In the dissertation the data modeling has been shown for the data that regards the damages, which value is above zero. With the use of

Weibull distribution, with prior regression and correlation analysis chosen parameters that defines the life time and failure level of two

populations of AlSi17Cu5 were defined. The calculation sheet of reliability allows to create so called survival diagram, and on the basis of

durability data the average warrantee can be determined, on the pre-exploitation period.

In the paper the reasons for steam pipeline’s elbow material rupture, made of steel 13CrMo4-5 (15HM) that is being used in the energetics.

Based on the mechanical properties in the ambient temperature (Rm, Rp0,2 and elongation A5) and in the increased temperature (Rp0,2t

) it

was found, that the pipeline elbow’s material sampled from the ruptured area has lower Rp0,2 i Rp0,2t by around 2% than it is a requirement

for 13CrMo4-5 steel in it’s base state. The damage appeared as a result of complex stress state, that substantially exceeded the admissible

tensions, what was the consequence of considerable structure degradation level. As a result of the microstructure tests on HITACHI S4200

microscope, the considerable development of the creeping process associates were found. Also the advances progress of the microstructure

degradation was observed, which is substantial decomposition of bainite and multiple, with varied secretion size, and in most cases

forming the micro cracks chains. With the use of lateral micro sections the creeping voids were observed, that creates at some places the

shrinkage porosities clusters and micro pores.