Hi dears,

We have gas turbine F 7EA during start up of the unit after speed reach to 60 % suddenly vibration in bearing 1 & 2 with high temp exhaust and speed control. So we found Atomizing poster compressor motor failure and replace it. After that unit start normally.

My question is there a relation between bad combustion and vibration? I need more detail in that.

 

Dear,

For most GE-design Frame 7EA heavy duty gas turbines 60% speed is the point at which the torque converter is depressurized to stop the transmission of torque to the turbine-generator shaft during acceleration when starting.

If there was high vibration and high exhaust temperature then it's possible there was excessive fuel flowing into the combustors in an attempt to maintain the desired acceleration rate. I would suspect that to cause high vibration there was combustors which were losing flame then reigniting multiple times, and that the exhaust temperature spreads we're also higher than normal.

But because you reported the vibration increased on bearings 1 & -2 I suspect the axial compressor was not fully straight and was experiencing high vibration at or near a critical speed. I can't equate high exhaust temperature and vibration very easily based on the information provided.

Did this happen only once, and then not again on successive starts?

We're the IGVs (Inlet Guide Vanes) in a stable position (they should have been at approximately 32 DGA (DegGrees Angle)) at 60% speed and up to approximately 80% speed under normal circumstances.

Does the unit have DLN-I combustors? If so, does it also have IBH (Inlet Bleed Heat)? If it has IBH, was the IBH Control Valve fully closed at 60% speed?

Does the unit exhaust into an HRSG (Heat Recovery Steam Generator--a boiler)?