Ergonomic evaluation of a commonly used power tiller in Thailand | |
| Author | Dian Utanti Mamansari |
| Call Number | AIT Diss. no.AE-98-01 |
| Subject(s) | Agricultural machinery--Thailand Human engineering |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | Power tillers and small tractors are still the most important machines in modern Thai agriculture. currently, almost a million units of power tillers are in active use in Thai agriculture. It suits both the economical and physical conditions associated with rece production. Contrary to the economical and technical advantages, power tillers have some disadvantages from the operator's point of view. Controlling while walking behind this machine is often a hard work. Safety and health concerns associated with the use of this machine in Thailand have not been well documented. Apart for these facts, there are unofficial reports of other health hazards while using power tillers. Considering that the power tillers have been and will continue to be used by farmers in Thailand, it was planned to conduct and ergonomic evaluation of the most commonly used power tiller in Thailand. The main objective of this study was to conduct detailed assessment of the power tiller from an ergonomic point of view. the specific objectives were; to study the utilization of power tillers in Thailand; to conduct vibration and sound level measurements and assess the physiological responses of the operator; to identify the human-machine-environment relationship during the power tiller utilization; and give recommendations for the improvement of the design of power tillers from the ergonomics point of view. In order to understand the operational features of the machines and equipment, the rice cultivation practices in selected parts of the central plain of Thailand, where the power tillers are generally used throughout the year, were studied. Among various models of power tillers used, the Siam Kubota power tiller was found to be the most popular among the farmers surveyed. The survey revealed that all the power tiller operators were male, most of them were the owners and the rest were hired labor. As a full time farmer, working 8-11 hours per day in the field was the daily routine throughout the years of farming. Seventy-seven percent of them had an average education of primary school level four. Economically, farmers tend to accept power tillers due to its lower price compared to big tractors and lower maintenance cost compared to animals. Technically, as farmers consider the main task of a power tiller is tillage, speed of work for this activity is needed. On-road accidents during transportation using power tillers were experienced by 52% of the respondents. For water pumping, power tillers are used for about 8-24 hours per day. Temporary threshold shift of hearing was experienced by 70% of the respondents due to power tiller nose. Although permanent hearing impairment was not found among the farmers surveyed, uneasiness during operation combined with vibration through the hand-arm system was recorded. All respondents companied about at wrist, lower-arm, upper-arm and shoulder, although 95% of power tillers owned by farmers have a steering clutch which is supposed to ease the operation by reduction some muscle power applied especially during the turning. The widely used power tiller, Siam Kubota 8.14 kW model ET110, was used for an ergonomic evaluation. The vibration level was increase with an increase of engine speed up to 2000 and 1600 rpm in the stationary and transport mode, respectively, Vertical vibration was significantly higher in the tip of handle, which had direct contact with the operator hand-arm system. The vibration accelerations exceed the ISO standard for less than 30 minutes vibration exposure time. The average sound at the points where the operator is supposed to stand was 90 dB at the engine speed of 2200 rpm on concrete, asphalt and soil surfaces. On the grass surface, the sound levels were below the recommended standard of 90dB for a noise exposure level of 8 h duration. During fieldwork, it was revealed that the sound level exceeded 90dB at an engine speed of more than 1400 rpm during all operations. The main source of sound was the engine, which is only partly covered and cannot attenuate the noise. The Physical work capacity of the power tiller operator was tested. Estimating the physical work capacity was possible by using the equation of heart rate and PWC. Field tests were conducted to observe the performance of the machine and to determine the man-machine relationship. It could be concluded that the excessive physiological response experienced by power tiller operators come from two sources, environmental and power tiller itself. Working with power tiller in a hot humid environment, which also changes throughout the working day, might be responsible for the excessive workload, Surface conditions of the agricultural field were another factor contributing to workload on the operator. The energy cost for wetland operation was found to be mainly due to the soil condition. Based on the results obtained, a few suggestions could be given to improve working with the power tiller from an ergonomic point of view. Attaching a seat behind the power tiller might be the way to reduce energy cost due to walking in the field. The proper way of attaching a seat has to be considered to avoid shifting energy due to walking and maintaining maneuverability of the power tiller during operation. Covering the engine propel will reduce the noise level. It has to be done without reducing the ease of engine maintenance. The modification of muffler design would help reduce the noise. The handle, which has the highest vibration compared to the other parts, is attached to the main chassis only at one end. Additional connection using rigid material to the main chassis without adding excess weight to the power tiller may reduce the handle vibration. Tightening the engine to the chassis using vibration isolator will reduce the vibrations transmitted by the engine. For this the case, of handling has to be considered as farmers frequently disengage the engine from the chassis for other purposes. |
| Year | 1998 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Salokhe, V.M.; |
| Examination Committee(s) | Gee-Clough, D.;Kitti Intaranont;Nitin, Afzulpurkar;Hoki, Makoto; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology |