agriculture engineering-chptr 3

ENGINE LUBRICATION

Effects of Improper and Insufficient Lubrication

• Carelessness of the operator – time• Poor construction of bearings – lack of maintenance• Failure to provide adequate means of conducting

lubricants to the bearings - levelTherefore, lubrication is needed because of friction.

Friction

• Force that acts between two bodies at their surface ofcontact to resist the sliding of one body on the other.

Friction

Rolling Friction

• When one body rolls upon another, the friction ismuch less than when one body slides upon another.The resistance is called rolling friction

Friction Roller

Anti friction bearing

• In the form of balls or rollers to diminish the amountof friction. Therefore increase the efficiency ofmachine

The Present Condition of Friction

• Loss of horsepower – decrease 18%• Graduated loss of fuel economy• Frequent oil drains due to degradation• Component wear• Increased emissions• Rising maintenance cost• Rising labor cost

5 Functions of the Lubricant

1) Friction reduction2) Seal the cylinders3) Heat removal4) Cleanse5) Absorb shock

Purpose of Lubrication

• Helps the engine to run smoothly and last longer• Absorbs and dissipates heat• Helps in the cooling system• Prolongs engine life

3 basic types of engine lubricating system

a. Circulating Splashb. Internal Force Feed and Splashc. Full Internal Force Feed

a) Circulating Splash System

Used in small single cylinder air cooled engineA pump supplies oil to a splash pan under the crankshaft

As the connecting rod revolve, scoops on the end of rodsdip into trough and oil is gravity fed through channels orlines

The upper parts of cylinders, pistons and pins are lubricatedmore by oil mist taken by the oil splash. The mist is createdby the rapid movement of the connecting rods

b) Internal Force Feed and Splash

– A pump forces oil directly to a main oil gallery in the engine block rather than to a splash pan

– From main oil gallery, the oil is force through passages to the main bearings, camshaft bearings, rocker arm shaft, filter and pressure sending unit

– The oil escaping from the bearings creates a mist that also lubricates the upper cylinder walls, pistons and pins

c) Full Internal Force Feed System • Preferred in all modern diesel and petrol engines• Pump usually in the form of gear pump

– Oil is force not only to the crankshaft – bearings, rocker arm shaft, filter and pressure-sending unit,

but also to the piston-pin bearing– Piston pin bearing are lubricated through drilled passages

in the connecting rods. The cylinder walls and pistons are lubricated by

i) oil escaping from piston-pin bearing ii) or the connecting rod bearings iii) or by oil sprayed by the underside of piston and cylinder wall

How Full Force Feed System Work

Oil pump pushes oil through the systemA reserve of oil is stored in the crankcase for circulation through the systemAt the oil filter, dirt is taken out of the oil to help it keep cleanOil passages take the oil to engine parts where they provide lubrication and cooling and carry away dirt and depositsPressure of the oil is regulated by pressure regulating valveAfter oil moves through the whole system it comes back to the crankcase reservoir again

Pressure gauge tells the operator if engine oil is normal

Major Parts of Lubrication System

1. Oil pump2. Crankcase3. Oil cooler (if any)4. Oil filter5. Pressure regulating valve6. Pressure gauge

Criteria of Lubrication

1. Keep a protective oil film on moving parts2. Resist high temperatures3. Resist corrosion and rusting4. Prevent ring sticking5. Prevent sludge formation6. Flow easily at low temperature7. Resist foaming8. Resist break down after prolong use

Petrol Lubrication

• Is common to small two stroke engines, consist ofmixing a small quantity of oil with the petrol

• Ratio of oil to petrol vary from 16 parts petrol to 1part of oil for larger engine to 24:1 for smaller twostroke engines

Maintenance

1. Changing Engine Oilprolong using the oil will make the oil dirty and its additives wear out:-

• acid formations• sludge• varnish• engine deposits• contaminated oil will make it unfit for continued use

that will harm the vital engine parts

2. Follow the manufacturer’s recommendation on oil and filterchanges

e.g. 50 hours of working

3. When changing oil and filter on any engine, always warm upthe engine first. This way the contaminants and foreignmaterials are mixed with the oil and drained out with it

4. After installing the filter and filling the engine with oil, runthe engine and check for possible filter leaks

5. Keep a maintenance record of all oil and filter changes to besure of regular engine service

Classification of Oil• Lubrication oil are classified according to their viscosity

“thickness” and are given a number which tell us the grade of oil and in some cases the type

• Classification is by the Society of Automotive Engineers (SAE)

Engine oils are given this number SAE 10; 20; 30; 40Gear & transmission oil are given this number SAE 50; 70; 90Power system oil SAE 120; 140

• The lower number indicate low viscosity oil suited tocold climates or engines with many stop and startcontinually, therefore never reaching proper workingtemperature.

• The higher numbers indicate high viscosity moresuited to hot climates, or engines continually runningin hot conditions.

Detergent Oil• Oil that contains additives which prevent the

formation of carbon and lacquer inside an engine.• Used for lubrication of a diesel engine because when

diesel fuel burns in the combustion chamber itproduce sediments which stick to the working parts ofthe engine.

• This sediments collect on piston, piston rings andcylinder walls resulting in increased wear.

• The additives prevent this from happening by holdingin suspension the sticky particles which would settleon the piston.

Multigrade Oil

• Oil have special additives which reverse the normaltendency of an oil to thicken when cold and thin outwhen hot .

• They are numbered SAE 10-30 or 20-50 and arecalled viscostatic or Universal Engine Oil more suitedto petrol or propane engines.

Universal Oil

• These oil are produced to reduce the number ofdifferent types of oil needed to serve all types oftractor and implements, covering engines,transmission, hydraulic system, power steering, etc.

• These oil are of a multigrade in nature with suitableadditives to combat engine contaminants, gearboxstresses, anti frothing for hydraulic system and powersteering

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