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Pre-insulated pipe technique EN 253

pre-insulated pipes EN 253

When ordering, specify:

  • outer diameter of the service pipe, wall thickness and length of pipeline
  • label of material of the service pipe
  • temperature of the medium flowing through the service pipe
  • pressure of the medium in the service pipe

Areas of application:

  • District heating
  • heating pipelines
  • hot water
  • Oil Pipelines
  • Industrial Fluids
  • Home installation
  • Petrol pumps (gas stations)

For systems of pre-insulating pipes technique our company provide:

  • Development of technical documentation
  • Complete purchase of materials and equipment
  • Perform of all works
  • Putting the system into operation
  • Maintenance of the system

Advantages of pre-insulated pipes technology are following:

  • Pre-insulation is done in the factory, which enables efficient control of product quality
  • Pipes are quickly and easily laid into earth channels, which helps eliminate expensive concrete channels
  • Hard polyurethane foam is an extraordinary insulator, with long-lasting stability of thermo mechanical properties
  • Outer tube made ​​of polyethylene of high density represents an efficient mechanical and chemical protection insulation

dimensions of pre insulated pipes

Polyurethane products based on cyclopentane

Following the European norm EN 253, in terms of foaming of polyurethane mass, AD “IZOLIR” with the purchase of the latest technology equipment for pre-insulation and rigging polyurethane mass manages to follow the modern trends of technology and from the second half of 2005. produce polyurethane foam based on cyclopentane.

Rigid polyurethane foam

Rigid polyurethane foams are good insulators because they consist of 92% – 98% closed cells that are filled with insulating gas. The composition of gas in the cell is the basic factor of the thermal conductivity of polyurethane foam.

The advantage of polyurethane foam based on cyclopentane compared to polyurethane foam based on CO2


Characteristics of polyurethane foam some determinate insulating value, i.e. initial thermal conductivity. According to EN 253 standard, the thermal conductivity of pre-insulated pipes must not be greater than 0029 mW / mK at temperature of 50 ° C. Through a certain time come to change of this value because of changes in the composition of the gas in cells of polyurethane foam, which leads to a change in the value of thermal conductivity.
In the polyurethane foam based on CO2 (carbon dioxide) foaming after a short time carbon dioxide inside the cellular structure of polyurethane foam begins to release and exchange with air and on this way increases the thermal conductivity of polyurethane foam, while cyclopentane gas has a lower diffusion value so cell’s structure longer keeps presence of cyclopentane with better i.e. smaller thermal conductivity and on that way polyurethane foam longer keeps it’s thermal properties.

The graph presents the results of laboratory’s tests of accelerated aging of polyurethane foam of pre-insulated pipes with expressed increase of the value of thermal conductivity of polyurethane foam in function of time.

Area of use:

IZOPEN pre-insulated pipes are in the standard version designed for the transport of fluids of different continuous temperatures up to 130 degrees C, with the allowed jumps of temperatures up to 150 degrees C (IZOPEN PC130). The same pre-insulated pipes are produced in variants for work with higher continuous temperatures to 140 ° C and allowed short-term jumps up to 150 ° C. For transport of fluids with temperature to 200 degrees C are intended pre-insulated pipes with combined insulating layers (IZOPEN PC200). IZOPEN PC130 – technical characteristics:

IZOPEN PC130 pre-insulated pipes are consisted of the following elements:
1. Service pipe for the flow of the working fluid
2. Polyurethane foam
3. The outer protective pipe

Service pipe

a) black steel seamless pipe according to EN 10216-2, DIN 1629
(label of the material: P235GH, St 35.8, St 37.0)
b) black steel welded pipe according to EN 10217-2, EN 10217-5, DIN 1626
(label of the material: P235GH, St 35.8, St 37-2) )
* Dimensions of steel pipe are from Ø26, 9×2, 6mm to Ø1016x10mm, shape and dimensions are in compliance with EN 10220, up to 12 m.
At the request of the customer, service pipe may be galvanized steel pipe, polypropylene pipe, polyethylene pipe, aluminum, copper …

Polyurethane insulation foam

Polyurethane insulation foam is the space between the service pipe and the outer protective pipe filled with rigid polyurethane foam with controlled following characteristics of the sample:
– Coefficient of thermal conductivity less than 0.029 W / mk
– Density of the foam – not less than 60 kg / m³
– Compressive strength in the radial direction at 10% deformation min 0.30 Mpa
– Resistance to shear 0.26 MPa
– Flammability class is according to DIN 4102 B3
– Foam is non-toxic

The outer protective pipe

Made of high density polyethylene EN 253 (DIN 8074), with dimensions Ø90-1200mm in length up to 12m, with the following characteristics
– Min density of 944 kg / m³
– Coefficient of thermal conductivity of 0.42 W / mK
– Softening temperature according to Vicat 121-124 ° C
– Elongation at break min. 350%
– Yield strength min. 19Mpa
– Resistant to the effects of moisture, salt water, various acids and bases Solvent
– As per customer request, the external protective coating can be made of aluminum or galvanized tin, thickness 0.7-1mm




Pre-insulated steel pipe with an accompanying electric heating

For the transport of process fluids with pre-insulated pipes for long distances, where is necessary to keep constant temperature of the fluid or if is necessary to additionally heat fluid to the required temperature during transport has been developed longitudinal electric heater that can be designed to satisfy both requirements.

Basic characteristics of the extended electric heaters:

  • Unit capacity up to 200W / m
  • Operating temperature to 200 ° C
  • On request can be issued to heaters with higher parameters

Advantages of extended electric heater:

  • Constant heating power along the route
  • Exceptional length of the heater (up to 5km with one power supply)
  • Excellent mechanical resistance
  • High reliability
  • Heater interchangeability without destroying the insulation
  • Precise temperature control

For the extended heating system our company provides:

  • preparation of technical documentation
  • Complete purchase of materials and equipment
  • Perform of all works
  • Putting the system into operation
  • Proving of design parameters
  • Maintenance of the heating systems

dimenzije predizolovanih cevi sa propratnim grejanjem


Other elements

End cap

End caps are for frontal protection against moisture of PUR foam at the ends of pipes.

End caps must be made of one piece and without damage. To ensure proper thermal shrinkage, it must be provide required overlapping between cap and polyethylene pipes.

End caps are available in all combinations of steel and polyethylene pipes according to the standard.

End cap is made of thermo shrinkable polyethylene, which can’t be melt. At each end cap is a layer of special sealing glue which is resistant to temperature.

End caps are resistant to: heat ageing, weathering, chemical influences and UV radiation.

Passage through the wall – a standard rubber ring (gasket)

Rubber rings are used to prevent water penetration during passage pipline through the wall.

Standard rubber ring consists of a specially profiled rubber ring. Rubber ring is resistant to aging, atmosphere conditions and chemical influences.

Standard rubber rings are placed in the middle of the wall opening, then it is necessary to concreting the same.
When installing the rings it would be desirable to perform as precisely as possible at right angle to the wall.

Improper installation leads to unsealing.

Expansion pillows

Expansion pillows are used to absorb the movement of pre-insulated pipes to the L-, Z-and U-arches the branches, reductions, the final joints, the valves and the high and low points of heating system.

Expansion pillows are made of closed cell formed from polyethylene which performs a full protection of the outer diameter of pre-insulated pipe.




Alert system for measuring moisture and detection of break in the route

Isotronic – surveillance system is a system that is placed in pre-insulated pipe system as a control unit that monitors and controls the functionality of pre-insulated systems and alarm the possible presence of moisture or break in the route.


The system contains the following elements:


  • pair of measuring wires, copper conductor (wires “A”) and tin conductor (wire “B”)
  • locators, which in the system build resistance of ≥ 20 M-Ohms, while during penetration of moisture resistance is decreases and  signal the error. Locators are used to precisely and closer locate occurred error.
  • Splitter, which signally divides secondary pipeline from the primary in order to identify possible made mistakes. Splitters are placed inside each branch.
  • Measuring boxes, placed at the pipe ends (household endings, manholes, substations, boiler rooms).
  • Central control unit of the new generation “TRA 2002 GSM” (with built-in Global System for Mobile Communication modem) monitors the route of max. 6 km. Placed at the beginning of the route or the substation. Thanks to GSM-modem, which is incorporated in each device, the supervisory unit can be accessed from any computer with a GSM modem.


All measuring values ​​are processed in the supervisory unit; and a values for settings ​​can be configured.
In the case of falling below or exceeding the the configured measurement values​​, the user is notified via e-mail or via SMS.
The database is kept last 500 measurement values. From the database can also be printed graphic characteristics of measured values.


Pre-insulated steel pipes EN 253 PC200

IZOPEN PC200 are used to transport fluids that reaches operating temperature up to 200 ° C. They have the same elements as IZOPEN PC130, with the same characteristics of the service pipe, and the outer protective pipe. The essential difference is in the insulating sheath.

Insulated sheath of pre-insulated pipe IZOPEN PC200 is combined with a layer of mineral wool on the tar paper (the first layer to the service pipe) and rigid polyurethane foam (second layer).


Properties of rigid polyurethane foams are the same as those at PC130 IZOPEN pipe, while the characteristics of mineral wool are following:


  • density up to 100kg / m³
  • coefficient of thermal conductivity at 100 ° C around 0.05W/mk
  • incombustible (nonflammable) material


spirofalz coated pipes

Spirofalz pipes are used for covering pre-insulated pipes for aboveground pipelines. They can be manufactured from aluminum with a thickness of 0.7 to 1 mm, and of galvanized tin thickness of 0.5 to 0.7 mm. Length of pipe diameters up to Ø 139.7 mm is 6 m, and for larger diameters up to 12 m.

The standard version diameters are done according to EN 253 Pipes can be made by special request too, according to necessary thickness of insulation and type of insulation. Isolation can be from polyurethane foam or it can be combined insulation with mineral wool and polyurethane foam.

We perform the preparation works on the installation of the pipeline, i.e. we factory install supports before the pre-insulation of the aboveground quide of the pre-insulated pipes.

Pre-insulated pipes in coated with spirofalcz may be protected with a waterproof aluminum foil, resistant to UV rays.



IZOLIR is the first domestic factory and leader in the field of pre-insulated pipes for district heating and following equipment, as well as in manufacturing pre-insulated pipes for high pressure gas pipelines.

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