Gard 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. We refer to our Loss Prevention Circular No 15-2008 “Loading of hot Coal at Maputo, Mozambique”which highlights the risks involved in the loading of this potentially hazardous cargo. The circular also highlights the importance of the crew’s vigilance and the need to follow the regulatory requirements contained in the IMSBC Code during loading.
The shipper’s cargo declaration containing the cargo properties and the associated hazards should be examined in detail.1 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 shipper’s 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.
- General requirements for all types of coal: Paragraph 5 of the Code states: “It is recommended that means be provided for measuring the temperature of the cargo in the range 0oC to 100oC to enable the measurement of the temperature of the cargo while being loaded and during the voyage without requiring entry into the cargo space”.
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 55°C, 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 terminal’s 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 ship’s 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 terminal’s 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 Code’s provisions are followed but this entails that the cargo temperature at loading should not be above 55oC.
- “Special precautions” for self-heating coal; According to the “Special precautions” for the carriage of self-heating coal, sub-section 3 of the Code states: “Prior to loading, the temperature of this cargo shall be monitored. This cargo shall only be accepted for loading when the temperature of the cargo is not higher than 55oC.” The Code’s wording is very clear when stating “shall only be accepted” to stress that any coal with temperature in excess of 55oC should not be loaded. The Master is fully entitled under the Code, and in fact obliged to, to resist loading such cargo and should insist that the cargo is discharged and replaced with Code compliant cargo to fulfil his obligation to ensure the vessel’s safety.
- Coal emitting methane: Methane is a highly flammable gas at concentrations of between 5% and 16% in the air. Such concentrations inside cargo spaces will create a flammable atmosphere and can lead to explosion if a source of ignition is introduced. It is therefore strictly prohibited to not carry out any hot work on deck, inside cargo holds or inside spaces adjacent to the cargo spaces. The restriction goes for all sources of ignition including smoking.
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:
- Prior to loading coal it is important that the vessel has multi gas detectors on board capable for measuring oxygen (O2), methane (CH4), carbon monoxide (CO) and hydrogen sulphide (H2S). These gas detectors should have sufficient length on the inlet hose to reach all levels of the free space in the holds. Furthermore, the equipment should be calibrated before the operation to ensure accurate reading.
- In addition to gas detection, the vessels fire-fighting systems should be checked to ensure they are in a state of readiness during loading and throughout the voyage. Vessels fitted with fixed CO2 systems should blow through the lines using compressed air prior to commencement of loading to ensure that all cargo holds are well covered by the CO2 system.
- According to the IMSBC Code, self-heating can be controlled by sealing the holds to starve the atmosphere of oxygen. However, controlling the explosion hazard stemming from methane requires the opposite, namely ventilation, to ensure that the methane content of the atmosphere inside the cargo holds stays below 20% of the Lower Explosive Limit (LEL) for methane. The IMSBC Code states that where risks of both self-heating and an explosion are found together whilst at sea, the provision to ventilate takes precedence.
- The importance of monitoring temperature and hold atmosphere is absolutely critical for vessels carrying any type of coal. When faced with a situation where the master suspects self-heating and/or excess accumulation of methane in the hold atmosphere, the master should contact the owners as well as the Club immediately so that coordinated efforts to mitigate the fire hazards can be carried out.
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 coal’s moisture content, sulphur content, size and whether the cargo is liable to emit methane or self-heat.