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This report presents the policies and procedures used by the HSB (Hydrostatic Stress Board) of PPI (Plastics Pipe Institute, Inc.) to develop recommendations of long-term strength ratings for commercial thermoplastic piping materials or pipe. Recommendations are published in PPI TR-4, "PPI Listing of Hydrostatic Design Basis (HDB), Pressure Design Basis (PDB), Strength Design Basis (SDB) and Minimum Required Strength MRS) Ratings for Thermoplastic Piping Materials or Pipe", a regularly updated document.

PPI is a trade association dedicated to promoting the effective use of plastics piping systems. Since the early 1960s, HSB has worked as a volunteer group under PPI's auspices to issue listings and continually evaluate and update procedures for long-term strength forecasting.

Listings are developed from stress rupture data submitted to the HSB by the manufacturer. The general method used to evaluate the data is given in ASTM D2837, "Standard Test Method for Obtaining Hydrostatic Design Basis for Thermoplastic Pipe Materials," for HDB, SDB and PDB listings, or in ISO 9080 for MRS listings, with additional requirements delineated in this report. Many important national and international thermoplastic piping standards, including those issued by ASTM, ISO (International Standards Organization), NSF International, AWWA (American Water Works Association), ANSI (American National Standards Institute), ASME (American Society of Mechanical Engineers) and the API (American Petroleum Institute), reference these HSB/PPI listed long-term strength recommended ratings.

This report was prepared by PPI as a service to the industry. The information in this report is offered in good faith and believed to be accurate at the time of its preparation, but is offered without any warranty, expressed or implied. Additional information may be needed in some areas, especially with regard to unusual or special applications. Consult the manufacturer or material supplier for more detailed information. PPI does not endorse the proprietary products or processes of any manufacturer, and assumes no responsibility for compliance with applicable laws and regulations.

Questions, comments, and problems of interpretation should be referred to the Chairman of the HSB, Plastics Pipe Institute, 105 Decker Court, Suite 825, Irving, TX 75062. Copies of this report, as well as other publications, are available from PPI on the website www.plasticpipe.org.

This report was updated May 2008.