An elegant engineering solution to your noise or vibration problem may already be available. Search the largest database of noise control at source case studies in the world for best practice alternatives to conventional, high-cost palliatives such as acoustic enclosures, silencers, barriers etc.
The Power Industry International journal published an article about the application of our innovative aerodynamic fan noise attenuation technology to cut not just the cost of noise control projects to reduce the noise from large fans feeding into stacks in the power industry, but also to improve fan efficiency.
The suggestion was that the widespread adoption of the technology could substantially reduce capital and running costs compared with traditional fan noise attenuation techniques such as attenuators, acoustic enclosures and lagging.
The journalist uses the application of the technology to the 50MW Schiller biomass power station in the US as an example. This is the largest power station of its type and uses a huge, house-sized ID combustion fan connected to a stack. The aerodynamic fan noise attenuation was installed within a time window of just 12 hours - compare that with the costly weeks of downtime required to install conventional mufflers. This cut the fan noise by 10dB at fraction of the cost and the fan efficiency was substantially improved.
An interesting point made in the article is that the noise control installation may seem too simple. The industry is used to the idea of massive noise control structures and extensive downtime. Compare that with the option to install elegant aerodynamic inserts inside the fan casing in a few hours to eliminate the noise problem at source without compromising fan efficiency.
Exactly the same point applies to many other industries such as steel and cement industry fans and the associated signature stacks that broadcast the fan noise far and wide.
Read the Power Engineering International fan noise control article
Two newly installed automated tray wash lines had failed to meet the Christian Salvesen Buy Quiet noise specification as they generated 91dB(A), 8 times the hearing damage risk of the 82dB(A) target. This was despite the efforts of the supplier who then proposed fitting a very costly set of additional noise reduction modifications, including an acoustic enclosure.
Asked to evaluate the options, our noise control audit predicted both the cost and the precise noise levels (82dB(A)) that could be achieved using best practice engineering source control techniques. These included:-
- air knife fan geometry and noise path control modifications
- gas burner - bespoke silencer
- water pump modifications
- box impact control
- bale arm pneumatic bespoke silencing
- stacker impact control modifications
Following the implementation of our recommendations by the manufacturer at a tiny fraction of the cost of the previously proposed control measures, the tray wash noise was reduced from the typical 85 – 91dB(A) levels down to or below the 82dB(A) target. Moreover, in addition to the noise reduction, the modifications also improved the drying performance of the units.
The manufacturer has adopted the more effective, lower cost and more practical INVC technology as standard practice, improving their product performance and profit margins...
The noise from die header machines and tableting machines (tablet presses) used to manufacture hard sweets, tablets and other products in the food and pharmaceutical industries is often 95 – 101dB(A). The conventional approach is to fit them with high-cost acoustic enclosures that cause serious access problems and also makes cleaning difficult. Even where enclosures are fitted, noise levels are often still very high. There is a more effective and lower-cost alternative approach.
Accurate diagnosis often makes it possible to reduce the noise at source. In this case, our solution was based on a very precise analysis of the source of the noise energy. This allowed us to more than halve the noise by developing a re-designed cam that not only extended the life of the cam significantly but also reduced operating costs. Coupled with hygienic close shields, this reduced noise levels by 10dB or more at a fraction of the cost of conventional enclosure.
Coupling new acoustic materials and systems with engineering source control technology is re-defining what constitutes noise control best practice in the food, drink and pharmaceutical industries. Whilst conventional acoustic materials (foam, fibreglass, rockwool) pose an unacceptable hygiene problem, we have invested heavily in the development of new techniques specifically for hygienic applications in clean industries that can be implemented quickly and painlessly – often as an extension to a maintenance schedule. The new generation of noise reducing materials includes…
- laminated stainless steel from SoundDampedSteel. This highly damped replacement (or retro-fit upgrade) for existing guides, chutes, guards, hoppers etc is hygienic, rugged, low cost and yet can reduce radiated noise by 10dB – 20dB in conjunction with engineering techniques that cut noise at source
- sound absorbent systems developed by Ecophon that are suitable for use in GMP (Good Manufacturing Practice), high care areas and clean rooms. These can withstand aggressive cleaning regimes, including pressure washing. The recording above illustrates up to 8dB noise reduction via tuned hygienic acoustic absorbent
- all aluminium sound absorbent micro-mesh that is very efficient at absorbing sound with no hygiene implications
These noise control materials and techniques are ideal for the pharmaceutical, electronic and food and confectionery industries where hygiene is a key requirement.
Weighing machines often generate noise levels of 90 – 100dB(A). The conventional approach is to fit partial or full enclosures round each machine. These often produce a noise reduction of only c 5dB(A) (and even an increase at the operator in some cases…) at a cost of the order of £8000 – £15000 per machine – and with the associated access and cleaning problems. We have developed source control techniques that reduce noise levels by 10 – 12dB(A) (typically) with no effect on normal operation, cleaning, hygiene or access – and at a small fraction of the cost of enclosures.
In this case, implementing our techniques reduced the 94dB(A) using the supplied acoustic enclosure down to 82dB(A) (PPE no longer mandatory) with the enclosure removed. This also reduced cleaning downtime from most of a day down to a couple of hours, improving productivity. Successful applications range from confectionery to pharmaceuticals to meat product processing.
This suction fan used in a newly designed, automated pick-and-place system for food packets on a production line generated high levels of noise.
Conventional fan silencing would not only have posed a hygiene problem (attenuators make use of porous acoustic absorbent materials), but would also have required acoustic enclosure. We re-designed the fan mounting system (interestingly, the fan itself was designed for model aircraft engines) and modified the geometry slightly.
Noise levels in a pharmaceutical manufacturing area were 95-100dB(A), dominated by the product air transport fan system. Whilst a traditional high-cost hygienic absorption system could be used to reduce the average area noise level by 5-10dB(A), it would still leave hot-spots of up to 95dB(A) near the air transport fans. As strict hygiene requirements ruled out conventional silencers, novel aerodynamic inserts were fitted inside the fan casings to reduce the tonal noise from these units by close to 20dB with no hygiene or performance implications over the life of the fans.
With the local fan noise eliminated, it was possible to reduce operator noise exposures to well below 85dB(A), reducing the hearing damage risk by around 95%, allowing PPE to be made advisory.
The noise from dozens of vibratory feed hoppers and separators in a pharmaceutical plant generating 95 – 99dB(A) was reduced by 22dB via retro-fit modifications to the geometry and the introduction of sophisticated damping. As an additional benefit, the modifications substantially improved product feed and eliminated persistent fatigue cracking. The cost was not only a tiny fraction of the c £100000 required to fit conventional acoustic enclosures, but there was no effect on access/cleaning (unlike acoustic enclosures) and productivity was significantly improved.
A similar approach has also been successfully applied to control the noise from vibratory bottle feeders to give an 8dB(A) reduction at a cost of c£500 and with substantially improved performance and productivity.
Contact us if you'd like to discuss a particular project.
We have also generated a comprehensive technical note on all aspects of vibrating feeder, hopper, conveyor and screen noise...
Other examples of our engineering vibratory system noise reduction technology include:-
Manufacturers are under increasing commercial pressure from their customers to develop low vibration plant. The innovative low vibration handle developed by the INVC for a Dennis Mowers lawn-mower reduced operator exposure from 6m/s^2 down to 2m/s^2 – without compromising mower control. This is a dramatic improvement that would allow operators to use the mower all day without reaching the 2.5m/s^2 Exposure Action Value.
Flash removal from hand-held aluminium components generated 32m/s^2 – the Exposure Limit Value (ELV) would be reached in 12 minutes, severely limiting production. Detailed analysis revealed dominant vibration was caused by a pedestal grinder component rest resonance. It was replaced by a floor mounted version that improved the ergonomics and reduced the vibration to 1m/s^2, allowing unlimited use without risk of HAVs.
A hand-held Ingersoll Rand sand rammer packing concrete lintel moulds generated 28m/s^2 with a maximum trigger time of only 15 minutes/day before reaching the ramming tool vibration control Exposure Limit Value, seriously limiting production. We designed a mass / sprung balance system that reduced the vibration to 11.5m/s^2, extending the “safe” trigger time to 90 minutes/day. Combined with substantial ergonomic improvements, operator HAVS risk was virtually eliminated and there were large productivity gains. As the whole project was completed within days (no site visit) via information (data, video) forwarded by email, the total cost was a few £hundred, making it self-financing over a few days.
Vibration from riveting on a bench jig posed a very high risk of HAVS. Our redesigned, stiffer jig reduced the riveting time by 50% and the vibration by 25%. This cut the overall operator dose by nearly 90% – improving productivity as a side effect.
The operator used a spanner on one side of conveyor frames and an impact wrench on the other, producing significant HAVS risk in both hands. We recommended a larger, more ergonomic spanner and a more powerful wrench. These measures halved the vibration dose and significantly improved productivity.
High-speed bits were used to trim aluminium panels, but the tool speed was far too low. Changing the die grinder for a high speed unit to match the bit left the vibration unchanged, but the improved efficiency cut working time from 20 minutes to 2 minutes, reducing the risk by a factor of three. On a similar operation, simply ensuring the grinding bit was pushed fully into the chuck reduced the level of vibration by a factor of x4.
Designing a shorter stirrer bar and reducing the speed of a hand held paint stirrer reduced the 30m/s^2 vibration level to 8m/s^2 without affecting performance.
