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Silencers. Attenuators. Enclosures. Lagging. Conventional fan noise control techniques that can compromise the efficiency of fans or make silencing costly. This presentation provides a guide to best practice in fan noise control, including alternative technologies that can even provide stealth and efficiency, reducing energy consumption and carbon footprint. Remote analysis techniques allow us to apply our fan silencing technology anywhere in the world from the UK.
Citation preview
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Industrial Noise and Vibration Centre http://www.invc.co.uk/noise/noise-control/fan-noise-reduction/
Fan Noise ControlFan Noise ControlBest Practicable Means Best Practicable Means
(BPM)(BPM)
Noise Control Best Practice
noise
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Industrial Noise and Vibration Centre
•Award winning noise control technology for fans £800k capital and £250k / p.a. running cost savings for Corus
•Best Practicable Means (BPM)•Best Available Technology (BAT, BATNEEC) In many cases, (including centrifugal fans, chiller / HVAC
plant, large stacks, burners / combustion) BPM / BAT often cannot be claimed without reference to our technology….
•BPM / BAT Evaluation Often used as the arbiter of what constitutes BPM / BAT –
including court cases
•Buy Quiet Policy De-facto UK standard noise purchasing policy
•Presentations and Training Noise training providers for English, Scottish, Irish
Environment Agencies and local authorities
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Noise Complaints from Industrial Premises
Source: National Physical Laboratory
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Environmental Fan Noise Control is ....
…not just about the overall level…
• Effective noise control must be based on an accurate diagnosis that relates noise features to subjective impact, not on just on assumptions about overall dB(A). Although dB(A) may also be an additional planning / specification requirement, this is often a completely separate issue.
• Noise control should not be implemented at the expense of fan system efficiency. Conventional silencing will often have a significant detrimental effect on fan performance, increasing power consumption (running costs) and the carbon footprint.
• All the options must be considered, not just the conventional high cost conventional palliatives of barriers, enclosures and silencers. These techniques should only be used where it can be proved that there is no engineering alternative.
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BS4142 Fails at Low Frequencies.....
BS 4142 does not work well for noise containing low frequencies. 5dB(A) correction for noise with tones
Tonal noise at 5dB(A) below non-tonal noise should be equally disturbing
Inside rooms, the T.L. of windows shapes the spectrum, reducing mid and high frequency components - almost un-'A' weighting the sound.
BS 4142 is supposed to assess the likelihood of complaints from people in the building.
It should not be used where background noise levels are very low (<30dB(A))
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Industrial Noise and Vibration Centrehttp://www.invc.co.uk/noise/noise-control/fan-noise-reduction/
Fan Noise ControlFan Noise ControlDiagnosisDiagnosis
Noise Control Best Practice
noise
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bedroomwindow open/shut
grinder 5m
cooling towers 1 / 2 at 2m
Cooling Tower Source ID
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Cooling Towers: Detail
Only 71.3Hz blade pass of fans in tower 1 matches bedroom spectrum - grinder and tower 2 are eliminated as sources
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Restaurant Fans and Chiller
Bedroom and room below chiller
Chiller tone at 48.5Hz + harmonics – previous recommendations would not have worked, must isolate from roof
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Industrial Noise and Vibration Centre: www.invc.co.uk
Noise Control TechniquesNoise Control Techniques
Noise Control Best Practice
noise
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Fan Noise Control Options
Techniques by priority and cost effectiveness….
•Control at sourceengineering modificationsefficiency – lowest fan noise coincides with maximum efficiencyvibration isolation and vibration damping
Only if the above are not practical should you consider…
•Silencing
•Enclosures
•Lagging
•Barriers
•Building modifications
Conventionally, these high cost techniques have been the only measures that are considered….
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Innovative Noise Control Technology
These are some of the innovations we use as part of current best practice in environmental noise control.
• Award winning Quiet Fan technology (QFt)
typically 10% - 20% of the cost, no effect on fan efficiency
• Chiller / HVAC noise control
<20% of the cost, free cooling unaffected, higher efficiency
• Fan / combustion stacks
Retro-fit, low cost, fast
• Burner / combustion noise
Unique source control technology – typically <5% of the cost
• Acoustic Camouflage
Psychological electronic silencing
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Placebo Silencers + Acoustic Camouflage
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Centrifugal Fan Installation
high pressure
low pressureNOISY
QUIET
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Fan: Outlet dampers
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Axial Fan Installations
NOISY QUIETER
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Axial Fan Installations
>2-3 duct diameters
NOISY QUIETER
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Efficiency: Fan Speed v Noise
10% 220% 530% 840% 1150% 15
noise reduction dBspeed reduction
• Variable speed drives
• Two speed motors (day and night)
• Proportional control systems
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Splitter Silencer
Mineral Wool
Perforated Steel
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Cooling Tower Silencer
Little attenuation due to material build-up
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Fan Outlet Silencer Cowl
acoustic absorbent
steel / plywood
A simple, cheap absorbent lined cowl can give a 10 - 20dB(A) noise reduction in fan inlet /outlet noise
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Industrial Noise and Vibration Centre: www.invc.co.uk
Reactive and Other Reactive and Other SilencingSilencing
Noise Control Best Practice
noise
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Drying Oven
Problem95dB(A) from gas burners at low firing82Hz "boom" dominant
Enclosurelarge oven - 8m x 4m x 3m @ c £30,000 with serious hygiene and maintenance problems
INVC BPMorgan pipe resonance excited due to weak mixture at low firing
standard weld fume extract motor controlled valves fitted to each inlet
21dB off boom; 8dB(A) overall reduction; £100 each for 12 burners
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Extract Fan System Duct Resonances
30dB tonal noise reductionImproved efficiency
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Damped Dry Chiller
Total 8dB(A) noise reduction under chiller (damping + absorbent)
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Fan: Steel and Elastomeric Spring Isolators
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Axial Vent Fans
8 off axial vent fans with 8m long silencers several stories up
112Hz blade pass problem tone reduced by 20dB by fitting invertors to change speed slightly to avoid resonant condition.
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Yoghurt-Based Noise Control - Boiler Burner
16dB tonal noise reduction
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Industrial Noise and Vibration Centre: www.invc.co.uk
Quiet Fan technologyQuiet Fan technology
Noise Control Best Practice
noise
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OG Centrifugal Fans: Corus
…for the most significant development in noise control technology
12dB noise reduction>£1 million cost saving>£800k capital +c£250k p.a. on power
“INVC’s modifications have brought about a huge reduction in fan noise, improving the environmental conditions across a wide area around the Plant. They’ve also saved us a large amount of money by negating the requirement for major capital expenditure, so it’s been a remarkably successful project.” – Grahame Wallace, Corus.
“INVC’s modifications have brought about a huge reduction in fan noise, improving the environmental conditions across a wide area around the Plant. They’ve also saved us a large amount of money by negating the requirement for major capital expenditure, so it’s been a remarkably successful project.” – Grahame Wallace, Corus.
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OG Centrifugal Fans: Corus
Conventional solutions not suitable:varying fan speedx3 4 megawatt fans (c3.5m high) - loss in efficiency due to silencers unacceptable
Source Control173Hz tone reduced by 12dBsaving of 0.6 - 1.2 megawatts power consumption (carbon footprint)
>£250,000 capital cost saving plus 5 figure savings on annual running costs
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Fan Silencing – without silencers
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Fan Noise Control Options
Techniques by priority and cost effectiveness….
•Control at sourceengineering modificationsefficiency – lowest fan noise coincides with maximum efficiencyvibration isolation and vibration damping
Only if the above are not practical should you consider…
•Silencing
•Enclosures
•Lagging
•Barriers
•Building modifications
Conventionally, these high cost techniques have been the only measures that are considered….
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Remote Control of Noise
video sound photos
email -internet
Specialised analysis
BPM
BAT
Costs
database
experience
@@
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Remote Control of Noise
Romanian power station Laundry fan Ship unloading
Roof-top fans Garage A/C plant Punch press
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Remote Control of Noise
BP Refinery: $1.25m conventional silencers: $0.25m via engineering – no impact on efficiency, no site visit
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Industrial Noise and Vibration Centre: www.invc.co.uk
Fan Noise ControlFan Noise ControlBest Practicable Means Best Practicable Means
(BPM)(BPM)
Noise Control Best Practice
noise
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