Thermal insulation of pipes
It's no secret that most residential buildings We have centralized heating, as well as water supply. But for this it is not enough to heat the water to the required temperature; it still needs to be delivered from minimal losses heat.
Previously, glass wool was used for these purposes. The pipe was wrapped in a layer of thermal insulation. The layer was fixed using steel wire. Then the pipe was covered from above with a sheet of galvanized steel. Over time, instead of galvanizing, they used ordinary cement mortar. But this approach was accompanied by large heat losses.
And only recently found wide application pipes in polyurethane foam (PPU). And then pipe shells were invented as thermal insulation.
Advantages
Pipes for overhead installation in galvanized insulation
Compared with its predecessors, this material has a list of advantages:
- Corrosion under the shell is slowed down by tens of percent.
- If soil is laid on top of a pipe coated with polyethylene and polyurethane foam, the construction of a box or other additional insulation is not required.
- Heat loss is at a low level, despite the humidity, unlike glass wool, which, if the outer shell is damaged, noticeably deteriorates its thermal insulation qualities. Pipes with factory-made polyurethane foam insulation have heat loss of two to three percent, and not twenty to twenty-five, like other types.
- Installation is extremely easy.
PPU steel pipe – what is it?
Pre-insulated steel pipes
This product is a regular steel pipe for plumbing or heating, which is covered with a heat-insulating layer of polyurethane foam. Additional external protective coating, taking into account the use of the pipeline through the air (galvanized) or into the ground (polyethylene protective layer).
Installation
Laying polyurethane foam pipes consists of the following stages:
- Stripping the pipe insulation to a distance of up to 30 cm from each edge;
- Welding at joints, as well as checking with a flaw detector. The ends of the thermal insulation must be protected during the process;
- The heat shrink sleeve is placed on the pipe;
- The cavity under the coupling is filled polyurethane foam. After this, the device heats up and settles. This ensures tightness.
In short, the installation is done quite quickly.
Pipes in thermal insulation
It should be noted that laying heating mains is not always accompanied by digging a trench. In some cases, the horizontal drilling method is used. But how can pipes be insulated if they are pulled through a horizontal puncture in the ground? It is precisely for these cases that pipes in polyurethane foam insulation will be relevant.
Perhaps, laying polyurethane foam pipes in an apartment is unlikely; it would be much more effective to install hot water or heating using this method in a house or in a large warehouse.
Installation of heating mains is carried out using steel pipes with a thermal insulation layer of polyurethane foam. In the cross-section of such pipes, three layers are visible: the inner one is a working pipe made of steel, then there is a thick insulating polyurethane foam (PPU), and on the outside there is a layer of galvanized or polyethylene shell.
Thermal insulation protects the main pipeline from heat losses when installed underground and above ground, increases the service life of pipes up to 30 years and reduces the cost of repairing heating mains by 3 times.
An important condition for achieving these properties is reliable insulation of the joints of polyurethane foam pipes - the areas where two pipeline elements are connected. At the junction of two sections of the pipeline there is no thermal insulation layer, which is why the engineering structure becomes vulnerable and requires additional thermal protection. To reliably insulate the joints of polyurethane foam pipes, several types of insulation are used.
When installing main pipelines of urban heating networks, as well as when arranging systems autonomous heating Several methods are used to seal the joints of polyurethane foam pipes:
- shell;
- coupling;
- pouring.
Each of them fits certain pipeline criteria: installation method, expected service life and operating conditions, type of outer insulating layer, design values of coolant pressure and temperature, and others.
How to install an insulation layer
The fundamental factor in choosing the type of joint insulation is the method of laying pipes - underground, above-ground, channel, non-channel. The coupling method of insulating the joints of polyurethane foam pipes shows itself to be universal, which is suitable for any method of laying pipes. It is used almost everywhere, and further we will talk about it.
Joint sealing methods
The coupling method involves the use of special heat-shrinkable sleeves made of radiation cross-linked polyethylene. Couplings are hollow cylinders that are almost equal in diameter to the main pipeline.
The cost of heating is largely determined by the quality of heating networks. Matter right choice pipe diameter, laying depth, as well as insulation parameters. Complete all necessary calculations and only professionals can carry out high-quality installation. EnergoStroyTechService LLC is engaged in the repair and installation of heating networks in PPU thermal insulation. Great experience in this area and the presence of qualified specialists on staff allow us to provide high level fulfillment of the most complex projects, and the use of quality modern materials- achieve excellent technical and operational parameters of the heating main.
Design features
According to their purpose, heating networks are divided into the following types:
- distribution. Designed to supply coolant to individual buildings;
- main. They are laid on base lines in populated areas.
Depending on the type of network, it may consist of the following structural elements:
- pipes connected by welding or flanging;
- valves (shut-off, control) and compensators;
- drainage, air-bleeding devices;
- supports for pipelines, etc.
Centralized heating provides closed system pipes through which the medium circulates (most often water, since it is characterized by high accumulating capacity). IN simple systems There is one main highway, in more complex ones there are several.
Features and advantages of PPU insulation
There are increased demands on materials, design and installation of networks, which is due to the significant operating pressure and temperature of the coolant. And the insulation characteristics determine the level of heat loss on the route. We suggest using PPU - polyurethane foam, which has high insulating properties. Compared to traditional materials used when laying such lines, it provides the following basic advantages:
- reduction of heat loss up to 40%;
- increased service life - for polyurethane foam it is about 30 years instead of the usual 10-15;
- reduction of repair costs (3 times).
Methods for laying heating mains with PPU insulation
Before laying, our specialists analyze the type and composition of the soil, climatic features areas, study the location of existing communications and other nuances. Based on this, they design the heating network and determine the scope of work. The pipe laying scheme should be carried out along the shortest route possible in order to optimize the costs of constructing the heating main. It is also necessary that it runs parallel to existing communications or above them. This will prevent damage to existing lines.
According to the installation method, heating networks are divided into the following types:
- above ground. The pipes are located above ground level, on specialized support structures. This scheme is most often used in production areas, outside settlements. It is also recommended for high groundwater levels;
- underground. Pipelines can be laid in channels (semi-through, through or non-through) or without them. If the air in the ducts warms up to a temperature of 50 °C or more, it is necessary to provide mechanical or natural ventilation.
The use of pipes in a ready-made polyurethane foam shell eliminates the need for expensive channel method gaskets, saving about 35 ± 5% on installation alone. This is due technical features heating system components. Pipes are supplied from the factory already in PPU insulation; their diameter varies, which ensures the choice of elements for a specific pipeline. The installation itself is quick and simple: individual factory pipe blocks are laid in a prepared trench using a truck crane and connected to each other by welding. As necessary, additional structures are installed and trenches are filled up. After installation, the pipeline is tested and put into operation.
To clarify details or order installation of a heating network in modern PPU insulation, call EnergoStroyTechService by phone, contact our specialists online or by email.
Polyurethane foam (PPU) is considered one of the best heat-insulating materials, the use of which in pipe production saves money on the installation and operation of networks. PPU pipe - simple design, consisting of two pipes of different diameters nested inside each other.
The free space between the pipes is filled with thermal insulating material, and the protective layer for the pipes is made by applying a galvanized steel coating over the pipes or polyethylene, which increases the service life of the product and also expands the scope of application.
Pipelines based on polyurethane foam pipes are found today in almost all areas of the national economy:
- water supply networks (both hot and cold);
- industrial pipelines;
- heating mains;
- oil and gas pipelines.
The use of polyurethane foam pipes (compared to traditional pipe material) reduces network maintenance costs by up to 9 times, and repair costs by up to 3 times.
Products are produced exclusively in factory workshops equipped necessary equipment. To the working pipe required diameter A layer of polyurethane foam of a certain thickness is sprayed, on top of which an outer coating of galvanized or polyethylene is applied.
Pay attention! There is an alternative manufacturing technology, when instead of spraying a layer of insulation, a polyurethane shell is used required thickness. The shell is made separately and fixed to the pipe using ties.
Manufacturers of polyurethane foam pipes
Two enterprises are considered recognized leaders in pipe products with polyurethane foam insulation in Russia:
- Moscow company “Mezhregionteplosetenergoremont TsTS”,
- "Tatteploizolyatsiya" from Tatarstan. Works on Finnish equipment, allowing the production of about 1,700 linear meters finished product per day.
- SKTK,
- Chelyabinsk "Bizol"
- Ural Thermal Insulation Plant,
- LenSpetsStal,
- Thermal insulation plant from St. Petersburg.
PPU pipe design
The standard product consists of three layers:
- The main working pipe, which is made of high-strength steel, meets all GOST standards.
- Polyurethane foam insulation - high-tech synthetic material protects the pipe from moisture (hygroscopicity), does not allow contaminants to accumulate on the walls of the pipes, increases the service life and retains heat in comparison with the glass wool used for insulation in pipes of the previous generation.
- Shell - insulation layer can be protected by galvanization or polyethylene. The type of shell is determined by the markings on the product.
- Installation work on ductless laying of heating networks using thermally insulated pipes and elements should be carried out in accordance with the requirements of SNiP 41-02-2003 “ Heat networks", SP 41-105-2002 "Design and construction of ductless heating networks made of steel pipes and industrial thermal insulation made of polyurethane foam in a polyethylene shell."
- Installation of pipelines from thermally insulated pipes and elements should be carried out in strict accordance with project documentation. Any deviation, up to an oblique joint, must be agreed upon with the design and operating organizations.
- The development of trenches for channelless laying of pipelines using thermally insulated pipes and elements should be carried out mechanically in compliance with the requirements of SNiP 3.02.01-87 " Earthworks. Foundations and foundations" and supplemented requirements of the "Production Rules earthworks in Moscow."
- Before installing a pipeline section, the insulation condition and integrity of the signal wires of the UEC system are checked. Installation of a heating network from elements whose insulation resistance is less than 10 MOhm is strictly prohibited.
- Flooding of the route with water is strictly unacceptable!
- Thermal insulation welded joints on the route and filling the heating pipes with sand is carried out after hydraulic test this section for strength and density, as well as after re-measuring the insulation resistance for each element. Work on insulating joints is carried out at the request of the customer, the submission of which guarantees the possibility of carrying out these works.
- When performing work on insulating joints, the following types of work are subject to acceptance with the preparation of inspection reports:
- visual inspection of the condition of the polyethylene shell and the moisture content of the polyurethane foam (traces of flooding);
- control check of wire integrity and measurement of insulation resistance;
- preparing the surface of steel pipes for filling with a mixture of polyurethane foam;
- connection of wires of the UEC system;
- installation of an electric welded coupling;
- pneumatic testing of the installed coupling;
- decoding of loggers and permission for uploading by the quality control department;
- filling joints with polyurethane foam;
- waterproofing of the heat-insulating layer of joints (use of heat-shrinkable material at joints of type MFL - 1000M, welding of plugs for joints of type MFL - 1000, MFL - 1000M); - Before laying, pipes and pipeline elements are carefully inspected for cracks, chips, deep cuts, punctures, ruptures and other mechanical damage to the polyethylene thermal insulation shell.
- Lowering insulated pipes into a trench should be carried out as planned, without jerking or hitting the walls and bottom of channels and trenches. Before laying pipes in trenches or channels in mandatory check the integrity of the conductors of the UEC system.
- Heat pipelines laid on a sandy base should not rest on stones, bricks and other solid inclusions, which should be removed, and the resulting depressions should be filled with sand (compacted with a tamper).
- When installing pipes, it is necessary to ensure that the wires of the UEC system are located in the upper part of the joint, and to protect the ends of the wires from mechanical damage. The metal seam of the pipe is located at the top. When welding, the longitudinal seam of adjacent elements should be positioned with a shift of at least 100 mm. When installing, the bends must be marked with the manufacturer's markings and welded seam metal pipes up.
Avoid placing signal wires in the lower quarter of the joint.
- The installation of the pipeline element with the output cable is carried out taking into account the direction of supply of the coolant. The control arrow on the shell must coincide with the direction of coolant supply to the consumer. On return pipe installation of the element with the output cable is carried out in the direction
straight pipe coolant supply. It is not recommended to install a piping element with an output cable near an outlet.
Attention!
If it is necessary to adjust the pipes to construction site, cutting of the polyethylene shell is carried out first in the transverse direction, then to remove the shell of the removed insulation fragment, cutting is performed in the longitudinal direction. Particular attention must be paid to avoid sawing the shell further than the cut part (see figure), in order to avoid the formation of cracks on the polyethylene shell.
- Steel pipes are cut using a gas cutter, during which the thermal insulation is removed hand tools, and the ends of the thermal insulation during the cutting of steel pipes are covered with protective screens. The end of the thermal insulation must be perpendicular to the axis of the pipe.
- The angular deviation for metal in straight sections is allowed within 2.5°, which is within the permissible limits for insulating joints of types 1000M, 1000R, 1000MR and their modifications. If the angular deviation in the metal of a straight pipe exceeds 2.5°, it must be agreed upon with the operating and design organizations.
- Installation of pipelines in a polyethylene sheath with thermal insulation made of polyurethane foam is carried out at an outside air temperature of at least minus 15°C. When working with pipes in the temperature range from 0°C to minus 15°C, cutting the shell must be done with preheating gas burner up to tо = +5 ÷ +15оС.
You should carefully remove with a scraper all remaining foam material that may release environmentally unsafe substances when burned. When performing welding work, it is necessary to install protection of polyurethane foam and polyethylene sheathing, as well as the ends of the wires coming out of the insulation, from sparks (protective screens).
- Subject to availability concrete base installation work must be carried out on a sand bed with a height of at least 300 mm.
- After welding the ends of the steel pipes, clean the outer surface of the joint area from traces of rust using metal brushes.
- Pipelines are usually installed at the bottom of a trench with pits installed. It is allowed to weld straight sections of pipes in a braid on the edge of a trench at a temperature of +10°C and above. It is recommended to place sandbags under the pipes. Acceptable use wooden beam with a cross-section of at least 100x100 mm followed by removal.
- When backfilling special attention You should pay attention to the installation of polyethylene mats, which serve to absorb expansion at corners of rotation, branches and expansion joints. Polyethylene mats are placed vertically, close to the outer shell. The height of the mats should be larger diameter outer shell by 100 mm. If the expansion is less than 10 mm, polyethylene mats are not used. The need for installation and the number of mats is determined by calculation.
- At the corners of pipelines, corners U-shaped expansion joints and straight sections (in the absence of terminals), signal posts are installed every 300 m. For pipelines in polyethylene sheath backfill to be carried out no later than two weeks after the work on insulating the joints is carried out.
- When laying pipelines in cases, use only pipes with a reinforced shell.
- When ordering a pipe in a reinforced shell, it is necessary to specify the minimum internal diameter of the case based on the diameter of the reinforcement ring plus 50 mm (Dt+50mm). To be able to carry out work on insulating joints, the pipe in the reinforced casing must extend beyond the casing by at least 500 mm.
- The fixed support is factory-produced and delivered to the site. Shield fixed support(concrete + reinforcement) is installed in accordance with design documentation developed for real forces and soil type. Welding steel reinforcement to the fixed support shield is strictly prohibited.
- When installing vertically located pipeline elements, it is necessary to provide protection against the ingress and accumulation of moisture at the joints of each lower end of the insulation. It is recommended to use working insulation plugs (issued as an additional order to the contract). It is acceptable to use polyethylene film with tape fixation.
If the installation organization fails to provide timely protection from the ingress and accumulation of moisture at the ends of the insulation of vertically located pipeline elements, renovation work will be made at her expense.
- If it is necessary to reduce the geometric dimensions of the unit, the reduction should be made by changing the length of the straight pipe or reducing the lengths of the bases of tees, tee branches and parallel tees in accordance with the table of ΔL values.