January 2, 20206 yr 12 minutes ago, Moonshine said: What is of note in these measurements is the blade pass frequency is not the dominant noise, and the peaks at ~480Hz, 600Hz, 750Hz, 1000Hz, and 1600Hz are circa 10 dB louder (even more so than the 200Hz tone once A-weighting is applied, if it hasn't been already), though don't follow a harmonic relationship. Just thinking about these 5 peaks (also there is a possible 6th at 500Hz), and its getting into the realms of condition monitoring, / diagnostics e.g. the 500Hz, 750Hz, and 1000Hz could be related. @readiescards can you confirm the operating RPM of the machine?
January 2, 20206 yr Author The plate says: 1450 rpm 37 kW 400 V 70 A 50 Hz 3 phase Rewind (and probably last time balanced etc) 28/10/2011 Though watching the fan slow down to stop it seemed very well balanced. I believe there are 12 blades from looking at this pic: I used an Android app called Recorder with high quaility enabled on a Samsung S10 this created an AMR file that I opened in Audacity using the FFMPEG extension and applied no filtering.
January 2, 20206 yr Author You can download the amr file here: http://rigsbywoldholidaycottages.uk/documents/Rigsby-Farm-Fan-At-Close-Quarters.amr Sorry don't know how to make the forum make this a download link Edited January 2, 20206 yr by readiescards add comment about download
January 2, 20206 yr 44 minutes ago, readiescards said: The plate says: 1450 rpm 37 kW 400 V 70 A 50 Hz 3 phase Rewind (and probably last time balanced etc) 28/10/2011 Though watching the fan slow down to stop it seemed very well balanced. I believe there are 12 blades from looking at this pic: I used an Android app called Recorder with high quaility enabled on a Samsung S10 this created an AMR file that I opened in Audacity using the FFMPEG extension and applied no filtering. Looking at that picture it looks more like 8 fan blades, with a rpm Of 1450 that is a blade pass Freq of 193 Hz, that doesn't tally with the noise measurements. I would use a wav recorder app as that AMR file is probably doing some funky masking ala mp3, Which may not accurately represent the noise levels are.
January 3, 20206 yr Could the fan be swapped out for a more modern, quieter design? A very brief read here I think suggests a (slight?) increase in drawn power whilst retaining the same airflow. https://www.physicsforums.com/threads/avoiding-acoustic-noise-from-the-electric-motor.415377/ Guessing the shaft / key will be imperial. On those lines I assume you've had the fan cover off and looked for blade damage or it being loose? Ditto clean out the accumulated, compacted dust & fluff. Check the mesh grilles too in case they're vibrating. A chance that changing the bearings for top quality ones might help. If you rotate the shaft manually how does it feel/sound? I've just changed a 24/7 run, fuel store fan's bearings for noise/vibration issues as I might have said earlier. Midland bearings are good. "You can have top quality for £40, Japanese for £20 or Chinese for £6". ? Needless to say the 3 Chinese ones in my kid's Jeep are still going strong alongside their posh (darker blue) sibling!
January 3, 20206 yr On 05/09/2017 at 01:56, Ferdinand said: How much will your rental income be reduced by for those 2-3 weeks per year due to a temporary noisy environment ? £500-£1000 per annum? Or a lot more? Are the works justified? this sounds like simplesat way around the problem- just don,t let them out then --or have a 50% discount to deaf people for that period .LOl -If that motor really is a 37kw = 45hp+ motor --then thats alot of air its moving and alot of noise it will be making and I don,t see any way that you going to minimize it --other than moving the unit a long way to its own building away from where it is I have a 7.5kw snail furnce fan for my dyno --and the noise from that is not the motor its the air its moving ---it makes a 60mph wind ,no way to silence that Edited January 3, 20206 yr by scottishjohn
January 3, 20206 yr Author It is difficult to block out the dates as when the harvest comes in can vary +/- a couple of weeks and if the wheat is wet or hot then we need to run the fan when ever the weather lets us so can easily be a few months of on and off use. Yes it is a 37kW fan. Bearings seem ok when I did a quick test the other week. I'll give the blades a good clean and see if that improves it.
January 4, 20206 yr How much cash are you willing to spend on this? Was thinking that maybe two fan units, with the same airflow may be a bit quieter. https://www.engineeringtoolbox.com/fan-noise-d_61.html Edited January 4, 20206 yr by SteamyTea
January 10, 20206 yr Author On 04/01/2020 at 09:24, SteamyTea said: How much cash are you willing to spend on this? Was thinking that maybe two fan units, with the same airflow may be a bit quieter. https://www.engineeringtoolbox.com/fan-noise-d_61.html Budget is £1000 so not intending to replace unit (at this stage)
January 10, 20206 yr can you not just move it it away from proposed units ?, If not then accept no rental when you using it-or serious reduction-thats a NO cost option ,just loss of income for a couple of weeks, Edited January 10, 20206 yr by scottishjohn
January 10, 20206 yr 44 minutes ago, readiescards said: Budget is £1000 so not intending to replace unit (at this stage) I think that your best bet is still to put a fence up like the attached, in the location shown in one of my previous posts. This uses 34mm T&G boards, though as below a 28mm board is £6.52 inc vat per 3m (not delivered) https://www.tuin.co.uk/Tongue-and-Groove-28mm-Timber.html Assume you need a 4m x 3.5m high fence, that is ~40 boards @ £260, add in the delivery, fence posts/misc timber, concrete you could probably probably do it for £500-600 in materials. Have you been able to get any .wav file recordings of the fan in operation and in the house that the issue is occurring? Jakoustic Fencing System 3500mm.pdf
January 13, 20206 yr Author Moving it would not resolve the issue - just giving a different property a noise issue. Sound fencing certainly seems the most viable option the only trouble is that it needs to easily removal and replaced as they is very little space between the fan entrance and the barn door entrance and we need all that for grain loading.
January 13, 20206 yr 1 hour ago, readiescards said: Moving it would not resolve the issue - just giving a different property a noise issue. Sound fencing certainly seems the most viable option the only trouble is that it needs to easily removal and replaced as they is very little space between the fan entrance and the barn door entrance and we need all that for grain loading. OK so that sounds like you need a big hinged door ..?? Concrete a steel post into the ground and put the other end on a wheel..? Make a frame of 100x50 RHS and fit the panel to it ..? May need some sort of way of hinging the bottom edge so you don’t get sound transferring through the gap but all doable
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