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A little about noise emissions and some sound advice

13 November 2015

Justin Leonard reviews the latest polymer energy chain technologies, which are enabling machines to operate more smoothly and quietly.

In a production environment noise is a concern not just for the operator but the effects that attendant vibration can have on the quality of the work being carried out. Energy chains and cable management systems are one of many sources of vibration and noise, and although not a major contributor, if a machine builder needs to reduce the levels by a few per cent to comply with the Machinery Directive, then the energy chain could make all the difference.

Noise is an important issue in a plant, and machinery must be designed and constructed so that any risks resulting from the emission of airborne noise are reduced to their lowest level. There are two different types of measurement – sound pressure and sound power. Sound pressure is essentially how loud the sound appears to the ear and the measurements are weighted to simulate the hearing response of the ear –a reduction of 3dB(A) sounds like a 50 percent reduction in the noise level to the human ear. However, sound power is the total amount of sound energy that the equipment radiates into the environment and remains non-weighted.

The European Machinery Directive 2006/42/EC requires measurement and declaration of A-weighted sound pressure at workstations where this exceeds 70 dB(A) (where this level does not exceed 70dB(A), this fact must be indicated). Where this A-weighted level exceeds 80dB(A), sound power must also be measured and declared. A value for peak C-weighted instantaneous sound pressure value at workstations must also be declared where this exceeds 63Pa (130dB in relation to 20µPa).

A recent NOMAD project, which was run by the EU to look at the reporting of noise emission in user instructions of machinery and equipment, found that a staggering 80 percent of the manuals did not conform to the requirements of the Machinery Directive - this was either because the noise information required was missing, not credible or unsuitably reported.  The project was conducted on about 1,500 machines in 40 equipment families from 800 manufacturers.

Machinery must be designed and constructed so that any risks resulting from the emission of airborne noise are reduced to their lowest level. Energy chains are often overlooked as a source of noise and, in addition to the energy chain itself, the running surface, the dynamics and the cable and hose package play a vital role in overall noise generation. 

Conventional energy chains use a pin and bore connection system, which allows relative movement between the joints. However, in recent years, noise optimised e-chains have been developed that replace the conventional pin and bore connection with an abrasion resistant spring element. 

By installing high quality, quiet energy chains and flexible cables and hoses, machine builders can reduce noise levels significantly and benefit from providing a comprehensive noise emission declaration, according to the Machinery Directive, while enabling the purchaser to select quieter machines. 

Justin Leonard is a director at igus UK

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