Plastic Pipe Facts™

Rochester, New York; Monroe County – Trolley Pump Station Improvement Project1:

In March of 2009, a 1600 LF horizontal directional drill (HDD) was attempted for the force main installation as part of the Monroe County Department of Environmental Services in Rochester, NY.   The specified material was 22” DR17 HDPE pipe.  The initial HDD failed as a result of the pipe buckling and deforming under load and had to be replaced with a thicker walled HDPE product (DR11).

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Plastically deformed HDPE pipe extracted from bore hole after failed pull-in.
Monroe County, NY (2009)

 

As a lower modulus thermoplastic material, HDPE will deform or “creep” under stress or load over time.  This change in material strength over time is referred to as a “time dependent” property and is illustrated by the HDPE trade association (Plastics Pipe Institute) publishing a number of tables in the Handbook of PE Pipe that depict the changing strength of HDPE under load over time.1

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AWWA approved PE3408 will decrease in safe pull stress by 25% in 12 hours - Plastic Pipe Institute, 2nd Edition Handbook of PE Pipe

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AWWA approved PE3408 will reduce in elastic modulus (stiffness) under constant load by over 50% after 1 year of service - Plastics Pipe Institute, 2nd Edition Handbook of PE Pipe

 

 

  1. “Handbook of PE Pipe, 2nd Edition”, Plastics Pipe Institute