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Case studies

Some businesses made presentations at the Buy Quiet event to describe how they changed their working environments for the better by adopting the Buy Quiet message. They were:

Steve Hopkins, Swindon Commercial Services

Steve Hopkins, Health, Safety and Risk Manager at Swindon Commercial Services, reported that he needed to modify equipment to make it safer:

We had an issue with noise from our recycling vehicles as workers emptied bottles into the hoppers. The metal skin of the vehicle amplified the noise of glass striking glass.

A noise assessment gave readings of over 90dB. We didn’t want to give our workers ear protection, as they wouldn’t be able to hear oncoming traffic when working in the road. So we came up with a simple solution – line the hoppers with rubber, and fit noise-absorbent plastic flaps on top of the hoppers. Additionally, the hoppers are angled downwards so that bottles slide towards the middle before falling from a lower height onto the glass below.

A number of other local authorities have expressed an interest in our design, which won an Institute of Occupational Safety and Health award for innovation in health and safety.

This relatively low-cost solution (around £2000 per vehicle) has proved a success by reducing the noise levels to 81dB. Staff are happy with the design; we can help protect their safety when working on roads as they can hear the traffic.

Chris Emmins, Saint-Gobain Abrasives

Saint-Gobain Abrasives manufacture products for the building and construction industry, including diamond blades, diamond core drills, machines, cutting and grinding wheels, and coated products for use on a variety of materials and many different kinds of equipment.

Saint-Gobain Abrasives demonstrated a low hand-arm vibration floor saw and a diamond blade with noise dampening (it’s used for cutting through a wide variety of building and construction materials) at the Buy Quiet event.

Diamond cutting products have been around for over a century, with tremendous advances having been made in recent years, in both performance and manufacturing processes.

A lot of people look at cost first when choosing new equipment and consumables, but there are real advantages in reducing noise and vibration, especially when working in public places. There’s a premium to be paid for products that last longer, cut quicker and are much quieter.

Local authorities are among our main target customers, and they can do a lot to promote the use of quieter machinery during the tender process. These authorities and other progressive specifiers will show others just what this type of equipment is capable of.

Tony Turner, GreenMech Ltd

Tony Turner presented on the development of a quiet wood chipper. Much of the need for development of a lower noise machine had been driven by environmental issues, that is, to overcome noise curfews in some neighbourhoods. But the quieter machines were also better for the operators. Tony reported how the sound power level had been reduced from 120 dB to 114 dB for the new wood chipper within a weight constraint of 750 kg. GreenMech are working on a larger and more powerful model with no weight constraint and expect to achieve sound power levels below 110 dB – a ten-fold reduction in the emission of acoustic power.

Noise exposures for comparison with the action levels in the Control of Noise at Work Regulations 2005 are based on another measure of noise - the sound pressure level at the operator’s position. Tony reported that the noise at the operator position had been reduced from about 105 dB to about 95 dB – about a halving of the loudness and a huge reduction in risk of deafness.

The reduction in noise, though significant, still leaves noise exposures above the exposure limit value of the Regulations in most cases and above the exposure action levels in virtually all cases. An operator is likely to be exposed at the exposure limit value of 87 dB LEP,d if working this machine without hearing protection for more than about 1¼ hour per day.

Wearing of hearing protection is mandatory for most users of both the original machine and the quieter machine. The reduction of noise at the operator station from 105 dB to 95 dB means that there is a much better chance of preventing deafness using a hearing protection programme because the associated increase in exposure is much smaller when the acoustic seal of the hearing protection is broken – for example, when chewing or talking.

GreenMech had achieved these commendable reductions in noise emission by careful consideration of the design of their wood-chipper. They identified the features of machines that lead to high noise and were able to redesign those features in a way that not only reduced the noise but improved the productivity and efficiency of the machine at the same time.

Peter Wilson, INVC

Peter Wilson of the Industrial Noise and Vibration Centre (INVC) gave a presentation that covered several examples of implementing Buy Quiet purchasing policies and of developing quiet versions of plant in conjunction with the manufacturers.

Vibratory Grader: Food Industry: retro-fit

A food manufacturer had ordered a vibratory grader to the INVC “Buy Quiet” standard. The supplier had attempted to meet the target noise level (less than 85dB) using an enclosure over the noisiest part of the line. We were called-in to the supplier when initial pre-delivery testing showed noise levels of 99dB. Within a couple of days, we had come up with a set of retro-fit engineering modifications (vibration damping, isolation and geometry changes) that reduced the noise to 85dB at a cost of c £4k (on a line costing c £250k). One of the main technical challenges was the requirement for a very high level of hygiene – which would have been impossible to meet using conventional acoustic materials. If the noise control measures had been designed-in, then they would actually have reduced the overall cost of the line by c £5k or more.

Compressor

We worked with the manufacturer to modify a packaged compressor to reduce noise levels within a smaller envelope. The objective was to remove the silencer element (so that transportation costs would be reduced) with no increase in noise or reduction in cooling. Detailed diagnosis led to the development of engineering changes in the form of fan modifications, subtle changes in geometry and some of the materials used. As a result, even with the silencer removed, the unit was 4dB quieter than before and with much reduced tonal noise and with no change in the manufacturing cost. These results provided a significant technical improvement that could be used for marketing as well as reducing costs.

Vibratory Sieves

The manufacturer was experiencing pressure from customers to reduce noise levels from new machines. Traditionally, covers and acoustic enclosures had been used, but these were not only very costly, but they also introduced access and hygiene problems for many applications.

Instead of looking at conventional palliative “sticking plaster” techniques such as covers, we carried out a detailed diagnostic review of the machine vibration and radiating surfaces. One of the benefits of working closely with the manufacturer is that it often allows very low cost engineering noise control modifications to be built-in. In this case, the main changes involved developing a way to manufacture highly damped versions of key components. Coupled with a few minor design changes, this resulted in a typical noise reduction of 5dB at a cost of around £300/machine - in very many cases, this was sufficient such that PPE would no longer be mandatory in the vicinity of the sieves. As the modifications could also be retro-fitted to existing machines with no effect on access, maintenance or hygiene, this was a very attractive potential upgrade.

Hosiery toe closer

A major customer had implemented the INVC Buy Quiet programme in order to reduce the requirement to wear PPE in manufacturing areas. As part of this process, they put pressure on suppliers to reduce the noise from new machines to well below 80dB. As a result, the manufacturer consulted us to determine the options to reduce the noise from their updated range of machines.

In the case of the machine in question (several were potentially on order subject to noise level targets being met), the operator noise level for the standard machine was 90dB. Ranking the sources showed that the air suction system used to transport the tights and the high speed industrial sewing machine were the dominant sources. The former was modified by changing the geometry and designing a bespoke silencer element. Combined with a new sump guard design developed for the sewing machine, these reduced the overall noise by 8dB – down to 82dB at the operator.

These modifications cost only £250 on new machines, and yet they eliminated the requirement for mandatory PPE. In addition to the direct cost savings on PPE, there were also indirect savings associated with improved working conditions, communications and the reduced risk management resources.

Update 2013-04-09