial channel  37 . Isocyanate was pumped through the channel  37  into the rod operating cavity  52  ( FIG. 17 ) of the dosing unit. 
     The dosing unit cavity filling was monitored by two pressure sensors built into the dosing unit. In this case, the stabilization of the fluid pressure at 6 bar indicates the completion of the dosing unit filling process. After filling the dosing unit, the hoses were disconnected from the quick-release couplings  69  and  71  ( FIG. 56 ). 
     The hydraulic accumulator  67  ( FIG. 62 ) was filled with washing fluid through the quick-release coupling  70  ( FIG. 43 ). The washing fluid was fed into the hydraulic accumulator  67  inner cavity under overpressure of 2 bar. Before filling the hydraulic accumulator  67 , compressed air pressure was released from its external pneumatic cavity through the channels  27 ,  121 ,  120  ( FIG. 40 ). During the filling, the fed washing fluid consistently passed through the quick-release coupling  70 , channel  123  and then it was pumped through the channel  105  into the inner cavity of the hydraulic accumulator  67  ( FIGS. 43, 41 ). The filling of the inner cavity of the hydraulic accumulator  67  to its full capacity was monitored by the pressure reading in the filling device of the washing fluid at atmospheric pressure in the hydraulic accumulator  67  pneumatic cavity. The overall time to fill the dosing unit and hydraulic accumulator  67  was about 60 seconds. 
     The protective bushing  16  was mounted on the device. Installation of the protective bushing  16  is clarified in  FIG. 57 . The protective bushing  16  was inserted coaxially on top of the device and placed on the bedding  38  ( FIG. 11 ) of the elastic shell  18 , so that its side stoppers  39  were aligned with the ends of the protective bushing  16 . Compressed air was fed into the closed airtight circuit created by the casing  22  ( FIG. 7 ) and the elastic hose  17  of the sealing unit  10  ( FIG. 3 ) from the pneumatic valve island  56  ( FIG. 20 ) of the pneumatic automation unit  13  ( FIG. 3 ). The elastic sleeve  17  ( FIG. 58 ) inflated and expanded the elastic shell  18 . The bedding  38  ( FIG. 11 ) made contact with the protective bushing  16  ( FIG. 58 ). The side stoppers  39  ( FIG. 11 ) of the elastic shell  18  made contact with the ends of the protective bushing  16  ( FIG. 58 ) and fixed it. When the protective bushing  16  fixation on the elastic shell  18  ( FIG. 58 ) was completed, the supply of compressed air in a leak-tight circuit created by the casing  22  ( FIG. 7 ) and the elastic hose  17  of the sealing unit  10  ( FIG. 3 ) was completed, and the pressure was fixed with the pneumatic valve island  56  ( FIG. 20 ). Further expansion of the elastic sleeve  17  ( FIG. 58 ) and the elastic shell  18  was suspended. Preparation of the suggested device for work on the welded joint inner insulation has been completed. In total, it took 2 minutes and 50 seconds to prepare the device. 
     Stage 2. The suggested device was inserted into the inner cavity through the open end of the pipeline  14  ( FIG. 59 ) and placed in such a way that the welded joint  15  was centered on the protective bushing  16  fixed to the elastic casing  18 . In this case, between the outer surface of the elastic shell  18  and the inner surface of the pipeline  14 , there was an annular space of about 3 mm thick. In most cases, this size of space is considered the most optimal. Reduced clearance due to pipe ovality makes it slightly more difficult to transport the device through the pipeline inner cavity. A larger space leads to an unreasonable decrease in the cross-section of the pipeline after the welded joint insulation and higher material expenditures due to higher compound consumption. 
     Stage 3. As soon as the device positioning through the channel  35  ( FIG. 13 ) in a closed leak-tight circuit formed by the casing  22  ( FIG. 7 ) and the elastic hose  17  of the sealing unit  10  ( FIG. 3 ) was over, the supply of compressed air continued. As the pressure increases, the elastic hose  17  ( FIG. 60 ) inflated and expanded the elastic shell  18  to its stop on the inner surface of the pipeline  14 . A pressure of 10 bar was set in a sealed circuit between the casing  22  and the elastic hose  17 . The closed annular space  19  was formed between the protective bushing  16  and the inner surface of the pipeline  14 . On the side of the compound feeding unit  12 , the cavity of the annular space  19  was connected to the channels of airtight inlets  20  and  21 . 
     Stage 4. The annular space  19  in the welded joint  15  area ( FIGS. 55, 61, 62 ) and the compound feeding unit  12  ( FIG. 4 ) were vacuum treated. For this purpose, a vacuum pump (not illustrated in the drawings) connected to the tube  9  of the suggested device ( FIG. 2, 62 ) was used. In this case, the small vacuum pump was located in the pipeline inner cavity  14  directly near the vacuum trap  5 . The air was evacuated through the tube  9  from the inner cavity of the vacuum trap  5  ( FIG. 62 ). At the same time, the channels of the tube  3  ( FIG. 61, 62, 2 ), airtight inlet  20  and annular space  19  in the welded joint  15  area were vacuum treated. The air was pumped out of the airtight inlet  21  of the tube  155 , channels  140  and  139  ( FIG. 52 ) and the static mixer  72  ( FIGS. 61, 62 ) through the annular space  19  ( FIG. 61 ). The channels  108 - 113  and the discharge cavities  90 ,  91  and  92  of the valves  73 ,  74 ,  75  ( FIGS. 35 and 36 ) were vacuum treated through the static mixer  72 . In addition, the air was pumped out of the channels  142 ,  143  ( FIG. 50 ),  153 ,  154  ( FIG. 51 ), nipple  131  ( FIG. 51, 46 ) and the tube  4  ( FIG. 62 ). With the pinch valves  129 ,  130  and  132  ( FIG. 62 ) opened, all the vacuumed cavities and ducts communicate with each other. Therefore, air was evacuated with open pinch valves  129 ,  130  and  132 , which ensured a minimum duration of vacuuming. It took 45 seconds to evacuate the air to an absolute pressure of 2 mbar. 
     In the background mode, the device control system monitored the tightness of the annular space  19  ( FIG. 61 ) during air pumping in the real time mode. The tightness control was carried out alternately by three methods: estimation of instantaneous rate of pressure decrease in the process of vacuuming; estimation of ultimate level of vacuum pressure reached; rate of leakage after completion of air evacuation from the system. In total, it took 56 seconds to evacuate air from the annular space  19  and to check its tightness. 
     Stage 5. The pneumatic automation unit  13  was used to pump compressed air into the piston drive cavity  53  of the dosing unit through the channel  44  ( FIG. 15 ). In doing so, compressed air was pumped into the rod drive cavity  54  of the dosing unit from the piston drive cavity  53  through the channels  48  and  49  ( FIG. 16 ). The pressure in the drive cavities  53 ,  54  of the dosing unit has stabilized at 10 bar. The pressure has been also stabilized at 9.8 bar in the piston and rod operating cavities  53 ,  54  of the dosing unit. The pinch valve  130  ( FIG. 62 ) was shut off. In this case, the pinch valves  129  and  132  were opened. In the initial state, the valves  73  and  74  were closed. The compound components were pumped into the supercharge cavities  87  and  88  of the valves  73  and  74  ( FIG. 34 ) from the operating cavities  51 ,  52  of the dosing unit at a pressure of 9.8 bar. At the same time, polyol from the piston operating cavity  51  of the dosing unit put pressure directly into the supercharge cavity  87  of the valve  73  through the channel  43  ( FIG. 14, 19, 35, 63 ). Isocyanate located in the rod operating cavity  52  of the dosing unit put pressure in the supercharge cavity  88  of the valve  74  through the channels  37 ,  36 ,  122  ( FIG. 42 ) and  101  ( FIGS. 34, 42 ). The valves  73  and  74  were synchronously driven open ( FIG. 35 ). The compound components filled the discharge cavities  90  and  91  of the valves  73  and  74  and channels  108 ,  109 ,  110 ,  111  and flowed into the static mixer  72  from the supercharge cavities  87  and  88  ( FIG. 35, 63 ) of the valves  73  and  74 . The compound components simultaneously filled the channels  112 ,  113  and the discharge cavity  92  of the valve  75  ( FIGS. 35 and 36 ). Polyol and isocyanate were mixed in the static mixer  72  in a strictly dosed ratio. Mixed compound was fed from the static mixer  72  into the channels  114 ,  139  ( FIG. 63 ),  140  ( FIG. 53 ) and the tube  155  ( FIGS. 53, 62 ). Since the valve  130  was closed, the compound was not supplied into the annular space  19 . At the same time, the compound was pumped through the channels  142 ,  143 ,  153 ,  154  ( FIG. 50, 51 ) passed through the nipple  131  and flowed into the vacuum trap  5  ( FIG. 62 ) by the tube  4  through the open pinch valve  132 . The first batch of mixed compound was of poor quality. This was primarily caused by the fact that one of the compound components with a lower proportional mixing volume ratio filled the cavities at the inlet of the static mixer  72  and the mixer  72  itself with a certain delay, which resulted in a disturbance of the mixing proportions at the initial stage. That is why the first batch of compound was discarded to the vacuum trap  5 . The amount of first batch of compound to be removed was set by the device control system program. The amount of removed compound was controlled by a special device, a separate technical solution not disclosed within the framework of the present invention. After the first batch of poor-quality compound was removed, the valve  132  was shut off and the valve  130  was opened ( FIG. 61 ). Meanwhile, the compound passed through the feed-through plate  21  and filled the annular space  19  ( FIG. 61 ) through the tube  155  ( FIG. 61 ). As the annular space  19  was filled, the compound level in it increased. When the level in the annular space  19  raised to the level of the upper airtight inlet  20 , the compound started leaving the cavity through the airtight inlet  20  and the tube  3  ( FIG. 61 ) into the vacuum trap  5  ( FIG. 62 ). At the time of limiting the compound flow into the vacuum trap  5  through the upper airtight inlet  20 , the valve  129  was closed, and the valve  130  ( FIG. 61 ) remained open. In this case, the control system automatically reduced the pressure in the dosing unit down to 6 bar. The compound was pressurized for 20 seconds. This ensured guaranteed filling of all, including microscopic, gaps, voids and pores in the annular space  19 . After 20 seconds of exposure, the valves  130  ( FIG. 62 ), and valves  73  and  74  ( FIG. 63 ) were shut off. The compressed air pressure in the dosing unit was relieved by the pneumatic automation unit  13  ( FIG. 55 ). The annular space  19  filling process has been completed. In total, it took 28 seconds to fill the annular space  19  with compound, considering the operations of controlling its specific density and holding it under pressure. Given the compound removed into the vacuum trap  5 , its total volume spent on the inner insulation of the pipeline welded joint  15  was 0.272 liters. 
     Stage 6. The static mixer  72  and mixed compound supply channels in the cavity of the annular space  19  in the welded joint area  15  were flushed. Compressed air was pressurized into the cavity of the external sealed circuit of the hydraulic accumulator  67  through the channels  120  and  121  ( FIG. 40 ). The pressure in the hydraulic accumulator  67  was set to 10 bar. The valves  132  and  75  were opened ( FIG. 55 ). When the valve  75  ( FIG. 36 ) was opened, the washing fluid flowed in the discharge cavity  92  from the discharge cavity  89  of the valve  75  in the hydraulic accumulator  67  ( FIG. 29 ) under pressure. At the outlet of the discharge cavity  92  of the valve  75  ( FIG. 36 ), the washing fluid was divided into two streams. One stream of washing fluid passed through the channel  112  ( FIG. 36 ) to the discharge cavity  91  of the valve  74  and then through the channels  108 ,  109  ( FIG. 35 ) entered the integrated static mixer  72 . Another stream of washing fluid passed through the channel  113  ( FIG. 36 ) to the discharge cavity  90  of the valve  73  and then through the channels  110 ,  111  entered the static mixer  72 , where the two streams were combined. The stream of washing fluid passed all the way of the mixed compound from the static mixer  72  to the point of pinching the elastic tube  155  ( FIG. 53 ) by the valve  130  rod. With the valve  130  ( FIG. 53 ) closed, washing fluid passed along the bypass channels  142 ,  143 ,  153  ( FIG. 51 ) and  154  to the nipple  131  through the annular slot between the nipple  128  ( FIG. 50 ) and the nozzle  141 . With the valve  132  ( FIG. 62 ) open, mixed compound flowed into the cavity of the vacuum trap  5  through the tube  4 . The washing fluid flow rate was measured by weight method by means of load cells  160  and the control system. When the flow rate of the washing fluid reached 0.150 kg, the valve  75  was closed. The washing process has been completed. 
     Stage 7. Polymerization. After the process of filling the annular space  19  with compound in the welded joint  15  area, the suggested device was kept in the pipeline cavity for 10 minutes. 
     Stage 8. At the end of exposure, the sealed circuit formed by the casing  22  and the elastic hose  17  ( FIG. 55 ) was depressurized. The elastic shell  18  ( FIG. 55 ) shrunk and left the grip with the protective sleeve  16 . The gap was formed between the suggested device  1  ( FIG. 64 ) and the inner walls of the pipeline  14 , as well as between the device  1  and the protective sleeve  16 . The device  1  was removed from the cavity of the pipeline  14 . In this case, after the device  1  was removed from the cavity of the pipeline  14 , the welded joint  15  took the shape illustrated in  FIG. 65 . The welded joint  15  and adjacent sections of the pipeline  14  inner surface are tightly sealed by a continuous waterproof cylindrical shell of polymerized compound  168  and protective bushing  16 . 
     Stage 9. Works on stage 9 involved service personnel. Immediately after the device  1  was removed from the pipeline  14  cavity, the elastic tubes  3 ,  4  and  155  were dismantled from it ( FIG. 57 ). The airtight inlets  20  and  21  ( FIG. 61 ) were purged with compressed air. If the time between the start of the process of filling the annular space  19  with compound in the welded joint  15  area and purging the airtight inlets  20  and  21  exceeded twice the lifetime of the mixed compound, their internal channels were cleaned with a straight steel rod of 4 mm in diameter. After full polymerization, the channels of sealed inlets  20  and  21  can be cleared by drilling them with a drill of 4 mm diameter with an electric screwdriver, for example. The reservoir was removed from the vacuum trap  5 , cleaned and then the vacuum trap was reassembled. 
     The second option of the pipeline welded joint inner insulation with the use of the suggested device without a vacuum trap, was performed as follows. 
     Stage 1. The work was carried out as per stage 1 according to the first option. The difference was that the long tube  3  was connected directly to the vacuum pump with an in-line receiver, and the tube  4  was connected with one end to the airtight inlet  20  ( FIG. 4 ), and its second end was left free with an open internal channel. 
     Stage 2. The work was carried out in full accordance with stage 2 of the first option. 
     Stage 3. The work was carried out in full accordance with stage 3 of the first option. 
     Stage 4. The work was carried out in accordance with stage 4 of the first option. The difference was that the pinch valve  132  was closed before the vacuum pump was turned on. Moreover, the duration of work at this stage increased to 180 sec due to the use of the long tube  3  that has a small cross-section. 
     Stage 5. The work was carried out in accordance with stage 5 of the first option. The difference was as follows. At the beginning of the stage, the pinch valve  132  was closed. That is why when the compound was fed, its pressure in the channels of the device increased. The compound pressure was controlled by a pressure sensor with an integrated media separator in the channel  139  ( FIG. 52 , the pressure sensor is not illustrated in the drawing). As soon as the compound pressure stabilized at 9.8 bar, the valve  132  was opened. The first batch of mixed compound was of poor quality. This is primarily caused by the fact that one of the compound components with a lower proportional mixing volume ratio filled the cavities at the inlet of the static mixer  72  and the mixer  72  itself with a certain delay, which resulted in a disturbance of the mixing proportions at the initial stage. That is why the first batch of compound was discarded into the cavity of the pipeline  14 . The amount of first batch of compound to be removed was set by the device control system program. The amount of removed compound was controlled by a special device, a separate technical solution not disclosed within the framework of the present invention. After the first batch of poor-quality compound was removed, the valve  132  was shut off and the valve  130  was opened ( FIG. 61 ). Meanwhile, the compound passed through the airtight inlet  21  and filled the annular space  19  ( FIG. 61 ) through the tube  155  ( FIG. 61 ). As the annular space  19  was filled, the compound level in it increased. When the level in the annular space  19  rose by about 80 percent of the volume of the annular space  19 , the valve  129  was shut off. Monitoring of the level of filling the annular space  19  ( FIG. 61 ) was carried out by a special device, a separate technical solution not disclosed within the framework of the present invention. When the moment of filling the annular space  19  to 80%, the valve  129  was closed, while the valve  130  ( FIG. 61 ) remained open. In this case, the control system automatically reduced the pressure in the dosing unit down to 6 bar. The process of filling the annular space  19  cavity continued. The moment when the annular space  19  is filled was monitored by the compound pressure in the channel  139  ( FIG. 52 ). Once the pressure was stabilized, the cavity of the annular space  19  was pressurized for twenty seconds ( FIG. 61 ). This ensured guaranteed filling of all, including microscopic, voids and pores in the annular space  19 . After 20 seconds of exposure, the valves  130  ( FIG. 61 ), and valves  73  and  74  ( FIG. 63 ) were shut off. The compressed air pressure in the dosing unit was relieved by the pneumatic automation unit  13  ( FIG. 55 ). The annular space  19  filling process has been completed. In total, it took 30 seconds to fill the annular space  19  with compound and expose it under pressure. The total volume of compound consumed for the pipeline welded joint inner insulation was 0,312 liters. 
     Stage 6. The work was carried out in accordance with stage 6 of the first option. The difference was that the washing liquid was removed directly into the pipeline cavity through the tube  4 . 
     Stage 7. The work was carried out in full accordance with stage 7 of the first option. 
     Stage 8. The work was carried out in full accordance with stage 8 of the first option. 
     Stage 9 The work was carried out in full accordance with stage 9 of the first option.