Chainsaws have to be certified before their commercialisation, as other agricultural and forestry machineries, because of the European Directive 98/73. The introduction of this Directive made compulsory the international standards to define noise and vibration methods to certify machineries: there are standards to permit the machinery design (CEN Report 1030-1, 1995) and to measure the emitted values (ISO 7505, 1985, for vibration and ISO 7182, 1989 for pressure acoustic data). Therefore, there are standards to verify the validity of the manufacturers' data declaration during the certification phase (EN 12096: 1997, for vibration and EN ISO 4871, 1998 for acoustic). At the beginning, we have used the standards ISO 7182 and ISO 7505 to evaluate the acoustic pressure and vibration levels bear by the woodcutters, using 13 chainsaws of different models, typically utilised in the forestry yards. Also if all the procedures indicated by standards have been followed, floating results have been obtained for almost all the machines, both for noise and vibration data: this fact has demonstrated how is difficult to recorder such information to obtain a good repeatability. Concerning acoustic parameters, the main factors which influence the data spread are chiefly connected to the different position of the microphone used for the measurement with the used log, that is the distance and the angle between the microphone and the log used for test and, last but not least, to the presence of the operator or, better, to his behaviour, to his physique, and to the garment type he wears, which lead to a high spread of the data (ISO TC 23/SC 17, 1994). Concerning vibration, because of lacking of a precise and exhaustive method to refer to, the operators are favourable to follow procedures connected to their experience and, also if they stay inside of the requests of the standard, they unlikely produce comparable data, because the human behaviour is not standardized (Gillmeister and Shenk, 1999). To face these problems, technical committees work to the production of standards to make the measurements results more reliable to let them to be compared. Tests proposed in these new standards use, when it is possible, artificial processes applied to the working machineries conditions without both the operator and the material normally used (Calvo et al., 2004). For this reason we have done a second work, where we have compared and then verified noise and vibration levels caused by 3 chainsaws using the current standards ISO 7182, ISO 7505 and the draft ones ISO/DIS 22868: 2003 and ISO/CD 22867: 2003. To carry out the tests we used the same parameters, criteria and instruments both with the current and draft standards (the ISO/DIS 22868 and ISO/CD 22867 have been approved in December 2003 and now they are circulating for the final vote as FDIS). More in detail, concerning the draft proposal ISO/DIS 22868, for the noise analysis the test procedure demands the operator absence, substituting him with an artificial device. The draft proposal ISO/CD 22867 still uses the operator for vibration tests, but requires an higher results repeatability, controlling the data standard deviation.
Current normative and draft proposals to compare noise and vibration data in chainsaws: a study to test the results repeatability
Deboli R
2004
Abstract
Chainsaws have to be certified before their commercialisation, as other agricultural and forestry machineries, because of the European Directive 98/73. The introduction of this Directive made compulsory the international standards to define noise and vibration methods to certify machineries: there are standards to permit the machinery design (CEN Report 1030-1, 1995) and to measure the emitted values (ISO 7505, 1985, for vibration and ISO 7182, 1989 for pressure acoustic data). Therefore, there are standards to verify the validity of the manufacturers' data declaration during the certification phase (EN 12096: 1997, for vibration and EN ISO 4871, 1998 for acoustic). At the beginning, we have used the standards ISO 7182 and ISO 7505 to evaluate the acoustic pressure and vibration levels bear by the woodcutters, using 13 chainsaws of different models, typically utilised in the forestry yards. Also if all the procedures indicated by standards have been followed, floating results have been obtained for almost all the machines, both for noise and vibration data: this fact has demonstrated how is difficult to recorder such information to obtain a good repeatability. Concerning acoustic parameters, the main factors which influence the data spread are chiefly connected to the different position of the microphone used for the measurement with the used log, that is the distance and the angle between the microphone and the log used for test and, last but not least, to the presence of the operator or, better, to his behaviour, to his physique, and to the garment type he wears, which lead to a high spread of the data (ISO TC 23/SC 17, 1994). Concerning vibration, because of lacking of a precise and exhaustive method to refer to, the operators are favourable to follow procedures connected to their experience and, also if they stay inside of the requests of the standard, they unlikely produce comparable data, because the human behaviour is not standardized (Gillmeister and Shenk, 1999). To face these problems, technical committees work to the production of standards to make the measurements results more reliable to let them to be compared. Tests proposed in these new standards use, when it is possible, artificial processes applied to the working machineries conditions without both the operator and the material normally used (Calvo et al., 2004). For this reason we have done a second work, where we have compared and then verified noise and vibration levels caused by 3 chainsaws using the current standards ISO 7182, ISO 7505 and the draft ones ISO/DIS 22868: 2003 and ISO/CD 22867: 2003. To carry out the tests we used the same parameters, criteria and instruments both with the current and draft standards (the ISO/DIS 22868 and ISO/CD 22867 have been approved in December 2003 and now they are circulating for the final vote as FDIS). More in detail, concerning the draft proposal ISO/DIS 22868, for the noise analysis the test procedure demands the operator absence, substituting him with an artificial device. The draft proposal ISO/CD 22867 still uses the operator for vibration tests, but requires an higher results repeatability, controlling the data standard deviation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
