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1- Project

Community development and social work (University of Nairobi)

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KENYA COAST NATIONAL POLYTECHNIC.

TRADE PROJECT.

AUTOMATIC MAIZE DRYING.

DEPARTMENT: MECHANICAL ENGINEERING.

COURSE: DIPLOMA IN MECHANICAL ENGEERING - PLANT OPTION.

COURSE CODE: 2402.

SUBJECT CODE: 306.

CENTER CODE: 106120.

INDEX NUMBER: 1061200649.

INSTITUTION: KENYA COAST NATIONAL POLYTECHNIC.

KNEC SERIES: OCT/NOV 2020.

PRESENTED TO: KENYA NATIONAL EXAMINATION COUNCIL IN PARTIAL

FULFILMENT FOR THE AWARD OF DIPLOMA IN MECHANICAL

ENGINEERING – PLANT OPTION.

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DECLARATION
THE KENYA NATIONAL EXAMINATION COUCIL

DECLARATION FOR POST SCHOOLS TECHNICAL EXAMINATIONS

NAME OF PROJECT: AUTOMATIC MAIZE DYRING

This project is my original work and has not been presented for award of any certificate in any
other college or university

Signature:………………… date:……………..

Name: OGUTU P. ODHIAMBO.

Index number:1061200649

This project has been submitted for examination with my approval as the polytechnic
supervisor.

Signature:…………………… date:…………………..

Name: OMARI K.O

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EXECUTIVE SUMMARY.
The purpose of this project is to ensure that maize is dried effectively with minimum time
possible using industrial waste product (exhaust gas) as a byproduct. This project is also
designed to ensure that drying temperature can be monitored and controlled digitally. The
temperature can be controlled by a micro controller which is programmed with set points to
ensure that the temperature in the drying room is within the set points. This can be achieved even
without presence of humans since it is automated.

The system is designed to absorb heat from the exhaust gas and use it for drying purpose; this is
achieved by use of heat exchangers whose tubes are coiled to ensure that its efficiency is high by
ensuring maximum absorption of heat from the exhaust gas. The air that goes to the heat
exchanger is from air receiver which is fed with air from air compressor. The air is filtered and
pressure regulated before it reaches the heat exchanger.

This heated air in the coils is then taken to the drying house where it is used for drying the maize
grain. This is achieved by use of blowers, the blowers ensure that air is uniformly supplied to the
drying beds containing maize grains and are placed strategically for the maize drying process.
The hot moist air that has been used n drying leaves through the vents in the roofs which have
suction fans.

Maintenance of the system is very simple and easy since and it does not need regular
replacement of parts.

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ACKNOWLEDGEMENT
I am very grateful to the almighty God for giving me good health, guidance, and the strength to
do my business plan work. My sincere thanks also go to my parents and my cousin Felix Otieno
for their moral, social and financial support during writing of the business plan.
I also appreciate my friends Mr. Ronny and Mr. Omoruli for their corrections and support.
Thanks to my business plan supervisor, Mr. Kennedy Omari for guidance and support she gave
during the writing of this business plan.
May God Bless you all.

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DEDICATION.
This project I dedicated to my loving family and friends for their sincere support and the
encouragement they extended to me towards writing and completion of this project.

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TABLE OF CONTENTS
DECLARATION........................................................................................................................................ii
EXECUTIVE SUMMARY........................................................................................................................iii
ACKNOWLEDGEMENT..........................................................................................................................iv
DEDICATION............................................................................................................................................v
CHAPTER ONE..........................................................................................................................................1
1.1 Introduction...........................................................................................................................................1
1.2 Problem statement.................................................................................................................................1
1.3 Objectives..............................................................................................................................................1
1.4 Project scope..........................................................................................................................................1
1.5 Limitation of the project........................................................................................................................2
CHAPTER TWO.........................................................................................................................................3
LITERATURE REVIEW............................................................................................................................3
1.1 INTRODUCTION.................................................................................................................................3
1.2 Related work..........................................................................................................................................4
1.3 Theoretical statement.............................................................................................................................4
1.4 Conclusion.............................................................................................................................................4
CHAPTER THREE.....................................................................................................................................5
DESIGN ANALYSIS AND METHODOLOGY.........................................................................................5
3.1 Compressors..........................................................................................................................................5
3.2 Selection of compressor.........................................................................................................................5
3.3 Intermittent services..............................................................................................................................5
3.4 Compressor stage, Double stage compressor.........................................................................................5
3.5 Factors considered when selecting air compressor................................................................................6
3.6 Receiver sizing......................................................................................................................................8
3.7 Recommended receiver capacity...........................................................................................................9
3.8 Sizing of the pipes.................................................................................................................................9
3.9 Installation of pipe works....................................................................................................................11
3.9.1 Accessibility of the valves................................................................................................................11

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3.9.2 Bracketing, anchoring and expansion...............................................................................................11

3.9.3 Bracketing........................................................................................................................................12
CHAPTER FOUR.....................................................................................................................................19
4.0 MAINTENANCE OF THE SYSTEM.................................................................................................19
4.1 Maintenance........................................................................................................................................19
4.2 Phased preventive maintenance...........................................................................................................19
4.3 Planned preventive maintenance..........................................................................................................21
4.4 Compressor driving belt......................................................................................................................22
4.5 Plant troubleshooting...........................................................................................................................22
4.6 Plant maintenance schedule.................................................................................................................24
4.7 Material and costing............................................................................................................................25
CONCLUSION.........................................................................................................................................26
RECOMMENDATION.............................................................................................................................26
REFERENCES..........................................................................................................................................27
APPENDICES...........................................................................................................................................28

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CHAPTER ONE

1.1 Introduction
This project is designed to help in drying grain farm produce more so maize and millet before
they are stored and or processed. Drying of the maize is normally and majorly done using the sun
i.e. sun drying.

Sun drying tends be slow method of drying maize especially where there is too much produce
besides it is unreliable method. This can lead to spoilage before or during storage.

1.2 Problem statement.

To curb food shortage there is need for food security and food security is all about proper storage
of the food which will ensure that maize is protected against aflatoxin. Maize from the farm
needs to be well dried before storage and this can only be achieved when drying conditions are
met. The drying conditions vary from seed maize to processing maize.

When drying efficiency is increased, one of the conditions shall have been met and this will
improve food security ensuring that the spoilage during storage is reduced or eliminated.

1.3 Objectives.
The general objective of the system is to reduce the maize drying time by 50% and also a system
which will kill microorganisms that end up destroying the seeds during storage. Most
microorganisms cannot survive at temperature of 60 degrees centigrade.

1) To dry wetter grain than they can be dried with natural air flow or low temperature drier.
2) To ensure that maize is properly and efficiently dried before storage or processing.
3) Allows more time for post-harvest field work.

1.4 Project scope.

The aim of the project is to provide a real time solution to curb food insecurity by ensuring that
wastage of farm produce due to aflatoxin is minimized and also that produce from the farm can
be processed as fast as possible. To achieve the above, industrial waste heat can be used.

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1.5 Limitation of the project.

Since our system solely depends on the industrial waste heat it can only operate when the
industrial machines are running or functioning

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CHAPTER TWO

LITERATURE REVIEW.

1.1 INTRODUCTION.
Air has long been used as a medium of heat transfer and in carrying humidity. High air flow rate
and higher temperature lowers the humidity in that particular air hence in turn this leads to
increased drying speed since it will pick more humidity from the surrounding. It can be used in
natural convection or forced convection to transfer heat for drying. There has been use of hot air
in drying maize using furnaces but this requires powering the furnace. One of the greatest
challenges for agriculture in Africa are aflatoxins , highly carcinogenic toxins formed by
fungi present in many agricultural crops. These toxins can contaminate maize in the field;
however, it is in the subsequent processing and storage phase that the aflatoxin level
increases rapidly. In Africa maize is the main food staple and proper drying is crucial to contain
storage losses. Open-air drying is the common practice, but new methods including solar and
biomass-heated dryers are being proposed; therefore, their efficacy and profitability need to be
compared to current practice. As traders can more easily estimate drying costs and maize prices
than farmers, we estimated the efficacy, costs and benefits of open-air drying based on
interviews with 122 traders in Kenya. Respondents reduced maize moisture content by 5.8%
(from 17.8%), at a cost of KES 113/90 kg bag (US$ 1.13) or KES 22/90 kg bag/% moisture
(US$ 2.46/tonne/% moisture or 0.7% of the grain value). The interviews also indicated that
drying is an integral part of the larger maize trading and value chain. The rate of return (RoR) for
transporting maize from purchase place to drying place, plus actual drying, was estimated at a
modest 11%; The RoR of transporting maize from drying place to point of sale, on the other
hand, was a strong 24%, while the overall RoR over the whole value chain was the highest, at
26%. We conclude that profits from maize drying itself are rather small, and that profits from
trading in the maize value chain are largely derived from spatial arbitrage. Further, it needs to be
ensured that alternative drying technologies are more economical than open-air drying, by
comparing their performance to open-air drying using

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1.2 Related work.

David Burii said his innovative idea was driven by the erratic weather conditions that
characterizes Laikipia County and designed the maize drying machine two years ago, adding that
it has a capacity to dry between 30 to 50 bags of maize per day to the recommended moisture
level of below 13.5 percent. The mode of powering his plant is by use of maize comb, this can be
further improved by using waste industrial heat as a byproduct, the industrial exhaust line has
high heat content of about 200˚c. When we use the waste product (exhaust gas) as a byproduct,
the cost of heating the furnace is reduced.

1.3 Theoretical statement

Higher airflow, higher temperature and low humidity increases drying speed. Raising air
temperature increases moisture carrying capacity of the air and decreases relative humidity. As a
general rule of thumb, increasing the air temperature by 20℉ doubles the moisture holding
capacity of air and cuts the relative humidity by half.

As the air enters the grain it picks up some moisture which cools the air slightly as the air moves
through deep grain mass the air temperature is gradually lowered and relative humidity is
increased until the air approaches equilibrium with the grain. If the air reaches equilibrium with
the grain, it passes through the grains without any additional drying. This slightly dried air will
begin to pick moisture when it reaches wetter grain.

Dryers can be categorized in different ways. There are natural air, low temperature, and high
temperature dryers; there are batch, automatic batch and continuous flow dryers; and there are
in-bin and column or self-contained dryers. Dryers can also be classified according to the
direction of airflow through the grain; cross-flow, counter-flow, and concurrent-flow.

1.4 Conclusion
To efficiently store or process maize, it has to be efficiently dried to the recommended level.
This can be achieved using several methods, the choice of these methods depends on the cost of

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setting up the plant, running cost, efficiency of the plant, maintenance of the plant among others.
This has made people choose different drying methods.

CHAPTER THREE

DESIGN ANALYSIS AND METHODOLOGY

3.1 Compressors.

3.2 Selection of compressor

Before deciding upon size of the compressor there are several factors to consider Depending on
your demand and cost involved. There is also an assumption that the plant may also increase or
expand someday. The compressors which could be used are single stage or multi stage
compressors, intermittent or continuous or mixed, single cylinder or multi cylinder etc.

3.3 Intermittent services

These are services which are only required at time and not all the Time. The compressor is
normally automated or set to a certain pressure of which when the pressure reduces from the
receiver the compressor starts up automatically to fill the receiver until maximum set pressure is
achieved.

3.4 Compressor stage, Double stage compressor

A multi stage compressor is preferred since it uses the first stage of compression then intercooler
and the second stage for further compression stage before the air is transferred to the receiver or
aftercooler, the second compression stage is optimized by the intercooler which lowers air
temperature for better cooling. In multi stage compressor the aftercooler can be eliminated.
Considering our plant which has Intimittent services equipment, it will need at least a two stage
compressor of 7.5KW.

A two stage compressor with an intercooler diagram.

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COMPRESSO
COMPRESSOR INTERCOOLER R

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3.5 Factors considered when selecting air compressor.

i) Pressure required
The maximum working pressure required should be taken into account when choosing air
compressor. The compressor should meet the maximum pressure required by the system.

ii) Capacity of the air

The compressor chosen should be able to supply adequate volume of air as required by the plant
demand.

iii) Types of cooling system

The available compressor should use a cooling system that will be readily available on the
ground.

iv) Method of control of air capacity.

The compressor chosen should be capable of controlling its output according to the variable
demand of air in the plant.

Advantages of double/multi stage compressor.

1) Reduces loss considerably.

2) Work done per KG is reduced by intercooler.
3) It improves volumetric efficiency by intercooler.
4) Provides effective lubrication due to lower temperature.
5) The size of air cylinders may be adjusted to suit the volume and pressure of the air
6)

Compressor specification

Receiver capacity 1250L

Working temperature 250ºc

Maximum sale working pressure 15 bars

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Fan rating

240/415 V supply

1.5 KW

1500 rpm

50 Hz

Factors affecting selection of fan.

1) Total pressure developed by a fan.

2) Power of the fan.
3) Volume flow rate of the fan.
4) Plant’s requirement need.

Motor rating

240/415 V

3KW

2800 rpm

50Hz

Aftercooler

Compressed air is normally at high pressure and temperature does aftercooler reduces its
pressure and this in turn reduces the volume of the compressed air, after cool allows smaller
receiver to be used for this storage of air. The most effective aftercooler is water cooled. In
situation where water cooling is not available, an air blast aftercooler is used

Intercooler in a double cylinder compressor.

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COMPRESSO
COMPRESSOR INTERCOOLER R

Air receiver

The air receiver also acts as a cooling plant resulting in formation of the condensate at the base
of the tank. If the content set is allowed to build up there are problems of corrosion to the
receiver itself

It is therefore important to ensure that the collected dust and liquid are removed automatically.
This nice acetates provision of the trap which will handle varying proportions of water oil
Emulsion and dust regular cleaning is thus warranted.

Functions of air receiver

1) Acts as a storage point for air that goes to the heat exchanger
2) Add pulsation damper (reciprocating compressor)
3) Cools air
4) Adds drain point for condensate.

3.6 Receiver sizing

The receiver will be served according to the volume to he handled. This will be made possible by
the pressure difference; the internal diameter D in mm.

In our case we recommend a velocity of 9m/s and the actual flow rate 86.5m/min.

D=
√
2 1280× 86.5
9 ×60
D=14mm

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3.7 Recommended receiver capacity

Compressor( KW) Tank size(L)

0.37 113.55

0.56 113.5

0.75 227.1

01.1 227.1 OR 3.28

1.5 302.8

3.7 302.8

5.6 454.2

7.5 454.2

Distribution pipes

They should be as short as possible, free from Sharp ends and ample size. It is good plan to
employ pipes that are galvanized inside in order to prevent the possibility of rust and scale being
carried to the drying chamber.

3.8 Sizing of the pipes

Most important information a designer needs is the difference in piezometric head required to
force fluid at a certain speed at a steady rate through a pipe.

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Dissipation of energy by fluid friction results in a fall of piezoelectric head in the friction
direction of the flow and if the pipe is of uniform crossection and roughness and the flow is
sufficiently far from the inlet pipe for the condition to become settled piezometric head fall
uniformly. Properly gauged pipes together with fittings made of the right materials are essential
for efficiency and economical operation. Before designing the size one must have knowledge of
flow mechanics of Fluid Freed which will assist him in determining the proper sizing method.

Hf = 4flv²
2dg
Heat loss due to sudden enlargement (hl)

At inlet HI= (V1-V2)

2g

At Exit h1= V²
2g

Heat loss due to sudden contraction

H1=V² (1/cc-1) ²
2g
LOSS in pipe fitting at pipe entry
HI= k (U²)
2g
Flow rate (velocity method equation)

Q = area x velocity

Q = Ax v

Q = πD²v
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Pipe diameter

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The following methods will be applied

V = flow rate
D²

Actual flow rate = flow rate

Compensation rate

Compensation rate = absolute temperature

Atmospheric pressure

3.9 Installation of pipe works

A great thought must go into consideration before installation of any pipe work system

There are rules applied when installing;

1) future problem for maintenance and servicing

2) complete installation appearance
3) Operation of the system
4) Drainage and rating of the system

3.9.1 Accessibility of the valves

Pipes should wherever possible run at right angle or parallel to the building lines. They should
not cross door or under roof light. The system should look as though designed with the building.
Valves must be positioned where there is easy to access in order to put the use for which they are
installed required periodic maintenance.

3.9.2 Bracketing, anchoring and expansion

Installation of pipe work special through to bracketing achieving an expansion of pipe works. In
order to prevent future faults occurring when work life of an installation namely fracturing of the
pipe work which may lead to heavy maintenance costs and sagging of the pipe work, creating

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operational difficulties that is a locking should we prefabricated fixing the brackets for the whole
section of the installation.

3.9.3 Bracketing
There are two types of Bracketing used in pipe works.

1. Anchors
2. Guide brackets

1. Anchor brackets
The main function of anchor bracket is to hold pie rigid to a fixed point thus preventing any axial
or lateral movement at that point. It will also support the weight of the pipe at that pion

2. Guide brackets
They are used where no lateral movement of the pipe can be allowed to take place but axial
movement only required.

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Lagging of pipes/ insulation

Lagging/insulation is necessary to ensure that heat loss is minimized in the already heated/
warmed air from heat exchanger to the drying room/chamber. Lagging also protects the pipes
from external damages and harsh environmental conditions.

Heat exchanger is also lagged to ensure that maximum heat is absorbed by the system. The
Lagging material preferred is vitrile rubber insulation Armaflex class O which is highly flexible
with high water vapour diffusion resistance.

It has a thermal conductivity of λ 0°c ≤0.035W/mk and water vapour resistance µ≥7000. It is
highly flexible elastomeric foam that can be installed quickly on irregular shapes and installation
on tight spaces.

Filters

Air applied for the purpose of drying of maize is supposed to be clean and free from harmful
substances since may this edible there's an air filter is incorporated into the lin.

Common usually used are.

i. standard air filter

ii. collecting air filter
In a standard air filter the air is given European circular motion so that the particles of the dirt
are thrown outside against the wall of the ball in closing the unit and so drop into the sump.

For conditions requiring a particular high quality a compressed air condensing filter is used they
are capable of removing particles of oil microscopic micro size. They are used after standard
filter.

Regular filter

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The purpose of regular feature is to maintain the secondary air pressure required and this
pressure depends on the needs of the supply. After the regulator the air enters the heat exchanges

Disadvantages of water in the system

1) It causes scale formation

2) It may result in high cost of system maintenance
3) When moist hot air enters drying house we drink process may not be as fast as intended need
to the high humidity content in the air.

Elimination of water

An Atlas Copco adsorption drier would do the trick this will reduce water vapour in the air to
such an event that condensate in the airline does not take place before temperature off 20
degrees’ centigrade pressure development point is reduced

It should be noted that from the maximum efficiency of operation of the Atlas Copco dryer prior
tooling is done by either after cooler or in case of multi stage compressor an intercooler is
required.

There is also alternative option of using combined air filer and regulator just after receiver tank

Heat exchanger

A counter flow heat exchanger will be used. The efficiency of heat exchanger is assumed to be
100% since the thickness of the tubes is heat exchanger are as thin as possible and their
coefficient can be ignored. The tubes ore of either copper or aluminum of thermal conductivity
of386W/mk and 229W/mk respectively. The air in the tubes is under forced convection since it is
induced, its heat transfer coefficient is 10- 1000W/m² k and this varies with air velocity.

From; Flow rate Q = area ×velocity

We know that, flow rate of heat will increase with increase in air flow.

Since heat transfer in a counter flow heat exchanger is given by, Q= UA (L.M.D.T)

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Q- Heat transfer

U- Heat transfer coefficient

A - Surface area of the tube

L.M D T – logarithmic mean temperature difference

L.M.D.T = ∆ T2- ∆ T1
Ln(∆ T1/∆ T2)

inside the tubes

Coil tubing inside the heat exchangers

Drying beds

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The drying beds are made are made of aluminum to allow better and faster transfer of heat in for
the dying process, they are placed horizontally on top of each other. This also ensures maximum
utilization of the space in the drying room

Block diagram

EXHAUST LINE DAMPER

HEAT DRYING CHAMBER

EXCHANGER MICRO
CONTOLLER

AIR
COMPRESSOR
RECEIVER MOTOR

DAMPER

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Plant circuit diagram.

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Operation the maize drying plant.

The exhaust gas has a higher temperature of about 200°c; this hot exhaust gas can be harnessed
by bypassing it to the heat exchanger. At the bypass there is a damper linked to a motor which is
connected to a controller. Whenever heat is required at the heat exchanger the damper on the
main line closes and the ones on the bypass line open and vise verser.

Air from the compressor is stored in the air receiver. Air from Air receiver passes though air
filter and regulator before going to the heat exchanger. Air regulator ensures that the flow of air
is controlled to achieve the desired velocity for flow of the air the heat exchanger.

The pipes in the heat exchanger are coiled to increase the surface area for better heat absorption,
the pipes which are made of copper or aluminum for faster heat absorption; this increases the
efficiency of the heat exchanger.

Air coming from the heat exchanger shall have been warmed as required and then through the
delivery pipe the air will be transferred to the drying chamber by means of pressure difference,
theatre is then blown to the maize grains that are on the during beds made of perforated
aluminum. The perforation allows more air circulation.

The blowers that are placed on both sides blowing hot air at constant speed will cause Eddie
current which will raise the air upwards. At the top of the roof there are vents with suction fans,
this will ensure that moist air is drawn from the chamber to create room for more fresh hot air
form the heat exchanger.

The drying temperature will be set depending on the purpose of the maize; maize seed drying
temperature will not exceed 42°c while milling maize drying temperature will not exceed 60°c.
There is a temperature sensor in the drying chamber that is connected to the controller.
Whenever temperature reaches the set limit the bypass dampers will close and this automatically
opens the main line damper by the linkage rod. The second damper of the bypass line ensures
that there is no flow of exhaust gas to the heat exchanger when the main line is open.

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CHAPTER FOUR

4.0 MAINTENANCE OF THE SYSTEM.

4.1 Maintenance
Maintenance helps to keep the machine and plant in such a condition which permits them to use
their optimum capacity with minimum breakdown and the lowest possible cost. in order to keep
the system/plant efficiently working, preventive maintenance affect the work of the installation,
servicing and adjustment. This is necessary to overcome the failure of equipment during
operation. The necessary action is taken before anticipated failure occurs.

4.2 Phased preventive maintenance

Compressed air and any other relevant plans should be subjected to phased preventive
maintenance schedule and responsibility of an engineer. Terms used in the ppm are as follows

Examine

To make a careful and critical scrutiny of an item without dismantling by use of site hearing
smell and touch so as to verify the plant or equipment are working and are in order.

Test

To operate the plant or equipment or use of the appropriate testing instruments and equipment to
ensure that the plant or equipment are fully functional

Safety valve

They are automatic spring loaded valves devices which relieves pressure in case of any excess
build up other than maximum permissible. They prevent receiver explosion and also maintain the
whole plant at a recommended pressure it should therefore be tested for proper regulation and
also inspected for malfunctioning

Air receiver

It should be inspected and cleaned regularly. It must be drained periodically to extract the
condensate at the bottom as a result of condensation due to the cooling of air. It is important to
note that the area list through ozone is at high velocity. Air at 100 PS a expands to Almost eight

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times that's a lot of cash should be observed if The Jets and personnel should not play pranks
with the compressed air.

Heat exchanger

Heat exchange she will be well maintained from time to time to ensure that the heat transfer from
the exhaust gas to the air from the air receiver is efficient. The heat exchanger should be well
lagged or insulated using the appropriate material and should be suit blonde from time to time or
on a regular basis to ensure that the internal pipes are not covered with suit which may reduce the
heat transfer.

Blowers and fans

We should be well installed and maintained from time to time. Their motors should be will to
ensure that they are well aligned and not too tight nor neither do they sag. This will ensure
maximum efficiency of the blowers. Blowers should be lubricated from time to time to ensure
that nice need to friction is avoided and this will also ensure that they run smoothly and that the
maintenance costs reduced due to wear and tear caused by the friction

Suction vent

This should be maintained to ensure that flow of the air from the drain chamber is continuous so
that fresh air from the heat exchanger can enter into the drain chamber for drying of the maze
drain this can be achieved only when it is regularly maintained and ensure that there is no
blockage and that the fans that are pleased at the events for sanction are properly functioning and
efficient. They should be lubricated so that there is no noise due to friction.

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4.3 Planned preventive maintenance

Compressor working time Operation

0 - 8 hours Check oil pressure and ring condensate from the regulating valves

0 - 50 hours check oil level and top up if need be record the volume added

0 - 500 hours All valves are overhauled cleaned and inspected replacement
should be done for one out valves.

0 - 1500 hours Air intake filter replaced

six months safety valves are test blown

3000 hours Lube oil changed regulating valves and filter cleaned loop oil
pump inspected and all valves replaced

6000 hours Overhaul of the compressor

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4.4 Compressor driving belt

The bell should be checked and tension regularly if they are worn out change changing must be
done to all bells and should be tightened to the recommended tension. since to lose bells will
sleep on the motor pulley and costs under heating and where. Also over tightening should be
discouraged and apparently this overloads the bearing when replacing the belts pulley alignment
must be checked before it tightening the motor holding down nuts

4.5 Plant troubleshooting

Symptoms possible causes

Pressure too low Excess leakage in the airlines valves

one out piston rings
demand greater than unit capacity
wrong speed
Insufficient capacity Section line blocked, dirty filter
leakage in intercooler
valve not install right
blown cylinder head gaskets
built sleeping

Compressor insufficient Lube oil

wrong direction of rotation
suction line blocked, dirty filter
Strips missing from the valve or broken
Compressor knocks loose valve
motor shutting back and do to belt
misalignment or mounting not level
Mean bearing need adjusting
Too much crack join
bearing clearance

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compressor vibration piping not supported right

Motorola out of balance
You need not properly secured to foundation
Defective foundation
Compressor overloads motor insufficient loop oil
belt too tight
voltage too long
discharge pressure
discharge pressure to high
electrical power characteristics
restricted line/blocked line

excessive oil consumption excessive oil consumption suction line blocked

dirty filter
oil level too high
we will viscosity too high
high pressure to high
one out piston rings
Receive a safety valve blown leakage in control line
pressure with differential to narrow
defective or improperly set safety valve
Heat exchanger not giving enough heat Problem in the insulation
the internal pipes are covered with a lot of suit

Blow is not working properly motor problem

Loose fan belt or tight fan belt

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4.6 Plant maintenance schedule

Item Action Time
compressor room should be kept clean dry and as long as the compressor is
cool running daily
Compressor should be kept clean and free daily
from oil spilling
suction filter should be kept or checked regularly
clean by blowing or
discharging
valve in brackets action or should be checked and monthly
discharge change if necessary

intercooler and aftercooler to be kept clean by dusting regularly

with compressor air

Belts should be checked for regularly

tensioning stroke wear
Air receiver should be checked for regularly
indicator glass safety valve
drain valve
Fans or blowers should be checked for regularly
motors , anti-vibration
mounting, lubrication,
bearing fun belts and noise
Damper motors should be checked for regularly
electrical wiring noise and
lubrication

Suction vents should checked for any regularly

blockage
Pipes should be checked for any regularly

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damages or leakages
should be checked for the
installation and insulation

Heat exchanger should be checked for any

soot accumulation on the pipe regularly
surfaces and fins

4.7 Material and costing

COMPRESSOR NUMBER OF COST PER UNIT TOTAL COAST
HEAT EXCHANGER 16 meters 450 7,200
Copper tubing
Insulation
COMPRESSOR 1 25000 30,000
RECEIVER 1 20000 20,000
FILTER AND 1 1200 1,200
REGULATOR
DAMPER 3 250 750
MOTOR 2 6000 12,000
BLOWER 6 1500 9,000
PIPES 10 meters 250 2500
DAMPER LINKAGE ROD 1 150 150
MICRO CONTROLLER 1 800 800
TEMPERATURE SENSOR 1 150 150
VENTS SUCTION FANS 6 800 4,800
DRYING BEDS 8 1200 9,600
TOTAL 99,000

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CONCLUSION
This project is aimed at solving the food insecurity that results from wastage of maize by
aflatoxin and during the storage. This project is very easy to install/setup, run and maintain. It
also utilizes readily and affordable available materials for its designing.

RECOMMENDATION
This project is very good and helps in recycling energy as well as increases the efficiency of
drying. The benefits of this project outweighs its limitation and it is simple to maintain and run
thus I would recommend that it should be introduced in the market. One heat exchanger can
serve more than one drying room. I recommend this system to all maize milling industries can
adopt this system.

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REFERENCES
i) APPLIED THERMODYNAMICS FOR ENGINEERING TECHNOLOGISTS fifth edition
T. D EASTROP A. MAcCONKEY
ii) ENGINEERING THERMODYNAMICS THIRD EDITION R.K Rajput
iii) PROCESS PLANT MACHINERY HEINZ P. BLOCH CLAIRE SOARES
iv) POWER PLANT ENGINEERING BLACK & VEATECH
v) FLUID MECHANICD AND HYDRAULIC MACHINES Dr. R. K Bansal
vi) MECHATRONICS ELECTRONIC CONTROL SYSTEM IN MECHANICAL AND
ELECTRICL ENGINEERING 3RD EDITION W. BOLTON

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APPENDICES
Hf – head loss due to friction
V - Velocity
g – Gravitational
h - Height
D – PIPE DIAMETER
Q – FLOW RATE

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