Insulated pipe

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District heating pipeline from Lower Austria Fernwarmeleitung in der Theresienstrasse in Hausmenning.jpg
District heating pipeline from Lower Austria
Elbow with foam pads of a District heating pipeline with a steel tube diameter of 400 mm installed in Lower Austria Dehnpolster.jpg
Elbow with foam pads of a District heating pipeline with a steel tube diameter of 400 mm installed in Lower Austria

Insulated pipes (called also preinsulated pipes or bonded pipe [1] ) are widely used for district heating and hot water supply. They consist of a steel pipe called "service pipe", a thermal insulation layer and an outer casing. The insulation bonds the service pipe and the casing together. The main purpose of such pipes is to maintain the temperature of the fluid inside the service pipes. Insulated pipes are commonly used for transport of hot water from district heating plants to district heating networks and for distribution of hot water inside district heating networks.

Thermal insulation material usually used is polyurethane foam or similar, with a thermal conductivity λ50 of about 0.024–0.033 W/(m·K). While polyurethane has outstanding mechanical and thermal properties, the high toxicity of the [diisocyanates] required for its manufacturing has caused a restriction on their use. [2] This has triggered research on alternative insulating foam fitting the application, [3] which include polyethylene terephthalate (PET) [4] and polybutylene (PB-1). [5] The outer casing is usually made of high-density polyethylene (HDPE). Preinsulated pipes for district heating are described in European standards EN 253 and EN 15698-1. EN 253 describes "District heating pipes - Bonded single pipe systems for directly buried hot water networks - Factory made pipe assembly of steel service pipe, polyurethane thermal insulation and a casing of polyethylene". EN 15698-1 describes "District heating pipes - Bonded twin pipe systems for directly buried hot water networks - Factory made twin pipe assembly of steel service pipes, polyurethane thermal insulation and one casing of polyethylene". Both standards don't give "short names" or abbreviations for described pipes.

According to EN 253:2019 & EN 15698-1:2019, pipes must be produced to work at constant temperature of 120 °C (248 °F) for 30 years. Thermal conductivity λ50 in unaged condition shall not exceed 0.029 W/(m·K). Both standards describe three insulation thickness levels. Both standards require use of polyurethane foam for thermal insulation and HDPE for casing.

Insulated pipelines are usually assembled from pipes of 6 metres (20 ft), 12 metres (39 ft), or 16 metres (52 ft) in length, directly buried in soil in depths of commonly 0.6–1.2 metres (2 ft 0 in – 3 ft 11 in).


See also

Related Research Articles

<span class="mw-page-title-main">Polyurethane</span> Polymer composed of a chain of organic units joined by carbamate (urethane) links

Polyurethane refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from a wide range of starting materials. This chemical variety produces polyurethanes with different chemical structures leading to many different applications. These include rigid and flexible foams, and coatings, adhesives, electrical potting compounds, and fibers such as spandex and polyurethane laminate (PUL). Foams are the largest application accounting for 67% of all polyurethane produced in 2016.

<span class="mw-page-title-main">Thermal insulation</span> Minimization of heat transfer

Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.

<span class="mw-page-title-main">Thermoplastic</span> Plastic that softens with heat and hardens on cooling

A thermoplastic, or thermosoftening plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling.

<i>R</i>-value (insulation) Measure of how well an object, per unit of area, resists conductive flow of heat

In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference per unit of heat flux needed to sustain one unit of heat flux between the warmer surface and colder surface of a barrier under steady-state conditions. The measure is therefore equally relevant for lowering energy bills for heating in the winter, for cooling in the summer, and for general comfort.

<span class="mw-page-title-main">District heating</span> Centralized heat distribution system

District heating is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from factories and nuclear power electricity generation. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, district heating with combined heat and power (CHPDH) is the cheapest method of cutting carbon emissions, and has one of the lowest carbon footprints of all fossil generation plants.

<span class="mw-page-title-main">High-density polyethylene</span> Class of polyethylenes

High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, HDPE is used in the production of plastic bottles, corrosion-resistant piping, geomembranes and plastic lumber. HDPE is commonly recycled, and has the number "2" as its resin identification code.

Cross-linked polyethylene, commonly abbreviated PEX, XPE or XLPE, is a form of polyethylene with cross-links. It is used predominantly in building services pipework systems, hydronic radiant heating and cooling systems, domestic water piping, insulation for high tension electrical cables, and baby play mats. It is also used for natural gas and offshore oil applications, chemical transportation, and transportation of sewage and slurries. PEX is an alternative to polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC) or copper tubing for use as residential water pipes.

<span class="mw-page-title-main">Trace heating</span>

Electric heat tracing, heat tape or surface heating, is a system used to maintain or raise the temperature of pipes and vessels using heat tracing cables. Trace heating takes the form of an electrical heating element run in physical contact along the length of a pipe. The pipe is usually covered with thermal insulation to retain heat losses from the pipe. Heat generated by the element then maintains the temperature of the pipe. Trace heating may be used to protect pipes from freezing, to maintain a constant flow temperature in hot water systems, or to maintain process temperatures for piping that must transport substances that solidify at ambient temperatures. Electric trace heating cables are an alternative to steam trace heating where steam is unavailable or unwanted.

<span class="mw-page-title-main">Polyisocyanurate</span> Type of plastic typically used for thermal insulation

Polyisocyanurate, also referred to as PIR, polyiso, or ISO, is a thermoset plastic typically produced as a foam and used as rigid thermal insulation. The starting materials are similar to those used in polyurethane (PUR) except that the proportion of methylene diphenyl diisocyanate (MDI) is higher and a polyester-derived polyol is used in the reaction instead of a polyether polyol. The resulting chemical structure is significantly different, with the isocyanate groups on the MDI trimerising to form isocyanurate groups which the polyols link together, giving a complex polymeric structure.

Insulation may refer to:

Seasonal thermal energy storage (STES), also known as inter-seasonal thermal energy storage, is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever needed, such as in the opposing season. For example, heat from solar collectors or waste heat from air conditioning equipment can be gathered in hot months for space heating use when needed, including during winter months. Waste heat from industrial process can similarly be stored and be used much later or the natural cold of winter air can be stored for summertime air conditioning.

<span class="mw-page-title-main">Building insulation</span> Material to reduce heat transfer in structures

Building insulation is material used in a building to reduce the flow of thermal energy. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation. Often an insulation material will be chosen for its ability to perform several of these functions at once.

<span class="mw-page-title-main">Building insulation material</span>

Building insulation materials are the building materials that form the thermal envelope of a building or otherwise reduce heat transfer.

Polybutylene (polybutene-1, poly(1-butene), PB-1) is a polyolefin or saturated polymer with the chemical formula (CH2CH(Et))n. Not be confused with polybutene, PB-1 is mainly used in piping.

<span class="mw-page-title-main">Fan coil unit</span> HVAC device

A fan coil unit (FCU), also known as a Vertical Fan Coil-Unit (VFC), is a device consisting of a heat exchanger (coil) and a fan. FCUs are commonly used in HVAC systems of residential, commercial, and industrial buildings that use ducted split air conditioning or with central plant cooling. FCUs are typically connected to ductwork and a thermostat to regulate the temperature of one or more spaces and to assist the main air handling unit for each space if used with chillers. The thermostat controls the fan speed and/or the flow of water or refrigerant to the heat exchanger using a control valve.

<span class="mw-page-title-main">Pipe insulation</span>

Pipe Insulation is thermal or acoustic insulation used on pipework.

<span class="mw-page-title-main">Plastic pipework</span> Tubular section or hollow cylinder made of plastic

Plastic pipe is a tubular section, or hollow cylinder, made of plastic. It is usually, but not necessarily, of circular cross-section, used mainly to convey substances which can flow—liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipes are far stiffer per unit weight than solid members.

<span class="mw-page-title-main">Armacell</span>

Armacell is a manufacturer and supplier of industrial foams and flexible insulation materials, based in Luxembourg. It has over 3,135 employees and 25 production plants in 16 countries.

HDPE pipe is a type of flexible plastic pipe used for the transfer of fluids and gases, often used when replacing aging concrete or steel mains pipelines. Constructed from the thermoplastic HDPE, it has high impermeability and robust molecular bonding, making it suitable for high pressure pipelines. HDPE pipe is often used for water mains, gas mains, sewer mains, slurry transfer lines, rural irrigation, fire system supply lines, electrical and communication conduits, stormwater pipes, and drainage pipes.

References

  1. "Catalog of a manufacturer; page 2.0.0.1". Archived from the original on 2012-03-21. Retrieved 2011-03-13.
  2. Commission Regulation (EU) 2020/1149 of 3 August 2020 amending Annex XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) as regards diisocyanates: (EU) 2020/1149. In: Official Journal of the European Union; 2020.
  3. Doyle, Lucía (2022). A Circular Economy Approach to Multifunctional Sandwich Structures: Polymeric Foams for District Heating Pre-Insulated Pipes (Thesis). HafenCity Universität Hamburg. doi:10.34712/142.35 . Retrieved 2023-01-23.
  4. Doyle, Lucía; Weidlich, Ingo (2021). "Sustainable insulation for sustainable DHC". Energy Reports. Elsevier BV. 7: 150–157. doi: 10.1016/j.egyr.2021.08.161 . ISSN   2352-4847. S2CID   240180109.
  5. Doyle, Lucía (2021). "Extrusion foaming behavior of polybutene‐1. Toward single‐material multifunctional sandwich structures". Journal of Applied Polymer Science. Wiley. 139 (12): 51816. doi: 10.1002/app.51816 . ISSN   0021-8995. S2CID   240464626.