Regulations and care
Heavy fuels
A4.05.07.02
M20-M601C
en / 15.12.1997 BA000170 3/5
Ĺ
The so-called CCAI is a useful indicator when assessing the ignition behaviour. (CCI = calculated Car-
bon aromaticity index).
The CCAI is determined from density D (kg/m
3
t 15 degrees C) and viscosity V (mm
2
/s or cSt at
50 degrees C) according to the following equation:
CCAI = D – 141 log log (V + 0,85) – 81
In principle, the following applies: the higher the CCI, the poorer the expected ignition behaviour.
Furthermore, the following applies: When taking a specific CCAI value as a basis, there is more risk
of a poorer ignition behaviour if the viscosity is low.
Since the CCAI is no measurement for the ignition behaviour, but rather an assessment aid, abso-
lute limit values cannot be specified.
The Caterpillar / MaK assessments make allowances for these factors:
A lower as well as an upper CCAI limit curve is defined depending on the viscosity, the type of
engine and the condition of the fittings and included in A4.05.07.03.00 an A4.05.07.03.01. The three
sub-ranges which develop in this manner mean the following:
The diagrams permit the determination of the permissible and/or maximum acceptable density of a
fuel in a simple manner, depending on its viscosity.
100 °C is to be the reference temperature for indicating the viscosity of a heavy fuel. A4.05.07.05
shows the conversion to 50 °C, 80 °C and Redw. I sec.
The heavy fuel grades permitted for Caterpillar / MaK engines can be found in the table “Permissible
limits for heavy fuels to be burnt in Caterpillar / MaK engines” (A4.05.07.04).
In so doing, you should ensure that restrictions with regard to the permissible densities are possi-
ble, according to the valid CCAI limit curves (A4.05.07.03.00 or A4.05.07.03.01).
Unrestricted permissible range.
Impairments by insufficient ignition characteri-
stics are not expected.
Ignition characteristics are predominantly
acceptable. Problematic fuels can, however, not
be excluded.
Range which should be avoided.
Impairments and even damage to the engine
can be expected.
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