What fittings are available for HDPE pipe?
HDPE fittings in standard configurations, including straight and reducing tees, elbows, crosses, Concentric and eccentric reducers, flanges, mechanical-joint adaptors, outlet branch-saddles, etc. These can be fused directly to the HDPE pipe. Custom fittings are also available upon request.
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In what lengths is HDPE pipe available?
It is available either in coils or straight lengths. Coils are normally available for small diameter pipe ( 6 inch and smaller). For diameters 3 inch and larger pipe is normally available in straight lengths up to 50' in length.
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Is the pipe available in both ductile iron pipe size and iron pipe size outside diameters?
A. Yes, HDPE pipe is available both in iron pipe (lPS) and ductile i on pipe sizes (DIPS), Sometimes also known as cast-iron pipe sizes (CIPS). Ductile iron pipe sizes are available in 3 Inch to 54-inch diameters. Iron pipe sizes are available from 3/4 inch to 63-inch diameters.
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How long has HDPE been used in sewer and water applications?
Polyethylene has been used for sewer force mains, gravity flow sewers, and pressure water Main applications for approximately 50 years. After many years of field proven performance, it became a standardized material and product. The first American Water Works Association (AWWA) Standard for HDPE Pipe, C901, HDPE Pipe and Tubing inch through 3 inch was adopted in 1978. AWWA Standard for larger pipe, C906, HDPE Pipe and Fittings, 4 inch through 63 inch, was adopted in 1990.
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What is the life expectancy of HDPE pipe?
The US EPA expects 1O0-year service life from HDPE land fill liners. Buried solid wall or profile wall HDPE pipe should last at least as long .HDPE pressure pipe was first used in water service over 50 years ago. Current accelerated testing methods predict that today's HDPE pressure pipes will last much longer than 50 years. Everything points to a service life of at least 100 years in a properly designed and installed HDPE pipe system.
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Is polyethylene pipe affected by chemicals?
Plastics are not subject to galvanic corrosion, as are metals, since they are not conductors. However, plastics can be affected through direct chemical attacks, strain corrosion, or solvation. The extent of the resistance is a function of many items, including time, temperature, and stress of contact. For more information you can consult PPI Technical Report TR19[38], Thermoplastic Piping for the Transport of Chemicals.
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ls HDPE able to handle ozone?
Yes, HDPE pipe has a limited resistance and consequently a limited service life when conveying ozone at up to 120 degrees Fahrenheit. Over time the pipe will become brittle. The phenomenon occurs faster for thin wall pipes, and slower for thick wall pipes.
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Will sunlight adversely affect HDPE pipe?
lf the proper amount of ultraviolet stabilizer has been added to the colored pipe resin, non-black pipe can last several years in outdoor storage. Non-black pipe is not recommended for permanent outdoor use. Black PE pipe has been stabilized with carbon black, which is the most effective ultraviolet stabilizer, PE pipe with carbon black UV stabilization (the normal black PE pipe), may be used indefinitely outdoors.
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Will HDPE pipe float in water?
Yes, HDPE pipe has a specific gravity of about 0 .95 so it will float. For underwater, anchored pipeline installations it, is important to specify the proper weights and spacing of the weights. Screw-anchors are a practical alternative. Whenever possible, an underwater pipeline should be installed in a trench with protective crushed rock cover.
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What is the temperature range across which HDPE pipe rnay be used?
The upper limit temperature for pressure service is 140 degrees Fahrenheit . ln structural pipe, gravity flow application in stable oils; the upper thermal limit is considered to be in the range of 160F for long term exposure; and up to 180 degrees Fahrenheit for short-term intermittent exposure. The low temperature limit is usually regarded as minus 130 degrees Fahrenheit (seen next question). Cold temperatures do not adversely affect HDPE in static applications.
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Does HDPE pipe withstand ice plugs?
Water with in the pipe may freeze solid without damaging the pipe. However, ice blockages must be thawed before pumping is resumed. Care should be taken to limit the additional tresses imposed on a 'frozen' PE pipe since the pipe wall may already be in a state of stress if the contents were unable to expand longitudinally during the freezing process. Seasonal freeze / thaw conditions have little effect on this flexible, elastic piping system.
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Will HDPE pipe wear less than other materials in a slurry application?
Yes, in general terms, with adequate particulate suspension, HDPE pipe has an extremely high resistance to abrasion from slurries. In some applications, HDPE pipe has outlasted steel pipe by as much as 4 to 1 for a given situation.
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Can HDPE pipe be used in permanent above ground installations?
Yes, in many mining and industrial applications, HDPE pipe has been installed above ground and has provided and continues to provide excellent service after1 5 to 25 years( North America), with the potential to remain in service for many more years.
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How are HDPE solid wall pipe and components joined and connected?
HDPE pipe is normally joined by heat fusion. Butt fusion, socket fusion, side wall fusion and electro fusion are all heat fusion methods that create a leak free joint stronger than the pipe itself. The butt fusion procedure is most frequently used joining procedure. In this process the pipe's mating ends are aligned and heated with standard tools until the surfaces have become molten. When held together under moderate pressure, the melted faces flow together forming a monolithic, homogeneous joint as the material cools.
Generic Butt fusion and Saddle heat fusion procedures and guide lines may be downloaded from PPI's website.
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How long does it take to make a butt fusion joint?
The time required to make a butt fusion joint is dependent upon the pipe wall thickness and diameter, and the field weather conditions. Typically the thicker the pipe being joined the longer it takes to make a butt fusion joint, due to heating and cooling time requirements. A typical time to make a butt fusion joint on a 12" DR26 pipe ( including all preparation time but excluding the cooling time ) is 10 minutes once the fusion machine was set up.
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What inspection criteria are used to provide assurance about the quality of heat-fusion joints?
The fusion joint has to be made following the pipe manufacturer's recommended fusion procedures, which include the procedures described in PPI's TR-4. The time-proven method used for field inspection of fusion joints is visual examination of the melt bead. Some fusion equipment manufacturers provide a data-logging unit to record critical fusion parameters. (PPl: TR33 & TR41)
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Can the butt fusion bead be removed from HDPE?
Yes, both external and internal bead removal tools are available. Removal of the bead does not affect the strength of the fused joint when removed after the bead cools to ambient temperature.
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Are gaskets required between the faces of HDPE flange adapters?
Gaskets are not required between HDPE to HDPE connections. Elastomeric gaskets are normally used for flanges between HDPE flange adapters and metal flanges.
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Will mechanical joint valves and fittings work with HDPE pipe?
Yes. Mechanical joint adapters fused to HDPE pipe are available as standard products. These joints are fully restrained.
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What is the recommended practice for joining HDPE pipe to mechanical joint valves and fittings?
MJ adaptors or Flange adaptors can be welded to PE pipe. These are then bolted to the other pipe using standard MJ assemblies or flange assemblies. MJ adaptor joints and flanges joints are fully restrained just like fusion-welded joints, so no thrust restraints required. However if the joints in the matching pipe are not fully restrained (bell and gasket), thrust restraint measures are required at the transition.
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How can HDPE pipe be connected to pipe made from other materials (PVC, Ductile, lron, Corrugated)?
For non-pressure drainage applications, flexible rubber couplings have been used for decades with success. These flexible couplings are made for joining all types of gravity flow drainage pipe, including transitions from one type or size of pipe to another.
For pressure applications and low-pressure sewer applications, HDPE transition fittings, HDPE mechanical-joint adapters, Gasket-joint adaptors, HDPE flanges, and standard metal couplings with internal stiffeners are recommended.
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Why is it necessary to consider the working pressure rating (WPR) of a plastic piping system, instead of just considering the pressure class (PC) of the pipe?
Actually, you should make this evaluation regardless of the pipe material being considered. Steady state pressure (no flow or constant velocity) within a pipe induces a stress in the pipe wall. The measure of a pipes ability to be pressurized is its' pressure class. However changes in flow velocities introduce additional stresses in the pipe wall. The physical characteristics of a pipe material play a significant role in determining the magnitude and frequency of this induced surge or water hammer stress. Pipe made of stiffer materials experience much higher surge stress levels and more frequent stress changes, while often having ales ability to tolerate surge and fatigues' tresses.
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Why is there a difference in pressure class (PC) and working pressure rating (WPR) between HDPE pipe and PVC pipe?
PVC is more than three times as stiff as PE. The magnitude of a pressure wave caused by the same hydraulic event is about 50% higher in a PVC pipe. And the pipe has a lower built in tolerance to surge stresses. So it is desirable to determine the remaining steady state pressure capacity of a pipe (its' working pressure rating) once the hydraulic operating conditions are known. Usually a PC100PE pipe (DR1 7) will have the same WPR as a PC150PVC pipe (DR18)
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Is there a loss of head pressure in HDPE pipe due to the inner bead resulting from the butt fusion process?
No. For pressure applications the Hazen-Williams C-factor of 150 already accounts for losses caused by the inner weld bead. Field tests confirm that the 150 C-factor used in the Hazen- Williams equation properly models the actual flow and that the bead is of no hydraulic significance.
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Will HDPE pipe of the same OD size as Dl pipe deliver the same flow?
The inside surface of HDPE is extremely smooth and has a very low long-term design coefficient of friction. The roughness co-efficient to use with Ductile iron pipe recognizes the likelihood that the ID roughness will degrade over time. The smooth bore of HDPE pipe is maintained throughout its service life. It is often possible to use a polyethylene pipe with a smaller inside diameter than the comparably sized ductile iron pipe, and still achieve an equal or greater flow.
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Are bedding and backfill procedures different for HDPE pipe than for PVG pipe?
No. HDPE and PVC pipe lines are installed using the same standard back fill procedures. Both are thermoplastic materials, requiring the same considerations for proper embedment and back fill. The popular ASTM standard D2321 applies to both pipe materials.
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Why should I monitor pipe deflection at installation?
Pipe deflection measurement is the tool used to verify the quality of the pipe installation. Deflection should be monitored as the job progresses, so that inadequacies in the installation procedure can be identified and corrected. Deflections exceeding the anticipated (design) deflection are an indication that insufficient soil support is provided. This is an indication that installation methods and/or embedment materials may need to be improved. To confirm compliance with the maximum recommended deflection limit, pipe deflection should be measured 30 days following completion of installation.
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What percentage of external surface scratching or scarring is permissible on HDPE pressure pipe?
Scratches or cuts to a maximum depth of 10% of the pipe wall are acceptable. The depth of the cut or scratch is measured from the pipes original OD surface to the valley of the indentation.
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To avoid kinking the pipe, what is the allowable bending radius of HDPE pipe?
A. The rule of thumb is to use a minimum bending radius of 50 times the nominal diameter of the pipe.
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Is expansion and contraction of HDPE pipe a problem?
No. All objects expand and contract. As with all materials, expansion and contraction must be taken into consideration when designing a HDPE piping system. The resistance to movement provided by friction between the pipe and its embedment is usually sufficient to prevent thermal expansion and contraction.
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After HDPE has been buried and allowed to relax, will the pipe continue to expand and contract a great amount with temperature variations?
No. When HDPE pipe is buried, the temperature of the system becomes much more stable than when it was above ground. Therefore it will exhibit far less dimensional change. Also, the friction between the compacted soil and the pipe offers resistance to movement. Buried HDPE pipe usually does not move after it is buried.
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Are thrust blocks required with HDPE pipelines?
No. HDPE pipe and fittings joined by heat fusion are self-restrained and do not require thrust blocks. It is only at the transition to unrestrained bell and gasketed pipe that provision must be made to limit the transmission of axial forces to the other piping system.
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Are there any guidelines for the maximum length of HDPE pipe that can be pulled along the surface after fusing sections together?
No, there are no general guidelines or rules of thumb. The goal is of course to keep tensile stress in the pipe within allowable values for the pipe type and loading conditions. ASTMF 1804 provides a procedure that can be used to determine the allowable tensile load for pulling polyethylene pipe.
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Are there recommended SDR's for directional drilling?
A. HDPE used in directional drilling must be designed to resist internal pressure, external loadings and pull back forces. Therefore there is no standard or "cookbook" guideline for choosing an SDR. Please consult PPI handbooks chapter on HDD.
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Compared to the host pipeline, when slip-lining or pipe bursting, what diameter HDPE pipe should be specified?
In slip-lining applications, the OD of the HDPE pipe is limited to between 85%t o 95% of the inside diameter of the existing host pipe, depending upon many factors including deflection, sag, bends, etc. PE pipes reduced resistance to flow often fully compensates for the slight reduction in diameter. For pipe bursting application as general rule of thumb is that the host pipe can be upsized two pipe sizes, for example 8 inch can be upsized to 12 inch, 12 inch to 18 inch, etc.
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Must the entire annular space be grouted when sliplining with HDPE pipe?
While grouting is not required for every application, generally it is recommended that it be done. Grouting the entire annular space is good practice. It generally represents only 3 % to 5% of the overall project cost. The annular space must be grouted when the condition of the existing pipe no longer permits it to support soil loads or live loads. lf the ground water level rises above the host pipe grouting may be required to provide adequate resistance to collapse caused by external hydrostatic forces acting on the liner pipe.
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Is HDPE pipe suitable for use under railroads?
Yes, HDPE pipe is suitable for direct burial under railroads with just 4-5 feet of cover. An engineering burial analysis is recommended. Due to the prior poor experience with "brittle" PVC (plastic) pipe, most railway specifications require that all pipe crossings must be encased in steel pipe based on a structural evaluation, impact tolerant HDPE pipe does not require a steel casing, but jurisdictional requirements will usually prevail.
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How are service connections made on HDPE pipe mains?
HDPE pipe can be cold or hot (under pressure) tapped using saddle fusion tapping tees, electro-fusion tapping tees, Fuse-A-Corps, and branch-saddles which are readily available in the industry. There are bolt-on mechanical connections qualified for use with HDPE pipelines as well.
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What are the recommended procedures to pressure test a polyethylene pipeline?
PE pipe is pressure tested in a procedure similar to that used to test other pipes. However the procedure is modified to account for the expansion of the pipe during the application of pressure. The procedure is described in PPI's HDPE pipe Handbooks chapter on inspection, Testing, and Safety.
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Can HDPE pipe be threaded using the same tapping tools commonly used for tapping PVC or ductile iron pipe?
No. Tapping of PVC or ductile iron pipe relies on cutting threads into the pipe wall. Unreinforced HDPE threads loose compression of the taper threads by creep-strain, leading to drip leaks over time.
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How are HDPE pipelines located?
A tracer wire can be buried above the HDPE pipe at the time of installation to facilitate future locates. If no metal wire was installed above the plastic pipe, ground-penetrating radar or acoustic resonance may be used.
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What method is appropriate for leak detection in HDPE pipe?
HDPE pipe is a leak free system when heat fused together. As a "zero" leak-rate pipeline, there is no "specification" for leak detection. However, large leaks are easily detected as water quickly reaches the surface. One of the most promising techniques to find smaller leaks is the audio technique, which listens for the sound emitted as the fluid flows irregularly through an unplanned opening in any pipe.
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Is it possible to repair a damaged HDPE pipe using a full circle clamp?
Yes, a full circle clamp can be used as a temporary repair. The damaged zone should be replaced within a scheduled maintenance period using a HDPE spool section either heat-fused or flanged in top lace.
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How will using HDPE save money?
Using HDPE pipe you create a leak-free system with an exceptionally long service life, that will save money annually on reduced leakage losses, improved water conservation, a reduction in the need for new water treatment plants, reduced warehousing requirements, a reduction in maintenance crews, reduced seasonal water-main breaks, less maintenance, and less rehabilitation and restoration. Savings will accrue for many years to come.
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