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Fan noise control best practice CIEH Nov. 2013

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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.

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Fan noise control best practice CIEH Nov. 2013

  1. 1. Noise Control Best Practice noise www.invc.co.uk Fan Noise Control Best Practicable Means (BPM) Industrial Noise and Vibration Centre http://www.invc.co.uk/noise/noise-control/fan-noise-reduction/
  2. 2. 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 www.invc.co.uk • 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
  3. 3. www.invc.co.uk Noise Complaints from Industrial Premises Source: National Physical Laboratory
  4. 4. 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. www.invc.co.uk • 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.
  5. 5. 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. www.invc.co.uk  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))
  6. 6. Noise Control Best Practice noise www.invc.co.uk Fan Noise Control Diagnosis Industrial Noise and Vibration Centre http://www.invc.co.uk/noise/noise-control/fan-noise-reduction/
  7. 7. Cooling Tower Source ID cooling towers 1 / 2 at 2m www.invc.co.uk grinder 5m bedroom window open/shut
  8. 8. www.invc.co.uk Cooling Towers: Detail Only 71.3Hz blade pass of fans in tower 1 matches bedroom spectrum - grinder and tower 2 are eliminated as sources
  9. 9. Restaurant Fans and Chiller www.invc.co.uk Bedroom and room below chiller Chiller tone at 48.5Hz + harmonics – previous recommendations would not have worked, must isolate from roof
  10. 10. Noise Control Best Practice noise www.invc.co.uk Noise Control Techniques Industrial Noise and Vibration Centre: www.invc.co.uk
  11. 11. Fan Noise Control Options Techniques by priority and cost effectiveness…. •Control at source engineering modifications efficiency – lowest fan noise coincides with maximum efficiency vibration isolation and vibration damping Only if the above are not practical should you consider… •Silencing •Enclosures www.invc.co.uk •Lagging •Barriers •Building modifications Conventionally, these high cost techniques have been the only measures that are considered….
  12. 12. 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 www.invc.co.uk • Burner / combustion noise  Unique source control technology – typically <5% of the cost • Acoustic Camouflage  Psychological electronic silencing
  13. 13. www.invc.co.uk Placebo Silencers + Acoustic Camouflage
  14. 14. Centrifugal Fan Installation high pressure NOISY www.invc.co.uk QUIET low pressure
  15. 15. www.invc.co.uk Fan: Outlet dampers
  16. 16. Axial Fan Installations www.invc.co.uk NOISY QUIETER
  17. 17. Axial Fan Installations >2-3 duct diameters www.invc.co.uk NOISY QUIETER
  18. 18. Efficiency: Fan Speed v Noise • Variable speed drives • Two speed motors (day and night) • Proportional control systems noise reduction dB 10% 20% 30% 40% 50% www.invc.co.uk speed reduction 2 5 8 11 15
  19. 19. Splitter Silencer www.invc.co.uk Mineral Wool Perforated Steel
  20. 20. www.invc.co.uk Cooling Tower Silencer Little attenuation due to material build-up
  21. 21. Fan Outlet Silencer Cowl steel / plywood www.invc.co.uk acoustic absorbent A simple, cheap absorbent lined cowl can give a 10 - 20dB(A) noise reduction in fan inlet /outlet noise
  22. 22. Noise Control Best Practice noise www.invc.co.uk Reactive and Other Silencing Industrial Noise and Vibration Centre: www.invc.co.uk
  23. 23. Drying Oven Problem 95dB(A) from gas burners at low firing 82Hz "boom" dominant www.invc.co.uk Enclosure large oven - 8m x 4m x 3m @ c £30,000 with serious hygiene and maintenance problems INVC BPM organ 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
  24. 24. Extract Fan System Duct Resonances www.invc.co.uk 30dB tonal noise reduction Improved efficiency
  25. 25. www.invc.co.uk Damped Dry Chiller Total 8dB(A) noise reduction under chiller (damping + absorbent)
  26. 26. www.invc.co.uk Fan: Steel and Elastomeric Spring Isolators
  27. 27. Axial Vent Fans www.invc.co.uk 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.
  28. 28. www.invc.co.uk Yoghurt-Based Noise Control - Boiler Burner 16dB tonal noise reduction
  29. 29. Noise Control Best Practice noise www.invc.co.uk Quiet Fan technology Industrial Noise and Vibration Centre: www.invc.co.uk
  30. 30. OG Centrifugal Fans: Corus 12dB noise reduction >£1 million cost saving >£800k capital + c£250k p.a. on power www.invc.co.uk “INVC’s modifications have brought about a huge reduction in fan noise, “INVC’s modifications have brought about a huge reduction in fan noise, improving the environmental conditions across a wide area around the improving the environmental conditions across a wide area around the Plant. They’ve also saved us a large amount of money by negating 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 requirement for major capital expenditure, so it’s been a remarkably successful project.” – Grahame Wallace, Corus. successful project.” – Grahame Wallace, Corus. …for the most significant development in noise control technology
  31. 31. OG Centrifugal Fans: Corus www.invc.co.uk Conventional solutions not suitable: varying fan speed x3 4 megawatt fans (c3.5m high) - loss in efficiency due to silencers unacceptable Source Control 173Hz tone reduced by 12dB saving of 0.6 - 1.2 megawatts power consumption (carbon footprint) >£250,000 capital cost saving plus 5 figure savings on annual running costs
  32. 32. www.invc.co.uk Fan Silencing – without silencers
  33. 33. Fan Noise Control Options Techniques by priority and cost effectiveness…. •Control at source engineering modifications efficiency – lowest fan noise coincides with maximum efficiency vibration isolation and vibration damping Only if the above are not practical should you consider… •Silencing •Enclosures www.invc.co.uk •Lagging •Barriers •Building modifications Conventionally, these high cost techniques have been the only measures that are considered….
  34. 34. Remote Control of Noise video sound photos @ @ www.invc.co.uk BPM BAT Costs Specialised analysis database experience email -internet
  35. 35. Remote Control of Noise www.invc.co.uk Romanian power station Roof-top fans Laundry fan Garage A/C plant Ship unloading Punch press
  36. 36. www.invc.co.uk Remote Control of Noise BP Refinery: $1.25m conventional silencers: $0.25m via engineering – no impact on efficiency, no site visit
  37. 37. Noise Control Best Practice www.invc.co.uk noise Fan Noise Control Best Practicable Means (BPM) Industrial Noise and Vibration Centre: www.invc.co.uk

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