Overhead laying of pipelines. Constructive solutions for heating networks for underground and above-ground installation. Above-ground installation of heating networks.

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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 last years Channelless installation began 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 underground laying Heating networks are carried out on an unplanned territory; local planning of the earth's surface is carried out. This is done for the purpose of draining surface water. Elements of heating networks (external 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-quarter tunnels are laid together with water networks with a diameter of up to 250 mm and a natural gas pipeline with a pressure of up to 0,005 MPa and a diameter of 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 pavement.

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

At channelless installation and in non-passable channels it is produced 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 compensator 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.

When laying heating networks underground and for air installation, a crane is used. 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 a populated area (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.

Pipelines Heating 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 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 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:

Direct laying of pipes in the ground (channelless).
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 canal 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) with pipelines not large diameter and 1 brick (250 mm) for pipelines of large diameters.

The walls are erected only from ordinary brick of a grade not lower than 75. It is not recommended to use sand-lime brick due to its low frost resistance. 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 weak soils, additional iron is placed on the concrete base 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.

KL type channels 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 if available large quantity pipes They are laid under the pavements of large highways, in large areas industrial enterprises, in areas adjacent to thermal power plant buildings. 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 a 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: the complication of repair work and the difficulty of 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. The 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, 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 the operating 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 minimal maintenance time. 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 intersection of such a route with pedestrian paths install special bridges. 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.

§ 2. Methods of underground, above-ground and above-ground laying and their technical and economic indicators

The installation of sanitary and technical communications in areas of permafrost can cause the soil to thaw due to the heat generated by the pipelines. As a result, the stability of both the pipelines themselves and buildings may be compromised. Methods for laying sanitary and technical communications must be linked to the methods of construction of buildings and structures and depend on the properties of the foundation soils and other factors, the most important of which is the location of the network route in relation to the built-up area and its architectural and planning solution.

There are the following types of sanitary communications laying: underground, above-ground and above-ground. These types of gaskets, in turn, can be single or combined.

Ground and overhead laying Due to the absence of contact of pipes with the ground and limited heat release into the soil, the foundations disturb to the least extent the natural thermal regime of permafrost soils. Such gaskets clutter the territory of populated areas, complicate the construction of passages, the organization of snow protection and snow removal.

Underground laying It is advisable to carry out within the boundaries of the settlement in order to achieve maximum improvement of the territory. Water supply and sewerage networks can be laid directly in the ground, and heating networks and steam pipelines can be laid in special channels. If there are such channels, it is advisable to lay water supply, sewerage and electrical cables in them.

The underground installation of heating networks is very expensive and requires special measures to maintain the thermal regime of permafrost soils at the base of the networks. So, for example, the cost 1 linear m channel for district heating in the conditions of Norilsk averages 300 rubles. The cost of a two-tier channel for the combined installation of a heating network, water supply, sewerage and electrical cables under the same conditions averages about 450 rubles. behind 1 linear m. Therefore, underground installation of heating networks is advisable only in compact buildings with multi-story (4-5 floors) buildings and in conjunction with other communications.

If the development is carried out with two- and three-story buildings with gaps, then the underground installation of heating networks usually turns out to be economically infeasible. In such cases, above-ground laying is most often used along the facades and attics of buildings, and between buildings - along overpasses, fences and fences. In this case, water supply and sewerage can be laid in the ground without channels. If the soils of the base of the pipes are subsidence, then to ensure their stability it is necessary to replace the soils with non-subsidence ones to a depth determined by thermal engineering calculations.

For small villages, if it is possible to route the network within blocks without crossing streets or with a minimum number of intersections, the most economical option is to lay heating networks above ground in ring insulation or in insulated ducts together with a water supply system. In this case, the sewerage system must be laid in the ground without channels.

In soils that subsidence during thawing, especially in soils that transform during thawing into a fluid-plastic or fluid state, when laying underground pipelines, an artificial foundation is necessary. The cost of such a foundation is directly dependent on the depth of thawing of the soil under the pipes.

When laying pipelines in soils that do not settle and do not lose their bearing capacity when thawed, the decisive condition is to protect them from freezing by reducing heat loss. In this case, the depth of placement is increased to 1.5-2.0 m; greater depth is undesirable, as it makes it difficult to detect pipeline failure sites and repair them, both in summer and especially in winter.

In order to reduce heat loss and the size of the taliks under the pipes, underground laying of water supply and sewerage systems is used in thermal insulation: in boxes made of wood or reinforced concrete filled with sawdust or mineral wool, in a ring box made of foam concrete, mineral wool, felt impregnated with resin. All of these types of thermal insulation fail to achieve their goal when the insulating material is wet. Local faults in waterproofing (and therefore thermal insulation) lead to thawing of the base and uneven settlement of pipelines, which is the most undesirable. Restoring thermal and waterproofing during repairs is a complex and labor-intensive process. The use of boxes creates additional difficulties in detecting and eliminating leaks. Any leak entails a violation of thermal insulation. The cost of thermal insulation usually exceeds the cost of an artificial foundation for water supply and sewerage. Therefore, the widespread use of thermal insulation for water supply and sewer pipelines when laying them in the ground is impractical.

Let's consider some designs of pipeline foundations laid in the ground.

Soil foundation(Figure IV-1). Ice-saturated local soils at the base of the fuel pipeline are replaced by non-subsidence soils with a low filtration coefficient to the calculated thawing depth. Sandy, gravel-sandy soils in some cases are compacted by preliminary thawing. For replacement, light sandy loams and fine-grained silty sands in a thawed state are used; in this case, an admixture of pebbles, gravel, crushed stone up to 40.....-45% or local dehydrated and compacted soil is desirable. A waterproofing layer of adobe concrete or clay with a thickness of 25-30 cm.

The width of the artificial foundation is assumed to be equal to the width of the trench, and the height is determined by calculation.

In the absence of a leak, the radius of thawing from heat releases from water supply or sewer pipelines on average does not exceed 1.2 m. If we take into account the increased intensity of thawing of soils that replace ice-saturated soils, then the depth of replacement will not exceed 1.5 m. It must be assumed that in many cases the soil foundation will be economically profitable and technically feasible.

Flat base It is used to reduce the unevenness of subsidence during thawing of subsidence soils and is made in the form of longitudinal logs in two logs. To prevent the tracks from warping during subsidence, as a result of which the pipeline is destroyed, they must be securely fastened.

Floating base used in ice-saturated soils and is a continuous flooring of plates laid across the trench; This type of foundation is quite reliable, but cannot be widely recommended due to the high cost and consumption of a large amount of timber.

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Rice. IV-2. Pipeline on a pile foundation. 1 - pipeline; 2 - log (timber) ∅30 cm on dowels (staggered joints); 3 - piles ∅30 cm through 3m with recess on 3m below the active layer; 4 - gaskets through 10 cm; 5 - backfilling with local soil

Pile foundation(Fig. IV-2) is used in highly subsidence soils. Driving piles into permafrost soil requires labor-intensive and expensive work on steaming the soil or drilling wells. Piles have to be placed frequently, because in pipes that carry a large load from the soil, significant bending moments occur on the supports. Such bases are characterized by high cost.

Underground overpasses(Fig. IV-3) due to their high cost, they are used in exceptional cases, for example, for sewerage in subsidence soils that thaw to great depths, when the route passes near a building with large heat releases, built according to methods I or IV and located higher in the relief.

The issue of using one or another type of basis is resolved by comparing technical and economic indicators.

To eliminate the possibility of intense movement of supra-permafrost water flow along underground pipelines, clay concrete bridges are used across the trenches. The lintels cut into the frozen base and walls of the trenches on 0.6-1.0 m. The distance between the lintels is determined depending on the longitudinal slope so that the pressure at the lintel does not exceed 0.4-0.5 m; Typically this distance ranges from 50 to 200 m.

In pebble, gravel and other well-filtering soils, the installation of dams is not advisable, since the flow of supra-permafrost water easily bypasses them.

Laying in earthen beads

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Rice. IV-4. Laying pipes in earthen beads. 1 - pipeline; 2 - thick clay concrete layer 20 cm; 3 - local soil; 4 - sand and gravel layer; 5 - local dewatered and compacted soil

This method of laying (Fig. IV-4) is used under fairly favorable permafrost-soil conditions, in the absence of thermal insulation materials, and the pipeline route should pass through an undeveloped area. This type of gasket has several advantages:

no need to produce labor-intensive excavation for digging trenches;
pipe leaks are easier to detect and fix;
filtering of supra-permafrost water along the pipes is eliminated;
the presence of a talik around the pipes allows longer interruptions in the movement of water through them than with ground and above-ground installations;
there is no need for thermal and waterproofing of pipes.

Main disadvantages this method is excessive cluttering of the territory and complexity of crossings. In addition, this creates conditions for greater snow cover in the area.

Underground laying of pipelines in channels

Laying pipelines in underground channels is a relatively expensive type of network construction; nevertheless, in some cases, channel laying is advisable, taking into account not only one-time capital investments, but also operating costs. The feasibility of combined laying of communications in underground channels in comparison with a single underground one should be confirmed by the cost of construction attributed to 1 m2 living space, and reliability in the operation of utility networks. Combined laying is usually justified in unfavorable climatic and frozen soil conditions.

Channels can be pass-through (semi-pass-through) and non-pass-through, single-tier and two-tier. In two-tier channels, the lower tier of which is passable, the upper tier can be either semi-passable or non-passable. The design of the channel with a semi-through upper tier is cumbersome and high cost. The single-tier channel design is the most economical and convenient to use.

In the case of installing different types of channels in a populated area (which must be justified), it is necessary, based on the conditions of industrialization of construction, to achieve a minimum number of standard sizes of elements.

Impassable up to 0.9 m channels (Fig. IV-5) can be used in short sections (house outlets and inlets, road intersections, etc.) while ensuring stability conditions and operating requirements. Non-passable channels should be constructed with minimal penetration into the ground (no more than 0.5-0.7 m from the floor to the ground surface). They must have a removable cover for cleaning channels, inspecting and repairing pipelines. The longitudinal slope of non-passable channels to ensure water drainage along the bottom must be at least 0.007.

Passage channels with a height of at least 1.8 m(Fig. IV-6) must have dimensions that provide free passage through them for inspection and repair of pipes, fittings and electrical cables.

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Rice. IV-7. Reinforced concrete two-tier passage channel. 1 - sewerage; 2 - heating network: 3 - water supply; 4 - shelves for electrical and communication cables; 5 - sand, δ = 10 cm; 6 - clay concrete, δ = 20 cm; 7 - replaced soil (calculated thickness)

With significant channel depths and large heat releases from communications, taliks formed under the channels can reach significant sizes. In such cases, to reduce the penetration of heat into the base, based on a technical and economic comparison with other options, the feasibility of installing two-tier channels is revealed (Fig. IV-7). In the lower passage tier of such a channel, a sewer pipeline and electrical cables are placed, in the upper - non-passable or semi-passable - heating network and water supply pipes are laid.

When laying a combined sewer and water supply system, water valves must be placed in special chambers or sections isolated from the sewer pipeline.

In order to prevent destruction of both the canals themselves and nearby buildings and structures from thawing of the soil at the base, it is necessary:

thermally insulate pipelines, minimizing their heat generation as much as possible;
ventilate the channels in winter to remove heat so that the soils at their base that have thawed over the summer are completely frozen;
arrange waterproofing along the bottom of the canal, preventing water from penetrating into the foundation soils. The foundations under the canals should be made of non-subsidence or low-subsidence soils.

In addition to replacing subsidence soils, it is possible to use preliminary thawing and compaction of foundation soils. Channels must be made of reinforced concrete, reinforced cement or other effective material. The construction of channels made of wood or concrete can be allowed with special justification, since concrete channels are expensive and do not meet the strength requirements for uneven foundation settlements, and wooden ones are susceptible to rotting, require big works for waterproofing, they are silted with the smallest particles of soil; If they have sewerage, they create unsanitary conditions for the water supply.

Ventilation of channels is arranged natural and artificial (forced). Natural is carried out by installing ventilation holes along the top of the channel at a distance 20-25 m depending on the dimensions of the channel and communications laid in it (Fig. IV-8). The efficiency of natural ventilation can be increased by installing exhaust shafts in buildings located near the canal; in this case, the distance between the holes on the channel for air flow can be increased to 100-150 m.

Discharge of emergency or waste water from the canal should be carried out from its end part, using a longitudinal slope, or from intermediate water collectors (waterproof pits) by pumping water out with pumps.

Heat and steam pipelines placed in channels should be moved as far as possible from the bottom of the channel; they must be in ring thermal insulation (for example, foam concrete with asbestos-cement plaster and waterproofing). The use of plastics with increased heat and waterproofing properties (foam plastic, polyethylene, etc.) for these purposes has great prospects.

Technical and economic feasibility of laying sewer networks in canals together with networks for various purposes compared to a single underground installation is identified based on a comparison of construction and operating costs attributed to 1 m2 living space, as well as assessing the stability of networks, their durability and thermal impact on nearby buildings and structures.

Ground laying of pipelines

The above-ground type of installation usually includes pipelines laid on low supports. In this case, between the pipe and the ground surface there must be a ventilated space of at least 30 cm, which is necessary to reduce heat release into the foundation soils and prevent snow drifts.

Ground laying of pipelines should be used outside the built-up areas of populated areas (as it is the cheapest), in low-lying and swampy sections of the route, in places with heavily ice-saturated permafrost soils.

In the built-up area, ground installation is allowed if there are a small number of pipeline intersections with driveways and sidewalks. Pipelines are thermally and waterproofed. The use of combustible materials both for the manufacture of boxes and heat-insulating backfills for steam pipelines and heating networks at a coolant temperature of 90 °C and above is not recommended by fire regulations. Slag backfill should also not be widely used due to possible destruction metal pipes corrosion when the slag is moistened.

Wooden boxes, being in conditions of variable humidity, are deformed, the filling is blown out, spills out and is easily moistened. Waterproofing boxes with roll materials does not achieve the goal, since roll coverings are easily damaged. Therefore, boxes made of reinforced concrete are more reliable, but their cost with backfill is higher than the cost of ring heat and waterproofing of pipes.

In the case of combined installation, mainly for ease of use, thermal insulation is carried out independently for pipelines for various purposes.

The base for above-ground pipelines can be bulk sand-gravel or any other non-subsidence or low-subsidence soil, laid without disturbing the natural moss and vegetation cover during the work. In the case of subsidence soils of the natural foundation, it is necessary to replace them with non-subsidence ones to a depth determined by calculation.

Special supports are installed on an artificial soil foundation under the pipelines.

Leg supports of the transverse beams have a small height, as a result of which, when the supports settle, the thermal insulation of the pipes falls on the ground, easily becomes moistened and deteriorates. The installation of common supports for several pipelines is not recommended, since with uneven load the tracks give uneven settlement.

Town supports(Fig. IV-9) are a more advanced type of wooden supports; they make it easy to straighten the profile of pipelines in the event of small subsidence of the foundation by wedging the elements of the towns.

Reinforced concrete intermediate supports sliding and roller type (Fig. IV-10) are more economical and durable than wooden ones. Their disadvantage is the difficulty of straightening pipelines when embankments settle; To level the base, the pipeline must be lifted and the supports removed.

Fixed(anchor) supports(Fig. IV-11) are made of wood, concrete and reinforced concrete. At wooden supports the pipes are secured to the support beams with bolts or pins.

Frame fixed supports require large volumes of work to develop and excavate soil from pits. Therefore, they can be recommended in cases where the use of pile supports is impractical (active layer of high thickness, high-temperature frozen soils characterized by low freezing forces, boulder crushed soils, etc.).

Massive concrete supports are arranged for pipelines of large diameters and during the construction of pipelines in 2 stages. For fastening metal parts nests are left in the concrete mass, which must be filled with concrete of the lowest grades until the construction of the second stage pipeline. Otherwise, water accumulates in them, which, when frozen, can tear the concrete mass. To avoid thawing of foundation soils due to exotherm during concrete hardening, as well as from heat flow through the support body, supports are laid on the bottom of the pit sand cushion thick 20-30 cm.

In general, ground laying in the conditions of the Far North is the most economical type of laying sanitary and technical communications (excluding sewerage).

Aboveground pipeline laying

Aboveground laying of pipelines is carried out on overpasses, on pile supports rising above the terrain (Fig. IV-12), along the walls of buildings, attics and fences. The above-ground type of pipeline laying is used when crossing roads, hollows, ravines and streams, in factory areas, and in places with heavily ice-saturated permafrost soils.

Similar to above-ground installation, pipes are laid in ring thermal insulation or in insulated boxes.

Overpasses can be made of wood, reinforced concrete and metal. Metal trestles are used in flammable areas. The production of reinforced concrete overpasses is difficult and their cost is high. Therefore, pile and frame wooden trestles are mainly used.

Advantages of above-ground installation:

pipes and ducts do not cause snow deposits and do not interfere with snow removal;
the issue of intersections with driveways and walkways is successfully resolved;
pipes and their insulation are not exposed mechanical damage from transport and pedestrians;
pipelines are not subject to snow drifts and are easily accessible for inspection and repair.

Disadvantages of above-ground installation:

high cost compared to land installation;
inconvenience of installing fittings, especially fire hydrants;
more significant heat losses than during ground installation due to high wind speeds and the absence of snow deposits on the pipes;
pipes laid along building facades, overpasses and fences spoil the appearance of a populated area;
When laying pipes along the walls of buildings, the principle of priority for the construction of sanitary communications is violated.

Technical and economic indicators for some types of gaskets are given in Appendices 1 and 2.

Heated water from a thermal power plant or a district boiler house is supplied to consumers via external heating networks by pumps for the centralized supply of heat to industrial enterprises, residential buildings and public buildings.

The route of heating networks in cities and other populated areas laid in technical lanes designated for utility networks parallel to the red lines of streets, roads and driveways. The route of heating networks runs between the roadway and a strip of green space. Inside microdistricts and blocks, the route of heating networks must also pass outside the roadway.

For heating networks in cities and other populated areas, underground installation is provided: in non-passable and through channels; in city and intra-block collectors together with other engineering networks and without installing channels (heating networks with a diameter of up to 500 mm).

In the territories of industrial enterprises, heating networks are laid on separate low and high supports or overpasses. Joint installation of above-ground heating networks with process pipelines, regardless of the parameters of the coolant and the parameters of the environment in the process pipelines,

Most often, heating networks are laid in non-passable channels made of precast reinforced concrete (), which are single-cell, double-cell and multi-cell.

Rice. 142. Non-passable CL channels: a - single-cell, b - double-cell; 1 - tray element, 2 - sand preparation, 3 - floor slab, 4 - cement dowel, 5 - sand

Rice. 143. Laying of heating networks: a - in a non-passage channel with bitumen-perlite insulation, b - channelless, C - circulation pipeline, D - hot water pipeline, X - cold water pipeline, T - return pipeline of the heating system, GP - leading pipeline of the heating system

On, and shows one of the options for intra-block installation of heating networks in non-passable channels. The heating system pipelines are laid in one channel, the hot water supply system pipelines in the other, and cold water supply pipelines run between the channels directly in the ground.

When laying heating networks in the groundwater zone, the outer surfaces of the walls and ceilings of the heating channels should be covered with bitumen insulation, and drainage should be installed to lower the groundwater level along the route.

Thermal insulation is provided for heating network pipelines, fittings, flange connections, compensators and pipe supports, regardless of the coolant temperature and installation methods. Temperature on the surface of the thermal insulation structure of the pipeline in technical underground and basements of residential and public buildings should be no more than 45 ° C, and in tunnels, collectors, chambers and other places accessible to maintenance, no more than 60 ° C.

Currently, the industry produces industrial bitumen perlite thermal insulation heat pipes, which is applied to the pipes by pressing at the factory. Such insulation is produced in two types: for laying heat pipelines and water supply networks in a channelless manner directly in the ground and in non-passable channels (see a); for laying heating pipes and water supply networks in technical undergrounds of buildings, passage channels, as well as indoors.

Bitumen-perlite insulation is a mixture of expanded perlite sand, petroleum bitumen and a passivating additive that reliably protects pipelines from corrosion. A covering layer of two layers of fiberglass glued to bitumen mastic or SKS-65 latex is applied on top of the bitumen-perlite insulation.

To weld heat pipes on the route, the ends of the pipes, 200 mm on each side, must not be insulated.

Channelless combined installation of pipelines for heating networks, hot and cold water supply with bitumen-perlite insulation (b) is allowed in all soils, except subsidence. When laying pipelines without channels in dry soils with a filtration coefficient Kf equal to 5 m/day or more, drainage is not required. In all other cases, it is necessary to arrange associated drainage. Channelless installation of pipelines for heating networks and hot water supply is used on routes. Chambers or channels should be provided in places where turns and expansion joints are installed.

The depth of installation of pipelines with bitumen-perlite insulation in areas of channelless installation must be at least 0.8 m from the planned surface of the earth to the top of the insulation in order to ensure strength and protection of the cold water supply from freezing.

The passage channel for a large number of pipes is shown in Fig. 144.

Rice. 144. Laying heating networks in the passage channel:

1 - supply pipelines, 2 - sliding support, 3 - steel beam, 4 - return pipeline, 5 - pipeline insulation, 6 - side walls of the channel, 7 - drainage tray

Such channels have large cross sections, which allows service personnel monitor and repair pipelines. Passage channels are installed mainly in the territories of large industrial enterprises and at the outlets of heat pipelines from powerful thermal power plants. The walls of the 6 passage channels are made of reinforced concrete, concrete or brick; The covering of passage channels is usually made of prefabricated reinforced concrete.

In the passage channels it is necessary to install a tray 7 for water drainage. The slope of the canal bottom towards the water drainage site must be at least 0.002. Support structures for pipes located in the passage channels are made of steel beams 3, cantilevered

straight sections in walls or mounted on racks. The height of the passage channel should be about 2000 mm, the width of the channel should be at least 1800 mm.

Pipelines in channels are laid on movable or fixed supports.

Movable supports serve to transfer the weight of the heat pipes to the supporting structures. In addition, they provide movement of pipes that occurs due to changes in their length with changes in coolant temperature. Movable supports can be sliding or roller.

Rice. 145. Supports: c - sliding, b - roller, c - fixed

Sliding supports (, a) are used in cases where the base for the supports can be made strong enough to withstand large horizontal loads. Otherwise, they resort to roller supports (, b), which create smaller horizontal loads. Therefore, when laying pipes of large diameters in tunnels, roller supports should be installed on frames or on masts.

Fixed supports ( ,c) serve to distribute pipeline extensions between expansion joints and to ensure uniform operation of the latter. In the chambers of underground channels and during above-ground installations, fixed supports are made in the form of metal structures, welded or bolted to pipes. These structures are embedded in foundations, walls and channel ceilings.

To absorb thermal elongations and relieve pipes from temperature stresses, bent and stuffing box compensators are installed on the heating network.

Rice. 146. Bent expansion joints

Bent expansion joints () U- and S-shaped are made from pipes and bends (bent, steeply curved and welded) for pipelines with a diameter of 50 to 1000 mm. These compensators are installed in non-passable channels, when inspection of laid pipelines is impossible, as well as in buildings with channelless installation. The permissible bending radius of pipes in the manufacture of expansion joints is 3.5-4.5 times the outer diameter of the pipe.

Bent U-shaped expansion joints are placed in niches. The dimensions of the niche in height coincide with the dimensions of the channel, and in plan they are determined by the dimensions of the compensator and the gaps necessary for the free movement of the compensator during temperature deformation. The niches where compensators are installed are covered with reinforced concrete slabs.

Rice. 147. Stuffing box compensators: a - one-sided, b - two-sided; 1 - body. 2 - glass, 3 - flanges

Stuffing box expansion joints are manufactured single-sided ( , a) and double-sided ( , b) for pressures up to 1.6 MPa for pipes with a diameter of 100 to 1000 mm. Stuffing box compensators are small in size, have a large compensating capacity and offer little resistance to the flowing fluid.

Stuffing box expansion joints consist of a housing 1 with a flange 3 on the widened front part. A movable glass 2 with a flange is inserted into the compensator body for installing the compensator on the pipeline. To prevent the stuffing box compensator from leaking coolant between the rings, stuffing box packing is placed in the gap between the body and the glass. The stuffing box is compressed by a flange liner using studs screwed into the compensator body. Compensators are attached to fixed supports.

The chamber for installing valves on heating networks is shown in Fig. 148.

Rice. 148. Chamber for installing valves on heating networks:

1 - branch of the supply main pipeline, 2 - branch of the return main pipeline, 3 - chamber, 4 - parallel valves, 5 - pipeline supports, 6 - return main pipeline, 7 - supply main pipeline

When laying heating networks underground, 3 rectangular underground chambers are installed to service shut-off valves. Branches 1 and 2 of the network to consumers are laid in the chambers. Hot water is supplied to the building through a pipeline laid on the right side of the channel. The supply 7 and return 6 pipelines are installed on supports 5 and covered with insulation.

The walls of the chambers are made of bricks, blocks or panels, the ceilings are prefabricated from reinforced concrete in the form of ribbed or flat slabs, the bottom of the chamber is made of concrete. The entrance to the cells is through cast-iron hatches. To descend into the chamber, staples are sealed under the hatches in the wall. The height of the chamber must be at least 1800 mm. The width is chosen so that the passages between the walls and pipes are at least 500 mm.

Aboveground pipeline laying

Overhead laying of pipelines through internal plant roads and railway access roads is carried out in compliance with the following basic requirements. The intersection of roads by pipeline networks is accepted at an angle of 90° to the axis of the road, and in cases where it is impossible to meet this requirement, it is allowed to reduce the intersection angle to 45°C.

Heating networks are laid by above-ground or underground (extremely rare) methods. When laying above ground, pipelines are laid on overpasses or on free-standing supports. With the underground method, pipelines are laid in non-passable channels.

Simple suspended supports are used for overhead laying of pipelines on overpasses with guy wires in self-compensation areas or during installation U-shaped expansion joints. The maximum spans between suspended supports are additionally checked by calculating the maximum permissible load on the support.

In industrial buildings and structures, it is necessary to provide for the above-ground laying of pipelines (along walls, columns and other building structures), and if such placement is not possible, it is allowed to provide for the laying of pipelines in underground channels. overhead pipeline laying

When laying pipelines above ground, in order to avoid freezing of the transported medium at subzero outside temperatures, a continuous supply of steam and condensate must be provided (especially for small-diameter pipelines) or associated heating of the condensate pipelines must be provided.

Exhaust and secondary steam lines and condensate lines are, whenever possible, laid together with existing fresh steam lines, water lines and process pipelines. When the groundwater level is high, above-ground installation of steam and condensate pipelines should be preferably used.

Aboveground pipeline laying was carried out mainly on overpasses and high supports. Some domestic factories also used lowered laying (2-2.5 m from the ground level).

As a rule, above-ground installation of pipelines should be provided on overpasses or free-standing supports.

Aboveground laying of pipelines for transporting heated products should be provided on free-standing supports and overpasses with a height that eliminates the thermal impact of pipelines on permafrost foundation soils.

When laying pipelines above ground, depending on their characteristics and operating conditions, the following types of supports are used: fixed and movable (sliding, roller and suspended). Movable supports allow the pipeline to move during temperature deformations.

Aboveground laying of pipelines along racks is convenient to use, since the pipelines are accessible for repair and monitoring; however, this method is expensive, and therefore wide application not received.

For turbulent mode (pipeline diameter 200-- 300 mm, g 80°C) Besh recommends taking following values k in w/m hail dry soil, sand -- 5.8 moist damp soil -- 5.8 + 11.6 soil containing groundwater, quicksand -- 17.4 87.0. For overhead laying of pipelines in still air = 12--14 W/m deg, and in rain and wind A = 14--23 W/m deg.

Note The mass of snow and ice should be taken into account in calculations only when laying pipelines above ground outdoors.

When laying pipelines above ground through roadways and streets, the height of the pipelines (clear) from ground level to the outer surface of the insulation must be at least 4.5 m, except for laying through the railway track, when the distance from the rail head to the outer surface of the insulation should not be less than 6 m (for normal gauge). When the distance from the bottom point of the pipeline insulation to the ground level is less than 2 m, then transition stairs must be installed for the passage of people. When installing pipelines on an overpass, the edges of the latter must be kept away from combustible buildings and premises. explosive production not less than 5 m from the ammonia storage warehouse - 10 m from the axis of the railway track - 3 and from travel and pedestrian roads.

Foreign practice in the operation of chemical and oil refineries also confirms the feasibility of above-ground installation of pipelines.

Each of the three types of above-ground pipeline installation (high, low and low) has its own technical and economic indicators, which serve as a criterion for choosing the optimal type of installation in specific conditions, including combined high with low, low with low, etc.

When laying a pipeline above ground, in order to maintain the brine temperature at least 2-3 °C, depending on local climatic conditions, the pipeline should be thermally insulated or also heated. When laying the brine pipeline above ground in the southern regions, its thermal insulation is not provided.

Overhead laying of pipelines is carried out on overpasses, pile supports, along the walls of buildings and when crossing roads and ravines, in factory territories. Pipes are laid in ring thermal insulation or in insulated boxes. The above-ground laying of the pipeline is carried out on a bedding with embankment. When laying above ground, heat and waterproofing of pipelines is provided.

The disadvantage of above-ground pipeline installation is the need to allocate a strip of irrigated or arable land at least 4 m wide for permanent use.

At the intersections of overpasses on which pipelines with flammable gases are laid, railways and internal plant tracks, valves, water collectors, stuffing box compensators, flange connections and other mounting components in which leaks may occur during operation should not be installed on pipelines. In these cases, pipelines are installed only by welding. The underground or above-ground installation of pipelines with flammable gases together with telephone, power and lighting cables is not allowed.

When laying pipelines above ground on overpasses or free-standing supports, joint laying of pipelines of all categories with process pipelines for various purposes is allowed, with the exception of laying in overpass-type galleries, as well as cases where such laying contradicts the requirements of other safety rules.

Defects are eliminated when the excess pressure is reduced to zero and the compressor is turned off. During pneumatic strength tests, a protected (safe) area must be established both indoors and outdoors. The minimum zone distance must be at least 25 m for overhead pipeline installation and at least 10 m for underground installation. The boundaries of the zone are fenced off.

Deviations from the design position of the supports when laying pipelines above ground should not exceed 5 mm for the displacement of the foundations relative to the alignment axes, 10 mm for the deviation of the support axes from the vertical, and +5 mm for the elevation of the top of the supports.

Overhead laying of pipelines on high supports is dangerous look work, therefore it is necessary to strictly comply with all safety rules and requirements of the work project.

When laying pipelines above ground through passages, the height of the pipelines (in clear) from the ground level to the outer surface of the insulation must be at least 5 m, except for cases of laying through the railway track, when the distance (in clear) from the rail head to the outer surface of the pipeline insulation must be at least 6 m (for normal gauge).

When laying together overhead pipelines of large and small diameters in order to increase the distances between supporting structures (overpass masts), it is recommended to a) use large-diameter pipes Vu = 500 mn or more) as load-bearing structures to create support or hang small-diameter pipes from them b) apply local stiffening of pipes of small and medium diameters by welding stiffeners.

Fittings and instruments for ground and above-ground pipeline laying are placed in chambers-wells, chambers-booths, chambers-thermal centers.

When laying pipelines above ground, paint and varnish coatings are used, the most common of which are the following.

Aboveground laying of pipelines on low supports is provided only in cases where traffic, lifting mechanisms and equipment are not expected to move in the area of the territory through which pipelines are laid.

The overhead pipeline laying scheme is carried out in such a way as to make maximum use of the plant territory intended for the creation of fire breaks between objects.

U-shaped expansion joints have a large compensation capacity (up to 700 mm) and are used primarily for above-ground laying of pipelines, regardless of their diameter.

Aboveground laying of pipelines is carried out on overpasses, pile supports, along the walls of buildings and is used when crossing roads and ravines, in factory territories. Pipes are laid in ring thermal insulation or in insulated boxes.

The assignment for the development of drawings of canals and overpasses is drawn up on the basis of the routing of the main technological lines and regulatory guidelines for underground and above-ground laying of pipelines. As a rule, water conduits and sewer lines are laid in intra-shop channels. The cross-sectional dimensions of the channel should ensure ease of installation and repair of pipes, placement of separate outlets to technological equipment, placement of primary elements of instrumentation and instrumentation (diaphragms, water meters, etc.) and installation of shut-off valves.

The laying of pipelines can be underground (in through-channels - tunnels, non-through-through channels and cable-free - directly in the ground), above-ground on supports and above-ground - on overpasses. Ground and above-ground laying of pipelines is preferable, since it provides the possibility of visual monitoring of the condition of pipelines and facilitates their installation and repair. Laying pipelines in the ground, especially gas pipelines, is dangerous because leaks can travel significant distances from the point of damage to the pipeline, and determining the location of the leak is difficult and common.

Before filling the pipelines with coolant, they are thoroughly washed and the tightness of the bolts on the flange connections is checked, the operation of shut-off valves, air bleed valves, drainage devices, packing of seals for compensators, valves and valves, the presence of sleeves for thermometers and fittings for pressure gauges in the required places, accessibility and uncluttered premises of subscriber inputs. When laying pipelines above ground, the condition of the supporting structures and the correct installation of movable supports are also checked.

Underground or above-ground laying of pipelines with flammable gases together with telephone, power and lighting cables is prohibited.

Fire hydrants are installed on main sections of networks. Overhead pipelines It is advisable to lay it in earthen ridges, buried channels using continuous backfill, as well as in semi-buried channels. Aboveground laying of pipelines is carried out on low supports, masts, overpasses or in ventilated undergrounds of buildings, in heated rooms and insulated ducts.

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