Ergonomical Evaluation of a Hand Operated Paddy Winnower by Women Workers

Abstract

A hand operated paddy winnower was developed by Central Rice Research Institute, Cuttack. The winnower
was ergonomically evaluated using 12 subjects. Two women workers are required for the operation of this
winnower, one for cranking the blower and other for feeding the threshed material and collection of grain. The
mean heart rate of the women workers and their output were measured to evaluate the winnower. The mean
heart rate of women workers during operation was found to be 112 beats/min. The energy expenditure rate in
operation of the equipment was 10.7 kJ/min. The average output was found to be 242 kg grain/h and winnowing
efficiency was found to be 88.36%. The equipment developed was found to be suitable for operation by women workers as the heart rate, work pulse value and energy expenditure rate are within the acceptable limits.

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Journal
of
AgriculturalEngineering
Vol.
44(4): October-December, 2007
Ergonomical Evaluation
of
aHand Operated Paddy
WinnowerbyWomen Workers
S.
"Po
Singh
J
and
L P
GUt?
ABSTRACT
Ahand operated paddy winnower was developed by Central Rice Research Institute, Cuttack. The winnower
was ergonomically evaluated using
12
subjects. Two women workers are required for the operation
of
this
winnower, one for crankingthe blower and other for feeding the threshed material and collection
of
grain. The
mean heart rate
of
the women workers and their output were measured to evaluate the winnower. The mean
heart rate
of
women workers during operation was found to be 112 beats/min. The energy expenditure rate in
operation
ofthe
equipment was 10.7 kJ/min. The average output was found to be 242 kg grain/h and winnowing
efficiency was found to be 88.36%. The equipment developed was found to be suitable for operation by
women workers as the heart rate, work pulse value and energy expenditure rate are within the acceptable limits.
Rice
is
one
of
the most importantcrops
of
world amongst
all cereal crops being astaple food and farm women are
involved
in
most
of
its
farming operations. The percentage
of
female workers in agricultural work force in the
country
is
expected to increase from 39% in year 2001
to
42%, 45% and 55% in year 2007, 2012 and 2025,
respectively (Banthia, 2004; National Commission on
Population, 2006). As ergonomical characteristics
of
men
and women are different, there is aneed to give due
consideration to capabilities and limitations
of
women
workers while developing various tools and equipment.
In
many part
of
India, paddy threshing is still done either
with animal treading or manually by beating on wooden
plank or stone. After that the winnowing
is
done with
help
of
winnowing basket using natural wind. This
is
a
very simple and effective method but the output
is
low,
Le., 40-45 kg per h(Anonymous, 1997). Also many
times, one has to wait for wind currents. Presently, hand/
pedal
operated
winnowing
fans
(winnowers)
are
commercially available and also used
by
the farmers.
The fan blades
of
such winnower are not
in
casing that
may be aone
of
the source
of
accident.
It
is
observed
that women workers rarely operate this equipment,
because
of
high initial
torque
requirement. During
winnowing with this equipment, lighter materials are
blown far away to agreater distance that forces farmers
to
winnow the threshed material in open space.
In
case
of
paddy, winnowing efficiency may also be affected
due to immature grain that generally lies very near to
clean grain, which are separated manually. Keeping this
in
view, ahand operated paddy winnower was developed
by Central Rice Research Institute (CRRI), Cuttack to
facilitate the winnowing work further. About 40% farm
women are involved in winnowing operation in Madhya
Pradesh (Singh, 2006). Ergonomical evaluation
of
equipment was carried out at Bhopal to see its suitability
for farm women in terms
of
physiological work load,
anthropometrical data, strength data, safety features in
equipment and performance
of
equipment.
Physiological cost
of
operation
is
expressed in terms
of
heart
rate
and
oxygen
consumption
rate.
Oxygen
consumption
;:lata
is the correct variable for measuring
the physiological work load but is difficult to measure
while performing the task hence, indirect method, Le.,
heart rate
is
measured. However, oxygen uptake gives
the absolute load butthe heart rate gives the relative load,
which in many instances may be just as important or
even more important.
It
is
known that not only the oxygen
transport will influence heart rate but also the climatic
conditions will contribute. As for agiven calorie output
the heart rate
'Nill
be higher when cranking in ahot and
humid environment. This fact speaks in favour
of
using
heart
rate
as
an
index
of
the
physiological
load
(Christensen, 1962). Similar type
of
finding was also
reported by Thakur and Das (1978). Therefore, several
research workers (Balasankari etal., 2003; Burger, 1969;
Gite, 1991; Ghugare et al., 1991; Gite, 2003; Singh et
al.,
2004,
2005 &
2006)
have
used
heart
rate for
assessment
of
physiological work load
of
the workers.
uSenior Scientist
(FMP)
and Project Coordinator, respectively Central Institute
of
Agricultur.1l Engineering, Nabi Bagh, Bhopal- 462 038
(Email:
spsinghyhd@yahoo.co.in)

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October-December, 2007 Ergonomical Evaluation
of
aHand Operated Paddy Winnower by Women Workers
MATERIALSAND
METHODS
CRRI
hand
operated
paddy
winnower
consists
of
trapezoidal frame, volute case, fan blades, hopper, handle
and gear mechanism (Fig. I). Four rectangular blades
are mounted on
19
mm shaft and the blower blades were
housed in avolute casing as it changes velocity head
into pressure head. The feed from hopper is adjusted
depending on the type
of
feed through inclined feed
control plate. The blower outlet is just above the grain
outlet so that air coming from blower strikes the feed
material and foreign materials being lighter than grain
goes out through the outlet. Clean grain comes out from
grain outlet.
It
is
mounted on trapezoidal frame. Handle
is
mounted with another shaft attached with large spur
gear. Further this gear
is
attached with small size spur
gear mounted on blower shaft. The winnower weight
is
36
kg
and the capacity
of
the hopper is 8
kg.
Two women
workers were engaged during its operation. One worker
was for cranking the equipment and the other was for
feeding the material and collecting the clean material.
The study was conducted at CIAE
in
farm shed during
year 2006 with
12
farm women subjects. The material
for winnowing was obtained after threshing
of
paddy
crop (Kanti variety) with pedal operated paddy thresher.
Such subjects were selected whose stature lied
in
between
the values
of
5th to 95th percentile
of
Madhya Pradesh
farm women
Le.,
142.7 cm to 159.7 cm (CIAE, 2005).
All the women workers were trained
in
operation
of
the
equipment before start
of
the actual experiment. Before
starting the experiment, age, stature and weight
of
each
subject were recorded. The body weight
of
the workers
varied in between 42 kg to 65
kg.
The lean body mass
of
the subjects was calculated using Hume's (1966)
formula [(0.29569x body weight, kg) +0.41873 xbody
height, cm)- 43.2933). This formula is for the
wo~en
having age more than 30 years. All the participated
subjects were right handed except one. The physical
conditions
of
all the workers were good. The related
anthropometric data
of
Madhya Pradesh farmwomen
is
given
in
Table 1(CIAE, 2005).
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Fig.
I: Hand winnower
Table I.Anthropometric
data
offarm
women
of
Madhya Pradesh(CIAE 2005)
Particulars Anthropometrical Data
5th Percentile 95th Percentile
Weight, kg
Height, em
Metacarpal III height,
mm
Bideltoid width, mm
Sitting popliteal height,
mm
Hip breadth, mm
Acromial height, mm
Torque strength with preferred hand in standing posture, N-m
33.2
142.7
602
331
352
272
1183
20.2
57.2
159.7
709
429
426
354
1342
40.0
68

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S.
P.
Singh and L P Gite
During the experiment, ambient conditions (dry bulb
temperature, wet bulbtemperature, relative humidity and
air speed), crank rotation, number
of
times
of
feeding,
number
of
times
of
change
of
hands during cranking
and percentage
of
straw (foreign matter) in material used
for winnowing and
in
cleaned material were noted. The
duration
of
trial was
of
10
min. Psychrometer was used
to measure the data with regard to dry bulb temperature,
wet bulb temperature and relative humidity during the
experiment. Air speed was also measured using hot wire
anemometer. Using suitable fixture, torque required in
rotation
of
crank
of
winnower was measured by torque
meter (EEL make).
Aheartrate monitor (Polar Electro
OY,
Finland; model S
810 i) was used for
recording
heart rate
of
women
workers
during
the
course
of
study.
The
monitor
consisted
of
achest strap and awrist watchtype receiver.
Before measuring the heart rate data aworker was given
warming up exercise
of
brisk walking for
15
minutes
followed by arest
of
30 min. After that the heart rate
monitor was fixed on the
chest
of
worker.
Data
for
resting, working and recovery heart rate were taken for
the period
of
10
min, 30 min and 10 min, respectively.
The recorded data in the receiver
of
the monitor were
downloaded daily in the computerthrough interface after
completion
of
the work. The heart rate data from 6th
min onwards
of
work
of
each worker was considered
for calculating the heart rate as it is considered that the
worker's heart rate gets stable after 3-5 min (Le Blanc,
1957). The heart rate data for resting, working (6th -
JAE :44(4)
30th min) and recovery periods were processed to get
the mean values
of
heart rate
of
workers. The work
pulse value was calculated
by
subtractingthe mean heart
rate during work with the mean heart rate
of
worker
during rest. Each day the experiment was conducted
from
lOam
to 2
pIp..
The oxygen consumption rate
of
worker was estimated from her heart rate during work
based
on
equation
developed
by
(Singh,
2007)
{Y
(oxygen consumption, l/min)= 0.0155 *X(heart
rate)-
1.2248}. The oxygen consumption (I/min) was converted
in kJ
(1
litre
02
=20.93
kJ) for
calculating
energy
expenditure. The workers were asked for their opinion
about the operation
of
the equipment. The summarized
data
of
the experiment are given in Table
2.
RESULTS AND DISCUSSION
Ergonomical
Evaluation
Mean (+ S.D) age, height and weight
of
the workers
were 39.4 +8.9 years, 152.0 +2.8 cm and 46.8 +6.6
kg, respectively. Mean lean body mass was found to be
34.1 kg. Dry bulb temperature, relative humidity and air
speed during the experiment were 28.1 +
1.3
°C,
38.8 +
5.5% and 0.4 +0.1 mis, respectively. The mean heart
rate
of
women workers in operation
of
the equipment
for cleaning the threshed paddy material was 112 beats!
min. Their mean work pulse value was
31
beats/min
which was within the acceptable limit
of
40 beats!min
(Saha etal., 1979). The oxygen consumptiqn rate (OCR)
of
women workers was estimated as 0.511 l/min Le.,
Table
2.
Dataon ergonomicalevaluation
of
handoperatedpaddy winnower
Particulars
Weight
of
machine,
kg
Handle height from ground, mm
Chaff percentage
in
material to be cleaned
Immature grain percentage in material to be cleaned
Chaff percentage
in
clean grain
Immature grain percentage
in
clean grain
Percent grain coming in blown material
Crank rotation, rpm
Blower rpm
Air velocity at outlet for cleaning foreign matter, m/s
Winnowing efficiency, %(weight basis)
Output, kg/h (clean grain)
Torque at
65
rpm, N-m
Working heart rate (WHR), beats/min
Work
pulse
(~
HR), beats/min
69
Values
36
570
2.2
22.2
0.25
11.4
1.35
65.3 +3.0
326.3 +15.2
3.2 +0.3
88.36
242.2 +41.4
5.27+0.8
111.9+3.0
30.5
+8.0

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October-December,
2007
Ergonomical Evaluation
of
aHand Operated Paddy Winnower by Women Workers
32.9%
of
aerobic capacity. The
OCR
value was also
found within the acceptable limit
of
40%
of
aerobic
capacity
(Nag
and
Chatterjee,
1981).
The
energy
expenditure rate was found to be 10.7 kJ/min. As per
the criteria given by
Nag
and Chatterjee, 1981, the
workload in terms
of
oxygen consumption rate was
of
moderate heavy category. Normal rest pauses may be
provided to the workers for day long operation as heart
rate and oxygen consumption rate values are within the
acceptable limit. Two women workers were required
during operation
of
equipment for winnowing purpose.
One worker was for operating the equipment and the
other for feeding the threshed grain material, collecting
the grain from outlet etc.
Overall,
the
workers felt
comfortable in operatingthe equipment. The equipment
was found suitable for operation by farm women as the
hear rate, work pulse value and energy expenditure rate
are within acceptable limit.
The handle height
of
equipment from ground was 570
mm
which
is
on lower side to their Metacarpal
III
height,
ie., 5th percentile value
of602
mm. Present handle height
at downward position forced the workers to bend their
back during cranking operation. Therefore, the handle
height at downward position from ground should not be
less than 602 mm. The space available for worker to
operate the handle
in
standing posture is 100 mm only as
against the required space
of
215 mm
(half
of
95th
percentile Bideltoid breadth, i.e., 429/2= 215 mm). The
limited space forced the workers to stand atrear
of
handle
and to put one hand on cover
of
gear
or
fan for support.
It
is
recommended to provide achair/ stool
of
352 mm
height (5th percentile sitting popliteal height), which
wiII
provide comfort to worker in cranking and may also
help
in
increasingoutput. The width
of
chair/stool should
be 354 mm (95th percentile hip breadth sitting). The
hopper height for feeding the material should not be more
than 5th percentile
of
acromial height,
Le.
1183 mm so
that at the time
of
feeding the material, worker's hand
shouldnot be lifted above acromial height. Keeping hopper
capacity same, the height
of
hopper may be reduced by
increasing the side slope
of
hopper.
Performance
of
Winnower
The moisture content ofthreshed grain material was 18%
(db). Chaffand immature grain percentage in the material
was 2.2 and 22.2, respectively. The maximum distance
covered by blown material was up
to
1.4 m. The hopper
was loaded for 32 times in an hour.
The
output
of
equipment was 242 kg clean grain per hat 65 rpm. The
clean grain obtained from equipment was having 0.25%
chaff
and 11.4% immature grain as against 2.2% and
22.2%, respectively. The winnowing efficiency in terms
of
clean grain was 88.36%. The ratio
of
large gear to
small gearwas I
:5.
The average crank speed
of
equipment
during its operation was 65 rpm. Atthis rpm, the obtained
air speed (3.2 m/s) was found suitablefor cleaning paddy
grain.
To
rotate the handle
of
equipment with one hand in
standing posture, the torque required was 5.3 N-m at 65
rpm. The 5th Percentile value for the maximum torque
strength
of
Madhya Pradesh farm women is 20.2 N-m
(CIAE, 2005). Thus, the torque requirement was within
the acceptable limit
000%
of
maximum torque strength
of
preferred hand in standing posture as suggested by
(van
Wely,
1970).
There was
no
hook for hanging sack holder at grain
outlet and needs to be provided for comfort to workers.
Threshed paddy materials were having
chaff
and dust
that affects continuous flow
of
material for cleaning from
hopper.
To
overcome this, an agitator either mechanical
or vibratory type may be provided.
Most
of
the moving parts
of
the equipment were covered
except the grain outlet side. This needs to be covered
with perforated cover as it sucks loose cloth (Sari)
of
workers during feeding
of
material.
The workers were having experience
of
working with
similarequipment though they were mostly illiterate. The
operation
of
equipment is simple in nature and they could
pickup the specific technical skiII easily.
CONCLUSIONS
Ahand operated paddy winnower was ergonomically
evaluated with
12
farm women for cleaning threshed
material
of
paddy.
The
equipment
was operated
by
women workers in standingposture. The torque required
in
cranking
the
blower
was
5.3
N-m
at
65
rpm.
Winnower should be operated at 65 rpm. Output
in
terms
of
clean paddy grain/h was 242 kg with winnowing
efficiency
of88.4%
at 3.2 m/s air velocity that is obtained
at outlet for separating foreign matter.Mean heart rate
and work pulse during cleaning paddy grain was found
to be 112 beats/min and 3I beats/min, respectively. The
energy expenditure rate in operation
of
the equipment
was 10.7 kJ/min. The equipment developed was found
to be suitable for operation by women workers and it
needs to be promoted as the heart rate, work pulse value
70

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S.
P.
Singh and L P Gite
and energy expenditure rate are within the acceptable
limits.
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