OILOCCURANCE AND HISTORY

Petroleum formed several million years ago from organic matter of marine deposits in a deficiency of oxygen (anaerobic condition). Selective bacterial attack destroyed proteins and carbohydrates, leaving fats to accumulate as oil reserves.

FRACTIONS OBTAINED: USES:

1. Fixed and liquefiable gases Fuel gases, Alcohols, Light Naphtha, Petroleum ether

2. Light Distillates Gasoline, Naphtha, Kerosene,Solvents, Light lubricant oils

3. Intermediate Distillates Gas oil a) Heavy gas oil Heating fuels b) Light neutral oil Cracking stock

Absorber oil, Diesel

4. Heavy Distillates White oil (Heavy Neutral) Emulsifying oils,

(Insulating oils) Floatation oil Lubricating oils.

5. Residue after Vacuum distillation Petroleum Greases, coke, Asphalt.

6. Refinery sludge Sulphuric acid, sulfonicAcids, Acid coke, fuel oil

       All the crude oil consists mainly of hydrocarbons, but they differ in proportion of type of hydrocarbons.

1. Paraffinic base crude2. Naphthenic base crude3. Aromatic crude.

       In order to obtain the different kind of oils for suitable application where it is required, the crude must be refined through several process of distillation.

condenser

distillation LPGcolumn

Aviation PetrolPetrol

Crude oil feedingDiesel

Kerosene T.O (Insulating) oil

Furnace oil

Tar

Normally in many Thermal Power station we can mainly divide in to three divisions

.BOILER TURBINE TRANSFORMER1 Furnace Oil (F.O.) Lubricating oil Transformer oil2 Low Sulphur Heavy Stock (LSHS)3 Light Diesel Oil (LDO)

1 . FURNACE OIL

Indian Standard for Furnace Fuel Oil is IS 1593-1982Reaffirm in 1997

These fuel oils are primarily indented for oil-fired furnaces. This low viscosity oils is divided in to four grades.

SPECIFICATIONS REQUIRED AS PER IS STANDARD

S.No. Characteristics LV MV1 MV2 HV1 Acidity Nil Nil Nil Nil2 Ash % mass Max 0.1 0.1 0.1 0.13 Gross Calorific Value Kcal/Kg Not limited 10000 10000 100004 Relative Density 15/15 0C ’’5 Kinematics Viscosity at 50 0C 80 cst 125 180 3706 Flash point 0C 66 66 66 667 Sediment % by Mass Max 0.25 0.25 0.25 0.258 Sulphur 3.5 4.0 4.0 4.59 Water content ppm 1.0 1.0 1.0 1.0

1. Grade LV -- Low Viscosity2. Grade MV1 -- Medium Viscosity3. Grade MV2 -- Medium Viscosity4. Grade HV -- High Viscosity

Definition: A dark viscous residual fuel obtained from blending mainly heavier components from crude distillation unit, short residue and calorified oil from fluidized catalytic cracker unit.

NOMENCLATURE:

           Bunker Fuel, Furnace oil, fuel oil are other names for the same product though fuel oil is general term applied to any oil used for generation of power or heat. Fuel oil can include distillate and blends of distillate and residue such as light diesel oil.

END USE:Broadly the applications can be classified as:

Steam rising In the and thermal power stations.

Industrial Furnace Metallurgical furnace, Pottery and brick kilns,Cement and limekilns, glass furnaces etc.,

Special applications: Includes the following:i. Marine engines and slow speed engines, i.e.

generator for power generationii. Tea manufacturer.

Indirect firing process and direct process can be used. If latter is used low sulphur furnace oil is needed for tea manufacture.

I. FLASH POINT: As per controller of Explosives classification, furnace oil falls Class“C” category with minimum flash point. Standard of 66 oC. Since Penskey Martens closed cup method is used, it is apparent that a small quantity of low boiling point hydrocarbons is sufficient to lower the flash point drastically.

DEFINITION: It is the lowest temperature to which oil should be heated to generate enough vapor and to give a momentary flash when brought in contact with the test flame.

Description of Pensky-Martin’s closed cup apparatus : This is the most commonly used apparatus for determination of flash point of oils having flash points between 50 0C to 370 0C.

The apparatus consists of brass cup, which is 5 cm in diameter, 5.5cm in depth. The level up to which oil is to be filled in the cup is marked at about 1 cm below the top of the cup. Its flange supports the cup over a heating vessel in such a way that there is a clearance between the cup and the heating vessel. The cover for the cup is

provided with four openings of standard dimensions, which are meant for a special type of stirrer, a standard thermometer, an air inlet and a device for introducing the standard flame. The shutter is provided at the top of the cup has a lever mechanism. When the shutter is turned, openings fr the test flame and air are opened and the flame exposure device dips into the opening over the surface of the oil. The test flame gets extinguished when it is introduced into the opening for the test, but as soon s t returns to its original position on closing the shutter, the flame is automatically lighted again by the pilot burner.Procedure: Wash the cup provided for the test and its accessories with Benzene and dry perfectly. The oil is poured into the cup up to the mark. The lid is placed then, and the thermometer is fixed. The oil is heated at a steady rate by adjusting the theostat for oils with flash point between 40 0C to 150 0C, the rate is 5 to 4 0C per minute. For higher flash point (5 to 7 0C) ensuring constant stirring with a approximate 60 revolution/minute. When the oil temperature reaches 15 to 20 0C below the expected flash point, start introducing the test flame. The flame’s size should be adjusted to 3 to 4 mm. Do not stir the oil during the application of the fl

A blue halo around the test flame indicates that the flash point is heating. The temperature recorded on the thermometer when a distinct flash appears for the first time inside the cup is to be taken as the flash point of the oil. Oils containing minute quantities of volatile organic substances are liable to flash below the true flash point of the oil. Although a small slash may be observed in such cases, it should not be confused with the true flash, since its intensity does not increase with increased temperature as occurs when the true flash point reached. The minimum closed-cup flash point required for turbine oil is 165 oC and that for insulating oils is 145 0C. The flash point /fire point of the oils = ----0C. This is also calculated by multiplying the Heat of combustion KJ Mol -1 [Heat of combustion KJ gm -1 x mol. Wt.] by vapour pressure

[in bar] at 300 K (27 0C). II. POUR POINT:

It is a very rough indication of the lowest temperature at which furnace oil is readily pumpable. However, since practical conditions are quite different from those under which the laboratory test is conducted, many fuels can be pumped at temperatures well below their laboratory pour point.

III. WATER: Water may be present in free or emulsified form and on combustion can cause damage to the inside furnace surfaces especially it is contains dissolved salts. It can also cause spittering of the flame at the burner tip. Water content of furnace oil when supplied is normally very low as the product at refinery site is handled hot and maximum limit of 1% is specified in the standard. The higher the specific gravity and viscosity of a fuel, the greater the quantities of water it can hold in suspension

IV SEDIMENTS: Furnace oil being a blend of residues contains some quantity of sediments. These

have adverse effect on the burners and cause blockage of filters etc. However the typical values are normally much lower than the stipulated value of maximum 0.25% by mass. The higher the specific gravity and viscosity of a fuel, the greater the quantities of sediments it can hold in suspension. Large quantities of sediment can affect the combustion of the fuel. And if abrasive, may cause excessive wear of the closely fitting parts of fuel pumps and injectors. It may also clog filters EX: a)In TS-II so many tones of sediments kept in drums. Carried out variety of experiments to utilize but not feasible. b) Gas Turbines: It is suitable fuel for power generation by gas turbines. However, the extent to which pre-treatment of fuel is required is high, frequency of shutting down for over washing is very high and hence significant use of furnace oil has yet not started in this application. c) Fertilizer Plants: As a feed stock for fertilizer manufacture.

SPECIFICATION: Furnace oil in the current marketing range meets Bureau of Indian Standards

Specification IS: 1593 – 1982 for Fuel oils grade MV2.

SIGNIFICANCE OF PROPERTIES:

Viscosity: is the most important characteristic in the furnace oil specification. It influences the degree of pre-heat required for handling, storage and satisfactory atomization. If the oil is too viscous it may become difficult to pump, burner may be hard to light and operation may be erratic. Poor atomization may result in the carbon deposits on the burner tips or on the walls. The upper viscosity limited for furnace oil is such that it can be handled without heating in the storage tanks excepting under severe cold conditions. Pre heating is necessary for proper atomization.

Over a period of time with the addition of secondary processing facilities to extract more light and individual distillate the viscosity of furnace oil has gradually increased

Example: Good poor

CALORIFIC VALUE:

Calorific value of the fuel is the quantity of heat generated in kilocalories by complete burning of one-kilogram weight of fuel.

Gross calorific value is higher that net calorific value of the extent of heat required changing the water formed by combustion into water vapour. Former is more commonly used in practice EX: Bomb calorimeter.

DENSITY: At a given temperature it is the weight of a unit volume of oil and in metric system

expressed as gm/ml at 15 0 C usually . Furnace oil marketed on volume basis. Density of furnace oil, like for other petroleum products varies from batch to batch depending on numerous variables.

Density becomes important in certain applications where pre-treatment includes centrifuging to separate water as in the case of marine applications.

LOW SULPHUR HEAVY STOCK (LSHS) AND HEAVY PETROLEUM STOCK (HPS):

Definition : LSHS/HPS are residual fuels produced by processing of indigenous crude and

Mixture of indigenous and Middle East crude respectively. These are obtained in lieu of Furnace oil and are different from FO in respect in viscosity. This requires handling at temperatures above atmospheric level because of very high pour point.

This HPS is mainly used in Power plants, steel plants and other industries fuel. In Fertilizer plant as fuel as well as feedstock. In certain industries such as steel production where the products being heated directly comes in contact with the flame, the sulphur content of the fuel is important and may have undesirable effect in the quality of finished product HPS is produced in two grades.

1.Low Sulphur content2.High Sulphur content

HPS being solid at ambient temperature it has to be heated up before loading for transport by TOH wagon. Before decanting it has to be heated by steam. After melting the oil is transported to storage tank, which invariably heated and insulated.

REQUIRED SPECIFICATION AS PER IS STANDARD

S.No. Characteristics Grade I LS Grade II HS1 Pour point 0C Min. 66 722 Flash Point 0C Max. 76 663 Kinematic Viscosity m2/s @ 100 0C 50 504 Relative Density @ 15/15 0C 0.90 0.905 Gross Calorific value (above) Kcal/Kg 10000 100006 Acidity inorganic Nil Nil7 As % by Mass Max. 0.1 0.18 Sediment by Mass Max. 0.25 0.259 Total Sulphur by mass max. 1.0 4.510 Water content % by volume 1.0 1.0

Nomenclature: Residual Fuel oil, Hot Heavy stock, Fertilizer Feed stock are nomenclatures other than

LSHS/HPS for the same product.

END USE: These are used in lieu of furnace oil in the same applications where furnace oil is suitable.

FACILITIES REQUIREMENTS FOR LSHS/HPS: LSHS/HPS are marketed on weight basis as they are solids at ambient temperature.

Therefore, product has to be filled hot a temperature of about 10 0 C above pour point, in tank/lorries/tank-wagons. Means are available to heat the product if needed at consumer’s premises, for which tanker lorries or tenor-wagons are having steam coils and in certain areas heat traveling taps are around the tanker lorries. To reduce heat loses the tanker lorries and tanker wagons are insulated in certain cases. At the unloading point, saturated steam should be available at 3-bar pressure for heating tanker lorries and tanker wagons with steam coils.

The entire network of pipelines from tanker lorry unloading point to burners is steam tracked or auto electrical tape tracked and insulated. oil

Fuel oil pump house Boiler burner Steam

Main storage tanks and service tanks should have thermostatically controlled floor steam coils for maintain temperature or shall be tracked with electrical auto tracking.

Pumps normally of the positive displacement type are used for furnace oil. These are to be suitably tracked/steam jacketed and insulated.

FLUSHING SYSTEM: To take care of start up after prolonged shut down as well as emergency

shut down, it is necessary; to provide for flushing the fuel oil lines with same low pour point class “C” category fuel such as furnace oil. For this purpose a separate storage tank, pimps lines arrangements should be present.

SAFETY PRECAUTIONS IN HANDLING LSHS/HPS:

Water in main storage tanks if present should be drained out periodically through drain valve. To prevent boil-over of product, care should be taken to regulate the temperature to maximum of 90 0C. At least two thermometers of good accuracy; should be provided at different levels to measure product temperature in the tank. “Minimum of two free vents should be provided on the roof of the storage tanks with size bigger than the product receipt line. Automatic temperature controllers are recommended on steam inlet to storage tanks. Testing of steams coils should be undertaken at least once in every two years. Only dry chemical powder fire extinguisher should be installed. Precaution should be taken that during boil-over, foam is that injected in to the storage tanks as this would only aggravate the boil over”.

DIESEL FUELS:

REQUIRD SPECIFICATION AS PER IS:1460- 2000 STANDARD

S.No. Characteristics Requirements1 Total acidity Nil2 Ash Max. 0.23 Carbon residue % 1.504 Pour point 12 0C (W ) 2 1 0C (S)5 K.Viscosity @ 380C 2.52 to 15.7 cst6 Flash point 667 Sediment Max 0.108 Total sulphur Min. 1.89 Water Content % by mass 0.25

a. Definition : A diesel fuel I any fuel suitable for burning or compression ignition engines.

b. NOMENCLATURE: Two main grades of diesel fuel are marketed in India, High Speed Diesel ,(HSD)

and Light Diesel Oil ( LDO ). The former is a 100% distillate fuel while the latter is blend of distillate fuel with a small proportion of residual fuel.

c. END USE: HSD is normally used as a fuel for high speed diesel engines operating above 750 rpm i.e.

buses, lorries, generator seta, locomotives, pumping sets etc. LDO is used for diesel engines generally of the stationary type operating below 750 rpm..

d. SIGNIFICANCE OF PROPERTIES:

e. Ignition quality: When fuel is injected in to the combustion chamber of a diesel engine, ignition does not occur

immediately. “The interval between the commencement of fuel injection and the commencement of combustion is known as the ‘ignition delay’ and is a measure of the ignition quality of the fuel.

f. Cetane number:

The most accurate method of assessing the ignition quality of a diesel fuel is by measuring its cetane number in a test engine, “the higher the cetane number the higher the ignition quality”.

g. Viscosity: When we move our finger through water contained in a tank, we experience a resistance.

This shows that water offer a frictional force. This frictional force will be more in the case of glycerin and castor oil. This force offered by the liquid is known as viscous force and is due to a property

known as the viscosity of the liquid. When a liquid flows slowly and steadily through a pipe the layer A of the liquid in contact with the walls of the pipe is practically stationary while the liquid along the axial line C has a maximum velocity. The layers in between A & C have progressively increasing velocities. The length of the arrows represents the progressively increasing velocities of the layers from A & C.

A

C

B“If the viscosity of the fuel is too high it will impede the flow of fuel to the pump,” giving rise to poor atomization and excessive penetration with in efficient combustion of fuel.

h. CARBON RESIDUE:Different fuels have different tendencies to crack and leave carbon deposits

when heated under similar conditions. A sample of fuel is heated without contact with air under specified conditions and weight of carbon residue remaining after the test is expressed as a % of the weight of the sample.

i. VELOCITY: As a rule, the higher the viscosity of a liquid fuel the lower its velocity.

j. TOTAL SULPHUR: This is significant because it governs the amount of sulphur oxides formed

during combustion. Water from combustion of fuel collects on the cylinder walls, whenever the engine operates at low jacket temperatures. Under such conditions, sulphurous and sulphuric acids are formed which attack the cylinder walls and piston rings, promote corrosion and thus cause engine wear and deposits.

The above effects can do some extent be overcome by the use of lubricant containing alkaline additives. If the diesel fuel is refined from a very high sulphur crude, it may become necessary to desulpurise it before marketing.

k. CORROSIVE SULPHUR: It is important that diesel fuels shall be free of these sulphur compound

which in themselves attack metal parts of the engine or the fuel system. This characteristic is tested by; the copper strip corrosion test, a severe discoloration or pitting of the polished strip indicating the presence of corrosive sulphur compounds in the fuel.

l. ACIDITY: This should be low in order that corrosion of metals in contact

with the fuel during storage and distribution is minimized.

m. INORGANIC OR MINERAL ACIDITY: Where diesel fuels are tested with mineral acid as part of the refining

procedure, traces of minerals acid remaining in the final product would obviously be undesirable. Hence, zero limits is usually specified for this property.

n. ORGANIC ACIDIY: This is due acids of the naphthemic type which are constituents of crude

petroleum. Although much weaker than mineral acids, they may attack galvanized metal and this is why the use of galvanized containers for the storage of diesel fuel is not recommended..

o. ASH CONTENT: Ash is a measure of the incombustible material present in a fuel and is

expressed as a percentage of the weight of the fuel sample. In the case of distillate fuels, it usually consists of rust, tank scale or sand, which settles out readily. Blends of distillate and residual fuel Ex: LDO may additionally contain metal oxides derived from oil soluble and insoluble metallic compounds. As is significant because it can give rise to deposit problems such as abrasion, malfunctioning of injectors and high temperature corrosion, particularly with residual fuel.

p. SEDIMENT AND WATER: Undesirable.

q. POUR POINT: Lowest temperature at which fuel flows.

r. COLD FILTER –PLUGGING POINT: (CFPP) Defined as the highest temperature at which the fuel, when cooled under

prescribed conditions, either will not flow through the filter (45 microns) or will require more than 60 seconds for 20 ml to pass through. This is the temperature at which wax crystals begin to cause blockage of filters.

s. FLASH POINT:Important largely from the point of view of safety in handling the fuel. LDO flash

point 66 0C . Class ‘C’.

t. SPECIFIC GRAVITY:Defined as the ratio of the weight of a given volume oil to the weight of the same

volume of water at a given temperature. Another index is mass per unit value at a standard temperature. Ex: 100 ml of oil weighs = 89 gms

100 ml of water weighs = 100 gms Sp. Gr. of oil = 89/100 0.89

TRANSFORMER OIL

SPECIFICATIONS REQUIRED AS PER IS: 335-1993 FOR NEW T.O OIL

S.No. Characteristics Requirement1 Appearance The oil should be clear and transparent

and free from suspended matter of sediments.

2 Density @ 29.5 0C 0.89 gm/cm23 Kinematic Viscosity at 27 0C 27 cst4 Interfacial tension @ 27 0C min. 0.04 N/m5 Flash point 140 0C6 Pour point - 6 0C7 Acidity max. 0.03 mg of KOH/g8 Elect. Strength (BDV)

a) New Oilb) After filtration

30 KVIf the above value is not attained the oil shall be filtered 60 KV

9 Di-electric dissipation factor tan @ 90 0C max. 0.002

10 Sp. Resistance (Receptivity)a) @ 90 0Cb) @ 27 0C

35 x 1012 ohm-cm1500 x 1012 ohm-cm

11 Neutralization value after oxidation max. 0.4 mg KOH/g

12 Water Content ppm max. 35

SPECIFICATIONS REQUIRED AS PER IS: 1886 – 1983 FOR MAINTENANCE AND SUPERVISION OF MINERAL INSULATING OIL IN EQUIPMENT

S.No. Tests Transformer Voltage Rating

Limits

1 Interfacial tension N/m For all voltages 0.015 Max2 Flash point 0C For all voltages Decrease by 15

0C3 Neutralization value of mg of

KOH/gFor all voltages 0.3 max

4 Break down voltage (BDV) Above 170 KVBetween 72.5 to 170 KVBelow 72.5 KV

30 min50 min40 min

5 Dielectric dissipation factor @ 90 0C

Above 170 KVBelow 170 KV

0.2 max1.0 max

6 Resistivity (x 1012 Ohm-cm) For all voltages 0.1 min7 Water content ppm Above 170 KV

Between 72.5 to 170 KVBelow 72.5 KV

20 max20 maxNo free moisture

8 Sediment & sludge For all Voltages Nil

Electricity is now an integral component of modern civilization and an essential input for Agriculture, Industry, Transport and quality of life. With the extension of electricity to rural areas, the number of transformers both power and distribution type installed in the country are about twenty lakes with increasing annual average rate of around 10%. The failure rate of distribution transformers varies from 9% to 20% in different states, which is very high when compared to international standards. In advanced countries the failure rate is generally less 2%.

The main reason for failure of Distribution Transformers (DT) can be broadly divided in three categories:

1. Due to poor quality of Transformers2. Due to improper maintenance3. Due to poor protection.

The majority of Distribution Transformer failure comes under first two categories where transformer oil is one of the main reason initiating and causing failure of DTs.

INTRODUCTION: Transformer oil is a product of petroleum origin. Oil is said to be composed of hydrocarbons and non-hydrocarbons. The hydrocarbons present are more in numbers. It can be divided in three major groups.

4. Paraffinic base crude5. Naphthenic base crude6. Aromatic crude.

The manufacture of Transformer oil is by the fractional distillation of crude under reduced pressure. The highest fraction obtained after dewaxing with propane is further refined by chemical means to yield transformer oil.

In order to accomplish multiple role by transformer oil like

1. The role of dielectric medium2. Heat transfer agent or coolant3. Arc-quencher.

The oil must possess following basic properties:

1. High electric strength 2. Sufficient low viscosity 3. Adequate low temp. Properties 4. Proper oxidation resistance

Transformer oil in service is subject to deterioration due to condition of its use, elevated temperature, presence of metals, organic compounds or both. Air acting as oxidation promotor. At an advance stage of oxidation, separation of sludge may occur. Similarly change in colour formation of acidic compounds and dielectric properties may be impaired. In addition, many other contaminants like water, solid particles and oil soluble *polar compounds may accumulate in the oil during service

* Polar compounds = Soluble in water.

POLAR COMPUNDS:

In Power Transformers, transformer oil heats up at winding due to the power loss in the coil and the magnetic core and transfer heat to the cool walls of transformer tank. In high voltage oil circuit breakers, the liquid dielectric serves not only to insulate the conductivity parts but also as a suppressive medium that quenches an arc discharge between the disengaging contacts.

MAIN CAUSES FOR DETERIORATION OF OIL OR:

MAIN CAUSES FOR DETERIORATION OF OIL1.Physical contaminating:- due to Contact with construction particles Fibrous materials Dissolution of varnish Moisture

2.Chemical contamination:- due to Thermal decomposition Oxidation Catalytic effect of construction materials Reaction of acids with paper and metal parts Sludge.

3.Contamination by gases:- Gases those dissolve in oil from atmosphere Gases those are generated due to various reaction.

TESTING The testing of fresh oil samples used oil samples or deteriorated oil samples can be done

by physical, chemical and electrical testing.

Physical Test : Appearance Density Viscosity Pour point Flash point Interface tension

B. Chemical Test: 1. Neutralisation Number : Is the determination of acidic constituents in the insulating oils. Leads to formation of sludge, metal surface corrosion and lowering of electric strength

2. Corrosive Sulphur : Indicates presence of Sulphur, which is corrosive in nature and corrodes the copper

surfaces.

Oxidation Stability:

Covers the evaluation of acid and sludge priming tendency of new mineral oils.

Water Content: by moisture entry into oil by accidental leakage by breathing action. During oil filling or topping up. Chemical reaction.

C.ELECTRICAL TEST;- Electrical strength : (Break down voltage - BDV)

is the voltage at which arc discharge occurs between the electrodes with 2.5 mm gap.Dieletric dissipation factor: Dissipation factor = Power loss in electric / apparent power (volt-ampere) is the measure of dielectric losses in oil and hence the amount of heat dissipated.

Low value indicates low losses. Resistivity:

Provides a sensitive method of determining the conducting impurities. affects the electrical losses and causes deterioration of oil causing equipment failure.

GAS IN OIL ANALYSIS. Is used to evaluate physical condition of transformer with regard to arcing, hot spot and paper deterioration. For this analysis high performance liquid chromatography (HPCL) and gas chromatography (GC) techniques are used.

Gas observed in oil 1. N2 + 5% or less O2 2. N2 + more than 5% O2 3. N2 + CO2 + CO 4. Nitrogen + H2 + Methane 5. N2 + H2 + other hydro- Carbon including Acetylene

STATE OF ART OF TRANSFORMER OIL:

CONSTITUENTS OF PETROLEUM:

The main elemental constituents of petroleum are carbon and hydrogen, together with small amount of metals such as vanadium, sodium, nickel and iron. The carbon and hydrogen are present in paraffinic, naphthaenic and aromatic hydrocarbons: whilst sulphur, nitrogen and oxygen are present with carbon and hydrogen in what is termed as hetero compounds.

PRODUCTION OF INDEGENOUS TRANSFORMER OIL:

The indigenous production of insulating oils commenced in 1969. Till then the product was being imported from western sources. Important characteristics of the transformer oil feed stock (TOFS) are sulphur content, aniline point, pour point, viscosity and armatic content must be kept within permissible limits.

INSTALLED CAPACITY AND DEMAND:

A working group of the Planning commission estimated in 1966 the requirement of new transformer oil as 1100 MT for addition of every one million kilowatts (I.e 1000 mega watts) of power for growth in power generation capacity: Based on these norms and the plan forecasts for growth in Power generation capacity, Government initially licensed in 1966 the organized sector to manufacture 30,000 MT of Transformer oil. Subsequently, based on the committee’s power plan further about 65,000 MT were licensed/registered in the medium and small sector. The manufacturing capacity in various different regions of the country given at present is more than 1.0 lakh MT.

CHEMISTRY AND MANUFACTURE OF TRANSFORMER OIL:

In power transformers, transformer oil heats up at windings due to the power loss in the coil and the magnetic core and transfers heat to the cool walls of transformer tank. In high voltage oil circuit breakers, the liquid dielectric server not only to insulate the conducting parts but also as a suppressive medium that quenches as arc discharge between the disengaging contacts.

Of all the liquid dielectric petroleum oils are mostly widely spread. These petroleum oils are obtained by the fractional distillation of petroleum, which is a complex process.

CRUDE DISTILLATION:

The first step in producing transformer oil is distillation of crude to produce a suitable distillate feed stock. The distillate can be taken as a side stream product from either the atmospheric tower or vacuum tower.

Low boiling fractions are removed in pre-fractionation. Middle boiling fractions are removed in Atmospheric tower. High boiling fractions or reduced crude from the bottom of the atmospheric tower

then goes to the final or vacuum tower. This is done in order to keep the boiling point of fractions well below cracking temperature. The distillate obtained during this process will be call as Transformer oil feed stock.

REFINING OF DISTILLATE:

a)CHEMICAL REFINING: Acid Treating:

In this process the oil fraction is treated with concentrated sulphuric acid. The oxygen, sulphur and nitrogen compounds along with undesirable hydrocarbon are removed in the form sludge. The amount of acid used and the time of contact depend upon the concentration of impurities in oil. During this treatment, the oil is continuously agitated and reacted in large vessels with conical bottoms for sludge drainage. After the sludge has settled down, the oil is drained off, washed with water and treated with 10-25 % solution of NaOH (alkali wash). This alkali neutralizes the acids completely and subsequently removed by water washings.

Acid Treating:

H2SO4

Water Alkali wash 10-25 % NaOHOil

Oil Oil

Neutralized oil

O,S,N compounds + Hydrocarbon as sludge

Clay Treating:

Alcohol water

Neutralized oil

ElectricalInsulating oil

Steam

Residual traces of Sodium Sulphonate

b) Hydro Treating: This process makes use of hydrogen, which reacts with sulphur,

nitrogen and oxygen compounds of the oil. The reaction takes place at elevated temperatures and pressure over a fixed bed catalyst. Generally a pressure of 35-40 tonnes per sq. mtr. And a temperature of 300-400 oC over cobalt or molybdenum sulphide or “alumina” as catalyst are employed. The products of reactions are stable hydrocarbons similar to ammonia naturally occurring hydrocarbons. Gases such as hydrogen sulphide, ammonia and water are removed. After hydro treating step, the oil goes to steam stripper where the gaseous reaction products are removed. The hydro treated oil by itself is not usually a satisfactory product. The process is too mild to remove all deleterious compounds. Therefore clay percolation or solvent extraction must be used to arrive at finished oil.

c. Solvent Extraction: This process is used in conjunction with the acid or hydro refining and is

applied to crude distillate shaving high aromatic content. In this process, the distillate is mixed with a solvent and is allowed to settle (using immiscible or partly miscible). The solvent should be more dense than the oil and selective or aromatics. The extracted oil (raffinate) containing some dissolved solvent goes to stripping system where the solvent is recovered and reused. The solvents that are used to treat transformer oil or phenol, n-mthryl-pyrolidine and liquid sulphur dioxide.

d.Solvent Dewaxing: Dewaxing is not required if the crude is Naphthaenic but is required for oils

made from paraffinic crude or waxy napthenic crude. In this process, waxy oil is mixed with a suitable anti-solvent for wax and chilled to a low temperature to cause, the n-paraffins to precipitate. The wax is then filtered off usually as a rotary filter. The solvent is recovered from the dewaxed oil and wax for reuse. The typical solvents that can be used for the process are liquid propane, methyl ethyl ketone and methyl isobutyl ketone.

e.Catalytic Dewaxing: The equipment used is similar to that used in hydro treating. The dewaxing

catalyst ‘mordenite’ can be best visualized as hollow sphere with hoes in the sides leading into the interior cavity. The hole size is such that a straight chain hydrocarbon (n-paraffin) can protrude through the hole into the interior but the branched chain iso paraffin or cyclic structure cannot encounter the catalyst. If the waxy oil fed into unit is mixed with hydrogen gas at elevated temperature and pressure and allowed to flow over the catalyst just as in hydro treating. The normal paraffin entering the catalyst is cracked off in typical units of 3 carbons (Propane). This process is capable of producing dewaxed oils with very low pour points. (50 oC)

PHYSICO-CHEMICAL ASPECTS OF REFINING:

PARAFFIN: n-paraffins are removed by solvent dewaxing and hydro treating.

Iso paraffins and naphthalenes are not affected by any process except that small amounts may be solublized into extract phase in solvent extraction.

Olefins are removed by acid treating, while hydro treating hydrogenation converts them to saturated hydrocarbons, which remain in oil.

AROMATICS : Highly condensed aromatics are removed by acid treating hydro treating converts

some of them into partially saturated hydrocarbons. Depending on the severity of process, hydrogenation can fully saturate the aromatics. Solvents extraction fully removes condensed aromatics. Clay treating, solvent dewaxing and hydro dewaxing have no effect on condensed aromatics.

SULPHUR COMPOUNDS: Benzothiophenes can be removed by acid treating. Hydro treating can totally

convert them to desulfurized hydrocarbon. Solvent extraction can also remove Benzothiphene. Clay treating, solvent dewaxing and hydro dewaxing have no effect on Benzothiphenes.

NITROGEN COMPOUNDS: Quinoline type compounds can be removed by acid treating and clay; treatment. Hydro

treatment with severity can convert quinoline to Denitrogenated hydrocarbon. Solvent extraction removes partially the qunioline. Solvent dewaxing and hydro dewaxing have no effect on quinoline content.

POLAR OXYGEN COMPOUNDS:

Naphthaoic acid type compounds are removed in acid treatment and clay treatment. Hydro treatment converts them to saturated naphthenics. Solvent extraction. Solvent dewaxing, hydro dewaxing have no effect.

UNIT PROCESS EFFECTS ON OIL PROPERTIES:

One can obtain transformer oil by many; different process sequences. Some of the various combinations that have been reported are:

a. Acid treating, clay treatingb. Hydro treating, clay treatingc. Hydrogenationd. Solvent extraction, hydro treatinge. Solvent extraction, hydro treating, clay treatingf. Solvent extraction, hydro treating, dewaxingg. Hydro treating, solvent extraction, dewaxing, clay treating.

ACCEPTABLE LIMITS FOR TRANSFORMER OIL BASE STOCK

Properties Acceptance limits1 Density at 150 oC 0.89 to 0.9052 Viscosity at 40 oC 11 – 133 Viscosity Index 64 – 704 Colour < 25 Pour Point oC -10 to 206 Flash Point oC 150 – 1707 Sulphur content % 1.7 – 2.5

ELECTRICAL PARAMETERS

1. DIELECTRIC STRENGTH:

It is the minimum voltage at which oil breaks down when subjected to a continuously ac voltage. It is expressed in kV. It is popularly known as Break Down voltage (BDV). BDV of oil is the ac voltage, which sparks between two electrodes placed in the oil under test at a standard distance (generally 2.5 mm as per most standards). The voltage being applied is raised at a specific rate. BDV is the single most important and popular test to gauge condition of oil on site. It is indicative if solid impurities and water content present in the oil. Dry and clean oil exhibits normally high Break down voltage. However high BDV doesn’t necessarily indicate absence of all above contaminations.

The gap between electrodes, shape of the electrodes and temperature of the sample are important parameters, otherwise the results will not be correct one.

Electrodes

Oil bath (.5 to 1 lr.)

Connected toServo motor

2. SPECIFIC RESISTANCE:

Also call resistivity of DC resistance of volume of oil of unit cross sectional area and unit length. Prevalent unit is ohm-cm. It is desirable to have Specific resistance of oil as high as possible. Resistivity of oil varies greatly with temperature of oil, an increase in temperature reduces the resistivity.

Resistivity of oil reduces considerably due to presence of moisture, acidity and solid contaminants. Contamination of oil, which would not otherwise be detected by acidity test, will immediately be indicated by changes in the value of resistivity. Resistivity

100 Kv

2.5 mm gap Oil .

measurements are carried out at 90 oC for monitoring purpose. New oils are tested both at room temp. (27 oC) as well as at 90 oC. A satisfactory value at 90 oC and unsatisfactory values at room temperature is an indication of the presence of water or degradation products preciptable in the cold but generally at a tolerable level. Unsatisfactory results at both temperatures indicate a greater extent of contamination and it may not be possible to restore the oil to a satisfactory level by reconditioning.

3. DIELECTRIC DISSIPATION FACTOR:

It is the tangent of the loss angle. Dielectric dissipation factor is also known as tan-delta or loss factor. In a pure insulating media the phase angle between voltage and current will be 90 0 and the loss will be zero. But in all practical cases the angle will never be 90 0, but slightly lesser by an angle which causes the loss. The tangent of this loss angle is called dielectric dissipation factor.

Dielectric dissipation factor is strongly affected by presence ionizable contaminants present in oil. Hence it is measure of contaminants and deterioration by products like acids sludge etc.

I I” I

= 90 0 = 900 -

V V

PHYSICAL PARAMETERS:

1. INTERFACIAL TENSION:

Inter facial tension between the water and oil interface is the way to measure molecular attractive force between the molecules of water and oil. It is expressed in Dynes/cm or mille Newton/m. It is measured using platinum ring tensiometer. A planner ring is first placed in the interface of water and oil and then it is lifted using a torsion wine into oil. The force required to lift the ring from the interface is proportional to the interface tension.

Interfacial tension is extremely useful for determining the presence of polar contaminants and oil decay products. Good new oil generally exhibits high interfacial tension. Oil oxidation contaminants lower the IFT. This is due to the reason that they have a high affinity towards water molecules (i.e. hydrophilic in nature) as well as the oil molecules. At the interface they extend across to the water, thus a vertical force is excerted reducing he lateral tension. Increase in oxidation contaminants causes more reduction IFT.

SAMPLING AND TESTING OF OILS1. Occurrence

2. Classification of Crude Petroleum3. Table – I4. Oils----------------------------------------------------------------------------------

Boiler Turbine Transformer

5. Furnace Oil - Definition - Nomenclature

- End use

Analysis: a. Flash point b. Pour point c. Water content

d. Sediment e. Viscosity f. Calorific Value Significance of properties. g. Density

6. LSHS: - Definition

- Nomenclature- End use.- Facilities for LSHS- Flushing system- Safety in handling

7. DIESEL FUELS (LDO):

a. Definitionb. Nomenclaturec. End use.d. Properties -----

1. Ignition quality 9. Inorganic or mineral acidity2. Centane number 10. Organic acidity3. Viscosity 11. Ash Content4. Carbon reside 12. Sediment and water5. Volatility 13. Pour point6. Total Sulphur 14. Cold filter plugging point7. Corrosive sulphur 15. Flash point8. Acidity 16. Specific gravity

17. Cleanliness

LUBRICATING OILS:

- History- Categories of L.O.S- Viscosity- Viscosity index- Pour point- Oxidation stability- Rust prevention- Resistance to emulsification-demulsification- Resistance to foaming- Antiwear property- Oiliness and film strength- Tackiness

In TS-II a. Boiler Feed pump for all 7 units (3 x 7 = 21 samples) Viscosity @ 50 oC b. Main oil Tank Viscosity @ 40 oC

TRANSFORMER OIL:

- History ---- 20,00,000 transformers with 10 % increase every year.- - ---------------------------------------------------------------- Constituents of Production of Installed capacity & - Petroleum indigenous T.O –1969 Demand 1100 MT

For every 1000 MW

- Introduction – State of art of Transformer oil.- Physical contamination- Chemical contamination Main Causes for deterioration of oil.- Contamination by gases

TESTING:

PHYSICAL TEST: - Appearance - IS 335 * - Density - 0.85 to 0.89 gm/cc

- Viscosity- Pour point- Flash point- Interfacial tension

CHEMICAL TEST:

- Neutralization number (Total acidity and Inorganic acidity)- Corrosive sulphur- Oxidation stability- Water content

ELECTRICAL TEST:

- Electrical strength (BDV)- Dielectric dissipation factor- Resistivity

GAS IN OIL ANALYSIS:

Std. Ppm Conc. Std. Area.

- Methane (CH4) 103 4688- Ethylene (C2H4) 109 7155- Ethane (C2H6) 109 5149- Acetylene (C2H2) 120 7912- Propane (C3H8) 102 9682

Ppm of constituent gas = Std. Ppm x Sample area x Volume of gas evolved

Std. Area Qty. of oil sample

Ex: Unit auxiliary Transformer:

CH4 ppm 103 x 7722 x 5.2 4688 100 = 8.82

PERMISSIBLE CONCENTRATION OF DISSOLVED GASES IN THE OIL OF THE HEALTHY TRANSFORMER.IN SERVICE.

GAS LESS THAN 4 YEARS I 4-10 YEARS MORE THAN 10 YEARSMethane 50/70 ppm 10/150 ppm 200/300 ppmEthane 30/50 ppm 100/150 ppm 800/1000 ppmEthylene 100/150 ppm 150/200 ppm 200/400 ppmAcetylene 20/30 ppm 30/50 ppm 150/200 ppmHydrogen 100/150 ppm 200/300 ppm 200/300 ppmCO2 300/3500 ppm 400/5000 ppm 9000/12000 ppmCO 200/300 ppm 400/500 ppm 600/900 ppm

A N A L Y S I S

In our Thermal Power Station - II there are 21 Feed pumps in total with each Unit has 3 pumps. Main Oil Tank (MOT) = 7 Nos. Total = 28.The following analysis is being carried out in oil.

FURNACE OIL LUBRICATING OIL TRANSFORMER OILViscosity Viscosity ViscosityMoisture Moisture MoistureSediments Sediments SedimentsFlash Point Flash Point Flash Point

-- Acidity Aidity-- Oxidation Stability Oxidation Stability-- -- Dissolved Gas Analysis

Calorific Value -- --Sulphur -- --Density -- --

1. MOISTUREBy Crackle Method: A trace of moisture is determined by this method. A small portion of oil is mixed well and taken in a perfectly dry test tube and heated over a sprit lamp with slight agitation. The production of “crackling sound” indicates the presence of moisture.

By Dean and Stark method: Moisture can be determined quantitatively by Dean & Stark method using Xylene as extractor of water.

Apparatus Required: (1) Round Bottom Flask,(2) Leibig condenser, (3) Dean & Stark receiver (entire set with assembly) (4) Heating mantle (5) Xylene.

Procedure: Take a known weight of the oil sample and put in the Round bottom flask, add 50 ml or required quantity of Xylene to make the sample immersed completely in Xylene. Heat it over the heating mantle up to boiling point. The boiling point of the solvent should be greater than 100 oC (B.P. of Xylene is 130 oC). Carry out the analysis with all fittings are in air tight with a slow stream of water is circulated. Heat gently on the heating mantle and maintain uniform distillation for about ½ an hour. The evaporated water particles in the oil will condense and collected in D&S measuring apparatus. Note the volume of water collected in the receiver.

% of Moisture = (Wt.) Volume of the water collected x 100 Weight of the oil taken.

2.VISCOSITY Viscosity is a measure of flow ability at definite temperature. It is the most important property of oil as at operating temperature, it is viscosity that determines fluid friction (friction within the oil itself). Any change in viscosity indicates the contamination or oxidation instability. Viscosity is the most important characteristic in the Furnace oil specification. It influences the degree of free heat required for handling storage and satisfactory atomization. If the viscosity of the fuel is too high it will impede the flow of fuel to the pump giving rise to poor atomization and extensive penetration with in effective combustion of fuel.

Viscosities are higher if the compound has ore hydroxyl groups (network of hydroxyl bonds) which makes flow difficult. Viscosity of a liquid decreases as temperature increases. Kinematic viscosity deals pure motion without reference to the masses of a fluid. Kinematic viscosity is the quotient of absolute viscosity divided by density both at the same temperature.

Kinematic viscosity is determined by measuring the time required for a given volume of oil to flow through a capillary tube under the force of gravity. The unit of kinematic viscosity is stoke or centistokes (1/100 of stoke).

Apparatus Required: 1. A Cannon & Pensky viscometer of desired viscosity range 2. Water bath for temp. at 80 oC 3. Thermometer.

Procedure:- Calibration: Note the efflux time of the viscometer with the help of A.P.I. liquid viscosity std. or any std. viscometer supplied by the companies whose viscosity constant is known can be use.Calculate the viscosity constant as under

C = Vk / t where Vk = Kinamatic viscosity of the given std. oil at the test Temperature in centistokes. t = efflux time in seconds. Before preceding the analysis ensure that the viscometer is cleaned perfectly with completely volatile liquid and dried out. Charge the viscometer with a portion of the filtered oil sample. Provide the viscometer with a firm mounting which will eliminate disturbances in its position when it is in the bath. The water in the bath should have its upper level at least 5 cm above the top of the liquid level in the capillary part of the viscometer. Make certain that the viscometer is vertical when compared with a plum line observed from two directions about 90 o apart. Introduce the stirrer to maintain uniform distribution of temperature.

Allow the charged viscometer to remain in the bath a long enough to reach the test temperature. When the test temperature remains steady for 10 mts suck the oil level a little above the graduated mark and then allow it to pass. When the oil level crosses the mark, start a stop watch at once. Note the time taken for the oil to flow up to the mark below from the top one. Repeat the experiment.

Kinamatic Viscosity in centistokes / sec = Viscosity co-efficient of viscometer x Time taken in seconds of flow between two marks = Ct.

3. ACIDITY (For Lubricating oil only) It is defined as number of mg of KOH required to neutralize the acidity presence in 1 gm of the sample. This should be low in order to minimize the corrosion of metal where contact with the fuel during storage and distribution.

Procedure:- Alcoholic KOH 0.05N (3.22 gm of KOH is dissolved in 1 lr. of Methyl alcohol) 3.22 gm of KOH flakes dissolved in 2 to 3 ml of DM water and then add Methanol. Take approximately 10 gm of the oil in a conical flask, mix 30 ml of Toluene with 20 ml of Methanol and add alkaline blue indicator. Add drops of alcoholic KOH until the colour changes from blue to wine red. Add the mixture in the conical flask and titrated against alcoholic KOH. E.P. green to blue.

T.V x 2.805 Wt. of oil = mgm of KOH / gm of oil.

Take 10 ml gm of the oil in a 250 ml conical flask. To a mixture of 30 ml of Toluene and 20 ml of Methanol in another flask, add 1 to 3 ml of 2% alkali blue solution and a drop of 0.1N HCl to sensitize the indicator. Neutralize the mixture with the KOH to the appearance of a strong wine red colour. Add the neutralized mixture to the sample in the conical flask with swirling. If the mixture assume a purple blue colour after the sample is completely dissolved, titrate it at once with the 0.05N KOH solution at a temp. 30oC. E.P purple to red.

Vol. of KOH consumed x Normality of KOH x 56.1 Weight of the sample taken = mg KOH / gm of oil

4. SEDIMENTS: Oil being a blend of residue contains some quantity of sediments. These have adverse affect on the burners and cause blockage of filters etc. However the typical values are normally much lower than the stipulated value of maximum 0.25% by mass. The higher the specific gravity and viscosity of a fuel, the greater the quantities of sediments it can hold in suspension. Large quantities of sediments have affect the combustion of the fuel and if abrasive may cause excessive wear of closely fitting parts of fuel pump and injectors. It may also clog filter and build up deposits in tank and piping.

Determination: Sedimentation Cone Method : . Shake the sample well until the sediments are homogenously distributed and transfer 50 ml (or a lesser amount for high viscosity oils) to a sedimentation cone. Add 50 ml of Benzene and shake well. Allow to settle for 24 hrs.

Transfer the mixture in parts to two centrifuging tubes and continue the process till the entire sample from the sedimentation cone is exhausted. Then filter the sediments through 42 filter paper. Wash it free of oil with Benzene

The contents are transferred to a pre-weighed and dried washing bottle and dried in an air oven.

n at 105 oC for 10 mts and cooled in a desicator for the same period of time. Reweigh the weighing the bottle and express the result in term of % sediments settled.

5. FLASH POINT The minimum temperature to which the oil must be heated to give enough vapour, which confirm a combustible mixture with air. Otherwise liquid having flashpoint < 20oC are considered to be highly flammable. A liquid is highly inflammable if its flash point is lower the surrounding temperature. It is the lowest temperature to which an oil should be heated to generate enough vapors and to give a momentary flash when brought in contact with the test flame. F.P. can be determined by using Pensky-Martein’s closed apparatus.

Description of Pensky-Martin’s closed cup apparatus: This is the most commonly used apparatus for determination of flash point of oils having flash points between 50oC to 370 oC.

The apparatus consists of brass cup, which is 5 cm in diameter, 5.5cm in depth. The level up to which oil is to be filled in the cup is marked at about 1 cm below the top of the cup. Its flange supports the cup over a heating vessel in such a way that there is a clearance between the cup and the heating vessel. The cover for the cup is provided with four openings of standard dimensions, which are meant for a special type of stirrer, a standard thermometer, an air inlet and a device for introducing the standard flame. The shutter is provided at the top of the cup has a lever mechanism. When the shutter is turned, openings for the test flame and air are opened and the flame exposure device dips into the opening over the surface of the oil. The test flame gets extinguished when it is introduced into the opening for the test, but as soon s t returns to its original position on closing the shutter, the flame is automatically lighted again by the pilot burner.

Procedure: Wash the cup provided for the test and its accessories with Benzene and dry perfectly. The oil is poured into the cup up to the mark. The lid is placed then, and the thermometer is fixed. The oil is heated at a steady rate by adjusting the theostat for oils with flash point between 40 oC to 150 oC, the rate is 5 to 4 oC per minute . For higher flash point (5 to 7 oC) ensuring constant stirring with a approximate 60 revolution/minute. When the oil temperature reaches 15 to 20 oC below the expected flash point, start introducing the test flame. The flame’s size should be adjusted to 3 to 4 mm. Do not stir the oil during the application of the fl A blue halo around the test flame indicates that the flash point is heating. The temperature recorded on the thermometer when a distinct flash appears for the first time inside the cup is to be taken as the flash point of the oil. Oils containing minute quantities of volatile organic substances are liable to flash below the true flash point of the oil. Although a small slash may be observed in such cases, it should not be confused with the true flash, since its intensity does not increase with increased temperature as occurs when the true flash point reached. The minimum closed-cup flash point required for turbine oil is 165 oC and that for insulating oils is 145 oC.

The flash point /fire point of the oils = ----o C. This is also calculated by multiplying the Heat of combustion Kj Mol -1 [Heat of combustion Kj gm -1 x mol. Wt.] by vapour pressure [in bar] at 300 K (27 oC).

FIRE POINT : The lowest temperature to which an oil should be heated to generate enough vapour and to give sustained fire is called Fire Point. The fire point is higher than the flash point. So continue the procedure until the fire point Sustained.

POUR POINT The pour point is the lowest temperature at which the oil ceases to flow when cooled under standard condition.

Procedure: Take the lubricating oil in a standard glass tube enclosed in an air jacket, cooled in a freezing mixture. Take the glass tube out periodically examines and replace inside immediately. Take the temperature at which a haze appears in the oil as the cloud point. Cool the oil further, stir and test for its flow away by tilting the tube carefully for every 2 to 3 oC rise in temperature. Note the temperature at which the oil eases to flow is pour point.CALORIFIC VALUE It is defined as number of parts of water which will heated through 1 oC by the heat evolved by the complete combustion of one unit weight of fuel.

Determination of Calorific value: Calorific value of a solid or liquid fuel can be known by burning a definite quantity in a bomb calorimeter.

Bomb Calorimeter Principle : When certain weighed quantity of a fuel is burnt in the calorimeter, the heat given out is used up in heating the calorimeter and the water in the calorimeter. If we equate the heat given out by the fuel with the heat taken up by the calorimeter and water, the calorific value can be determined.

Working Procedure of Calorimeter 1. Switch on the Leco Instrument for stabilization. 2. Switch on the Electronic balance and the printer. 3. Weigh about 0.06 gm of oil sample with the oil cup provided. 4. Operate the No. 1 key to charge the instrument. 5. Enter the oil weight into the microprocessor by operating the enter switch in the balance. 6. Put the weighed oil cup into the ring provided in lid of the bomb calorimeter and connect the two rods in the lid with 8 cm long fuse wire above the oil cup. 7. Pour a known quantity of water in the bomb calorimeter and screw the lid with oil cup

8. Charge the bomb calorimeter with oxygen by the charging point through the micro- processor which shows the display in the screen ‘To fill’ and after the filling is (460 atmosphere) completed the charging will be stopped itself. 9. Collect 2 ltr of water in the bucket and put it in the place provided in the instrument.10. Place the bomb calorimeter in the bucket, check for any leak and connect the two terminals on the top of calorimeter and close the instrument with the door.11. Press start button and give the ‘yes’ command in the key board.12. After 5 minutes of firing the bucket temperature will be displaced (25 - 27 oC) in the screen. After the completion of firing the above display will disappear and Delta-T will appear. This process will go for further 3 minutes. After 3 minute of the process the actual Calorific value will be appeared on the screen.(Cal /gm).

LUBRICATING OIL

Before the advent of petroleum, lubricating oil consists of animal and vegetable oils, but modern requirements have made petroleum the main source of supply. Fatty oils are still used to a minor extent, generally in secondary role.

Lubricating oils manufactured from petroleum are known as mineral lubricating oils and are derived from crude oil by a series of refining processes that select those constituents suitable for use as lubricants. Crude oil as drawn from the wells, is a complex mixture of different types of hydrocarbon liquids boiling at different temperatures and having different properties. Although practically all crude oils contain fractions with viscosities with the lubricating oil range but not all hydrocarbons possess the other properties required for good lubrication. Therefore, for the manufacture of lubricating oils, crude oil

i. Should contain a reasonable proportion of liquid fractions of suitable viscosity and

ii. these fractions, after refining treatment, should posses the other properties desirable in lubricants.

In India lubricating oils are manufactured from imported crudes. Indigenous crudes are not suitable for the manufacture of lubricating oils. Only second quality lubricating oils are manufactured from Digboi crude oil.

The uses of lubricating oils are varied and since it would be impracticable to make all the various grades required direct from the crude oil, a limited number of primary grades i.e (base oils) is made in the refinery. These base oils are then blended together in various proportions, with or without additives to produce large grades suitable for specific applications. This secondary blending is not regarded as pert of refining and is usually arrived out in a separate lubricating oil blending plant which may be either situated within the precincts of the refinery r in an installation i.e a distributing center, drawing supplies of base oils from one or more refineries.

Based on multiplicity of individual end-use application, industrial lubricating oils may be broadly categorised as under.

1. Spindle Oils 13. Spray Oils2. Machinery Oils 14. Process Oils3. Air compressor Oils 15. Cable Oils4. Refrigeration Oils 16. Heat treatment Oils.5. Gear Oils6. Turbine Oils 7. Hydraulic oils8. Steam cylinder Oils9. Axe Oils10. Transformer Oils 11. Heat transformer Oils12. Cutting Oils

From the above different categories of lubricating oils, it is obvious that the properties of different lubricants, required for various applications, have to be different. The selection of industrial lubricants in any mechanized industry involves a consideration of the requirements of the equipments, available methods for handling and application of the lubricant itself and environment condition.

Most manufacturers of equipment and lubricants have carried out considerable test work in order to choose the proper lubricant for a particular application. It is always advisable to use lubricants as recommended by the manufacturers of the equipment or by the oil companies in order to ensure maximum life of the operating equipment.

However in selecting a lubricant for a given application, it is necessary t consider what properties are required in relation to the conditions of service. In this context, we shall now discuss the main properties listed below of lubricating oils:

1. Varicosity2. Viscosity Index3. Pour Point4. Oxidation stability5. Rust Prevention6. Resistance to emulsification (Demulsification Value) 7. Resistance to foaming8. Antiwear property9. Oiliness and film strength10. Trackiness.

1.VISCOSITY:

Viscosity of ‘flow ability’ at definite temperature. It is the most important property of an oil as at operating temperature it is viscosity that determines fluid friction (Friction within the oil itself). Any change in viscosity indicates contamination or oxidation instability. Conventional instruments like Redwood, Saybolt and Engler can measure viscosity. Absolute viscosity can be measured in entipoise.

Absolute viscosity is defined as the tangential force on unit area of either one of two parallel planes at unit distance apart when the space is filled with liquid and one of the planes moves relative to the other with unit velocity in its own plane. The cgs (Centi-metre-gram-second) unit of absolute viscosity is the poise (P). The centipoises are 1/100 of poise and is the unit f absolute viscosity most commonly used. It is more convenient to us Kinematic viscosity which is given by equation

If A is the common area between layers, V1,V2 their respective velocities and x distance between them, then the viscous

F A

V1 – V2 1 x

F = n A (V1 – V2) = n m2 x m x 1 X sec m

Dynamic Viscosity = Kg

(m) (sec)

Density = Kg / m3

Kinematic Viscosity = Dynamic Viscosity Density

The unit of Kinematic viscosity is stoke or centistokes (1/100 of stoke)

In practice the kinematic viscosity is determined by measuring the time required fr given volume f oil t flow through a capillary rube under the force of gravity. For example Typical Result 225 x 0.1200 = 27 cst, where 225 is seconds = Flow Time and 0.1200/sec = Viscometer constant.

A series of viscosity levels for Industrial Oils has been established by International Organization for Standardization (ISO), which is a federation of International Standards Institute for specified ISO viscosity grade classification. The advantage of this standardization of ISO viscosity grade classification is that lubricants suppliers, lubricant users and equipment designers have a uniform and common basis for designating or selecting Industrial liquid lubricant according to the kinematic viscosity required in a particular application.

The oil industries in India have switched over to ISO-VG viscosity classification in respect of Industrial lubricants w.e.f. 1.10.81. In the ISO system the kinematic viscosity of an oil is given at 40 0C with + 10% variation.

VISCOSITY INDEX:

The other most important property in selecting an oil for particular application is its viscosity Index. The viscosity index of oil shows the variation in viscosity with temperature.

The viscosity temperature relationship in oils is designated by the viscosity index (VI) scale. A typical Pennsylvania oil showing a small change in viscosity with changes in temperature was given in VI of 100 and a Gulf Coast oil showing a great change was given VI 0, ASTM-D567 provides a procedure for rating VI of an oil from its viscosity at 100 F and 210 F. Variation of viscosity with temperature may be determined with considerable accuracy when the viscosities are known at any two temperatures.

POUR POINT:

Lubricating oils containing straight-chain paraffin hydrocarbons tend to form waxy crystals at moderately low temperatures. Such Wax crystals formed in lubricating oils at winter temperature assume a lattice like structure which traps the liquid il and keeps it from pouring of flowing. The temperature which this ‘thickening’ takes place is the Pour Point

This is an important property t o be considered if th oil is to be used in gear cases, air compressors, bearing etc under winter-temperature conditions or in refrigerating system. This characteristic can be improved by adding additives i.e. Pour Point depressants.

OXIDATION STABILITY:

Air is inevitably present in the lubricant system. Therefore, lubricating oil oxidize in service. The extent of oxidation depends n various factors such as temperature, presence of catalysts, extent of exposure to air. Not only I oxidation more rapid at higher temperature but the chemical reactions involved may differ from those at lower temperature. Catalysts, particularly iron and copper, will also influence the nature of the reaction as well as accelerate oxidation. Exposure to air may vary from the small specific surface area of oil in bulk or in thick films to the very high specific surface area of oil mists.

Oxidation produces acids, sludge, lacquers, which affect the performance efficiency. This property is very important to be considered if oil is to be used in turbines, transformers, hydraulic system, circulatory system, centralized lubrication system etc. This characteristics can also be enhanced considerably by the addition of additives i.e. anti-oxidants.

RESISTANCE TO FOAMING:

When lubricating oils are churned or agitated in the presence of air, tiny air bubbles form. Unless these bubbles are rapidly released or broken up, a more or less persistent foam of oil and air results. Foaming may present a serious problem under certain conditions. For example, if so much foams in an oil-distribution system, that the pump delivers a mixture of oil and air to the bearings, insufficient lubrication may result and eventually lead to baring or surface failure. Foam

may cause the overflow or a oil reserve of false readings of its oil content. Foam in hydraulic lines makes hydraulic oil springy or compressible, causing improper or erratic operation of the device. High-speed gearboxes using heavy oils generate excessive foam.

These characteristics can be improved by adding additives Antifoam additives.

ANTIWEAR PROPERTY:

So long as hydrodynamic lubrication is maintained, mechanical wear cannot be occur, but in actual there are occasions when loads become high enough to squeeze out the lubricant, though for only short periods and intermittently, and metal-to-metal contact occurs between moving parts. Under these conditions, the metal surfaces will scuff, i.e. become scratched and roughened, to an extent on the severity of the conditions (ultimately if nothing were done to prevent it, they would weld or size.

Even under Hydrodynamic conditions, without metal-to-metal contact, wear can occur due to the corrosive action of water or more practically aqueous solutions of strong acids. This specially happens in Internal combustion engines. Anti corrosive additives and anti scuffing additives are used to overcome this problem.

OLINESS AND FILM STRENGTH:

The ‘oiliness’ of a lubricant is still the most fugitive and difficult quality of the lubricant to evaluate yet its performance be overlooked. Oiliness sometimes referred to as lubricity and defined as smoothness or slipperiness, decreases friction. Oiliness depends on both the lubricant and the surface to which the lubricant is applied. Compounding with fatty acids enhances oiliness of a lubricant.

TACKINESS:

In certain industrial application, oil must not drip or spatter from the bearing. For this purpose, the oil must have greater cohesion than its viscosity would indicate and must be stringly in texture. General purpose oils containing a tackiness agent provide economical and effective general lubrication ornery where oil leakage and work spoilage problems i.e. food processing, textiles, old printing and binding machines, packing machines etc. In general reduced ol loss from bearing prolongs lubrication intervals. Gear box leakage can often be stopped with an oil formulated with a tackiness additive.

Suitable test methods designed by standard International bodies like Institute of Petroleum, London (IP), American Society for testing of Materials (ASTM), Indian Standard Institute, Delhi are available to evaluate various lubricating oils for the characteristics or properties mentioned above. These test methods are used both for control purpose during manufacture as well as for performance evaluation of lubricating oils.

You may be wondering that the characteristics like odour, density and flash point have not been mentioned. These characteristics have no effect as far as the performance of lubricating oils.

CONCLUSION:

The function of lubricating oil is not only to lubricate moving parts in order to reduce friction but it has to perform many other functions. A property selected lubricating oil for a particular application will reduce the breakdown period and maximize the life of the machinery.

STANDARD SPECIFICATION AS PER IS:1012-1958 FOR TURBINE LUBRICATING OIL

Characteristics RequirementLight LDO Medium LDO Heavy LDO Extra Heavy

Viscosity 4.7 to 5.4 5.5 to 6.4 6.5 to 8.1 8.2 to 10.5Viscosity index 8.0 8.0 8.0 8.0Flash Point 165 0C Mini. 165 0C Mini. 165 0C Mini. 165 0C Mini.Pour point - 3 oC - 3 oC - 3 oC - 3 oCTotal acidity 0.20 0.20 0.20 0.20