Substantiation of methods for laying heat pipelines. Selection of equipment and building structures for heating networks

The main types of pipeline laying are underground and aboveground. Underground piping is the most common. It is divided into laying pipelines directly in the ground (channelless) and in channels. When laying on the ground, pipelines can be on the ground or above the ground at such a level that they do not interfere with the movement of vehicles. Above-ground laying is used on suburban highways when crossing ravines, rivers, railways and other structures.

Above-ground laying of 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 installing 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 options. Minimum 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 the reliability of the heat pipelines, it is necessary to apply their mechanical and thermal protection.

Underground laying of pipelines.

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

Direct laying of pipes in the ground (channelless).

Pipe laying in channels (channel).

Laying pipelines in channels.

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

Channelless laying.

With channelless laying, pipelines are protected from mechanical influences by reinforced thermal insulation - a shell.

The advantages of channelless laying of pipelines are: the relatively low cost of construction and installation works, a reduction in the volume of earthworks and a reduction in construction time. Its disadvantages include: the complication of repair work and the difficulty of moving pipelines clamped by the ground. Channelless laying of pipelines is widely used in dry sandy soils. It finds application in wet soils, but with a mandatory device in the area of ​​\u200b\u200bthe drainage pipes.

Above ground piping.

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

The bearing structures for above-ground laying of pipelines are: for small and medium diameters - above-ground 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. Supports are usually made of reinforced concrete blocks. Masts and overpasses can be either steel or reinforced concrete. The distance between the supports and masts during above-ground laying should be equal to the distance between the supports in the channels and depends on the diameters of the pipelines. In order to reduce the number of masts, intermediate supports are arranged with braces.

Placement of distribution routes of underground networks on the territory of the microdistrict and residential areas depends on the general planning solution and the terrain.

Distances from underground networks to buildings, structures, green spaces and to neighboring underground networks are regulated. All trenches of underground networks are located outside the zone of pressure in the ground from buildings, which helps to maintain the integrity of the base of the foundations of the building, protecting it from erosion (Fig. 1). Compliance standard distances, moreover, prevents the possibility of damage, and, if necessary, provides the conditions for repair. Minimum values these distances are given in SNiP 2.07.01-89*.

Picture 1. 1 - low-current cables; 2- power cables; 3 - telephone cables; 4 - heating network; 5 - sewerage; 6- drain; 7- gas pipeline; 8- plumbing; 9 - the border of the freezing zone

The laying of underground engineering networks can be done in three ways (Fig. 2): 1) in a separate way, when each communication is laid in the ground separately in compliance with the relevant sanitary-technological and building conditions for placement, regardless of the methods and timing of the installation of other communications; 2) in a combined way, when communications are laid in one trench at the same time for various purposes; 3) in a combined collector, when networks for various purposes are jointly located in one collector.

Figure 2. a - in a common trench; b - in an impassable collector; in - in the passage manifold; 1 - heating system; 2 - gas pipeline; 3 - plumbing; 4 - drain; 5 - sewerage; 6 - communication cables; 7 - power cables

two the latest ways lay engineering networks of one direction. In the case when the network of underground communications is so developed that there is not enough space in the trenches, the third method is used.

The separate method of laying underground networks has great disadvantages, since significant earthworks when one communication is opened can cause damage to others due to changes in pressure and soil connectivity. In addition, the construction time increases due to the fact that communications are laid in series.

With the combined method, pipelines are laid simultaneously, and cables, pipelines and impassable channels can be located in one trench. This method is applicable in the reconstruction of streets or the creation of new buildings, since the volume of earthworks is reduced by 20 ... 40%.

Laying networks in a combined collector reduces the amount of earthwork and construction time. This method greatly facilitates operation, simplifies the repair and replacement of communications without excavation. When laying networks in a combined collector, it is possible to arrange separate communications even after the end of the zero construction cycle. The collector can accommodate heat networks running in one direction with a diameter of 500 to 900 mm, water conduits with a diameter of up to 500 mm, more than ten communication cables and power cables with a voltage of up to 10 kV. It is allowed to locate air ducts, pressure pipelines of water supply, sewerage in common collectors. Joint laying of gas pipelines and pipelines with combustible and flammable substances is not allowed.

Collectors are distinguished by design, size, shape cross section. The collector is a walk-through (human-height), semi-walk-through (below 1.5 m) or impassable gallery of prefabricated reinforced concrete structures.

Passage collectors must be equipped with supply natural and mechanical ventilation to ensure the internal temperature within 5 ... 30 ° C and at least three air exchanges in 1 hour, as well as electric lighting and pumping devices.

Shallow and deep networks. Underground communications of the city are the most important element of engineering equipment and landscaping, meeting the necessary sanitary and hygienic requirements and providing a high level of convenience for the population. Underground utilities include networks of hot and cold water supply, gasification, power supply, alarm special purpose, telephonization, radio broadcasting, telegraph, sewerage, drainage (storm sewerage), drainage, as well as new types of development (pneumatic mail, garbage disposal), etc.

Urban underground communications are constantly evolving, representing a complex and important part city ​​"organism". Underground networks are divided into transit, main and distribution (distributing).

Transit includes those underground utilities that pass through the city, but are not used in the city, for example, a gas pipeline, an oil pipeline running from a field through a given city.

The main networks include the main networks of the city, through which the main types of carriers in the city are supplied or removed, designed for big number consumers. They are usually located in the direction of the main transport routes of the city.

Distribution (distributing) networks include those communications that branch off from the main lines and are brought directly to the houses.

Underground networks have different depth laying. Shallow networks are located in the soil freezing zone, and deep networks are located below the freezing zone. The depth of soil freezing is determined according to SNiP 23-01-99. For Moscow, for example, it is 140 cm.

Shallow networks include networks whose operation allows significant cooling: electrical low-current and power cables, telephone and telegraph cables, alarms, gas pipelines, heating networks. Deep-laid networks include underground utilities that cannot be overcooled: water supply, sewerage, drainage. For underground networks, steel, concrete, reinforced concrete, asbestos-cement, ceramic and polyethylene pipelines can be used.

Water supply. One of necessary conditions urban beautification is water supply. The water supply system takes into account the number of consumers and the rate of water consumption. For all categories of consumers there are rules. The population needs water to meet physiological needs: cooking, maintaining hygiene, household activities. The rate of water consumption by one person per day varies depending on the degree of improvement of the city. For the population of large cities, provided with cold and hot water supply, the rate of water consumption per 1 person. is about 400 l / day. This norm includes water consumption for the needs of public utilities (baths, hairdressers, laundries, catering establishments, etc.). Another consumer of water is industrial enterprises, almost in each of which technological process associated with high water consumption.

The city also takes into account the consumption of water for firefighting, watering green spaces and, depending on climatic conditions, for watering the urban area.

Depending on the amount of water supplied, a water conduit system is selected. They can represent two or more parallel threads. Water comes to consumers from a water supply source (rivers, The groundwater, seas) through treatment facilities where it is filtered, decolorized, disinfected with chlorine, ozone, hydrogen or ultraviolet rays, desalted and settled.

Pipelines are made of steel, cast iron, reinforced concrete and plastic, polyvinyl chloride and polyethylene.

When designing water supply networks, it is very important to provide for the preservation of the required water temperature in the pipes. Therefore, it should not be excessively cooled and heated. Therefore, it is accepted that water networks are usually laid underground. But with the technological and feasibility study, other types of placement are allowed.

To exclude hypothermia and freezing of water pipes, the depth of their laying, counting to the bottom, should be 0.5 m more than the calculated depth of penetration into the ground of zero temperature, i.e., the depth of soil freezing. To prevent water heating in the summer season, the depth of the pipelines should be taken at least 0.5 m, counting to the top of the pipes. The depth of laying of industrial pipelines must be checked from the condition of preventing water heating only if it is unacceptable for technological reasons.

Water supply networks are made ring and in rare cases dead ends, as they are less convenient for repair and operation, and water can stagnate in them.

The pipe diameter is taken by calculation in accordance with the instructions of SNiP 2.04.02-84. The diameter of the pipes of the water supply system, combined with the fire-fighting one, for urban areas is not less than 100 and not more than 1000 mm. A free head of at least 10 m of water column is maintained in the water supply network, which makes it possible to use the water supply network to extinguish fires. For this purpose, throughout the entire length of the water supply network, after 150 m, special devices are installed for connecting fire hoses - hydrants. The norms stipulate that for external fire extinguishing, a water flow of 100 l / s is required.

Due to the free pressure in the water supply network, at least 10 m of low-rise buildings are provided with water without an additional pump. In high-rise buildings, additional pressure is created by local pumps.

The location of the water lines on master plans, as well as minimum distances in plan and at the intersection from the outer surface of pipes to structures and engineering networks should be taken in accordance with SNiP 2.07.01-89 *.

On the water networks for correct operation and repairs arrange water wells. They are made from precast concrete or from local materials. At the location of the level ground water above the bottom of the well, waterproofing of its bottom and walls is provided 0.5 m above the groundwater level.

Water pipes for irrigation, filling open pools, functioning of fountains operate only in summer, therefore they are allowed to be laid at a depth of 0.5 m.

Hot water supply suit in cities with a high level of improvement. Supply hot water of residential buildings is produced by quarterly systems of centralized hot water supply from separate central heating points (CHP), which, as a rule, are located in the center of the serviced area. Thermal power TsTP is chosen taking into account the prospective construction.

The hot water supply network is calculated at centralized system water supply into two operating modes: hot water draw-off mode during hours of maximum water consumption; mode of water circulation during hours of minimum drawdown.

For hot water supply networks, galvanized water and gas pipes are used, connected by threading or welding. The slope of pipelines is assumed to be at least 0.002. Pipes are insulated to reduce heat loss. Laying of hot water pipes is allowed in a channelless way (directly in the ground) or in channels together with heating networks.

Sewerage. Sewerage is a necessary system for the treatment of populated areas from wastewater. Its task is to remove water contaminated as a result of human household activities and the work of industrial enterprises that use water in the technological process.

Sewerage can be common and separate. Alloy sewerage carries out the removal of one system of pipelines of storm sewage, which comes after rain from urban areas through storm grates, and household and fecal water coming from residential buildings. With separate sewerage, two independent systems sewage disposal: storm sewerage (drainage), household and fecal. Waste water from industrial enterprises is diverted separate system to neutralize them from specific contaminants. Currently, a separate sewerage system is most applicable.

Sewerage not only removes wastewater from buildings, but also cleans them to such an extent that when they are discharged into a reservoir, they do not violate its sanitary conditions. For this purpose, sewer networks are used, pumping stations pumping, facilities for waste water treatment and for the release of waste treated water.

Diameters sewer pipes systems depend on the amount of wastewater, which is determined by the degree of improvement, i.e. the norm of water consumption, the presence of hot water supply. Yes, the rate waste water with centralized hot water supply and the presence of a bath - 400 l / day. for 1 person, and with gas heating installations - 300 l / day.

The sewerage route is selected using a feasibility study of possible options. With parallel laying of several pressure pipelines, the distance from the outer surfaces of the pipes to structures and engineering communications must be taken in accordance with SNiP 2.04.03-85 based on the conditions for protecting adjacent pipelines and performing work.

Manholes suit in all places of change of direction, diameter or slope, in places of attachment of side lines. In addition, manholes are built at certain distances on all pipelines to monitor their condition and timely cleaning. Currently, wells are unified and are divided into small - for pipes with a diameter of up to 600 mm and large - more than 600 mm. In terms of shape, typical wells are round, rectangular, trapezoidal. The most economical in terms of concrete consumption and easy to manufacture are round wells.

The smallest laying depth is taken in accordance with SNiP 2.04.03-85 for sewer pipes with a diameter of up to 500 mm per 0.3 m, for pipes of large diameter - 0.5 m less than the greatest depth of penetration into the soil of zero temperature, but not less than 0, 7 m to the top of the pipe, counting from the layout marks.

Heat supply. Thermal energy required for the operation of industrial enterprises, heating, ventilation, air conditioning and centralized hot water supply of buildings. Housing and communal services use about 25% of all heat energy consumed by the city.

The heat supply of cities can be carried out in two ways: centralized (obtaining thermal energy from thermal power plants and powerful boiler houses) and decentralized (from local heat sources).

In accordance with SNiP 2.07.01-89*, the heat supply of cities and residential areas with buildings over two floors high must be centralized. With district heating, one boiler plant supplies heat to a group of houses, a quarter or district of a city, as well as industrial enterprises. Boilers, depending on the purpose, are divided into energy, production and heating. Heating boiler houses provide heat for the needs of heating, ventilation and hot water supply of residential and public buildings, and depending on the production capacity there are individual and group. Group services are conditionally subdivided depending on the size of the serviced territory into quarterly and district ones.

To transport heat to consumers, pipelines are used - heating networks that can transfer heat using water and steam, and depending on the coolant, they can respectively be water and steam.

Currently, thermal networks can transfer heat over long distances. Heating network different districts of the city are interconnected, so that in case of failure of one heat source, it could be duplicated by another. This allows you to uninterruptedly supply heat to all areas of the city and at the same time eliminate the malfunction.

Heating networks that supply heat to industrial enterprises, are called industrial, to residential and public buildings - communal, to enterprises and civil buildings - mixed.

Heating networks are made two- and multi-pipe. The most common is a two-pipe system, in which one pipe is supply, the other is return. In this system, water circulates through vicious circle: having given its heat to the consumer, it returns to the boiler room. In residential areas, two types of water heating systems are used: open and closed. Their difference lies in the fact that with a closed heat supply system, a constant amount of water circulates in the pipelines, and with an open part of the water, it is taken directly from the system for the needs of hot water supply. In an open heating system, water must be of equal quality to drinking water, and the water supply must be constantly replenished.

The main networks are located in the main directions from the heat source and consist of pipes of large diameters - from 400 to 1200 mm. Distribution networks have a diameter of branch pipelines from main lines from 100 to 300 mm, and a diameter of pipelines leading to consumers is from 50 to 150 mm.

Steam heating systems are made one- and two-pipe, while the condensate is returned according to special pipe- condensate line. Under the influence of an initial pressure of 0.6 ... 0.7 MPa, and sometimes 1.3 ... 1.6 MPa, the steam moves at a speed of 30 ... 40 m / s. Pipes are used metal and metal-polymer in accordance with SP-41-102-98 and SNiP 2.05.06-85. When choosing a method for laying heat pipes, the main task is to ensure the durability, reliability and cost-effectiveness of the solution.

Channelless laying of heat pipes - simple and cheap way laying, so it is the most common. This method, however, has major disadvantages, such as corrosion, difficulty in repair, lack of periodic supervision. Partially, these shortcomings are overcome by protecting the pipes from external influences of the soil using insulating material, cement peel and waterproofing. This method of protection is used in reinforced concrete, where the reinforcement is made in the form of a mesh, which gives significant rigidity to the pipelines. It is allowed to lay heat networks in common trenches with water pipes, drains, sewerage and gas pipelines with a pressure of up to 0.3 MPa inclusive.

Laying in impassable channels - the most convenient way laying heat pipes, which explains its widespread use. The advantage of this method over channelless laying is that the pipeline is protected from pressure fluctuations in the ground, as it is enclosed in a channel, where it is located on special mobile and fixed supports. However, it has a drawback: there is no constant monitoring of the state of the networks, and in the event of an accident, it is required to break some part of the channel in order to find the place of damage. In impassable channels, heating networks can be located with oil and fuel pipelines, pipelines compressed air pressure up to 1.6 MPa and water pipes.

In through collectors, heat networks can be placed together with water pipes with a diameter of up to 300 mm, communication cables, power cables with a voltage of up to 10 kV, and in city collectors - also with compressed air pipelines with a pressure of up to 1.6 MPa and pressure sewerage. In intra-quarter collectors, joint laying of water networks with a diameter of not more than 250 mm with gas pipelines is allowed natural gas pressure up to 0.005 MPa, diameter up to 150 mm. When laying a heating network and a water supply system together, in order to avoid heating the latter, it is thermally insulated and placed either in one row or under heating networks, taking into account the standard laying depth. Continuous monitoring and control over the state of the networks is carried out in the through collectors. Repair of such networks is simplified. In difficult areas, for example, under central highways with high traffic, when crossing railways, under buildings where pass-through collectors cannot be laid, and impassable channels cannot be laid due to limited ability to tear them apart for repair, semi-through channels are used. Although the passage in them is very small (height up to 1.4 m, width 0.4 ... 0.5 m), it is possible to inspect and repair the heating system.

The route of heating networks in cities is laid in the technical lanes allocated for engineering networks parallel to the red lines of streets, roads and driveways outside the carriageway and the strip of green spaces, but when justified, the location of the heating main under the carriageway or sidewalk of the streets is allowed. Heating systems cannot be laid along the edges of terraces, ravines or artificial recesses with subsiding soils.

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

SNiP 2.04.07-86 and SNiP 3.05.03-85 provide special conditions for arranging intersections of other underground structures with heating networks.

Gas supply. Thanks to the development of the gas industry in our country, most of the towns and cities are gasified. Gas is used in industry and housing and communal services. It is transported through pipelines from fields over long distances and delivered to the consumer in the form of a combustible mixture of hydrocarbons, hydrogen and carbon monoxide. Gas consumption rates depend on the equipment of the apartment, climatic conditions, and the level of development of public services. For example, the rate of gas consumption in an apartment with gas stove and hot water supply is accepted 77 m 3 / year for 1 person, and in an apartment with a gas stove and gas water heater for hot water supply - 160 m 3 / year.

The city gas supply system consists of gas pipelines, gas control points and service facilities.

Gas pipelines transporting wet gas are laid below the zone of seasonal soil freezing with slopes of 0.002 towards the condensate collectors. Gas pipelines transporting dried gas, when laid in non-heaving soils, may be located in the zone of seasonal freezing of the soil.

Energy supply. A modern city is a complex complex of various consumers of electrical energy. The bulk of electricity is consumed by industry (about 70%).

AT last years the area of ​​application of electricity for household needs, which averages 20% of total consumption, has expanded markedly. Depending on the size of the city, climatic conditions, the development of industry in it and many other factors, the share of household load and specific power consumption (per 1 inhabitant or per 1 m 2 of living space) can vary widely. For Moscow, for example, the total electrical load of residential and public buildings in the power supply system of the microdistrict is more than 40 W / m 2 of living space in areas with gas cookers, and in areas with electric cookers - more than 50 ... 55 W / m 2.

The transmission of electricity to consumers within residential areas is carried out by underground cable lines, which are laid on the strip between the red line and the building line. Laying underground power cable lines conducted, as a rule, in common trenches. In cases of intersections with main routes and railways, with a lack of free space in the transverse profile of the street, and in some other cases, it is allowed to lay power cables in common collectors, and power cables must be located in the collector above other engineering networks.

Technical operation of the microdistrict equipment. The housing stock is one of the most complex sectors of the urban economy, requiring further improvement in operation and new forms of management using automation, telemechanics and computer technology.

One of the stages of improving the housing economy is the creation of dispatching systems. With the construction of high-rise buildings with high-speed elevators, automatic systems smoke removal and fire alarm, the saturation of the housing sector with a variety of complex underground engineering equipment to improve operation, the need arose for integrated integrated dispatch systems (UDS) for monitoring and managing engineering equipment. ODS can control the operation of all main types of engineering equipment and provides for two-way loud-speaking communication between the dispatcher and passengers in the elevator cabin, with residents in each entrance of the house, with technical rooms microdistrict. ODS can control automatic locking devices (AZU) of entrances, the operation of elevators, emergency lighting of the territory of the DEZ, the temperature of the coolant of the central heating station and boiler rooms. The ODS system provides for subsystems for monitoring water consumption, gas contamination, flooding of premises and collectors, etc. The use of ODS will help to detect and eliminate faults in underground utilities in a timely manner.

The main types of laying heating networks in the Russian Federation today are ground and channel laying. Of the total length of heating networks, which is more than 257 thousand km in one-pipe terms, more than 85% are networks of underground laying in channels. This feature is due to the concentration of the bulk of heating networks in urban areas (ground laying is prohibited within the boundaries of settlements) and the use of outdated technologies (lack of pre- insulated pipes conductors for channelless laying in the domestic market) in thermal networks. Underground (channel) laying in 90% of cases is provided in impassable channels and in 10% of cases - in through and semi-through channels. Ground laying of heat networks is typical for small settlements with a population of up to 30 thousand people, in which heat is supplied from local boiler houses and pipeline diameters do not exceed 300 mm.

Since the 1990s, as is known, new technologies for channelless laying have been actively introduced in Russia using pre-insulated pipelines in polyurethane foam (PPU) insulation (in addition to pipes in PPU insulation, other types of insulation are used for channelless laying, which will be discussed below - approx. auth.). Channelless laying has received the main distribution in large metropolitan areas and cities with a production base (workshops for the production of pre-insulated pipes) within transport accessibility. Basically, channelless laying is used in new construction and reconstruction (change bandwidth pipelines and tracing) of heat networks. At overhaul individual sections of pipelines heat supply organizations usually the existing channel lining (so-called traditional lining) is retained.

In addition, two more types of gaskets used locally should be noted: laying heating pipelines in communication manifolds and cases. The use of collectors for laying heating networks is reflected in cities with dense buildings and cities where traditionally (in order to reduce the area for technical corridors of engineering communications) the laying of various communications was combined. Heating networks laid in collectors are subject to constant diagnostics, have electrochemical protection and, due to the constant access of personnel for current repair in 80-90% of cases they have an extended service life (25-30 years) compared to the "traditional" types of gasket, which is limited only by the corrosion wear of the steel pipeline. Laying in cases (sleeves) is mainly used for laying a heating network under the carriageway of streets, where the planned high-altitude location of neighboring communications or high capital costs do not allow the installation of a through channel.

The main characteristics of laying heat networks are the following indicators.

1. Channel laying is characterized by:

¦ the use of reinforced concrete tray elements manufactured by the industrial method as building structures;

¦ the use of hinged types of insulation;

¦ the presence of cameras on the linear part of heating networks for the installation of fittings, water outlet units and fittings for air release.

The advantages of channel lining include:

¦ protection of pipelines of heating networks and insulation from external damage;

¦ additional protection of the life of citizens in case of pipeline breaks due to the presence of enclosing structures and a drainage system.

2. Channelless laying is characterized by:

¦ lack of enclosing structures for pipelines;

¦ use of pre-insulated pipelines;

¦ lack of cameras for personnel access. The advantages of channelless laying are:

¦ reducing the volume of earthworks during the construction and repair of heat pipelines;

¦ the presence of a system of operational-remote control (for pipelines in polyurethane foam insulation);

¦ the possibility of laying pipelines in conditions high level groundwater and the lack of the possibility of installing drainage networks.

3. Ground laying is characterized by:

¦ laying pipelines of the heating network on supports above the ground using reinforced concrete blocks of the FBS type as supporting structures;

¦ use of hinged isolation from fibrous types of isolation;

¦ arrangement of ground pavilions to protect fittings, water outlets and air vents from unauthorized access.

The main advantages of using ground laying are:

¦ low stresses in the metal of pipelines;

¦ no earthworks during laying, reconstruction and repair of heat pipelines, which reduces capital costs by 60-70%.

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Briefly about thermal networks

Many people imagine what a heating system is, but for a more accessible narrative, a few common truths should be recalled.

Firstly, the heating network does not supply hot water directly to the batteries. Heat carrier temperature in main pipeline on the coldest days it can reach 150 degrees and its direct presence in the heating radiator is fraught with burns and dangerous to human health.

Secondly, the coolant from the network in most cases should not enter the hot water supply system of the building. It is called closed system DHW. Drinking water (from the tap) is used to meet the needs of the bathroom and kitchen. It has undergone disinfection, and the coolant only provides heating to a certain temperature of 50-60 degrees through a non-contact heat exchanger. Usage network water from heat pipelines in the DHW system, at least wasteful. The coolant is prepared at the source of heat supply (boiler house, CHP) by chemical water treatment. Due to the fact that the temperature of this water is often above the boiling point, hardness salts that cause scale are necessarily removed from it. The formation of any deposits on the nodes of the pipeline can damage the equipment. Tap water does not heat up to such an extent and, therefore, expensive desalination does not take place. This circumstance influenced the open systems Hot water supply, with direct water intake, is practically not used anywhere.

Types of laying heating networks

Consider the types of laying heating networks by the number of pipelines laid next to each other.

2-pipe

The structure of such a network includes two lines: supply and return. Preparation of the final product (lowering the temperature of the coolant for heating, heating drinking water) takes place directly in the heat-supplying building.

3-pipe

This type of laying of heating networks is used quite rarely and only for buildings where interruptions in heat are not acceptable, for example, hospitals or kindergartens with permanent children. In this case, a third line is added: a reserve supply pipeline. The unpopularity of this reservation method lies in its high cost and impracticality. The laying of an extra pipe is easily replaced by a permanently installed modular boiler room and the classic 3-pipe version is practically not found today.

4-pipe

Type of laying when both the coolant and hot water of the water supply system are supplied to the consumer. This is possible if the building is connected to distribution (intra-quarter) networks after the central heating point, in which drinking water is heated. The first two lines, as in the case of a 2-pipe gasket, are the supply and return of the coolant, the third is the supply of hot drinking water, and the fourth is its return. If we focus on the diameters, then the 1st and 2nd pipes will be the same, the 3rd may differ from them (depending on the flow rate), and the 4th is always less than the 3rd.

Other

There are other types of laying in the operated networks, but they are no longer associated with functionality, but with design flaws or unforeseen additional development of the area. So, if loads are incorrectly determined, the proposed diameter can be significantly underestimated, and in the early stages of operation, it becomes necessary to increase the throughput. In order not to shift the entire network again, another pipeline of a larger diameter is reported. In this case, the supply goes through one line, and the return line goes through two, or vice versa.

When building a heating network to an ordinary building (not a hospital, etc.), either a 2-pipe or 4-pipe option is used. It depends only on which networks you were given a tie-in point.

Existing methods of laying heating mains

Overhead

The most profitable way in terms of operation. All defects are visible even to a non-specialist, no device is required additional systems control. There is also a drawback: it can rarely be used outside the industrial zone - it spoils the architectural appearance of the city.

Underground

This type of gasket can be divided into three types:

1. Channel (heating network is placed in the tray).

Pros: protection from external influences (for example, from damage by an excavator bucket), safety (if pipes break, the soil will not be washed out and its failures are excluded).

Cons: the cost of installation is quite high, with poor waterproofing, the channel is filled with ground or rain water, which adversely affects the durability of metal pipes.

1. Channelless (the pipeline is laid directly into the ground).

Pros: Relatively low cost, easy installation.

Cons: when the pipeline breaks, there is a danger of soil erosion, it is difficult to determine the place of the break.

1. In sleeves.

Used to neutralize vertical load on the pipes. This is mainly necessary when crossing roads at an angle. It is a heating network pipeline laid inside a pipe of a larger diameter.

The choice of laying method depends on the area through which the pipeline passes. The channelless option is optimal in terms of cost and labor, but it cannot be applied everywhere. If the section of the heating network is located under the road (does not cross it, but runs parallel under the carriageway), channel laying is used. For ease of use, the location of the network under driveways should be used only if there are no other options, because if a defect is found, it will be necessary to open the asphalt, stop or restrict traffic along the street. There are places where the channel device is used to improve security. This is mandatory when laying a network across the territories of hospitals, schools, kindergartens, etc.

The main elements of the heating network

A heat network, to which variety it does not belong, is essentially a set of elements assembled in a long pipeline. They are produced by the industry in finished form, and the construction of communication comes down to laying and connecting parts to each other.

The pipe is the base brick in this constructor. Depending on the diameter, they are produced in lengths of 6 and 12 meters, but on order at the factory, you can purchase any footage. It is recommended to adhere, oddly enough, to standard sizes - factory cutting will cost an order of magnitude more expensive.

Mostly for heating systems are used steel pipes covered with a layer of insulation. Non-metallic analogues are rarely used and only on networks with a greatly reduced temperature curve. This is possible after central heating points or when the source of heat supply is a low-power hot water boiler, and even then not always.

For the heating network, it is necessary to use exclusively new pipes, the reuse of used parts leads to a significant reduction in the service life. Such savings on materials lead to significant expenses for subsequent repairs and rather early reconstruction. It is undesirable to use any type of pipe laying with a spiral weld for heating mains. Such a pipeline is very time-consuming to repair and reduces the speed of emergency repair of gusts.

Elbow 90 degrees

In addition to conventional straight pipes, the industry also produces fittings for them. Depending on the type of pipeline chosen, they may vary in quantity and purpose. In all options, there are necessarily bends (pipe turns at an angle of 90, 75, 60, 45, 30 and 15 degrees), tees (branches from the main pipe welded into it with a pipe of the same or smaller diameter) and transitions (change in pipeline diameter). The rest, for example, the end elements of the operational remote control system, are produced as needed.

Branch off the main network

Not less than important element in the construction of a heating main - shutoff valves. This device blocks the flow of coolant, both to and from the consumer. The absence of shutoff valves on the subscriber's network is unacceptable, since in the event of an accident at the site, not only one building, but the entire neighboring area will have to be turned off.

For air laying of the pipeline, it is necessary to provide for measures that exclude any possibility of unauthorized access to the control parts of the cranes. In case of accidental or intentional closure or restriction of the throughput of the return pipeline, unacceptable pressure will be created, which will result not only in a rupture of the pipes of the heating network, but also in the heating elements of the building. Most dependent on battery pressure. And new design solutions radiators are torn much earlier than their Soviet cast-iron counterparts. It is not difficult to imagine the consequences of a bursting battery - rooms flooded with boiling water require quite decent sums for repairs. To exclude the possibility of control of valves by strangers, it is possible to provide boxes with locks that close the controls with a key, or removable handwheels.

When laying underground pipelines to fittings, on the contrary, it is necessary to provide access for maintenance personnel. For this, thermal chambers are being built. Descending into them, workers can perform the necessary manipulations.

With ductless laying of pre-insulated pipes, the fittings look different from their own standard view. Instead of a control wheel, the ball valve has a long stem, at the end of which there is a control element. Closing / opening occurs with a T-shaped key. It is supplied by the manufacturer complete with the main order for pipes and fittings. To organize access, this rod is placed in a concrete well and closed with a hatch.

Stop valves with reducer

On pipelines of small diameter, you can save on reinforced concrete rings and manholes. Instead of concrete products, rods can be placed in metal carpets. They look like a pipe with a lid attached on top, mounted on a small concrete pad and buried in the ground. Quite often, designers on small pipe diameters suggest placing both valve stems (supply and return pipelines) in one reinforced concrete well with a diameter of 1 to 1.5 meters. This solution looks good on paper, but in practice, such an arrangement often leads to the impossibility of controlling the valve. This happens due to the fact that both rods are not always located directly under the hatch, therefore, it is not possible to install the key vertically on the control element. Fittings for pipelines of medium and above diameter are equipped with a gearbox or an electric drive, it cannot be placed in a carpet, in the first case it will be a reinforced concrete well, and in the second - an electrified thermal chamber.

Installed carpet

The next element of the heating network is the compensator. In the simplest case, this is the laying of pipes in the form of the letter P or Z and any turn of the route. In more complex versions, lens, stuffing box and other compensating devices are used. The need to use these elements is caused by the susceptibility of metals to significant thermal expansion. In simple words, pipe under action high temperatures increases its length and so that it does not burst as a result of excessive load, at certain intervals provide special devices or angles of rotation of the route - they remove the stress caused by the expansion of the metal.

U-shaped compensator

For channelless laying of pipelines, in addition to the angle of rotation itself, a small space is also provided for its operation. This is achieved by laying expansion mats at the bend of the net. The absence of a soft section will lead to the fact that at the time of expansion the pipe will be pinched in the ground and simply burst.

U-shaped compensator with stacked mats

An important part of the designer of thermal communication is drainage. This device is a branch from the main pipeline with fittings, descending into a concrete well. If it is necessary to empty the heating network, the valves are opened and the coolant is dumped. This element of the heating main is installed at all lower points of the pipeline.

drainage well

Discharged water is pumped out of the well with special equipment. If it is possible and the appropriate permission has been obtained, then it is possible to connect the waste well with household or storm sewer. In this case, special equipment for operation is not required.

In small sections of networks, up to several tens of meters long, drainage may not be installed. When repairing, the excess coolant can be dumped using the old-fashioned method - cut the pipe. However, with this emptying, the water must significantly reduce its temperature due to the risk of burns to personnel and the timing of the completion of the repair is slightly delayed.

Another structural element, without which the normal functioning of the pipeline is impossible, is an air vent. It is a branch of the heating network, directed strictly upwards, at the end of which there is a ball valve. This device serves to release the pipeline from air. Without removing gas plugs, normal filling of pipes with coolant is impossible. This element is installed in all high points thermal network. It is impossible to refuse to use it in any case - another method for removing air from pipes has not yet been invented.

Tees with vent ball valve

When installing an air vent, in addition to functional ideas be guided by the principles of personnel safety. When deflated, there is a risk of burns. The air outlet tube must always be directed to the side or down.

Design

The work of a designer when creating a heating network is not based on templates. Each time new calculations are carried out, equipment is selected. The project cannot be reused. For these reasons, the cost of such work is always quite high. However, the price should not be the main criterion when choosing a designer. The most expensive is not always the best, and vice versa. In some cases, the excessive cost is not caused by the laboriousness of the process, but by the desire to fill one's own worth. Experience in the development of such projects is also a considerable plus in the selection of an organization. True, there are times when a company has gained a status and completely changed its specialists: it abandoned experienced and expensive ones in favor of young and ambitious ones. It would be nice to clarify this point before the conclusion of the contract.

Rules for choosing a designer

1. Price. It should be in the middle range. Extremes are not appropriate.
2. Experience. To determine the experience, the easiest way is to ask for the phones of customers for whom the organization has already completed similar projects and not be too lazy to call several numbers. If everything was "on the level", then you will get necessary recommendations, if "not very" or "more or less" - you can safely continue the search further.
3. Availability of experienced staff.
4. Specialization. You should avoid organizations that, despite the small staff, are ready to make a house with a pipe and a path to it. The lack of specialists leads to the fact that the same person can develop several sections at once, if not all. The quality of such work leaves much to be desired. The best option will become a narrowly focused organization with a bias in communication or energy construction. Large civil engineering institutions are also not a bad option.
5. Stability. Fly-by-night firms should be avoided, no matter how tempting their offer may be. It is good if there is an opportunity to apply to the institutes that were created on the basis of the old Soviet research institutes. Usually they support the brand, and employees in these places often work all their lives and have already “eaten the dog” on such projects.

The design process begins long before the designer picks up a pencil (in the modern version, before he sits down in front of the computer). This work consists of several successive processes.

Design stages

1. Collection of initial data.

This part of the work can be entrusted to both the designer and carried out independently by the customer. It is not expensive, but it requires some time to visit a certain number of organizations, write letters, applications and receive answers to them. You should not engage in self-collection of initial data for design only if you cannot explain what exactly you want to do.

1. Engineering survey.

The stage is rather complicated and cannot be performed independently. Some design organizations do this work themselves, some give it to subcontractors. If the designer works according to the second option, it makes sense to select a subcontractor on your own. So the cost can be somewhat reduced.

1. The design process itself.

It is carried out by the designer, at any stage it is controlled by the customer.

1. Project approval.

The developed documentation must be checked by the customer. After that, the designer coordinates it with third-party organizations. Sometimes, to speed up the process, it is enough to participate in this process. If the customer travels together with the developer as agreed, firstly, there is no way to delay the project, and secondly, there is a chance to see all the shortcomings with your own eyes. If there are any controversial issues, it will be possible to control them even at the construction stage.

Numerous development organizations project documentation, offer alternatives her kind. 3D design, color design of drawings is gaining popularity. All these decorative elements are purely commercial in nature: they add the cost of design and do not raise the quality of the project itself. Builders will perform the work in the same way for any type of design and estimate documentation.

Drafting a design contract

In addition to what has already been said, it is necessary to add a few words about the design contract itself. A lot depends on the items in it. It is not always necessary to blindly agree to the form proposed by the designer. Quite often, only the interests of the project developer are taken into account.

The design contract must contain:

• full names of the parties
• price
• period of execution
• subject of the contract

These items must be clearly spelled out. If the date is at least a month and a year, and not a certain number of days or months from the start of design or from the start of the contract. Indicating such a wording will put you in an awkward position if you suddenly have to prove something in court. It should also be given Special attention the name of the subject matter of the contract. It should not sound like a project and a point, but like “design work for the heat supply of such and such a building” or “designing a heat network from a certain place to a certain place”.

It is useful to prescribe in the contract and some points of fines. For example, a delay in the design period entails the payment by the designer of 0.5% of the contract amount in favor of the customer. It is useful to prescribe in the contract the number of copies of the project. Optimal quantity- 5 items. 1 for myself, 1 more for technical supervision and 3 for builders.

Full payment for the work should be made only after 100% readiness and signing of the acceptance certificate (certificate of work performed). When drawing up this document, be sure to check the name of the project, it must be identical to that specified in the contract. If the records do not match even by one comma or letter, you run the risk of not proving payment under this particular agreement in the event of a dispute.

The next part of the article is devoted to construction issues. It will shed light on such points as: features of the selection of a contractor and the conclusion of a contract for the implementation construction works, give an example correct sequence installation and tell you what to do when the pipeline is already laid in order to avoid negative consequences during operation.

Olga Ustimkina, rmnt.ru

9.1 In settlements, for heating networks, as a rule, underground laying is provided (without channels, in channels or in tunnels (collectors) together with other engineering networks).

When justified, it is allowed to lay overground heating networks, except for the territories of children's and medical institutions.

Bypass pipelines of heating networks (when they are in operation for less than one year and serve for uninterrupted heat supply to consumers), used during reconstruction and overhaul, are laid, as a rule, on the ground.

When passing bypass pipelines through the territory of children's and medical institutions, the design documentation must meet the requirements that ensure the safety of operation in accordance with Section 6 and provide for the measures established by Appendix D of these rules.

9.2 The laying of heat networks on the territory not subject to development outside settlements should be provided above ground on low supports.

The laying of heat networks on embankments of public roads of categories I, II and III is not allowed.

9.3 When choosing a route, it is allowed to cross residential and public buildings with transit water heating networks with heat pipeline diameters up to 300 inclusive and a pressure of 1.6 MPa, provided that networks are laid in technical undergrounds and tunnels (at least 1.8 m high) with a drainage well at the lowest point at the exit of the building.

As an exception, the intersection of residential and public buildings with transit water heating networks with a diameter of 400-600 mm is allowed if the requirements of Section 6 are met and measures are taken in accordance with Appendix D of these rules.

If the same requirements are met, it is allowed to install a wall channel (attached to the foundation of the building) channel, while the device of wall channels below the level of building foundations is not allowed.

9.4 Crossing by transit heat networks of buildings and structures of preschool, school and medical institutions is not allowed.

The laying of transit heat networks on the territory of the listed institutions is allowed only underground in monolithic reinforced concrete channels with waterproofing. At the same time, the installation of ventilation shafts, hatches and exits to the outside from the channels within the territory of institutions is not allowed, shutoff valves on transit pipelines must be installed outside the territory.

Branches from the main heating networks for heat supply of buildings and structures related to children's preschool, school and medical institutions and located on their territory are laid in monolithic reinforced concrete channels (including sand-filled ones), in prefabricated reinforced concrete channels using gluing waterproofing and subject to the installation of structures that ensure the tightness of the channel.

The installation of shut-off valves on branches is allowed only with the use of channelless units and chambers with measures to prevent unauthorized access by third parties and ensure gravity drainage from the chambers to the rain sewer system.

9.5 Laying of heating networks at a working steam pressure above 2.2 MPa and a temperature above 350 ° C in tunnels together with other engineering networks is not allowed.

9.6 The slope of heating networks, regardless of the direction of movement of the coolant and the method of laying, must be at least 0.002. With roller and ball bearings, the slope should not exceed

where is the radius of the roller or ball, see Fig.

Slope of heating networks to individual buildings for underground laying, it should be taken, as a rule, from the building to the nearest chamber.

In some areas (when crossing communications, laying on bridges, etc.), it is allowed to accept the laying of heat networks without a slope.

When laying heating networks from flexible pipes, it is not required to provide for a slope.

9.7 Underground laying of heat networks is allowed to be provided together with the engineering networks listed below:

in channels - with water pipes, compressed air pipelines with a pressure of up to 1.6 MPa, control cables intended for servicing heating networks;

in tunnels - with water pipes with a diameter of up to 500 mm, communication cables, power cables with a voltage of up to 10 kV, compressed air pipelines with a pressure of up to 1.6 MPa, pressure sewer pipelines, cold pipelines.

Laying of pipelines of heating networks in channels and tunnels with other engineering networks, except for those indicated, is not allowed.

The laying of pipelines for heating networks should be provided in one row or above other engineering networks.

9.8 In the case of new construction, the horizontal and vertical distances from the outer edge of the building structures of channels and tunnels or the pipeline insulation shell during channelless laying of heat networks to buildings, structures and engineering networks should be taken according to Appendix A. When laying heat pipelines through the territory of industrial enterprises - according to the relevant standards for industrial enterprises.

Reducing the regulatory guidelines in Appendix A is possible with justification and is regulated by the Decree of the Government of the Russian Federation, section I, paragraph 5.

9.9 When reconstructing and overhauling heating networks, under cramped construction conditions and maintaining the boundaries of the buffer zone of the heating network, it is possible to reduce the standard distances to buildings, structures and engineering networks (Appendix A) by taking measures to ensure the safety of existing buildings, structures and utilities (Appendix D).

9.10 The crossing of rivers, highways, tram lines, as well as buildings and structures by heating networks should, as a rule, be provided at a right angle. It is allowed, when justified, to cross at a smaller angle, but not less than 45 °, and for subway and railway structures - not less than 60 °.

9.11 The crossing of tram tracks by underground heating networks should be provided at a distance of at least 3 m from switches and crosses (clearly).

9.12 At underground crossing of railways by heating networks, the smallest horizontal distances in the light should be taken, m:

up to the points and crosses of the railway track and the places where suction cables are connected to the rails of electrified railways - 10;

to arrows and crosses of the railway track with subsiding soils - 20;

to bridges, tunnels and other artificial structures - 30.

9.13 The laying of heat networks at the intersection of railways of the general network, as well as rivers, ravines, open drains, should be provided, as a rule, above ground. In this case, it is allowed to use permanent road and railway bridges.

Channelless laying of heat networks at the underground intersection of railways, highways, main roads, streets, city and district driveways, as well as streets and roads of local importance, tram tracks and metro lines is not allowed.

When laying heating networks under water barriers, as a rule, siphons should be provided.

The intersection of heating networks with metro station structures is not allowed.

At underground crossing of metro lines by heating networks, channels and tunnels should be provided from monolithic reinforced concrete with waterproofing.

Crossing passages within the quarterly development with heating networks from flexible pipes should be carried out in cases with clamp centering supports.

9.14 The length of channels, tunnels or cases at intersections must be taken in each direction by at least 3 m more than the dimensions of the structures being crossed, including the subgrade structures of railways and roads, taking into account Table A.3.

When heating networks cross railways of the general network, metro lines, rivers and reservoirs, shut-off valves should be provided on both sides of the intersection, as well as devices for draining water from pipelines of heating networks, channels, tunnels or cases at a distance of not more than 100 m from the border of the structures being crossed .

9.15 When laying heat networks in cases, anti-corrosion protection of pipes of heat networks and cases should be provided. At the intersection of electrified railways and tramways, electrochemical protection should be provided.

A gap of at least 100 mm must be provided between the thermal insulation and the case.

9.16 At the intersections during underground laying of heat networks with gas pipelines, it is not allowed to pass gas pipelines through the building structures of chambers, impassable channels and tunnels.

9.17 When heating networks intersect water supply and sewerage networks located above the pipelines of heating networks, when the distance from the structure of the heating networks to the pipelines of the intersected networks is 300 mm or less (in the light), as well as when crossing gas pipelines, it is necessary to provide for the installation of cases on pipelines of water supply, sewerage and gas at a length of 2 m on both sides of the intersection (in the light). Cases should include protective covering from corrosion.

9.18 At the intersections of heat networks during their underground laying in channels or tunnels with gas pipelines, devices for sampling for gas leakage should be provided on heat networks at a distance of no more than 15 m on both sides of the gas pipeline.

When laying heating networks with associated drainage at the intersection with the gas pipeline, drainage pipes should be provided without holes at a distance of 2 m on both sides of the gas pipeline, with sealed joints.

9.19 At the inlets of pipelines of heat networks into buildings in gasified areas, it is necessary to provide devices that prevent the penetration of water and gas into buildings, and in non-gasified areas - water.

9.20 At the intersection of above-ground heat networks with overhead power lines and electrified railways, grounding of all electrically conductive elements of heat networks (with a resistance of grounding devices of not more than 10 Ohms) located at a horizontal distance of 5 m in each direction from the wires should be provided.

9.21 Laying of heating networks along the edges of terraces, ravines, slopes, artificial cuts should be provided outside the prism of soil collapse from soaking. At the same time, when buildings and structures for various purposes are located under a slope, measures should be taken to divert emergency water from heating networks in order to prevent flooding of the building area.

9.22 In the area of ​​heated pedestrian crossings, including those combined with the entrances to the metro, it is necessary to provide for the laying of heating networks in a monolithic reinforced concrete channel extending 5 m beyond the clearance of the crossings.