We have 2 BFPs coneected in the same header. These pumps are running since 1996. There is vibration in both pumps drive end bearing of the magnitude 35 mm/Sec and 150 microns. No failures have occured due to this vibration, but I want to know the very root cause of the problem.

150 KHI BHEL Make

 

There are a couple of things you need to check to determine the cause of this vibration namely:

1. Is the vibration predominantly radial or axial, and if possible can you get the harmonic content of this vibration? The results you get will lead you better.

2. Is the pump shaft position still balanced, i.e. is the balance piston still functioning properly? You should have a reference mark on the non-drive end side of the shaft, which tells you where the shaft should be with respect to the bearing housing (manufacturer should give you such details). If the balance position is worn out the shaft will move towards the suction side of the pump rubbing internal components. Mind you the pump will still pump, and the wear may be slow enough as to permit 'machining' of the components without catastrophic destruction.

3. Do you have a sliding coupling between drive motor and the pump proper, and is this free or jammed? The pump rotor should be free to move axially irrespective of the drive motor rotor. If this coupling is jammed, then the pump is not allowed to take up its balance position, or worse still the rotor component may be forced to rub with their stator equivalents.

 

Dear,

35 mm/sec? Pump health is deteriorating very fast.
Look at frequency i. e. FFT .Immediate re-balancing is advised. Compare torque required for bare pump to data provided by BHEL.