Development of Methods for Design and Installation of Long-Lasting Polyethylene Gas Systems. Annual Report January 1985-December 1985

摘要

In 1985, Battelle began a new 4-year research program directed toward four major research tasks--determination of field loads, study of fusion joint integrity, study of squeeze-off, and development of methodologies to analyze and predict performance of PE gas pipe systems. In addition, work was carried out on extended studies of the Slow Crack Growth (SCG) and Constant Tensile Load (CTL) tests and a reexamination of the results of the experimental evaluation of rapid crack propagation. The field load task started with the development of encapsulated strain gages for underground service on PE pipes. Preliminary measurements of squeeze-off effects were made with the stress-rupture test. The SCG test was further evaluated at a wider range of loads and test times and the feasibility of using an nondestructive method of determining damage growth was demonstrated. The CTL test was strengthened by comparing it with other ESCR tests and by applying a bilinear statistical model to the test results. The RCP test results were reevaluated and put on a firmer basis with statistical analyses and a model of initial defect size effect on probability of RCP initiation.