TWI Industrial Member Report Summary 913/2008
By M Troughton and C Brown
Background
Welded polyethylene (PE) pipe systems have been in use for around 50 years for the pressurised distribution of fluids such as potable water, sewage and domestic gas. The long-term performance of the pipes themselves is well understood from established regression analysis techniques on pressurised samples at elevated temperatures. However, the longevity of a welded pipe system also depends on the long-term performance of the joints. Numerous short-term tests are used to quantify the quality of electrofusion (EF) joints but there has been little work to correlate the results from these tests with those from long-term tests and, therefore, they cannot yet be used to give an indication of the long-term performance of the joints.
The work described in this report, which is part of the Polytec Systems European-funded project to develop and validate non-destructive testing techniques for EF joints in PE pipes, was carried out to compare the results of various short- and long-term tests currently carried out in industry on EF joints in PE pipes containing various different flaws.
Objectives
- Correlate the results from short- and long-term coupon and whole pipe tests on EF welds in PE pipes made under different welding conditions or containing different known flaws.
- Identify the most suitable mechanical test methods for predicting the long-term performance of EF welds.