ergonomics evaluation of a manually operated multi

Transcription

ERGONOMICS EVALUATION OF A MANUALLY OPERATED
MULTI-PURPOSE JUICE EXTRACTOR
ADEMOLA K. AREMU
Department of Agricultural and Environmental Engineering
E-mail: ademolaomooroye@gmail.com
Abstract- A manually operated multipurpose juice extractor was designed and constructed for use in rural and urban areas
for extraction of juice from tropical fruits. The machine was ergonomically evaluated to access the anthropological and
physiological workload on end-users. A total of twenty-five (25) subjects within age groups 15 to 41 years and above were
selected for this study. The subjects were physically fit for performing the operation and they were acclimatized with the
experimental procedure before the commencement of the evaluation. The ergonomics evaluation included anthropological
measurement (measurement of the body weight, age, height and arm length and physiological evaluation (measurement of
blood pressure and heart beat rate at normal rest position and after machine operation). The oxygen consumption rate and
energy expended in operating the machine was also studied. The arm length of subjects ranged from 66.3-76cm for age
groups 15-20 and 36-40 respectively, average body mass ranged from 54-72kg for age groups 15-20 and 31-35 respectively
while average height ranged from 145-176cm for age groups 41 and above and 31-35 respectively. Highest increase in
blood pressure and heart beat rate of subjects after machine operation was obtained to be 40 mmHg for age group 21-25 and
16beats/min for age group 15-20 years respectively. The highest oxygen demand and energy expended by the subjects after
machine operation was 0.4144 L/min and 6.5444kJ/min respectively. Percent juice yield, extraction efficiency and extraction
loss was obtained to be 65 (for age group 21-25), 41 (for age group 15-20) and 23 (for age group 31-35). Moreover, 28%
subjects felt pains at the arm while 20% felt pain at the chest after operating the machine and 52% did not feel any pain after
operating the machine. The machine is cost-effective, simple to operate and maintain and causes less discomfort to the users,
it is therefore recommended for small local fruit processors and rural dwellers.
IndexTerms- Juice Extractor, Anthropometrics, Physiological, Performance Evaluation, Ergonomics Evaluation.
produce high quality juice from the abundance of
fruits available at their disposal. In lieu of this, [2]
designed and constructed a portable multi-purpose
juice extractor for use in both urban and rural areas;
the machine performance is dependent on skill, age,
sex and some other ergonomics parameters. The
machine was designed to be used manually by people
of all age groups in various homes, there is need to
ergonomically evaluate the machine to study its
physiological effect on end-users. Ergonomics
evaluation is the human factors engineering which
studies the levels of injuries and discomfort caused on
end-users as a result of machine usage. In Nigeria,
local fabricators of agro-processing equipment have
designed and manufactured various improvised
versions of many processing machines without due
ergonomic considerations [3]. The objectives of this
study was to evaluate the anthropometrical and
physiological characteristics of the machine operators
and assessment of the magnitude of the machine
usage-related injuries
I. INTRODUCTION
Fruits are important component of human diet
because of the large content of vitamins A, B and C
as well as minerals like calcium and iron, which help
meet daily nutrient requirement and good health.
Most fruits are seasonal in availability and highly
perishable in natural and fresh forms because of their
high water content (70-90%) which aids chemical
deterioration [1] however, adequate storage and
processing technology of these fruits into forms that
can easily be stored, preserved, packaged or
consumed is essential as it will play an important role
in contributing to self-sufficiency in food production.
Fruit extraction methods in homes is crude; people
apply pressure and squeeze fruits with hand and
mouth in order to get the juice out of the fruit (for
citrus and cashew), other methods like peeling and
eating raw (for fruits like pineapple, pawpaw and
watermelon) are also adopted. These methods are
primitive and consume both time and energy. Nigeria
as a developing country is trying to attain the level of
technological advancement to meet the ever
increasing demands of her teeming population. The
country is blessed with numerous fruits yet;
modernized juice extractors are still being imported
while the few ones produced in the country are
expensive and cannot be afforded in homes by
peasant farmers and rural dwellers. There is need for
agricultural and food engineers, to produce costeffective machines that will extract juice from raw
fruits in rural and urban areas to enable local farmers
II. MATERIALS AND METHODS
A. Sample Preparation
Fresh oranges (Citrus sinensis) and watermelon
(Citrullus lanatus) fruits were procured from Bodija
market in Ibadan, Oyo State, Nigeria. The fruits were
cleaned and sorted by physical examination before
being used for the ergonomics evaluation of the
machine.
Proceedings of TheIRES 8th International Conference, London, United Kingdom, 30th Aug. 2015, ISBN: 978-93-85465-83-3
27
Ergonomics Evaluation Of A Manually Operated Multi-Purpose Juice Extractor
B. Principle of Operation of the Machine
The fruits were fed into the hopper and the screw rod
is turned manually which thus rotates in the cylinder
drum and compresses the fruits. The cylinder has an
opening at the base to allow passage of extracted
juice through a mesh steel plate to sieve the
suspension. The rotary motion of the screwed rod
moves the fruits against the stationary plate in the
cylinder where squeezing is done and the juice is
extracted. The screwed rod with the flat plate
conveys, crushes, presses and squeezes the fruits to
force-out the juice. The juice extracted is filtered
through the juice sieve into the juice collector. The
isometric view of the machine is presented in Figure
1.
E. Oxygen Consumption and Energy Expenditure
The oxygen consumption rate of subjects at their
measured heart beat rate after machine operation was
estimated using the general equation given by [7] as:
= 0.0114 − 0.68
(1)
Where: Y is the oxygen consumption (L/min), X is
the heart beat rate after machine operation
(beats/min)
Also, the energy expenditure was calculated using the
formula given by [8] as:
= (0.159
) − 8.72
(2)
Where: EE is the energy expenditure (kJ/min), HR is
the heart beat rate (beats/min).
The values obtained for energy expenditure were
compared and categorized as per standard values
reported by [9] and presented in Table 1:
Table 1: Categorization of Agricultural work
Source: Nag et al. (1980)
F. Measurement of Muscular Stresses and Postural
Discomfort
Muscular stresses during the ergonomics evaluation
were measured by recording the incidences of pain
perceived by the subjects from different parts of
body. Intensity of pain in body parts of the body was
measured on a five-point scale given below as
described by [8].
Table 2: Categorization of Severity of Pain from
Machine Operation
Figure 1: Isometric View of the Manually Operated MultiPurpose Juice Extractor
C. Subjects
Twenty five subjects were selected within age groups
15-20, 21-25, 26-30, 31-35, 36-40, 41 and above
(each numbering 4, 8, 6, 2, 1, 4 respectively) because
the machine was designed to be operated by adults
from age 15 as most people usually attain their
highest strength between 20-45 years [4]. All the
subjects were physically fit and were not suffering
any disability that will disrupt the machine operation.
The operators were acclimatized with the
experimental protocol before the commencement of
the test and were given training on the operational
techniques of the machine [5], [6].
Source: Kwatra et al. (2010)
A. Performance Evaluation of the Machine
Mass of peeled and unpeeled fruits was fed through
the hopper into the cylindrical drum for crushing and
compression against the end plate to extract the juice.
The time taken for extraction, mass of fruit fed into
the machine, mass of juice extracted and mass of
residual waste was obtained and recorded using a stop
watch and weighing scale. The mass of juice in chaff
was determined using the method of [10] as applied
by [11] and [12]. The following indices described by
[11], [13], [14], [15], [16], [17] were used to calculate
the juice yield, extraction efficiency and extraction
loss of the machine while the juice constant was
obtained from the ratio of sum of masses of juice
extracted and juice in chaff to the mass of fruit fed in
as presented in Equations 3-6.
D. Anthropometrics and Physiological Evaluation
The subjects were selected at random and the
anthropometrics evaluation was carried out by
measuring the body weight, height and arm length
using a weighing scale (120kg, 260 lb Capacity, made
by Hana Company, China) and meter rule.
The blood pressure and heart beat rate of the subjects
were taken before (at normal rest position) and in
working conditions after the machine was operated. A
sphygmomanometer (KRIS-ALOY CE 0483,
Capillare 3, 5 mm+ 0.1 300 mmHg) with a
stethoscope was used for the physiological evaluation
of the subjects. The difference in blood pressure and
heart beat rate was compared both at normal rest
position and after the operation of the machine to
determine the significant variation in blood pressure
and heart beat due to the usage of the multi-purpose
extractor.
28
observed for age group 31-35. The arm length
increases with an increase in age while no definite
pattern was noticed for the variation in height within
the age groups. The results of the anthropometrics
evaluation and relationship of age on the ergonomic
data of the operators is presented in Table 3 and the
results obtained for the physiological evaluation of
subjects at normal rest position and after machine
operation difference is presented in Table 4. The
heart-beat rate, oxygen consumption and energy
expenditure of the subjects is presented in Table 5
while Figure 2 shows the variations in heart beat rate
of subjects at normal rest position and after machine
operation.
Where: WJE is Mass of juice extracted in grams, WRW
is the Mass of residual waste in grams, WFS is the
Mass of fed sample in grams and X is the juice
constant of fruits in decimal, Wi is the weight of
fruits fed into the machine and Wjc is mass of water
in the chaff (determined after drying)
III. RESULTS
B. Performance Evaluation of the Machine
The average and standard deviation of the percentage
juice yield, extraction efficiency and extraction loss
obtained for each age group is presented in Table 5
and Figure 3.
A. Anthropometrics and Physiological Evaluation
The body weight of operators increases with increase
in age from age group 15-20 to 31-35 while there was
a decline in body weight from age group 31-35 to 41
years and above. Maximum body weight was
Table 3: Anthropometrics Evaluation of the Subjects
Table 3: Physiological Evaluation of the Subjects
29
Table 4: Physiological Evaluation of the Subjects (Heart Beat Rate)
Figure 2: Heart Beat Rate of Subjects at Normal Rest Position and after Machine Operation
Table 5: Performance Evaluation of the Juice Extractor
S. D. is the Standard Deviation
30
range from 6/6 to 40/40 for age groups 15-20 and 2125 years respectively while the highest difference in
heart beat rate before and after machine operation
was obtained to range from 6 to 16 beats/min at 41
and above and 15-20 years respectively. The machine
is cost-effective, simple to operate and maintain, it is
therefore recommended for small local fruit
processors and rural dwellers.
REFERENCES
[1]
Figure 3: Performance Evaluation of the Multi-purpose Juice
Extractor
[2]
IV. DISCUSSIONS
The physiological workload while operating the
manually operated multi-purpose juice extractor was
assessed based on their heart beat rate response and
blood pressure, the heart beats increases with an
increase in blood pressure and age of the subjects as
shown in Table 3 and 4, this implies that there was a
physiological difference in the normal heart beat and
blood pressure at normal rest position and after
machine operation, a similar trend was observed
many researchers [18], [19], [20], [21], [22], [23].
The highest energy expended (6.544 kJ/min for age
group 15-20) signifies that the machine operation and
usage is light as reported by [9].
The machine operation causes discomfort to some of
the machine users; 7 subjects claimed to feel pains at
the arm, 5 felt pain at the chest after operating the
machine while 13 users did not feel any pain after
operating the machine however, all the pain felt by
the subjects are mild as categorized in Table 2. The
average percentage juice yield ranges from 52 to 65%
while the average extraction efficiency ranges from
34 to 41% and the average percent extraction loss
ranges from 13 to 23% within all the age groups as
presented in Table 5 and Figure 2.
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
CONCLUSION
The ergonomics evaluation of a multi-purpose juice
extractor was carried out using 25 subjects within age
groups 15-20, 21-25, 26-30, 31-35, 36-40, 41 and
above with mid-ages 18, 23, 28, 33, 38 and 41 years
respectively.
The
evaluation
included
anthropometrics and physiological measurement of
the subjects in relation to performance evaluation of
the machine. Optimum juice yield of 65% was
obtained at age groups 21-25 years while optimum
extraction efficiency of 41% was obtained for age
group 15-20 years. Average mass of the subjects
ranged from 54-72 kg for age groups 15-20 and 31-35
years respectively, height ranged from 145-176 cm
for age groups 41 and above and 31-35 years
respectively while the arm length of the subjects
ranged from 66.3-76 cm for age groups 15-20 and 3640 years. The highest difference in blood pressure
before and after machine operation was obtained to
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[15]
[16]
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ergonomics evaluation of a manually operated multi

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