Pre-insulated pipelines technical specifications. Pre-insulated pipelines for district heating systems. The basis for the development of the project are
Pre-insulated pipelines are used in heating networks both for channelless underground laying and for above-ground laying. In the practice of building heating networks, pipelines with polyurethane foam thermal insulation of the "pipe in pipe" type (PPU pipes) are used. The pipeline consists of a pipe, polyurethane foam insulation and a protective sheath (Fig. 3). Steel or polymer (for hot water supply) pipes are used. Polyethylene centering supports are installed between the pipe and the casing.
Pre-insulated piping provides the following advantages over existing structures:
Increased durability (pipeline resource) by 2-3 times;
Reduction of heat losses by 2-3 times;
Reducing operating costs by 9 times (specific damage is reduced by 10 times);
Reducing capital costs in construction by 1.3 times;
Availability of a system of operational remote control over the dampening of thermal insulation.
Pre-insulated pipes have been successfully used for the construction of:
Heating networks;
Hot water supply systems;
Technological pipelines;
Oil pipelines.
Thermal insulation is applied to the entire length of steel pipes and fittings, with the exception of end sections equal to 150 mm for pipes with a diameter of up to 219 mm, and 210 mm for pipes with a diameter of 273 mm or more. The joints are thermally insulated at the construction site, after welding and testing of the pipeline. Insulation of pipe sections with welded joints can be carried out according to one of the methods: installation of insulating shells made of rigid polyurethane foam with the application of a waterproofing material; installation of polyethylene couplings with polyurethane foam filling into the cavity of the coupling.
Protective shells are made in the form of thin-walled pipes from high-density polyethylene. They are intended for pipelines directly located in the ground, providing their water tightness and mechanical protection.
For pipelines located above the ground, a protective sheath made of galvanized steel with a zinc coating thickness of at least 70 microns is used.
Pipelines made of steel pipes are equipped with an on-line remote control system for wetting insulation, consisting of two copper wires (one of which is electrically insulated, and the second without insulation) and an electronic signaling unit. When the insulation becomes wet due to corrosion of the pipe or violation of the integrity of the containment, the ohmic resistance of the system changes, which is recorded by the alarm unit.
The service life of the thermal insulation of pipes and fittings must be at least 25 years. Polyurethane foam does not have a harmful effect on the environment and ensures high-quality operation of the insulation at temperatures up to 130 °C.
The pros and cons of conventional heat supply systems based on steel pipes, used almost everywhere in our country, can be observed by almost all citizens of Russia. These are barely warm (or completely cold) radiators, pipes clogged with scale and rust with a narrowed clearance, rusty smudges wherever water drips at least sometimes, and most importantly, endless repairs with planned and unscheduled shutdowns of heating and water supply. To a large extent, the objective shortcomings of the traditional heat supply system, multiplied by the subjective (so-called "human") factor, are to blame for this.
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That is why in our country there is a gradual replacement of obsolete steel heating systems with new ones everywhere. Advantages of innovative systems:
- simplified installation (no need for laying channels from concrete blocks and additional insulation of pipes)
- low weight of pipes, the ability to avoid obstacles, simple pipe welding technology significantly lower thermal conductivity of pressure pipes and thermal insulation
- financial savings at the construction stage and at the stage of subsequent operation of the system.
These distinctive qualities of pre-insulated systems have already been noticed and appreciated by all large construction and design organizations, the largest heat supply organizations, as well as individual developers.
To date, the number of various options for pre-insulated piping systems on the market, made from different types of materials, is very large.
What usually underlies the choice of a consumer considering various pipes for heating?
First of all, the financial issue. And this is often used by unscrupulous sellers who hide from the buyer that pipes from different manufacturers, with the same outer diameter, often have a different flow area, and, consequently, different wall thicknesses and strengths. Different materials have different MRS (minimum required strength) values, and therefore are able to withstand different pressures and temperatures. Another trick is that cheaper pipes (per linear meter) may have a higher price of fittings and require special fittings for installation, and this difference can increase the overall cost of the pipeline, many times overriding the savings on the pipes themselves.
Another important point is the underestimation of such a parameter as the oxygen permeability of pipes. This parameter greatly affects the efficiency of the heating system. In heating systems with a high coolant temperature, oxygen diffusion through the pipe walls leads to an increase in the intensity of cavitation processes that destroy those elements that are made of metal - i.e. shut-off valves, impellers and rotors of pumps and other parts. In low-temperature heating systems, the penetration of oxygen entails the activation of the activity of aerobic microorganisms, as a result of which siltation of the system occurs in a short time, narrowing the flow area of the pipeline to a state of complete obstruction.
made of polymeric materials, manufacturers use various techniques to reduce oxygen diffusion - for example, aluminum reinforcement or coating with special materials with low oxygen permeability. , manufactured by Thermaflex (Thermaflex), for heating are covered with a layer of special anti-diffusion material, these pipes are easily recognizable by their bright red color. This oxygen-protective layer prevents the diffusion of oxygen, and therefore, Flexalen systems are not only not subject to corrosion themselves, but also protect other system equipment from this negative factor.
Consider the molecular structure of polybutene. Polybutene, being a polymer, contains many branches in the molecular chain. Additional bonds between carbon atoms give the material strength and flexibility (which polypropylene does not have) and thermoplasticity (which makes it possible to weld pipes, as opposed to cross-linked polyethylene), making it the best material for heating systems .
A distinctive feature is the insulation made of foamed polyethylene. The insulation is applied continuously, foaming is done with isobutane, the thermal conductivity of which is much lower than that of air. The number of closed pores in such thermal insulation reaches 98%. The polyurethane foam used for the production of pre-insulated pipes by other manufacturers has an open cellular structure, which leads to strong water absorption by thermal insulation if the outer protective casing or inner pipe is damaged - and, as a result, to a significant decrease in thermal insulation properties. Flexalen pipes do not have this drawback - even if the outer layer is broken, the insulation does not absorb moisture during the entire service life. When creating a protective casing, the molten low-pressure polyethylene enters through the extruder directly onto the insulated pipe and is firmly welded to it. This increases the overall strength and tightness of the pipe.
As a result, Flexalen pre-insulated pipes become the optimal solution for creating heating and hot water systems.
Briefly, the advantages of Thermaflex pre-insulated pipelines are as follows:
- Polybutene, which forms the basis of the Flexalen pipe, has a lower thermal conductivity than the materials of other analogues.
- The thermal insulation of Flexalen pipes is made of foamed polyethylene, which has high thermal insulation properties.
- Full tightness and the highest moisture insulation among similar pre-insulated pipes.
- Pipes have high flexibility, which greatly simplifies and reduces the cost of pipeline installation.
- Flexalen pipes can be welded, which avoids the use of press fittings that narrow the flow area in similar systems.
- Flexalen piping systems are self-compensating, which eliminates the need to use compensators, simplifies and reduces the cost of installation.
- Inexpensive fittings and accessories reduce the overall cost of installing a piping system.
Flexalen heating pipes often have a slightly higher cost per linear meter than analogues, but they greatly benefit in the total installation cost, and as a result, the final cost of the pipeline is lower than in the case of using similar pipes for heating from other manufacturers. The costs for subsequent operation are also markedly reduced.
Specifics of External Network Design Using Preinsulated Pipes
A. N. Cheban, Engineer, Lecturer at Moscow Institute of Architecture
keywords: external network, heat line, heating network, remote control, preinsulated pipe, polyurethane foam insulation
The article presents the main stages of design of heating network in polyurethane foam insulation, gives a detailed overview of design documentation structure, contents of sections, including installation diagram for pipe laying and operative dispatch remote control arrangement.
Description:
A. N. Cheban, engineer, lecturer at Moscow Architectural Institute
The article presents the main stages of designing heat networks in polyurethane foam insulation, discusses in detail the composition of the project documentation, the content of the sections, including the wiring diagram for laying pipes and the diagram of the operational remote control system.
Experience in the operation of heat networks has shown high reliability and efficiency of pre-insulated pipelines. In connection with the expansion of the list of factories producing this type of product, as well as with the improvement of pipe production technology and installation work, the cost of laying networks from pre-insulated pipes has significantly decreased in recent years. In view of this, both for newly built urban facilities and for the reconstruction of existing networks, pre-insulated pipes are increasingly being used. The most widely used pipes are in polyurethane foam (PPU) insulation.
The design of heat networks in polyurethane foam insulation is carried out in accordance with SP 124.13330.2012 “Heat networks. Updated edition of SNiP 41-02-2003 "and SP 41-105-2002" Design and construction of thermal networks of channelless laying from steel pipes with industrial thermal insulation from polyurethane foam in a polyethylene sheath ".
The basis for the development of the project are:
for newly constructed urban facilities - technical specifications (TS) and connection conditions from the operating organization (in Moscow - this is PJSC MOEK), terms of reference (TOR) from the customer;
for objects of reconstruction and overhaul (buildings or existing heating networks) - TK.
With an increase in thermal power, it is necessary to obtain new connection conditions from the operating organization (in Moscow, this is PJSC MIPC) and the terms of reference from the customer.
A change in the requirements of the TOR at the design stage must be carried out in the prescribed manner upon submission of the operational area with mandatory reapproval by the operating organization.
Typically, the term of the TU is 3 years, unless otherwise specified.
A change in the requirements of technical specifications at the design stage must be carried out in the prescribed manner on the proposal of the customer with mandatory reapproval in the operating organization.
If necessary, the TOR and TS are accompanied by as-built documentation for the areas of interface with existing heat pipelines or measurement drawings with the signature of the operational area.
These documents must contain clear information on the technical parameters of the networks being designed with an exact indication of the scope (boundaries) of the design. When formulating the requirements of the TOR, a reference to the documents approved by the company (SRO standards, technical regulations, etc.) is allowed. The term of the ToR is 3 years, unless otherwise specified.
Project
When working on project documentation, the designer must choose the most efficient option for laying heat networks that meets the requirements of the technical specifications of the operating organization and the technical specifications of the customer, ensure uninterrupted, reliable and safe heat supply to consumers.
The preferred type of laying for pipelines in polyurethane foam insulation is channelless laying.
Laying in channels should be used if necessary to unload the pipe from excessive soil pressure, when crossing roads, parking lots and other objects to ensure the possibility of repairing the pipe without tearing, as well as in cases provided for by SNiP (passing near buildings, crossing the territories of medical and preventive, children's educational establishments, etc.).
When designing, the most rational routing option should be adopted. To ensure the cost-effectiveness of solutions, existing channels should be used as much as possible, repairing them if necessary.
The project includes the following main drawings.
1. The plan of heat networks (Fig. 1) is carried out on the engineering and topographic plan (geo-baseline) on a scale of 1:500. Heat networks are applied to the geo-base in green, characteristic points are indicated at the angles of rotation and at the places of installation of fixed supports, fittings installation nodes, at the places of branching of heat pipelines. When designing water removal (outlet) from heating networks, it is necessary to obtain technical conditions (in Moscow - this is the State Unitary Enterprise "Mosvodostok") for discharging water into the city drainage system.
Before proceeding with the detailed study of the heating network project, it is necessary to perform a calculation for the strength and rigidity of the heat pipes. The calculation allows you to evaluate the correctness of the chosen scheme for laying heating networks and eliminate the likelihood of accidents. This calculation is part of the project and requires further approval.
2. The profile of heat networks (Fig. 2) is a vertical section along the axis of the underground route of the heat network, on which all existing, designed and inactive engineering networks are indicated.
The profile of heat networks is built vertically on a scale of 1:100 and horizontally on a scale of 1:500. Characteristic points are applied to the profile, the distances between them, the type of coating, ground marks (design and full-scale), marks of the top and bottom of the insulation in the event that the heating network is laid channelless. In the event that the heating network is laid in the channel, the top and bottom of the channel are marked on the drawing. The depth of the trench must be calculated taking into account the concrete preparation. The profile indicates: the slopes of the heating networks and their length, the size and material of the pipes, as well as a detailed plan indicating all the elements of the heating networks. The profile of thermal networks corresponds to the situation on a geo-based basis.
After a detailed study of the plan and profile of heating networks, it is necessary to carry out a number of coordination procedures in various organizations, depending on the specifics of laying the route.
In the department of underground structures of the State Budgetary Institution "Mosgorgeotrest". This agreement allows you to link the designed heating network with existing or planned facilities and urban engineering networks in the process of their further operation.
In the operating organization of the heating network, it is necessary to agree on the chosen direction of the heating main. In the case of a forced relocation of existing city networks, it is necessary to additionally obtain technical conditions for the relocation.
In the operating organizations of city networks, all intersections and parallel laying with city networks must be coordinated.
3. The installation diagram (Fig. 3) of laying steel pipes in polyurethane foam insulation (PUF insulation) is a diagram of series-connected elements indicating the length and diameters of the heat pipes. The elements include: straight sections with a minimum length of up to 3.0 m and a maximum length of 11.0 m, tees, shut-off fittings, bends, fixed supports, transitions. Both standard elements and non-standard elements can be used in the project. All non-standard elements are manufactured at the factory and delivered to the construction site after prior agreement between the design organization and the manufacturer.
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Figure 3 |
Compensation for thermal elongation of heat pipes in polyurethane foam insulation is carried out due to the natural angles of rotation of the route or special compensatory devices in the form of bellows, lens or stuffing box compensators. When designing a heating main with natural compensation for large displacements, shock-absorbing pads (polyethylene mats) are installed, the number and location of which are indicated on the wiring diagram.
The installation scheme is carried out not only for steel heat pipelines in polyurethane foam insulation, laid without channels, but also for laying heat pipelines in a channel, ground laying or temporary laying of heat pipelines for the period of construction of the main section of the heating network (hereinafter referred to as the bypass. - Note. ed.).
When designing heat pipelines in an impassable or through channel, it is necessary to develop a scheme for laying out the channel floor slabs (Fig. 4).
When developing a scheme for uninterrupted heat supply to consumers, it is necessary to ensure a safe tie-in into an existing heat pipeline. To do this, it is necessary to develop a wiring diagram indicating the distances, installation locations for high and low supports and tie-in of the heat pipeline bypass into the existing heating network (Fig. 5).
In such cases, temporary chambers are designed (Fig. 7), in which a tie-in is made into the heat pipes. Upon completion of construction, the chamber, bypass and tie-in point are dismantled. This is indicated in the specification and dismantling list.
4. Operational remote monitoring system (SOODK) is designed to control the state of the PPU heat-insulating layer and detect areas with high humidity.
The diagram shows the signal wires in the supply and return heat pipes. The main signal wire is a tinned wire, located on the right in the diagram in the direction of the coolant. All side branches for other consumers are included in the tinned wire break.
Installation of end terminals is carried out at the beginning and at the end of the heating main. The terminal installed in the central heating point or individual heating point has an exit to the stationary terminal. When pairing projects (previously released and new), a double terminal is installed at the junctions of heating networks, the functions of which can include both merging and separating the system for operational remote control of projects. If the length of the heating main is more than 300 m, it is necessary to install intermediate terminals.
The operational remote control system provides measurements from both ends of the heat pipeline section.
The drawing of the remote control scheme must necessarily contain a specification indicating the nodes and places (characteristic points) of their installation.
The operational remote control system includes:
- signal conductors in the heat-insulating layer of pipelines, passing along the entire length of the heating network;
- terminals for connecting devices at the points of control and switching of signal conductors;
- cables for connecting signal conductors to terminals at control points, as well as for connecting signal conductors in pipeline sections where bare elements are installed;
- detector (stationary 220 V or portable 9 V);
- locator (pulse reflectometer);
- isolation tester (control and installation tester).
Each project must submit the following specifications:
- custom specification for steel pipes in polyurethane foam insulation for ordering at the manufacturing plant in accordance with GOST 30732–2006;
- general specification, which indicates the total length of the pipe, the number of branches, fittings and reinforced concrete elements;
- specification for the designed bypass and a dismantling list for the subsequent elimination of the bypass.
All specifications in the project must comply with the developed drawings and be agreed with the operating organization and the customer.
If the project provides for the dismantling of the existing heating network, then the project must contain a dismantling list, which indicates the steel and reinforced concrete elements of the network to be dismantled.
The design of thermal networks in polyurethane foam insulation requires from the designer not only the skills of a draftsman, but also knowledge regarding the use of new modern materials that are necessary for the design of thermal networks. This will make it possible to develop the optimal solution for the design of the heating network and draw up a specification that allows for a complete timely completion of the facility, which is especially important for carrying out installation work on time.
Literature
- SP 124.13330.2012 “Heat networks. Updated edition of SNiP 41–02–2003”. M., 2012.
- SP 41-105-2002 "Design and construction of thermal networks of channelless laying from steel pipes with industrial thermal insulation from polyurethane foam in a polyethylene sheath". M., 2002.
- Guidelines for the use of pipes with industrial insulation made of polyurethane foam produced by MosFlowline. 2014.
- Typical album TS-01-03 "Channel-free laying of heat pipes in polyurethane foam insulation." LLC "Kanalstroyproekt" M., 2003.
High-quality components and pre-insulated pipes for heating networks are a guarantee of long-term operation of communications in any climatic zone. The very technology of production of these products and qualified installation in compliance with the technology ensures the perfect operation of the heating system for a long time without the need for repairs.
For those who are familiar with the "sandwich" system for chimneys, the pipe pre-insulated with PPU will seem like a "related" product. The same cylinder in a wider blank, but the gap between them is filled not with mineral or basalt wool, but with foamed and baked synthetic filler. At the moment, this development is considered the most high-tech achievement in the industry.
This method of insulating pipes for heating networks in practice confirms its effectiveness and reliability - the high efficiency of the pipeline with a service life of at least 25 years. The pre-insulated product is able to withstand short-term amplitude jumps of the coolant at a record low ambient temperature in winter. The specific shape of the product with internal insulation is used not only for hot water, but also for the transport of other liquid and gaseous media.
The main pipe is steel, the outer layer is not always solid metal with galvanization, especially when this is not necessary. The polyurethane foam layer can be protected by a flexible sheath wrapped around the porous filler in the form of a spiral. Each layer of multilayer products is manufactured according to a special technology, equipped with a special control system for the moisture content of the insulating layer and possible defects in the trunk segment.
The pipe "in the pipe" does not look like an assembly, but like a whole product, thanks to the tight adhesion of the heat-insulating filler. Pre-insulated products are recommended for use in practical installation in heating systems. The outer layer is designed to protect PPU from getting wet, and also provides resistance to external influences.
Components of pre-insulated pipes
The pipe in polyurethane foam insulation is produced from the following components:
1. Rod base or functional steel pipe. The release of certified products is carried out in accordance with GOST:
- 8731;
- 8733-77;
- 10704;
- 10706;
- 20295;
- PB 03-75-94, etc.
2. The inner thermal insulation layer is produced from polyurethane foam raw materials from leading manufacturers. Izolan, Dau, Elostokam and Huntsman have moved from domestic products to a high-tech level, whose products are not inferior to imported systems. Their ready-made fillers have a long warranty period under maximum external and internal stress, even water hammer or short-term temperature rises up to 150°C.
3. The outer shell or protective casing is designed to protect the PU foam layer from damage and moisture penetration. The lack of moisture access from the outside ensures the safety of all layers of pre-insulated pipes - from corrosion of the core base and polyurethane crumbling. The polyethylene sheath is produced in accordance with GOST 16330 from thermo-light-stabilized raw materials of high density in black. It is possible to use a shell of a different type - according to other standards.
The most popular pre-insulated steel pipes (PPU-PE GOST 30732):
- 57*3,5-1;
- 57*3,5-2;
- 76*3,5-1;
- 76*3,5-2;
- 89*3,5-1.
Product quality requirements
All processes for the production of pipes with PPU are carefully controlled for compliance with standardization standards. For example, foaming and curing polyurethane foam is a fast process where deviations from the norms are unacceptable. Literally in seconds, the raw material takes on its final form and is ready for use. There are polyurethane foam of different density and rigidity - within 1 kg / m³. Its isolated porous cells also have different sizes - up to 1 mm in diameter.
Requirements for thermal insulation filler:
- water absorption of PPU by volume - within 10% (tested at 1.5 hour boiling);
- density - within 60 kg / m³;
- compressive elasticity - from 0.3 MPa (within 10% deformation in all directions);
- the change in the length of the product after heating to 110°C should be minimal - up to 3%.
Mandatory testing for the main quality indicators is carried out not only by the pre-insulated pipes themselves, but also by all components. Before implementation, they are tested in the laboratory for density, the size of closed pores and thermal conductivity.
It is interesting! The foam in the insulating layer looks like a yellowish confectionery cream after whipping. But this homogeneous paste has a dense fine-meshed structure, which does not settle, does not stick together. The ends of the PPU insulation do not have a protective layer, and it is obvious that thermal protection is no more than 1/3 of the total thickness of the product.
One of the characteristics of pre-insulated pipes with polyurethane foam is the adhesion of the outer and inner layers. To do this, technological standards must be met:
- cleaning the surface of the steel pipe from rust, with the obligatory formation of roughness, with which foamed polyurethane foam has better adhesion;
- maintaining a given temperature regime for uniform foaming of raw materials;
- treatment of the inner shell with a discharge for greater adhesion to the foam filler.
Due to the obtained properties, pre-insulated pipes are used in the construction of main oil, gas and steam pipelines. It is also widely used in heating networks for hot water supply and in various technical pipelines - in hot production shops.
Important! PPU was produced in several ways, but today the practice has become established - to take carbon dioxide and freon 141b (F-141b) as a basis. This mixture is dangerous, therefore it is used only in an industrial way, due to the explosiveness of the likelihood of fire. But foaming agents give the maximum effect when obtaining the necessary contents in the annulus. All norms are regulated by a single standardization - GOST 30732-2001.
Benefits of pre-insulated PU foam pipes
There are many positive qualities and similar products.
- Installation of communications in a short time with minimal labor costs.
- Reducing heat loss to a minimum (2% vs. 40%).
- Increasing the efficiency of the heating main to the maximum possible indicators.
- Increasing the service life of communications by 3-5 times (relative to the old technology).
- Ability to reduce the cost of frequent overhauls by minimizing breaks in pre-insulated pipes and their joints.
- The operation of the remote control system (UEC).
- There is no need for grounding and arrangement of the drainage system.
- Protection of pipes from corrosion and other external negative factors.
- Pipes in polyurethane foam are less susceptible to destruction from chemicals and aggressive environments.
- PPU safety for the environment.
- Maximum preservation of the temperature of the transported substance, due to the absence of "cold bridges".
- Minimum thermal conductivity with a small layer of thermal insulation.
Manufacturing technology of preinsulated pipes
A well-established process involves pouring foaming raw materials into the gap between the outer shell and the steel pipe. The technology is thought out in such a way that the production of products for heating plants is carried out with a minimum of operations.
PPU foam with minimal thermal conductivity is poured over a steel pipe, which is fixed with a hoist on a special assembly table. Centralizers and SODK control the molding process of products. The product is placed in the outer shell with an electric winch. The conveyor shifts the product into a heat chamber - for further thermostatic control.
Fan heaters heat the inner surface of the pipe up to 350 ° C with a hot air jet - the hot base for pouring polyurethane foam is ready. A special device rotates the pipe on a rotary axis. On both sides, the ends of the product are provided with plugs with small drainage gaps for air to exit the wire.
Plugs are fixed with screws to prevent the outflow of uncured raw materials from the space between the pipes. The pouring machine is regulated on the control panel, where the main pouring parameters are set. They depend on the type of raw materials, the length and shape of the pipes. The watering can for injection of PPU of the filling machine is brought to the pipe opening and the mixture is quickly injected. A further goal is the hardening of the thermal insulation layer in the annulus.
Further, the products are transferred to the site of control and laboratory quality control. Certified products are sorted, labeled and packaged. Upon completion of the waterproofing process at the ends of pipes for heating networks, they are stacked on racks - up to 5-6 products.
Note! In Europe, the basic requirements for pre-insulation with PU foam for laying underground utilities were regulated by the European standard - EN253. It was also reflected in the accompanying documentation.
In the Russian Federation, manufacturers of pre-insulated products, technologists and developers have developed a single Russian standard - GOST 30732-2001. Standardization came into force on 01.07.2001. The regulatory document reflects the requirements for PPU insulation products and components for pre-insulated pipes. The operation of pre-insulated products in communications involves taking into account the thermal conductivity of gases. This figure increases as the temperature rises. However, this indicator is not able to significantly affect the pipes themselves and the insulating layer of polyurethane foam.
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The uninterrupted functioning of a number of human life support systems depends on the targeted delivery of services, the centralized transportation of common goods: heat, water. For this purpose, an extensive network of supply pipelines is being created. Mostly engineering communications are laid underground. This allows not to clutter up the city infrastructure, not to interfere with automobile and other transport.
When laying underground pipelines, close attention is paid to the maintainability of the route, reducing heat losses and increasing the corrosion resistance of the pipe assortment. You can buy pre-insulated pipes (PI-pipes) on the website www.ankirsplast.by, look at the prices for products.
Design features of pre-insulated pipes
Modern technologies have made significant changes in the design and installation of heating plants and public water conduits. Pre-insulated analogues have replaced the pipes, which undergo a labor-intensive operation of insulation after installation. Structurally, the product consists of three elements:
- An internal electric-welded pipe that provides the flow of the fluid flow provided for by the project. It is manufactured by the direct seam method from low-alloy structural steel of various grades and grades. Thickness of a standard size provides long use at the set parameters of a working environment: temperature, pressure.
- Outer thin-walled steel pipe. In the standard size with a large cross-section, the carrier pipeline is placed in a centered manner. The purpose of the shell is waterproofing, preventing mechanical damage to the communication artery.
- Polyurethane layer located in the cavity between two metal surfaces. Filling a limited space is carried out with a polymer in a foamed state. After hardening, high adhesion of the component to the steel is ensured. Polyurethane acts as a heat-insulating component of the finished product.
Preferences of the new technology over the traditional way of laying highways
Products with pre-insulation are used in the construction of main pipelines for central heating, hot and cold water supply. The diameter of the inner pipes coincides with the range of previously used ones, which makes it possible to replace entire sections that have served their deadlines during the repair of pipelines. The following advantages of pre-insulated products contribute to the displacement of outdated methods of laying main supply lines:
- corrosion resistance;
- impact strength indicators;
- thermal insulation characteristics and sound absorption;
- ease of installation: welded qualities and reduced labor costs for additional insulation;
- the possibility of laying in the ground without the construction of special boxes (channels);
- reliability and durability of communication;
- lower annual maintenance costs;
- fast return on investment.
Channelless pipe laying
Builders owe the introduction of a channelless method of laying highways to the appearance of polyurethane foam insulation. Pipes insulated with polymer and placed in a metal sheath are highly resistant to mechanical damage. In combination with corrosive inertness, this makes it possible to lay such products directly into the ground. The bottom of the trench is pre-filled with sand. A technological cushion is created that prevents the track from sagging, which creates unwanted stress on the metal.
Installation of pre-insulated pipes without arranging protective channels is carried out using special fittings that provide connection of measured sections, changes in the directions of highways. Welded joints of the inner pipe are covered with a polyurethane cover, and the integrity of the waterproofing outer shell is achieved by polyethylene sleeves.
The development of electronics makes it possible to connect heating mains, water supply communications to operational remote control systems. Precise instruments detect violations of the tightness of the outer layer. Timely response to identified damage prevents the destruction of the inner pipe, reduces the likelihood of emergency leaks. Special requirements are imposed on the channelless laying of pipes under the carriageway of highways. They are regulated by the relevant provisions of SNIP.
