HDPE pipe: Difference between revisions

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{{Short description|Type of flexible plastic pipe}}

{{third-party|date=April 2019}}

{{advert|date=April 2019}}

'''HDPE pipe''' is a type of flexible [[plastic]] [[Pipe (fluid conveyance)|pipe]] used for [[fluid]] and [[Gastrointestinal tract|gas]] transfer and is often used to replace ageing concrete or steel mains pipelines. Made from the [[thermoplastic]] [[HDPE]] (high-density [[polyethylene]]), its high level of impermeability and strong molecular bond make it suitable for high pressure pipelines. HDPE pipe is used across the globe for applications such as water mains, gas mains,<ref>{{Cite web|url=http://www.pipa.com.au/wp-content/uploads/2018/09/tn004.pdf |title=PIPA Technical Paper on Polyethylene used for Gas Pipe Material }}</ref> sewer mains, slurry transfer lines, rural irrigation, fire system supply lines, electrical and communications conduit, and stormwater and drainage pipes. However, most United States municipal governments restrict its use on public works projects.

'''HDPE pipe''' ('''high-density polyethylene pipe''') is a type of flexible [[plastic]] [[Pipe (fluid conveyance)|pipe]] used to transfer [[fluid]]s and [[gas]]es. It is often employed for replacing aging [[concrete]] or [[steel]] main [[Pipeline|pipelines]]. Constructed from the [[thermoplastic]] [[HDPE]] (high-density [[polyethylene]]), it has low [[Permeability (Earth sciences)|permeability]] and robust molecular bonding, making it suitable for high-pressure [[Pipeline|pipelines]]. HDPE pipe is often used for [[Water distribution system|water mains]], [[Gas main|gas mains]],<ref>{{Cite web|url=http://www.pipa.com.au/wp-content/uploads/2018/09/tn004.pdf|title=PIPA Technical Paper on Polyethylene used for Gas Pipe Material|last=Stahmer|year=2008|language=en|website=Plastics Industry Pipe Association of Australia}}</ref> [[Sewerage|sewer]] mains, [[slurry]] transfer lines, rural [[irrigation]], [[Fire suppression system|fire-suppression system]] supply lines, [[Electrical conduit|electrical]] and communication conduits, and [[stormwater]] and [[drainage]] pipes.<ref>{{Cite web|title=HDPE|url=https://www.plasticpipe.org/PowerCommunications/BuildingConstruction/HDPE.aspx|access-date=2023-11-22|website=Plastics Pipe Institute|language=en|date=<!--not stated-->}}</ref><ref>{{Cite web |last=Ireland |first=Beck |date=1 September 2009 |title=Fast, Cheap, and Out of Control? |url=https://www.ecmweb.com/design/fast-cheap-and-out-control |website=Electrical Construction & Maintenance |publisher=[[Endeavor Business Media]]}}</ref>

== Benefits ==

The toughness and resistance to chemicals of [[polyethylene]], as well as the corrosion resistance and low weight have contributed to its growing use in situations where cost-effective and durable fluid and gas piping systems are required. According to a press release from the Plastics Pipe Institute, "PE piping has been used for water and other fluids in Europe and America since the 1950s due to its durability, leak free joints, resistance to corrosion, and long-term cost-effectiveness."<ref>{{Cite web |url=https://plasticpipe.org/pdf/press-release-jana-lab-tech-report.pdf |title=Plastics Pipe Institute study confirms long life expectancy for polyethylene pipe in municipal water systems. }}</ref>{{Self-published inline|date=April 2019}}

It is frequently used in [[pipe bursting]].

HDPE pipe can be joined by [[butt welding]], [[electrofusion welding]], socket welding, or [[extrusion welding]]. These joints heat the pipe during the joining process, creating a completely homogeneous joint so the weld becomes as strong, or stronger than the existing pipe on either side of the weld. There is no need to use rubber seals or jointing chemicals, as is used for joining PVC pipe, which cause environmental health issues and increase the chance of failure over time. PE is less likely to have problems with root intrusion, and provides integrity for the pipeline, even when installed in unstable soils.

==Attributes==

[[File:Acu-Tech HDPE Pipe being installed by directional drilling.jpg|thumb|HDPE communications conduit pipe being installed by [[directional drilling]] in Perth, Western Australia]]

[[File:Freshly Extruded 800mm HDPE Pipe at Acu-Tech Piping Systems.png|alt=Piping Systems - Extruded 800mm HDPE Pipe|thumb|Freshly Extruded {{convert|800|mm|in|2|abbr=on}}extruded HDPE Pipe]]

Due to the fusion welding system, the need for anchors or thrust restraint blocks are eliminated, as the joints become fully end load resistant, reducing costs for material and installation time. This also allows for safer excavation close to the pipeline in future, which is particularly important for high pressure gas pipelines. Coils of PE Pipe make [[Trenchless technology|trench-less installation]] safer and less intrusive on the surrounding environment.

[[File:Acu-Tech HDPE Pipe being installed by directional drilling.jpg|thumb|HDPE communications conduit pipe being installed by [[directional drilling]] in [[Perth]], Western Australia]]

[[File:120 inch HDPE pipe installation 3.jpg|thumb|120 inch HDPE pipe installation in [[Mexico City]]]]

HDPE is resistant to many environmental factors and has applications where cheap but durable fluid piping systems are required.

[[File:Electrofusion Welding of HDPE Pipe.jpg|thumb|[[Electrofusion welding]] of HDPE pipe]]

HDPE pipe systems are available for many applications, providing for standard trenching of water mains, fire ring mains, sewer mains, and gas mains pipelines, as well as horizontal drilling for electrical and telecommunications conduits.<ref>{{Cite web |url=https://www.ecmweb.com/design/fast-cheap-and-out-control |title=Article about the growth of HDPE Conduit systems, and their advantages over PVC Pipe. |last= |first= |date=September 2009}}</ref> According to a company that manufactures HDPE, HDPE systems are cost-effective to install and have long-term maintenance cost savings, and also allow for cheaper installation methods, such as [[Directional boring|HDD]] (horizontal directional drilling), [[sliplining]], [[pipe bursting]], floating and submerged pipe.<ref>{{Cite web |url=https://www.acu-tech.com.au/about-us/why-use-hdpe/ |title=Benefits of HDPE Pipe }}</ref>

[[File:Bonding HDPE for DX Groundwater Treatment Facility (7582956094).jpg|thumb|Bonding HDPE for DX Groundwater Treatment Facility at the [[Hanford Site]]]]

HDPE pipe can be joined by [[butt welding]], [[electrofusion welding]], socket welding, or [[extrusion welding]]. These joints heat the pipe during the joining process, creatingto create a completely homogeneous joint sowithout the weld becomes as strong, or stronger than the existing pipe on either side of the weld. There is no need tofor use rubberadditional [[Sealant|seals]] or [[Pipe dope|jointing]] chemicalscompounds, asreducing isthe usedlikelihood forof joiningfailure PVCor pipe, which causenegative environmental healtheffects. issuesHDPE andis increaseless thelikely chancethan of[[Polyvinyl failurechloride|PVC]] over time. PE is less likelypipe to have problems with root intrusion, and provides integrity for the pipeline, even when installed in unstable soils.{{Citation needed|date=February 2024}}

Due to the fusion welding system, HDPE pipe does not need any additional supports around joints. This also allows for safer excavation close to the pipeline in the future, which is particularly important for high-pressure gas pipelines. HDPE pipe is highly durable and flexible even at lower ambient temperatures, enabling bends in the pipe system to be created with relative ease. Due to its high impact resistance and flexibility, HDPE pipe is well-suited for installation in dynamic soils, including those in earthquake-prone areas. HDPE has been considered to be cost-effective due to its versatility in installation and reduced need for maintenance.{{cn|date=June 2024}}

HDPE pipe is very durable and flexible and can be bent on site to a radius twenty-five times the nominal pipe diameter - for SDR11 and SDR17 pipe, at or below 20°C ambient temperature. This provides major cost savings, when compared to different pipe systems, some of which require glued fittings, restraints or thrust blocks for even minor changes in direction. Because of the high impact resistance and flexibility of HDPE pipe, it is well suited to installation in dynamic soils including in earthquake-prone areas. HDPE pipe has very high flow capacity, because of its smooth bore and end-to-end jointing methods. HDPE pipe does not corrode in the environment, and will maintain its flow capabilities over time, unlike ferrous piping systems, which will rust and build up internal resistance to fluid flowing through it.<ref name="PIPA whitepaper">{{Cite web |url=http://www.pipa.com.au/wp-content/uploads/2018/09/tn013.pdf |title=PIPA Technical Whitepaper on 'Life Expectancy for Plastics Pipes' |publisher=Plastics Industry Pipe Association of Australia Ltd }}</ref>{{Self-published inline |date=April 2019}}

Because food-grade polyethylene [[Raw material|virgin material]] is used to fabricate HDPE pipes, they are safe for the transfer of [[drinking water]], provided that any initial debris has been flushed out. HDPE pipe is resistant to many chemicals, facilitating its use in [[Process plant|process plants]] or aroundin corrosive or acidic environments, without needinguse to useof protective coatings or galvanising, as is required on steel pipes[[galvanization]]. As HDPE has a very lowlower thermal conductivity, than many metals it can maintain more uniform temperatures compared tothan metal pipes when carrying fluids, which willreduces greatly reduce anythe need for insulation to control condensation around thea pipeline.<ref>{{Cite webbook |urltitle=https://plasticpipe.org/pdf/chapter08.pdfHandbook of Polyethylene Pipe |titlepublisher=ResearchCLVR onCompany |year=2012 |isbn=9781952632006 |edition=2nd |chapter=Chapter 8: Above-groundGround applicationsApplications for PE Pipe }}</ref>{{Self-published inline |date=April 2019}}

== Manufacture Manufacturing==

To make lengths of HDPE pipe, polyethylene raw material is dried, heated to ~{{convert|180|°C|°F}}, and extruded through a [[Die (manufacturing)|die]].

To make pipe lengths, HDPE resin is heated and extruded through a [[Die (manufacturing)|die]], which determines the diameter of the pipeline. The wall thickness of the pipe is determined by a combination of the size of the die, speed of the screw and the speed of the haul-off tractor. Polyethylene pipe is usually black in color due to the addition of 3-5% of [[carbon black]] being added to the clear polyethylene material. The addition of carbon black creates a product which is [[UV light]] resistant. Other colours are available but are less common. Coloured or striped HDPE pipe is usually 90-95% black material, with just a coloured skin or stripe on the outside 5%.

Polyethylene pipe is usually black due to the addition of 3-5% of [[carbon black]] to the clear polyethylene material, which adds [[UV light]] resistance to the finished pipe. To create striped HDPE pipe a different die is used, containing small channels that the colored material runs through just before it is pushed through the die. Co-extruded, or co-ex HDPE pipe has an extra 'skin' of color around the black HDPE pipe, allowing the pipe to be colored on the outside for the identification of thermal cooling requirements.

The following shows the process for HDPE Pipe Extrusion:

[[File:Freshly Extruded 800mm HDPE Pipe at Acu-Tech Piping Systems.png|alt=Piping Systems - Extruded 800mm HDPE Pipe|thumb|Freshly Extruded {{convert|800|mm|in|2|abbr=on}} HDPE Pipe]]

Polyethylene raw material is pulled from a silo, into the hopper dryer, which removes any moisture from the pellets. Then it is pulled by a vacuum pump into the blender, where it is heated by a barrel heater. The PE material becomes molten at around {{convert|180|°C|°F}}, allowing it to be fed through a mould/die, which shapes the molten material into a circular shape. After coming through the die, the newly formed pipe quickly enters the cooling tanks, which submerge or spray water at the pipe exterior, each one reducing the temperature of the pipe by 10-20 degrees. Because polyethylene has a high specific heat capacity, the pipe must be cooled in stages, to avoid deforming the shape, and by the time it reaches the "haul-off tractor", it is hard enough to be gently pulled by the 2-3 belts. A laser or powder printer prints the size, type, date and manufacturers name on the side of the pipe. It is then cut by a saw cutter, either into lengths of {{convert|3 or 6 or 12 or 24 |m|ft|sp=us}}, or it is coiled to {{convert|50 or 100 or 200|m|ft|0|abbr=on}} lengths on a coiler.

[[File:Hdpe pipe with blue strips.jpg|alt=water pipe with blue stripes|thumb|420x420px|HDPE Pipe with Blue stripes]]

A different die is used for striped HDPE pipe, which has small channels that the coloured material runs through, just before it is pushed through the die. This means the stripes are formed as an integral part of the pipe and are not likely to separate from the main pipe body. Co-extruded, or co-ex HDPE pipe, has a second extrusion screw which adds an extra skin of colour around the black HDPE pipe, this allows the pipe to be coloured on the outside, for identification or thermal cooling requirements.

After coming through the die the pipe is cooled by submerging in or spraying with water. The rate of cooling is carefully controlled to avoid deformation of the extruded pipe. Once cooled, a [[Laser engraving|laser]] or powder printer prints the size, type, date, and manufacturer's name on the side of the pipe. It is then cut by a saw cutter or coiled into longer lengths on a coiler.[[File:Hdpe pipe with blue strips.jpg|alt=water pipe with blue stripes|thumb|360x360px|HDPE pipe with blue stripes]]

== Uses ==

An example of the durability of HDPE pipe is the {{convert|600|m|ft|0|abbr=on}} long HDPE boom used for the [[Ocean Cleanup]] project. The HDPE pipeline is being released into the ocean to clean up the [[Great Pacific Garbage Patch]].<ref>{{cite web |title=AGRU and The Ocean Cleanup |url=https://www.agru.at/en/applications/agruline/agru-and-the-ocean-cleanup/ |website=www.agru.at|publisher=agru Kunststofftechnik Gesellschaft m.b.H. |accessdate=16 September 2019}}</ref>

==Longevity==

HDPE pipe has been used in rural and mining environments in Australia for over 50 years, proving to be a very durable and effective means of fluid and gas transfer.<ref>{{Cite web|url=http://www.pipa.com.au/wp-content/uploads/2018/09/tc4130.pdf|title=PIPA Technical Commentary on Polyethylene pipes for pressure applications }}</ref>{{Self-published inline|date=April 2019}}

HDPE piping is estimated to last 50 years. However, technical white papers written by the Plastics Industry Pipe Association assert that HDPE pipe systems can be reasonably expected to last up to, or over 100 years.<ref name="PIPA whitepaper">{{Cite web |date=2018 |title=Life Expectancy for Plastics Pipes |url=http://www.pipa.com.au/wp-content/uploads/2018/09/tn013.pdf |publisher=Plastics Industry Pipe Association of Australia Ltd |language=en}}</ref>

== Life expectancy ==

[[File:Hdpe Pipes In Coil.jpg|thumb|285x285px|HDPE yellow jacket gas pipe, white jacket communications conduit, and orange jacket electrical conduit]]

Although HDPE pipe is often estimated to last 50 years, they are in fact more likely to have life expectancies of 100 years. PIPA (Plastics Industry Pipe Association) and the Plastic Pipe Institute (PPI) have written technical white papers on HDPE design life. The PIPA paper is called "Life Expectancy for Plastics Pipes" which mentions that because of the fifty-year stress regression data, people {{who?|date=April 2019}} falsely assume that plastic pipe systems' life expectancy is only fifty years. In fact, these pipe systems can be reasonably expected to last up to or more than 100 years.<ref name="PIPA whitepaper" />{{Self-published inline|date=April 2019}} In Australia, PE pipes and PE fittings were introduced during the mid-1900s, mainly for irrigation or water supply, but also for gas, fuel, and other industrial applications. The use of this 50-year time interval, leads to a misunderstanding that it represents a 50-year pipe life. For pipe systems that have been correctly manufactured and installed, the actual life cannot be predicted, but can be expected to be over 100 years until major rehabilitation is needed.<ref name="PIPA whitepaper" />{{Self-published inline|date=April 2019}}

==References==