Abdollah Hayati; Afshin Marzban; Majid Rahnama
Abstract
Introduction Date fruit production has an important position in either Iran or the world. Life and economy of many of people who live in the West Asia and North Africa (WANA) depend on this agricultural product. Date palm crown access, as one of important operations of date fruit production, is performed ...
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Introduction Date fruit production has an important position in either Iran or the world. Life and economy of many of people who live in the West Asia and North Africa (WANA) depend on this agricultural product. Date palm crown access, as one of important operations of date fruit production, is performed in a traditional manner with a tool talked “Parvand” yet. It results in various ergonomic and safety problems, such as fall from height, sunstroke, and musculoskeletal disorders (MSDs). Meanwhile, mechanization could not adequately adopted by date palm growers. Possibly, ergonomic interventions in forms of simple tools mitigate ergonomic and safety problems in date palm crown access operation.Materials and Methods In this study, some ergonomic interventions were investigated to improve the present status of ergonomic and safety status of this operation with employing nine workers from Ramshir city, Khuzestan province, Iran. Evaluated date palm climbing tools were as follows: Parvand (traditional tool), Parvand+rubber shoes (intervened tool), harness (intervened tool), and harness+rubber shoes (intervened tool). Parvand consisted of a backrest and a towing wire. In two last mentioned intervened tools, harness was replaced with backrest in Parvand. Indeed, harness was the brief name of composition of harness and towing wire. Comparisons were done based on some ergonomic, safety, bio-mechanical, and technical indices. Ergonomic evaluations included physical and cognitive ones. Body discomfort (BD), heart rate (HR), worker energy expenditure (EE), working oral temperature (OT), and physiological strain index (PSI) were the physical indices. Perception-based heat Strain Index (PeSI) and acceptance of climbing tools in view of workers were the cognitive Indices. Acceptance comprised workers’ perception about safety, work speed, ease of use, technical properties, and preference of the tools. Safety evaluation was conducted using failure mode and effects analysis (FMEA) which resulted in a risk priority number (RPN) for each climbing tools. Bio-mechanical evaluations were performed using 3DSSPP software (to find the compression and shear forces on L5/S1 disc) and the investigation of mechanical stresses of Parvand and harness (to achieve the factor of safety (FoS) of tools). Technical index was the total time cycle (TTC) to perform date palm crown access (install climbing tool, ascending, and descending). Statistical analysis was conducted using IBM SPSS 24. During evaluation, workers’ qualitative feedbacks around intervened tools were recorded.Results and Discussion Mean age, height, mass and body mass index of workers were 33.1 years, 1.71 m, 74.0 kg, and 25.3 kg/m2, respectively. According to the statistical analyses, there was no any significant difference among climbing tools regarding BD, HR, EE, OT, PSI, PeSI, RPN, and TTC. Bio-mechanical evaluations showed that all four climbing tool caused a low risk compression force on L5/S1 (<3400), whereas interventions including harness were significantly higher than those including Parvand. Traditional and Parvand+rubber shoes with shear forces of 1120.9 and 1119.6 N, respectively, on L5/S1 disk resulted in high injury risk (>500 N) and were significantly higher than other two methods in which harness was used (p<0.001). FoS was achieved for Parvand and harness 1.21 and 3.53, respectively. Therefore, only harness could cover the minimum FoS required to work in height (2.4) according Ministry of Cooperative, Labor and Social Welfare’s regulations. During cognitive evaluations, harness+rubber shoes gained the highest safety level (score of 17) as well as the highest preference level (score of 14), whilst, Parvand+rubber shoes had the highest cognitive-based acceptance score (score of 58). Workers’ qualitative feedbacks, in order of frequency, were as follow: harness ropes should be wider (33%); towing wire-harness joint should be upper (from pelvis toward waist) (22%); harness ropes should be softer (especially around the thighs) (22%); harness should be integrated (i.e. without rope, like a short) from pelvis to thighs (11%); rope buckle should be used so that harness is more easily-and fast worn (11%).Conclusion Safety and work speed can be two main factors in the preference of a date palm crown access tool. Overall, intervened tools had a better state concerning safety, whereas, the qualifications were almost equal considering ergonomics. Notwithstanding it, the intervened tools had the lacks around work speed and technical properties which should be amended. Besides the attempts for development of date palm mechanization, further studies may be conducted on intervened date palm climbing tools, especially harness+rubber shoes method, based on workers’ qualitative feedbacks to gain a more appropriated level.
Post Harvesting Technology
Poya kohansal makvandy; Majid Rahnama; Rasol Memar dastjerdy; Alireza Shafeinia
Abstract
Introduction Material conveying in the industries is carried out in the different ways. Pneumatic conveyors are widely used in industries. The special benefits of these conveyors have led them in the short term to widely used in different industries. Transfer of materials without dust dispersion, the ...
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Introduction Material conveying in the industries is carried out in the different ways. Pneumatic conveyors are widely used in industries. The special benefits of these conveyors have led them in the short term to widely used in different industries. Transfer of materials without dust dispersion, the flexibility to choose the vertical, horizontal or diagonal tubing, low maintenance costs and manpower, adequate safety and reliability during conveying at the high amounts of materials, easy and automatic control are the some benefits of the pneumatic conveying systems Materials and Methods The mean aperture and the coefficient of variation of sugar particles were determined by sugar crystal size distribution test. It is done based on the cumulative percentages of remaining sugar content on the sieve. The mean aperture (MA) and the coefficient of variation (CV) are obtained from the chart. 7 sieves are used for testing. The percentage of remaining sugar on each sieve was calculated. The amounts of D50% and D16% were calculated following the plotting the size of the sieves versus the cumulative percentage of the remaining sugar on each sieve graph. The conveying pressure drop includes the total pressure drop required for air alone (ΔPL), the material acceleration pressure drop (ΔPA), the friction and material collision pressure drop (ΔP*z), the pressure drop due to lifting and suspension of materials (ΔPG), and bends' pressure drop (ΔPB) in Pascal. Following determination of required power (293.42 w) to run the system, with a confidence coefficient of 3, a blower with a rated power of 700 w was selected. The amount of pressure produced by the selected centrifuge fan was measured by a pitot tube embedded in the blower outlet. The outlet air velocity was measured by a pressure gauge according to the principles of the pitot tube. Results and Discussion The treatments and their levels consisted of pipe lengths at three levels (2, 4 and 6 m), inlet air velocity at five levels (13, 16, 19, 22 and 25 m/s) and mass flow rate of sugar at three levels (160, 180 and 200 kg/h). The statistical analysis was done as a factorial based on a completely randomized design. Analysis of variance and comparison of means were done using Duncan's test at 5% level in each case. Then, the effects of the factors on pressure drop, mean aperture and coefficient of variation of particle size were investigated. Analysis of variance of data shows that the effect of conveying length, mass flow rate of sugar particles and inlet air velocity as well as their interactions and the interaction of three factors on air and sugar pressure drop is significant at 1%. In all conveying lengths, an increase in air velocity and consequently increased sugar particles' velocity at each mass flow rate causes an increase in frictional pressure drop due to the particle's collision with the wall as well as air collision with the pipe wall at each length and the sugar mass flow rate level. Also, total pressure drop has increased with mass flow rate at any velocity. Analysis of variance of data shows that the effect of conveying length, mass flow rate of sugar particles, inlet air velocity, and the interaction of mass flow rate and air velocity on qualitative properties of sugar is significant at 1% level. Considering the significance of the effects of the main factors and interactions between air velocity and mass flow rate, the effect of every main factors and the interaction of air velocity and mass flow rate on qualitative characteristics of the sample was investigated. With increasing velocity in each mass flow rate, the mean aperture and coefficient of variation significantly decreased and increased, respectively. Also, with increasing mass flow at any velocity, the mean aperture decreased and the coefficient of variation increased. By increasing the mass flow rate, the effect of the air velocity on the mean aperture reduction and increase in coefficient of variation increases, and at higher velocities, the mass flow rate effect is more pronounced. Conclusion The length of the pipe with a reduction by 15% in mean aperture and an increase of 137.5% in coefficient of variations than the initial sugar sample had the least effect on these two qualitative properties of sugar. With an increase in air velocity from 13 to 25 m/s, MA and CV values decreased by 20.27 and increased by 17.22, respectively. The velocity of 13 m/s with a reduction of 5.19% in the mean aperture and an increase of 6.69% in coefficient of variation compared to the initial sugar sample had the least effect on the size and the particle coefficient of variation size of the particles among all 5 velocity treatments. With the increase in particle mass flow rate of 160 to 200 kg/h, MA and CV values decrease by 16.49% and increase by 14.75%, respectively. The particle density increases with the mass flow rate.
Yousef Abaspour Kalan; Mohammad Nikbakht; Majid Rahnama
Volume 36, Issue 1 , September 2013, , Pages 23-34
Abstract
Drying grape fruit as a strategic product in Iran faces numerous challenges including color change, spoilage, and hygienic issues and long drying time. To this aim, the present research was conducted to kinetically study the thin-layer hot air drying of grape fruit together with mathematical modeling ...
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Drying grape fruit as a strategic product in Iran faces numerous challenges including color change, spoilage, and hygienic issues and long drying time. To this aim, the present research was conducted to kinetically study the thin-layer hot air drying of grape fruit together with mathematical modeling to cover the drying process. The results give a promising opportunity for an appropriate design of a dryer. Experimental setups included four levels of air temperature, 40, 50, 60 and 70 oC and air velocity of 1.2 ms-1. Ten semi-empirical and empirical models were subsequently fitted to the experimental data and statistical criteria, coefficient of determination (R2), Chi square (χ2) and Root Mean Square of Error (RMSE) were investigated. Results showed that air temperature of drying has a meaningful effect on the drying rate in a way that increasing the temperature from 50oC to 60oC led to a 59% reduction in the drying time. It was observed that the whole drying process was located in the falling drying phase. Modeling evaluation of data showed that Midili model fitted best (R2=0.9978, χ2=0.0001679 and RMSE=0.010234) to the experimental results. Additionally, the influence of air temperature on the constants and coefficients of the studied models was extensively assessed.
