Fuel pump noise
Fuel pump noise
(OP)
I work in an office building, where we have a 2000KW power plant on the roof. The fuel pumps and cells are in the basement. Pumps are of a positive displacement variety. For a long time, whenever the pump set is on, one can walk literally anywhere in the building and hear the "whine" of the pump being on line. This is annoying to say the least, and this allows the staff to operate the plant only in the late evening. We had changed out the flexible connections from the pump set to the riser piping in hopes of eliminating the problem, which it hasn't. Now someone suggested to put in a VFD drive to eliminate the noise (in my opinion, the noise is a harmonic resonance, and has more to do with the anchoring arrangement with no sound attenuation, but thats only me). 1- Will this idea work, or is this guy just trying to sell me a VFD? 2-I think adding a VFD to a setpoint below the spec of the system will effect capacity of fuel, no? 3- Is there something I am overlooking? I did check out the springs on the inertia block (steel pan) to make sure there were no problems with suspension. Any help would be appreciated. Thanks- malz





RE: Fuel pump noise
You've looked at 1&2, 3&4 are less likely, so you could try an air reservoir type damper in the fluid line (anti water-hammer). This may need to be tuned to the whine.
A VFD may allow you to find a better operating speed, but it may just change the pitch of the whine.
Cheers
Greg Locock
RE: Fuel pump noise
RE: Fuel pump noise
I really appreciate the help.
RE: Fuel pump noise
Hope it works for you!
RE: Fuel pump noise
RE: Fuel pump noise
rgds.
RE: Fuel pump noise
RE: Fuel pump noise
RE: Fuel pump noise
Please provide details regarding the quarterwavelength resonator. Is this an elecrically powered device? Where would one install it for greatest impact? The name indicates it limits frequency resonance, but we have no indication as to how this is accomplished. Would this be a cost effective answer as it relates to a VFD installation?
Please advise, if you can. Again, I appreciate the assistance, and all the info!!
malz
RE: Fuel pump noise
Bear in mind that all the devices outlined in this paper work over a fairly narrow range of frequencies, so some trial and error will likely be involved in implementation. The less accurate your knowledge of the frequency(ies), the more error you will have with your trials.
RE: Fuel pump noise
The advantage of the Helmholtz resonator is that the attenuation is pretty reliably tunable, and you can get a lot of damping from a small device
fr=c/2/pi*sqrt(Ac/lc/V)
Y=f/fr-fr/f
X=(sqrt(Ac*V/lc))/2/Ap/Y
Transmission Loss (dB)=10*log10(mod(1+X^2))
Ac = Cross-Sectional Area of Connector
Ap = Cross-Sectional Area of Main Tube
lc = Length of Connector
V = Resonator Chamber Volume
fr = Resonant Frequency
c = Speed of Sound
Note that the chamber's linear dimensions should be fairly small, less than wavelength/10.
Beranek (Noise and Vibration Control) has a good discussion of these things.
Cheers
Greg Locock