Gas Distribution FAQ
Yes. The premier and original calculator for HDPE piping applications, PlexCalc™ allows users to perform a number of PE pipe calculations for Performance Pipe’s DriscoPlex® products. Pressure ratings, fluid flow rates, reactions to burial and traffic loading, thermal effects, deflection between above-grade supports, safe pulling strength, allowable bend radius, and many more important calculations can be made using PlexCalc™, found on our website and as an app in the Apple App Store as well as Google Play for Android devices.
Pressure ratings for common DRs and typical temperature and environmental conditions are shown in our product flyers. Pressure ratings accounting for different temperatures, environmental applications, etc. can be determined using PlexCalc™. For gas piping under federal regulation, the equation to calculate pressure rating with the appropriate design factors in accordance with 49 CFR 192.121 is shown in our Gas Brochure.
Normally it is not a concern for buried municipal water or sewer pipelines. Soil will provide sufficient restraint against movement. However, thermal effects must be considered for above-grade or aerial pipelines. The unrestrained expansion/contraction coefficient for PE pipes is approximately 9 x 10-5 in/in/°F. See technical note PP814 Thermal Effects for more information.
- Safe burial depths vary and should be calculated. In lieu of calculations, AWWA says that for an embedment soil with an E' of 1,000 psi and no surface water, HDPE pipes with DRs ranging from 7.3 to 21 can be safely buried from a depth of 2 ft to 25 ft where no traffic load is present and from 3 ft to 25 ft where H2O live load is present.
- Most pipes can be buried to deeper depths. Equations for calculating burial depth may be found in Chapter 6 of the PPI Handbook of Polyethylene Pipe.
Design information for HDPE pipe is located on the Download Page of our website. You will find links to technical notes, fusion guides and the field handbook. There is also a link to the Plastics Pipe Institute Handbook of Polyethylene Pipe. Other resources include product flyers and brochures, historical literature, submittals, and packaging information.
Engineering data for HDPE and PE pipes may be found in Chapter 3 of the Plastics Pipe Institute Handbook of Polyethylene Pipe, which may be found at www.plasticpipe.org. Engineering information may also be found in the various Performance Pipe technical notes. Look on the Download Page for a link to technical notes.
- PE is a ductile material and has exceptional impact strength. As an example, AWWA publishes an Izod Impact resistance value of 10–12 ft-lbf/in for HDPE and of 0.65 ft-lbf/in for PVC. PE superior impact strength provides a piping system that is nearly impervious to impact damage and to damage from improper tapping.
- In the real world, engineers understand that pipes must be tough and resist impact and handling damage. PE pipes are field tested and proven to be impact tough.
Yes. Every day more utilities realize the advantages of trenchless technology. More trenchless projects are being installed than in the past because of cost savings. Savings result from quicker installations, faster permitting and design time, fewer disruptions to business and residents, less damage to parks and trees, and less disturbance to roadbeds (and subsequent road repair).
Aside from the low cost of PE pipe, long-term savings may be realized due to PE pipe’s fusion joints and corrosion resistance. Leakage rates for fused PE systems are far lower than for gasket-jointed DI or PVC systems. PE pipe resists corrosion. It will not undergo tuberculation and is unaffected by “hot” soils or electrogalvanic corrosion, thus PE pipes last longer in the ground. Additional savings may be realized by trenchless installation. Go to www.PEpipe.org for more information.
In a pumped system, the maximum operating velocity is limited by the surge pressure capacity of the pipe. The Plastics Pipe Institute Handbook of Polyethylene Pipe states that “if surge is not a consideration, water flow velocities exceeding 25 feet per second may be acceptable.”
Safe pull strength can be found in Performance Pipe technical note PP803 Pull-in Applications or by using PlexCalc™.
HDPE pipe can be cold bent to a minimum bending radius of R = α x OD, where R is the minimum bend radius, OD is the pipe’s outside diameter, and α is the minimum bend ratio. The minimum bend ratios shown below are for a long-term application based on the pipe DR. The pipes may be bent to a tighter radius during installation; see technical note PP819 Field Bending of PE Pipe.
|Dimension Ratio, DR||Minimum Bend Ratio, α|
|Fitting or Flange Present in Bend||100|
ASTM F2620 addresses heat fusion of HDPE pipes. Also, see Performance Pipe PP750 Heat Fusion Joining Procedures and Qualification Guide for information on fusing DriscoPlex® pipe products. Videos showing correct butt, saddle and socket fusions, along with other fusion literature, can be found on our Fusion page. Fusion information on Performance Pipe historical products such as Driscopipe® and Plexco® pipe can be found on the Download Page.
- Yes. Polyethylene pipe has been heat fused for almost fifty years in a wide range of service applications. The window of conditions that are acceptable for good quality fusion joints is broad, and the long-term performance is documented in actual field applications as well as in long-term testing. PE pipe joints are standardized through ASTM fusion procedures as well as recognized in AWWA, PPI, ASME and other industry standards.
- There are new technologies that attempt to mimic the advantages of PE fused joints for other pipe materials. However, these materials do not have the history, the proven performance, and the industry peer-reviewed standardization of PE pipe fusion joints.
A complete line of molded PE fittings including tees and MJ adapters up to 8" IPS and molded PE flange adapters up to 18" are available from Performance Pipe. For more information, see our Fittings page. Additional fittings and sizes are available through other PE suppliers.
- When external third-party damage does occur, there are several repair methods. Punctures in PE pipe may be repaired using electrofusion repair saddles or mechanical repair clamps.
- If the damage is sufficiently extensive that a pipe section must be removed, the pipe section may be replaced with a spool piece of the pipe connected on each end to the exiting pipe using mechanical fittings, electrofusion couplings, or flanged connections. Refer to the PPI Handbook on HDPE Pipe Repair and Maintenance.