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

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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 info@easydry.org A video guide on “Important Fabrication Details” can also be found at XXXXX.

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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

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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

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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.

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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

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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”

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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

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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

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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

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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

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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

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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.

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