Farm Machinery Maintenance and Management
Professor Surendra Singh Project Co-ordinator Central Institute of Agricultural Engineering Nabi Bagh, Bhopal (Madhya Pradesh) 462038
and
Professor S R Verma Ex-Dean College of Agricultural Engineering Punjab Agricultural University Ludhiana (Punjab) 141 004
anysojti ICAR
Directorate of Information and Publications of Agriculture
Indian Council of Agricultural Research, Krishi Anusandhan Bhavan-I, Pusa, New Delhi 110 012
Printed : June 2009
Project Director (DIPA) :
Incharge, English Editorial Unit : Editing : Production Officer : Technical Officer (Production ) :
Chief
Incharge (Art Unit) : Senior Artist :
Dr T P TRTVEDI
Dr R P SHARMA Dr SUDHIR PRADHAN V K BHARTI ANIL KUMAR SETH
B C MAZUMDER NARENDRA BAHADUR
All Rights Reserved Š 2009, Indian Council of Agricultural Research, New Delhi
ISBN
Price
:
978-81-7164-094-2
Rs. 475.00
Published by Dr T P Trivedi, Project Director, Directorate of Information and Publications of Agriculture, Indian Council of Agricultural Research, Krishi Anusandhan Bhavan, I, Pusa, New Delhi 110 012; Lasertypeset at M/s Graphic Point, 26 A, Amrit Nagar, South Extn. I, New Delhi 110 003; and printed at M/s National Printers, B-56, Naraina Industrial Area, Phase-I, New Delhi-110 028
Contents Preface
iii
1. Introduction
1
2. Maintenance of Farm Machinery
2
3. Farm Machinery Management
130
4. Safety of Agricultural Machinery References
189 199
Appendices
200
I
S I Units
200
II
Conversion Factors
200
III
Conversions
201
IV
Useful Life of Farm Machinery
202
V
Status of Farm Power Sources in India
203
VI
All India Indigenous Production and Sale of Tractors and Power Tillers
204
VII Status of Farm Power from Different Sources in India
205
VIII Cultivated Area, Production and Power
206
Availability in India
IX
Status of Hand and Animal Operated
207
Agricultural Machinery in India
X
Status of Power Operated Agricultural
208
Machinery in India Subject Index
209
1. Introduction
M
AINTENANCE concerns with the regular care, servicing, adjusting, repairing and recalibrating of tools, machines and equipment to ensure
smooth and trouble-free operation. A properly maintained farm machine operating under specified working conditions will meet a variety of agro-technical and other requirements, viz. reliability, longevity, economy and safety. Maintenance does not imply only repairing a machine after it breaks down but also to protect it so that it does not break down or bear out to soon or to frequently. There are 3 main enemies i.e. wear, dirt and heat, against which machines need protection. The parts in a machine rub and turn against each other until they get heated and begin to wear. The friction causes wear. Use of proper lubricants and bearings helps in protecting the machines and prime movers from friction and thus wear. The same is true for dirt, when it enters the machine parts, it can easily scratch and wear out moving parts. Filters are used to arrest dust particles and avoid damage to the machine parts. Similarly, excess heat can damage various moving parts, especially engines, which develop crack. Proper cooling protects parts from excess heating. Good maintenance keeps machines ready for work, prevents delays and saves time, money and crops. The guidelines and practices help the users in proper maintenance of their machines and prime movers to avert impending failures and troubles during operation. Tractor and farm machinery maintenance includes the daily and periodic servicing that will ensure better performance and longer life. Proper servicing reduces the number of field breakdowns and the subsequent frequency of major reconditioning and overhauling. It is also essential that the major repair and maintenance are carried out by qualified service men in the repair shop, having proper workshop facilities. Operators’ Manual supplied by the manufacturer carries relevant information regarding the service, operation and maintenance. Machinery users and operators must follow the same. Besides the Operators’ Manual, it is advisable to maintain a logbook in which hours of use and servicing need to be recorded regularly. The recording helps the user in quick and easy checking of fuel and oil consumption, hours of operation, type of work performed, nature of breakdowns, repairs and repair cost as well as the daily and periodic servicing done to the machine and prime movers.
2. Maintenance of Farm Machinery /ÿOMMON types of machines and equipment used on the farm include the engines, pumps, tillers, harrows, seed drills/planters, sprayers, threshers, combines etc.
Varactors,
TRACTORS AND THEIR COMPONENTS
Tractor consists of several systems and components, which need regular mainte¬ nance. The various components in a tractor are engine, fuel system, air intake and exhaust systems, cooling system, lubrication system, transmission system, electrical system, hydraulic system, tires, brakes, and other individual compo10) (11
6XlX8X5X9Ji) (13}
n 12
2
,14
15,
16,
4 3
1. Fuel tank, 2. Fuel cock, 3. Diesel filters (primary and secondary), 4. Hand priming pump, 5. Fuel injection pump, 6. High pressure pipe, 7. Injector, 8. Overflow pipe, 9. Battery, 10. Radiator, 11. Fan, 12. Air cleaner, 13. Steering wheel, 14. Front wheel, 15. Clutch and 16. Gear box Fig. 2.1. Locations of different components of a tractor
nents (Figs. 2.1, 2.2). These systems/components require regular attention. Every tractor manufacturer supplies an Operator’s Manual, which gives details of different parts and contains details of hourly, monthly and yearly mainte¬ nance schedule. All these periodic maintenance are dependent on the hours of use of the tractor. Every tractor is equipped with an hour meter that records the hours of engine running. Preventive maintenance is normally done at 10, 100,
Maintenance of Farm Machinery
3
500 and 1,000 hours of engine running. Thus the maintenance schedule should be carried out as indicated : Hour meter reading Maintenance (i) 10 - hr maintenance 10 (ii) 100 - hr maintenance 10 + 100 = 110 (iii) 500 - hr maintenance 110 + 500 = 610 (iv) 1,000 - hr maintenance 610 + 1,000 = 1,610 8
2
1
SEEL#? 9
5
6) (7) (4) (3
1. Back light, 2. Position control lever, 3. Adjustable lower link, 4. Top link, 5. Fixed lower link, 6. Differential, 7. Power-take-off, 8. Seat and 9. Rear axle. Fig. 2.2. Locations of different components on rear of a tractor
If a tractor is operated under abnormally dusty or muddy conditions, it might require more frequent maintenance. Common signals warranting maintenance: Look for damaged parts. Watch the gauges for overheating, reduced oil - pressure, an alternator not charging and any other sign of trouble. Listen to unusual sounds like squeaks, excessive vibration, rattling or knocking sounds. Feel for loose belts, chains, nuts, bolts, washers, keys joints and other fasteners. Smell for overheating of bearings, electrical equipment, slipping belts, leaking fuel and fires around the exhaust system. To sum up, periodic maintenance is the formidable need of all machines for safe and long trouble-free working. Maintenance practice and careful operation make the equipment look better and perform better. It displays good judgment and saves money by being more efficient. Engine An internal combustion engine working on diesel fuel compresses the air and the fuel is injected into the cylinder or pre-combustion chamber. The combustion leads to an explosion, which pushes the piston down. Each piston is connected
4
Farm Machinery : Maintenance and Management
.Cylinder
Piston Connecting rod
. Crank shaft
to the engine crankshaft by means of a connecting rod. Downward movement of piston and the connecting rod imparts a rotary motion to the crankshaft. Power is tapped from the crankshaft to operate other machines or mechanisms. Basic components (Fig. 2.3) of an engine are
cylinder, cylinder-head; piston, piston-pin, piston-ring; connecting rod, crankshaft; Fly wheel flywheel; valve system i.e. valve, intake and exhaust, cam shaft, cam gear, tappet, push rod and rocker arm; fuel Fig. 2.3. Components of an engine supply and carburetion system, i.e. fuel tank, fuel line, fuel pump, carburetor, manifold and air cleaner; ignition system, i.e. battery, coil, sparking device, timing mechanism breaker points, distributors, switch and wire connection; cooling system i.e. tank, radiator, pump, water-jacket, fan, thermostat, pipe and connections; lubrication system, i.e. oilpump, oil-lines, oil-gauge, oil-filter and grease fittings; and governing system, i.e. weights and springs, fingers (in hit and miss system only), throttle butterfly (in throttle system only). Each time a piston moves up or down, makes one stroke in a four-stroke cycle engine (Fig. 2.4). There are two types of engines, viz. compression O -ignition engines or diesel engines in which air is compressed which gets hot that it ignites the fuel, and spark-ignition engines or petrol engines which are those in which mixture of air and fuel is ignited by means of an electric spark. The basic principle of operation of four strokes in a compression (diesel) and spark ignition (petrol) engines are as follows: o Suction stroke (Intake stroke) The piston moves downward and air is drawn in the cylinder through the intake o of] valve, which opens when the piston is at top-dead-center (TDC). the Fig. 2.4. Four strokes, viz Power stroke, Compression stroke Exhaust stroke, Suction stroke and Compression stroke in a diesel engine When the piston moves upward from bottom-dead-centre (BDC), the air is compressed to a pressure of 30-40 kg/cm2 and temperature of 650째 to 800째C.
o
(ft
Maintenance of Farm Machinery
5
At this point both the inlet and outlet valves remain fully closed. Power stroke (Combustion stroke) As the piston reaches top-dead-centre diesel fuel is injected into the cylinder and is instantly ignited due to high temperature of compressed air. In spark ignition engines the spark plug ignites the air and fuel mixture. The explosive force thrusts the piston down the cylinder and the crankshaft gets rotated. Exhaust stroke As the piston is pushed down towards bottom-dead-centre, exhaust valve opens and combustion gas is discharged through exhaust valve. The gas is discharged completely when piston reaches top-dead-centre. Four stroke engines are commonly used in tractors and farm machines. However, two stroke engines are also used in small power tools viz. chain saw, mowers and sprayers. All the four strokes, viz. intake, compression, power and exhaust, take place in just two strokes in the two-stroke type of engine. Combustion chambers The combustion chamber is an important part in the performance of the diesel engine. There are 2 types of combustion chambers viz. direct combustion chamber, and indirect combustion chamber. Direct combustion chamber is of direct injection type whereas indirect combustion chamber is of two types, i.e. pre-combustion chamber type and swirl chamber type. In the direct injection type, the injection nozzle sprays the fuel directly into the main combustion chamber between the cylinder head and piston. The chamber provided on the top of the piston is formed into one of the several special shapes designed to improve combustion efficiency. In the pre-combustion chamber type, the fuel is sprayed into the pre-combustion chamber by the injection nozzle. Partial combustion takes place in pre-combustion chamber and remaining fuel which is unburnt is passed through a passage between pre-combustion and main combustion chamber, where it is broken into fine particles for complete combustion in the main chamber. In swirl chamber which is spherical in shape, air compressed by the piston enters the chamber and produces a turbulent flow into which fuel is injected. Most of the fuel is burnt in swirl chamber, but part of it reaches the main chamber where complete combustion takes place. Now-a-days most of the tractors have direct injection type combustion chamber. The main advantages are higher thermal efficiency, low-fuel consumption, easy to start especially under cold conditions, and simple cylinder head design leading to low heat loss. Engine performance The engine performance depends mainly on cylinder bore, piston stroke, clearance volume, piston displacement (swept volume) and compression ratio.
Cylinder bore It is the internal diameter of the engine cylinder and is measured in millimeter (mm).
Farm Machinery : Maintenance and Management
6
Piston stroke It is the distance traveled by the piston from top-dead-center to bottomdead-centre or vice-versa. The bore to stroke ratio is an important criteria in engine design. If the stroke exceeds the bore, the engine is called long stroke engine. If the bore exceeds stroke, it is called over square. If bore and stroke both are equal, it is called square engine. Square and over square engines help reduce piston and bore wear. Clearance volume It is the volume above the top of the piston when piston is at T.D.C. and is expressed as cubic centimeters (cc). Stroke-bore ratio It is the ratio of length of stroke (L) and diameter of the bore of the cylinder (D). This value is 1.25 for tractors and varies from 1.0 to 1.45 for other automobiles. Piston displacement The volume which piston displaces when it moves from bottom-dead-centre to top-dead-centre is called stroke volume or piston displacement. It is also called swept volume. The total displacement in the engine is stroke volume multiplied by number of cylinders. It is expressed as: Pd = 7t(D/2)2 L N where, Pd, total displacement, (cm3); D, cylinder bore, (cm); L, stroke length, cm; and N, number of cylinders Engine displacement It is the total swept volume of all the pistons during power strokes occurring in 1 min. It is expressed as Ed = Pd n N/2 (for 4-stroke engines) = Pd n N (for 2-stroke engines) where, Ed, Engine displacement, cm3; n, number of cylinders; and N, rpm of the engine Compression ratio It is ratio of the total cylinder volume with the piston at bottom-dead-centre (i.e. piston displacement + clearance volume) to the combustion chamber volume with the piston at top-dead-centre (clearance volume). Compression ratio varies from 14:1 to 20:1 for diesel engines and 4:1 to 8:1 for petrol engines. Piston speed It is the total length of travel of piston in a cylinder in 1 min. It is expressed as Sp = 2 L N
where, Sp, piston speed, m/min; L, length of stroke, m; and N, rpm of engine.
Piston speed varies from 300 to 500 m/min for high speed tractor engines. Engine cycle It is a cycle consists of events taking place in each cylinder of an engine between 2 successive power strokes.
Maintenance of Farm Machinery
7
Torque The force produce by the combustion of fuel is transmitted to the crankshaft by a connecting rod develops a torque at the crankshaft. The amount of torque developed depends on the force exerted on the piston and the length of crank arm. i.e. T=Fr
where,T , torque, (Nm); R force, (N); and r, length of the crank arm, (m). Indicated horsepower It is the total horse power developed by all the cylinders and received by pistons disregarding of friction and other losses within the engine. It is the rate at which the piston is pushed downwards by combustion of fuel. It is expressed as IHP =
IHP
=
PLAnN/2 4500
(for 4-stroke engines)
PLAnN 4500
(for 2-stroke engines)
where, IHR indicated horse power, hp; R indicated mean effective pressure, kg/cm2; L, piston stroke, m; A, cross sectional area of piston, cm2; n, number of cylinders; and N, engine speed, rpm It can also be expressed as IHP
=
IHP =
PLAnN/2 60 x 1012
(for 4-stroke engines)
PLAnN 60 x 1012
(for 2-stroke engines)
where, IHR indicated horse power in kW; R indicated mean effective pressure, Pa; L, piston stroke mm; and A, cross-sectional area of piston, mm2. Indicated mean effective pressure It is an average net pressure on the piston during the power stroke only. It is measured by an engine indicator. Brake horse power (BHP) It is the net power available at the crankshaft for doing the useful work. This is 20-30% less than indicated horse power as some of the power developed inside the cylinder is lost in friction among various parts. It can be measured at the belt pulley by a suitable dynamometer. Frictional horsepower (FHP) It is the power required to run the engine at a given speed without producing any useful work and lost in friction between the various parts. It is expressed as: FHP= IHP - BHP
PTO horse power It is the power available at PTO shaft of a tractor for doing useful work. It can be measured by PTO dynamometer.
Farm Machinery : Maintenance and Management
8
Drawbar horse power It is the power of a tractor available at drawbar for doing useful work. This is the power available to pull the load. It can be also measured by spring dynamometer.
Mechanical efficiency It is the ratio of brake horse power and indicated horse power and expressed in per cent.
Volumetric efficiency It is the ratio of quantity of fuel mixture actually drawn into cylinder by the piston in the intake stroke and producing power to the actual volume of space displaced by the piston. The volumetric efficiency of automotive engines varies between 75 and 85%. Thermal efficiency It is the ratio of the output in the form of useful mechanical power to the power value of the fuel consumed. It varies from 15 to 35% depending upon the type of engine, speed, load, design and other factors. Components of engine Cylinder head All engines have removable cylinder heads. This -cv; is attached to the cylinder block with a number of bolts and a copper asbestos gasket provides a seal between head and block. The cylinder head (Fig. 2.5 a) contains space which is known as combustion chamber. It contains passages that match with those Fig. 2.5 a. Cylinder head of cylinder block and allow the coolant to circulate to provide effective cooling. The cylinder head should be able to withstand the temperature and pressure developed inside the cylinder. It is located over the cylinder block. It is made of high grade cast iron. However, in some special cases a cast aluminum alloy is used to provide better heat dissipation and control. It contains water - jackets for cooling. Cylinder block and oil-sump The cylinder block (Fig. 2.5b) along with crankcase forms the main part of
m
Fig. 2.5 b. Cylinder block
Fig. 2.5 c. Oil sump
% %
Maintenance of Farm Machinery
9
L
the engine. It has cylinders which guides the piston. The crankcase supports the crankshaft and camshaft through bearing. An oil sump (Fig. 2.5c) is bolted at the bottom of the crankcase serves as a reservoir for oil engine. The cylinder block has also water passage inside for cooling. In some engine blocks weltch plugs are fitted at the outer surface of the cylinder block for safety against water freezing. The cylinder block and crankcase usually have single casting.
[
Cylinder
|
It is the part of engine which converts heat energy into mechanical energy with the help of piston that moves up and down inside the cylinder. It provides [ space, in which the piston operates to draw in the fuel mixture, compresses it [ and allows it to expand and generate power. It is generally made of high grade I cast iron. Design and construction of cylinder depends on power required, [ compression ratio, valve arrangement, method of cooling and arrangement of I cylinders. A large number of small cylinders are prefered over a small number of [ large cylinders mainly due to smooth torque, lower engine weight and higher I efficiency. Large cylinders are preferred when very low crankshaft speeds are ! desirable as in marine propulsion. Casting of cylinders in a single block offers a number of advantages, i.e. it gives more compact and rigid construction, and I provides better enclosure for engine mechanism. Hollow space in block is provided [ for circulation of cooling medium for liquid-cooled engine. Air-cooled engines i usually have the cylinders cast separately and equipped with fins to provide better air circulation and more rapid escape of the excess heat. The bore in which the piston moves may be either integral with the main I cylinder or it may be a separate liner which is also known as the sleeve. Most B diesel engines have replaceable sleeves. When cylinders become worn, it is K relatively simple to remove the worn sleeve and install a new one. The cylinder I liner wall has fine finish I to minimize friction and B wearing due to sliding |motion. There are 2 types f I of liner, viz. wet liner, and I dry liner. Wet cylinder liner (Fig. 2.5d) is provided B with a flange at the top I which fits into the groove K in the cylinder block. At I the bottom of liner, grooves are provided for Fig. 2.5 d. Wet cylinder liner Fig. 2.5 e. Dry cylinder liner B rubber ring for sealing the I water leak. The liner is in direct contact with cooling water; therefore it is called I wet liner. A dry cylinder- liner (Fig. 2.5e) is made in the shape of a barrel having I a flange at the top which keeps in position into the cylinder block. This type of j liner is inserted in the worn cylinder bore after machining. Since it does not I come in direct contact with cooling water, hence it is called dry cylinder liner. Cylinder-liners are made of an alloy of cast iron that contains chromium, i
I
B
-
f.
a
Farm Machinery : Maintenance and Management
10
nickel and molybdenum. Chrome plating is used extensively to reduce wear. Cylinder liners have to withstand high pressure and temperature and heavy thrust of connecting rod. Piston Piston (Fig. 2.5f), when receives the force from the combustion within the cylinder, is forced downward and transmits motion to the crankshaft through a connecting rod. Pistons are designed to sustain severe operating conditions, viz. high compression pressures (900 psi or 63 kgf/cm2) and high exhaust temperatures (540째-600째C). Pistons are made of aluminum alloy due to light in weight and have better heat conductivity than cast iron. However, aluminum alloy has the disadvantage of expansion. Thus, the diameter at the piston crown is made smaller than the skirt so that after expansion both will be of approximately the same size. Cast iron or cast steel is used in heavy duty engines, viz. tractors, where high speeds and quick acceleration is not involved. Most automobile
I
Fig. 2.5 f. Piston assembly.
Fig. 2.5 g. Piston rings.
engines have aluminum alloy pistons because the lighter weight material permits
higher speeds and greater speed flexibility. It has excellent heat conductivity nearly twice as much as that of cast iron. There are 3 types of piston, viz. trunk type, composite and crosshead pistons. Piston rings (Fig. 2.5g) are used to maintain a tight seal in the combustion chamber during the combustion and power strokes. The primary function of the piston rings is to retain compression and at the same time reduce the cylinderwall and piston-wall contact area to a minimum thus preventing friction losses and excessive wear. It also scrapes the oil from the cylinder wall and prevents it from entering into the combustion chamber and also helps to transmit the greater portion of piston heat to cylinder walls. The piston ring is made of fine grained alloy cast iron and is provided with butt joint so that it can be fitted easily into the ring groove cut in the piston. The outer diameter of piston ring is slightly bigger than the piston diameter, so that when the piston ring is installed in the piston, it is pressed tightly against the cylinder wall due to its elasticity. Many of the piston rings are chrome plated for the purpose of reducing wear and scoring of cylinder wall. There are two types of piston rings, viz. compression rings (Fig. 2.5h) and oil
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