To obtain the regression curve, laboratory tests are normally carried out on pipe samples subjected to a range of internal pressures, and hence pipe stresses, at 20AC, 60AC and 80AC. The test regime is designed to obtain burst test results at intervals from one hour to more than 10,000 hours (approximately 14 months). Regression analysis is carried out on the test results to predict the long term strength at 50 years and 20AC.
PE100 material has a 50 year Minimum Required Strength (MRS) of 10 MPa. In practice however the actual strength is greater than the design strength and hence the expected resulting service lifetimes are greatly in excess of the nominal 50-year requirement when the pipe is operating within its design envelope.