The thickness of the insulation of thermal networks. Pipeline insulation

To reduce the level of heat loss in heating systems that occur in cold period pipes are insulated. Heat-insulating materials contribute to saving the required temperature in the network, eliminating the occurrence of condensate on the pipeline surface and insulation. The use of these types of products prevents icing of water during stagnation, and slows down the corrosion process that forms over time on pipeline components that are made of metal, prolonging their service life.

When choosing a heater, it is necessary to initially determine the place where it will be used, outside or inside the house. The choice of thermal insulation material is influenced by:

• pipe diameter;
• heating temperature of the heat carrier;
• conditions under which the heating system is operated.

The types of insulation used differ depending on the diameter of the pipes available. Manufacturing companies offer semi-cylinders, soft roll insulation and cylinders with certain form hard execution.

For pipelines with small diameters, half-cylinders and cylinders with characteristic rigidity are suitable. This type of execution has grooves that greatly simplify installation work. This material has an excellent level of resistance against high temperatures with minimal water absorption. Rigid heat insulator constantly retains its primary shape, providing additional safety from possible mechanical damage.

When choosing, you need to pay attention to the following characteristics of a heat insulator:

• flammability class, especially should be taken into account for further placement inside residential and industrial buildings;
• the level of water absorption, on which the service life of the material directly depends, because at a high level of moisture absorption, the insulation succumbs to decay, starting to decompose, subsequently not representing any efficiency;
• the degree of resistance to ultraviolet radiation, because a material with a low index, which is located outside the house, will begin to succumb to destruction by sunlight;
• the level of thermal conductivity should be as low as possible, because at a low rate, the heat insulator saves heat better, allowing the use of insulation with thinner layer.

Varieties of insulation materials

Thermal insulation of heating pipes is carried out after the acquisition of the material, but until this moment it is necessary to learn about the characteristics and advantages of the insulation, as well as its scope. After these data, it will be possible to choose the most suitable and effective option.

This insulation consists of ribs and walls, which form a solid structure of a solid form. It creates a heat-insulating shell that has high level strength, while effectively retaining heat inside the heating network. Polyurethane foam has the following positive qualities:

• odorless and non-toxic;
• does not rot;
• it is environmentally friendly to the human body;
• has excellent dielectric qualities;
• material is resistant to different kind climatic influences, favorably suited for outdoor use;
• a sufficiently strong insulation that excludes the possibility of pipeline breakdowns under the influence of mechanical loads from the outside.

Its only tangible drawback is its high cost.

mineral wool

Possessing a significant level of efficiency, it is quite in demand among heat insulators. It consists of mineral wool, and has a number of its features:

• cotton wool has low moisture absorption due to the processing with special compounds during the manufacturing process;
• a high degree of thermal stability, which, when heated, ensures the preservation of thermal insulation and mechanical parameters at the primary level;
• is environmentally friendly, does not contain toxic substances;
• it is not afraid of exposure to acids, solvents and other chemical solutions.

Mineral wool is excellent for use as a heat insulator for pipes. heating networks. It is quite often installed on pipelines that are subjected to continuous heating of great force.

Foamed polyethylene

Does no harm human body. It is not afraid of significant temperature changes and is resistant to moisture. The heater is quite popular among buyers. It has the shape of a tube with a specific thickness, in which an incision is made. It is used as a heat-insulating material for pipes of the heating network, as well as for warming warm and cold water pipes.

It preserves its properties when used in conjunction with other building materials, including concrete, lime and others.

This heater for heating pipes appeared on the market quite recently, being a reflective heat insulator, which consists of aluminum foil and cellular polyethylene. Thanks to the 2 layers, the material has excellent thermal performance, which is why it is quite in demand among buyers. Folgoizol has a number of features:

• relatively easy installation, no special means protection;
• it is environmentally friendly, does not emit toxic substances;
• has a long service life;
• has a wide range of uses, suitable for both indoor and outdoor use.

Penofol is distributed in rolls with a different level of density of the polyethylene layer. When choosing a thickness, one should start from the future conditions for the use of a heat insulator. The double layer contributes to the retention of heat in an enclosed space, achieving the maximum allowable efficiency.

Stages of thermal insulation of heating pipes

mineral wool

Processes for warming the heating pipeline with mineral wool must be carried out with gloves on.

1. First of all, the material is cut in accordance with the desired dimensions.
2. It is wound on the pipe, and it does not need to be tightened strongly.
3. At intervals, one should stop, making fixation with electrical tape, wire or a solid rope.
4. Having finished covering the pipeline with mineral wool, it is necessary to prepare a protective sheathing, which is made of roofing material or corrugated foil, which is pre-cut into pieces.
5. Having installed a shell of foil or roofing felt, it is fixed with plastic ties or ropes.

polyurethane foam shell

With a small diameter, a cylindrical or semi-cylindrical shell shape can be used.

1. Thermal insulation material is put on the pipeline.
2. It is fixed by means of glue, adhesive tape, wire or self-adhesive tape.

If the pipes have a large diameter, then it is necessary to select a shell, which consists of several parts. This kind of material is fixed according to the groove-thorn principle.

Having produced high-quality insulation heating networks, it will be possible to save a significant amount of heat indoors. Therefore, the choice of insulation should be approached responsibly, weighing all the advantages of heat-insulating building materials available on the market before making a purchase.

Thermal insulation is of great importance in the construction of a heat pipe. Not only heat loss but, just as importantly, its durability. With the appropriate quality of materials and manufacturing technology, thermal insulation can simultaneously play the role of anti-corrosion protection of the outer surface of the steel pipeline. Such materials, in particular, include polyurethane and derivatives based on it - polymer concrete and bion.

Thermal insulation is arranged on pipelines, fittings, flange connections, compensators and supports for the following purposes:

reduction of heat losses during its transportation, which reduces the installed capacity of the heat source and fuel consumption;

reducing the temperature drop of the heat carrier supplied to consumers, which reduces the required heat carrier flow and improves the quality of heat supply;

lowering the temperature on the surface of the heat pipe and the air in the places of service (chambers, channels), which eliminates the risk of burns and facilitates the maintenance of heat pipes.

The main requirements for thermal insulation structures are as follows:

1) low thermal conductivity both in the dry state and in the state natural humidity;

2) low water absorption and small height of capillary rise of liquid moisture;

3) low corrosivity;

4) high electrical resistance;

5) alkaline reaction of the medium (pH > 8.5);

6) sufficient mechanical strength!

It is not allowed to use materials subject to combustion and decay, as well as containing substances capable of releasing acids, strong alkalis, harmful gases and sulfur.

Most difficult conditions for the operation of heat pipelines occur during underground channel and especially channelless laying due to moistening of thermal insulation with soil and surface waters and the presence of stray currents in the ground. In this regard, the most important requirements for heat-insulating materials include low water absorption, high electrical resistance, and with channelless laying, high mechanical strength.

As thermal insulation in heating networks, currently used mainly products made from inorganic materials (mineral and glass wool), lime-silica, sovelite, volcanic, as well as compositions made from asbestos, concrete, asphalt, bitumen, cement, sand or other components for channelless laying: bitumen perlite, asphaltoizol, armo foam concrete, asphalt expanded clay concrete, etc.

Depending on the type of products used, thermal insulation is divided into wrapping (mats, strips, cords, bundles), piece (slabs, blocks, bricks, cylinders, half-cylinders, segments, shells), pouring (monolithic and cast), mastic and backfill.

Wrapping and piece products are used for all elements of heating networks and can be either removable - For equipment requiring maintenance (gland expansion joints, flange connections), or fixed. They are fastened with bandages, wire, screws, etc., made of galvanized, cadmium or corrosion-resistant materials, and a cover layer. Filling and filling insulation is usually used for elements of heating networks that do not require maintenance. Mastic insulation may be used for shut-off and drainage valves and stuffing box expansion joints, provided that removable structures are made for branch pipes of stuffing box expansion joints and stuffing boxes for sealing fittings.

The heat-insulating structures of steel pipelines for above-ground and underground channel laying, as well as for channel-free laying in a monolithic shell, usually consist of three main layers: anti-corrosion, heat-insulating and cover. The anti-corrosion layer is superimposed on the outer; the surface of a steel pipe and is made of coating and wrapping materials in several layers (isol or brizol on insulating mastic, epoxy or organosilicate enamels and paints, glass enamel, etc.). On top of it, the main heat-insulating layer of wrapping, piece or monolithic products is laid. It is followed by a cover layer that protects the heat-insulating layer from moisture and air and from mechanical damage. It is performed at underground laying from two or three layers of isol or brizol on insulating mastic, asbestos-cement plaster on a metal mesh, lacquered fiberglass with various impregnations, foil isol, and for above-ground laying - from sheets of galvanized steel, aluminum, aluminum alloys, glass cement, glass roofing material, fiberglass, etc.

Channel heat pipes. In channels with an air gap, the insulating layer can be made in the form of a suspended or monolithic structure. On fig. 8.25. an example of a suspended insulating structure is shown. It consists of three main elements:

a) anti-corrosion protective layer 2 in the form of several layers of enamel or isol applied at the factory on a steel pipeline 1, having sufficient mechanical strength and having high electrical resistance and the necessary temperature resistance;

b) thermal insulation layer 3, made of a material with a low thermal conductivity, such as mineral wool or foam glass, in the form of soft mats or hard blocks laid on top of a protective anti-corrosion layer;

in) protective mechanical coating 4 in the form of a metal mesh acting as a supporting structure for the heat-insulating layer.

To increase the durability of the heat pipe Basic structure suspension insulation (knitting wire or metal mesh) is covered on top with a sheath of non-corrosive materials or asbestos-cement plaster.

Rice. 8.25. Heat conductor in an impassable channel with an air gap

1 - pipeline; 2 - anti-corrosion coating; 3 - heat-insulating layer; 4 - protective mechanical coating

Channelless heat pipes. They find justified application in the case when, in terms of reliability and durability, they are not inferior to heat pipelines in impassable channels and even surpass them, being more economical compared to the latter in terms of initial cost and labor costs for construction and operation.

The requirements for the insulating structures of channelless heat pipelines are the same as for the insulating structure of heat pipelines in channels, namely, high and stable heat, moisture, air and electrical resistance under operating conditions.

Channelless heat pipelines in monolithic shells. The use of channelless heat pipelines in monolithic shells is one of the main ways to industrialize the construction of heat networks. In these heat pipelines, a shell is applied to the steel pipeline at the factory, combining heat and waterproofing structures. Links of such elements of the heat pipeline up to 12 m long are delivered from the factory to the construction site, where they are laid in a prepared trench, butt welding of individual links between themselves and the application of insulating layers to the butt joint. In principle, heat pipes with monolithic insulation can be used not only without channels, but also in channels.

Modern requirements for reliability and durability are quite fully met by heat pipes with monolithic thermal insulation made of cellular polymeric material such as polyurethane foam with closed pores and an integral structure made by molding on a steel pipe in a polyethylene sheath (“pipe in pipe” type).

At the same time, pre-insulated pipelines are made with a polyethylene sheath. high pressure. The space between the shell and the pipe is filled with rigid polyurethane foam. Embedded in polyurethane foam copper conductors to control the presence of moisture in the thermal insulation of the pipeline.

Due to the good adhesion of the peripheral layers of insulation to the contact surface, i.e. to the outer surface of the steel pipe and inner surface polyethylene sheath, the long-term strength of the insulating structure is significantly increased, since during thermal deformation the steel pipeline moves in the ground together with the insulating structure and there are no end gaps between the pipe and the insulation, through which moisture can penetrate to the surface of the steel pipe.

Average thermal conductivity polyurethane foam insulation is, depending on the density of the material, 0.03 - 0.05 W / (m ∙ K), which is approximately three times lower than the thermal conductivity of most widely used thermal insulation materials for heating networks (mineral wool, reinforced concrete, bitumen perlite, etc.).

Thanks to high warmth- and the electrical resistance and low air permeability and moisture absorption of the outer polyethylene sheath, which creates additional waterproofing protection, the thermal waterproofing structure protects the heat pipeline not only from heat losses, but, no less important, from external corrosion. Therefore, when using this insulation design, there is no need for special anti-corrosion protection of the surface of the steel pipeline.

Use of pipelines with polyurethane foam insulation allows to reduce losses of thermal energy by 3-5 times in comparison with existing species thermal insulation (bitumperlite, expanded clay bitumen, foam concrete, etc.) and obtain annual savings of about 700.0 Gcal/year per 1 km.

The construction of heat networks with polyurethane foam insulation is carried out several times faster compared to channel ones and the cost is 1.3-2 times lower, and the service life is 30 years, while the durability of commonly used structures is 5-12 years.

Bitumoperlite, bitumen expanded clay and other similar insulating materials based on bituminous binder have significant technological advantages that make it possible to industrialize the production of monolithic shells on pipelines relatively easily. But along with this, the specified technology for manufacturing shells needs to be improved to ensure uniform density and homogeneity of the bitumen-perlite mass both along the perimeter of the pipe and along its length.

In addition, bitumen-perlite insulation, like many other materials based on a bituminous binder, loses water resistance during prolonged heating at a temperature of 150 ° C due to the loss of light fractions, which leads to a decrease in the corrosion resistance of these heat pipes. To increase the anticorrosion resistance of bitumen-perlite, polymer additives are introduced into Portland cement during the production of hot molding mass, which increases the temperature resistance, moisture resistance, strength and durability of the structure.

Channelless heat pipes in bulk powders. These heat pipelines are mainly used for pipelines of small diameter - up to 300 mm.

The advantage of channelless heat pipes in bulk powders compared to heat pipes with monolithic shells lies in the ease of manufacturing the insulating layer. The construction of such heat pipelines does not require the presence of a plant in the construction area of ​​heat networks, which must first receive steel pipes for applying a monolithic insulating shell. Insulating bulk powder in appropriate packaging, e.g. in polyethylene bags, can be easily transported to long distances rail or road transport.

Self-sintering foam concrete, perlite concrete, asphalt or asphalt concrete are used as such powders.

As is known, in two-pipe heating networks temperature conditions, and consequently, the temperature deformations of the supply and return pipelines are not the same. Under these conditions, adhesion of the thermal insulation layer to the outer surface of steel pipelines is unacceptable. To protect the outer surface of steel pipelines from adhesion with the insulating mass, they are covered on the outside with a layer of anti-corrosion mastic material, such as asphalt mastic, before pouring with a liquid foam-cement mortar.

Cast structures for thermal insulation of channelless pipelines. Of the cast structures of channelless heat pipelines, heat pipelines in a foam concrete mass have received some use; perlite concrete can be used as a material for the construction of such heat pipelines. Steel pipelines installed in trenches are filled with a liquid composition prepared directly on the route or delivered in a container from the production base. After setting, the concrete or perlite concrete array is covered with soil.

test questions

1. What are the main requirements for the design of modern heat pipelines? Name the assortment of pipelines of the heating network and the types of fittings used.

2. Compare underground heat pipelines in through channels, impassable and channelless. Name the advantages and disadvantages of each type of gasket and the main areas of their appropriate application.

3. Name the designs of modern expansion joints temperature deformations pipelines of thermal networks. How is the calculation and selection of U - shaped expansion joints?

4. Describe the construction of supports for pipelines of heating networks. Give the calculation formula for determining the resulting force acting on the fixed support of the heat pipe.

5. What are the main features and requirements for heat-insulating structures of heat pipelines?

Thermal insulation of equipment and prospects for the development of the industry

The rational use and use of fuel and energy resources is one of the highest priority tasks in the development of any economy.

Insulation for piping and equipment causes technical capabilities and economic efficiency in the implementation of technological processes.

The main role in solving this problem belongs to effective thermal industrial insulation. Insulation for the pipeline is widely used in energy and housing and communal services. It is also used in the metallurgical, oil refining, food and chemical industries.

In the energy sector, thermal insulation for pipelines is used in steam boilers, gas and steam turbines, heat exchangers, as well as in tanks accumulating hot water and in chimneys. In industry, technological apparatuses (vertical and horizontal), pumps and heat exchangers are insulated. Tanks for storage of oil products, oil and water are subject to thermal insulation. Increased requirements are imposed on the thermal insulation of cryogenic equipment and other low-temperature units. Insulation for pipelines will ensure the implementation of various processes, including technological ones, and allow creating working conditions that exclude the risk of injury and damage. It will reduce losses from evaporation of oil products from tanks and will allow storing natural and liquefied gases in isothermal storage.

Technological requirements for insulating structures

During installation and subsequent operation, insulation for pipelines is subjected to water and temperature, vibration and mechanical stress. These impacts determine the list of requirements that apply to these structures. Thermal insulation materials and structures must have:

• thermal efficiency;
• operational durability and reliability;
• fire and environmental safety.

There are several main indicators that determine the operational and technical-physical properties of such materials. These include: compressibility, elasticity, resistance to aggressive media, strength at 10% deformation, thermal conductivity and density. Of no small importance is the biological stability and the content of organic substances. The efficiency of thermal insulators is primarily determined by the coefficient of thermal conductivity. This coefficient determines the required thickness of the insulating layer, and, as a result, the installation and design features of the design, the load on the object that needs to be isolated. When performing calculations, we use design factor thermal conductivity. It takes into account temperature, the presence of fasteners and sealing heat-insulating materials in this design. When theoretically choosing a heat-insulating material, take into account:

• its linear shrinkage during operation, the dimensions of the material may decrease when heated;
• loss of mass and strength, when heated, destruction of the material may occur;
• the degree of partial burnout of the binder with increasing temperature;
• maximum allowable loads on insulated surfaces and supports, determined limit weight insulating material.

The service life of heat-insulating materials and structures largely depends on the conditions in which they work and design features. Operating conditions include:

• the place where the object is located;
• mode of operation of the equipment;
• aggressiveness of the environment;
• mechanical influences and their intensity.

The presence and quality of the protective coating of heat-insulating materials and heat-insulating structures largely determine their service life.

Thermal insulation of today's pipelines

To date, the market of heat-insulating materials is filled with products of both foreign manufacturers and domestic brands. The range of fibrous insulation for equipment on the market includes a list of such materials for pipeline insulation:

• mats mineral pierced heat-insulating;
• mineral mats lined with kraft paper, fiberglass or metal mesh;
• for industrial insulation, mineral products with a corrugated structure, according to TU 36,16,22-8-91;
• heat-insulating mineral plates with a density of 75-130 kg/cu.m. on a synthetic binding material, in accordance with GOST 9573-96;
• products based on a synthetic binder made of staple and glass fibers, insulation for pipelines.

In a small volume, heat-insulating materials are produced in the form of products made of basalt and thin glass fibers, corresponding to TU 21-5328981-05-92.

Materials (insulation for pipelines) are widely represented by products of foreign manufacturers. Foreign insulation options for pipelines and equipment are represented by fibrous heat-insulating materials. These are cylinders, plates and mats, which are covered on one side with aluminum foil or metal mesh. Producing countries of this product: Denmark, Finland and Slovakia.

Foamed polyurethane, produced in the form of tile products, is increasingly used in similar structures. It should be noted that the above thermal insulation materials do not replace thermal insulation, they can only be used as additional elements to increase heat reflective characteristics. When channel laying pipelines in heating networks, cylinders made of glass fiber and mineral wool, soft plates and thermal insulation mats. For laying pipelines underground, pipes with waterproofing coating pre-insulated at the factory. It is possible to increase the temperature stability of heat-insulating structures with the help of polyurethane, if two-layer insulation is applied. The inner layer of such insulation should be made of mineral wool, and the outer layer should be made of polyurethane foam. These materials for pipeline insulation in this case can only be used in combination.

Thermal insulation for pipelines industrial scale It is very diverse both in the type of structures and in the materials used in these structures.

For insulating horizontal and vertical heat exchangers use structures using wire frames and heat-insulating fibrous materials. Wire frames are mainly used in the insulation of horizontal devices.

Regulations

Active today economic conditions influenced the revision of today's regulatory and technical framework for thermal insulation in industry. Thermal insulation of equipment is a priority industry.

Building codes and regulations 41-03 of 2003 were developed taking into account the current nomenclature and cost of protective and heat-insulating materials. The document contains requirements for products and materials, for thermal insulation structures, and design recommendations. It indicates the norms for the density of heat fluxes from the surfaces of the units under the conditions of their location in rooms or in the open air, under the conditions of laying pipelines underground. The current SP 41-103-2000 contains various methods calculations of thermal insulation, characteristics for calculations and nomenclature of auxiliary, cover and heat-insulating materials. This set of rules was revised in 2005-2006. According to the changes, many current rules from the category of "obligatory" they pass to the number of "recommendations". At the same time, the need to establish mandatory standards in such important issues as the durability and reliability of buildings, structures, housing and communal services and their energy saving will remain.

Thermal insulation materials can not only directly, but also indirectly ensure the safety and reliability of pipelines and equipment. They create conditions for life, energy saving in the construction sector and industry. Thermal insulation of equipment and insulation for pipelines ensures trouble-free operation of facilities classified as fire hazardous, explosive and hazardous to human health and environmental pollution.

Building Code 41-03 of 2003 includes many requirements that are not "recommended". These requirements relate, in particular, to the level of surface temperature of insulated pipelines and surfaces, the effectiveness of vapor insulation of cryogenic equipment and other low-temperature units. They define methods for calculating the temperature maximum and the degrees of flammability of heat-insulating materials. Thermal insulation for pipelines can provide the possibility of operation of this or that equipment in housing and communal services, industry and energy. In any area where it is used, thermal insulation, in addition to technological requirements, also provides energy saving requirements. Thermal insulation materials and insulation for pipelines in general are very important for the entire national economy.

The section SNiP 41-02-2003 entitled "Thermal insulation" lists the basic requirements for the construction and materials of thermal insulation of heat networks and pipelines of channel and channelless, underground and ground laying. For heating networks and pipelines, the norms for the density of heat flows are determined and are given in the section "Thermal insulation of pipelines and equipment" building codes and rules 41-03-2003.

In the future, it is planned to introduce and develop the “Code of Rules for Thermal Insulation for Pipelines and Equipment” and the definition of territorial norms for the design of thermal insulation.

Materials for pipeline insulation

Verification of physical and technical properties and testing of heat-insulating materials for pipelines are carried out in accordance with the methods of GOST 17177-94. According to GOST 7076-99 and GOST 30256-94, the coefficient of thermal conductivity for thermal insulation materials is determined. GOT7076-99 is called “Materials and building products. A method for determining thermal resistance and thermal conductivity in a thermal stationary regime. To date, approved established order methods for identifying important thermal insulation characteristics materials are missing.

Method for determining minimum temperature the use of thermal insulation materials requires additions and adjustments. This indicator is very important for foamed polymers, which are used to insulate pipelines and equipment located in low-temperature structures or in the open air. At low temperatures and mechanical action, they are destroyed. Insulation for pipelines at low temperatures is unstable.

Method for determining maximum temperature use of thermal insulation materials. This temperature is commonly understood as the temperature at which inelastic deformations under fixed loads appear in the material. In practice domestic manufacturers heating is carried out in a furnace on the entire surface of the sample. In foreign practice, heating of samples is used on one side.

Method for determining the thermal resistance of insulating cylinders made of glass and mineral fibers and the coefficient of thermal conductivity. Abroad thermal resistance thermal insulation for pipelines is determined according to ISO 8497:1994.

The development of thermal insulation

There are several main directions for the development of the industry of thermal insulation for pipelines and equipment.

Introduction to the design and construction of the latest design solutions and materials that will reduce heat losses in construction and industry. Expansion of the use of modern efficient insulating products made of glass and mineral fibers of domestic manufacturers. Enough high price thermal and insulating cylinders made of fiberglass or mineral wool, compensated by increased durability, reliability and thermal technical efficiency. Direction improvement. Insulation materials for pipelines, technology for insulating pipelines and mechanisms are 2 promising branches of the industry for the next 20-25 years.

Further improvement of the regulatory framework for industrial and building insulation. Bringing the regulatory framework in line with international standards. Promotion of domestic insulation products to the markets foreign countries. Carrying out test activities according to methods identical to international ones. These activities will contribute to the efficient use of insulation for pipelines abroad.

One of the most important tasks of the modern energy sector of the Russian Federation is energy saving. Of great importance in this is the reduction of heat losses through heating networks, heating mains and pipes of housing and communal services. The scale of losses is enormous: more than 70% of heat is lost every year. Of these, about 60% in heating plants, and 40% in residential buildings. The thermal insulation of most pipes is made in the old fashioned way, using glass wool or other piercing materials, protected from the outside by insulating, polymeric tapes, brizol or reinforced foam concrete. Heating mains with this type of insulation do not provide reliable and economical heat supply to consumers due to the greater frequency of pipe damage due to moisture and destruction.

And although in Europe, America, Canada, for more than 50 years, thermal insulation has been used with reliable and durable material- foamed polyurethane foam, this technology came to Russia only in 1994. The number of companies involved in polyurethane foam insulation is still small, despite the fact that a long period of time has passed.

CMETHODS OF THERMAL INSULATION OF PIPES USING POLYURETHANE FOAM There are three main methods of pipeline insulation:

PU foam shells

Pipe-in-pipe method

Polyurethane foam spraying

Also called semi-cylinders. They are made in the factory, by pouring polyurethane foam into molds. The resulting semi-cylinders and blanks for bends are fastened to each other at the pipeline installation site. different ways(screeds, clamps, polypropylene tapes, wire).

Semi-cylinders can be both without additional insulation, so with her. In this way, oil pipelines, gas pipelines, network engineering chemical plant, etc.

High-quality heat-insulating material reduces heat losses by two and a half times. Hidden in a durable moisture-resistant package, protected from corrosion and mechanical stress, the pipes last much longer.Labor intensity installation work on the installation of the shell is very low. Almost every enterprise can install thermal insulation.

Although the process of installing the shell is not very laborious, some technological rules should be observed:

First, the installation of thermal insulation must be carried out assembly locks perpendicular to the pipe. If you do not follow this rule, then a kind of tray is formed at the bottom of the pipe, in which there is condensate, which, one way or another, is formed. Longitudinal locks must be in vertical position.

Secondly, for joining the ends of the insulation, it is necessary to use composite glue and clamps. Clamps must be inserted into the shells in 3 places: at the beginning, in the middle and at the end. If the technological regimes of the installation are observed, the thermal insulation will last for more than a dozen years.

Pipe-in-pipe technology. This is the name of pipes pre-insulated with polyurethane foam. Used to insulate pipes made of stainless and galvanized steel, polypropylene and polyethylene. The essence of the method is as follows: another, larger in diameter, is put on the pipe through which the substance will be transported. Polyurethane foam is poured into the cavity between the pipes, which, foaming and hardening, forms a heat-insulating layer.

There are important requirements in the application of pipe-in-pipe technology:

First of all insulated pipe must be of perfect quality (after all, in case of damage, it will have to be changed along with the insulation).

Secondly, the pipe must pass full training for pre-isolation. In addition, "the pipe in the pipe must be equipped electronic devices control (every 200 meters of length), otherwise it is impossible to establish "sick" places of the heat pipeline.

The third method of thermal insulation is the spraying of polyurethane foam using special equipment. has the lowest coefficient of thermal conductivity of all currently used thermal insulation materials. For comparison: it is 25 times more effective silicate brick, 4.5 times - expanded clay gravel, 2 times - slabs of mineral wool and glass staple fiber and 1.5-1.7 times more effective than expanded polystyrene. A 45 mm polyurethane foam coating layer is sufficient for air laying, even if the coolant temperature is up to +1100 C, and outdoor temperature up to -250 C.

Installation work

Composition of operations and controls

Technical requirements

SNiP 3.04.01-87 paragraphs. 2.32, 2.34, 2.35, tab. 7

Permissible deviations:

When installing thermal insulation from rigid products laid dry, it is necessary to ensure:

The gap between the products and the insulated surface is not more than 2 mm;

The width of the seams between products is not more than 2 mm;

Fastening of products - according to the project.

When installing thermal insulation using soft and semi-rigid fibrous products, it is necessary to ensure:

Compaction factor:

for semi-rigid products - no more than 1.2; for soft - no more than 1.5;

Tight fit of products to the insulated surface and to each other;

Overlapping of longitudinal and transverse seams during insulation in several layers;

Installation on horizontal pipelines of fasteners from sagging thermal insulation.

When installing thermal insulation cover shells, it is necessary to ensure:

Tight fit of the shells to the thermal insulation;

Reliable fastening with fasteners;

Careful sealing of joints of flexible shells.

When installing an anti-corrosion coating metal pipes it is necessary to check the continuity, adhesion to the protected surface, thickness.

Not allowed:

Mechanical damage;

Sagging layers;

Loose adherence to the base.

Requirements for the quality of the materials used

GOST 10296-79*. Isol. Specifications.

GOST 23307-78*. Heat-insulating mats made of mineral wool are vertically layered. Specifications.

GOST 16381-77*. Thermal insulation building materials and products. Classification and general technical requirements.

GOST 23208-83. Heat-insulating cylinders and half-cylinders made of mineral wool on a synthetic binder.

Izol must be flexible. When bending a strip of isol grade I-BD at a temperature of minus 15 "C, grade I-PD at a temperature of minus 20" C on a rod with a diameter of 10 mm, cracks should not appear on the strip of isol. The insulation must be temperature resistant. When heated in a vertical position for 2 hours at a temperature of 150 ° C, no increase in length and the appearance of blisters should be observed. The isol web must be wound on a rigid core with a diameter of at least 60 mm, made of a material that ensures the safety of the isol during its transportation and storage. The length of the core must be equal to the width of the web or less than it by no more than 10 mm. The ends of the isol roll, as well as the edges of the sheets at the junction of the roll, must be evenly cut. The isol web should not have holes, tears, folds, edge tears, as well as non-recycled rubber particles and foreign inclusions. The lower surface of the canvas isol (inner in roll) should be covered with a continuous layer of powdered dressing. The isol cloth should not be stuck together.

Thermal insulation materials and products must meet the following general technical requirements:

Have a thermal conductivity of not more than 0.175 W / (m K) at 25 ° C;

Have a density (bulk weight) of not more than 600 kg/m 3 ;

Possess stable physical and mechanical properties;

Do not emit toxic substances and dust in quantities exceeding the maximum permissible concentrations.

For thermal insulation of equipment and pipelines with an insulated surface temperature above 100 °C, inorganic materials should be used.

Foam diatomite and diatomite heat-insulating products must have the correct geometric shape. Permissible deviations from the perpendicularity of faces and edges should not exceed 3 mm. Defects in appearance are not allowed in products:

Voids and inclusions with a width and depth of more than 10 mm;

Bruising and blunting of corners and ribs with a depth of more than 12 mm and
longer than 25 mm;

Through cracks over 30 mm long; products with cracks
30 mm is considered a ladling.

Work instructions

SNiP 3.04.01-87 paragraphs. 1.3, 2.1, 2.8-2.9, 2.32, 2.33,

SNiP 3.05.03-85 paragraphs. 6.1, 6.2

Thermal insulation work can only begin after the execution of an act (permit) signed by the customer and representatives of the installation organization and the organization performing thermal insulation work.

Insulation work may be performed at positive temperatures (up to 60 °C) and negative temperatures (up to -30 °C).

The surfaces of pipelines before insulation must be cleaned of rust, and those to be corrosion protection processed in accordance with the requirements of the project. Thermal insulation work on pipelines should only begin after they have been permanently fixed. Insulation of pipelines located in impassable channels and trays must be carried out before they are laid.

At a coolant temperature of up to 140 ° C, to protect the outer surface of pipes of heating networks from corrosion, a coating of isol in two layers on isol mastic is used. The total thickness of the coating is 5-6 mm. For an air heating system with a coolant temperature of up to 140 ° C, to protect the surface of pipes from corrosion, coatings combined with BT-177 paint over GF-020 primer are used. The total thickness of the coating is 0.15-0.20 mm.

To check the quality of work on the anti-corrosion protection sticker, an incision is made to the metal in a section measuring 200 x 200 x 200. The quality is considered satisfactory if the insulation is separated from the pipe with some effort. 5% of pipes are subjected to such a pull-off test.

Fastening of thermal insulation on pipelines should be done with bandages. To protect the main layer of thermal insulation from moisture, mechanical damage, it is necessary to use cover shells made of rigid or flexible (non-metallic) materials.

Installation of heat-insulating products must be started from flange connections and fittings and carried out in the direction opposite to the slope.

During an intermediate check, the surfaces prepared for thermal insulation are examined, with multilayer thermal insulation, each layer is checked before applying the next one. During the final check of the thermal insulation, the uniformity of the insulation thickness is determined along the entire length of the direct and return pipelines.

The thickness of the insulation is checked with a feeler gauge. Particular attention should be paid to the dosage of cement and asbestos when protecting the insulation with asbestos-cement mortar. An excess of cement in the asbestos-cement mass leads, after its hardening and heating, to cracking.