identify the cause of the failures
identify the cause of the failures
(OP)
The purpose is to identify the cause of the failures and make corrective repairs. The pumps have been in service since the late 1970's and have exhibited high vibrationa at vane pass frequency but operated with normal maintenance without failure for approx 10 years at a time. Since 2003, five of the pumps modified with new diffusers to reduce high vibrations at vane pass frequency. All had balancing device and thrust bearing failure. the modified diffusers have 9 vanes instead of 8. This is a boiler feed 5 stage pump. I did the CFD analysis of considering the cases of 8 & 9 vanes but as per that analysis hard to say anything.





RE: identify the cause of the failures
RE: identify the cause of the failures
RE: identify the cause of the failures
Is there some reason you can't get them rebuilt by manufacturer A? ... and restored to their original design, or one that's evolved in the correct direction?
Mike Halloran
Pembroke Pines, FL, USA
RE: identify the cause of the failures
Anyway- it seems that even though you have high frequency vibration with the OEM design, the life of the pump was better and you should consider reverting to the original and look into the frequency problem again.
RE: identify the cause of the failures
RE: identify the cause of the failures
1. The second OEM reduced the A gap to .03 inch in the last stage.
2. Change in the diffuer design (8 to 9 vanes).
As per my thinking diffuser is not playing any role here. May be the 7 impeller vanes & 9 diffuser vanes combition is not right. There are some charts but i am not having right now. A Gap can play an influnce on this problem as it is reduced considerable (from .079 to .039) but I need some proof to proov this. The most of the OEM's are using the values like .040 & sometimes even less value. I have calculated the resultant thrust also. The total resultant thrust is 11.21 E04 lbs. By considering this thrust, i have calculated the counter bore diameter of balance drum. As per my calculation that diameter is 9.65. As per the drawing the diameter is 9.40. This may also be the possible cause of failure.
3. There was no taper on balance drum & balance sleeve. There is a full sucface contact.