Due to recent incidents involving self-heating of coal
The Gard P&I Club has issued a loss prevention ciruclar to highlight the importance of checking the accuracy of shippers declarations for all types of coal cargoes.The Club has recently been involved in several incidents of self-heating of coal cargoes and would like to emphasise the importance of treating coal cargoes as liable to self-heat until it has been satisfactorily established that they are not.
The Club says that the shippers cargo declaration containing the cargo properties and the associated hazards should be examined in detail1.It should be borne in mind that the information contained in the declaration may be inaccurate. Inaccurate IMSBC Code declarations have been seen in areas such as Indonesia, where large quantities of coal are shipped. More surprisingly, Gard was involved in a recent case where a coal cargo loaded at Richards Bay, South Africa was inaccurately declared as not self-heating coal nor liable to emit methane. Subsequent investigations involving cargo experts, established that the cargo did in fact possess both properties.
It is therefore recommended that all coal cargoes are treated as potentially hazardous and liable to self-heat until it can be satisfactorily established that they are not. Gard recommends that, for all types of coal, the vessel implements a gas monitoring and temperature checking regime during loading, as further explained below. If the ship’s crew or the Members are in any doubt they should contact the Association for advice and assistance, either directly or through the local correspondent. |
Checking the accuracy of shippers declarations and the IMSBC Code
The Code sets out (1) General requirements for all types of coal and Special precautions for (2) self-heating coal and (3) coal emitting methane.
It is important to note that no particular limit on the temperature of the coal in general is provided in this section. Therefore, should the shipper not declare the coal as self-heating, there is strictly speaking no requirement for the Master to take temperature readings. However, it is recommended that the Master does monitor cargo temperatures and, if these exceed 55C, the master should immediately suspend loading until a proper investigation can be carried out. The relevant parties should be notified in writing and expert advice sought to establish whether the coal is in fact self-heating.
A terminals loading rate from one single loader can be several thousand tonnes per hour, making it difficult for the Master or crew to obtain reliable cargo temperatures. Furthermore, the ships crew may not be permitted access to the terminal, to make checks on stockpiles. A Master may therefore be inclined to rely on any automatic temperature controls contained in the terminals conveyor/loading system. These systems, often found at large coal terminals, may be designed to stop loading when the temperature exceeds a certain limit. However, this is not something the crew can control and whilst terminal readings may be informative, they should not be solely relied upon. It is therefore recommended that the crew checks the temperature of the cargo every time there is a stoppage or a sequence changeover.
The production of noticeable quantities of carbon monoxide (CO) from a coal cargo is also symptomatic of self-heating as described in the IMSBC Code. Therefore, it is also recommended that the crew monitor the carbon monoxide emission as described in the Code. This can be done during a sequence changeover during loading allowing the holds not being worked to be closed down for gas measurements. If CO concentrations of 50 ppm is detected the coal may be self-heating. Such coal can be carried safely as long as the Codes provisions are followed but this entails that the cargo temperature at loading should not be above 55oC.
To avoid an explosive atmosphere developing, gases should be monitored to ensure that the methane content within the hold is below 20% of the Lower Explosive Limit (LEL). Methane is lighter than air and if present will tend to accumulate in the head space above a stow. It is therefore important that the gas measurements cover the high areas above the stow. Furthermore, it is important to ensure that all gas measuring equipment on board is calibrated to ensure the readings are accurate. Although the Code does not expressly say so, methane emitting coal should never be loaded in the same cargo space as self-heating coal due to the risk of an explosion.
Recommendations when loading self-heating and/or high methane levels coal:
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Source & Image Credit : The Gard P&I Club
Note
1.The Code requires that the shipper provides the Master with the characteristics of the coal in writing for all types of coals. This should as a minimum contain the coals moisture content, sulphur content, size and whether the cargo is liable to emit methane or self-heat.