Comparison of infrared, flame and steam units for their use in plant protection

Comparison of infrared, flame and steam units
for their use in plant protection
M. N. RIFAI1, J. MILLER1, J. GADUŠ2, P. OTEPKA2, L. KOŠIK2
1Nova Scotia Agricultural College, Truro, Canada
2Slovak University of Agriculture, Nitra, Slovak Republic
ABSTRACT: The energy performance of infrared, flame-weeder & hot-steam units for pest and weed management were eva-
luated and compared. These thermal units were tested for ease of installation, adjustment of operation, safety and reliability. The
temperature development of these units was tested in a controlled environment. All three units used propane combustion as the
main source of energy to provide heat. Type K, 0.5 mm thermocouples were used for measuring temperature. The three thermal
units were passed over the thermocouples at groundspeeds of 1.5, 2.5 and 3.5 km/h. At a groundspeed of 1.5 km/h, the hot water-
steam unit reached the lowest temperature, 43.6°C. The infrared radiation and open flame units developed temperatures of 620.9ºC
and 186.1ºC respectively. The exposure time, fuel consumption, and energy input were calculated for each thermal unit. Propane
consumption was one of the main factors causing the significant difference in temperatures. The infrared radiation unit developed
the highest temperature, and it also had the highest propane consumption, 165.2 kg/ha at a groundspeed of 1.5 km/h. The hot wa-
ter-steam and open flame units had propane consumptions of 24.5 and 29.8 kg/ha respectively. The hot water-steam unit was the
safest of the thermal units because all of the flames were contained within the boiler. The hot water would not do any damage to
the soil and it would not spread rapidly across the field. The infrared unit can cause the greatest fire hazard and it is recommended
that some form of fire-extinguisher be present when this unit is in operation. The hot water-steam unit has the most potential in
pest management, and the infrared radiation unit is most suitable for pre-emergence weed control. The open flame unit reached
medium temperature among the thermal units. This thermal unit has the biggest potential in thermal weed and pest management.
It is the easiest to use of these thermal units, and the design allows for both nonselective and selective techniques, which makes it
the most adaptable for using in practical situations.
Keywords: thermal units; thermal pest control; thermal weed control; hot-steam; infrared; flaming
Conventional farming today involves using chemicals ded for human or animal consumption (PANNETON et
for controlling insect pests, weeds, and top-killing vege-
al. 2001). However, thermal control methods as a part of
table plants. The way chemicals interact with all factors physical methods involve a high consumption of fossil
around them is complicated, and it is difficult to predict fuels (ASCARD 1998). Thermal methods of controlling
what will happen in a field environment. Chemicals also weeds and pests are a type of physical control, which
remain in the soil and plants that are treated. These che-
have potential in organic agriculture. They leave no
micals can find their way into the crops grown in fields chemical residues in the soil or water, which seems to
treated with chemicals. People do not know exactly make them better for the environment. Since they leave
what types or concentrations of chemical pesticides and nothing behind, they affect only what enters their range
herbicides are present in the food they grow and buy at at the time of treatment. Organisms that enter a treated
stores. As a result of this, weed scientists need to consi-
area will not be affected, as they can be when insecti-
der alternative and integrated systems of weed manage-
cides and herbicides are used. Researchers have experi-
ment to reduce herbicide inputs and impacts (RIFAI et mented with several forms of thermal control, including
al. 2000).
flame, infrared radiation, and hot steam application.
Physical control methods are some of the alternative
The idea behind flame weeding is to kill weeds with
methods used in organic agriculture. Most physical an intensive wave of heat, without disturbing the soil or
control techniques have no detrimental environmental harming the crop root system. Broadcast flaming is used
effects. Physical control methods are generally limited before the crop emerges, but it usually cannot be used
to the site of treatment and the period during which they after the crop has emerged. Post-crop emergence fla-
are applied. Physical control methods bring no chemical ming is done selectively. The burners are angled toward
or biological substances into play and therefore do not the weeds and away from the crop. If the crop is more
leave undesirable residues on food commodities inten-
heat resistant than weeds or pests the broadcast flaming
This project has received the financial support from the Organic Agriculture Centre of Canada-NSERC-Research Projects.
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RES. AGR. ENG., 49, 2003 (2): 65–73
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can be used, but it has to be done very precisely and
carefully. ANDERSEN (1997) has developed a mathe-
matical model, which describes the heat dispersion from
the base of a plant in the directions outwards, upwards,
and along the row. Since all plants are composed of tiny
cells filled largely with water, a thin blast of heat direc-
0.2 m
ted at the stalk will boil the water within the cell. The
pressure generated by this expanding water will then Fig. 1. Set up of thermocouples during temperature detection
explode the cell itself, rupturing a cross section of the developed by thermal units: 1 – board; 2 – position of thermo-
stalk. When this happens, plant food and water cannot couples; 3 – connection between thermocouples and data logger;
move from roots to leaves and the plant withers and dies 4 – operation direction of the units
(RIFAI et al. 1996). In order to burst the cell membranes,
the plant tissue must be raised to a temperature of 100°C
for at least 0.1 s, but coagulation of proteins occurs
MATERIALS AND METHODS
between 50°C and 70°C (PARISH 1990). Bursting the
cell membranes is the goal of all thermal units when
Temperatures under thermal units were measured in
used for weed control.
a plant-free environment. The three thermal units were
The infrared and hot water-steam units do not direct based on hot water-steam, infrared radiation, and flame.
their thermal energy specifically toward the stalks of the Ground speeds of 1.5, 2.5 and 3.5 km/h were used for
weeds. They unleash the thermal energy in a more uni-
all the units, and 1.0 km/h was also used for the hot
formly distributed pattern. For this reason, they are used water-steam unit. Five 0.5 mm type-K thermocouples
primarily for pre-emergence, broadcast weed treatment. (chrome – aluminium) were set up in a line perpendicu-
When the flame thermal unit is set up for pre-emergence, lar to the operating direction of the machines at a height
broadcast weed treatment, it works similarly to the other of 10 mm above ground level. The thermocouples were
two thermal units. Some flamers have open burners and placed 0.15 m apart. The centre of application of each
others have burners under an insulated cover. BOND and machine was passed over the middle thermocouple
GRUNDY (2001) stated that shielding design is critical (Fig. 1). A data logger, connected to a laptop using the
to keep combustion gases close to the ground for as long program PC208W 3.01 (Data-logger Support Software,
as possible, and a burner angle between 22.5° and 45° to Campbell Scientific Inc., Logan, Utah, USA, 1998), was
the horizontal is ideal. Infrared radiation based thermal used to collect the data. The temperature was recorded
units have burners that heat ceramic and metal surfaces once every second for a period of 25 s as each unit pas-
that radiate heat toward the target. Hot steam based ther-
sed over the thermocouples. Five replications of each
mal units spray a mixture of hot water and steam from ground speed were performed for each thermal unit.
a distribution head onto the weeds.
After collecting data the exposure time (in seconds), fuel
The hot steam and flame based thermal units can be consumption (kg/ha, kg/h, l/h), and energy input (MJ/h)
easily adjusted for the purpose of insect pest control. were calculated for each thermal unit.
A few adjustments of the distribution head on the hot
steam unit allow the thermal energy to be focused on the
Hot water-steam unit
top leafy section of the plants where the insects are loca-
ted. The hot steam system is most effective when used
The model of hot water-steam nit used in this study
within an integrated program using a variety of cultural, is a prototype hot water-steam machine developed at
physical, mechanical, and biological tactics to solve the the Department of Engineering, Nova Scotia Agricul-
weed problem (RIFAI et al. 2002). In the case of the flame tural College, in Truro, Canada. The unit consists of
unit, there are several types of burners, which cause diffe-
rent heat distributions. Round burners cause long, narrow
flames suitable for selective in-row weeding in heat-sen-
sitive crops where precision is needed. Flat burners with
wide jet nozzles cause shorter, wider flames that result
in a more uniform heat distribution, which makes them
appropriate for pre-emergence, broadcast weeding. Flat
burners with narrow jet nozzles cause a longer, narrower
flame than those with wide jet nozzles, which makes
them appropriate for applications where heat penetration
through a given target is required, such as thermal top-kil-
ling of mature potato plants (LAGUË et al. 1997).
0.2 m
The objective of this study was to evaluate the hot
water-steam, infrared radiation, and flame thermal units Fig. 2. Distribution head of hot water-steam unit assigned for
based on operating temperature and energy input. In ad-
weed control: 1 – boom; 2 – perforated pipe; 3 – adjustable height
dition, safety and practicality were also considered.
of pipe; 4 – cover; 5 – ground; 6 – operating direction
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Fig. 3. Distribution head of hot water-
steam unit assigned for control of pests:
1 – perforated pipe; 2 – adjustable height
3
of pipe; 3 – hot water supply; 4 – outlet of
hot water and hot water steam; 5 – cover;
6 – adjustable side covers; 7 – boom;
8 – relieving wheel with adjustable high;
9 – top perforated pipe; 10 – operating
direction
0.2 m
a 900-litre water storage tank, a high pressure, hot water age tank or into the distribution head. The distribution
washing system, and a distribution head. This equip-
head is located on an arm that extends to the right, so
ment is mounted on a trailer, which can be attached to the distribution head is beyond the right tire of the trac-
a tractor. There is cold water in the storage tank. A little tor when the arm is in working position. The arm can
12-volt electric pump pumps the water through a filter to also be raised, so the hot water-steamer can be trans-
clean the water. The filtered water enters a high-pressure ported more easily. The distribution head is 1.0 m wide.
pump that is run by a gasoline-powered engine. There A basic scheme of a cross-section of the distribution
is a pressure-regulating valve for the pump, and a pres-
head assigned for weed control is shown in Fig. 2, and
sure gage with a maximum reading of 35.0 MPa. Next, a scheme of the distribution head assigned for pests con-
the water enters a heating coil in a boiler, and flames trol is shown in Fig. 3 (A and B).
around and underneath the heating coil heat the water.
All equipment for heating the water was produced by
Infrared radiation unit
Easy-Kleen Pressure Systems Ltd. Sussex, New Bruns-
wick, Canada (manufacturers of the Easy-Kleen™ Pres-
The infrared radiation unit used in this study is a KBL
sure Washer System). There is a propane tank mounted type HOAF crop debris burner, constructed at HOAF
on the back of the trailer with a pressure regulator on Apparatenfabriek B.V. Nijkerk, Holland. It mounts
it. This tank feeds propane to a burner at the bottom of on the back of a tractor. Its main components are two
the boiler. The boiler has a safety control unit on it to 116-litre propane tanks, a heavily insulated burning
prevent the burner from turning on unless there is water chamber, nine flat burners, and three fans. The propane
in the heating coil. The boiler also has a temperature tanks have relief valves on them, which will open if
sensor/control unit, which can maintain a temperature the tanks are filled to more than 80%. There is an out-
of up to 180°C, which was used in this study. There is let for each of the propane tanks that is controlled by
a safety pressure-relief valve just before the boiler, in an electric solenoid. These outlets lead to the propane
case there is a problem further along in the pipe. After line, which is a steel tube. Next in the propane line is
the boiler, there is a valve (control head) that will allow a pressure regulator, with the corresponding pressure
the hot water to be directed back into the water stor-
gage set on the front of the machine. The gage reads up
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0.2 m
Fig. 4. Burning chamber of infrared radiation unit: 1 – burner;
2 – propane supply; 3 – air supply; 4 – cover; 5 – gauze lining;
6 – chains; 7 – ground; 8 – operating direction
to 0.6 MPa, but 0.24 MPa was used in this study. After
the pressure regulator, the propane line goes through
another electric solenoid and finally to the burner heads.
The burner heads are located behind three fans at the
front of a 1.5-metres wide by 1.4-metres long burning
chamber. The top of the burning chamber has gauze
lining which radiates infrared radiation (ANONYMOUS
2002a). This infrared radiation, in combination with the
0.2 m
direct flames from the burners, raises the temperature
in the burning chamber to kill the weeds. The fans are Fig. 5. Burner segment of open flame unit: 1 – segment of fra-
electric, and a control panel that sits beside the driver me; 2 – steel rod; 3 – propane supply; 4 – burner; 5 – nozzle;
on the tractor controls them, the propane supply, and the 6 – flame; 7 – cover; 8 – ground; 9 – operating direction
activity of burners. The fans reduce the effect of wind
on the machine’s performance, and ensure the heat from or pests. The small amount of propane supplied by the
the burning chamber does not escape at the front end. pilot flame knob keeps the burners lit. Each of the six
The fans remain on for seven minutes after the propane burners has an individual gas flow valve with a safety
supply and burners are turned off. A basic scheme of the line on it that detects the flames in the burners. If the fla-
burning chamber of the HOAF infrared unit is shown in me in a burner goes out, a safety valve will close off the
Fig. 4.
propane line to that burner. The height and angle of the
burners are adjustable, and the height is maintained by
Open flame unit
wheels on a parallelogram support, which is pin connec-
ted to the main part of the machine. During this study,
The open flame thermal unit used in this study is the burners were positioned vertically 50 mm above the
a German-made Reinert propane flame weeder. It ground, and an operating pressure of 0.2 MPa was main-
mounts on the back of a tractor. Two 9.07 kg (20 lb) tained. A basic scheme of a segment of the flame unit is
propane tanks are partially immersed in a temperature shown in Fig. 5.
regulating water tank to prevent them from freezing.
A pressure regulator and gage attach to the propane
RESULTS AND DISCUSSION
tanks. The propane line runs along to an on/off safety
valve. After this valve, the line has a branch, which
Temperatures under three thermal units measured in
allows some of the propane to fuel a small flame in this study show high significant differences. The highest
a small chamber on the side of the water tank. There is temperatures were recorded under the infrared unit. The
a sensor that monitors the flame in this chamber, so if infrared unit also had the longest exposure time due to
the flame goes out, a valve will close off the propane its covered burning chamber. The hot water-steam unit
line. This branch also runs to a torch, which is attached had the second longest exposure time because of its
to the machine, and is used for manually lighting the covered distribution head, but it had the lowest tempera-
burners. The main propane line continues to a knob, ture. The flame treatment involved the shortest exposure
which controls the amount of propane released for the time, since it had no covers, and the second highest
purposes of lighting the burners and keeping a small temperatures. The maximum temperature for each unit
pilot flame. There is also a main propane control valve is shown in Table 1.
that allows a full flow of propane through the lines to
LAGUË et al. (1997) found their propane flamer
the burners. This valve is open during treatment, and caused temperatures of 150°C and 200°C at travel
can be closed to save propane when not treating weeds speeds of 3.5 km/h and 2.5 km/h, respectively. These
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Table 1. Average maximum temperature in °C by ground speed
1 meter long insulated cover on that flamer. The thermo-
and thermal unit
couples used in that study were 0.25 mm thick, which
is half the thickness of the thermocouples used in this
Driving speed
study. This may have had some effect on how quickly
(km/h/thermal unit)
Steam
Infrared
Flame
the temperature of the thermocouples could change, on
1.0
49.14
–
–
their sensitivity. If so, this could have a large impact on
1.5
43.64
620.87
186.13
the accuracy of the temperatures recorded for the flame
2.5
35.04
476.48
156.75
unit, since it had such a short exposure time. ASCARD
3.5
32.51
285.35
110.81
(1998) also found maximum temperatures of 300, 150,
and 100°C for the infrared radiation unit at 1.0, 2.0 and
temperatures were recorded at ground level with the 4.0 km/h, respectively. This is much lower than the
burners positioned 0.25 m above the thermocouples. numbers found in this study because the infrared unit
The burners were spaced 0.265 m apart (from center used in this study uses a combination of direct flames
to center). Laguë’s numbers are about 40°C higher and infrared radiation. The infrared unit in this study
than those found in this study. The burners used in this did not reach the temperatures developed by the flamer
study were spaced similarly, but they were positioned that ASCARD (1998) used, despite higher propane
0.20 m lower. The higher numbers found by LAGUË consumption.
et al. (1997) may be a result of several more factors.
The three thermal units show different temperature-
They used a different model burner, they recorded time patterns, shown in Figs. 6, 7 and 8. The maximum
the temperature eight times per second, and they used temperature for the infrared radiator was recorded when
a different method for the experiment. In this study, the back of the machine was passing over the thermo-
the thermocouples were stationary, and the thermal couples. This is because flames shot all the way back
units were passed over the thermocouples. LAGUË et through the burning chamber, so the whole burning
al. (1997) passed the thermocouples under the burners, chamber was hot. The thermocouples were heated for
which were mounted on a test bench.
1.44–3.36 seconds, depending upon driving speed, as
ASCARD (1998) found maximum temperatures of shown in Table 2, and then exposed to open air. The
900, 700, and 400°C for the flamer at 1.0, 2.0 and remaining time on the temperature-time curve, after the
4.0 km/h, respectively. This is much higher than the infrared unit passed by, and the thermocouples were in
numbers found in this study, probably because of the open air was not exposure time. It only represents the
cooling time of the thermocouples (ASCARD 1998).
Table 2. Exposure time in seconds for each ground speed and
Driving speed had a large effect on the temperature un-
thermal unit
der the infrared unit. Most of the effect was due to the
Driving speed
smaller exposure time, but the infrared unit also heated
(km/h/thermal unit)
Steam
Infrared
Flame
the thermocouples at a slower rate at a driving speed
of 3.5 km/h. The slope of the line in the first second
1.0
2.88
–
–
of heating is less than the slope of the other two lines,
1.5
1.92
3.36
0.07
as shown in Fig. 7. Since the temperature under the
2.5
1.15
2.02
0.04
infrared unit still reached 285°C at a ground speed of
3.5
0.82
1.44
0.03
3.5 km/h, the tractor could drive faster, and still reach
50
1,0 km/h
1.0 km/h
40
1,5 km/h
1.5 km/h
2,5 km/h
2.5 km/h
3,5 km/h
3.5 km/h
30
T
emperature (°C) Temperature (oC) 20
10
Fig. 6. Effects of hot water-steam unit on
-–4
0
4
8
12
16
20
temperatures at 10 mm above ground, at
Time (s)
various ground speeds
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Fig. 7. Effects of infrared unit on tempe-
600
ratures at 10 mm above ground, at various
1,5 km/h
ground speeds
500
2,5 km/h
3,5 km/h
)
400
300
p
e
r
a
t
u
r
e

(
o
C
T
e
m
200
T
emperature (°C)
100
0
-4
–
0
4
8
12
16
20
Time (s)
over 100°C. Driving the infrared unit at 1.5 km/h, and head was over the thermocouples. The back half of the
reaching temperatures of 621°C would be overkill in cover kept the temperature of the thermocouples close to
most situations.
the maximum temperature, but it was not quite as hot as
ASCARD (1998) found that the exposure time of the front half because the perforated pipe that discharges
a covered flame unit and an infrared unit were about four the hot water and steam is located in the front half of the
seconds at a speed of 1.0 km/h. These two thermal units cover. This pattern is most evident for the driving speed
were one meter long. ASCARD (1998) stated the highest of 1.0 km/h, as shown in Fig. 7, since it had the longest
temperature under the infrared unit was recorded when exposure time. The temperature under the hot water-
the back of the unit passes over the thermocouples, four steam unit was too low for bursting the membranes of
seconds after the initial recording. It was also found that the plant cells, but at 1.0 km/h, it was close to coagulat-
the maximum temperature under the covered flame unit ing some of the proteins.
was found after two seconds, which was at the end of
The exposure time for the open flame unit was less
the actual flames under the cover. The temperature then than 0.1 s because it had no cover to keep the heat near
decreased slowly until the back of the cover passed over the ground. This short exposure time resulted in a low
the thermocouples. The infrared unit in this study was temperature, relative to the infrared unit. Since tem-
a combination of these two units used by ASCARD perature was recorded once per second, the maximum
(1998). It had flames that reached to the back of the temperature could have easily been missed, as shown
burning chamber, so there was no drop in temperature in Fig. 8. The temperature is just high enough to burst
until it passed the thermocouples.
the plant membranes at a travel speed of 3.5 km/h, so
The maximum temperature under the hot water-steam the flame unit should not be driven any faster than this
unit was recorded when the middle of the distribution in the field under these operating conditions (gas pres-
200
1,5 km/h
) 150
2,5 km/h
3,5 km/h
100
p
e
r
a
t
u
r
e

(
º
C
T
e
m
50
0
Fig. 8. Effects of open flame unit on tempe-
-4
–
0
4
8
12
16
20
ratures at 10 mm above ground, at various
Time (s)
ground speeds
Time seconds
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Table 3. Propane consumption in kg/ha by ground speed for
Table 5. Energy input for each thermal unit
each thermal unit
Fuel
Propane
Gasoline
Total
Driving speed
(MJ/h)
(MJ/h)
(MJ/h)
(km/h/thermal unit)
Steam
Infrared
Flame
Heat content
50.402 MJ/kg
29.017 MJ/l
–
1.0
36.7
–
–
Steam
184.975
19.151
204.126
1.5
24.5
165.2
29.8
Flame
293.340
–
293.340
2.5
14.7
99.1
17.9
Infrared
1,935.437
–
1,935.437
3.5
10.5
70.8
12.8
sure of 0.2 MPa, burners 50 mm above the ground). input for these two thermal units. The infrared unit used
It might be a good idea to drive a little slower than far more energy than the other two thermal units, but it
3.5 km/h in case the presence of plants lowers the tem-
also caused the highest temperatures. The open flame
perature around their stalks; the leaves of larger plants unit used much less energy than the infrared unit while
may protect their stems.
still reaching high enough temperatures to kill weeds
Table 3 shows that propane was the only source of and insects. The hot water-steam unit used almost as
fuel for the flame and infrared thermal units. The hot much energy as the open flame unit, but it did not cause
water-steam unit consumed propane and gasoline, and temperatures high enough to kill weeds.
it also required water for its treatments. The propane
LAGUË et al. (1997) found that a flame weeder set
was used to heat the boiler, and the gasoline was needed up for pre-emergence broadcast flaming would use
to run the motor that pumped the water through the 3,300 and 4,500 MJ/ha of energy at a gas pressure of
boiler. From Table 4 the hot water-steam unit consumed 0.2 MPa and speeds of 3.5 and 2.5 km/h, respectively.
3.67 kg/h of propane, 0.66 l/h of gasoline, and 570 l/h This is considerably higher than the 645 and 903 MJ/ha
of water.
found with the open flame unit in this study. Energy
ASCARD (1998) stated the shielded flame unit used input is very closely linked to fuel consumption, so it
in that study consumed 6.82 kg/h of propane per meter is not surprising that LAGUË et al. (1997) found both
of working width at a gas pressure of 0.15 MPa. This is fuel consumption and energy input to be higher for
higher than the 4.48 kg/h per meter of working width at a flame unit at set operating conditions. The infrared unit
a gas pressure of 0.2 MPa found in this study. The dif-
used in this study may be closer linked to the flame unit
ference may simply be due to the different models used, used by LAGUË et al. (1997) than the flame unit used in
but there may have been a difference in the method used this study. At a gas pressure of 0.24 MPa and speeds of
to calculate the consumption, since ASCARD (1998) did 2.5 and 3.5 km/h, LAGUË et al. (1997) found the energy
not state how the consumption was calculated. In this applied to be 5,300 and 3,750 MJ/ha, respectively. The
study, the propane tank was weighed before the start of infrared unit in this study used 4,995 and 3,567 MJ/ha at
the experiment, and weighed again after the experiment the same operating parameters. The energy released by
was completed. The total running time of the experi-
the infrared unit seemed closer to that of the other flame
ment was recorded, and used to calculate the propane unit than the open flame unit in this study was found to
consumption in kilograms per hour.
be to the flame unit used by LAGUË et al. (1997).
The theoretical thermal energy input of each of the
These thermal units must do more than just heat the
thermal units was calculated using a gross heat content weeds and pests to a certain temperature and kill them.
of propane of 50.402 MJ/kg (LAGUË et al. 1997) and They must also be practical for use in real-world ap-
a gross heat content of gasoline of 29.017 MJ/l plications, not just some experiments. Therefore, it
(ANONYMOUS 2002b). Table 5 shows the amount of is necessary to consider the safety and practicality of
energy supplied by gasoline was small relative to that each thermal unit. The hot water-steam unit was the
supplied by propane for the hot water-steam unit, so it safest of the thermal units because all of the flames
did not have much effect on the total energy input for were contained within the boiler. The hot water would
the hot water-steam unit. Since propane was the only not do any damage to the soil and it would not spread
source of fuel for the open flame and infrared units, the rapidly across the field. The infrared unit reached the
energy supplied by the propane was the only energy highest temperature, so it was the greatest fire hazard. It
is recommended that some form of fire extinguisher be
Table 4. Fuel consumption of each thermal unit according to
present when this unit is in operation. The infrared unit
time
will remain hot for several minutes after it has been shut
Gasoline
Water
off, so the fire hazard remains until the burning chamber
Thermal unit
Propane
(kg/h)
(l/h)
(l/h)
cools down. The operator must be careful any time this
unit is in operation, especially near the edges of the field
Hot steam
3.67
0.66
570
where the chances of starting an out of control fire are
Flame
5.82
–
–
the greatest. The open flame unit is also a fire hazard
Infrared
38.4
–
–
because of the open fire, but it is easier to control be-
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cause it can be shut off quickly, and the exposure time until the fans shut off, so they can help cool the burning
and temperature are lower than with the infrared unit. chamber and keep the heat away from the tractor. With
Wind may cause problems when using the flame unit the infrared unit, everything is controlled while sitting
because it will blow the hot air towards the tractor when on the seat of the tractor.
the tractor is downwind. This is not as much of a factor
The open flame unit hooks up to the three-point hitch
with the infrared unit because it is equipped with fans to of the tractor, and there are no other connections. When
blow the hot air away from the tractor. Some parts of all turning on the flame unit, the valve on the propane tank
three thermal units will become very hot during use, so must be opened. Another source of fire is necessary for
a certain amount of caution is necessary when operat-
lighting the flame unit; a little torch is recommended.
ing them. Consult local regulations before using any of The burner for regulating the temperature of the water
these thermal units.
bath for the propane tank should be lighted next. There
The hot water-steam unit from the practical point of is a torch connected to the propane line, which can be
view has many separate components, which must work used to light the burners if another torch is not available,
together and be turned on in a certain order. A valve at but this torch will not light unless the above burner has
the bottom of the water tank must be open to allow the been lit. Each burner also has an on/off valve, which
water to flow through the line. The little 12V pump must must be opened in order to light the burner. The propane
be attached to the battery of the tractor and turned on. and the water in the water tank must be checked before
Next, the engine for the high-pressure pump should be using the flame unit. There is no need to wait for this
started. The valve for the propane tank must be opened thermal unit to heat. The only things that can be done
before igniting the burner in the boiler. The tractor from the seat of the tractor are raising the three-point
should be on while the hot water-steam unit is being hitch, and switching the burners between a small pilot
activated, so the battery of the tractor will not run out. flame and treatment flame. If the flame in one of the
The gasoline in the motor, the water in the water tank, burners goes out, someone needs to manually light it
and the propane in the propane tank must be monitored again. This is most likely to happen when the burners
along with the other things on the tractor. After the boil-
are turned to a low pilot flame, and it is windy, or when
er is turned on, it is necessary to wait for the boiler to the main propane flow valve is turned on too quickly.
heat up and the application head must be put into work-
Sometimes, the flame can be very hard to see, especially
ing position before starting treatment. From this point, on hot, sunny days.
the treatment can be done from the seat of the tractor.
The driver can turn a valve on the control head, which is
References
positioned behind the seat of the tractor, to direct the hot
water back to the water tank or to the distribution head. ANDERSEN J., 1997. Experimental trials and modeling of
When turning off the hot water-steam unit, it should be
hydrogen and propane burners for use in selective flaming.
done in the opposite order to that listed above. It may be
Biol. Agric. Hort., 14: 207–219.
quite difficult to maneuver the trailer in confined areas.
ANONYMOUS, 2002a. HOAF Crop Debris Burners for Weed
When hooking up the infrared unit on a tractor, a con-
Control in Agriculture and Horticulture. URL: http://www.ls
trol panel must be mounted beside the seat of the tractor
systemsltd.demon.co.uk/hoafkb.html
and attached to the battery of the tractor and the front ANONYMOUS, 2002b. Thermal Conversion Factors. URL: http:
of the infrared unit. When turning on the infrared unit,
//www.eia.doe.gov/emeu/aer/pdf/pages/sec13_1.pdf
turn the tractor on, and flip two switches on the control ASCARD J., 1998. Comparison of flaming and infrared radiation
panel. Flip the switch for the propane supply, first, then
techniques for thermal weed control. Weed Res., 38: 69–76.
the switch for lighting the burners. The fans operate au-
BOND W., GRUNDY A.C., 2001. Non-chemical weed
tomatically. Lighting burners may take some time. The
management in organic farming systems. Weed Res., 41:
propane supply will shut off if the burners do not light
383–405.
after approximately ten seconds. When this happens, the LAGUË C., GILL J., LEHOUX N., PELOQUIN G., 1997.
switch must be turned off and back on again in order to
Engineering performances of propane flamers used for weed,
turn on the propane supply again. If the burners will not
insect pest, and plant disease control. Appl. Eng. Agric., 13
light for a long time, it may be a good idea to allow the
(1): 7–16.
propane that has already been released to disperse, es-
PANNETON B., VINCENT C., FLEURAT-LESSARD F., 2001.
pecially if it is being lit inside. Ensure nobody is stand-
Plant Protection and Physical Control Methods the Need to
ing at the back of the infrared unit when it is being lit
Protect Crop Plants. In: VINCENT C., PANNETON B.,
because the propane may accumulate at the back of the
FLEURAT-LESSARD F. (eds.), Physical Control Methods
unit and catch fire. The gauges on the propane tanks
in Plant Protection. Berlin, Heidelberg, New York, Springer-
should be checked before turning on the infrared unit,
Verlag: 329.
and the covers over the pressure gauges should be put PARISH S., 1990. A review of non-chemical weed control
back before using the unit. Once the burners are lighted,
techniques. Biol. Agric. Hort., 7: 117–137.
time should be allowed for the burning chamber to heat, RIFAI M.N., LACKO-BARTOŠOVÁ M., BRUNCLÍK P.,
so it will radiate infrared radiation. After the burners are
2000. Alternative methods of weed control in apple orchards.
shut off, it is a good idea to leave the tractor running
Pakistan. Bio. Sci., 3: 933–938.
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RIFAI M.N., LACKO-BARTOŠOVÁ M., PUŠKAROVÁ V.,
three types of mulch on weeds in apple orchards. J. Environ.
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RIFAI M.N., ASTATKIE T., LACKO-BARTOŠOVÁ M.,
Received for publication November 11, 2002
GADUŠ J., 2002. Effect of two different thermal units and
Accepted after corrections February 10, 2003
Porovnanie infra?ervenej, plame?ovej a parnej jednotky pri ich využití
v ochrane rastlín
ABSTRAKT: Objektom hodnotenia a vzájomného porovnania boli energetické výkony jednotiek na ni?enie škodlivého hmyzu
a buriny využívajúce infra?ervený lú?, plame? a prúd horúcej pary. Testy teplotných jednotiek boli zamerané na posúdenie
jednoduchosti inštalácie, nastavenia chodu, bezpe?nosti a spo?ahlivosti. Vyvíjanie tepla u týchto jednotiek bolo testované
v riadenom prostredí. Ako hlavný zdroj energie na získavanie tepla u všetkých troch jednotiek slúžilo spa?ovanie propánu. Na
meranie teploty boli použité termo?lánky typu K 0,5 mm. Prejazd uvedených troch jednotiek miestom, kde boli inštalované
termo?lánky, bol pri rýchlostiach 1,5, 2,5 a 3,5 km/h. Pri základnej rýchlosti 1,5 km/h jednotka s prúdom horúcej pary dosiahla
najnižšiu teplotu 43,6 °C. Jednotka s infra?ervenou radiáciou a jednotka využívajúca otvorený plame? vyvinuli teploty 620,9 °C
a 186,1 °C. Expozi?ný ?as, spotreba paliva a energetický vstup boli po?ítané jednotlivo pre každú teplotnú jednotku. Spotreba
propánu bola jedným z hlavných faktorov spôsobujúcich signifikantné rozdiely v teplotách. Jednotka infra?ervenej radiácie
vyvinula najvyššiu teplotu a mala aj najvyššiu spotrebu propánu 165,2 kg/ha pri základnej rýchlosti 1,5 km/h. Jednotky prúdu
horúcej pary a otvoreného plame?a mali spotrebu propánu 24,5 a 29,8 kg/ha v uvedenom poradí. Jednotka prúdu horúcej pary
bola najbezpe?nejšou z teplotných jednotiek, pretože priamy plame? bol prevádzkovaný v kotlu. Horúca para nespôsobuje
žiadne poškodenie zeminy a ani sa nemôže rýchlo šíri? naprie? po?om. Infra?ervená jednotka môže spôsobi? najvä?šie riziko
požiaru a odporú?a sa, aby bolo po?as prevádzky k dispozícii zariadenie na hasenie požiaru. Jednotka prúdu horúcej pary má
najvä?ší potenciál pre ni?enie škodlivého hmyzu a infra?ervená radia?ná jednotka sa javí ako najvhodnejšia na ni?enie buriny.
Jednotka s otvoreným plame?om dosiahla strednú teplotu spomedzi teplotných jednotiek. Táto termálna jednotka má najvä?ší
potenciál pri tepelnom ni?ení buriny a škodlivého hmyzu. Je najjednoduchšia na použitie a jej konštrukcia dovo?uje prevádzku
pri obidvoch režimoch – neselektívnom a selektívnom, ?o ju robí najprispôsobivejšou pre aplikáciu v praktických situáciách.
K?ú?ové slová: termálne jednotky; tepelné ni?enie škodlivého hmyzu; tepelné ni?enie buriny; horúci prúd pary; infra?ervený;
plame?
Corresponding author:
Doc. Ing. JÁN GADUŠ, Ph.D., Slovenská po?nohospodárska univerzita, Mechaniza?ná fakulta, Katedra mechaniky a strojníctva,
Trieda A. Hlinku 2, 949 76 Nitra, Slovenská republika
tel. + fax: + 421 37 733 60 73, e-mail: Jan.Gadus@uniag.sk
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