Main pipes for heating are pre-insulated. Pre-insulated pipelines. Advantages of pre-insulated pipes with polyurethane foam

Previously insulated pipelines are used in heating networks both for ductless underground installation and for above-ground installation. In the practice of constructing 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 thermal insulation and a protective shell (Fig. 3). Steel or polymer (for hot water supply) pipes are used. Centering supports made of polyethylene are installed between the pipe and the shell.

Pre-insulated pipelines provide the following advantages over existing structures:

Increased durability (pipeline service life) by 2-3 times;

Reduction of heat losses by 2-3 times;

Reduced operating costs by 9 times (specific damage rate is reduced by 10 times);

Reduction of capital costs in construction by 1.3 times;

Availability of a system for operational remote control over the humidification of thermal insulation.

Pre-insulated pipes have been successfully used for construction:

Heat supply networks;

Hot water supply systems;

Technological pipelines;

Oil pipelines.

Thermal insulation is applied along the entire length steel pipes and shaped products with the exception of end sections equal to 150 mm for pipe diameters 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 done using one of the following methods: installing insulating shells made of rigid polyurethane foam with the application of waterproofing material; installation of polyethylene couplings with polyurethane foam poured into the cavity of the coupling.

Protective shells are made in the form of thin-walled pipes made of high-density polyethylene. They are designed for pipelines directly located in the ground, ensuring their waterproofness and mechanical protection.

For pipelines located above the ground, a protective shell made of galvanized steel with a zinc coating thickness of at least 70 microns is used.

Pipelines made of steel pipes are equipped with a system for operational remote monitoring of insulation wetting, consisting of two copper wires(one of which is electrically insulated, and the second without insulation) and an electronic alarm unit. When the insulation gets wet due to pipe corrosion or a violation of the integrity of the protective shell, the ohmic resistance of the system changes, which is recorded by the alarm unit.

The service life of 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 insulation performance at temperatures up to 130 °C.

Magazine “Heat Supply News” No. 5, 2005, www.ntsn.ru

IN AND. Manyuk, President; Ph.D. I.L. Maizel, Executive Director, Association of Manufacturers and Consumers of Pipelines with Industrial Polymer Insulation, Moscow

On February 28, 2005, a conference was held in Moscow on the experience of production, design, construction and operation of heating pipelines with polyurethane foam insulation, organized by the Association of Manufacturers and Consumers of Pipelines with Industrial Polymer Insulation. More than 60 organizations from different regions Russia. These are, first of all, manufacturers of pre-insulated pipes, construction organizations who actively use them when laying heating networks, manufacturers of raw materials and equipment, as well as the largest research and design institutes, incl. and foreign partners. At the conference, an interested exchange of views took place on the problems that have existed in this area over the last decade, when this area of ​​heat supply has developed massively.

The general opinion of the conference participants was the following - to ensure the reliability, durability and energy efficiency of heating network structures, pipelines with polyurethane foam insulation should be used as widely as possible for both underground ductless installation and above-ground installation. There are practically no alternatives to this direction in heat supply today.

In his report “Experience of mass production and use of pipelines with polyurethane foam insulation in Russia,” the executive director of the Association, Ph.D. I.L. Meisel, summed up more than ten years of experience in the production and use of such pipelines in construction. If in 1994 in Russia there were only a few enterprises producing pipes pre-insulated with polyurethane foam, then by the beginning of 2005 there were about 70. Thus, in the Central Federal District there are about 30 such enterprises (including in Moscow and Moscow region - 21 enterprises), in the North-Western - 8, in the Volga region - 9, in the Ural region - 9, in the Siberian region - 9, in the South - 4. The total capacity of the enterprises is about 10 thousand km per year of both main and distribution pipelines (from 57 mm and below, up to 1200 mm). However, due to a lack of financing, the capacity of enterprises is used on average by 30-60%.

It was emphasized that for the successful use of pipelines with polyurethane foam insulation, the Association and its members have developed regulatory documentation. The main documents are as follows:

Interstate standard GOST 30732-2001 “Pipes and shaped products steel with thermal insulation made of polyurethane foam in a polyethylene shell";

ST 4937-001-18929664-04 “Steel pipes and fittings with thermal insulation made of polyurethane foam with a steel protective coating”;

SP 41-105-2002 “Design and construction of ductless heating networks made of steel pipes with industrial thermal insulation made of polyurethane foam in a polyethylene shell”;

RD 10-400-01 “Standards for strength calculations of heating network pipelines”;

Computer programs "START";

SNiP 41 -02-2003 “Heat networks”;

SNiP 41-03-2003 “Thermal insulation of equipment and pipelines”;

SP 41-107-2004 “Design and installation of underground hot water supply pipelines from PE pipes with thermal insulation from polyurethane foam in a polyethylene shell”, etc.

In order for the use of new products to be successful, it is necessary to pay close attention to the quality of manufactured products, increasing the level of design and installation with the mandatory use of operational remote monitoring (ODC) systems during operation.

I.L. Meisel emphasized that to improve the level of design and construction of heating mains, the Association has created training centers through which hundreds of design and construction specialists have passed (every year about 700-800 people study at the training centers of NPO Stroypolymer and JSC MosFlowline).

New approaches to the development of SNiP 41-02-2003 “Heat networks” were reported in his report by the head of the department of VNIPIEnergoprom Association OJSC, Doctor of Technical Sciences. G.H. Umerkin. Special attention paid attention to such concepts as the probability of failure-free operation of the system, the availability factor (quality) of the system, the survivability of the system, etc.

The report of the Director of Heating Networks of JSC Lenenergo E.G. was devoted to increasing the reliability of the operation of heating networks. Khachaturova. He noted that the use of polyurethane foam-insulated pipes in the heating networks of JSC Lenenergo began in 1993 and 123 km have already been laid.

Previously, pipes were used without operational remote monitoring (ORC) systems. It was only in 2003 that the enterprise made an unequivocal decision - not a single meter of PPU-insulated pipeline should be laid without a monitoring system. A real tool has appeared that allows you to control product quality at all stages, starting from incoming inspection of supplied products. Installers now know that they can hand over a facility only if the insulation resistance meets the standard.

During storage and laying of pipelines, the insulation can be damaged, therefore, after installing the pipe in the trench, before insulating the joint, its resistance must be measured again. If it is normal, then the metal of the joint is treated with an anti-corrosion coating, the joint is insulated with foam and the resistance is measured again. Since 2004, all joints must be treated with an anti-corrosion coating. For this purpose, mastic produced by NPK Vector is used. The ends of the thermal insulation are also coated with mastic from the same company to protect against moisture in unfavorable conditions. weather conditions and even when pits are flooded.

Head of the operation service of the Teplosetservis enterprise V.I. Kashinsky focused on the experience of operating steel pipelines with polyurethane foam insulation in the heating networks of Mosenergo OJSC for the period from May 1996 to March 2004. During this period, the following malfunctions were noted during the operation of 218.4 km of pipelines with PPU insulation:

Damage to steel pipes from internal corrosion - 4%;

Weld defects - 5%;

Defects in sealing butt coupling joints - 23%;

Errors during the installation of operational remote control systems (ORC) - 5%;

Destruction of elements for connecting the SODC (terminals, contact boxes, connecting cables, etc.) - 26%;

Mechanical damage during excavation work - 3%;

Failure of SODK devices is 1%.

Thus, there is no damage from external corrosion (for old traditional designs of heating networks in non-passing channels with thermal insulation made of mineral wool materials, damage from this type of corrosion was about 75%), from internal corrosion - no more than 4%. The main type of damage is vandalism and lack of coordination between the various organizations carrying out excavation work.

After training and experience gained by specialists installation organizations defects when sealing coupling joints are gradually decreasing. Specific damage rate of steel pipelines (number of damages per year per km) for the period from 1999 to 2003. for channelless gaskets in PPU insulation was 0.0107, and for other types of gaskets - 1.244, i.e. differs by two orders of magnitude. (The speaker agreed with the remark that the comparison is not entirely correct, since the damageability of relatively new ductless pipelines in polyurethane foam insulation and “old” heating mains of traditional types, which also have a significantly greater length, was assessed - approx. ed.).

Director of OJSC "Association VNIPIEnergoprom" and President of NP " Russian heat supply» V.G. Semenov emphasized the need to improve the quality of products. Having dwelled on the undoubted advantages of laying heating networks with pipes with PPU insulation, especially in significant savings heat, the speaker recommended strengthening control at all stages of design, production and construction of heating networks.

The chief specialist of Mosproekt OJSC, A.V. Fisher, gave a report on the experience of designing heating networks. He noted that in Moscow, flexible pipes made of cross-linked polyethylene with polyurethane foam insulation are widely used in the reconstruction and new construction of heating networks after central heating systems in hot water supply and heating systems, which significantly (up to 50 years or more) increases the service life and reliability of heating networks and the entire heating system as a whole. To be able to use such pipes more widely, it is necessary to develop a “Code of Rules for the Design of Heating Networks Using Pipes from polymer materials", which legalizes the abolition of the use of shut-off and drain valves on branches to individual buildings and a number of other issues that significantly facilitate and reduce the cost of installation and further operation of heating networks based on cross-linked polyethylene.

Issues of strength calculations for heating network pipelines with polyurethane foam insulation were raised in the report of Deputy Director of NTP Truboprovod V.Ya. Magalifa. He touched on the use computer programs"START" in these calculations. The adjusted methodology for calculating the wall thickness of tee branches, leading to their significant increase, caused a heated debate. According to V.Ya. Magalifa's methodology includes the strength calculation standards set out in RD 10-400-01, approved by Gosgortekhnadzor. However, these thicknesses do not correspond to GOST 30732-2001 “Steel pipes and fittings with thermal insulation made of polyurethane foam in a polyethylene sheath.”

Achievements in the production and use of steel pipes with PPU insulation were reported in the reports of the chief engineer of Mos-Flowline CJSC V.G. Kukhtin and director of JSC Sibpromkomplekt (Tyumen) G.A. Smash. The need for a complete set of heating networks (production of shaped elements, shut-off valves, materials for insulating joints, ODSK, etc.) was noted. For example, JSC MosFlowline, in addition to pipes and fittings, produces and supplies for installation ball shut-off valves and, since 2005, compensators (starting and bellows).

A number of speakers presented products manufactured by their organizations for the production and installation of heating networks using polyurethane foam insulated pipes.

Director of PC "Polymer-Complex" V.I. Timokhin and head of the representative office of "Cannon" (Italy) A.Yu. Bobkov was told about the filling machines by the General Director of NPP Izolan LLC (Vladimir) M.Ya. Tsarfin and representative of VIKORD LLC A.V. Shapovalov (Tolyatti) about raw materials systems for polyurethane foam, the president of the ENEKOS company (St. Petersburg) - about ball valves D u 300-800 mm, representative of LLC " Olmax" - about manual extruders for welding polyethylene casings.

V.A. Polyakov (MosFlowline CJSC) emphasized in his message the need to install systems for operational remote monitoring of the moisture state of polyurethane foam and spoke about new multi-level detectors for recording moisture.

In conclusion, the President of the Association V.I. Manyuk recommended that the conference participants make wider use of the experience accumulated by the Association members in the production and use of polyurethane foam-insulated pipes in heating networks.


Pipes ISOPROFLEX 0.6 MPa
CASAFLEX
Pipes ISOPROFLEX 75A 1.0 MPa
Steel pipes in polyurethane foam insulation
Steel pipes in VUS insulation
ISOPROFLEX Quadriga and Tandem pipes
Convectors
Steel panel radiators
Movable supports according to GOST 14911-82, OST 36-94-83
Movable supports for heating networks series 5.903-10-13 issue 8-95
Fixed supports of heating networks series 5.903-10-13 issue 7-95
Movable supports series 4.903-10 issue 5
Fixed supports series 4.903-10 issue 4

The economic component of using pipes for centralized heating in our cities is determined by the quality and durability of pipelines and thermal insulation. In Russia, all pre-insulated pipes that are produced can be divided into two types - polymer pipes and steel. The heat-insulating layer is PPU polyurethane foam. It has a fine-cell structure with closed pores. The advantages of polyurethane foam are low thermal conductivity and low moisture absorption. Weak side- flammability.

The main types of pre-insulated pipes that are used for heating networks:

1. Steel pipes insulated with polyurethane foam . Thermally insulated pipes are produced in accordance with GOST 30732-2006 “Steel pipes and fittings with thermal insulation made of polyurethane foam with a protective shell.” Steel pipes in polyurethane foam are operated at a pressure of up to 1.6 MPa and a coolant temperature of up to 1400 degrees (it is possible to increase the temperature to no more than 1500 degrees). The diameter of steel pipes is up to 1420 mm. The protective shell of thermally insulated pipes is made of PE (for ductless installation), as well as galvanized steel (for above-ground installation). The quality of the products is determined not only by the quality of the steel pipes and its shell, but also by the technology for manufacturing polyurethane foam insulation.

The priority in the use of pre-insulated steel pipes is due to a large range of standard sizes, high heat resistance, and the possibility of using high blood pressure, the presence of highly qualified personnel in construction and maintenance companies. The main disadvantage of steel pipes is their low corrosion resistance. The use of indicator conductors in the operational remote control system (ORMS) is necessary when combating corrosion. They are located in the PPU. The use of ODS makes it possible to detect an area with excessive moisture in the insulation, which facilitates the prompt completion of work on the repair of thermally insulated pipes. The service life (according to GOST 30732-2006) of a pre-insulated steel pipeline (at least 30 years) is possible only with very high-quality installation of this pipeline, which complies with all standards for water treatment and with the obligatory presence of a water supply system. One of the main reasons for the early wear of steel pipes in polyurethane foam is the wetting of the heat insulator, due to poor tightness of the external insulation, due to poor quality work on insulating the joints. Another cause of wear is technological defects during welding work pipes in PE shells.

2. Polymer pipes "Isoproflex" - these are pipes made of cross-linked polyethylene (PEX) in PPU insulation. These thermally insulated pipes have good flexibility (bending radius approximately 1 m) and heat resistance up to 95°C. Maximum operating pressure is up to 1.0 MPa. The ability to use long sections allows for quick installation. The main positive features of Isoproflex pipes are flexibility and high chemical resistance. This makes it possible to exclude SODK. But there are also disadvantages - the large thickness of the pipe wall and, therefore, high cost. Plastic pipelines are cheaper to operate than steel ones. No need to carry out repair work caused by corrosion, like steel pipes. There are no costs for maintaining UEC systems.

Add to bookmarks

Pre-insulated heating mains: what are the advantages?

Pre-insulated pipes are a special type of product that is used for laying large heating mains and heating systems. Unique features of such products are given not only by the materials, but also by the presence of a technical control system, which is not used for other types of pipes.

Pipe diagram
1 – pressure corrugated stainless steel pipe; 2 – indicator conductors (when producing pipes with the UEC system); 3 – thermal insulation made of polyurethane foam;
4 – corrugated protective shell made of polyethylene.

When laying such routes, heat loss is reduced significantly; it amounts to up to 2%, which was previously considered impossible even when using insulation. Pre-insulated pipes are already completely finished goods, which do not require additional work during installation, which significantly reduces all installation and further maintenance costs.

Features of pre-insulated pipelines

A pre-insulated pipeline is special system, which was created for laying heating mains. Such pipes have numerous advantages and features, the main thing being that the pipe consists of several layers, each of which has its own characteristics.

Thus, part of the pipes, which is intended for underground installation, is made of steel and a polyurethane shell, between which a heat-insulating layer is laid, but for the pipes of the above-ground system, the outer shell is made of galvanization, which allows you to effectively protect the route from corrosion, adverse weather conditions, and other influences .

Production specifics

Pre-insulated steel products are intended for laying heating mains, while pipelines in a steel or polyethylene sheath are laid in a channel-free underground manner, and in galvanized ones - in passage channels or tunnels above the ground.

The pipes themselves are a “sandwich” structure consisting of the following layers: a pressure steel inner pipe, a special signal wire SODK (technical control), a thermal insulation layer (usually made of polyurethane foam), and a protective shell. The result is a special pipe consisting of two separate pipes with thermal insulation located between them.

It is the manufacturing features that ensure the resistance of pipes to corrosion, which is very important for the constituent elements of any heating main.

Before insulation begins, the pipe undergoes special treatment in a shot blasting machine. This gives the surface a slight roughness, which improves the adhesion of the thermal insulation layer to the base of the inner pipe.

The polyethylene shell is also treated with its own inside using coronary discharges, which guarantees excellent adhesion between the insulation and the pipe. All pipes pre-treated in this way acquire their own unique properties, allowing them to be used in the most unfavorable conditions.

Technical quality control

Today, insulated pipes are offered, which can have shells made of various materials. Most often these are shells made of polyethylene and galvanized steel, which can be suitable for laying underground and above-ground routes.

A casing made of similar materials provides protection from any mechanical damage, exposure to moisture, corrosion. In addition, diffusion of polyurethane, which is the main material for the production of the pipe itself, is prevented.

Soldering pipe connections.

Most often, high-density polyethylene is used to make the insulating shell, which is considered the most effective for underground installations. The polyethylene itself is thermo-light-stabilized, its color is black, it is produced strictly in accordance with GOST 16330, but in some cases GOST 18599 can be used.

Polyurethane foam is also used for insulation, which is excellent for steel pipes.

All pre-insulated pipes must undergo technical control, which allows us to guarantee the quality of the product. During laboratory tests, the following pipe characteristics are determined:

  • density;
  • compressive strength at 10 percent deformation;
  • volume fraction of all closed pores;
  • water absorption during boiling;
  • shear strength;
  • thermal conductivity.

Welded joints are 100% tested using modern method ultrasonic testing, which is mandatory requirement before implementation.

Benefits of use

Assembly diagram of parts of a pre-insulated flexible pipeline system.

All pre-insulated steel products differ from others for laying heating mains in the following advantages:

  1. The online remote monitoring system can significantly increase the strength and reliability of such pipes and reduce all costs for repairing installed heating mains.
  2. Service life is about 30 years, while simple uninsulated pipelines last only 10-15 years. This reduces the cost of replacing unsuitable pipes, route maintenance, and repairs.
  3. Such a pipe reduces heat loss during use by up to 2%, although when laying uninsulated pipelines such losses are quite significant - from 25%.
  4. Steel insulated routes are laid much easier and faster than usual, construction time is reduced by about two to three times, since there is no need to install channels and wells, and this causes a reduction in all costs.
  5. All steel pipes do not require additional anti-corrosion coating, as they already have all the necessary properties. This allows you to reduce the cost of the gasket many times.
  6. The heat resistance of pipes is up to 150 degrees.

The following conclusions can be drawn: all pre-insulated pipelines are much more profitable for the installation of heating mains, since they are more modern and less expensive. Their durability is twice as long, and operating costs and repair costs are reduced by the same amount. In a word, this is a profitable and promising option.

Basic provisions for the production of work

Materials of pre-insulated heating network pipeline

5.1 Pre-insulated pipes and parts are used for the construction of heating networks
according to manufacturers' catalogs.

5.2 The material of the steel pipe must comply with the requirements of the Construction Rules and
safe operation steam pipelines and hot water, approved
Ministry of emergency situations and the Ministry of Labor of the Republic of Belarus
(3.1.1 and 3.1.2).

5.3 Changing the direction of the heating network pipeline route is carried out using
factory-made pre-insulated bends with angles of 15, 30, 45, 60, 75, 90°.
Turns of the route at an angle of 15° or less are carried out by trimming individual
pipeline sections at an angle of no more than 5°.

5.4 Fittings - pre-insulated ball valves (valves).

5.5 Compensation for temperature expansion of pipelines is carried out due to
application of L, Z, U-systems, disposable expansion joints, preheating
pipeline during installation.

5.6 Connection of steel pipelines different diameters performed by welding with
using standard transitions.

5.7 Connecting the joints of external polyethylene pipes is carried out using
a special sheath placed on the pipeline, made of low-density polyethylene
pressure grades 273-79, 273-80, 273-81 according to GOST 16338 or high-density polyethylene

grades 102-14,102-90,102-10,153-9,153-10,154-4 according to GOST 16337.

5.8 Sealing of butt joints is carried out using heat-shrink tape
or heat shrink bandage.

5.9 For thermal insulation of butt joints, polyurethane foam PPU-317M is used (TU
-1472), consisting of component A 317M/1 according to TU 6.55.221.14.71 and component B
(polyisocyanate) according to TU 113.03.38-106.

It is allowed to use imported polyurethane foam components.

5.10 To perform thermal and hydraulic insulation at the ends of the pipeline
a special end nozzle, polyurethane foam components, and also
shrink tape or sleeve.

Transportation and storage of pre-insulated elements

5.11 When transporting, loading and unloading pre-insulated pipes and their elements
precautions must be taken to avoid damaging the outer
polyethylene sheath pipe.

5.12 Loading and unloading operations must be carried out using soft
wide slings and slings with end grips. Steel slings cannot be used as slings
cables, cords, etc., causing deformation of the surface of polyethylene pipes. Throw
pipes are prohibited.

5.13 Transportation of pipes by road and loading and unloading operations
allowed at outdoor temperatures down to minus 20 °C. Pipes should be stored in
stacks on a flat area equipped with beds located at intervals of 2 m.
The height of the stack should not exceed 1 m. The stacks should be located under a canopy,
protecting pipes from impact sun rays and atmospheric precipitation.

5.14 The duration of storage of pre-insulated products must be specified in their
manufacturer.

When storing products at negative temperatures Mechanical impacts (impacts) on the polyethylene shell, which can cause its destruction, should be avoided.

5.15 Liquid components of polyurethane foam should be stored in heated rooms
at temperatures from 15 to 30 °C.

Excavation and auxiliary works

5.16 Ground, auxiliary and preparatory work should be carried out according to
requirements of SNB 5.01.01 and SNiP 3.05.03.

5.17 The depth of the trench is determined by the design according to the longitudinal profile based on
permissible depths for laying pipelines, taking into account leveling sand bedding
thickness of at least 100 mm. The density of the filled soil after compaction should be
be in the range from 1700 to 1800 kg/m"

5.18 The minimum width of the trench base depends on the size of the corresponding
pipe diameters and regulated horizontal distances between pipes and wall
trenches. The distance from the pipe to the trench wall must be at least 100 mm. Distance
between pipes, mm, is taken for pipes with a diameter of:

From 90 to 225mm--150;

From 250 to 780 mm - 250;

More than 900 mm - 350.

5.19 In places where connections of pre-insulated elements are made, a trench is necessary
expand and deepen, based on the convenience of performing the work.

5.20 The bottom must be flat and sloped in accordance with the design.

5.21 The tolerance for bottom unevenness should not exceed 3 cm over a length of 1 m.

6 Installation of pre-insulated pipes and elementsGeneral requirements

6.1 Heating networks made from pre-insulated pipes are installed in compliance with the requirements
supervision by representatives of the design organization and the customer. Work must be carried out in favorable weather conditions. Welding of pipes should be performed at a temperature not lower than 0 °C, and insulation and sealing of joints should not be lower than 10 °C. In case of precipitation, sealing of connections must be done under cover (a tent made of film, tarpaulin, etc.).

Pipeline laying

6.2 The pre-insulated pipeline should be laid on a leveling layer of sand
at least 10 cm thick.

Lowering pre-insulated pipes with an outer diameter of up to 160 mm into the trench can be done manually or using a winch (crane). In this case, precautions must be taken so as not to damage the shell pipe.

6.3 Pre-insulated pipes containing alarm detection devices
faults in the pipeline insulation, must be laid so that the control
the wires were at the top of the pipe.

6.4 The pipeline should be laid with a slope of at least 2%0.

Pipeline installation

6.5 Welding of joints and bends of pre-insulated pipelines is carried out
directly in the trench. In some cases, it is possible to weld the pipeline above
trench, as specified by the project.

In this case, pre-insulated pipes must be laid on wooden pads with a cross-section of 100x100 mm, which are placed in increments of 2 to 3 m.

6.6 Before laying pre-insulated pipes and elements in a trench, it is necessary to
put temporary plugs on the pipes.

6.7 All connections of steel pipes and their elements should be made by electric welding.
Gas welding is allowed for pipes with a diameter of up to 50 mm.

6.8 Welding work when connecting pre-insulated pipes should be carried out in accordance with
requirements of current regulatory documents.

6.9 During gas welding It is necessary to use protective screens to protect the insulation and shell pipe from the burner flame.

6.10 Before starting welding, the ends of steel pipes must be thoroughly cleaned of
anti-corrosion oil using active degreasers, without solvents, as well as
from polyurethane foam, because when it burns, toxic gases are released.

6.11 After making welded joints and testing the pipelines for leaks
begin to install the alarm system.

6.12 If it is necessary to shorten a pre-insulated pipe, it is necessary to
the following operations:

Measure the specified segment and mark the location of the cut;

Measure 200 mm from the cut point on the remaining pipe and mark with a circular line;

Saw off the polyethylene pipe with a hacksaw along the intended section line so that
to avoid damaging the alarm wires;

Remove the cut section of the polyethylene sheath pipe;

Remove the polyurethane foam insulation in the area where the casing pipe is removed using
knife or other cutting tools, be careful not to damage the wires
alarms;

Thoroughly clean the surface of the steel pipe to prevent
burning polyurethane foam residues, which release toxic gases;

Cut the steel pipe.

Installation of butt joints

6.13 Wooden pads are laid on a sandy base, the distance between
which should be no more than 3.0 m. The alignment of the welded pipes is ensured.
Before starting the connection, a coupling is put on one end of the pipe. If
If heat-shrinkable rings are used, they must be put on as well.

After checking the alignment, the pipes are welded.

If pipes with signal wires are installed, it is necessary that the wires are at the top in the “10 minutes to 14 o’clock” position.

When installing the transition, two couplings of different diameters are required, which are first put on the ends of the pipes being welded. When installing a heat-shrinkable seal, the following measures must be taken:

If necessary, complete the installation of the alarm system;

Pull the signal wires through the heat-shrinkable seal, and if there is
necessity - to connect the signal wires to each other;

Clean the steel pipe with metal brush from rust;

Clean the outer polyethylene pipe from foreign objects and clean it;

Heat the steel and polyethylene pipes to 60 °C;

Install heat shrink seal on steel and polyethylene pipes.
After checking the coupling for leaks, components are poured into the coupling hole
polyurethane foam. After the foam has hardened, the hole is sealed with a plug.

Alarm system

6.14 To monitor the condition (humidification) of the heat-insulating layer of the pipeline
An alarm system is being installed.

The system consists of two copper wires (hereinafter referred to as wires) with a cross-sectional area of ​​1.5 mm2, mounted in polyurethane foam insulation at a distance of 15 to 20 mm from the steel pipe in the “10 minutes to 14 o’clock” position.

Installation of butt joints

Sealing the end of the pipeline

6.26 Before sealing the end of the pipeline, it is necessary to close the hole in the steel pipe.
After positive results of leak testing at the end of the pipeline
insert the end coupling so that between the bottom of the coupling and the end of the steel pipe
The thermal insulation thickness was 5 cm for pipes with a diameter of up to 200 mm and 7.5 cm for pipes
with a diameter of more than 250 mm.

Heat-shrinkable sleeves are used to hydraulically insulate the end of a pre-insulated pipeline.

Backfilling pipelines with soil

6.27 Backfilling begins with sand sprinkling.

Sand sprinkling should be done in two layers. The first layer is to fill the space between the pipelines, as well as between the pipeline and the trench wall, and then compact the layer. Lay the second layer horizontally, at least 10 cm above the pipeline and compact it.

After filling with sand, fill the remaining part of the trench with soil previously selected from the trench (removing large stones and hard blocks from it) and compact it mechanically.

Special requirements

6.28 In the case of laying pre-insulated pipelines in places exposed to
dynamic loads (exceeding 5.0 t/axle), as well as with a covering layer of less than
50 cm, in places provided for by the project, at a height of at least 30 cm above the surface
pipelines need to be laid reinforced concrete slab, or lay the pipeline in
protective pipes or reinforced concrete channels.

6.29 Heating network mark with warning tape laid at a distance of 30 cm
over the pipeline.

7 Testing and acceptance of pipelines into operation

7.1 Testing and flushing of heat pipes is carried out in accordance with the requirements
SNiP 3.05.03 and "Rules for the construction and safe operation of steam and
hot water", ed. 1994

Heat pipelines must be subject to preliminary and final tests for strength and tightness.

Preliminary testing of pipelines should be carried out in separate sections as installation and welding work is completed before installation of starting equipment, bellows compensators, shut-off valves, but after the welded section of the heat pipeline is laid and the ends of the tested section are welded with plugs. The use of shut-off valves to disconnect the test section is not permitted.

7.2 Reports are drawn up on the results of testing and washing.

7.3 Acceptance of pipelines for operation must be carried out in accordance with
requirements of SNB 1.03.04, taking into account the instructions of SNiP 3.05.03.

When storing pre-insulated pipes, fittings, parts and elements at the construction site, taking into account the flammability of polyurethane foam and polyethylene, you should follow the rules fire safety(GOST 12.1.004). It is prohibited to light a fire or carry out hot work in the immediate vicinity (no closer than 2m) to the storage area of ​​insulated pipes, or to store flammable and flammable liquids near them.

8.3 If the thermal insulation of pipes, fittings, parts and elements catches fire, you should
use conventional fire extinguishing agents; In case of fire in an enclosed space, you should
use BKF brand gas masks.

When drying or welding the ends of steel pipes free from thermal insulation, the ends of the thermal insulation should be protected with tin split screens with a thickness of 0.8 to 1 mm to prevent ignition from the flame of a propane torch or electric arc welding sparks.

8.4 When heat shrinking polyethylene couplings and cuffs with a propane torch flame
it is necessary to monitor the heating of couplings, cuffs and polyethylene pipe shells, do not
allowing polyethylene to burn or ignite.

8.5 Waste polyurethane foam and polyethylene when cutting insulated pipes and
the release of steel pipes from insulation should be immediately after the end of the working
operations are collected and stored in a specially designated area on the construction site at
a distance of at least 2 meters from thermally insulated pipes and parts.

8.6 Thermal insulation of pipes and parts (foamed polyurethane foam and polyethylene) is not
explosive if normal conditions does not release toxic substances into the environment
and does not have a harmful effect on the human body upon direct contact. Handling it does not require special precautions (hazard class 4 according to GOST 12.1.007).

8.7 All work on polyurethane foam insulation of pipe joints
(preparing a mixture of polyurethane foam, pouring the mixture into a joint) must be carried out using special protective equipment (cotton suit, special shoes,
rubber gloves, cotton mittens, safety glasses).

When filling joints of pipelines laid in passage channels (tunnels) with polyurethane foam, it is necessary to use a respirator of the RU-60M type.

8.8 At the site where joints are filled with polyurethane foam, there must be means for degassing the substances used (10% ammonia solution, 5% hydrochloric acid solution), as well as a first aid kit with medications (1.3% sodium chloride solution, 5% solution boric acid, 2% solution of baking soda, iodine solution, bandage, cotton wool, tourniquet). It must be remembered that component “B” of the polyurethane foam mixture (polyisocyanate) is a toxic substance.

9 Security environment

9.1 When laying heating networks, the requirements of SNiP 3.05.03 must be observed
environmental protection.

9.2 It is not allowed to produce without obtaining permission in accordance with the established procedure
heating network construction works.

9.3 Flushing of pipelines should be carried out by reusing water.
Drain water from pipelines after washing (disinfection) to places
provided for by the PPR.

9.4 The territory after completion of work on the installation of a heating network must be
cleared of construction and installation waste and restored in accordance with
project requirements.

9.5 Waste thermal insulation made from polyurethane foam and polyethylene should be collected for
their subsequent removal to the plant for disposal or burial in permitted places.

Contributing to the solution of the most pressing issues of energy saving and import substitution at the moment, SKTB Sarmat in October 1996 was the first in the Republic of Belarus to open the production of pre-insulated pipes.

The use of pre-insulated pipelines with an insulation monitoring system makes it possible to stop the process of damage to pipelines from external corrosion. Moreover, the undoubted advantages of pre-insulated pipelines are that they provide lower heat losses due to polyurethane foam insulation, compared to conventional channel laying, heat losses are reduced by approximately 3-3.8 times.

The laying of pre-insulated pipelines, in addition, has significant advantages over the traditional one; it does not require the use of reinforced concrete products and structures, has a significantly smaller depth of pipelines and reduces construction time by 3-4 times.

Ready-made pre-insulated pipelines and fittings are manufactured by SKTB Sarmat in accordance with TU RB.130-97.

Pre-insulated pipes and parts are made of steel pipes with a heat-insulating coating of industrial polyurethane foam (Freon-free and ozone-indestructible) with a waterproof coating of polyethylene or galvanized sheet.

The insulation is made of rigid polyurethane foam. Thermal conductivity coefficient is no more than 0.033 W/mK.

The total density is 80 kg/m3.

Compression resistance is not less than 0.3 MPa.

Shear resistance - (0.15-0.4) MPa.

The shell pipe is made of polyethylene. Thermal conductivity coefficient is no more than 0.43 W/mK.

Density - 950kg/m.

Service life is 50 years.

Polyethylene pipes made without seams are resistant to impact, corrosion, and ultraviolet rays. For air laying there is a shell made of galvanized sheet in the form of a spiral-coiled pipe TU RB 6-9.