Abstract
The activities and the policies issued by the Hydrostatic Stress Board (HSB) of the Plastics Pipe Institute have significantly enhanced the reliability of pressure rated thermoplastics pipe and the quality of ASTM, American Water Works Association, and other standards that cover such pipes. HSB policies define procedures for the forecasting of the long-term hydrostatic strength of thermoplastics piping materials and for the reducing of this strength into a hydrostatic design stress (HDS). HSB policies have been developed and are periodically updated under the light of our most current understanding of the factors that affect significant strength under actual service conditions. In support of the development of the most appropriate policies the HSB has also conducted various investigative activities. This paper reports on the major contributions that have been made by the HSB. Furthermore, it does so with reference to an overview of the factors that are now recognized as affecting the significant strength under actual service conditions and those that need to be considered when reducing a particular measure of strength into the most appropriate value of a HDS for an intended application.
