Overhead laying of pipelines. Heating network structures Installation of heating networks, pipe laying

Pipelines Heat networks can be laid on the ground, in the ground and above the ground. With any method of pipeline installation, it is necessary to ensure the greatest reliability of the heat supply system at the lowest capital and operating costs.

Capital expenditures are determined by the cost of construction and installation work and the costs of equipment and materials for laying the pipeline. IN operational include the costs of servicing and maintaining pipelines, as well as costs associated with heat loss in pipelines and electricity consumption along the entire route. Capital costs are determined mainly by the cost of equipment and materials, and operating costs are determined mainly by the cost of heat, electricity and repairs.

The main types of pipeline laying are underground And aboveground. Underground pipeline installation is the most common. It is divided into laying pipelines directly in the ground (channelless) and in channels. When laid above ground, pipelines can be located on the ground or above the ground at such a level that they do not interfere with the movement of traffic. Overhead gaskets are used on suburban highways when crossing ravines, rivers, railway tracks and other structures.

Overhead gaskets pipelines in channels or trays located on the surface of the earth or partially buried, are used, as a rule, in areas with permafrost soils.

The method of installation of pipelines depends on the local conditions of the facility - purpose, aesthetic requirements, the presence of complex intersections with structures and communications, soil category - and should be taken on the basis of technical and economic calculations possible options. Minimal capital costs are required for the installation of a heating main using underground pipe laying without insulation and channels. But significant losses of thermal energy, especially in wet soils, lead to significant additional costs and premature failure of pipelines. In order to ensure reliable operation of heat pipelines, it is necessary to apply mechanical and thermal protection.

Mechanical protection pipes when installing pipes underground can be provided by installing channels, and thermal protection can be achieved by using thermal insulation applied directly to the outer surface of the pipelines. Insulating pipes and laying them in channels increases the initial cost of the heating main, but quickly pays off during operation by increasing operational reliability and reducing heat losses.

Underground laying of pipelines.

When installing heating pipelines underground, two methods can be used:

1. Direct laying of pipes in the ground (channelless).
2. Laying pipes in channels (channel).

Laying pipelines in channels.

In order to protect the heat pipeline from external influences, and to ensure free thermal elongation of the pipes, channels are designed. Depending on the number of heat pipes laid in one direction, non-through, semi-through or through channels are used.

To secure the pipeline, as well as ensure free movement during thermal expansion, the pipes are laid on supports. To ensure the outflow of water, the trays are laid with a slope of at least 0.002. Water from the lower points of the trays is removed by gravity into the drainage system or from special pits using a pump it is pumped into the sewer system.

In addition to the longitudinal slope of the trays, the floors must also have a transverse slope of about 1-2% to remove flood and atmospheric moisture. At high level groundwater The outer surface of the walls, ceiling and bottom of the channel is covered with waterproofing.

The depth of laying trays is taken from the condition of a minimum volume of excavation work and uniform distribution of concentrated loads on the floor during vehicle traffic. The soil layer above the canal should be about 0.8-1.2 m and no less. 0.6 m in places where vehicle traffic is prohibited.

Impassable channels are used for a large number of pipes of small diameter, as well as two-pipe laying for all diameters. Their design depends on soil moisture. In dry soils, block channels with concrete or brick walls or reinforced concrete single- or multi-cell ones are most widespread.

The channel walls can have a thickness of 1/2 brick (120 mm) for small-diameter pipelines and 1 brick (250 mm) for large-diameter pipelines.

The walls are erected only from ordinary brick of a grade not lower than 75. Sand-lime brick Due to its low frost resistance, it is not recommended to use. The channels are covered with a reinforced concrete slab. Brick channels, depending on the category of soil, have several varieties. In dense and dry soils, the bottom of the canal does not require concrete preparation; it is enough to compact the crushed stone directly into the ground. In soft soils concrete base add additional iron concrete slab. When groundwater levels are high, drainage is provided to drain them. The walls are erected after installation and insulation of the pipelines.

For pipelines of large diameters, channels are used that are assembled from standard reinforced concrete tray-type elements KL and KLS, as well as from prefabricated reinforced concrete slabs KS.

Channels of the KL type consist of standard tray elements covered with flat reinforced concrete slabs.

KLS type channels consist of two tray elements stacked on top of each other and connected at cement mortar using an I-beam.

In KS type channels Wall panels the bottom slabs are installed in the grooves and filled with concrete. These channels are covered with flat reinforced concrete slabs.

The bases of all types of canals are made of concrete slabs or sand preparation, depending on the type of soil.

Along with the channels discussed above, other types are also used.

Vaulted channels consist of reinforced concrete arches or semicircular shells that cover the pipeline. At the bottom of the trench, only the base of the channel is made.

For large-diameter pipelines, a vaulted two-cell channel with a dividing wall is used, while the channel arch is formed from two half-vaults.

When installing a non-passable channel intended for laying in wet and soft soils, the walls and bottom of the channel are made in the form of a reinforced concrete trough-shaped tray, and the ceiling consists of prefabricated reinforced concrete slabs. The outer surface of the tray (walls and bottom) is covered with waterproofing from two layers of roofing material on bitumen mastic, the surface of the base is also covered with waterproofing, then the tray is installed or concreted. Before filling the trench, the waterproofing is protected with a special wall made of brick.

Replacement of failed pipes or repair of thermal insulation in such channels is possible only by developing groups, and sometimes by dismantling the pavement. Therefore, the heating network in non-passable channels is routed along lawns or in green areas.

Semi-bore channels. In difficult conditions where heat pipes cross existing underground devices (under the roadway, with a high level of groundwater), semi-passable channels are installed instead of impassable ones. Semi-through channels are also used for a small number of pipes in places where, due to operating conditions, opening of the roadway is excluded. The height of the semi-bore channel is taken equal to 1400 mm. The channels are made of prefabricated reinforced concrete elements. The designs of semi-through and through channels are almost similar.

Passage channels used when there are a large number of pipes. They are laid under the pavements of large highways, in the territories of large industrial enterprises, in areas adjacent to the buildings of thermal power plants. Along with heat pipelines, other underground communications are located in the passage channels - electrical cables, telephone cables, water supply, gas pipelines, etc. The collectors provide free access for service personnel to the pipelines for inspection and emergency response.

Passage channels must have natural ventilation with threefold air exchange, ensuring an air temperature of no more than 40 ° C, and lighting. Entrances to passage channels are arranged every 200 - 300 m. In places where gland expansion joints designed to absorb thermal expansion, locking devices and other equipment are located, special niches and additional hatches are installed. The height of the passage channels must be at least 1800 mm.

Their designs are of three types − from ribbed slabs, from frame structure links and from blocks.

Passage channels from ribbed slabs , are made of four reinforced concrete panels: a bottom, two walls and a floor slab, manufactured in a factory method on rolling mills. The panels are connected with bolts, and the outer surface of the channel overlap is covered with insulation. Channel sections are installed on a concrete slab. The weight of one section of such a channel with a cross-section of 1.46x1.87 m and a length of 3.2 m is 5 tons, entrances are arranged every 50 m.

Passage channel made of reinforced concrete frame sections, the top is covered with insulation. The channel elements have a length of 1.8 and 2.4 m and are of normal and increased strength when buried, respectively, up to 2 and 4 m above the ceiling. Reinforced concrete slab place only under the joints of the links.

The next view is collector made of reinforced concrete blocks three types: L-shaped wall, two floor slabs and bottom. The blocks at the joints are connected with monolithic reinforced concrete. These collectors are also made normal and reinforced.

Channelless installation.

When laying without a channel, pipelines are protected from mechanical influences by reinforced thermal insulation - a shell.

Advantages advantages of channelless pipeline laying are: relatively low cost of construction and installation work, reduction in the volume of excavation work and reduction in construction time. To her shortcomings include: complication repair work and difficulty in moving pipelines clamped by soil. Channelless pipeline laying is widely used in dry sandy soils. It is used in wet soils, but with mandatory device in the area where drainage pipes are located.

Movable supports are not used for channelless laying of pipelines. Pipes with thermal insulation are laid directly on a sand cushion located on the pre-leveled bottom of the trench. sand cushion, which is a bed for pipes, has the best elastic properties and allows for the greatest uniformity of temperature movements. In the weak and clay soils the layer of sand at the bottom of the trench should be at least 100-150 mm thick. Fixed supports for ductless pipe laying are reinforced concrete walls installed perpendicular to the heating pipes.

Compensation for thermal movements of pipes for any method of their ductless installation is ensured using bent or stuffing box compensators installed in special niches or chambers.

At the turns of the route, in order to avoid pinching the pipes in the ground and to ensure possible movements, impassable channels are installed. In places where the pipeline intersects the wall of the drip, as a result of uneven settlement of the soil and the base of the channel, the greatest bending of the pipelines occurs. To avoid bending the pipe, it is necessary to leave a gap in the hole in the wall, filling it with elastic material (for example, asbestos cord). Thermal insulation of the pipe includes an insulating layer of autoclaved concrete with a volumetric weight of 400 kg/m3, having steel reinforcement, a waterproofing coating consisting of three layers of brizol on bitumen-rubber mastic, which contains 5-7% crumb rubber and a protective layer made of asbestos-cement plaster over a steel mesh.

Return pipelines are insulated in the same way as supply lines. However, the presence of return line insulation depends on the diameter of the pipes. For pipe diameters up to 300 mm, insulation is required; with a pipe diameter of 300-500 mm, the insulation device must be determined by the technique using an economic calculation based on local conditions; for pipes with a diameter of 500 mm or more, insulation is not provided. Pipelines with such insulation are laid directly on the leveled compacted soil of the base of the trench.

To lower the groundwater level, special drainage pipelines are provided, which are laid at a depth of 400 mm from the bottom of the canal. Depending on working conditions drainage devices can be made of various pipes: for non-pressure drainage, ceramic concrete and asbestos-cement are used, and for pressure drainage, steel and cast iron are used.

Drainage pipes are laid with a slope of 0.002-0.003. At turns and when there are differences in pipe levels, special inspection wells are installed, similar to sewer wells.

Overhead laying of pipelines.

Based on the ease of installation and maintenance, laying pipes above the ground is more profitable than laying them underground. It also requires less material costs. However, this will spoil appearance environment and therefore this type of pipe laying cannot be used everywhere.

Load-bearing structures overhead laying of pipelines serve: for small and medium diameters - overhead supports and masts, ensuring the location of pipes at the required distance from the surface; for pipelines of large diameters, as a rule, trestle supports. The supports are usually made of reinforced concrete blocks. Masts and overpasses can be either steel or reinforced concrete. The distance between supports and masts during overhead installation should be equal to the distance between supports in the channels and depends on the diameters of the pipelines. In order to reduce the number of masts, intermediate supports are arranged using guy wires.

When laying above ground, thermal elongations of pipelines are compensated using bent expansion joints, which require minimum costs time for service. Maintenance of fittings is carried out from specially arranged sites. Roller bearings should be used as moving ones, creating minimal horizontal forces.

Also, when laying pipelines above ground, low supports can be used, which can be made of metal or low concrete blocks. At the intersections of such a route with pedestrian paths, special bridges are installed. And when crossing roads, either a compensator of the required height is installed or a channel is laid under the road for the passage of pipes.

The method of laying heating networks during reconstruction is chosen in accordance with the instructions of SNiP 2.04.07-86 “Heating networks”. Currently, in our country, about 84% of heating networks are laid in ducts, about 6% - ductless, the remaining 10% - above ground. The choice of one method or another is determined by local conditions, such as the nature of the soil, the presence and level of groundwater, the required reliability, cost-effectiveness of construction, as well as operating costs of maintenance. Laying methods are divided into above-ground and underground.

Aboveground laying of heating networks

Aboveground installation of heating networks is rarely used, since it disrupts the architectural ensemble of the area and, other things being equal, has higher costs compared to underground installation. heat losses, does not guarantee against freezing of the coolant in the event of malfunctions and accidents, and restricts passages. When reconstructing networks, it is recommended to use it at high groundwater levels, in permafrost conditions, with unfavorable terrain, in the territories of industrial enterprises, in areas free of buildings, outside the city or in places where it does not affect the architectural design and does not interferes with traffic.

Advantages of above-ground installation: accessibility of inspection and ease of operation; opportunity in as soon as possible detect and eliminate accidents in heat pipelines; absence of electrocorrosion from stray currents and corrosion from aggressive groundwater; lower cost of construction compared to the cost of underground installation of heating networks. Aboveground installation of heating networks is carried out: on separate supports (masts); on overpasses with a span in the form of purlins, trusses or suspended (cable-stayed) structures; along the walls of buildings. Free-standing masts or supports can be made of steel or reinforced concrete. For small volumes of construction of above-ground heating networks, steel masts made of profiled steel are used, but they are expensive and labor-intensive and therefore are being replaced by reinforced concrete ones. It is especially advisable to use reinforced concrete masts in mass construction on industrial sites, when it is cost-effective to organize their production in a factory.

For joint laying of heating networks with other pipelines for various purposes, overpasses made of metal or reinforced concrete are used. Depending on the number of simultaneously laid pipelines spans overpasses can be single-tiered or multi-tiered. Heat pipelines are usually laid on the lower tier of the overpass, while pipelines with a higher coolant temperature are placed closer to the edge, thereby providing a better location U-shaped expansion joints having different sizes. When laying heating mains on the territory of industrial enterprises, the method of above-ground installation on brackets fixed in the walls of buildings is also used. The span of heat pipes, i.e. the distances between the brackets are chosen taking into account the load-bearing capacity of the building structures.

Underground laying of heating networks

In cities and towns, heating mains are mainly laid underground, which does not spoil the architectural appearance, does not interfere with traffic and reduces heat loss by using the heat-shielding properties of the soil. Soil freezing is not dangerous for heating pipelines, so they can be laid in the zone of seasonal soil freezing. The shallower the depth of the heating network, the smaller the volume of excavation work and the lower the cost of construction. Underground networks are most often laid at a depth of 0.5 to 2 m and below the surface of the earth.

The disadvantages of underground heating pipes are: the danger of moisture and destruction of insulation due to the influence of soil or surface waters, which leads to a sharp increase in heat losses, as well as the danger of external corrosion of pipes due to the influence of stray electric currents, moisture and aggressive substances contained in the soil. Underground installation of heat pipelines involves the need to open up streets, driveways and courtyards.

Structurally, underground heating networks are divided into two fundamentally various types: ducted and ductless.

The design of the channel completely relieves heat pipelines from the mechanical impact of the soil mass and temporary transport loads and protects the pipelines and thermal insulation from the corrosive influence of the soil. Laying in channels ensures free movement of pipelines during temperature deformations in both the longitudinal (axial) and transverse directions, which allows the use of their self-compensating ability in corner sections of the route.

Laying in passage channels (tunnels) is the most advanced method, since this ensures constant access for maintenance personnel to pipelines to monitor their operation and carry out repairs, which in the best possible way ensures their reliability and durability. However, the cost of laying in passage channels is very high, and the channels themselves have large dimensions (clear height - at least 1.8 m and passage - 0.7 m). Pass-through channels are usually installed when laying a large number of pipes laid in one direction, for example, at the outlets from a thermal power plant.

Along with laying in non-passing channels, channelless laying of heat pipes is becoming increasingly popular. Refusal to use channels when laying heating networks is very promising and is one of the ways to reduce their cost. However, in channelless laying, the thermally insulated pipeline, due to direct contact with the ground, is subject to more active physical and mechanical influences (soil moisture, soil pressure and external loads, etc.) than in channel laying. Channelless installation possible by using a mechanically strong thermal and waterproofing shell that can protect pipelines from heat loss and withstand loads transmitted by the soil. Heating networks with pipe diameters up to 400 mm inclusive are recommended to be laid primarily using a ductless method.

Among channelless gaskets, the most widespread are last years received progressive gaskets using reinforced foam concrete, bitumen perlite, asphalt expanded clay concrete, phenolic foam plastic, polyurethane foam, polyurethane foam and others as monolithic thermal insulation thermal insulation materials. Ductless installations of heating networks continue to improve and are becoming increasingly widespread in construction and reconstruction practice. When reconstructing intra-block heating mains, there are more ample opportunities laying networks along basements than with new construction, since the construction of new sites often precedes the construction of buildings.

Installation of heating networks, laying pipes

Installation of pipelines and installation of thermal insulation on them is carried out using pre-insulated polyurethane foam pipes, shaped products in polyurethane foam insulation (fixed supports, tees and tee branches, transitions, end elements and intermediate elements, etc.), as well as polyurethane foam shells. Thermal insulation of straight sections, branches, pipeline elements, sliding supports, ball valves is being installed, as well as butt joints are being installed using heat-shrinkable sleeves, heat-shrinkable tape, polyurethane foam components, galvanized casings and heat-insulating polyurethane foam shells.

The laying of heating networks and installation of polyurethane foam insulation is carried out in several stages - preparatory stage (excavation, delivery of polyurethane foam pipes and elements to the route, inspection of products), laying of pipelines (installation of pipes and elements), installation of UEC system devices and installation of butt joints.

The depth of laying polyurethane foam pipes when laying heating networks should be taken into account the difference in density between the polyurethane foam steel pipe and the thermal insulation layer of polyurethane foam, as well as heat transfer standards and normatively permissible heat losses.

The development of trenches for channelless installation should be carried out mechanically in compliance with the requirements of SNiP 3.02.01 - 87 "Earth structures".

The minimum depth for laying polyurethane foam pipes in a polyethylene shell when laying heating mains in the ground should be at least 0.5 m outside the roadway and 0.7 m within the roadway, counting to the top of the thermal insulation.

The maximum depth of laying thermally insulated pipes when installing pipelines in polyurethane foam insulation when laying heating networks should be determined by calculation taking into account the stability of the polyurethane foam layer under the action of static load.

Installation of polyurethane foam pipes is usually carried out at the bottom of the trench. It is allowed to weld straight sections in the section at the edge of the trench. Installation of polyurethane foam pipes in a polyethylene sheath is carried out at outdoor temperatures down to -15 ... -18°C.

cutting steel pipes(if necessary) is carried out using a gas cutting machine, in which case the thermal insulation is removed using a mechanized hand tools on a section 300 mm long, and the ends of the thermal insulation during cutting of steel pipes are covered with a moistened cloth or a rigid screen to protect the thermal insulation layer of polyurethane foam.

Welding of pipe joints and inspection of welded connections of pipelines during the installation of polyurethane foam pipes should be carried out in accordance with the requirements of SNiP 3.05.03-85 "Heat networks", VSN 29-95 and VSN 11-94.

In production welding work It is necessary to protect the polyurethane foam insulation and polyethylene sheath, as well as the ends of the wires coming out of the insulation, from sparks.

When using a heat-shrinkable sleeve as protection for a welded joint, it is put on the pipeline before the start of welding work. When sealing a joint using a fill joint or a polyurethane foam shell joint, where a galvanized casing and heat-shrink tape are used as a protective layer, pipe welding is carried out regardless of the availability of materials for sealing the joints.

Before the construction of a heating main during ductless pipe laying, polyurethane foam pipes, fittings in polyurethane foam insulation, thermally insulated with polyurethane foam Ball Valves and elements pipeline system subjected to a thorough inspection in order to detect cracks, chips, deep cuts, punctures and other mechanical damage polyethylene shell thermal insulation. If cracks, deep cuts and other damage to the coating of polyurethane foam pipes in a polyethylene or galvanized shell are detected, they are repaired by extrusion welding, by applying heat-shrinkable cuffs (couplings) or galvanized bandages.

Before installing a ductless heating main, pipelines in polyurethane foam insulation and fittings in polyurethane foam are laid out on the edge or bottom of the trench using a crane or pipe layer, soft “towels” or flexible slings.

Lowering insulated polyurethane foam pipes into a trench should be done smoothly, without jerking or hitting the walls and bottom of channels and trenches. Before installing polyurethane foam pipes in trenches or channels, it is imperative to check the integrity of the signal wires of the operational remote control system (SODC system) and their isolation from the steel pipe.

In order to prevent damage to the shell, polyurethane foam pipes laid on a sandy base during channelless installation should not rest on stones, bricks and other solid inclusions, which should be removed, and the resulting depressions should be filled with sand.

If it is necessary to control calculations of the laying depths of heat pipelines with polyurethane foam insulation in a polyethylene shell for specific installation conditions, the design resistance of polyurethane foam should be taken as 0.1 MPa, for a polyethylene shell - 1.6 MPa.

If it is necessary to lay underground heating networks with thermal insulation of polyurethane foam in a polyethylene shell at a depth more than permissible, they should be laid in channels (tunnels). When laying routes under the roadway, railway tracks and other objects located above the PPU pipe, the pipes in PPU insulation are made with reinforcement (polyethylene overlay rings along the entire length of the shell) and are laid in a steel case that protects from external mechanical influences.

It is produced in non-through, through, and semi-through channels, as well as in general collectors along with other communications. Using the example of Leningrad, in recent years, channelless installation has begun to be used, which is considered the most effective. But even in this option, individual sections are laid into channels - compensation niches, turning angles, etc.

If the underground laying of heating networks is carried out in an unplanned area, local planning of the earth's surface is carried out. This is done for the purpose of draining surface water. Elements of heating networks (outer surfaces of ceilings and walls of channels, chambers, etc.) are finished with coating bitumen insulation. If the installation takes place under green areas, the structures are covered with adhesive waterproofing, which is made from bitumen roll materials. Networks installed below the maximum groundwater level are equipped with associated drainage. Its diameter must be more than 150 mm.

Installation of expansion joints

Underground pipeline laying involves the installation of compensators. Installation of compensators in the design position is permitted after preliminary testing of heating networks for tightness and strength, their backfilling and underground laying of chambers, channels and panel supports.

If the heating networks being laid are installed to service shut-off brick or reinforced concrete fittings, underground chambers are installed. The main heating networks pass through the chambers. They are equipped with inserts with shut-off valves for installing branches to consumers. The height of the chamber must correspond to the safety of maintenance.

IN major cities underground pipeline laying carried out in conjunction with other engineering networks. City and intra-block tunnels are combined with water pipelines with a diameter of up to 300 mm, power cables voltage up to 10 kV and communication cables. City tunnels with compressed air pipelines with a pressure of up to 16 MPa are combined with pressure sewerage. Intra-block tunnels are laid together with water networks with a diameter of up to 250 mm and a gas pipeline natural gas with pressure up to 0 005 MPa and diameter no more than 150 mm. Heating networks are laid in cases or tunnels under city passages, at the intersection of large highways and under areas with modern coverage.

Underground pipeline installation can be carried out in non-passable channels.

Channelless underground installation is carried out throughout the territory of populated areas. Installation is carried out in non-passable channels together with other utility networks in city-wide or intra-block sewers. Aboveground pipeline installation is carried out at enterprise sites. Heating networks are installed on separate racks and supports. Sometimes underground installation is also allowed.

More information about underground installation of expansion joints

For channelless installation and in non-passable channels, it is carried out underground installation of bellows expansion joints in the cells. Special pavilions are not constructed when heating networks are laid on separate supports or overpasses. They are installed at fixed supports. Only one expansion joint is mounted between two fixed supports. Guide supports are installed before and after expansion joints. One of the guide supports must be stationary.

For aesthetic and architectural reasons, it is provided in residential areas.

At underground installation heating networks and a tap is used for air installation. It is also used on masts, trestles, for the construction of office premises 3 floors high and above-ground pavilions of pumping stations.

In special collectors and together with other utility networks, underground pipeline laying within settlement(city or town). Installation is carried out in semi-through, non-through and through channels directly in the ground.

All pipelines laid underground must be inspected periodically. The condition of thermal insulation, building insulation structures and the pipelines themselves are monitored. Preventative planned excavations are carried out in accordance with the schedule, at least once a year. The number of pits is determined depending on the condition of the underground gaskets and the length of the heating networks.

Laying pipes in a trench is carried out using the same mechanisms as for underground laying of heating networks. These are truck cranes, pipe layers and cranes crawler. If these mechanisms are not available or it is not possible to use them due to cramped production conditions, then the pipes can be lowered into the trench using mounting tripods, which are equipped manual winches or hoists. For pipes with a small diameter, 2 ropes are used and they are lowered into the trench manually.

One of the main features of heat pipes is the relative heat the product transported through them - water or steam, in most cases exceeding 100 ° C, which largely determines the nature of the design of heating networks, since it requires the installation of thermal insulation and ensuring freedom of movement of pipes when they are heated or cooled.

The presence of thermal insulation and the requirement for free movement of pipes significantly complicates the design of heat pipelines - the latter are laid in channels, tunnels or protective shells.

Periodic heating of the walls of heat pipelines to a temperature of 130-150°C makes anti-corrosion coatings, usually used to protect unheated steel pipelines laid in the ground, unsuitable. To protect heat pipelines from external corrosion, it is necessary to use building insulation structures that prevent the penetration of ground moisture into the pipelines.

The designs of heat pipelines currently used are significantly diverse. Based on the method of installation, heating networks are divided into underground and above-ground (air).

Underground installation of heating network pipelines is carried out:

a) in non-passing and semi-passing channels;

b) in tunnels or sewers together with other communications;

c) in shells various shapes and in the form of backfill gaskets.

When laying underground, chambers, niches for compensators, fixed supports, etc. are built along the route.

Aboveground installation of heating network pipelines is carried out:

a) on overpasses with a continuous span;

b) on separate masts (supports);

c) on suspended spans (cable-stayed).

A special group of structures includes special structures: underwater, overground and underground passages and a number of others.

The main disadvantages of those used in construction underground structures heat pipes are: fragility, large heat losses, labor-intensive manufacturing, significant consumption building materials and high construction costs.

The most widely used structures are prefabricated structures of impassable channels with concrete walls. The use of non-passage channels is justified in the case of laying heating networks in wet soils, provided that associated drainage is installed . You should focus on the use of non-passable channels made from standardized prefabricated reinforced concrete parts. The specified reinforced concrete channels can be used for heating networks with a diameter of up to 600 mm. It is possible to use non-passing channels assembled from vibrating rolling plates.

Non-passing channels with suspended thermal insulation forming around the pipes air gap, are indispensable in sections of the route with self-compensation for thermal elongation of heat pipes. Characteristic feature Channel laying of heating networks, in contrast to ductless, is to ensure the movement of heat pipes in the longitudinal and transverse directions.

When laying heat pipelines under passages with heavy traffic and improved road surfaces, semi-through channels made of prefabricated reinforced concrete parts are used. When laying a large number of heat pipes of significant diameters, through-pass tunnels are used.

For heating mains of large diameters there are also standard designs channels that have proven themselves both in construction and operation. For example, heating mains with a diameter of 700-1200 mm are being built in Moscow. However, channel designs must be improved until more rational decisions. For laying heat pipes, prefabricated reinforced concrete channels of single-cell and double-cell sections are used. Basically, these channels are designed as a semi-bore type for the possibility of inspecting them service personnel, as well as ensuring maximum reliability of heating mains in operation.

In Moscow and some other cities, ductless laying of heat pipelines with a two-layer cylindrical shell consisting of a reinforced concrete pipe and a heat-insulating layer (mineral wool) has been used.

Reinforced concrete pipes have sufficient mechanical strength, high resistance to shock and vibration loads, good moisture resistance. Therefore, they reliably protect the heat pipeline from moisture and loads transmitted by the soil. This achieves more favorable conditions for the operation of heat pipelines: stresses in the pipe walls are reduced and the durability of thermal insulation is ensured.

The outer reinforced concrete shell remains motionless when the heat pipe moves in the axial direction due to temperature deformations, which distinguishes this design from a structure with a reinforced foam concrete shell moving on the ground along with the heat pipe.

A similar design is made using asbestos-cement pipes and reinforced concrete half-cylinders as the outer shell.

The use of ductless structures can be recommended when laying in dry soils with the outer surface of the heat pipes protected by two layers of insulation. Channelless installation of heat pipelines with backfill thermal insulation with peat, diatomaceous earth, etc. turned out to be unsuccessful. Currently underway experimental work on creating backfill material.

The chamber designs used in the construction of heating networks are very diverse. Prefabricated chambers made of reinforced concrete parts are designed for heat pipelines of small and medium diameters. Cameras large sizes made of concrete blocks and monolithic reinforced concrete. The structures of fixed supports in the channels are made of monolithic and prefabricated reinforced concrete. In Moscow, Novosibirsk and other cities, so-called common collectors have become widespread, in which heat pipes are laid together with electrical and telephone cables, water supply and other underground networks.

Passage channels and common collectors are equipped with electric lighting, telephone communications, ventilation, and various devices automatic control and drainage facilities.

In ventilated passage tunnels, a favorable temperature and humidity regime of the air environment is ensured, which contributes to the good preservation of heat pipes.

During the construction of common sewers in Moscow open method The design of large ribbed reinforced concrete blocks, proposed by engineers N. M. Davidyants and A. A. Lyamin, has proven itself well.

The method of jointly laying underground networks in common sewers has a number of advantages, the most significant of which are : increasing the durability of the material part of networks and ensuring the best conditions operation. When operating heating networks in collectors, as well as when it is necessary to build new underground networks, it is not necessary to open up urban areas for repairs. The placement of networks for various purposes in collectors makes it possible to organize their complex and planned design, construction and operation and makes it possible to streamline the entire system of placing underground networks more compactly both in plan and in the cross section of city passages. Underground urban sewers are modern engineering structures.

a - separate;

b - joint;

TK - telephone sewer;

E - electrical cables;

T - heat pipes 2d = 400 mm;

G - gas pipeline d=300 mm

B - water supply d = 300 mm;

C - drain d= 600 mm;

K - sewerage d = 200 mm;

T KAB - telephone cables

Internal view of the common collector

Number of pipelines and cables placed in manifolds of various sections

The design of underground, overground and underwater passages of heat pipelines through natural and artificial obstacles is included in the general complex of designing heating networks and is only in rare cases carried out by specialized organizations.

Underwater crossings of rivers are carried out in the form of passage tunnels and siphons; air crossings across rivers to railway tracks - in the form of bridge crossings. It is also possible to lay heat pipelines along existing bridges and overpasses.

When the route crosses the heating networks of iron and highways, as well as city passages, underground passages are most often constructed, carried out in a closed way to provide uninterrupted operation expensive

Underground passages are made mainly in the form of tunnels, constructed using metal shields of circular cross-section. These tunnels require significant deepening, and therefore often fall into the groundwater zone, which complicates the work and requires the organization of drainage from the tunnel during operation.

Another type of underground passage is the laying of steel cases, inside of which heat pipes are placed. The cases are laid by pressing or puncturing steel pipes hydraulic jacks. The implementation of this type of transition is advisable where it is possible to pass above the groundwater level without disturbing existing underground communications.

Underpasses made of steel casings are widely used in the construction of heating networks.

The correct choice of one or another type of transition is the main task in the design, since the cost of these structures is very high and significantly increases the total cost of heating networks.

At industrial enterprises, overhead laying of heat pipelines along trestles, often made of rolled metal, has become widespread.

The design of overpasses using precast reinforced concrete is now significantly simplified in connection with the release of the standard project “Unified prefabricated reinforced concrete free-standing supports for process pipelines” (IS-01-06 series).

In urban heating networks, overhead laying of heat pipelines was carried out mainly along metal masts of a lattice structure. Reinforced concrete masts began to be manufactured only at the present time. For example, reinforced concrete masts made from prefabricated parts for heating mains with a diameter of 1200 mm have found application in Moscow. The structural parts of these masts are manufactured at the factory and assembled on the track.