Coal,Oil Sampling and Their Analysis

8/13/2019 Coal,Oil Sampling and Their Analysis

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Coal,oil sampling and their

analysis.



• For the determination of the various sizes of coal, as wellas for the reduction purposes, sieves conforming to IS :460-1962 shall be used.

• for sampling of coal from (a) conveyers, (b) wagons, (c)ships, (d) stock.piles and (e) seams.



TERMINOLOGY

• Coal, Large - Goal with nominal size 15 to 5 cm, the

upper limit not exceeding 23 cm.• Coal, Run-of-Mine - Unscreened coal containing all sizes,

mainly 23 to 0 cm.• Coal, Small - Coal with nominal size 5 to 0 cm.

• Increment - The quantity of coal taken by a singleoperation of the sampling implement.

• Laboratory Sample - The quantity of coal obtained byreducing a gross sample ( JCC 2.5 ) by following a

specified procedure for laboratory testing.• Lot - The quantity of coal offered for disposal at one time



Coal• Why Coal Sampling ?• Prices as per the gradation of coal So need of

continuous monitoring of coal quality.• Wide Variation in Coal qualities even from single

source.• Sample mechanically and manually.• At a time amount of coal collected is called

increment• More the number of increments from different

Places more will be the accuracy .



• Moisture Sample - A sample ‗to be usedexclusively for the purpose of determining totalmoisture.

• Sample‘ Reduction -The process of crushing orgrinding the sample to reduce the particle size

and of mixing and sample-dividing in successivestages.• Sub-lot - The quantity of coal in each of the

groups into which ,a lot is divided for the purposeof sampling; a lot may consist of two or moresub-lots.



Division of coal



Sampling• division of a lot into a number of sub-lots depending

upon the weight of the lot and then drawing arepresentative gross sample from each, of the sub-lots separately.

• The gross samples after suitable, reduction are to

be tested individually• Coal may be sampled when it is in motion, that is,

from conveyers or during loading or unloading.• IS : 437- 1956 Size grading of coal and coke for

marketing ( revised ) • IS : 1350-1959 Methods of test for coal and coke –

proximate analysis, total sulphur as calorific value



• IS : 1352-1959 Methods of test for coal

and coke -special impurities• IS : 1353-1959 Methods of test for coal

carbonization – caking index, swelling

properties and gray-king assay ( L.T. )coke types• IS : 1354-1959 Methods of test for coke -

special tests• IS : 1355-1959 Methods of test for ash of

coal and coke



SAMPLING PROM CONVEYERS

• Sub Lots -For the purpose of sampling, a lot, while it isbeing discharged over conveyer, shall be divided into anumber of sub-lots of approximately equal weight asspecified in Table



• A representative gross sample shall be drawn from eachof the sub-lots and shall be kept separately. Thus, there

will be as many gross samples as the number of sub-lots into which the lot has been divided‘ .• This number shall be evenly distributed over the sub-lot.

The increments shall be drawn with the help of asuitable shovel at regular intervals.

• The material collected from all the increments in a sub-lot shall be mixed together and shall constitute a grosssample.





Sampling Procedure• ISI or mutually agreed agreement .• For Each consignment of 250 Tons or more ,

one sample is recommended.• Collect 350kg samples for 250 tons of coal

received in increments of 7kg.C & Q C & Q350kg → 50kg of 1/8‖ → 2 kg (1/2‖)

1kg for gross moisture content (size ½‖) other

half crushed to 72 mesh size.• For efficiency of plant , Samples of coal of

individual boilers collected from hoppers.



SAMPLING FROM WAGONS DURING LOADING OR

UNLOADING

• Sub-lots - For the purpose of sampling, all the wagons ina lot shall be divided into a suitable number of sub-lots ofapproximately equal weight.

• The objective of dividing a lot into a number of sub-lots isonly to facilitate the drawing of a representative gross

sample rather than to indicate its physical division.• In order to get a representative gross sample, coal shall

be sampled as far as possible in steady motion duringloading or unloading of the wagons.

• A minimum of 25 percent of the wagons shall be selectedat random from the sub-lot.

• The material collected from the selected wagons in asub-lot shall constitute a gross sample.



• Samples of pulverized fuel to determine thefineness of coal pulverised to know millefficiency & to ascertain the burner performance.

• Analysis of coal Samples -• Proximate Analysis• Ultimate• GCV• Hardgrove grindability index ( HGI index)• Fusion behaviour of ash of coal.



Ash Fusion Sample

• reduce the gross sample in successive stagesand take an additional 1 kg sample, passing12.5 mm IS Sieve for the determination of ashfusion.

• If, however, it is desired still further to avoid anycon-tamination whatsoever with iron, takeseparate‘ quantities of about 5 kg of the coarselybroken coal ( 12.5 mm and below) for the test.

Do not grind the sample further in iron &ills orvessels. Grind the ash obtained by incinerationin an agate mortar to pass 75 micron IS Sieve.





Moisture• Total Moisture- The coal which has been exposed to

contact with water in the seam or in a washery, or coaland coke wetted by rain, may carry free or visiblewater. This water plus the moisture within the material,is referred to as total moisture.

• Moisture in coal equilibrated at 60 percent relative

humidity and 40°C — The moisture content of air-driedcoal varies and depends upon the temperature andrelative humidity of the air to which it is exposed. Assuch it is necessary to determine moisture content ofdifferent samples of coal under standard conditions.For this purpose, the coal is ground to pass 212-micronIS sieve and equilibrated in an atmosphere of 60percent relative humidity and 40°C.



Moisture in coal equilibrated at 96 percent relativehumidity and 40 0C

• Moisture in coal equilibrated at 96 percent relativehumidity and 40°C — This is also termed as ‗Near Saturation Moisture‘ or ‗Bed Moisture‘ . It is exclusive offree or visible water and is determined after equilibrating

coal in an atmosphere of 96 percent relative humidityand 40°C. This is a measure of the moisture holdingcapacity of a coal.

• Free water or visible water is that quantity of water whichis physically adhering to coal. In essence,this is thatquantity of water which is in excess of the moistureholding capacity of a coal.



REDUCTION OF GROSS SAMPLES

• GENERAL PREGAUTIONS

The place set apart for the treatment of grosssamples shall prefer-ably be enclosed, roofedover, cool and free from draughts. Where this isnot possible, precautions shall be taken against(a) loss of fine wind-borne sample, (b)contamination with moisture, and (c)contamination with foreign matter.

• Select a hard and clean surface free of cracksfor sample mixing,quartering and other

operations. Do not let cinders, sand, chippingsfrom the floor or any other foreign matter get intothe sample.



CONING AND QUARTERING

• The material which has been crushed to. 3.35 mm shall

be heaped into the shape of a cone by pouring onescoopful of the material after another at the apex of thecone till the entire sample has been coned.

The material shall be allowed to slide down the sides of

the cone only under the influence of gravity.• Flatten the cone evenly so that it forms a low circular pile.

Cut the pile into four quarters along two diameters whichintersect at right angles.

• Retain one pair of opposite quarters and reject the other.Repeat till the size of the retained sample is reduced tothe required weight of 2 kg.



RIFFLING

• The material which has been crushed to3.35 mm shall be dropped uniformly in the

_ riffle. One half shall be retained and the

other half rejected. This procedure shall berepeated several times till 2 kg of materialis obtained.



GRINDING (FINE SIZE)

• In grinding the sample to pass 212-micron ISSieve , it has been found that unnecessarily finegrincling is harmful. The ground coal shouldhave the following approximate particle size

distribution:• Passing 212-micron IS Sieve and retained on

125-micron IS Sieve : 35 percent• Passing 125-micron IS Sieve and retained on

63-micron IS Sieve : 30 to 35 percent• Passing 63-micron IS Sieve : Remainder





Moisture• Moisture - Inherent & external moisture.• When a wet coal is exposed to atmosphere the external

moisture evaporates.• The inherent or Air dried moisture is related to the nature

of coal . The I.M. content predicts the maturity of coal.

• 1g. sample for 1&1/2 hrs - at 108 oC± 2 oC.• Ash & Mineral Matter – Inorganic minerals converted into

ash by chemical reactions.• Mineral matter -inherent and extraneous.

• Extraneous can be removed from coal by mechanicalmethod i.e. Washing . Inherent cannot be separated bymechanical means.



Ash & VM• High Ash – removing and Handling problems.• Ash may restrict passage of air & lower the rate of

combustion . So need of ash calculation to know thequality of coal .

• ―parr‖ formula -

• Mineral matter = 1.1 A ( A=% of ash in coal)• V.M• The flame size depends on V.M. content.• Coals of V.low V.M. having good C.V are

disadvantages.• V.M is volatile substance present in coal and thegaseous products of thermal decomposition of coal .



VM• VM is measured at 900+/-20 0C for 7 minutes• VM first catches fire, burns with flame and gives support

in burning the char (FC)• Normally V.M is 20-30%• For low V.M coal oil support is given. Flame length

increase with decrease in V.M. as char takes longer timefor combustion.• V.M also dictates the fineness required for proper

combustion . Lower the V.M in coal, higher is thefineness required.

• For V.M 20-30% ,68-70% should pass through 200• If V.M <20% , 80% pass is required.• Fixed carbon = 100-(Ash%+V.M%+Moist%)



Ultimate Analysis• Ultimate Analysis- To know the percentage of C,H,N,S,O

coal is burnt in O2• Carbon and H2 are oxidised to CO 2 and H 2O.• From the weight of CO2 &H2O, corresponding quantity of

C&H present in sample can be calculated .• S & N content by analytical methods. O2 content by

difference.• Carbon & H2 content of coal from proximate analysis -• C=0.97 F +0.70 (V-0.1A)-0.6 M• H=0.036F +0.091 (V-0.1A)-0.05M• F=fixed carbon

• V=Volatile matter• A=Ash• M= Moisture on Air dried



Carbon & H2 content of coal

• Proximate Analysis By Ultimate Analysis By formula

M A V.M. FC C H C H

0.9 23.8 18.3 57 65.03 3.64 65.89 3.46

1.0 25.5 14.3 59.2 64.14 3.13 65.05 3.15

1.2 13.8 18.1 66.9 75.98 4.09 75.88 3.87

0.9 32.8 12.5 53.8 58.14 2.96 58.10 2.73



• Ultimate analysis predicts whether coal is weathered(oxidised) or not.

• A weathered coal will be deficient in C&H but richer withO2 resulting in low calorific value. Proximate analysismay not show any wide difference between a normalcoal & weathered coal.

• By ultimate analysis we can calculate the theoretical airfor combustion.

• We can calculate gross & net C.V.• Gives an idea of SOx and NOx.• Dew point of the flue gas increases with increase in SO3

that means more sensitive heat loss. SO2/NO2/Cl2 etc.improve the performance of ESP by lowing Ashresistivity .



Calorific value• Calorific value - Quantity of heat evolved by its complete

combustion. Calorific value is employed to find.• Thermal efficiency of Combustor.• Coal equivalent of any fuel for operation & commercial

purposes.• Useful heat value of coal, which has been accepted as

an index of price fixation.• 1g coal fired electrically at a P of 25 kg/cm2 O2• GCV can be calculated theoretically.• For low moisture coal – • 1.8 GCV =165*FC +136*(V-1.1A)-108*M Kcal/kg• For high Moisture coal — • 1.8* GCV=154*(100-1.1A-M)-108*M kcal/kg



Proximate Analysis

Proximate Analysis Det_CV Cal_CV

Moisture Ash

5.95.75.4

24.736.619.4

519542155380

537042215473



Useful Heat Value( UHV)

• An arbitary formula to calculate useful heatvalue -

• Useful heat value (UHV)=8900-138 (A+M)kcal/kg

• A,M are Ash & moisture % at 60/40• If V.M<19• UHV=8900-138(A+M)-150(19-VM)Kcal/kg



Grades of coal

• Grade UHV(kcal/kg)• A >6200• B 5600-6200

• C 4940-5600• D 4200-4940• E 3360-4200

• F 2400-3360• G 1300-2400



HGI- Hardgrove Grindability Index• HGI- Hardgrove Grindability Index (HGI)• HGI of Coal indicates its easiness towards pulverisation.

It is also related to the power consumption forpulverisation of coal. The life and efficiency of coal milldepends on the HGI of coal.

• It measures the increase of surface produced by theapplication of standard amount of work and express theresult as HGI, Which is between 20-100 for most coals.

HGI=13+6.93 W

• W= g of coal passing through 200 mesh after 50g ofcoal of size 16-30 mesh are ground in a standard mill for60 revolution.





Ash Fusion- Clinker formation• Ash Fusion - Fusion behaviour is due to mineral matter

associated with coal.• Depending upon the temp. of thermal environment theatmosphere (reducing or oxidising ) the time of heating &the composition of mineral matters of coal. final productmay be Ash, partially fused mass / clinker or molten

matter/ Slag.• Leitz heating microscope - specimen in cylindrical shapeii reducing atmosphere.

• Initial deformation temp.• Hemispherical temp.

• Flow temp.• The major components of Ash are SiO2,Al2O3 & CaO• Minor components – MgO, TiO2,P2O5,Na2O



OilMechanical machines need lubrication.

• No machines can run for long without lubrication of its movingparts. At best, the moving parts may wear out faster. At worst,entire machines can seize up and develop cracks. In severeconditions, the heat built up can even cause explosions andloss of lives.

• Lubricating oil can last for a very long time in normal machineoperation.

• The key features of steam turbine oil are superior oxidationresistance, rust/corrosion protection and good water sheddingproperties. Because steam turbine oils routinely carry out theirfunction in a 'wet' environment, it is vital that steam turbine oiladditives have very good hydraulic stability (i.e. are notdegraded by the presence of water).



O i Ch k



Onsite Checks• Color - Unusual and rapid darkening can indicate

contamination or excessive degradation.

• Odor - Sour smelling oil can indicate contamination orexcessive degradation.• Air entrainment - Air bubbles in the body of the lube oil

sample should clear within 15 minutes.• Foam - After a vigorous shake, foam from the surface

should clear within 10 minutes.• Water - Turbine oil samples should be transparent. If you

cannot read printing through a clear sample container,then water levels above 300 ppm may be present. A

simple crackle test can also prove useful in determining ifany free or emulsified water is present.• Solids - Look for solids settling out as signs of external

and internal contamination.



Air Release ASTM D3427

• Turbine and system circulating oils, if exposed to heating,will absorb air and change their characteristics. They shouldon cooling release this air quickly and return to the originalproperties. The time for the air entrained during the testprocedure to detrain to 0.2 percent by volume.

• This is typically not a problem for most ISO VG 32 turbineoils, but can be for ISO VG 46 oils, due to the higherviscosity.

• In turbines with small sumps and minimal residence time,entrained air mixtures can go to bearings and criticalhydraulic control systems causing film strength failureproblems, loss of system control, and an increased rate of

oxidation.• Air release of turbine oils should not vary with in-servicetime and therefore may not need to be tested for conditionassessments routinely, unless a specific problem issuspected.



Air release..• The air release test is done by saturating the fluid (normally

at 50° C., or any other temperature such as 25° C.) with airbubbles and then measuring the time it takes for the fluid toreturn to an air content of 0.2%. Air release times aregenerally longer for Group I base oils than for Group III baseoils. Polyol ester, polyalphaolefin, and phosphate ester baseoils typically have lower air release than conventionalmineral oils.

• The maximum air release for hydraulic oils 5 minutes forISO 32 oils, 7 minutes for ISO 46 oils, 17 minutes for ISO150 oils. Air release values generally increase with viscosityof the base oil.Air release is mainly a function of the basestock, and oils need to be monitored for this



Demulsibility ASTM D1401

• This test measures the ability of oils to separate from a water/oilemulsion.

• Oil and water under certain conditions will form an emulsion, whichcan have undesirable consequences. If it is allowed to stand, withno further mixing, the oil and water should separate, to enable thewater to be removed.

• Demulsibility is affected by excessive water contamination orpresence of polar contaminants and impurities.

• Demulsibility can be tested using ASTM D1401, in which a knownvolume of oil is mixed with water, and the time taken for the two toseparate is measured in minutes; the faster the separation, thebetter the demulsibility.

• ASTM does not have warning limits for demulsibility although someturbine OEMs identify levels of 3 ml emulsion after 30 minutes on

new oils. In-service oil warning limits of 15 ml or greater of emulsionafter 30 minutes should serve as a warning limit.



Dem… • The impact of demulsibility depends on the

system residence time and anticipated levels ofwater contamination.• Demulsibility testing can show failure in the lab,

but with sufficient residence time, the turbine oil

may shed water at an acceptable rate that doesnot impact turbine oil performance.• Small sumps with lower residence times will

require better demulsibility performance thanlarger sumps.

• Testing for demulsibility should be conducted onan annual basis, or if the lube oil system isexposed to water.



Test Method• A 40-ml sample of oil and 40 ml of distilled water are put into

a 100-ml graduate cylinder. The mixture is stirred for 5minutes while maintained at a temperature of 130° F. Thetime required for separation of the emulsion into its oil andwater components is recorded. If, at the end of 30 minutes, 3or more milliliters of emulsion still remain, the test isdiscontinued and the milliliters of oil, water, and emulsion are

reported. The 3 measurements are presented in that orderand are separated by hyphens. Test time, in minutes, isshown in parenthesis. The number of minutes to 3 mlemulsion at 54 degrees C. by ASTM D 1401-02 is preferablyless than 30 minutes, more preferably less than <20 minutes.



flash point & fire point• The flash point is the temperature to which

an oil has to be heated until sufficientflammable vapor is driven off so that it willflash when brought into contact with a

flame.• The fire point is the higher temperature at

which the oil vapor will continue to burn

when ignited.



Flash point• Flash point testing is done

primarily to confirm productintegrity from contamination.

• ASTM D4378-97 identifies a

drop in 30°F (17°C) from thenew oil flashpoint as a warninglimit.

• Flash point testing is requiredonly if product contaminationfrom a different oil or solvent issuspected.

http://media.noria.com/sites/archive_images/backup_200203_TurbOils-Fig4.jpg



Viscosity• Viscosity is the most important characteristic of a turbine oil

because the oil film thickness is critically dependent on the

oil‘s viscosity. Turbine blade clearances are critical to powerplant efficiency and reliability. These blade clearances aredirectly impacted by lubricant viscosity. Changes in oilviscosity can result in unwanted rotor positioning, both axiallyand radially. Axial movements directly impact turbine bladeefficiency and in extreme cases can lead to blade damage.

Radial movements caused by changes in viscosity can resultin oil whip, where the rotor does not settle into one radialposition.

• For in-service turbine oils, the viscosity should remainconsistent over years of service, unless the oil has becomecontaminated or severely oxidized. ASTM D4378-97 identifiesa five percent change from the initial viscosity as a warninglimit.

• Testing for viscosity should be conducted on a quarterlybasis, at a minimum.



Viscocity Index

• The Viscosity Index (VI) is an indication of theoil‘s change in viscosity with a change intemperature. Most gas and steam turbine OEMsrequire a turbine oil with a VI of at least 90.

• The VI for turbine oils should not vary in-service,because turbine oils typically do not contain VIimprovers and therefore do not need to be testedroutinely.

• The higher the VI, the less a given lubricant‘s

viscosity will change with a subsequent change intemperature.



PPM & % relationship

• 10000 ppm = 1 %• 1000 ppm = 0.1 %• 100 ppm = 0.01 %

• 10 ppm = 0.001 %1 ppm = 0.0001 %

Water in the oil increases frictional resistance,causes the oil to break down prematurely,corrodes journals and any parts not continuouslycovered with oil, and may cause corrosion in theentire system.





Rotating Pressure Vessel Oxidation



Rotating Pressure Vessel OxidationTest (RPVOT) - ASTM D2272

• was developed for the monitoring of in-service oils to warn of a lossin oxidation resistance. Oxidation is driven by heat and exposure to

contaminants like water, entrained air and catalytic metals. As aturbine oil degrades, it forms weak organic acids and insolubleoxidation products.

• After a period of time, these oxidation by-products and carboninsolubles cause a significant change in critical clearances, and insome instances prevent the oil from providing adequate cooling tothe bearings and fouling turbine control elements and heatexchangers.

• for identifying oxidation stability problems with in-service turbine oils. ASTM D4378-97 identifies an RPVOT drop to 25 percent of the newoil RPVOT value with a concurrent increase in Acid Number (AN) asa warning limit.

• the RPVOT test is designed to determine a lubricant‘s suitability forcontinued use, not to compare competitive oils. Competitive oilcomparisons should be evaluated on the basis of RPVOT longevity,rather then the absolute RPVOT value.





RPVOT• an oil that has reached its minimum allowable RPVOT values

needs to be changed. However, as a short-term measure, theso-called ―bleed and feed‖ method of turbine oil rejuvenationis suitable to extend the life of the turbine oil for a limited time.

• Efforts to readditize a severely oxidized turbine oil withoxidation inhibitor can put equipment at risk. An oil that has aRPVOT value below 100 minutes more than likely has

diminished its inherent base stock oxidation stability, makingreadditizing a nonpractical solution.• In such cases, readditization may temporarily boost the

RPVOT value but given the diminished nature of the basestock may sharply reduce the time frame before heavyvarnishes and sludges are formed. Without the use of specialfilters such as Fuller‘s Earth, to strip all polar materials,contaminants and additives, followed by completereadditization, the rejuvenation of a degraded turbine oil isinadvisable.



Foaming characteristics - ASTM D4378-97 • Large industrial turbines have a need to control foaming to ensure

adequate lubrication and to protect the environment from spillages.• Circulation oils usually have an additive to keep foaming under

control. To determine if the additive is still functioning fully, ameasured amount of air is blown at a constant rate into an oil at aspecified temperature, the foam produced is measured and checkedto see how long it takes to collapse.

• the volume of foam generated after blowing for 5 minutes at 75°F(24°C), defined as the residual foam left after a 10-minute settlingperiod. A foam stability of less than 5 ml is a good indication thatfoam bubbles are breaking and the turbine should not experiencefoam operational problems.

• When addressing a foam problem, cleanliness, contamination ormechanical causes should be investigated before field defoamantreadditization can be considered. Excessive readditization can resultin an even greater problem with increased air entrainment. Dirt is aleading cause of foam, so cleanliness should be tested as a likelycause.



Foam ASTM D892

• If the foam level in the turbine sump is sixinches or less and does not overflow thesump or cause level-monitoring issues, thenturbine oil foaming is not usually a major

cause for concern, although a suddenincrease in foaming may indicate a moreserious problem.

• Lube oil at the turbine sump surface shouldshow at least one clear area (no bubbles)and larger breaking bubbles should be seen

at this interface.



PQ or particle quantifier• This test determines ferromagnetic debris

in used oil samples and to screen samplesfor further analysis.

• This test measures the larger ferrous wear

particles in the oil, by their effect on amagnetic field. It is more suited to particlesgreater than 10 microns. Together withICP (which is optimised for particles sized< 5 microns) this can give moreinformation on wear particle size profiles.



ISO 4406• Sudden breakdown in an oil system is often caused by

large particles (>14 micron) in the oil while slower,progressive faults, e.g. wear and tear, are caused by thesmaller particles (4-6 micron).

• That is why the particle reference sizes were set to 4micron, 6 micron and 14 micron in ISO 4406/2000.

• A typical sample contains in every 100 ml of oil:450,000 particles >4 micron

120,000 particles >6 micron14,000 particles >14 micron

• Introduced in the ISO classification table this oil samplehas a contamination class of 19/17/14.





Additives put into the lubrication oil• Anti Oxidant - Amines, Phenols

Corrosion Inhibitor Detergent and Dispersant - Ca, Ba, Compounds, Soaps

Alkalinity - Ca, Ba Hydroxides Anti Bacterial - BiocidesOiliness or Wetting Agents - fatty oils, chlorinated waxExtreme Pressure Agents - organic compounds of Cl, S,P (for hydraulic, gear oil)Pour Point Depressant - Organic polymers (alkylnaphthalene) (for steering gear, refrigerator)

Anti foam - SiliconesViscosity Index Improvers - organic polymersEmulsifying Agent - Polar Compounds (emulsifying butdo not lose lubricating property)



NAS 1638 Particle Count• The sample is pumped through a sensor, which counts

and sizes the particles. A 100ml of sample is counted andthe particles are grouped into various size ranges. Theresults are assessed against NAS 1638 to give ratingswhich determine the cleanliness of the fluid.

• Hydraulic systems are sensitive to the presence of solidparticulate matter or 'dirt'. Dirt particles interact withmoving surfaces that accelerate wear. If they are notremoved or diluted, loss of operating efficiency andeventual breakdown is more likely. Sizing and counting ofparticulate contamination in hydraulic fluids are measuredby a Particle Size Analyzer. Counts are recorded asparticles per 100 ml in the ranges 5-15, 15-25, 25-50, 50-100, 100+ microns. Limits are set by the manufacturers.



TAN -Total Acid Number• This test describes the measurement of the acidic

constituents in oils and is reported in milligrams ofpotassium hydroxide per gram of sample.• Oils degrade while in service, due to both acidic and

basic oxidation. An increase in the acid number of aused oil is a measure of the amount of acidic substancesabsorbed. It is measured by determining the Total AcidNumber (TAN) of the oil.

• The rate of change of the TAN is more important than itsabsolute value. A rapid increase may be caused by

excessive degradation due to oxidation, hotspots fromskidding bearings, carbon seals, dirty oil ways or by top-up with a different oil.



Constituents of oils• The two basic categories of lube oil found in oil

analysis applications are mineral and synthetic.Mineral oils are refined from naturally occurringpetroleum, or crude oil. Synthetic oils aremanufactured polyalphaolefins, which arehydrocarbon-based polyglycols or ester oils .

• Mineral oils are the most commonly usedbecause the supply of crude oil has rendered

them inexpensive; Another advantage ofmineral-based lube oils is that they can beproduced in a wide range of viscosities.





LOAD CARRYING ABILITY

• The ability of a lubricant to maintain aneffective lubricating film under high loadsor pressures is a measure of its loadcarrying or extreme pressure (EP)characteristics.

• The load carrying ability of a lubricant maybe enhanced by the addition of EPadditives



NEUTRALIZATION NUMBER.• As petroleum products are subjected to elevated

temperatures, the process of oxidation occurs.Oxidation leads to the formation of organic acidsin the lubricant. This increase in acidity reducesthe water-separating ability of certain oils, andmay also prove corrosive to certain alloys.

• The neutralization number measures the amountof acidity present in the lubricant. It isquantitatively defined as the amount ofpotassium hydroxide (KOH) required to

neutralize the acid present in one gram ofsample. This quantity is also referred to as theTotal Acid Number (TAN).

C O O A O O



CLOUD POINT AND POUR POINT• Since petroleum stock consists of a mixture of molecular

components, lubricants do not exhibit sharp freezing points.• As a lubricant is cooled, certain components such as waxes

will begin to precipitate out and become evident in the liquidas a cloud.

• The temperature at which this occurs is called the cloud pointof the lubricant. If the product is further cooled, a point will be

reached at which the lubricant will no longer flow or beefficiently pumped. The temperature at which this occurs istermed the pour point of the lubricant.

• Both properties are related to the wax content of the basestock. The pour points of high-wax lubricants may bedepressed by the addition of pour point depressant additives.Pour point behavior becomes important in applications suchas refrigerant compressor lubrication where the oil issubjected to low temperatures.

FLASH POINT AND FIRE POINT



FLASH POINT AND FIRE POINT

• As a lubricant is heated, lighter components

begin to vaporize.The temperature at whichsufficient vapor concentration exists above thesurface of the lubricant so that ignition with atest flame is possible is called the flash point ofthe product. Flash point is useful for bothproduct storage requirements and for thedetection of contamination of one product withanother. The fire point of a lubricant is thattemperature at which sufficient vapors arepresent above the surface of the lubricant tosustain combustion upon ignition. Thisparameter is useful for storage and safetyconsiderations.

Documents

Coal,Oil Sampling and Their Analysis