The noise emissions from circular saws endanger the hearing of the employees in wood, metal, stone and plastics working businesses. The noise exposure can be reduced substantially by the use of low-noise circular saw blades. Since the low-noise circular saw blades available on the market have not as yet been adopted on a large scale by companies, the BG expert committee Wood proposed that a project be conducted for indentification of the scope for use of low-noise saw blades and the attainable noise reduction. The results were to be resumed in a Noise-Reduction Manual suitable for practical application.
In the first phase of the project, surveys were conducted on the Internet, in trade directories and through trade associations (such as the VDS, the Verein Deutscher Schleifmittelwerke e. V.), in order to obtain as comprehensive an overview as possible of the offers of manufacturers and suppliers of low-noise saw blades for the various materials. The available low-noise saw blades were classified according to external characteristics (e.g. sandwich type, laser-cut, etc.). At least two examples of each available type were then selected and obtained for each material group. The smallest saw blade sizes generally used professionally in fixed application were then selected for the laboratory tests. These saw blades had a diameter of 250 mm for wood, aluminium and plastics cutting, and of 350 mm for stone cutting. The second phase of the project involved performance of the laboratory tests and two in-plant measurements. Typical wood types were selected on the basis of preliminary tests for the wood-cutting tests. The measurements were performed on blockboard, chipboard and medium-density fibreboard, and also on squared beech and sawn meranti timber. A range of casement sections and FOREX panels were selected for plastics cutting. Aluminium extrusions (system profiles and tubes) were selected for all aluminium cutting tests. For stone cutting, measurements were taken with eight different materials, including granite, marble, slate and basalt.
Evaluation of the information gathered during the surveys revealed a total of 40 companies offering low-noise saw blades. The range can be classified for the various materials as follows:
wood cutting - 16 companies;
aluminium cutting - 6 companies;
plastics cutting - 6 companies;
stone cutting - 24 companies.
The noise radiated by the saw blade during sawing on stationary circular saws was found to be clearly greater than the noise from the drive and dust exhaust (or water jet in the case of stone sawing). The use of low-noise saw blades thus permits considerable attenuation of the sound level. Since conventional saw blades from various manufacturers differ considerably in the radiated noise, the attainable noise reduction exhibits a correspondingly wide scatter, however. The following sound level attenuation values were measured during laboratory testing for the various material classes: wood cutting, 1 to 12 dB(A); plastics cutting, 1 to 11 dB(A); aluminium cutting, 2 to 6 dB(A); stone cutting, 3 to 16 dB(A). Saw blades, suitable for the available table saws, with a diameter of 300 mm were employed for the in-plant measurements. During wood cutting, a sound level attenuation of between 1 and 7 dB(A) was measured. The results show that the saw blade must be selected carefully in order for the best attenuation in sound level to be reached. For stone cutting and for aluminium and plastic cutting, the sandwich-type blades should be given clear preference over other saw blade types, owing to their substantially higher sound level attenuation.
-cross sectoral-Type of hazard:
Lärm, Arbeitsmittel, MaschinensicherheitDescription, key words:
noise reduction, circular saws, low-noise saw blades, wood working, metal working, stone working, plastics working