7.4. Over Speed Test The purpose of the test is to check rotor structural integrity and to allow settling of each item assembled on the shaft. Since the rotor will be tested in the bunker at Over Speed (OS), high vibrations could occur even if LSB has been performed accurately. In this case supports can be locked. The operations shall be executed recording the synchronous vibrations (mm/s) on both pedestals (amplitude and phase for each pedestal). A diagram “vibrations and phase vs. speed of rotation” for both the rotor end, from 0% to 121% of MCS, must be prepared. The OS test operating sequence shall be: 1. Increase the speed gradually up to the 121% of the MCS (Over Speed OS). After 2 minutes at the OS, decrease slowly the speed up to LSR (25% of 1st critical speed). 2. Let the rotor stabilize, for 5 minutes at least, at the LSR. 3. Increase the speed gradually up to MCS. 4. Let the rotor stabilize, for 10 minutes at least, at the MCS. 5. Increase the speed gradually up to TS. 6. Let the rotor stabilize, for 2 minutes at least, at the TS. 7. Slow down the rotor at the LSR. 8. Rotor shall be tested more times to check the repeatability of the measured values on 2 consecutive tests at least (after the second test, if necessary, additional runs shall be executed up to the TS). 9.During the test, if it is installed, the operation of the mechanical trip device must be checked (when the trip device comes into operation an increase of the vibrations amplitudes occurs) and, if necessary, its setting shall be performed according to the test specification document.