Application of the CEN (European Committee for Standardization) small punch creep testing code of practice to a representative repair welded P91 pipe

The small punch test has particular value in life prediction of plant components operating at high temperatures under creep conditions since the test requires very small amounts of material which can be acquired from operating equipment in a virtually non-destructive manner. The application of the small punch test for creep has gained significant interest in the last decade, primarily as a result of research coordinated by the European Pressure Equipment Research Council to develop a CEN code of practice for the application and use of the small punch test for both creep rupture and tensile and toughness properties. This paper briefly summarizes the EPERC round-robin work leading to the creep part of the code of practice and key aspects of the code. This is followed by a detailed example of implementation of the code for studying the creep behaviour of a representative repair weld between service exposed and virgin P91 piping. Small punch creep tests have been carried out on both the pipes, the weld and areas from the heat-affected zone on both sides of the weld and the results interpreted to aid remaining lifetime predictions for this type of component.