During commissioning of a cogeneration plant the air cooled generator cannot be run up tosynchronization speed because of high 1X vibration during startup. Several attempts weredone by the commissioning team to balance the rotor but proven ineffective. This paperpresents the vibration analysis performed by GE MDS Engineer. As a result of the analysisit was concluded the high levels of synchronous vibration are caused by thermally inducedbow because of rub in the new type of seals installed in generator casing. The seals wereremoved for test and the generator was started successfully. The next part of the paperdiscusses the differences between Newkirk and Morton type thermally induced bows as theycan be observed in the machinery diagnostics during field analysis.
