Hazards of coal: Indonesia in focus
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Hazards of coal: Indonesia in focus
Posted on Tuesday 14th June 2011
In light of the dangers that ships and seafarers continue to face in the loading and transport of coal, the UK P&I Club has published a simple “How to monitor coal cargoes from Indonesia” checklist. Self-heating incidents involving coal cargoes have been problematic for centuries. It was a much-feared hazard in the days of wooden sailing ships, and has continued on since the advent of modern steamships. The problems associated with carrying coal by sea are today much better understood, says Karl Lumbers, a Director of Thomas Miller P&I Ltd, Managers of the UK P&I Club:
“When coal cargo oxidises, it spontaneously generates heat and toxic gases such as carbon monoxide. This can lead to flammable atmospheres in the hold, depletion of oxygen in those spaces and corrosion of metal structures. Lower quality coals such as lignite are more prone to this process than higher quality coals such as anthracite. Understanding the quality of coal being shipped and how to monitor it is fundamental to reducing the risk of self-heating, and possibly the outbreak of fire.”
Indonesia a real problem
The UK Club believes one country whose coal exports present a real threat to ships and seafarers is Indonesia and it further notes that incidents have become increasingly frequent in recent years. It has therefore published a simple checklist entitled How to monitor coal cargoes from Indonesia. This is being distributed to all Members of the UK Club and can be downloaded in .pdf format from its website – www.ukpandi.com.
The problem is primarily related to the nature of the coals, and may be exacerbated by the way they are handled prior to and during loading.
Coal shipped from Indonesia is likely to contain a significant proportion of lower-rank coals in the sub-bituminous and lignite (brown coal) categories. In general terms, lower rank coals are more susceptible to self- heating than the high rank coals.
Brown coals tend to release more carbon monoxide into the sealed cargo holds than bituminous coals and anthracite. It should be noted that lignite is listed separately in the cargo schedules under the Bulk Cargo Shipping Name (BCSN) system as “BROWN COAL BRIQUETTES”, which are manufactured by compressing dried brown coal particles into blocks.
The UK Club stresses that shippers’ descriptions of the cargo, eg “steam non-coking coal in bulk”, may not reflect the nature and properties of the coal being presented for shipment.
Detailed recommendations for the safe carriage of coal are contained in Appendix 1 of the International Maritime Solid Bulk Cargoes (IMSBC) Code, which became mandatory worldwide on 1 January 2011 and which should be familiar reading for all deck officers serving on bulk carriers and other types of ship that carry bulk cargoes, even if only occasionally.
The new UK Club checklist is intended not as a substitute for reading the full IMSBC Code – it has after all been designed to fit in a pocket – but as an ‘aide memoire’ for the guidance of shippers, shipowners, charterers, surveyors, ships’ crews and other parties involved in the loading and carriage of cargoes of coal. Its main focus is the potential hazard of self heating.
The nature of the hazard
The schedule in Appendix 1 of the Code refers to the BCSN “COAL (bituminous and anthracite)”. As material hazardous in bulk (MHB) it is placed in Group B (and A).
Group B cargoes possess a chemical hazard; coal may create flammable atmospheres, may heat spontaneously, may deplete the oxygen concentration and may corrode metal structures. When the cargo oxidises (generating heat) it releases the toxic gas carbon monoxide. It follows that extreme care should be taken at all times if crew members are required to inspect the cargo while at sea.
Group A cargoes are defined as those which may liquefy if shipped at moisture contents in excess of their transportable moisture limit (TML). This can in extreme cases cause a ship to capsize with very little advance warning.
Indonesian coals are likely to have high moisture content, eg 30 to 40 per cent. It is a country where humidity levels are usually high and where rainfall can be intense. Furthermore, it is common practice to transport coal to the load port in open barges. Thus stability issues may arise as well as the risk of self-heating.
ADDENDUM
The following text lists the various items detailed in the checklist (the full checklist can be downloaded from the UK P&I Club website www.ukpandi.com)
Prior to loading
Documentation (IMSBC Code section 4)
- shipper to supply complete documentation relating to the cargo identified by BCSN as required by the Code (secondary names may be used in addition)
- coal must be declared as either Group B or as Group A and B
- check that shipper has not used outdated classifications such as “Category A” when describing the cargo
- if the shipper declares a value for the TML (Group A cargo), check that additional certification as required by the Code is supplied including recent (less than 7 days) representative cargo moisture content analysis
- consider all coal loaded in Indonesia as having the potential to self heat irrespective of the wording of the shipper’s declaration.
Hold preparation (IMSBC COAL schedule and Appendix)
- all cargo spaces and bilge wells clean and dry
- all residues of waste material or previous cargo removed
- all electrical cables and components in cargo spaces and adjacent enclosed spaces free from defects. Such cables and components to be safe for use in an explosive atmosphere or positively isolated.
Vessel instrumentation
- equipment to measure methane, oxygen and carbon monoxide in the hold atmospheres without entering the cargo space
- equipment to measure pH value of cargo space bilge samples
- it is recommended that a means of measuring the temperature of the cargo whilst it is being loaded and during the voyage is available. (Infra-red thermometers are an invaluable addition to standard thermometers in this regard but only measure the surface temperature. Probes can typically measure at depths up to 1m below the surface).
Temperature monitoring
- temperature of the cargo to be monitored prior to loading. Look for ‘hot spots’
- any cargo at a temperature in excess of 55oC should not be loaded
- note that coal cargoes delivered to anchorage in barges may be particularly susceptible to self-heating as they are exposed to the wind
- shippers and surveyors may quote an ‘average temperature’ measurement in relation to a barge cargo in order to establish a value below 55oC. The Code does not recognise this methodology.
During loading
Temperature monitoring
- monitor the temperature of the cargo regularly during loading, not just when the first barge arrives. The cargo is likely to be hotter towards the bottom of the stow in the barge
- reject any cargo at a temperature in excess of 55oC
- do not stow cargo adjacent to hot areas.
Ingress of air
- employ ‘soft loading’ as much as is possible
- as cargo in partially filled holds will be exposed to ingress of air, avoid undue delays when loading
- if delays occur, close partially filled holds and do not ventilate.
After loading
Trimming
- trim the cargo as level as possible to the boundaries of the cargo spaces
- shippers may resist requests to properly trim. Insist that they do so.
Cargo monitoring
- close and seal the holds immediately after loading in accordance with the Code recommendations for self-heating coals
- begin monitoring of the hold atmospheres for methane, carbon monoxide and oxygen immediately, recording the results and the times they were obtained
- gas monitoring to be done through proper fittings in the holds as described in the Code, not through open accesses or covers.
During the voyage
Cargo monitoring
- monitor the hold atmospheres for methane, carbon monoxide and oxygen at least once a day; more frequently if the carbon monoxide and/or methane concentrations begin to rise steadily. Maintain a proper record of these measurements
- a reduction of the oxygen concentration in a well sealed hold is to be expected
- below an oxygen concentration of about 10%, most instruments in common use will not provide reliable readings of the methane %LEL. (Check your instrument manufacturer’s recommendations on the use of a ‘splitter’ at low oxygen levels and/or seek expert advice if there is cause for concern)
- temperatures measured by lowering thermometers into sounding pipes may be useful in general terms but should not be relied upon to reflect any changes occurring in the bulk of the cargo as temperature monitoring via sounding pipes will only detect heating coal in the immediate vicinity and will not provide information on the bulk of the cargo
- if methane in excess of 20% of the LEL is detected, use surface ventilation in accordance with the Code but only for the minimum time necessary to remove the methane. If this concentration of methane is detected after the oxygen has fallen below 10%, seek expert advice before ventilating
- if carbon monoxide concentration in a closed cargo hold exceeds 30ppm, the Code recommends that the frequency of measurement is increased to twice daily. If the carbon monoxide exceeds 50ppm the Code recommends the owner should be notified to call for expert advice. With Indonesian coal the carbon monoxide level can be significantly higher than these values without indicating the presence of self heating but the owner should still be notified (in accordance with the Code) particularly if the gas concentration continues to rise steadily over a period of three consecutive days.
Please note that recommendations for the cargo space gas monitoring procedure are contained within the Code and the carriage of coal is described in the in UK P&I Club publication Carefully to Carry – Coal cargoes