Page 34 - Insurance Times February 2016

minimal in each coal carrying compartment and steps ered coal and, therefore, mined coal self-heats to a
to be taken to monitor and record the rise of tempera- greater extent than weathered coal.
ture, if any, during the entire sea voyage.
When spontaneous combustion occurs, the temperature
Ventilation rises initially but no burning in the normal sense takes
place. This stage is called "heating". Apart from the
As the cargo is prone to self-heating, ventilation should be increase in temperature, heating may develop from the
restricted to an absolute minimum, and it is essential gases produced i.e.carbon monoxide. Since the gases
that the cargo is trimmed to a level which is reasonably produced tend to increase the possibility of spontaneous
possible. Any increase in temperature may cause self- heat- combustion in a remote location, it is difficult to locate
ing. More over, nature of the cargo is such that spoting the the place of heating. The heating gradually develops
hot spot is unlikely to be detected in the early stages un- into a fire unless the situation alters.
less there happens to be a temperature probe in the right
location. Marine underwriters should not grant cover for spon-
taneous combustion during storage at port even in the
Since self heating is an oxidation process,the oxygen con- ordinary course of transit. However, cover for spontane-
centration in the hold atmosphere under conditions of re- ous combustion may be granted during sea voyage and
stricted ventilation is likely to become depleted. For car- the loss, if any, due to spontaneous combustion may
goes which are liable to emit methane, the possibility of be admitted if the Master of the vessel confirms the oc-
explosion is high. Hence precautions should be taken to currence of spontaneous combustion.
avoid the accumulation of flammable atmosphere in the
holds although excessive ventilation, particularly into the Loss of Weight
body of the coal, may cause self - heating.
Coal or coke shipped in wet condition may be subject to
Contamination loss of weight due to drainage during the voyage or by
evaporation up to, say 3%, depending on the quantity
Most classes of coal, particularly those used for coke shipped. However, loading and unloading in heavy rain
making, suffer deterioration and depreciation in value due may result in an increase in discharged weight over
to contact with salt water. However, quality, calorific value shipped weight.
apart, coal is seldom affected due to contact with fresh
water. Hence, proper care should be taken while arriving Apart from the physical weighing of the commodity on
at depreciation or loss arising from spontaneous combus- loading and discharging, an approximate check of the lost
tion, heating, or water damage. The assistance of a quali- or added weight can be made by using the immersion
fied sampler/analyst is essential to determine the de- scale of the vessel or by comparison of moisture analysis
gree of deterioration. of cargo samples taken professionally during loading and
discharging. Cargo weights are, in certain cases ,ascer-
Spontaneous combustion

A commodity having relatively low ignition tempera-
ture begins to release heat. It may occur due to oxidation
by moisture and air and, in some cases, bacterial fermen-
tation generates heat. If heat is unable to escape, the
temperature of some commodities like hay, straw, peat
etc. increases.

With regard to coal , the possibility of self- heating de-
creases with increasing rank of the coal. Lignite coal is
more susceptible than bituminous coal, but the latter is
more active than anthracite coal. It is also found that
mined coal consumes oxygen more rapidly than weath-

34 The Insurance Times, February 2016

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