noise Top 10 Noise Control Techniques Top 10 Noise Control Techniques... Noise Control - Best Practice The You must control Noise at Work Regulations

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1 Top 10 Noise Control Techniques Top 10 Noise Control Techniques innovative "magic bullets" that may make you think... Low cost, DIY engineering best practice for common problems 1 fan installation details 2 simple ductwork silencing 3 fan speed 4 pneumatic exhausts 5 pneumatic nozzles 6 damping - chutes, hoppers, guards... 7 vibration isolation pads - motors, pumps... 8 upgrade existing guards 9 chains and toothed belts 10 quiet motors - buy quiet retro-fit fan modifications yoghurt-based combustion control bolt-on quiet free collateral quiet Industrial Noise and Vibration Centre: Slough The You must control Noise at Work Regulations Placebo Silencers these regulations are concerned with controlling, not measuring it..." Hearing protection can no longer be used for long term risk management unless it can be proved that control is impractical Companies should not repeat risk assessments that do not include useful and practical information on control Companies should carry out a Noise Control Audit assess the control options using the best of current technology generate cost v reduction trade-offs for each item of noisy plant plan the most practical and cost effective control programme Copyright 2009 INVC

2 k14 Noise Control is... Self-Financing Noise Control Improved efficiency / productivity due to control modifications. Noise control is not a safety issue Noise control is an engineering problem that should be solved by engineering means, in particular through control at source. Effective control must be based on an accurate diagnosis and not on assumptions All the options must be considered, not just the conventional high cost palliatives of enclosures and silencers. These techniques should only be used where it can be proved that there is no engineering alternative. One company had spent 1,600,000 on acoustic enclosures. The Noise Control Audit and subsequent testing proved that using BPM would have saved over 1,000,000 and levels would have been substantially lower and operating costs would be significantly reduced (down-time). Noise source category vibrators burners fans weighing Pay-back Period 4 weeks 1 year 3 years 1 minute... doubled through-put higher efficiency, no cleaning cleaning down-time reduced avoided being shut-down... presses 2 years no enclosures, reduced down-time Noise control costs - 000's conventional best practice Fan Designs axial fan - quiet impellor Fans centrifugal fan Industrial Noise and Vibration Centre: Slough Copyright 2009 INVC

3 m15 Centrifugal Fan Installation m16 Axial Fan Installations NOISY QUIETER NOISY high pressure low pressure >2-3 duct diameters QUIET m35 Fan: Outlet dampers m20 Stalag Chicken-Run Henhouse Up to 19dB tonal reduction from axial fans via modifications to existing fan ductwork to improve flow conditions. As the main neighbourhood complaints were about the 62.5Hz tone, this was a very cost effective solution at 25/fan compared with very large conventional silencers. Copyright 2009 INVC

4 88 Simple Ventilation Silencing m85 Fan Outlet Silencer Cowl 600 mm steel / plywood ventilation silencer for rooms of up to 150m^3 150 mm 1000 mm acoustic absorbent perforated sheet steel 25% open area c3mm holes acoustic absorbent 250 mm 18swg steel sheet duct A simple, cheap absorbent lined cowl can give a 10-20dB(A) reduction in fan inlet /outlet Scrap Can Extract and Chopper Fans Fan Speed v Noise Problem Occupational and environmental tonal Conventional silencers, lagging and enclosures capital cost > c maintenance costs BPM Engineering internal fan modification reduced tones by 23dB and overall by 22dB(A) Cost c no maintenance costs (lasts the lifetime of the fans despite passage of cans) sound modified fan speed reduction reduction db 10% 2 20% 5 30% 8 40% 11 50% 15 Copyright 2009 INVC

5 s85 Cooling Tower Silencer Boiler Burner 16dB tonal reduction w20 Sand Burner Pneumatics Industrial Noise and Vibration Centre: Slough Copyright 2009 INVC

6 Pneumatic Silencers Pneumatic Nozzles Silencer Solutions zero back-pressure silencers - or a larger coupling standardise on 3 sizes fix piped silencers to machine and manifold multiple exhausts Entraining Nozzles c10db quieter for the same thrust use c 20% less air pay for themselves very quickly intrinsically "safe" reduce air pressure... entrained ambient air annulus compressed air directing cone m2 Quiet Nozzle Design Scrap Product Air-Lances db tool clearance (mm) flatjet commercial nozzle Cu pipe Copyright 2009 INVC

7 Filler Cooling Pipes Problem 94dB(A) from cooling pipes for sealed tube ends - rapid cooling a necessity Conventional Solution enclosure - high cost with hygiene and productivity issues BPM Solution Coanda effect linear nozzles 12dB(A) reduction (82dB(A)) improved performance (less turbulence disturbing tubes) 20% less air consumption - pay for themselves very quickly no effect on access or operation Vibration Damping Industrial Noise and Vibration Centre: Slough p10 Damping Thin Plates s90 Vibratory Bottle Unscrambler unconstrained layer of damping material damping material in sandwich construction Problem Vibratory feed hopper for unscrambler generating 90dB(A) damping material damping material deforms only near bends sheet metal damping material made to shear over whole area BPM poor design: vibrators at high level to vibrate whole hopper - feed still inefficient laminated plate inside existing hopper (grommet isolation), connected to vibrators through holes in hopper: cost c 400 reduced vibrator level, improved feed, reduced from 90dB(A) down to 82dB(A) Copyright 2009 INVC

8 m49 Damped Dry Chiller p1 115T Bliss Press Dynamic vibration absorbers designed and fitted to flywheel inside existing guards. Total 8dB(A) reduction under chiller (damping + absorbent) 10dB(A) reduction 20 materials; 1 day fitter time Panel Vib n13 Verso Press Problem High speed strip fed press at 101dB(A) in a quiet area Conventional Manufacturer supplied "acoustic guards" gave only 3dB(A) reduction. Full enclosure suggested. Vibration Isolation Industrial Noise and Vibration Centre: Slough isolation pads BPM Noise Control Audit showed dominant source to be fabricated press legs. Tico isolation fitted between frame and legs tuned to give natural frequency of 65Hz for both legs (different loads) 9dB(A) reduction at closest operator position. 45 materials, 1 man day to fit Copyright 2009 INVC

9 k58 Hydraulic Power Pack n10 Machine Foot Isolation Looking at the diagnostic procedure for this power pack:- m/c foot Tico pad load-spreading steel washer PPack bolt NO ISOLATION Tico pad bolt EFFECTIVE ISOLATION Modify Existing Machine Guards Minimise gaps halving the open area of gaps in a set of guards will reduce the from this source by 3dB reduce the openings by 90% - 10dB reduction Existing Guards Acoustic Absorbent Line a significant proportion of the inside of guards with acoustic absorbent (foam, rockwool) Guard vibration radiated as - use damping... Test mock-ups Industrial Noise and Vibration Centre: Slough Copyright 2009 INVC

10 Modify Existing Guards "Blue Peter" Cardboard Engineering gaps open outfeed no acoustic absorbent ringing box section Belt Drives replace noisy chains with belts use quiet tooth profiles on toothed belts chevron tooth pattern - ultra-quiet Chains and Toothed Belt Drives replace wide belts with a pair of narrower belts toothed belt is very sensitive to belt tension 5-20dB reductions possible Industrial Noise and Vibration Centre: Slough Copyright 2009 INVC

11 Buy Quiet Motors Do not allow your suppliers to spend your money on control without close scrutiny and evidence that they have followed diagnostic best practice Buy Quiet Motors Industrial Noise and Vibration Centre: Slough Remote Control of Noise video sound photos Remote Control Specialised analysis or CD Industrial Noise and Vibration Centre: Slough Free evaluation of control costs and options database Copyright 2009 INVC

12 Top 10 Noise Control Techniques innovative "magic bullets" that may make you think... Low cost, DIY engineering best practice for common problems 1 fan installation details 2 simple ductwork silencing 3 fan speed 4 pneumatic exhausts 5 pneumatic nozzles 6 damping - chutes, hoppers, guards... 7 vibration isolation pads - motors, pumps... 8 upgrade existing guards 9 chains and toothed belts 10 quiet motors - buy quiet retro-fit fan modifications yoghurt-based combustion control bolt-on quiet free collateral quiet Top 10 Noise Control Techniques Further information and case studies: Industrial Noise and Vibration Centre: Slough Copyright 2009 INVC