Fig. 8. Depth of the cracks as the function of work duration
Fig. 9. The vertical vibrations of generator shaft on the exciting side
revolutions. Rotor grazed several gaskets. Besides, that rotor could revolve
for further 30 hours but it was observed that it was distorted for 2.5 mm.
When it was stopped, a crack was found, which was about 98 mm from the
bearing impulsive side and expanded for half of the perimeter. When the
surface of the crack was opened, it was found that half of the cross section
was broken (Fig. 12).
As a result it is was confirmed that vibrational behaviour shown in
Figs. 10 and 11 is characteristic of the rotor with cracks but there is no
assurance that cracks exist in the rotor if it behaves like that. Further
informations are given by the curve of shutting down (Fig. 13). They show
behaviour of this turbogenerator when it was shut down after 50 days and
12 days before it was put out of work. It was observed that for the last 12
days critical number of revolutions
n
2
/
2
moved from 950 to 960 and that
116 ISSN 0236-3941. Вестник МГТУ им. Н.Э. Баумана. Сер. “Машиностроение”. 2009. № 3
