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DEFINITION
A refined petroleum
distillate, less volatile than gasoline, boiling between 150 0C
and 300 0C, its
distillation range overlapping that of gasoline and HSD.
SPECIFICATIONS
Superior kerosene meets Bureau
of Indian Standards specification IS : 1459-1974.
SMOKE POINT
The maximum flame height in
millimeters (mm) at which the oil burns without smoking when tested in a standard wick-fed
lamp under specified conditions is termed and smoke point.
Smoke point is important
because it determines the degree of illumination possible from a given kerosene in a
wick-fed lamp. Smoke point is related to the hydrocarbon composition of kerosene - it is
highest with paraffins, considerably lower with naphthenes and very much lower with
aromatics. The smoke point is also an indication of the tendency to smoke when the flame
is smaller than the maximum stipulated size. Smoking under such conditions is usually
caused by an inadequate supply of air or by a sudden draught.
Excise/Customs requirements
stipulate a minimum flame height of 18 mm mainly to distinguish it from HSD. The Indian
customs method for testing smoke point tends to give somewhat lower readings than the
standard IP method.
BURNING TEST : CHAR VALUE
It is important that kerosene
should burn freely and steadily for reasonable periods without attention to the appliance
and with no diminution of flame. Burning tests have been developed to assess these
properties.
The burning test is
carried out for 24 hours in a standard lamp with a flame conforming to a specified size
and shape. At the end of the test the consumption of kerosene and the amount of char
formed on the wicks are measured, while a qualitative assessment is made of the appearance
and colour of any bloom which may have been formed on the chimney. The char value is
expressed as milligrams of dry char per kilogram of kerosene consumed.
VOLATILITY
The nature of the distillation
range is of significance with regard to burning characteristics, such as warming up time
and initial flame size, etc. and it is customary to place suitable limits on volatility.
An abnormally high final Boiling Point can indicate contamination with higher boiling
constituents.
COLOUR
Colour in itself has no
bearing on burning quality, but its measurement is useful in checking consistency of
supplies and contamination.
SKO is water which when
produced and is marketed as such in India. However, in many countries premium grades are
dyed for ease of identification, the dye present in trace quantities.
SULPHUR Only slight amounts
of sulphur compounds remain in kerosene after refining which removes most of the
undesirable products. Hydrogen sulphide and mercaptans are removed so as to render the
kerosene marketable from the point of view of odour.
Free or corrosive sulphur in appreciable amount could
corrode metallic components of an appliance, e.g. pressure burner vaporizing tubes which
operate at high temperatures. The usual test applied in this connection is the Copper
Corrosion Test. The total sulphur content of kerosene should be low because oxides of
sulphur formed during combustion should not be present to harmful extent in the
atmosphere. This is particularly important in respect of indoor burning appliances which
are not provided with the flue. Also, as mentioned earlier a higher sulphur content can
contribute to the formation of lamp chimney deposits.
FLASH POINT
In the interest of safety,
legislation has been introduced in most countries fixing minimum flash point limits to
prevent the inclusion of highly inflammable volatile fractions in kerosene distillates.
According to Controller of Explosives classification it falls in the category of Class B
Petroleum Products. Its flash point (Abel) is stipulated as Min. 35 deg C in the IS
specification.
SPECIFIC GRAVITY
As with colour, specific
gravity has no relation to burning quality, but it is a useful aid for quantity reckoning
and identity.
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