4. Carbon Residue Test

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4. Carbon Residue Test

(Experiment No. 3)

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1. OBJECTIVES:

1) To be able to determine the carbon residueof a liquid fuel.

2) To be able to know the definition of a

carbon residue test. 3) To be able to have knowledge about carbon

residue of a liquid fuel.

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2. THEORY AND

HYPOTHESIS: Carbon residue for a fossil fuel can be defined

as the tendency of that fuel to form carbon

deposits at high temperature in an inert

atmosphere.

Carbon residue for a fuel is measured in weight

percentage (wt %) or parts per million by

weight (ppm wt). High carbon residue value is

undesirable for a fuel.

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2. THEORY AND

HYPOTHESIS: (cont..) When oil is heated to a high temperature in the

absence of sufficient air a portion of the oil will

distill, thus leaving a carbon residue.

The amount of this residue is an index to theextent the oil is likely to decompose in service.

Under engine-operating conditions, the amount

and type of the carbon formed has an

important effect upon the performance of theengine.

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2. THEORY AND

HYPOTHESIS: (cont..) While no maximum residue specifications for

lubricating oils are commonly given, a relatively

smaller amount in one oil compared with

another should be favorable.

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2. THEORY AND

HYPOTHESIS: (cont..) Apparatus known as the Conradson carbon-

residue tester is widely used in this country.

It consist of a porcelain crucible with a

Skidmore iron crucible resting upon a layer ofsand in a second larger iron crucible, all of

which are supported upon a wire triangle on a

metal stand of specified dimensions.

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2. THEORY AND

HYPOTHESIS: (cont..) The assembled tester is shown in the figure.

The crucibles are surrounded by an asbestos

block and covered by a sheet-iron hood and

chimney.

Heat is applied by a Meker burner. An analytical

balance is used to weigh the sample of oil and

the residue.

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2. THEORY AND

HYPOTHESIS: (cont..)

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2. THEORY AND

HYPOTHESIS: (cont..) A clean porcelain crucible is weighed to the

nearest 5mg, then filled with a 10g sample of oil

and weighed to the same accuracy.

The crucible is then placed in a Skidmorecrucible.

The sand in the large iron crucible is leveled,

and the Skidmore crucibles are covered, and

the assembly of crucibles is centered on a wiretriangle with the asbestos insulation on a

suitable ring stand.

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2. THEORY AND

HYPOTHESIS: (cont..) The whole is covered with the sheet-iron hood,

and heat is applied with a strong flame from the

Meker burner so that the pre ignition period

will be from 8.5 to 11.5 min.

When smoke appears from the chimney, the

burner is moved or tilted so that the flame

passes up one side of the crucible and ignites

the oil vapor.

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2. THEORY AND

HYPOTHESIS: (cont..) The burner is momentarily removed and the

gas flame adjusted so that the vapors burn

uniformly with the high flame above the

chimney but not above the bridge on top of the

chimney.

The burning period should be from 12 to 14

min.

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2. THEORY AND

HYPOTHESIS: (cont..) When the burning and smoking have ceased,

the burner is adjusted so that the bottom of the

iron crucible is heated to a cherry red for

exactly 7 min.

The total period of heating should be 28 to 32

min. The burner is then removed and the

apparatus is allowed to cool for about 15 min.

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2. THEORY AND

HYPOTHESIS: (cont..) The porcelain crucible and contents are

reweighed, and the percentage of carbon

residue is calculated on the basis of the original

sample weight.

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2. THEORY AND

HYPOTHESIS: (cont..) The Conradson Test for the amount of carbon

in oil is accurate if test is properly performed.

Also through the experiment it was found out

that Carison residue is very small compared tothe amount of other components in oil.

Carbon residue test determine the percentage

of carbon that remains in a sample after the

volatile vapors had been driven off by heat.

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3. LIST OF APPARATUS:

1) Meker Bunsen Burner

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(cont..) 2) Hood Porcelain Crucible

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(cont..) 3) Tripod

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(cont..) 4) Wire Mesh

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(cont..) 5) Chimney

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4. SET UP OF

APPARATUS:

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5. PROCEDURES:

1) Place the two glass bends provided whichare about 1 in diameter in the porcelain

crucible and include their weight in the net

weight of the crucible. Then, add 10 grams of

the oil to be tested accurately weighed and free

from impurities.

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5. PROCEDURES: (cont..)

2) Place the crucible in the center of theSkidmore crucible. Level the sand in the sheet-

iron crucible and set the Skidmore crucible as it

is in the exact center of the iron crucible.

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3) Apply the covers to both the Skidmore andthe iron crucible, the one to the later fitting

loosely to allow exit of vapors that are formed.

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4) Place the bare nichrome wire triangle onthe metal tripod on the asbestos block as

hollow sheet metal box.

Center the short iron crucible into the block

with its bottom resting on top of the triangle

and cover the whole with the sheet iron hood in

order to distribute the heat during the process.

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5) Apply heat with a highly strong flame from aMeker type gas burner so that the pre ignition

period will be 10 and 1 1/2 minutes.

When some smoke appear above the chimney,

immediately move or tilt the burner so that the

gas flame plays on the sides of the crucible for

the purpose of igniting the vapors.

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Then, remove the heat temporarily and beforereplacing adjust the gas flame so that the

ignited vapors burn uniformly with the flame

above the chimney, but not above the wire

bridge.

Heat may be increased if necessary, when the

flame does not show above the chimney. The

period of burning the vapors shall be 13 and 1minutes.

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6) When the vapors cease to burn and nofurther blue smoke can be seen, readjust the

burner to hold the heat as in the beginning so

as to make the bottom, and the cover part of

the sheet-iron crucible, red and maintain for

exactly 7 minutes.

The total period of heating should be 2 to 30

minutes, which constitute an additionallimitation on the tolerances for the preignition

and burning periods.

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7) There should be no difficulty in carrying outthe test exactly or directed with the gas burner

provided, using city gas with the top of the

burner about 2 below the bottom of the

crucible. The time periods should be observed

with whatever burner or gas used.

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8) Remove the burner and allow the apparatusto cool until no smoke appears, then remove

the cover of the Skidmore crucible. Remove the

porcelain crucible with heated tongs, place in

the dessicator, cool and weigh.

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9) The total weight of the crucible plus beadsand 10 grams of oil at start minus the weight of

the crucible plus beads and carbon residue at

finish equals loss of oil on grams.

The 10 grams of oil minus loss in weight of oil

equals carbon residue in grams, divided by 10

grams equals % of carbon residue.

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%% 100oilofweight

residuecarbonofweightresiduecarbonof

crucibleofwtresiduecarbonandcrucibleofwtresidueofwt ...

%.&.

.&.% 100

crucibleofwtoilcrucibleofwt

crucibleofwtresiduecrucibleofwtresiduecarbon


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6. DATA & RESULTS:

Weight of crucible = _______________

Weight of oil = ___________________

% of carbon residue = ______________

Weight of carbon residue = __________

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7. SAMPLE COMPUTATIONS:

8. QUESTIONS :

9. ANSWERS:

10. DISCUSSION: 11. CONCLUSION/RECOMMENDATION:

12. REFERENCES:

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END

4. Carbon Residue Test

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