PROTECTION FROM HAND-ARM TRANSMITTED VIBRATION USING ANTIVIBRATON GLOVES VLADO GOGLIA IGOR ĐUKIĆ JOSIP ŢGELA Abstrct There re vrious wys of reducing the helth-hzrds of hnd-trnsmitted vibrtion. One of the possible protective mesures is the use of the nti-vibrtion gloves, but their effectiveness is still subject to discussion nd mny experts re questioning it. The procedure for mesurement nd evlution of the vibrtion trnsmissibility of the nti-vibrtion gloves is given in ISO 10819-1996 nd EN ISO 10819-1996 s well s in the Ntionl Stndrd HRN ISO 10819-000. Due to the numerous objections on the testing procedure recommended by the bove stndrds mny reserchers prefer field- testing. In order to ssess the effectiveness of nti-vibrtion gloves of five different mnufctures the Fculty of Forestry University of Zgreb in co-opertion with the public enterprise Hrvtske šume Ltd. crried out fieldtesting. The pper reports on the testing results. Key words: ergonomics, vibrtion, nti-vibrtion gloves, mnufctures, mesurement. Clssifiction JEL: Z13 Economic Sociology 1. Introduction Exposure to vibrtion of higher intensity over longer period of time often cuses permnent helth dmges. Occuptionl deseses ply n importnt role in mny ctivities in forestr too. One of the numerous protective mesures tken ginst excessive exposure to hnd-rm trnsmitted vibrtion is the use of nti-vibrtion gloves. The ssessment of their effectiveness is complex procedure which doesn t lwys yeld expected results. As there is number of nti-vibrtion gloves vilble on the mrket, it is very responsible tsk to mke the right choice. According to the officil sttistics of the Crotin Stte Helth Institute vibrtion ccounted for 11.4 % of the overll number of occuptionl deseses between 1990 nd 1997 (Kocin, 1999). In order to ssess the effectiveness of nti-vibrtion gloves of five different mnufcturers the Fculty of Forestr University of Zgreb, in co-opertion with the public enterprise Hrvtske šume Ltd. crried out field testing.. Sensitivity of the hnd-rm system to vibrtion It is very well known tht prts of the humn orgnism hve different nturl frequences. Exposure to vibrtion the frequency chrcteristics of which re in resonnce with prt of humn body cn multiply the consequences, especilly in the cse of the hnd-rm system where vibrtion is directly trnsmitted to the body. It is lso known fct tht mximum sensitivity of the hnd-rm system lies in the frequency rnge from 6.3 to 16 Hz (Gogli, 1997). Beside frequency chrcteristics there re two more prmeters tht re importnt in predicting the hzrd rte of exposure to vibrtion: - vibrtion level or intensit nd - time of exposure. The rel vibrtion intensity should be weighted simultneosly tking into ccount frequency chrcteristics s well s vibrtion level. According to the ISO 5343-1001 recommendtions the vibrtion level in ll three co-ordinte xes schould bi noted in the vibrtion mesurement report. The weighted ccelertions should be counted in ccordnce with the Annex A of the sme stndrd using the following eqution:
h hw( x, z) ( Whihi) i1 where: W hi is the weighting fctor for the i-th one-third-octve bnd, nd hi is the r.m.s. ccelertion mesured int the i-th one-third-octve bnd, m/s. The evlution of the totl exposure to vibrtion trnsmitted to the hnd-rm system is defined s the root-sum-of-squre of the three component vlues: hv hwx hwy hwz The dily vibrtion exposure is expressed in terms of the eight-hour energy-equivlent frequency-weighted totl vibrtion vlue, A(8), s shown in the following eqution: A( 8) where: T is totl dily durtion of exposure to the vibrtion hv nd T 0 is the refernce durtion of 8 hours (8800 s). If the totl dly exposure to vibrtion consists of severl opertions with different vibrtion mgnitude, the dily vibrtion exposure, A (8), shll be obtined using the eqution: A( 8) 1 T hv N o i1 T T o hvi T where: hvi is totl vibrtion vlue fot the i-th opertion; n re number of individul vibrtion exposures, nd T i is durtion of the i-th opertion. 3. Reduction of the dily exposure to hnd-rm trnsmitted vibrtion The bove equtions show clerly tht there re three possibilities to reduce opertor's dily exposure to hnd-rm trnsmitted vibrtion: ) by orgnizing the work-site s to combine the different ctivities during the work d b) by reducing the exposure time, c) by dmping the vibrtion, prticulrly in the frequency rnge in which the hnd-rm system is most sensitive. All three possibilities re used in prctice. This rticle discusses the possibility of reducing the exposure to the hnd-rm trnsmitted vibrtion by dmping. The use of nti-vibrtion gloves is suggested to opertors exposed to higher levels of vibrtion, but it hs to be pointed out tht mny reserchers nd scientists re scepticl towrds the their effectiveness (Koton, 00). Wht type of gloves shoulod be used hs been discussed for yers. The choice of the best nti-vibrtion gloves is not esy. There re mny mnufcturers who offer nti-vibrtion gloves mde of vrious mterils for vibrtion dmping, which mkes the dmping efficiency of nti-vibrtion gloves necessry. In our opinion, the best wy to define the dmping chrcteristics of the ntivibrtion gloves is to test them in rel work-site conditions. 4. Mesuring method nd mesuring equipment The vibrtion level ws t first mesured on the opertor s grip hndle of the motor chin sw in ll three directions t 3 different working conditions: i
- t idling, - t full lod, nd - t mximum rottionl frequency. After tht, the vibrtion level on opertor s hnd ws mesured in ll three xes simultneously t the sme three working codnitions. The nti-vibrtion gloves were plced between the grip hndle nd the opertor s hnd. The dmping chrcteristics of the ntivibrtion gloves cn be expressed in verious wys: 1) By the rtio between the weighted ccelertion sum mesured on the grip hndle nd the ones mesured directly on the opertor s hnd: p WAS WAS where: α p is dmping fctor expected to be < 1; WAS 1 is weighted ccelertiion sum on the grip hndle, m/s, nd WAS is weighted ccelertiion sum on the opertor s hnd, m/s ) The dmping cn be xpressed lso by the rtio between the weighted ccelertions in different directions on the grip hndle nd the opertor's hs s follows: x, z 1 hwx, z hwx, z1 where: α x,z is dmping fctors in the prticulr directions expected to be < 1; α hwx,z1 is weighted ccelertion in specific direction ont he grip hndle, m/s ; α hwx,z is the sme on the opertor's hnd, m/s. 3) For detiled dmping chrcteristics ot the prticulr nti-vibrtion gloves the frequency chrcteristics of the vibrtion level on the grip hndle nd the opertor s hnd cn be clculted. A specil holder for the threexil ccelerometer hs been designed for these mesurements. The threexil ccelerometer with holder is shown in Fig. 1. As it ws mentioned before, the mesurements were first crried out on the grip hndle in ll three co-ordinte xes simultneously nd t three operting conditions. Figure 1: Threexil ccelerometer with the holder
The sme ws then repeted on the opertor s hnd. The threexil ccelerometer ws positioned in ccordnce with the ISO 875 1985 recommendtions. A mesuring chin s shown in Fig. ws used for the mesurements. For ech working codition severl smples were used. The verging times during nlysis wre tken in ccordnce with the bove recommendtions. Figure : Shemtic representtion of the mesuring chin 5. Mesurement nd mesurement results In ccordnce with the ISO 7505 fresh beech-prism ws cut for the mesurement. For ech of the three xes in ll three working conditions the vlues of weighted ccelertions were clculted. Then the WAS-vlues (weighted ccelertion sum) were clculted. The velues for ll three xes s well swas-vlues re grphiclly represented in digrms in Fig. 3 6. From Fig. 3 it is cler tht during idling only one type of nti-vibrtion gloves hve shown reltively good dmping chrcteristics, two types hve shown negligible dmping chrcteristics nd the lst two tested types hve shown unexpected chrcteristics: the vibrtion levels were incresed. The tested gloves hve shown similr chrcteristics in WAS-vlues s well s in prticulr xes. Figure 3: Grphicl representtion of the weighted ccelertion in ll three single xis nd the WAS vlues t idling At mximum rottionl frequency the nti-vibrtion gloves hve shown significntly better dmping chrcteristics. The WAS-vlue is shown in Fig. 4. From the five tested types of ntivibrtion gloves four hve shown good dmping chrcteristics. These results correspond to the
results obtined in some independent reserches of this problem. It hs been known lredy tht the most nti-vibrtion gloves show good dmping chrcteristics t higher frequencies only. Figure 4: Grphicl representtion of the weighted ccelertion in ll three single xis nd the WAS vlues t full lod Fig. 5 shows the weighted vibrtion level in ll three co-ordinte xes s well s the WASvlue t cutting. It is evident tht only one type of the tested nti-vibrtion gloves hs shown good dmping chrcteristics. Two types hve shown wek nd two types negligible dmping chrcteristics. Figure 5: Grphicl representtion of the weighted ccelertion in ll three single xis nd the WAS vlues t cutting The cumultive representtion of the WAS-vlues for ll three cutting conditions is shown in Fig. 6. It shows clerly tht compred to the vibrtion level obtined by mesurements on the grip hndle, the use of nti-vibrtion gloves mkes negligible difference. The differences re so smll, tht they might s well be the consequence of the mesuring error. On the other hnd, the sme figure shows lso tht during mximum rottionl frequency ll types of the nti-vibrtion gloves tested show good dmping chrcteristics. One type of nti-vibrtion gloves hs shown prticulrly good dmping chrcteristics. It hs to be pointed out tht two types of nti-vibrtion gloves hve shown totlly unexpected dmping chrcteristics t idling. Their dmping fctors were greter thn 1, which mens tht the vibrtion level increses t idling when using these types of nti-vibrtion gloves.
Figure 6: Cummultive representtion of the WAS vlues 6. Conclusion The mesurement hve shown tht there re significnt diferences in dmping chrecteristics between deferent tzpes of nti-vibrtion gloves. At idling some of nti-vibrtion gloves hve shown completely unexpected chrecteristics. During idling only one type of ntivibrtion gloves hve shown reltively good dmping chrcteristics, two types hve shown negligible dmping chrcteristics nd the lst two tested types hve shown unexpected chrcteristics: the vibrtion levels were incresed. The tested gloves hve shown similr chrcteristics in WAS-vlues s well s in prticulr xes. At mximum rottionl frequency the nti-vibrtion gloves hve shown significntly better dmping chrcteristics. From the five tested types of nti-vibrtion gloves four hve shown good dmping chrcteristics. At cutting it is evident tht only one type of the tested nti-vibrtion gloves hs shown good dmping chrcteristics. Two types hve shown wek nd two types negligible dmping chrcteristics. These results correspond to the results obtined in some independent reserches of this problem. References: [1] DONG, R. G. WELCOME, D. E. McDOWELL, T. W. WU, Y. Z.: Mesurement of biodynmic response of humn Hnd-rm system. Journl of Sound nd Vibrtion, 006, 94, p. 807 87. ISSN 00-460X [] DONG, R. G. McDOWELL, T. W. WELKOME, D. E. SMUTZ, W. P. SCHOPPER, A. W. WARREN, C. WU, J. Z. RAKHEJA, S.: On-the hnd mesurement methods for ssessing effectiveness of nti-vibrtion gloves. Interntionl Journl of Industril Ergonomics, 003, 3, p. 83 98. ISSN 0169-8141 [3] GOGLIA, V.: Ergonomske znčjke šumrske mehnizcije problemi njihov mjerenj i vrednovnj. Mehnizcij šumrstv, 1997, (4), p. 09 17. ISSN 035-5406 [4] GOGLIA, V. GOSPODARIĆ, Z. BELJO, R. ĐUKIĆ, I. KOVAĈEV, I.: Izloženost vozč mlog poljoprivrednog trktor vibrcijm. Zbornik rdov Actul tsks on griculturl engineering. 004. Optij. ISSN 1333-651 [5] GRIFFN, M. J.: Evluting the effectiveness of gloves in reducing the hzrds of hndtrnsmitted vibrtion. Ocuptionl nd Environmentl Medicine, 1998, 55, p. 340 348. ISSN 1351-0711 [6] HEWITT, S. Assessing the performnce of nti-vibrtion gloves possible lterntive to ISO 10891-1996. Annls of Occuptionl Hygiene, 1998, 4, p. 45 5. ISSN 0003-4878 [7] KACIAN, N.: Occuptionl diseses in Croti. Work nd Sfety 1999, 3 (1), p. 83 89. ISSN 035-3675
[8] KOTON, J: Prevention of hnd-rm vibrtion syndrome by using ntivibrtion gloves. Medycyn Prc 00, 53, p. 43 431. ISSN 0465-5893 [9] REYNOLDS, D. D. WOLF, E.: Evlution of ntivibrtion gloves test protocols ssocited with the revision of ISO 10819. Industril Helth, 005, 43, p. 556 565. ISSN 0019-8366 [10] SUCHOMEL, J. SLANĈÍK, M.: Influence of some ergonomic criterims on modelling nd optimiztion technology in forestry. In: Proceedings of the Interntionl Conference Mngement of Humn Potentil in Compny. Ţilin. University of Ţilin. 005, p. 354 359. ISBN 80-8070-360-4 [11] WARREN, C. WU, J. Z. RAKHEJA, S.: On-the hnd mesurement methods for ssessing effectiveness of nti-vibrtion gloves. Interntionl Journl of Industril Ergonomics, 003, 3, p. 83 98. Address of uthors: Prof.dr.sc.dr.h.c. Vldo GOGLIA Mr.sc. Igor ĐUKIĆ Fculty of Forestry Fculty of Forestry University of Zgreb University of Zgreb Svetošimunsk 5 Svetošimunsk 5 10 000 Zgreb 10 000 Zgreb Croti Croti e-mil: gogli@sumfk.hr e-mil: i_dukic@yhoo.com Mr.sp. Josip ŢGELA Public Enterprise Hrvtske Šume, Ltd. Vukotinović 10000 Zgreb Croti e-mil: josip.zgel@hrsume.hr