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REPORT
Demonstration Construction and
Training for Formal and Informal
(Artisan) Fabricators of the
Portable Shallow-Bed Batch Dryer
AflaSTOP: Storage and Drying
For Aflatoxin Prevention
July 2015
Performance Testing Procedure for
the AflaSTOP EasyDry M500
Dryer
AflaSTOP: Storage and Drying
For Aflatoxin Prevention
April 2016
PAGE 2 OF 16
PAGE 3 OF 16
The AflaSTOP: Storage and Drying for Aflatoxin Prevention (AflaSTOP) project is identifying the most promising storage options to arrest the growth of aflatoxin and designing viable drying options that will allow smallholder farmers to dry their grain to safe storage levels. The project works to ensure that businesses operating in Africa are able to provide these devices to smallholder farmers. It is jointly implemented by ACDI/VOCA and its affiliate Agribusiness Systems International (ASI) under the direction of Meridian Institute. For more information on AflaSTOP and other key reports and resources, visit: www.acdivoca.org/aflastop-publications. This work was carried out as a partnership with Marius Rossouw and Catapult Design to identify potential drying technology suited to support post-harvest handling devices for maize smallholder farmers. For any inquiries about the EasyDry M500, please contact us at [email protected] A video guide on “Important Fabrication Details” can also be found at XXXXX.
PAGE 4 OF 16
TABLE OF CONTENTS
1. Product Overview .................................................................................................................................. 5
2. Safety warning....................................................................................................................................... 6
3. EasyDry M500 Dryer Components ....................................................................................................... 7
4. Performance Testing Procedure – Visual Inspection ............................................................................ 8
5. Performance Testing Procedure – Active Evaluation ......................................................................... 13
6. Troubleshooting .................................................................................................................................. 14
LIST OF TABLES
Table 1: EasyDry M500 Attributes ............................................................................................................... 6 Table 2: EasyDry M500 Dryer Components ................................................................................................ 7 Table 3: EasyDry M500 Performance Testing Procedure – Visual Inspection ............................................ 8 Table 4: EasyDry M500 Performance Testing Procedure – Active Evaluation ......................................... 13 Table 5: EasyDry M500 Dryer Troubleshooting ........................................................................................ 14
PAGE 5 OF 16
1. Product Overview
The EasyDry M500 dryer is a portable, on-farm drying solution that enables smallholder farmers to dry
their maize down post-harvest to the recommended moisture levels. It offers a solution that closely
resembles the traditional method of lying shelled maize out in the sun to dry, with the major difference in
that forced hot air is used as the drying mechanism and is capable of operating under inclement weather
conditions since it relies on burning biomass to generate the required heat, and not the sun.
The dryer is either transported (as a service) on two motorbikes, a pickup truck, a trailer, or handcart to or
stored at the location (as an on-farm investment) where maize is shelled or dried. The dryer can be
assembled within 10 minutes by erecting the modular shallow-bed and connecting it to the drying air
supply unit. ± 500 Kg of “wet” maize (±10 x 50 kg bags, ±5 ½ x 90 kg bags, ±4 ¼ x 120 kg bags - ±
50kgs will not effect drying performance) are loaded onto the shallow-bed and the furnace is ignited. The
heated clean air needed for drying is generated through convection heat transfer by blowing ambient air
over heated heat exchanger (HX) channels. The HX channels are heated by drawing hot furnace exhaust
gasses through them and out the chimney. The hot exhaust gasses are constantly generated by steadily
burning fuel (maize cobs) in the downdraft furnace. The heated air is blown into a canvas plenum with
maize suspended on a perforated mesh bed above it. The air pressure builds up in the canvas plenum and
forces heated air past the maize kernels with surface moisture drawn away. The maize is stirred at 30 min
intervals to allow the moisture trapped in the lower layers closest to the heated air to escape. Once dry,
the maize is offloaded for storage. The dryer can dry the 500 kg “wet” maize (~20% moisture content)
down a safe storage moisture content of +/- 13.5% within four (4) hours (+/- an hour depending on the
actual moisture content of the maize) and 500 kg of maize of ~16% moisture content to below 13.5%
within 90 minutes. Multiple batches can be handled per day depending on starting moisture levels and
operating hours. A video guide on “Important Fabrication Details” can also be found at XXXXX.
Drying Air Supply Unit
Shallow-bed
Saturated Drying Air
PAGE 6 OF 16
Table 1: EasyDry M500 Attributes
Attribute Complete Dryer Drying Air Supply Unit Shallow-bed Unit
Tangible
Size - Operation
2.4 m (W) x 3.3 m (L) x 1.8 m (H)
1.0 m (W) x 1.6 m (L) x 1.8 m (H)
1.9 m (W) x 2.5 m (L) x 1.2 m (H)
Size - Transportation
1.5 m (W) x 1.5 m (L) x 0.9 m (H)
0.5 m (W) x 1.3 (L) m x 0.9 m
(H)
1.0 m (W) x 1.5 m (L) x 0.9 m
(H)
Color/s Various Agricultural colors – Heat
resistant
Stock PVC and Canvas
Agricultural colors - Bed
Weight 190 kg 120 kg 70 kg
Material composition Local, low cost material to promote
sustainability
Mild Steel, Cast Iron,
Plastic, Copper, Aluminum
Mild Steel, Canvas, Rubber,
Leather, Plastic
Finish Stock, Painted/
Painted Heat Resistant
Stock, Painted/
Painted Heat Resistant
Stock, Painted
Intangible
Efficiency/Capacity
Dry 500 kg wet maize (+/- 20%
moisture content) down to 13.5% in +/-
four (4) hours (+/- 2 hours depending
on actual moisture content of the
maize)
Consumes 12 - 15 kg cobs
and 450 ml petrol/hour.
Recommended capacity of
500 kg
Projected
Durability/Longevity* 5 years 5 years 5 years**
Projected Maintenance
Schedule
Lubricate bearings and
check engine oil weekly,
Service engine monthly,
Replace HX panels every 2
years.
Repair lesions in canvas and
coffee mesh as they occur.
* Durability/Longevity with proper care, maintenance and associated cost.
** Canvas plenum and coffee mesh may wear through first and may need repair/replacing more often.
2. Safety warning The EasyDry M500 dryer is a dangerous piece of agricultural equipment that consists of moving
components and hot surfaces, posing possible injury risks. Extreme caution is required around the furnace
area, the engine and v-belt assemblies. Children should be kept away from the aforementioned
components at all times with bystanders minimized around these areas where possible. Children should
be kept away at all times while the dryer is in operation.
PAGE 7 OF 16
3. EasyDry M500 Dryer Components
Table 2: EasyDry M500 Dryer Components
1 x EasyDry M500 Dryer
1 x Shallow-bed
1 x Drying Air Supply Unit
2 x Collapsible Bed Panels
1 x Cob Drying Basket
2 x Transportation Handles
1 x V-belt
1 x Connection Pin
1 x Rainfly
1 x Canvas Plenum
1 x Main Drying Unit Body
1 x Padlock
1 x 5.5 HP Engine
1 x Center Support Post
4 x Collapsible Support Frames
PAGE 8 OF 16
4. Performance Testing Procedure – Visual Inspection Table 3: EasyDry M500 Performance Testing Procedure – Visual Inspection
Step 1: Initial inspection of all the components.
Inspect the EasyDry M500 dryer to insure all of the
components are present and in good working condition.
Pay close attention to surface finishes and ensure that all
external metal surfaces are properly painted including
the primary supply fan and surrounding scroll. Verify
that all hinge and pinned components work properly and
that all components intended to nest inside others do so
with limited effort. Inspect all bolted connections to
make sure that they have spring washers/lock nuts and
that they are securely tightened. Check each bearing to
make sure that the shaft grub screws and grease nipples
(and protection if applicable) are installed and facing
upwards.
Step 2: Initial inspection of the drying air supply
unit – fan assembly tolerances and construction.
Check to confirm that each fan has less than a ¼
clearance to its respective scroll yet does not make
contact with any part of its supporting structure when
turned by hand. Ensure that all of the fan blades are
welded completely to the fan hubs with hubs welded to
the shafts and that the fans are balanced. Check each
shaft and pulley for any excentrisities and make sure that
each pulley is secured to the shaft propperly with its
shear key installed. Confirm that all bearings are
lubricated with high temperature (150 ºC) lithium
grease. Ensure that the internal air supply fan bearing is
sufficiently lubricated by viewing the bearing through
the spaces of the heat exchanger panels.
Step 3: Initial inspection of the drying air supply
unit – Heat Exchanger (HX) tolerances and
construction.
Check the HX panels at the furnace and exhaust ends to
make sure that all the panels are parallel, equally spaced
(~1/2” apart) and spot welded in at least 2 places on
each side. Similarly confirm that the HX panels are
parallel, equally spaced apart at ~1” with no welding.
Check to make sure that there are not visible gaps
between HX channel panels or the main frame of the
dryer body (if possible) or the removable cover plate.
Step 4: Plenum inspection and fit.
Inspect the plenum to ensure that it is sealed at all the
seams and reinforced in the proper locations. Confirm
that the perimeter rope and the connecting duct with the
strap are installed. Check to make sure that each sub
component of the plenum are made from the proper
material: Base = PE shipping, Sides = PVC, Connecting
duct = Canvas and the Rainfly = Raincoat. Make sure
that the connecting duct strap is made from cotton or
leather and not something plastic that will melt during
operation.
½”
1”
PAGE 9 OF 16
Step 5: Shallow-bed support frame inspection.
Unfold each collapsible bed support frame and confirm
that they only open to or just under 90º. Ensure that the
hinges work correctly and that the two horizontal
support members at the same level when collapsed.
Compare each bed support member to another and
confirm that they are all equal sizes and lengths. Check
the top end of the vertical rainfly support to make sure
that it has an end cap and that it has soft edged and will
not puncture the rainfly when installed. Place each
support frame at a corner of the plenum ready for
installation.
Step 6: Interlocking the bed support frames.
Inspect each bed support frame’s connecting pins and
catches to ensure that one receives the others with
minimal effort. Ensure that the pin on each bed support
member is located in the same position and
perpendicular to the horizontal support member and that
the groves in the receiving catches are parallel. This will
ensure that two connected bed support frames are
straight when connected. Repeat Step 6 until the bed
support frame is complete. Ensure that all connecting
pins are properly engaged and that all corners are as
square as possible.
Step 7: Inspecting the plenum fit.
After connecting the sidewalls of the plenum to the
inside of the bed support frame, confirm that the plenum
sits snug inside the support frame’s legs and that the
support frame’s clips are softened and will not damage
the perimeter rope during operation. Make sure that the
perimeter rope is as tight as possible without damaging
the canvas or the bed supports. Smooth out the canvas
and confirm minimal creasing by checking that the
bottom corners of the plenum are close to the bed
support frame’s legs.
Step 8: Inspecting the collapsible bed panels.
Inspect both collapsible bed panels and confirm that all
the edger and corners that will interface with the plenum
has been rounded and softened to prevent damage.
Check the coffee mesh for damage and make sure that
no wires are protruding beyond the panels edges as his
will damage the plenum and my cause injury. Confirm
that one of the panels has additional flat bar installed in
the correct location. Check that the inner corner of each
bed has been cut to allow the center post to nest within
them.
Flat bar
overlap
PAGE 10 OF 16
Step 9: Inspect how the collapsible bed panels fit.
Install both bed panels and center post and confirm that
the panels’ total expanded lengths match that of the bed
support frame. Ensure that collapsible bed panels nest
properly onto the bed support frame with the maximum
overlap of the perimeter angle iron resting on the bed
support square tubing on 3 sides. A ½” gap should
remain between the inner vertical edge of the perimeter
panel angle iron and the bed support square tubing.
Confirm that the inner corners of each bed allows for the
center post to fit snugly but not too tight in the middle of
the assembly. Ensure that no gaps exist large enough for
maize to fall into the plenum within the entire assembly.
Step 10: Rainfly inspection
Inspect the rainfly for damage and confirm that all the
seams are properly sealed. Install the rainfly and confirm
that it fits the erected shallow-bed. Check that all the
seams are properly sealed and for damage. The top
corners of the rainfly should be larger than the bed
support vertical members with about ½”* if the shallow-
bed is assembled on level ground. The bottom of the
rainfly should be larger than the plenum perimeter rope
by at least 2” on each side. This is necessary to allow air
to escape during rain since the air pressure will inflate
the rainfly, allowing air to escape out the bottom.
*This excess will change as the terrain does since an elevation
at the center connections of the bed support frame connection
will increase the span between the vertical member s and
decrease this overage. The opposite is also true for a
depression in this area.
Step 11: Ensuring a seals between the ground and
the shallow-bed
Inspect the bottom of the furnace and confirm that the
frunace seal flatbars are installed. Connect the canvas
connecting duct and ensure that it fits easily around the
receiving connection scroll with minimal effort. The
connecting duct should not be larger than ½”. Tigten the
strap and confirm that the d-ring mechanism work
properly.
Step 12: Inspecting the engine assembly
Check that the engine has sufficient oil and remove the
assembly from its transportation stowage. Confirm that
is has a padlock and that the pin is easily removable.
Reinstall it onto the receiving support angles on the
opposite side of the furnace and confirm that is installs
with minimal effort yet has minimal play in the pinned
connection.
Furnace seal frame
PAGE 11 OF 16
Step 13: Inspecting the chimney and stamping the
SN and QC numbers.
Stamp the corresponding serial and quality control
numbers onto the dryer body below the chimney support
member using a number punch set.
Erect the chimney by pivoting it upward from its
stowing position until it rests securely on the dyer body
under its own weight. Confirm that the hinges work
properly and that the chimney seals properly on the
dryer body. Engage the sliding mechanism at the base of
the chimney and confirm that it latches fully and stays in
place until disengaged intentionally.
Step 14: Installing the v-belt.
Install the v-belt onto both fan and engine pulleys and
confirm that the engine assembly hangs level under its
own weight without making contact with the ground.
Confirm the V-belt type corresponds with that of the
pulleys (either type A or B) to ensure the belt does not
slip when it rains. Confirm that all of the pulleys are
aligned within ½” and that the belt runs in a straight line.
Check the pulley and make sure that the shear key is
installed and that it is spot welded to the engine shaft.
Confirm that the bolt securing the pulley to the shaft is
tightened and that the threads are not damaged by over
tightening.
Step 15: Inspecting the cob-drying basket.
Remove the cob-drying basket from its stowing location
within the furnace and place it on top of the chimney.
Confirm that it releases easily from the furnace cavity
without catching. Check that the legs slot into the
receiving holds within the chimney easily and that all of
the feet make simultaneous contact to avoid instability.
Inspect the lid hinge and confirm that the lid is able to
fold back 270°.
Step 16: Confirming the batch capacity.
Load the shallow-bed with about 500 kg (±10 x 50 kg
bags, ±5 ½ x 90 kg bags, ±4 ¼ x 120 kg bags) of maize
and confirm that it fits on the bed with at least 2”
remaining at the top of the plenum sidewalls once
leveled. Listen for maize falling through into the
plenum.
QC number
Serial number
PAGE 12 OF 16
Step 17: Ensuring consistent furnace fuel.
Remove, fill and return the cob drying basket from/to
the top of the chimney. When firing the furnace, make
sure that cobs are fed from the basket into the furnace.
Using similarly dry cobs when testing the furnace and
HX efficiencies on various dryers is important so that
varying performance is not influenced by the cob
moisture levels.
Step 18: Inspecting the ash cleanout door and
installing the thermometer.
Inspect the ash cleanout door and ensure that is seals
properly with the dryer body. Install a thermometer on
the opposite, adjacent end of the plenum in the drying
air cavity under the maize bed. Make sure that the
thermometer end does not make contact with the plenum
sides or the underside of the maize bed. The intension
here is to measure the drying air temperature in the
plenum before it passes through the maize bed.
Step 19: Calibrating the airflow requirement
- Part 1.
Place the drying air supply unit on level ground and
ensure that the airflow indicator plate (the 4” x 4” plate
welded to the thin rod going across the heat exchanger)
is just touching the HX panels and not leaning away or
against it. Mark the needle position in the protective half
circle before the engine is fired with a hacksaw or cold
chisel to indicate to “off” position.
Step 20: Inspecting the engine mounting.
Prep the furnace and fill the engine with petrol to a point
that can be used as a reference to determine how much
furl was consumed during the 30 min testing period.
Confirm the engine fuel cap has the proper rubber gasket
installed. Confirm that there is enough space between
the engine and the furnace body to allow for the engine
to be lifted to such an extent where the belt tension is
reduced and the engine starts with minimal effort. Start
the engine and confirm that is runs smoothly without
any moving assemblies making contact with their
support structures. Turn the engine off and light the
furnace. Restart the engine and reduce the rpms close
idle.
Thermometer
“Off” position
PAGE 13 OF 16
5. Performance Testing Procedure – Active Evaluation Table 4: EasyDry M500 Performance Testing Procedure – Active Evaluation
Step 1: Calibrating the airflow requirement
- Part 2.
.
Once the engine is running comfortably and at an idle,
take an A crisp, uncreased A 4 piece of paper and place
it on the flat, equal thickness maize bed. This piece of
paper should just “float” above the maize bed. If it
doesn’t then increase the engine rpms until the paper can
be pushed across the bed with minimum effort. If it
hovers with excessive movement then decrease the rpms
until it is just suspended on a small cushion of air above
but very close to the maize. Once this has been achieved
you will notice that the airflow indicator needle has
moved away from the “off” position”. Once again, mark
the “on” position on the protective half circle. This will
provide the operator with a guide on what airflow is
required regardless of the maize bed depth without
having to take a piece of paper to the field. The
important thing to remember is that the slower the air,
the hotter it is and the faster it will dry wet maize. The
flipside is also true where if the airflow is not sufficient
to push through the maze then drying will take longer.
Step 3: Tracking performance-testing metrics.
The following performance testing metrics should be
tracked:
Plenum temperatures
Fuel consumption of the engine
Feed the furnace at a constant cob feed rate with cobs
that have been dried/preheated in the cob-drying basket.
At no point should the cob level fall below the top level
of the furnace grate. Under and over feeding will result
in lower furnace temperatures, HX and ultimately drying
air temperatures. Always ensure that the furnace is firing
as hot as possible by confirming flames through the
peepholes on the side of the furnace body. Track the
plenum and ambient temperatures in 5 min intervals
through 30 min op continuous operation. A difference
of at least 35° C should be witnessed between the
ambient and the drying air within the 30 min
performance testing period. Upon completion of the 30
min testing period, stop the engine and wait for the
furnace flames to die out before refilling the engine to
the reference point and noting the fuel consumption. The
engine should not have used more than 250 ml of fuel
during a 30 min period. Note: Tracking fuel over such a
short period of time is often difficult since small
amounts are being consumed and a reliable method to
conduct in the field-testing on such small amounts is
lacking. The better approach would be to track the fuel
consumption over the entire drying cycle and divide it
by the drying time.
Step 2: Documenting performance-testing metrics.
Two performance-testing sheets are provided in and
Excel file named –Appendix A: Performance Testing
Worksheets.
The first is used as a visual inspection checklist with the
second to document the EasyDry M500’s configuration
and to track the plenum temperature and the fuel
consumption of the 30 min testing period.
“On” position
A 4 paper
PAGE 14 OF 16
Step 4: Disassembling and preparing the
EasyDry M500 for transport.
.
Once performace testing has been completed and the
furnace has had some time to cool down, diassemble the
EasyDry M500 in the reverse order of assembly and
return it to its original condition (engine stowed, cob
basket nested and chimney collapsed). Only return the
engine assembly to its stowing position once the
adjacent metal has sufficiently cooled. Fold the plenum
and rainfly neatly and place them in the enigne shipping
box along with the v-belt, engine manual and tools and a
operating manual. Write the corresponding serial
number on the box to ensure that components do not get
mixed up if multiple units are being perfromance tested
at the same time.
6. Troubleshooting A video guide on “Important Fabrication Details” can also be found at XXXXX.
Table 5: EasyDry M500 Dryer Troubleshooting
Shallow-bed
Symptom Probable Causes Solution/s
1. Collapsible bed panel 1
does not fit properly.
Improper bed support frame
assembly.
Ensure that the all the collapsible
bed support frames are connected
properly and that the frame as a
whole is square.
2. Collapsible bed panel 2
does not fit properly.
Improper collapsible bed panel
1 installation.
Ensure that collapsible bed panel 1 is
nested properly.
3. Maize leaking into the
plenum.
Gaps between Collapsible bed
panel 1 and 2 and/or bed
support frame.
Ensure that collapsible bed panel 2
has a sufficient overlap with
collapsible bed panel 1 and that the
perimeter of both panels has
sufficient overlap with the bed
support frame.
4. Uneven drying throughout
the maize bed.
Uneven airflow through he
maize bed (uneven chaff
accumulation is an indication
Ensure that the maize bed is level
and equal maize thickness
throughout the bed.
PAGE 15 OF 16
of uneven airflow)
Drying air supply unit
5. V-belt is slipping. Insufficient belt tension. Ensure that the engine assembly
hangs freely with only the v-belt
supporting it.
6. Noisy bearings. Insufficient lubrication. Ensure all bearing are lubricated at
all times.
7. Fire escaping out the top of
the furnace post-initial
furnace startup.
Insufficient seal between the
bottom of the furnace and the
ground, ash buildup under the
fire grate or the ash cleanout
door is open.
Confirm that a good seal is achieved
between the furnace bottom and the
ground and that no combustion air is
being introduces from the bottom.
Remove any ash/charcoal that may
be obstruction airflow and ensure the
ash cleanout door is closed.
8. Excessive smoke from the
chimney.
Insufficient combustion air or
wet fuel source. Furnace is
over fueled or the ash cleanout
door is open. Cobs are too wet
for efficient combustion.
Ensure that the proper amount of dry
cobs (from the cob drying basket) is
fed to the furnace at regular
intervals. Cob levels should always
lie around the top of the fire grate.
9. Longer than expected
drying times.
Low drying air temperature, in
insufficient airflow or higher
than anticipated grain moisture
content.
Ensure that the furnace is always
fired as hot as possible. Confirm
constant flaming through the heat
exchanger through the peepholes on
the side of the furnace. Stir the
furnace and introduce more cobs if
limited flames are visible. Ensure
that sufficient drying air passes
through the maize bed by ensuring
the engine rpms are set to the
derided rate as indicated by the
airflow indicator.
PAGE 16 OF 16