report easydry m500: assembly, operation and … drawing hot furnace exhaust gasses through them and...

REPORT

Demonstration Construction and

Training for Formal and Informal

(Artisan) Fabricators of the

EasyDry M500

AflaSTOP: Storage and Drying

For Aflatoxin Prevention

July 2015

REPORT

EasyDry M500: Assembly,

Operation and Maintenance

Manual

AflaSTOP: Storage and Drying

For Aflatoxin Prevention

February 2016

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Prepared by:

Marius Rossouw

Design Engineer

[email protected]

catapultdesign.org | Billions of people lack access to life's basic needs. We design and implement

human-centered products to help them thrive.

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 between Catapult Design and Agribusiness Systems

International (ASI) through the AflaSTOP project to identify potential drying technology suited to

support post-harvest handling devices for maize smallholder farmers.

mailto:[email protected]

http://catapultdesign.org/

http://www.acdivoca.org/aflastop-publications

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TABLE OF CONTENTS

1. Product Overview ................................................................................................................................. 5

2. Safety warning ..................................................................................................................................... 6

3. EasyDry M500 Components ................................................................................................................ 7

4. EasyDry M500 Assembly Procedure ................................................................................................... 8

5. EasyDry M500 Operation .................................................................................................................. 12

6. Troubleshooting ................................................................................................................................. 15

7. Maintenance schedule ........................................................................................................................ 16

LIST OF TABLES

Table 1: EasyDry M500 attributes ................................................................................................................ 6

Table 2: EasyDry M500 Components ........................................................................................................... 7

Table 3: EasyDry M500 Assembly Procedure .............................................................................................. 8

Table 4: EasyDry M500 Operation ............................................................................................................. 12

Table 5: EasyDry M500 Troubleshooting .................................................................................................. 15

Table 6: Potable Shallow-bed Batch Dryer Maintenance Schedule ........................................................... 16

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1. Product Overview

The EasyDry M500 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 motor bikes, pickup, truck, trailer or hand cart 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. Five (5) to six (6) bags of 90 kg (+/- 500 kg) of “wet” maize 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.

Drying Air Supply Unit

Shallow-bed

Cool Ambient

Air

Warm Drying Air

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 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 Components

Table 2: EasyDry M500 Components

1 x EasyDry M500

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. EasyDry M500 Assembly Procedure Table 3: EasyDry M500 Assembly Procedure

Step 1: Mobilization.

Transport the dryer to suitable drying location. Select

relatively even terrain – 3 m x 4 m with the 4 m length

of the operating area established in the direction of the

prevailing wind.

Step 2: Site selection and area preparation.

Prepare the drying area by removing any object that may

puncture the plenum. Place the drying air supply unit

and plenum (with sides folded inwards to identify its

footprint) with the drying air supply unit down wind of

the plenum.

Step 3: Shallow-bed assembly.

Unfold one collapsible bed support frame (90º) and

place at one corner of the plenum.

Step 4: Interlocking the bed support frames.

Repeat Step 3 and connect the first unfolded bedframe

with a second by slotting the pin of the first bedframe

into the receiving catch of the second bedframe.

Step 5: Completing the bed support frame.

Repeat Step 4 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 6: Securing the plenum.

Connect the sidewalls of the plenum to the inside of the

bed support frame by hooking the perimeter rope of the

plenum onto the bed support frame’s corresponding

clips.

Prevailing wind direction

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Step 7: Placing the first collapsible bed panel.

Smooth out the canvas to ensure minimal creasing by

making sure the bottom corners are close to the bed

support frame’s legs. Unfold collapsible bed panel 1

(with the overlap flat bar) and place it into the bed

support frame and plenum. Collapse the panel slightly to

reduce the span and place the bed panel into the plenum

with the underside of the perimeter angle iron slightly

above the bed support frame square tubing before

lowering the center of the panel, pinching the canvas in

the process between the panel angle iron and bed

support frame square tubing.

Step 8: Proper panel nesting.

Ensure that collapsible bed panel 1 nests 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.

Step 9: Supporting the first bed panel.

Place the center pole under collapsible bed panel 1 to

support the center. Ensure correct installation by

orienting the center pole horizontal square tubing,

nesting under the horizontal angle iron edge and not the

hinges.

Step 10: Placing the second collapsible bed panel.

Place collapsible bed panel 2 in the remaining opening

by repeating Step 7 with the inner angle iron

overlapping the protruding flat bar of collapsible bed

panel 1.

Flat bar

overlap

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Step 11: Proper panel nesting.

Ensure the maximum contact between the collapsible

bed panels and the bed support frame by confirming that

the bed support frame sits well within the perimeter

angle iron of the collapsible bed panels, especially at the

pin connections.

Step 12*: Rainfly installation

Install the rainfly by placing it over the center pole and

connecting all the corresponding cornets to the bed

support frame corner stanchions.

*Step 12 Rainfly to be installed after maize is loaded on the

bed only if rain is eminent.

Step 13: Ensuring a seal between the furnace and

the ground

Place the drying air supply unit within connecting

distance from the erected shallow-bed. Test-fit the

plenum’s duct connection to the drying air supply unit

and confirm that the ground underneath the furnace is

even enough so that no gaps between the underside of

the furnace and the ground are visible. If gaps are

visible, build soil up around edges to create the seal.

This is required to prevent flames from leaking out the

top as all combustion air will be introduced from above,

drawing the flame through the heat exchanger.

Step 14: Securing the plenum connecting duct.

Fill the engine with sufficient fuel (at least 3 liters for

one batch), check the oil and lubricate all the bearings

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. Connect the plenum’s duct to

the receiving connecting ring on the drying air supply

unit and tighten the connection strap securely. Adjust the

drying air supply unit’s location to minimize creasing of

the connecting duct to prevent pressure losses.

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Step 15: Installing the engine assembly

Remove the engine assembly from its transportation

stowage by removing the padlock and locking pin and

install it onto the receiving support angles on the

opposite side of the furnace. Be sure the replace the

padlock as this will prevent the connecting pin from

coming undone during operation.

Step 16: Erecting the chimney.

Erect the chimney by pivoting it upward from its

stowing position until it rests securely on the dyer body

under its own weight.

Step 17: Installing the v-belt.

Install the v-belt onto both fan and engine pulleys by

lifting the back end of the engine to reduce the span.

Releasing the engine will tension the v-belt. Ensure that

the engine hangs freely on the v-belt with no

obstructions underneath.

Caution: A moving v-belt poses potential danger as

loose clothing or appendages may get caught between

the v-belt and the pulley.

Step 18: Placing the cob drying basket.

Remove the cob drying basket from its stowing location

within the furnace and place it on top of the chimney.

The EasyDry M500 is now ready for operation.

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5. EasyDry M500 Operation Table 4: EasyDry M500 Operation

Step 1: Loading the maize.

Load the shallow-bed with about 500 kg (5 – 6 x 90 kg

bags) of maize to be dried. Best practice is to spread

each bag before adding the next. This mixes the maize

to promote more homogenous drying. Level the maize

and ensure that the grain depth is equal (within 1 cm)

throughout the maize bed. This is necessary to ensure

consistent airflow throughout the bed.

Step 2: Filling the cob basket with wet cobs.

Remove, fill and return the cob drying basket from/to

the top of the chimney. Dry cobs are needed to fuel the

furnace efficiently and the initial ignition of the furnace

using other flammable material will assist in supplying

dry cobs if none are available.

Step 3: Igniting the furnace.

Open the ash cleanout door downstream of the heat

exchanger to allow for combustion air when igniting the

fire. Prepare and light a fire in the furnace with stover,

grass, twigs, paper, etc. and slowly add dry cobs until a

well-established fire with sufficient cobs alit remains.

Close the ash cleanout door once again, creating the

required seal between the ground and the furnace.

Step 4: Starting the engine.

Start the engine by raising the backend of the assembly

with one hand (this will minimize the starting torque

requirements of the engine) and pulling the staring cord

with the other hand. Release the engine assembly slowly

to engage the v-belt and subsequent fans only once the

engine has reached a steady idling speed. Initial

throttling may be required to overcome the fan inertia.

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Step 5: Engine RPM adjustment - airflow indicator.

Be sure to reduce the RPMs to the required rate (as

specified by the airflow indicator) once the fans are up

to speed. Adjust the engine RPM throttle to have the

airspeed indicator needle point to the notch in the needle

protection member.

Step 6: Feeding the furnace.

It is very important that the furnace is fed 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 low furnace temperatures and

longer drying times. 12-15 kg/hour (1/2 large bag) cob

feed rate is desired.

Caution: The furnace body of the dryer gets extremely

hot and poses danger of severe burns upon contact.

Step 7: Viewing the furnace for flames.

Always ensure that the furnace is firing as hot as

possible by confirming flames through the peepholes on

the side of the furnace body.

Step 8: Stirring the cobs to intorduce oxagen.

If no flames are visable either the furnace cob level is

too low or the cob combustion has moved into the

charcoaling stage. This is not desirable as flames are

needed to heat the heat exchanger effectifly. Stir the

charcoaled cobs and add fresh dry cos to ignate flames

again.

Notch

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Step 9: Drying cobs in the cob drying basket.

Continuously rotate cobs from the cob drying basket to

the furnace. Cobs are considered dry enough if the break

with limited flex. Excess dry cobs can be placed in a bag

or on the ground to be used to start the furnace at the

next batch. A lid is provided to protect the cob drying

operation in the event of rain. The lid should remain

open if not raining for best drying results.

Step 10: Processing the maize.

Stir the maize every 30 min using an implement (bucket,

rake, etc.) or by hand. Ensure that maize from the

bottom of the grain bed is replaced with maize from the

top. A proven method to achieve this is to mix in a

circle, filling maize from the top into voids where maize

was removed from the bottom. Be careful not to damage

the bed panel coffee mesh if implements are used. Be

sure to level the maize bed again after processing and

confirm equal maize bed depths.

Step 11: Stopping the drying operation between

batches.

When the desired maize moisture is achieved, stop

feeding the furnace and stop the engine. If refueling is

required, wait until the majority of cobs within the

furnace have been consumed with no visible flames

before opening the fuel container. Using a bucket or by

hand, offload the maize into empty maize bags. Again,

use caution not the damage the bed coffee mesh when

scooping maize. Lift the furnace end of the drying air

supply unit and remove any charcoaled cobs that may

have accumulated in the furnace body. This is required

to ensure that no obstructions exist in the way of the

combustion gasses flowing through the heat exchanger.

Step 12: Maintenance between batches.

Open the ash removal door downstream of the heat

exchanger and remove any ash that may have

accumulated during the drying operation. Allow the

furnace to die down before refueling the engine (if

required). Grease all the bearings if required.

Step 13: Demobilization

Disassembly is executed in the reverse assembly order.

Only return the engine assembly to its stowing position

once the adjacent metal has sufficiently cooled. When

loading, make sure that the plenum and collapsible bed

panels are protected from sharp objects to prevent

damage.

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6. Troubleshooting Table 5: EasyDry M500 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

of uneven airflow)

Ensure that the maize bed is level

and equal maize thickness

throughout the bed.

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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Refill petrol and

check oil

7. Maintenance schedule Table 6: Potable Shallow-bed Batch Dryer Maintenance Schedule

Daily Schedule:

Refill petrol @ 0.45 l/hour of operation

Remove ash and charcoal

Clean plenum

Weekly Schedule:

Lubricate bearings

Clean fire grate

Check plenum and repair holes if required

Check bed mesh and repair holes if required

Monthly Schedule:

Service engine.

Check v-belt.

Yearly Schedule:

Check and replace HX panels if required.

Check and replace furnace body if required.

Check and replace fire grate if required.

Check and replace bed mesh.

Clean ash from

furnace body and

exhaust chamber

Clean plenum from dirt before stowing away

Lubricate

bearings

Clean

fire

grate

Inspect

plenum and

rainfly for

tears

Inspect bed

Coffee mesh

Check and replace

furnace body and

grate if burned out

Check and replace HX

panels if burned out by

removing the rear panel Check and replace

V-belt if worn through

Service engine

by refilling oil

and cleaning fuel

filter

report easydry m500: assembly, operation and … drawing hot furnace exhaust gasses through them and...

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