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Plastic pipe is a tubular section, or hollow cylinder, made of
plastic Plastics are a wide range of synthetic or semi-synthetic materials that use polymers as a main ingredient. Their plasticity makes it possible for plastics to be moulded, extruded or pressed into solid objects of various shapes. This adaptab ...
. 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 Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circula ...
are far stiffer per unit weight than solid members. Plastic pipework is used for the conveyance of
drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
,
waste water Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...
,
chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...
s, heating fluid and cooling fluids,
foodstuff Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...
s, ultra-pure liquids,
slurries A slurry is a mixture of denser solids suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids or separating minerals, the liquid being a carrier that is pumped on a device such as a centrifugal pu ...
,
gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
es,
compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
,
irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow Crop, crops, Landscape plant, landscape plants, and Lawn, lawns. Irrigation has been a key aspect of agriculture for over 5,00 ...
,
plastic pressure pipe systems 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 sm ...
, and
vacuum system application 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 sm ...
s.


Types

There are three basic types of plastic pipes:


Solid wall pipe

Extruded Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
pipes consisting of one layer of a homogeneous matrix of thermoplastic material which is ready for use in a pipeline.


Structured wall pipe

Structured-wall pipes and fittings are products which have an optimized design with regard to material usage to achieve the physical, mechanical and performance requirements. Structured Wall Pipes are tailor made solutions of piping systems, for a variety of applications and in most cases developed in cooperation with users.


Barrier pipe

Pipe incorporating a flexible metallic layer as the middle of three bonded layers. Barrier pipe is used, for example, to provide additional protection for the contents passing through the pipe (particularly drinking water) from aggressive chemicals or other pollution when laid in ground contaminated by previous use. Most plastic pipe systems are made from thermoplastic materials. The production method involves melting the material, shaping and then cooling. Pipes are normally produced by
extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
.


Standards

Plastic pipe systems fulfil a variety of service requirements. Product standards for plastics pipe systems are prepared within the CEN/TC155 standards committee. These requirements are described in a set of European Product Standards for each application alongside their specific characteristics, for example: * Conveyance of
drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...
: Hygienic requirements * Conveyance of gas: Highest Safety requirements *Plastic pipes for radiant heating and floor heating: Temperature resistance over decades * Sewer applications: High
chemical resistance The chemical resistance of a material or surface can be determined in compliance with ISO 2812 Paints and varnishes – Determination of resistance to liquids – Part 1: Immersion in liquids other than water (ISO 2812-1:2007); German Version EN I ...
Plastic pipes are capable of fulfilling the specific requirement for each application. They do so over a long lifetime and with reliability and safety. The key success factor is achieved by maintaining consistently high quality levels. For plastic pipe products, these levels are defined by the different standards. Two aspects are fundamentally important for the performance of plastic pipes: flexibility and long lifetime.


Materials used

* ABS (
Acrylonitrile Butadiene Styrene Acrylonitrile butadiene styrene (ABS) (chemical formula (C8H8)''x''·(C4H6)''y''·(C3H3N)''z'' is a common thermoplastic polymer. Its glass transition temperature is approximately . ABS is amorphous and therefore has no true melting point. A ...
) * CPVC (
Chlorinated Polyvinyl Chloride Chlorinated polyvinyl chloride (CPVC) is a thermoplastic produced by chlorination of polyvinyl chloride (PVC) resin. CPVC is significantly more flexible than PVC, and can also withstand higher temperatures. Uses include hot and cold water deli ...
) * HDPE ( High-Density Polyethylene)) * PB-1 (
polybutylene 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. Production Polybutylene is produced by polymerisatio ...
) * PE (
polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
) of various densities, also abbreviated to
LDPE Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its ...
,
MDPE Medium-density polyethylene (MDPE) is a type of polyethylene defined by a density range of 0.926–0.940 g/cm3. It is less dense than HDPE, which is more common. MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or met ...
and
HDPE 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, ...
(low, medium and high density polyethylene; the medium density version is at times referred to as "black alkathene" in the UK) * PE-RT (polyethylene of Raised Temperature (RT)) * PEX (
cross-linked polyethylene 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, ins ...
) * PP (
polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and ...
) * PVDF (
Polyvinylidene Difluoride Polyvinylidene fluoride or polyvinylidene difluoride (PVDF) is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of 1,1-Difluoroethylene, vinylidene difluoride. PVDF is a specialty plastic used in applications requ ...
) * UPVC ( Unplasticized Polyvinyl Chloride)


Material characteristics


ABS (Acrylonitrile Butadiene Styrene)

Acrylonitrile Butadiene Styrene (ABS) is used for the conveyance of potable water, slurries and chemicals. Most commonly used for DWV (drain-waste-vent) applications. It has a wide temperature range, from -40 °C to +60 °C. ABS is a
thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...
material and was originally developed in the early 1950s for use in
oil field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter) is created in surrounding rock by the presence ...
s and the chemical industry. The variability of the material and its relative cost effectiveness has made it a popular engineering plastic. It can be tailored to a range of applications by modifying the ratio of the individual chemical components. They are used mainly in industrial applications where high
impact strength In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
and waste.


CPVC (Chlorinated Polyvinyl Chloride)

Chlorinated Polyvinyl Chloride (CPVC) is resistant to many acids, bases, salts, paraffinic hydrocarbons, halogens and alcohols. It is not resistant to solvents, aromatics and some chlorinated hydrocarbons. It can carry higher temperature liquids than uPVC with a max operating temperature reaching . Due to its greater temperature threshold and chemical resistance, CPVC is one of the main recommended material choices in residential, commercial, and industrial water and liquid transport.


HDPE (High-Density Polyethylene)

High-Density Polyethylene (HDPE) - HDPE pipe is strong, flexible and light weight. It has a zero leak rate when fused together.


PB-1 (polybutylene)

PB-1 is used in pressure piping systems for hot and cold potable water, pre-insulated district heating networks, and surface heating and cooling systems. Key properties are weldability, temperature resistance, flexibility and high hydrostatic pressure resistance. One standard type, PB 125, has a minimum required strength (MRS) of 12.5 MPa. It also has low noise transmission, low linear thermal expansion, no corrosion and calcification. PB-1 piping systems are no longer sold in North America. Market share in Europe and Asia is small but steadily growing. In some markets, e.g. Kuwait, UK, Korea and Spain, PB-1 has a strong position.


PE (polyethylene)

Polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...
has been successfully used for the safe conveyance of potable and waste water, hazardous waste, and compressed gases for many years. Two variants are
HDPE Pipe HDPE pipe is a type of flexible plastic pipe used for fluid and 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 ...
(
high-density polyethylene 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, ...
) and the more heat resistant
PEX PEX is cross-linked polyethylene, a form of polyethylene with cross-links. PEX or Pex may also refer to: Science and technology *Peer exchange, a method to gather peers for BitTorrent * PHIGS Extension to X, in programming * Pex (software), a un ...
(cross-linked polyethylene, also XLPE). PE has been used for pipes since the early 1950s. PE pipes are made by
extrusion Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
in a variety of sizes dimensions. PE is lightweight, flexible and easy to weld. Its smooth interior finish ensures good flow characteristics. Continuous development of the material has enhanced its performance, leading to rapidly increasing usage by major water and gas utility companies throughout the world. The pipes are also used in lining and trench-less technologies, the so-called no-dig applications where the pipes are installed without digging trenches without any disruption above ground. Here the pipes may be used to line old pipe systems to reduce leakage and improve water quality. These solutions are therefore helping engineers to rehabilitate antiquated pipe systems. Excavation is minimal and the process is carried out quickly below ground. Also for PE pipe material, several studies demonstrated the long track record with expected lifetime of more than 50 years.
Cross-linked polyethylene 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, ins ...
is commonly referred to as XLPE or PEX. It is a thermoplastic material that can be made in three different ways depending how the cross-linking of the polymer chains is being made. PEX was developed in the 1950s. It has been used for pipes in Europe since the early 1970s and has been gaining rapid popularity over the last few decades. Often supplied in coils, it is flexible and can therefore be led around structures without fittings. Its strength at temperatures ranging from below freezing up to almost boiling makes it an ideal pipe material for hot and cold water installations, radiator and under floor heating, de-icing and ceiling cooling applications


PE-RT

Polyethylene of Raised Temperature (RT) or PE-RT expands the traditional properties of polyethylene. Enhanced strength at high temperatures are thus made possible through special molecular design and manufacturing process control. Its resistance to low or high temperatures makes PE-RT ideal for a broad range of hot and cold water pipe applications.


PP (polypropylene)

Polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins and ...
is suitable for use with foodstuffs, potable and ultra pure waters, as well as within the pharmaceutical and chemical industries. PP is a thermoplastic polymer made from polypropylene. It was first invented in the 1950s and has been used for pipes since the 1970s. Due to the high impact resistance combined with good stiffness and high chemical resistance makes this material suitable for sewer applications. A good performance at operating temperature range from up to (continuous) makes this material suitable for in-house discharge systems for soil & waste. A special PP grade with high temperature behaviour up to (short-term) makes that material a good choice for in-house warm water supply.


PVDF (Polyvinylidene Difluoride)

Polyvinylidene Difluoride (PVDF) is a fairly non-reactive,
thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...
fluoropolymer A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon ...
with excellent chemical and thermal resistance for plastic pipework uses. PVDF resin is produced through polymerization of the vinylidene fluoride monomer. The PVDF resin is then used to make PVDF pipe as well as many other products. Industries and applications select PVDF pipe due to its inert, durable qualities. PVDF piping is used most in the chemical process industry due to its ability to plumb aggressive, corrosive solutions. PVDF pipe also sees common use in high purity applications, semi-conductor fabrication, electronics / electricity, pharmaceutical developments, and nuclear waste processing. PVDF piping specifications and performance characteristics approve PVDF pipe up to under pressurized system conditions. The pipe does not support fungus growth according to military test standard method 508, 81-0B. Dissimilar from other common thermoplastic pipes, (uPVC, CPVC, PE, PP), PVDF does not exhibit sensitivity to UV light or ozone oxidative damage, approving it for long term outdoor uses.


uPVC (unplasticized Polyvinyl Chloride)

uPVC or PVC-U, is a thermoplastic material derived from common salt and fossil fuels. The pipe material has the longest track record of all plastic materials. The first uPVC pipes were made in the 1930s. Beginning in the 1950s, uPVC pipes were used to replace corroded metal pipes and thus bring fresh drinking water to a growing rural and later urban population. uPVC pipes are certified safe for drinking water per NSF Standard 61 and used extensively for water distribution and transmission pipelines throughout North America and around the world. uPVC is allowed for waste lines in homes and is the most often used pipe for sanitary sewers. Further pressure and non-pressure applications in the field of sewers, soil and waste, gas (low pressure) and cable protection soon followed. The material's contribution to public health, hygiene and well-being has therefore been significant. Polyvinyl chloride or uPVC (unplasticized polyvinyl chloride) pipes are not well suited for hot water lines and have been restricted from inside water supply line use in the USA for homes since 2006. Code IRC P2904.5 uPVC Not listed. uPVC has high chemical resistance across its
operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...
range, with a broad band of operating pressures. Max operating temperature is reported at , and max working pressure: . Due to its long-term strength characteristics, high stiffness and cost effectiveness, uPVC systems account for a large proportion of plastic piping installations and some estimations put it that greater than of uPVC pipe are currently in service across applications.


uPVC Variants

Based on the standard polyvinyl chloride material, three other variants are in use. One variant called OPVC, or PVCO, represents an important landmark in the history of plastic pipe technology. This molecular-oriented bi-axial high performance version combines higher strength with extra impact resistance. A ductile variant is the MPVC, polyvinyl chloride modified with acrylics or chlorinated PE. This more ductile material with high fracture resistance is used in higher-demand applications where resistance against cracking and stress corrosion is important. In several studies the long track record of uPVC pipes has been investigated. Recent investigations at the German KRV and the Dutch TNO have confirmed that uPVC water pressure pipes, when installed correctly have a useful life span of over 100 years.


Characteristics


Longevity of plastic piping systems

Plastic pipes have been used in service for over 50 years. The predicted lifetime of plastic piping systems exceeds 100 years. Several industry studies have demonstrated this prognosis. Plastic pipe materials have always been classified on the basis of long-term pressure testing. The measured failure times as a function of the stresses in the pipe wall has been demonstrated in so-called Regression Curves. An
extrapolation In mathematics, extrapolation is a type of estimation, beyond the original observation range, of the value of a variable on the basis of its relationship with another variable. It is similar to interpolation, which produces estimates between know ...
based on measured failure times has been calculated to reach 50 years. The predicted failure stress at 50 years was taken as a basis for the classification. This value is called MRS, Minimum Required Stress, at 50 years.


Pipe system failure

Some reasons why plastic piping systems may fail are poor product bonding/gluing during installation and naturally-occurring physical damage, such as from tree root infiltration.


Flexibility

Plastic Pipes are classified by their ring stiffness. The preferred stiffness classes as described in several product standards are: SN2, SN4, SN8 and SN16, where SN is Nominal Stiffness (kN/m2). Stiffness of pipes is important if they are to withstand external loadings during installation. The higher the figure, the stiffer the pipe. After correct installation, pipe deflection remains limited but it will continue to some extent for a while. In relation to the soil in which it is embedded, the plastic pipe behaves in a 'flexible' way. This means that further deflection in time depends on the settlement of the soil around the pipe. Basically, the pipe follows the soil movement or settlement of the backfill, as technicians call it. This means that good installation of pipes will result in good soil settlement. Further deflection will remain limited. For flexible pipes, the soil loading is distributed and supported by the surrounding soil. Stresses and strains caused by the deflection of the pipe will occur within the pipe wall. However, the induced stresses will never exceed the allowed limit values. The thermoplastic behavior of the pipe material is such that the induced stresses are relaxing to a low level. It has to be noted that induced strains are far below the allowable levels. This flexible behaviour means that the pipe will not fail. It will exhibit only more deflection while keeping its function without breaking. However, rigid pipes by their very nature are not flexible and will not follow ground movements. They will bear all the ground loadings, whatever the soil settlement. This means that when a rigid pipe is subject to excessive loading, it will reach the limit for stress values more quickly and break. It can therefore be concluded that the flexibility of plastic pipes offers an extra dimension of safety. Buried Pipes need flexibility.


Components of plastic pressure pipe systems

Pipes, fittings,
valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
s, and accessories make up a plastic pressure pipe system. The range of pipe diameters for each pipe system does vary. However, the size ranges from and . Pipes are extruded and are generally available in: , , , and straight lengths and , , , and coils for LDPE and HDPE. Pipe fittings are moulded and come in many sizes: tee 90° equal (straight and reducing), tee 45°, cross equal, elbow 90° (straight and reducing), elbow 45°, short radius bend 90° socket/coupler (straight and reducing), union, end caps, reducing bush, and stub, full face, and blanking flanges. Valves are moulded and also come in many types:
ball valve A ball valve is a flow control device which uses a hollow, perforated and pivoting ball to control fluid flowing through it. It is open when the ball's hole is in line with the flow inlet and closed when it is pivoted 90-degrees by the valve ...
s (also multiport valve),
butterfly valve A butterfly valve is a valve that isolates or regulates the flow of a fluid. The closing mechanism is a disk that rotates. Principle of operation Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves ...
s, spring-, ball-, and swing-check non-return valves,
diaphragm valve Diaphragm valves (or membrane valves) consists of a valve body with two or more ports, an elastomeric diaphragm, and a "weir or saddle" or seat upon which the diaphragm closes the valve. The valve body may be constructed from plastic, metal, woo ...
s, knife gate valve,
globe valve A globe valve, different from ball valve, is a type of valve used for regulating Fluid dynamics, flow in a Piping, pipeline, consisting of a movable plug or disc element and a stationary ring seat in a generally spherical body. Globe valves are ...
s and pressure relief/reduction valves. Accessories are solvents, cleaners, glues, clips, backing rings, and gaskets.


See also

*
HDPE Pipe HDPE pipe is a type of flexible plastic pipe used for fluid and 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 ...
*
Pipe support A pipe support or pipe hanger is a designed element that transfer the load from a pipe to the supporting structures. The load includes the weight of the pipe proper, the content that the pipe carries, all the pipe fittings attached to pipe, and t ...
*
Piping Within industry, piping is a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping design studies the efficient transport of fluid. Industrial process piping (and accompan ...
*
Reinforced thermoplastic pipe Reinforced thermoplastic pipe (RTP) is a type of pipe reinforced using a high strength synthetic fibre such as glass, aramid or carbon. It was initially developed in the early 1990s by Wavin Repox, Akzo Nobel and by Tubes d'Aquitaine from France, w ...


References


External links

* * * *{{cite book , author=David A. Chasis , title=Plastic Piping Systems , publisher=Industrial Press , year=1988 , isbn=0-8311-1181-X , url-access=registration , url=https://archive.org/details/plasticpipingsys0000chas
ISO Technical Committee TC 138 - Plastics pipes, fittings and valves for the transport of fluidsPlastics Pipes and Fittings Association (PPFA)The European Plastic Pipes and Fittings Association (TEPPFA)
Piping Plumbing Pipe manufacture