Pre-insulated pipes (hereinafter PPU pipes, steel PPU pipes) - rigid structure "pipe in pipe" - steel pipe, a layer of polyurethane foam insulation (PPU), protective sheath made of polyethylene (galvanized steel) with the UEC system.

The "central heating system" first appeared at the end of the 3rd and beginning of the 4th century BC. in the Roman Empire. This invention was successfully applied in Roman baths. Only in Rome, in the 4th century BC. there were more than 800 public baths. The heating systems of the baths had underground air pipelines.

In the 18th century, steam and water heating systems were first used in England and France. Initially, they were designed to heat greenhouses and greenhouses, and then the invention was successfully applied to heating buildings.

Over time, pipelines and pipes for heating have changed significantly - from wood, ceramic to steel, polypropylene pipe in polyurethane foam insulation.

External heating networks - Interesting Facts

• In the USA, Lockport in 1876 was first connected to the central heating system.
• In 1878, for the first time in Europe, in the Bonn hospital (Germany) and the hospital in Stockholm (Sweden), the central heating system was launched.
• By 1930, there were over 200 central heating systems in Europe, including the Vatican.
• For the first time in the USSR, a hot water pipe made of wood was installed in Smolensk in 1927. The riveted wooden water conduit was 60 mm thick, with an inner diameter of 100 mm and a length of 800 m. It was laid directly into the ground, without insulation, at a depth of 2 m. At an initial water temperature of 60 °, by the end of the pipeline the water temperature was 55. 5 º. The temperature drop was only 4.5 degrees.
• In Germany, in 1937, Otto Bayer obtained rigid polyurethane foam.
• In Germany in 1944 began industrial production polyurethane foams.
• Oil, energy crisis of 1974 and 1976 pushed the countries of Europe and the United States to create national energy programs that stimulate the rational use of energy resources in all areas of human activity.
• In the late 1950s and early 1960s. the first polyurethane foam pipes appeared, and Logstor ROR introduced a revolutionary insulation concept. Thus, the invention - "pipe in pipe" (PPU pipes) is widely used. The PPU pipe on many years of experience in use in the areas of hot water supply and heat supply, trunk oil and gas pipelines, condensate pipelines have proven their high technological and economic efficiency.
• The service life of polyurethane foam is 25-30 years, and PPU pipes - 40 years. The PPU pipe allows you to really increase the service time of the central heating station, significantly reduce heat losses and operating costs.
• In Denmark, at the beginning of the 90s, up to 75% of heating networks were replaced by a pipe in a PPU. Currently, the share of such pipes is 95-100%. As a result, with an increase in the number of connected consumers, the supplied capacity of heat supply sources decreased by 30%, tariffs for heat energy - by 10%.
• At present, only steel PPU and PPU pipes are used for laying the central heating station in Latvia, Lithuania, Estonia. polypropylene PU foam prefabricated.
• The demand for PPU pipes in Russia is growing every year. The length of the central heating station in Russia is about 250 thousand km.
• The PPU pipe is easier to install and operate than its steel counterpart. Pipes in polyurethane foam insulation are optimal for underground communications. In pipelines of the previous generation, up to 40% of heat was lost, in pipelines laid with the use of PPU pipes - only 4%.
• At present, the wear of heating systems has reached 60%. Specific damage to the heating network in the regions of the Russian Federation per 1 km of the network per year is 1.8-2.2, with a really permissible level of 0.3. Only 1.2% of the total length of the central heating station was replaced with steel pipes. In some regions of the Russian Federation, pipes in polyurethane foam have been replaced by 1.8%, if necessary, annual replacement of 5% of heat pipes.

SNiP "External heating networks" and PPU pipes

At present, the technical side of laying external heating networks is regulated by SNIP 41-02-2003 " Heating network". These rules laying of polyethylene pipelines heating networks (and other pipelines made of polymeric materials) are allowed at an operating vapor pressure of less than 0.07 MPa and a temperature of the coolant below 115 ° C at a pressure of less than 1.6 MPa.

As seen, polyethylene pipeline in heating networks has serious restrictions on the use and is not suitable for all installation conditions. Steel pipes in polyurethane foamoffered by NPO Stroypolimer do not have such restrictions and are suitable for equipment of heating systems of any configuration.

Technical requirements for heating networks

2.1. Technical requirements for heating networks

2.1.1. The laying of heating networks, the design of pipelines, thermal insulation, building structures of heating networks must comply with the requirements of the current SNiP.

2.1.2. On the territory of enterprises, as a rule, an above-ground laying of heating networks should be provided on detached supports and overpasses.

2.1.3. The slope of pipelines of heating networks must be at least 0.002, regardless of the direction of movement of the coolant and the method of laying heat pipes.

2.1.4. Construction of buildings, storage, planting of trees and perennial shrubs at a distance of less than 2 m from the projection onto the surface of the edge of the land in places where heat pipes are laid building structure heating network or channelless pipeline is prohibited.

2.1.5. The surface of the land along all routes of heating networks should be planned so as to prevent the ingress of surface water into the canals.

2.1.6. Materials, Pipes and fittings for heating networks should be used in accordance with the "Rules for the construction and safe operation of steam and hot water pipelines" of the Gosgortekhnadzor of Russia.

2.1.7. Elements (parts) of pipelines should be, as a rule, factory-made. It is prohibited to use parts made of pipes with an electrically welded spiral seam.

2.1.8. All connections of pipeline elements must be welded. The use of flanged connections is allowed for connecting pipelines to valves and equipment parts with flanges. Welding of flanged fittings directly to pipelines is allowed.

2.1.9. For all pipelines of heating networks, except for heat points and hot water supply networks, it is prohibited to use fittings for heating design:

from gray cast iron - in areas with an estimated outside air temperature below minus 10 ° С;

from ductile iron - in areas with a design temperature of the outside air below minus 30 ° C.

It is prohibited to use fittings made of gray cast iron on drainage and drainage devices.

2.1.10. On water heating networks with a diameter of 500 mm and more at a nominal pressure of 1.6 MPa (16 kgf / cm 2) and more, with a diameter of 300 mmand more at a nominal pressure of 2.5 MPa (25 kgf / cm 2) and more, on steam networks with a diameter of 200 mm or more at a nominal pressure of 1.6 MPa (16 kgf / cm 2) and more, valves and gates must be provided bypass pipelines (bypasses) with stop valves.

2.1.11. Gate valves and gates with a diameter of 500 mm and more must have an electric drive. When laying overhead heating networks, valves with electric drives must be installed indoors or enclosed in casings that protect the fittings and the electric drive from precipitation and exclude access to them by unauthorized persons.

2.1.12. Shut-off valves on heating networks should be installed:

on all pipelines of heating network outlets from a heat source, regardless of the parameters of the coolant and the diameters of the pipelines;

on pipelines of water heating networks with a diameter of 100 mm and more (sectioning valves) at a distance of no more than 1000 m from each other;

in the nodes of branches on pipelines with a diameter of 100 mm or more of water and steam heating networks, as well as to individual buildings.

2.1.13. At the lowest points of the pipelines of water heating networks and condensate pipelines, as well as sectioned sections, fittings with shut-off valves for draining water (drainage devices).

2.1.14. At the lowest points and in front of vertical, rises of steam heating networks, the drainage of steam pipelines should be constantly carried out. In the same places, as well as on straight linessections of steam pipelines through 400-500 m with a passing and after 200-300 m with an opposite slope, a device for starting drainage of steam pipelines should be installed.

2.1.15. Drainage of water from pipelines of water heating networks during underground laying should be carried out into waste wells with gravity drainage or into sewage systems with mobile pumps. The temperature of water discharged from wells should not exceed 40 ° C. When draining water in household sewerage a hydrolyzer must be installed on the gravity pipeline, and in case of a reverse flow of water, an additional shut-off (check) valve must be installed.

2.1.16. Condensate discharge from permanent steam line drains must be carried out into the condensate discharge system. It is allowed to drain it into the pressure condensate pipeline if the pressure in the drainage condensate pipeline is at least 0.1 MPa (1 kgf / cm 2) higher than in the pressure pipeline.

2.1.17. At the highest points of pipelines of heating networks, including at each sectional section, fittings with shut-off valves for air release (air vents) must be installed.

2.1.18. In heating networks, reliable compensation for thermal expansion of pipelines must be ensured.

2.1.19. To control the parameters of the coolant, the heating network must be equipped with selection devices for measuring:

temperatures in the supply and return pipelines in front of the sectioning valves and in the return pipe of branches with a diameter of 300 mm or more in front of the valve along the water flow;

water pressure in the supply and return pipelines before and after the sectioning valves and control devices, in the forward and return pipelines of the branches in front of the valve;

steam pressure in the branch pipelines in front of the valve.

2.1.20. In the chambers of heating networks, local indicating instrumentation must be installed to measure temperature and pressure in pipelines.

2.1.21. Heating pipelines, fittings, expansion joints, flange connections and pipe supports must be covered with thermal insulation in accordance with NTD.

It is allowed in the feasibility study to provide for laying without thermal insulation:

return pipelines of heating networks in the shops of enterprises, the heat flow of which is used for heating;

condensate networks for their joint laying with steam networks in non-passage channels.

Thermal insulation flange connections, fittings, pipeline sections subject to periodic inspection, as well as stuffing box, lens and bellows expansion joints must be removable. Heating networks laid outdoors, regardless of the type of installation, must be protected from moisture.

2.1.22. The outer surface of pipelines and metal structures of heating networks (beams, supports, masts, overpasses, etc.) must be protected with resistant anti-corrosion coatings.

Commissioning of heating networks after the completion of construction or major repairs without external corrosion-resistant coating of pipes and metal structures is prohibited.

2.1.23. When laying underground (in non-passable channels and channelless ones), pipelines of heating networks must be protected from external corrosion caused by the interaction of the metal of the pipelines with moist insulation or high corrosive soil activity, as well as stray currents. Protection must be provided in accordance with the current SNiP and "Instructions for the protection of heating networks from electrochemical corrosion". (Moscow: Stroyizdat, 1975).

2.1.24. When laying heating networks below the standing level groundwater it is necessary to arrange associated drainage with a pipe slope of at least 0.003, Water drainage from the associated drainage system should be provided by gravity or by pumping out by pumps into the rain sewer, reservoirs or ravines in agreement with the environmental authorities. The discharge of these waters into absorption wells or onto the surface of the earth is prohibited.

2.1.25. Equipment elements, fittings and devices for thermal control, remote control of underground heat pipelines,subject to periodic inspection and maintenance, should be placed in special chambers or basements accessible to service personnel.

2.1.26. The overall dimensions of chambers, tunnels, channels, the number of chamber hatches, the distance between the chambers of the tunnels must comply with the requirements of SNiP and the rules of Gosgortekhnadzor of Russia.

2.1.27. Places of installation of electrical equipment (pumping stations, heating points, tunnels, chambers), as well as places of installation of electrically driven valves, regulators and instrumentation must have electric lighting that complies with the "Rules for Electrical Installations".