Ergonomic evaluation of conventional agricultural sprayers with respect to human performance

Transcription

1 Agric. Sci. Digest., 36 (3) 2016: Print ISSN: X / Online ISSN: AGRICULTURAL RESEARCH COMMUNICATION CENTRE Ergonomic evaluation of conventional agricultural sprayers with respect to human performance P. Tamilselvi* 1 and D. Anantha Krishnan 2 Department of Farm Machinery, Tamil Nadu Agricultural University, Coimbatore , India. Received: Accepted: DOI: /asd.v36i ABSTRACT Ergonomic intervention in spraying operation can provide a reasonable basis for recommendation on operating methods and improvement in operation for more output and safety. Two commercially available sprayers namely knapsack sprayer and rocker sprayer were evaluated with nine male subjects for the study. Age, weight and height of the selected subjects are 30.33±1.93 years, 68.33±9.51 kg and ±5.55 cm respectively. The major operational parameters including pressure and lever arm distance of the sprayers were selected and optimized based on human performance. Heart beat rate and operating energy requirement for ergo refined knapsack and rocker arm sprayers were observed as beats per minute, beats per minute, and KJ min -1, KJ min -1 respectively. The field evaluation results showed that ergo refined knapsack sprayer and ergo refined rocker sprayer reduced the energy expenditure by 7% and 8%, oxygen consumption as percentage of VO 2 max by 19% and 23%, HR results gave a reduction of 22% and 23%, ODR results gave a reduction by 4% and 5% and BPDS score indicated a reduction of 13% to 12% respectively from the conventional sprayers. The above results confirmed that the ergo refined sprayers provided better comfort and efficiency to the operator. Key words: BPDS, Ergonomics, Lever arm distance, LOK sprayers, ODR, VO 2 max. INTRODUCTION In India, crops are affected by over 200 major pests, 100 plant diseases, hundreds of weeds and other pests like nematodes, harmful birds, and rodents. Approximately, 18 per cent of Indian crop yield potential is being lost due to insects, disease and weeds which in terms of quantity would mean 30 million tonnes of food grain. The value of total loss has been placed at Rs 50,000 million, represents about 18 per cent of the gross national agriculture production. (Manncsa, 2009) Control of pests and disease is achieved by various plant protection methods. This includes agro technical, biological, chemical, physico-mechanical and others. But chemical application is the viable option since; it is highly effective, relatively simple and quick to apply. Sprayer is a machine to apply herbicides, fungicides, and insecticides in the form of droplets. Among the others lever operated knapsack sprayer, Power sprayer and manually operated sprayers are commonly used by small farmers to medium farmers. Spraying is an energy consuming operation in crop production, because of sprayer weight with spray fluid are carried by the worker throughout the entire covering area makes a need of high energy consumption during spraying. *Corresponding author s tamilbeag@gmail.com. 1 Department of Farm Machinery, Tamil Nadu Agricultural University, Coimbatore Agricultural Machinery Research Centre, Tamil Nadu Agricultural University, Coimbatore During sprayer operation, the operator s body assumes an awkward position giving severe discomfort to the body. The frequent up and down movement of lever in lever operated knapsack sprayers and rocking motion of a lever in rocker arm sprayer causes undue fatigue and discomfort to human body. Gite, et al. (1991) investigated on lever operated manual knapsack sprayer. The study indicated that though the workload in the spraying operation was within acceptable limits according to physiological criteria, there is a need to make improvements in the mounting of the sprayer on the operator s back to reduce the postural discomfort. Gite (1993) reported that generally, a workload, which requires oxygen at a rate of about 35 per cent of VO 2 max, is considered as the accepted workload for Indian workers and the values work out to be 0.70 l min -1 and 0.63 l min -1 for male and female workers respectively. The corresponding heart rate values for this workload will be about 110 beats min -1 and 105 beats min -1. Narasingarao (1997) evaluated LOK sprayers considering human performance. During this study, the heart beat rate, oxygen consumption, energy expenditure were calculated for three commercially used LOK sprayers. He

2 180 AGRICULTURAL SCIENCE DIGEST- A Research Journal Table 1: Specifications of the selected sprayers Particulars Sprayer I Sprayer II Name of the selected sprayer Hand operated knapsack sprayer Rocker sprayer Manufacturer ASPEE works Ltd, Malad, Mumbai ASPEE works Ltd, Malad, Mumbai Model SRP/60 GR/5 Capacity (l) 16 - Overall dimensionsl W H (cm) Empty weight of the sprayer (kg) (with discharge line) Weight of the sprayer with spray fluid (kg) Pressure range (kg/cm 2 ) Pressure vessel HDPE Brass Spray lance Brass Brass concluded that the spraying operation using the LOK sprayers was classified as moderate work. Gurpreetsingh et al. (2006) evaluated on power knapsack sprayer. The independent parameters selected were three subjects of different age groups and three engine rpm (4000, 5000 and 6000) for the machine. The heart rate varied from 96 to 117 beats per minute, overall discomfort rating between 2.83 and 4.50 and postural configuration between 2.67 and 9.67 while operating the sprayers. Ergonomic intervention plays a vital role to enhance the functional effectiveness with which people can use them and to maintain or enhance desirable human values. To get better efficiency of human machine system, it is necessary that the sprayer matches to the capabilities and limitations of the operator. Hence the study was carried out for identifying the ergonomic problems, energy expenditure for operating sprayers and refinement of conventional sprayers with reference to ergonomic considerations. MATERIALS AND METHODS Two commercially available conventional sprayers with different systems namely rocker sprayer and hand operated Knapsack sprayer had been selected for the study (Table 1). Nine male workers were selected for the study based on age and medical fitness. (Table.2). Eighteen body dimensions in relation to sprayer operations were measured (Table 3). The selected subjects were calibrated in the laboratory by indirect assessment. For indirect assessment of oxygen uptake for the spraying operation, the heart rate of the subject while running on a treadmill and the corresponding oxygen uptake were measured and plotted. The heart rate of the subject during exercise in the treadmill was measured using K4b 2. It is an electrical medical device designed to perform pulmonary function tests. The maximum heart rate attainable by the subjects was computed by Maximum heart rate= (Age in years 25) x 0.62 The intersection of the computed maximum heart rate of the subjects with the plotted calibration chart line and the line of fit to the oxygen uptake defines the maximum aerobic capacity (VO 2 max) of the individual. The VO 2 max for all the subjects was computed and recorded. The parameters such as operating pressure, fore arm length of spraying operation and lever arm distance and acromial height of the subject. The levels of variables selected for the various independent parameters affecting the operating energy required for sprayers are furnished in Table 4 and 5. Ergonomic evaluation parameters: Heart rate and oxygen consumption rate, Energy cost of operation, Grading energy cost of work, Acceptable Work Load (AWL), Limit of Continuous Performance (LCP), Overall Discomfort Rating (ODR), Body Part Discomfort Score (BPDS) were find out through experiments. The heart rate data was recorded using computerized heart rate monitor (polar S 810i). From the downloaded data mean values of heart rate, oxygen consumption rate and the energy expenditure rate for all the subjects were computed. The acceptable workload (AWL) for Indian workers was the work consuming 35 per cent of VO 2 max (Saha et al., 1979). To ascertain whether the selected spraying operations are within the acceptable workload (AWL), the oxygen consumption rate in terms of VO 2 max was computed. To have a meaningful comparison of physiological responses, work pulse ((DHR) values (increase over resting values) were calculated (Tiwari and Gite, 1998). The mean values of work pulse for spraying Table 2: Details of selected subjects for spraying operation Subject Age Weight Height Experience (Years) (Kg) (cm) I years II years III years IV years V years VI years VII years VIII years IX years Mean± SD 30.33± ± ±5.55

3 Table 3: Anthropometric data of selected subjects Volume 36 Issue 3 (2016) 181 Body dimensions Mean SD Range Percentile value max min 5 th 95 th Weight (Kg) Stature (cm) Acromial height (cm) Illiocrystale height (cm) Arm reach (cm) Bideltoid breadth (cm) Interscyce breadth (cm) Waist breadth (cm) Fore arm length(cm) Hand breadth at metacarpal III(cm) Hand breadth (cm)across thumb Palm length(cm) Hand thickness at metacarpal III(cm) Grip diameter (inside) (cm) Grip diameter (outside) Elbow to finger tip length(cm) Shoulder to elbow length(cm) Elbow rest height(cm) Max grip length(cm) Table 4: Levels of variables for Knapsack sprayer Parameter Levels Values Operating pressure (P), MPa Fore arm length (L), mm P1 P2 P3 L1 L2 L Table 5: Levels of variables for Rocker sprayer Parameter Levels Values Operating pressure (P), MPa Acromial height (L), mm P1 P2 P3 L1 L2 L Fig 1: Field evaluation of ergo refined sprayers

4 182 AGRICULTURAL SCIENCE DIGEST- A Research Journal operation were compared with the acceptable work pulse values of 40 beats min -1 as limit of continuous performance. For the assessment of overall discomfort rating (ODR) and body part discomfort score (BPDS), a 10 point psycho physiological rating scale was used which is an adoption of Corlett and Bishop (1976) technique. At the end of each trial with the selected spraying practice the subject was asked to indicate their ODR and BPDS level on the 10 point rating scale. The conventional knapsack sprayer was modified by sorting the problems identified in operating the sprayer. It was found that the straps resting on the shoulder causes a severe ache in shoulder & lower neck regions. Hence it is decided to provide a sponge along with the straps. A grip was provided on the handle to reduce the ache being caused in the palm. The grip provided on the handle having thickness of 6.35mm and the diameter of 12.7mm was fixed based on the hand grip diameter calculated for selected subjects. The length of the handle was 450mm. A typical lever operated rocker sprayer consists of a pressure vessel, a connecting hose with a lance and a nozzle, and an operating lever. The handle is extended in length with 12.7 mm diameter MS round pipe. The length of the handle is 1250 mm from the hinge point. The work performance of the sprayer is not only depends on the equipment but also on the operator. During the operation of the sprayer, the body is in awkward posture. Thus to reduce the injury the handle length was fixed as 1250mm. The refinements of the sprayers were carried out based on Anthropometric and strength data of Indian agricultural workers for farm equipment design (Gite et al., 2009). The ergonomically refined sprayers were evaluated with the subjects at TamilNadu Agricultural Table 6: specifications of the loadcells University farm, Coimbatore. The trials were conducted between 8.00AM to 11.30AM during the month of May, 2012 and the ergonomical evaluation parameters were compared with the conventional spraying operation. Effort required for operating sprayers: The effort required for the operation of the knapsack sprayer and rocker arm sprayer was found with the help of load cell and load indicator. For this experiment a 20 kg capacity and 200 kg capacity tension compression load cells were used (Table.6). The effort measurement was done by modifying the handle of the sprayers by providing a provision for fixing the loadcell. The loadcell was used to measure the force required in upward as well as downward strokes. The 20kg capacity load cell was fixed on the upper part of the handle in the lever operated knapsack sprayer. The load cell was connected to the load indicator. Selected nine subjects were used and whose efforts for operating the sprayer was recorded. The sprayer was filled with water and then properly mounted on operator s back. Initially, the subject was asked to build up working pressure by applying strokes in a standing posture. Maximum readings were noted from the indicator for about 5 min. Then the subject was given a break for 5 min and the same procedure was repeated for three times. The same procedure was repeated for rocker arm sprayer with 200 kg load cell with the selected parameters. RESULTS AND DISCUSSION The factors causing the physical fatigue while operating the sprayers were weight, operating force and energy. Hence the need for refinement of sprayers based on limitations and capabilities was felt. The comparison of the conventional lever operated sprayers with ergo refined sprayers in the field and the observations are given in Table.7. Specifications Load cell -200 kg Load cell -20 kg Model CZL Precision 0.02 % F.S - Rated output, (mv/v) Non- linearity, % F.S ±0.025 Hysteresis, % F.S ±0.02 Repeatability, % F.S < ±0.01 Creep, % F.S/30 min < ±0.03 Temp. Effect on zero, % F.S/ 10 C < Temp. Effect on span, % F.S/10 C < Zero balance, % F.S ± 1.5 ±5.0 Input impedance, Ohm 402± ± 15 Output impedance, Ohm 350± ± 3 Insulation resistance, M ohm >-5000 >1000 Recommended excitation voltage, VDC 9~12 10~15 Allowed excitation voltage, VDC 5~18 4~16 Compensated temp. Range, C -10 C ~ +40 C C Operating temp. Range, C -20 C ~ + 55 C 10 ~ 50 Safe overload, % F.S Ultimate overload, % F.S Finish & Construction Anodized Aluminium Alloy Anodized Aluminium Alloy

5 Table 7: comparison of Ergonomic parameters of selected spraying systems Volume 36 Issue 3 (2016) 183 Parameters Sprayers Knapsack Rocker Ergo refined Ergo refined sprayer sprayer knapsack sprayer Rocker sprayer Mean heart rate, Beats min Estimated oxygen consumption,l min Estimated Energy expenditure, kj min Oxygen consumption rate as percent of VO 2 max AWL (35% of VO 2 max) >AWL >AWL >AWL >AWL DHR,Beats min LCP, 40 Beats min -1 >LCP >LCP >LCP >LCP Overall Discomfort Rate(ODR) BPDS score The maximum heart rate of selected subject was 181±1.44 beats min -1 and the maximum aerobic capacity of the selected nine male subjects varied from 1.90 to 3.5 l min -1 Among the four sprayers, the physiological cost of spraying was the highest for rocker sprayer and the lowest values were observed for ergo refined knapsack sprayer. This might be due to the ergo refinements carried out. The energy cost of spraying operation with ergo refined sprayers varied from to kj min -1. AWL values were much higher than that of the AWL limit of 35 per cent of VO 2 max indicating that all the selected sprayers could not be operated continuously for 8 hours without frequent rest-pauses. The mean values of work pulse for spraying with selected sprayers varied from 44 to 52 beats min -1. But the values were lower for ergo refined rocker sprayer when compared with other sprayers. In general, the work pulse values calculated for the entire selected four sprayer operations were higher than the LCP value of 40 beats min -1, which is clear indicative of the fact that these sprayers could not be operated for longer duration without adequate rest. From the mean values of overall discomfort rate, discomfort experienced by the subjects was lesser for ergo refined rocker sprayer when compared with other sprayers. The less body part discomfort score (BPDS) was experienced by ergo refined knapsack sprayer. The majority of discomfort Table 8: Mean of operating energy for different combination of parameters for knapsack sprayer Combination Heart rate Energy expenditure (beats min -1 ) (kj min -1 ) P1L P2L P3L P1L P2L P3L P1L P2L P3L experienced by the workers was in clavicle right shoulder, left shoulder and lower back for all the subjects. The discomfort experienced by the subjects was mainly due to the alternate up down and push-pull action associated with the operation coupled along with the additional effort required to spray fields. Heart rate during the sprayer operation were measured at three fore arm length of 550, 450 and 350mm. Heart rate ranges from 93 to 120 beats per minute. It is observed that increase in pressure the heart rate was also increased. The operating energy required for operating sprayer was ranging from to kj min -1. At high pressure rate, the energy expenditure was maximum during the operation (Table 8). Heart rate during the sprayer operation were measured at three lever arm distances of 1350, 1250 and 1150mm. Heart rate ranges from 97 to 120 beats per minute. It is observed that at high pressure the heart rate was also increased. The operating energy required for operating sprayer was ranging from to kj min -1 (Table 9) The effort required for the operation of the knapsack sprayer, rocker arm sprayer, ergo refined knapsack sprayer and ergo refined rocker sprayer was found with the help of calibration charts. From the Table 10 and 11, it is observed that the mean force required for operating the knapsack sprayer was Table 9: Mean of operating energy for different combination of parameters for rocker sprayer Combination Heart rate Energy expenditure (beats min -1 ) (kj min -1 ) P1L P2L P3L P1L P2L P3L P1L P2L P3L

6 184 AGRICULTURAL SCIENCE DIGEST- A Research Journal Table 10: Effort required for operating knapsack sprayer Subject Conventional knapsack sprayer Required force (N) Ergo refined knapsack sprayer Subject I Subject II Subject III Subject IV Subject V Subject VI Subject VII Subject VIII Subject XI Mean±SD ± ± ± 2.36 N and operating force for ergo refined knapsack sprayer was ± 1.63 N. The force required for operating the rocker sprayer was ± 7.28 N push Table 11: Effort required for operating rocker sprayer force and ± 5.69 N pull force. The force required for operating the ergo refined rocker sprayer was ± 3.88 N push force and 72.95±7.35N pullforce. From these values the operating force for operating ergo refined sprayers were less compared to conventional sprayers. The results showed that ergo refined knapsack sprayer and ergo refined rocker sprayer reduced the energy expenditure by 7 per cent and 8 per cent, respectively. In case of oxygen consumption as percentage of VO 2 max, the ergo refined knapsack and rocker sprayer showed a reduction of 19 per cent and 23 per cent, respectively. A reduction of 22 per cent and 23 per cent of work pulse rate ( HR) values were observed for both type of ergo refined sprayers. According to ODR values, it was 4 per cent and 5 per cent, respectively. The BPDS score also indicated a reduction of 13 per cent to 12 per cent from the conventional sprayers. The above results confirmed that ergo refined sprayers performed better. Subject Operating force for rocker sprayer (N) Operating force for ergo refined rocker sprayer (N) Push force Pull force Push force Pull force Subject I Subject II Subject III Subject IV Subject V Subject VI Subject VII Subject VIII Subject IX Mean±SD ± ± ± ± 7.35 REFERENCES Gurpreet Singh, Shiv Shankar Kumar, Manes, G. S., Anoop Dixit and Arshdeep Singh. (2006). Spray distribution pattern of different sprayers on cotton using droplet analyzer, Journal of Research, SKUAST-J, 10: Corlett, E.N. and Bishop, R.P. (1976). A technique for assessing postural discomfort. Ergonomics, 19: Gite, L. P., Majumder, J., Mehta, C. R. and Abijit K. (2009). Anthropometric and strength data of Indian agricultural workers for farm equipment design. Coordinating cell AICRP on Ergonomics and Safety in Agriculture, CIAE Bhopal Gite, L.P. (1991). Ergonomics evaluation of a lever-operated knapsack sprayer. Journal of Applied Ergonomics, 22: Gite, L.P. (1993). Ergonomics in Indian Agriculture A review. Paper presented in the International workshop on human and draught animal powered crop protection held at Harare, Jan Manncsa, (2009). Pesticides in Agriculture, Press Trust of India. Narsingh Rao, S. (1997). Ergonomic analysis of man machine system on sprayers, Unpublished M.E. thesis in Dept of Farm Machinery, TamilNadu Agricultural University, Coimbatore. Saha, P.N., Datta, S.R., Banerjee, P.K. and Narayane, G. (1979). An acceptable workload from a modified scale of perceived exertion, Ergonomics, 37: Tiwari, P.S. and Gite, L.P. (1998). Human energy expenditure during power tiller operations. Paper presented during XXXIII annual convention of ISAE, CIAE, Bhopal, September, pp