Type of flexible plastic pipe
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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 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,[1][self-published source?] 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.
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 s due to its durability, leak free joints, resistance to corrosion, and long-term cost-effectiveness."[2][self-published source?]
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.
HDPE communications conduit pipe being installed by directional drilling in Perth, Western Australia
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 trench-less installation safer and less intrusive on the surrounding environment.
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.[3] 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 HDD (horizontal directional drilling), sliplining, pipe bursting, floating and submerged pipe.[4]
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.[5][self-published source?]
Because food-grade polyethylene 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 plants or around corrosive or acidic environments, without needing to use protective coatings or galvanising, as is required on steel pipes. As HDPE has a very low thermal conductivity, it can maintain more uniform temperatures compared to metal pipes when carrying fluids, which will greatly reduce any need for insulation to control condensation around the pipeline.[6][self-published source?]
Manufacture
To make pipe lengths, HDPE resin is heated and extruded through a 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%.
The following shows the process for HDPE Pipe Extrusion:
Freshly Extruded 800 mm (31.50 in) 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 180 °C (356 °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 3 or 6 or 12 or 24 meters (9.8 or 19.7 or 39.4 or 78.7 ft), or it is coiled to 50 or 100 or 200 m (164 or 328 or 656 ft) lengths on a coiler.
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.
Uses
An example of the durability of HDPE pipe is the 600 m (1,969 ft) 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.[7]
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.[8][self-published source?]
Life expectancy
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?] 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.[5][self-published source?] In Australia, PE pipes and PE fittings were introduced during the mid-s, 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.[5][self-published source?]
Are you new to the HDPE piping world? No problem. Take a few minutes between projects to review the below collection of common HDPE pipe terminology and definitions. Once you have finished, please contact us for additional information and guidance or to discuss your company’s specific HDPE needs.
HDPE: High density polyethylene (HDPE) refers to the thermoplastic polymer produced from the monomer ethylene. HDPE piping has a high strength-to-density ratio and highly bendable, allowing for pipe to be coiled. HDPE is lightweight, flexible, inexpensive and corrosion resistant. In addition to piping, HDPE is used in the production of plastic bottles, geomembranes, grocery bags, toys, containers and plastic lumber.
IPS and DIPS: Iron Pipe Size or IPS represents the nominal diameter of the pipe. A 6-in. IPS pipe has an inside diameter of six inches. Ductile Iron Pipe Size or DIPS is used to specify the size of ductile iron pipe. Typically, IPS refers to black iron or carbon steel pipe while DIPS refers to cast/ductile iron pipe. IPS and DIPS are used in the HDPE market to replicate the familiar dimensions of these other IPS pipe is available in size ranging from ¾-in. to 65-in. diameters while DIPS is available from 4- in. to 36-in. diameters.
CTS: Copper Tube Size is specific to plumbing and potable water systems. In copper, the OD is always 1/8 inch larger that the nominal size of the pipe, and that has carried over to HPDE that is built to CTS sizes. As a replacement for traditional copper lines for water, a 2-in. HDPE pipe that follows CTS sizing standards would have an OD of 2 1/8 in. For water applications HDPE pipe can be sized as small as ¾ in OD.
Bend Radius: Bend radius, measured to the inside curvature, is the minimum radius one can bend a pipe, tube, sheet, cable or hose without kinking it, damaging it or shortening its life. The smaller the bend radius, the greater is the material flexibility. HDPE piping is more flexible than other competitive piping options, offering a smaller bend radius. However, exceeding minimum bend radiuses may result in mechanical failure and decreased longevity. And for HDPE-encased fiber-optic cabling, it is problematic, as exceeding minimum bend radius can cause light attenuation resulting in performance loss.
Dimension Ratio (DR): The Dimension Ratio (DR) is the ratio of the pipe outside diameter to the pipe minimum wall thickness. As diameters change, the pressure rating remains the same for the same material, dimension ratio and application.
Standard Dimension Ratio (SDR):
Certain Dimension Rations (DRs) that meet an ASTM International specified number series (32.5, 26, 21, 17, 13.5) are referred to as Standard Dimension Ratios (SDRs). There is approximately 25% difference in minimum wall thickness between each SDR.
Calculating SDR: SDR is defined as the ratio of the nominal outside diameter to the nominal wall thickness.
SDR = dn/en
Where dn is the nominal outside diameter of pipe and en is the nominal (minimum) wall thickness of the pipe.
Carbon Black (CB): Carbon Black products are additives used to improve the strength and performance of HDPE pipe. CBs are typically used to improve UV resistance and to reduce or lower moisture absorption in pipe
Coefficient of friction: Coefficient of friction measures the amount of friction existing between two surfaces. As this measurement relates to piping, a lower coefficient of friction typically means less friction damage in piping (example: outer layer wear). To find the coefficient of friction (fr) use this formula:
Fr/N = fr
Where Fr is the resistive friction force and N is the normal force pushing on objects.
Surge pressure - Recurring and occasional: American Water Works Association standard AWWA C901 defines two types of surge pressure, recurring and occasional. The safe peak pressure or allowed total pressure for HDPE pipe is 1.5 times the pipe’s pressure rating for recurring surge and 2.0 times the pipe’s pressure rating for occasional surge.
Temperature derating: Materials rated for operating pressures or tensions at a standard temperature, must be ‘derated’ when temperatures increase. Derating is usually expressed graphically or in terms of derating factors. HDPE piping loses its strength to pressure and tension as temperature is increased.
FM approved: FM Approvals is a third-party testing and certification service. FM Approved-HDPE pipe and fittings are subjected to more severe performance testing. The five-step certification process includes product review, testing, and manufacturing facility audits.
UL Rating: Underwriters Laboratories (UL) is a global safety science company and third-party certification company founded in . The company tests products and technologies for safety. Beginning in , UL published a series of standards for polymer raceway products, including rigid PVC conduit as well as HDPE conduit.
Seismic loading: Seismic loading is one of the basic concepts of earthquake engineering which includes application of a seismic oscillation to a structure. It happens at contact surfaces of a structure either with the ground or with adjacent structures.
According to an Electric Power Research Institute report Nondestructive Evaluation: Seismic Design Criteria for Polyethylene Pipe Replacement Code Case, there are two potential sources for seismic loads on the piping: loads from wave propagation in the soil and from seismic anchor motion of the buildings that form the boundary for the buried pipe.
Most of these definitions come from industry-recognized sources such as PPI. See below for a complete list of sources.
About United Poly Systems
United Poly Systems produces quality HDPE pipe in diameters from ¾-in. to 26-in. IPS, 4-in. to 24-in. DIPS, and ¾-in. to 2-in. CTS for use in many industries including telecommunications, power utility, water, electrical and oil and gas. The market for HDPE pipe continues to expand as initiatives to improve, repair and expand the country’s infrastructure are implemented.
Our off-the-shelf HDPE conduit/pipe is available in a variety of sizes, colors, dimensions and lengths, with or without stripes. We also offer fully customizable HDPE conduit options. In addition, piping can be customized with a ribbed interior (to maximize the distance cable may be pulled or jetted), pull tape, or a lubricated interior (for easier installation).
Success at UPS can be attributed to our vast experience, extensive client relationships, state-of-the-art manufacturing and quality processes. Our agile business model that allows UPS to quickly meet customers’ needs without the overhead expenses that are incurred by many of the larger producers in the industry.
Conveniently located in Springfield, Missouri and Albuquerque, New Mexico, United Poly Systems can provide quick delivery to a majority of the U.S. market.
HDPE piping is one of the things we do best here at US FUSION — but if you’re not working with it every day like we are, you may have some questions about what it is and how it works.
Below, we’ll explore the answers to some of those questions, giving you an overview of everything you need to know about HDPE piping: what it is, what it’s used for, and how it can benefit your application.
First things first — HDPE stands for high-density polyethylene, which is a type of thermoplastic made from petroleum. It’s flexible, but that definitely doesn’t mean it lacks in strength or performance. Among other things, HDPE is known for its outstanding water, chemical, and impact resistance — all qualities that come together to make it a top material choice for a number of applications, including heavy-duty piping.
HDPE piping is corrosion and abrasion-resistant, making it a great material for transporting various solids, liquids, and gases safely and effectively. You can find HDPE piping being used for many industrial applications, some of the most common being:
Municipal and industrial water and waste
Potable water
Wastewater and sewer
Drainage
Firewater
Oil and gas gathering systems
Methane recovery systems
Landfills
Water supply lines for oil recovery
The bottom line is, from firewater to hazardous waste, there is no system more effective at safely containing and transporting material than HDPE piping.
In recent years, HDPE piping has grown in popularity in various industries — and for good reason. Many have come to realize the countless benefits it brings, including:
Arguably the greatest benefit of HDPE piping is its exceptional durability. It offers water, temperature, and corrosion resistance — three things that other types of piping (galvanized steel, PVC, copper) just can’t do. Depending on how it’s applied, designed, and installed, HDPE piping can last an astounding 50-100 years.
Since HDPE piping is made of plastic, it’s much more lightweight than other types of piping. This means that it usually costs less to manufacture, transport, and install. It can also help save money and resources in regards to reduced installation time and labor.
One of the biggest issues you may face with other piping systems is leaks. However, HDPE’s installation and fusion process lends itself to unparalleled leak-free performance. The fusions create a monolithic connection and are even capable of handling the frequent surges common in water distribution and oil transportation.
On the off chance that your HDPE piping does have performance issues, due to aging or normal wear and tear, repairs are simple. Electrofusion couplers and off carriage butt welds can be performed in tight conditions to repair HDPE pipe. With trenchless techniques and technologies, HDPE pipe can be used to repair failing steel, concrete, and ductile iron pipelines. If it’s time to replace or upsize your existing piping system, whether it’s an HDPE system or not, HDPE piping makes it easier than ever.
For multiple reasons, HDPE piping is a fairly sustainable option. It takes less energy to manufacture than non-plastic pipes, requires fewer fittings due to its flexibility, and prevents hazardous toxins from escaping into the environment. It’s also capable of being recycled into non-pressure piping applications.
HDPE pipes can be installed through two techniques: trenching and trenchless. Trenching involves digging deep trenches, then installing the pipe. It’s messier than the trenchless technique, but it works more effectively for certain applications.
Trenchless installation, as the name suggests, doesn’t require digging any trenches before the pipes can be installed. It makes use of many different techniques to get the job done, such as directional drilling, sliplining, and pull-in-place lining.
If you’d like to learn more about how HDPE piping may suit your application, contact US FUSION. We’re one of the only companies in the industry equipped with over 35 years of experience in complete installation, supply, and on-site fusion. All of that experience combines to deliver you some of the most specialized HDPE piping systems on the market.
General
What does the PPI Power & Communications Division do?
PPI is the major North American manufacturers’ trade association of advocacy and education for plastics use in pipe, conduit and infrastructure solutions. The mission of the Plastics Pipe Institute is to advance the acceptance and use of plastic pipe systems through research, education, technical expertise and advocacy. PPI has divisions representing the different end use applications for pipe and conduit. The Power & Communications Division (PCD) mission is to expand knowledge of the uses and benefits of HDPE conduit for Power and Communications applications.
Where can I find terminology specific to duct and conduit?
PPI Handbook of PE Pipe - Chapter 14 on Duct & Conduit has a useful glossary: link
What is the voltage of mainline power distribution and can HDPE conduit handle that voltage?
HDPE conduits up to 8 inches in diameter have had solid dielectric, high voltage cables, rated at 345kV installed inside them. Further, conduit through 6 inches is commonly used to protect underground distribution cables having voltage ratings from 600V to 35kV. Cable voltage ratings have not been a deterrent for utilities choosing to use conduit made from HDPE for underground power cables.
Is all plastic pipe that is orange conduit?
No. While modern gas pipe is yellow, when excavating piping infrastructure workers should be aware that certain older plastic gas pipe material was colored orange or tan. The predominant color for conduit today is orange but many other colors do exist. See FAQ question What colors are available? The American Gas Association has published a historical list of plastic gas pipe manufacturers which includes colors where pertinent. Contact the local gas company for further information. See also:
Can HDPE conduit be used for natural gas, propane, compressed air or water service?
HDPE conduit is not suitable for pressure service, whether it be for a gas or for water. Gas service includes, but is not limited to, natural gas, propane or compressed air applications. Short-term pressurization of HDPE conduit for pull-tape or cable installation by blowing is acceptable. Water service includes, but is not limited to, potable water and non-potable water applications. Products suitable for these applications have specific technical requirements, undergo specific testing, and potentially require specific 3rd party certifications.
For more information, please visit 6 Inch HDPE Pipe.
Conduit Sizing
What size conduit do I need?
The size of the conduit you will need will depend on the type of cables to be installed, the method of cable installation, and method of conduit installation.
For further discussion on the sizing of conduit based on cable fill and cable installation method, see:
For further discussion on sizing of conduit based on conduit installation method, see:
Why are there many sizing systems for conduit?
There are a number of different sizing systems for conduit. These define the outside or inside diameter, wall thicknesses and tolerances. These include outside and inside diameter controlled sizes where the outside diameter, or inside diameter in the case of inside diameter controlled sizes, is fixed for a given size, and the wall thickness varies depending on the needs of the installation. Common sizes are IPS, SIDR, True Size, Schedule, EPEC and SDR. Selecting the right size of conduit is important so to ensure that the conduit is properly sized for the cable(s) to be installed and sufficiently robust for the installation and long term performance in the application. The PPI Power & Communications Division is working to harmonize the sizes across the ranges of standards. A more complete discussion of sizing systems is available within:
What do SDR and SIDR stand for?
SDR and SIDR values are indicators of wall thickness. SDR is the Standard Dimension Ratio, sometimes also referred to simply as DR (Dimension Ratio). Technically, it is the nominal outside diameter divided by the minimum wall thickness per specification. Similarly, SIDR is the ratio of the inside diameter of the conduit to the wall thickness of the conduit. The larger the SDR or SIDR, the thinner the wall thickness. The smaller the SDR or SIDR number the thicker the wall of the conduit.
Smaller SDR or SIDR numbers also mean that the conduit has higher tensile strength and greater resistance to deflection than a comparable product with a higher number. The combination of the outside diameter (OD) or inside diameter (ID) with the SDR or SIDR will define the ID of the conduit and the available space for the cables. See tables within conduit standards for available sizes and specific dimensions. A more complete discussion of sizing systems is available within:
Need help sizing the wall thickness for conduit in mini-HDD installations?
The Conduit Design Calculator is a software tool that aids in determining the most appropriate wall thickness of high-density polyethylene (HDPE) conduit installed via horizontal directional drilling (HDD) techniques.
How many power cables can be placed into a conduit?
It depends on the size and quantity of the cable. The NEC (National Electric Code) has guidelines on the number of conductors allowed in a HDPE Conduit. With one conductor, it can "fill" 53% of the inside diameter of the conduit. For 2 wires 31% and over 2 wires 40% fill ratio is allowed. Simply multiply the area of the conductors by the quantity and compare to the inside area of the conduit. For further discussion on the sizing of conduit based on cable fill and cable installation method, see:
What is the maximum number of HDPE conduit innerducts in a casing?
This is highly dependent on the installation. The straighter and shorter the run, the more you can fill the casing. The longer and more complex the casing installation is, the less fill is applicable. Generally, the recommended percentage fills for all combined innerducts being considered, based on areas, is:
For additional information on innerducts, please see:
Conduit Storage
How long can conduit be stored outdoors?
Black is recommended for any application where the conduit is exposed or stored over a long time period to sunlight (Carbon Black additive provides UV protection). Colors, even those with UV Stabilizers (other than black) cannot tolerate sunlight for extended periods of time without deterioration. ASTM F specifies the stabilizers in colored conduit should protect it in outside storage for a minimum of one year. Contact the manufacturer for recommendations for storage. For more information, see:
Can conduit stored outdoors for more than one year still be used?
In some cases, yes, depending on storage conditions and location. Conduit can be recertified to meet the required standards for use in some situations. Please contact your manufacturer to see if they offer this service for the product you have a question about.
Conduit Installation
How do I join HDPE conduit?
HDPE conduit can be joined using mechanical couplings, fusion joining (including electrofusion), and adhesive bonding. The choice may depend on the conduit installation method, cable installation method, and in-service conditions. For additional information, please see:
How do I avoid overstretching the conduit during installation?
HDPE conduit can be over-stressed during laying or pulling resulting in undesirable necking that may result in internal restriction that will later impede cable or innerduct pulling or blowing. For this reason, it is important to avoid over stressing the product during installation. The Safe Pull Strength is dependent on conduit dimensions, conduit temperature and conduit material. It is recommended to always use a breakaway link swivel, or similar, sized based on the Safe Pull Strength of the conduit being installed. PPI provides several references:
What do I do about HDPE Conduit Memory, Ovality and Coil-set?
Due to its flexible nature, HDPE conduit can become oval or out-of-round when it is wound onto reels or coils. Ovality is a packaging condition that occurs when conduit is coiled, whereby conduit flattens out as it is coiled. This is allowed and limits are specified in industry standards. Coil-Set is an inherent tendency for conduit to conform over time to the curved shape or bend radius of the coil or reel on which it has been stored. Both of these are sometimes termed “memory” as the conduit wants to hold its packaged shape; the conduit will have a memory from winding on the reel because the molecules align themselves during the manufacturing process of reeling, or "bending" the conduit. You can envision, one side of the conduit will be in tension, while the opposite is in compression. The molecules align themselves, relax and "remember" their position. Once uncoiled, they start to relax into the new positions. The rate of relaxation is temperature dependent, with relaxation occurring faster at higher temperatures.
For more information on ovality and coil-set, causes and methods for mitigations, see:
For additional information on working safely with conduit, please see:
What is the temperature range over which HDPE conduit can be installed?
HDPE conduit can be installed in ambient temperature ranging between -30 °F to 180 °F (-34 °C to 82 °C). At low temperature, care should be made in handling to avoid dropping the conduit. At high temperature, and particularly in conjunction with solar heating, HDPE conduit will have reduced Safe Pull Strength. Expansion/contraction of the conduit as a result of temperature changes should be considered in the design phase for above ground applications and, below ground, conduit should be allowed to stabilize with the ground prior to trimming and completing connections.
For additional information on thermal expansion/contraction, please see:
What is the impact of temperature on conduit length (thermal expansion/contraction)?
HDPE conduit has a high degree of thermal expansion/contraction, approximately 10 times that of metal pipe, with a coefficient of thermal expansion of 1 x 10-4 in/in/°F. As a “rule of thumb,” temperature change for unrestrained HDPE conduit is about “1/10/100,” that is, 1 inch for each 10 °F temperature change for each 100-foot of conduit. A temperature rise results in a length increase while a temperature drop results in a length decrease.
In aerial conduit applications due to the potential for significant temperature variations resulting from ambient fluctuations and solar heating, the effects of thermal expansion/contraction of the conduit must be carefully considered in the design process. In buried applications, temperature variations are significantly moderated in service; however, during installation, sufficient extra conduit should be laid to allow for thermal contraction that may occur once installed.
For additional information on thermal expansion/contraction, please see:
Product Offering
What colors are available?
The National Public Works Association recommends
Colors, even those with UV Stabilizers (other than black) cannot tolerate sunlight for extended periods of time without deterioration. ASTM F specifies the stabilizers in colored conduit should protect it in outside storage for one year. For more information, see:
Note: While modern gas pipe is yellow, when excavating existing piping infrastructure workers should be aware that certain older plastic gas pipe material was colored orange or tan. The American Gas Association has published a historical list of plastic gas pipe manufacturers which includes pipe colors where pertinent. Contact the local gas company for further information. See:
Can conduit be ordered with more than one conduit and/or color per reel?
Yes. Most manufacturers provide special packaging called paralleling or segmenting. Conduit that is parallel packaged can have up to four (4) different colors per reel. For more information, see:
What is the longest length that can be put on a reel?
That depends on the Outside Diameter of the conduit. The larger the conduit the less material will fit on a reel. See the PPI manufacturer's web sites for their standard reel configurations. For safety information related to handling of reels, see:
Can the conduit be supplied in coils without a reel?
Yes. This type of packaging is usually for quantities of less than 1,000 feet per coil. Coils are generally secured at multiple points to keep them together and palletized for shipping. For safety information related to handling of coils, see:
Can a pull tape be installed in the conduit at the factory?
Yes. Most manufacturers can install a wide range of pull tapes, from inexpensive polypropylene rope (PP Rope) to expensive Kevlar pull tapes that are pre-lubricated, measured and marked. The conduit is extruded over the pull line. The extruder has an opening in the back side of the extrusion die that forms the HDPE tube. The pull line is inserted into this opening at the same rate as the HDPE tube is extruded providing a continuous pull line inside the conduit. Depending on your project the manufacturer can suggest the pull line that is best for your application. See also:
Can cable be installed in the conduit at the factory?
Yes. This is called Cable in Conduit (CIC). Many types of cable, power or communications, can be installed in the conduit. ASTM D and UL are the specifications for CIC for power applications. The requirements for the conduit used in these products are essentially the same as regular conduit.
What advantage does ribbed or lubricated conduit have?
Ribbed or lubricated conduit reduces the friction between cable and conduit to facilitate cable installation. The friction between the cable outer jacket and the conduit inner surface can be a limiting factor for the distance of cable installed. Friction can lead to excess heat that can damage conduit, cable or both. Reducing this friction can significantly increase the achievable cable install distance. Longitudinal ribs reduce the surface area reducing friction (note that these are still basically a smoothwall product). Lubricants are commonly added to cable surface during installation but conduit with the inner surface pre-lubricated at the factory may be available. It is important to consider the compatibility of the lubricant with the cable jacket and the installation method (pull or blown) when choosing a lubricant. For more on reducing the friction and selection of lubricants, see:
Why can't we get 4-inch Schedule 40 on a reel?
Theoretically, 4-inch schedule 40 conduit can be placed on a reel. However, it is not recommended. As the conduit is extruded, it is wound on a reel. As it is wound, the top of the conduit is in tension, while the bottom is in compression. This causes the conduit to ovalize. It is much more apparent in the larger diameters. ASTM F acknowledges the effect and allows for it in the specification. As 4-inch Schedule 40 has a relatively thin wall, it (and Schedule 40 diameters above 4-inch) can have a tendency to buckle. That is why 4-inch Schedule 40 on a reel is not recommended. Those diameters are typically available in stick form. Heavier walls, such as SDR 13.5, can be put on reels. Six inch (6-inch) diameter conduit is typically the maximum diameter that is coilable. For more information on ovality and coil-set, causes and methods for mitigations, see:
Conduit Materials
What is HDPE?
HDPE is the abbreviation for High Density Polyethylene, the preferred and most commonly used material to make conduit. HDPE is a polymer comprised primarily of ethylene and is different from polyvinyl chloride (PVC), polyethylene terephthalate (PET) and polypropylene (PP) plastics. HDPE is strong, tough, durable, flexible in all weather, and never gets brittle. These characteristics make it the ideal choice for conduit products. You may already be familiar with HDPE as it is successfully used in milk jugs and other consumer packaging products. In the case of conduit, a very specific durable grade of HDPE is selected to ensure appropriate long term performance in the application. For more information:
What does the cell classification of HDPE mean?
The cell classification is a method of identifying and specifying the raw material properties of HDPE Conduit. It is a series of six numbers and one letter which describe the properties of the resin per ASTM D. The numbers, in order, represent the density, melt index, flexural modulus, tensile strength, slow crack growth, hydrostatic design basis, and the letter represents whether the material is black or colored. It is used in the industry standards to specify the minimum properties of acceptable materials to be used in the fabrication of conduit. As the cell classification is specified within these standards, it is typically not required to specify the cell classification of the material if you are already specifying conduit that conforms to any of the ASTM, NEMA, UL or CSA conduit standards. For more information:
What is black or colored “masterbatch” concentrate?
In the manufacturing process for conduit, called extrusion, unpigmented polyethylene pellets are mixed with a small proportion of black or colored pellets. These black or colored pellets are also made of polyethylene but have had a high concentration of carbon black or colored pigments, and sometimes other additives, incorporated. These pellets are termed a “concentrate” or “masterbatch”. The extrusion process is specifically designed to melt and mix all the unpigmented and masterbatch pellets together distributing the black or color evenly throughout the entire material. Carbon black, color pigments and other additives are specifically selected to enhance the properties of the final product, such as outdoor weathering resistance.
Can I use conduit made with PE material?
The standard HDPE resin used in the manufacture of conduit, and as specified in conduit standards, provides the ideal combination of strength and flexibility for most applications. Occasionally, a higher strength conduit may be desirable due to high anticipated installation or frictional forces, e.g., long difficult HDD run; in such cases, a heavier wall conduit may be selected or, alternatively, a higher strength material may be selected, such as a PE pressure pipe grade with approximately 15% greater tensile strength. The PE product will likely be stiffer and more expensive than standard industry conduit. Not all manufacturer’s supply PE based conduit and UL or CSA certified products may not be available. PE based pressure pipe may not conform to the conduit standards unless all specified conduit tests have been conducted and the printline includes the conduit standard reference.
PPI has a number of resources explaining the materials used in conduit, how to estimate the safe pulling strength of conduit and calculating the appropriate wall thickness for your installation:
What is rework vs. recycle HDPE?
The use of rework, sometimes called regrind, HDPE is permitted in most conduit standards (e.g. ASTM, UL, NEMA, CSA). As defined by ASTM F412, rework is "plastic from a manufacturer’s own production that has been reground or pelletized for reuse by that same manufacturer." There are various sources of rework from the manufacturing process. In all cases rework is made from materials that are under the control of the conduit manufacturer and they are fully aware of the material composition of the rework. Typically, rework is used in combination with virgin resin anywhere from a 10 - 40% ratio. The use of rework eliminates waste in the production process, avoiding material going to landfill unnecessarily, thus reducing the carbon footprint of the product.
Recycled HDPE are HDPE materials sourced from outside a manufacturer’s plant. This can be post-consumer, post-commercial or post-industrial material. The PPI Power & Communications division is developing requirements to ensure conduit made with recycled HDPE has the required durable, long-term performance needed for the application.
Codes, Standards & Certification
What standards exist for Conduit and where can I find them?
A number of standards bodies develop standards for conduit. Different standards may be intended for different end-uses and applications. Always read the scope of the standard to learn about its intended end-use. Standards are issued by:
PPI provides several publications that may be helpful:
What does ASTM stand for?
ASTM was the American Society for Testing and Materials but has been renamed ASTM International to communicate the international scope and acceptance of its standards. It is an association of manufacturers, engineers, consultants and governmental officials who write standards for materials and products used in all types of construction, including conduit. ASTM Standards for conduit are ASTM F and D.
ASTM F vs. D, D or D?
ASTM F and D are ASTM standards specifically written for conduit products. ASTM D, ASTM D, ASTM F714 and ASTM D are ASTM water pipe specifications often referred to in conduit specifications. Dimensionally pipes conforming to ASTM F and the various water pipe ASTM standards are the same, but the material specification for water pipes include pressure strength requirements and may not have been tested to all the standard conduit requirements. Using water pipe ASTM standards for conduit applications can raise the price significantly because pressure rated resin is more expensive than conduit non-pressure rated resins.
What is UL or CSA Certification?
UL or CSA certified products are products that have been certified by a third party, in this case Underwriters Laboratories or Canadian Standards Association, to conform to a standard. Typically, it requires the manufacturer’s production facilities to be audited on a regular basis by the certifying agency and that samples from those facilities are tested periodically by the certifying agency to ensure conformance with the specified standards. UL or CSA certification may be required by certain customers or by code requirements in the power industry. In many applications third-party certification is not required as it adds cost. Not all products may be available with third party certification so check with the conduit manufacturer. Note that ASTM and NEMA do not provide certification services: In most cases, conduit manufacturers will attest to the fact that their products conform to one or more industry standards.
What is the difference between UL certified resin and ASTM F resin?
Not much in reality. Resins can have either or both classifications. Both are quality resins and meet the same requirements; however, UL will independently test and certify the resin. A manufacturer is required to use a UL certified resin for UL certified product. Blending or mixing is not allowed by UL standards.
Why can't I get SDR 11, UL listed conduit?
You may now be able to get SDR 11 conduit certified to UL651A or UL. SDR 11 wall thickness was not allowed within the previous UL standard but was added in 6th edition published in . UL 651A, Continuous Length HDPE Conduit, and UL , Nonmetallic Underground Conduit with Conductors, now has six categories of conduit wall thickness: EPEC-A, EPEC-13.5, EPEC-11, EPEC-9 as well as Schedule 40 and Schedule 80. ASTM D, ASTM D and NEMA TC7 also include SDR11 conduit.
When HDPE conduit is used in directional drilling, a heavier walled conduit may be required. Relevant PPI publications to assist in selecting wall thickness where the pulling forces may be of concern include:
What are the NEC requirements for HDPE Conduit?
The US National Electric Code (NFPA 70) is the code regulating HDPE conduit use in power applications. Section 353 ( edition) specifies that conduit and fittings shall be listed and indicates conditions under which it can be used. Generally, conduit must be buried or encased and cannot be used in applications with an ambient temperature greater than 50 °C (122 °F). The cable fill limits are defined. Conductors or cables rated at a temperature higher than
The listed temperature rating of HDPE conduit are permitted to be installed in HDPE conduit, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the HDPE conduit. For more information see:
Can 90C and 105C rated cables be used with HDPE Conduit?
Yes, the NEC (NFPA 70) permits the use of 90C and 105C rated conduit under specific conditions, provided the conductors or cables are not operated at a temperature higher than the listed temperature rating of the HDPE conduit. For more information see:
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