This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Termoelektrana „Kakanj“ , Kakanj , Bosnia and Herzegovina
Institute "Kemal Kapetanović" Zenica, University of Zenica , Zenica , Bosnia and Herzegovina
Maneco Kakanj , Kakanj , Bosnia and Herzegovina
This paper describes the process of degradation of the structure of the inlet header of the
intermediate reheater (MPr) 2 input header at the boiler of Unit 7 of the Thermal Power Plant
Kakanj, determined on the basis of tests of replicas and hardness at characteristic places of the
header. Headers, with minor delays, have been in continuous operation since 1988. Hardness was
tested at replica pickup sites, on the basis of which the correlation between structure degradation
and hardness drop resulting from exploitation during the long-term high-temperature operation
was estimated.
The change in hardness is certainly one of the most reliable indicators of the structure degradation
degree, which is directly related to the service life of the installed components. The subject of the
test was the inlet header of the intermediate heater made of low alloy steel 15Mo3, consisting of
ferrite-pearlite microstructure, and having calculated values for the allowed hardness in the range
from 133 to 176 HB. The structure degradation assessment was performed according to VGB-S-
517 by comparing the microstructure of the replicates with the corresponding standards, and the
hardness was tested according to ASTM A 956/1996-method A.
The examination has shown that in the exploitation life achieved so far, there has been a partial or
complete degradation of the structure, which is reflected in the initial and delayed coagulation of
the perlite lamellae (Grades 2a and 3a). The hardness at the test sites is at or below the lower than
the prescribed 133HB. The tests confirmed that there is a good correlation between the degree of
degradation of the structure and the hardness, which can be used in assessing the condition and
planning the extent of testing on critical components.
1. INTRODUCTION
As part of the regular tests of critical components of the
The statements, opinions and data contained in the journal are solely those of the individual authors and contributors and not of the publisher and the editor(s). We stay neutral with regard to jurisdictional claims in published maps and institutional affiliations.