An ergonomic risks assessment for manual and motor-manual pruning

Sibiya, Zimbili Bonisiwe (2020-03)

Thesis (MScFor)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Mechanisation and modernisation in pruning operations for South Africa's forestry industry have advanced to keep abreast with best practices internationally. Commercially planted pine species in South Africa are not self-pruning, therefore, pruning activities are done extensively to produce clear wood and for fire protection or accessibility purposes. Although traditional handheld pruning tools have been used for decades, motor-manual pruning saws have recently been introduced to South African pruning operations. This has, however, raised the question what the ergonomic risks in manual and motor-manual pruning operations potentially expose workers to. Therefore, the study aimed to assess ergonomic risks that may be associated with the manual and motor-manual pruning operations of Pinus patula stands in Kwa-Zulu Natal (KZN), Midlands at 3.5 m and 2.0 m pruning lifts. Convenience sampling of seven pruners was done to collect data on productivity (time study), workload (heart rate indices and productive heart rate), awkward postures (captured images during pruning operations) and body discomfort rating (Nordic Musculoskeletal map and the Likert scale) for ergonomic risks assessment. Statistica 64 and Excel functions were used to test for significant interactions between pruning method, pruning lift and worker and Games-Howell posthoc test for significant differences between the means of operations at a statistically significant level of 5.0 %. Awkward postures were assessed for deviation from the neutral plane of body posture. Body discomfort was analysed with Fisher’s exact test for prevalence of discomfort per recording period, frequency of discomfort rating and discomfort per body part for each pruning operation. Machine utilisation was considered the same as the duration of exposure to operation due to the nature of the operation requiring availability of operator and machine to be executed successfully. Results show that the interaction between the pruning lift, pruning method and pruner was significant for productivity, productive heart rate and body discomfort responses. Time study results showed that motor-manual (MM) operations produced the highest productivity compared to the manual (M) operations; however, the manual operations were the most efficient. Pruning operations fell under the “medium to heavy” workload classification with mean heart rates at work of 115, 113, 110 and 119 beats per min (beats.min-1), for 2.0 m M, 2.0 m MM, 3.5 m M and 3.5 m MM respectively. Common postures adopted by workers were the shoulder and elbow abduction and extension, twisting and neck extension, ulnar deviation and bending of the back. High prevalence of discomfort was reported for manual (55 %) operations compared to MM (49 %) and 2.0 m pruning lift (61 %) and 3.5 m pruning lift (42 %). Pruning operations were rated as severe discomfort except for 3.5 m MM, which was rated as moderate discomfort. Some of the postures adopted by workers must be adjusted to avoid future health problems, such as high flexion of the back in the 2.0 m M and MM operations with a high prevalence of discomfort reported. Additionally, the duration of exposure to the operation and the repetitive nature of pruning operations are additional ergonomic risks identified in this study. These results show promise as the first steps in investigating the effect of M and MM operations on Ergonomic and productivity of operations. However, it is recommended for this study to be repeated with a larger sample and with gender as an additional factor because that is much more thorough representation of the current pruning operation teams. Additionally, a thorough focus on musculoskeletal disorder since many workers have been in the field for several years.

AFRIKAANSE OPSOMMING: Meganisasie en modernisering van snoeibedrywighede vir die bosboubedryf in Suid-Afrika is gevorder om op hoogte te bly met die beste praktyke internasionaal. Kommersiële aangeplante dennespesies in Suid-Afrika snoei nie vanself nie; daarom word snoeiaktiwiteite breedvoerig gedoen om helder hout te produseer, en vir brandbeskerming of toeganklikheid. Alhoewel tradisionele hand-en-snoei-instrumente al dekades gebruik word, is motorsnoei-saag onlangs aan Suid-Afrikaanse snoeibedrywighede bekendgestel. Dit het egter die vraag laat ontstaan waartoe die ergonomiese risiko-handleiding en motorhandmatige snoeiwerk werkers moontlik blootstel. Daarom is die studie gemik op die bepaling van ergonomiese risiko's wat verband hou met die hand- en motorhandmatige snoeibewerkings van Pinus patula bos in Kwa-Zulu Natal (KZN), Midlands op 3.5 m en 2.0 m snoeihysbakke. Gemakste steekproefneming van sewe snoeiers was gedoen om data oor produktiwiteit (tydstudie), werklading (hartslagindeks en produktiewe hartklop), ongemaklike posture (vasgelegde beelde tydens snoeioperasies) en liggaamsgemakstemming (Nordiese muskuloskeletale kaart en Likert-skaal) te versamel vir assessering van ergonomiese risiko's. Statistica 64 en Excel-funksies was gebruik om te toets vir beduidende interaksies tussen snoeimetode, snoeigraaf en werker, en Games-Howell posthoc-toets vir beduidende verskille tussen die bedieningsmetodes op 'n statisties beduidende vlak van 5.0 %. Ongemaklike houdings is beoordeel as afwyking van die neutrale vlak van liggaamshouding. Liggaamsongemak is geanaliseer met Fisher se presiese toets vir die voorkoms van ongemak per opnameperiode, frekwensie van ongemak-gradering en ongemak per liggaamsdeel vir elke snoeibedrywigheid. Die doeltreffendheid van die masjien word dieselfde beskou as die duur van die blootstelling aan die gebruik as gevolg van die aard van die werking wat die beskikbaarheid van die bestuurder en die masjien suksesvol moes uitvoer. Resultate toon dat die interaksie tussen die snoeihef, die snoeimetode en snoeier betekenisvol was vir produktiwiteit, produktiewe hartklop en reaksies op liggaamsongemak. Resultate van die tydstudie het getoon dat motorhandleiding (MM) bedrywighede die hoogste produktiwiteit opgelewer het in vergelyking met die handleiding (M) bewerkings; die handbedrywighede was egter die doeltreffendste. Snoei-operasies val onder die gemiddelde tot swaar werklasklassifikasie met gemiddelde werkshartklop van 115, 113, 110 en 119 slae per minuut (slae.min-1), vir 2.0 m M, 2.0 m MM, 3.5 m M, en 3.5 m MM onderskeidelik. 'n Algemene liggaamshouding wat deur werkers aangeneem is, was die ontvoering en verlenging van die skouer en elmboog, draai en nekverlenging, afwyking van die ulna en buigingvan die rug. 'n Groot voorkoms van ongemak was gerapporteer by handmatige (M) (55%) operasies in vergelyking met MM (49%), en 2.0 m snoeihef (61%) en 3.5 m snoeihef (42%). Snoeibedrywighede is as ernstige ongemak beskou, behalwe vir 3.5 m MM, wat as matige ongemak beskou is. Sommige van die houdinge wat deur die werkers aangeneem was, moet aangepas word om toekomstige gesondheidsprobleme te vermy, soos hoë buiging van die rug in die 2.0 m M- en MM-bedrywighede, met 'n hoë voorkoms van ongemak wat aangemeld is. Boonop is die duur van die blootstelling aan die bedrywigheid en die herhalende aard van die snoeiobedrywighede addisionele ergonomiese risiko's is wat in hierdie studie geïdentifiseer was. Hierdie resultate toon belofte as die eerste stappe in die ondersoek na die effek van M- en MM-bewerkings op die ergonomiese risiko’s en produktiwiteit van snoeibedrywighede. Dit word egter aanbeveel dat hierdie studie herhaal word met 'n groter steekproef en met geslag as 'n addisionele faktor want dit is 'n baie deeglike weergawe van die huidige snoei-operasiespanne. Daarbenewens is daar 'n deeglike fokus op muskuloskeletale versteurings, aangesien baie van die werkers al 'n paar jare in die veld was.

Isifinyezo: Ukusebenza ngomshini nokwenziwa kwemisebenzi ngesimanje emisebenzini yokuthena embonini yamahlathi yaseNingizimu Afrika sekuthuthukile ukuze kuqhubeke kuhlangane ngemikhuba emihle emhlabeni jikelele. Izinhlobo zikaphayini ezitshalelwe ukuthengiswa eNingizimu Afrika azizitheni. Ngakho-ke, imisebenzi yokuthena yenziwa kakhulu ukukhiqiza izinkuni ezinhle, kanye nezinjongo zokuvikela umlilo noma kungeneke kalula ehlathini. Yize kusetshenziswe amathuluzi endabuko okuphathwa ngesandla amashumi eminyaka, amasu okuthenga izithuthuthu asanda kwethulwa emisebenzini yokuthena yaseNingizimu Afrika. Lokhu-ke, kuphakamise umbuzo wokuthi yimiphi imisebenzi yezandla yokuphehlwa kwe-ergonomic kanye ne-motor-manual (MM) engase ichithe abasebenzi kuyo. Ngakho-ke, lolu cwaningo luhlose ukuhlola ubungozi beergonomic obungase buhlotshaniswe nomsebenzi wokuthena izihlahla ze-Pinus patula KwaZulu Natal (KZN), Midlands ngamamitha ayi-3.5 m kanye no-2.0 m. Ukwenza isampula yokuqongelela, abasebenzi abayisikhombisa abavele bekhona, kwenziwa ukuqoqa idatha ekukhiqizeni (ngesikhathi sesifundo), umthamo womsebenzi (ukushisa kwenhliziyo kanye nenhliziyo ekhiqizayo), ukuma okungahambi kahle (izithombe ezithwetshuliwe ngesikhathi somsebenzi), isilinganiso sokungakhululeki komzimba (Imephu yeNordic Musculoskeletal kanye nesikali se-Likert) ukuhlolwa kwezingozi ze-ergonomic. I-Stistica 64 ne-Excel imisebenzi esetshenziselwe ukuhlola ukusebenzisana okuhle phakathi kwendlela yokuthena izihlahla, ukuphakamisa izihlahla kanye nomsebenzi, kanye nokuhlolwa kwe-GamesHowell posthoc ngomehluko omkhulu phakathi kwezindlela zokusebenza ngezinga eliphakeme ngokwezibalo ze-5.0 %. Ukuhlolwa okungahambi kahle kuhlolwe ukuze kuhlukaniswe ukuma komzimba okungathathi hlangothi. Ukungaphatheki kahle komzimba kwahlazinywa ngokuhlolwa okuqondile kukaFisher kokuthola ukungathandeki ngesikhathi ngasinye sokurekhoda, imvamisa yesilinganiso sokungaphatheki kahle, kanye nokungaphatheki kahle kwengxenye yomzimba womuntu ngamunye emsebenzini wokuthena. Ukusebenza kahle komshini kubhekwe kufana nesikhathi sokuchayeka ekusebenzeni ngenxa yohlobo lomsebenzi oludinga ukutholakala komsebenzi nomshini ukuthi wenziwe ngempumelelo. Imiphumela ikhombisa ukuthi ukuxhumana phakathi kwephini yokuthena izihlahla, indlela yokuthena izihlahla kanye nomsebenzi kwakubalulekile ekukhiqizeni, ukushaya kwenhliziyo nokukhiqiza izimpendulo zokungakhululeki komzimba. Imiphumela yokutadisha isikhathi ikhombisa ukuthi ukusebenza kwe-motor-manual (MM) kukhiqize umkhiqizo ongcono kakhulu uma kuqhathaniswa nokusebenza kwemanuwali (M); kepha imisebenzi yezandla ibisebenza kahle kakhulu. Umsebenzi wokuthena wawela ngaphansi kokuhlukaniswa komthwalo osindayo kuya kwesilinganiso senhliziyo emsebenzini we-115, 113, 110 no-119 ukushaywa ngeminithi ngalinye (beats.min-1), ku-2.0 m M, 2.0 m MM, 3.5 m M, no-3.5 m MM ngokulandelana. Ukuma okujwayelekile okwamukelwa ngabasebenzi kwakungukuhlatshwa kwehlombe nokuwela, nokunwebeka, ukusontelana nokunwetshwa kwentamo, ukuphambuka kwe-ulnar nokugoba kweqolo. Kubikwe ukuthi kunenkinga enkulu yokungakhululeki komzimba kahle ngokusebenza kwezandla (55%) makukuqhathaniswa neMM (49%), kanye noluthena okuphakanyiswe amamitha awu-2.0 m (61%) nakuma mitha awu-3.5 m (42%). Umsebenzi wokuthena ulinganiswe njengobunzima obukhulu ngaphandle kwe-3.5 m MM, okulinganiswe njengokungahambi kahle okulinganiselwe. Ezinye zezinto ezimiselwe ukusetshenziswa kumele zilungiswe ukuze kugwenywe izinkinga zempilo zesikhathi esizayo, njengokuguquguquka okuphezulu komhlane ekusebenzeni kwe-2.0 m M ne-MM ngobunzima obukhulu bokuxhamazeka okubikiwe. Ngaphezu kwalokho, isikhathi sokuchayeka ekusebenzeni kanye nemvelo ephindaphindekayo yokusebenza ukuthena ziyingozi eyengeziwe ye-ergonomic ekhonjwe kulolu cwaningo. Le miphumela ikhombisa ukuthembisa njengezinyathelo zokuqala zokuphenya imiphumela yokusebenza kwe-M ne-MM ku-Ergonomic nokukhiqizwa kwemisebenzi. Kodwa-ke, kunconyelwe ukuthi lolu cwaningo luphinde luphindwe ngesampula enkulu kanye nobulili njengenye into eyengeziwe ngoba lokho kuvezwa ngokuphelele kwamaqembu wokusebenza kokuthena kwamanje. Ngaphezu kwalokho, ukugxila ngokuphelele ekuphazamisekeni kwesifo semusculoskeletal njengoba abasebenzi abaningi baneminyaka eminingi benza lomsebenzi.

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