Booster Fan Vibration Problems
Booster Fan Vibration Problems
(OP)
Can anybody help.? I am experiencing a repetitive imbalance problem on a two stage Booster Fan. We call experts to come in and they perform balancing (on the Impeller) and the following week the problem comes back again. I have been suspecting the Flue-gas. Currently the Bag-Filters are worn out and when you look into the Booster Fan Housing you can see the blades are wearing off. They are very sharp and I was suspecting that the Flue-gas has too much abrasive material from the Boiler, hence the wearing off of the impeller and probably resulting in increased vibration. BUT my superiors are suspecting the Support structure (Concrete base) and I JUST dont agree with them. The support structure was built in 1991, can the support structure have such a high level input into the Booster Fan getting out of balance?





RE: Booster Fan Vibration Problems
Chris
"In this house, we obey the laws of thermodynamics." Homer Simpson
RE: Booster Fan Vibration Problems
Let us know more about what it is that you are having to deal with with this fan.
rmw
RE: Booster Fan Vibration Problems
RE: Booster Fan Vibration Problems
The guy comes in a does a trial-and-error job of welding weights on the fan blade tips and it gets better, then the next week its out
They are not really experts are they?
As a start, I would suggest that you number the blades and take digital photos of every one each time they are balanced to 'prove' the wear theory.
I would suggest that you get your operations people to trend the fan vibration to see if it gradually increases over the week or goes up in a sequence of step changes?
Did the appearance of this problem coincide with the bag filters being worn out? What is your definition of worn out - are they physically damaged with holes in them or are they blocked? Why don't you just replace the filters with new?
This might not be a balance issue.
You really need to keep a log of how much weight is added and where - a proper balancing routine, would be useful, so you can track the amount of weight and the angle it was added at. This would allow you to calculate the influence coefficient (crudely how much weight corresponds to how much vibration, but this is a vector quantity and the angle is needed)- if this was truly a balance problem, then the influence coefficients would be relatively constant - if there is wide variation, then maybe unbalance is not the issue.
You need some data to figure this out, otherwise you will stay in the 'suck it and see' mode until the fan can no longer be rebalanced.
Here are some things you might want to consider that can produce these symptoms:
a) Cracked shaft
b) Cracked foundation
c) Impeller loose on shaft - not so loose that you can rattle it about, but loose enough to slowly slip around over a period of a week or so
RE: Booster Fan Vibration Problems
I will take every point suggested and look deeper.
The vibration problem seems to have come about at the same time the bag filters failed, at least thats what the Technicians are telling me. I am new in the Reliability section but not the plant. I have never heard of this vibes problem until about towards the end of last year, hence my total disapproval of what some of my colleagues are suggesting, "that the support structure isnt stiff enough"....this is because there are no visible cracks on the concrete foundation and other steel structure supporting the Assembly.
TPL, you asked about the worn bag-filters, they failed, as in holes to the point where you can see dust coming out through the stack and tracks of boiler sand in the fan casing.
The bags have been ordered and they are simply not arriving, AFRICA.!!! I love this place!!!!!!!!!
RE: Booster Fan Vibration Problems
rmw
RE: Booster Fan Vibration Problems
Walt
RE: Booster Fan Vibration Problems
It is possible you have a process problem rather than a mechanical problem with the fan. Such as rmw said about the material buildup on the wheel, this can appear as if you have an imbalance on the wheel itself, but is and imbalance being produced by the material buildup. Clean your wheel via soft sandblasting if you can. If this is your problem and it is related to the filter, then it will keep coming back until you get that new filter.
Do you have vibration spectrums and waveforms to look at? This would also be helpful.
RE: Booster Fan Vibration Problems
(Assuming single plane balance correction)
If it is much less than 3 or 4 times what is recommended for ISO G6.3 I'd say the structure is weak, or worse.
If it is equal or greater than 3 or 4 times G6.3 I'd say the fan is losing material at a too rapid rate.
ISO G6.3 based on rotor weight and rpm can be determined on page 3 (inch) or 4 (metric) here - http://w