With aging, some large steam turbines at Russian and Ukrainian power plants face problems with thermal expansion. Thsi shows itself in the broken (leap-like) movement of the bearing pedestals during the transients, distortion of casings, and torsion of the foundation cross-bars and then results in high vibraiton, leakage of lube oil and steam from the gland seals, damage of the bearings and couplings, etc. The problems with thermal expansion freedom hamper the turbine start-ups since the relative rotor expansions attain their limits. Long-term experimental and computational investigations made it possible to comprehend why the turbine can lose its thermal expansion freedom. Special mathematical models of the turbine casings and foundation frames allowed analyzing possible deformations of these components in the course of thermal expansion. As a result, a special set of diagnostic, design, and technological measures was developed to reveal the specific causes of the problems and obviate them. Adequate countermeasures completely normalize the turbine's thermal expansion process. Among the most widespread and effective measures are the placing of special fluoroplastometallic bnads under the bearing pedestals, adjustment of the steam-lines' support-and-suspension system, etc.
展开▼
