The Plastics Pipe Institute, Inc. (PPI) Power & Communications Division (PCD) recently released a new Technical Note to assist conduit installers in calculating safe pulling loads to avoid damaging high-density polyethylene (HDPE) conduit. TN-63 is available for free at https://plasticpipe.org/pdf/tn-63-2021.pdf.
PPI TN-63 Safe Pull Strength Calculations for Conduit: Including Derating Factors provides not only the equations used to calculate the Safe Pull Strength (SPS) for HDPE conduit but easy-reference tables of pre-calculated SPS values for typical industry HDPE conduit wall diameters and thickness types. Guidance is also provided on how to derate the Safe Pull Strength for elevated temperature installation and time-under-tension considerations.
Installers can quickly look up the Safe Pull Strength for the conduit they are using from the tables, derating it for actual ambient temperature conditions and the time under tension, for use with an in-line tensiometer or in selecting the breakaway link with the correct rating. The SPS values already include the appropriate safety factor.
TN-63 is applicable to any pulled into place installation, including open trench and Horizontal Directional Drilling (HDD) methods. Tables of SPS values are provided for industry-standard DR and Schedule wall types, up to 6 in. in diameter. An explanation of the behavior of conduit under load is provided and guidance on installation considerations is included.
Published on PPI’s website, TN-63 is one of several PPI documents related to the design and installation of HDPE conduit that is published as a service to the industry. The PPI Conduit Design Calculator assists in selecting HDPE conduit types for mini-HDD applications.
For more information, visit www.plasticpipe.org.
