Jan 252009

Amendments by the International Maritime Organisation, IMO, to mandate the use of inert gas, IG, on oil and chemical tankers carrying low flashpoint cargoes are being opposed by the International Parcel Tankers Association, IPTA,in part because of what it believes will be heightened dangers during confined and enclosed space entries.

Says IPTA: “IPTA is concerned that the imposition of a mandatory IG requirement is widely viewed as a kind of¬†universal panacea that will automatically protect seafarers. We feel it important that those involved in the debate should have a full understanding of all the underlying issues, including the operating practices of the chemical tanker trade, which are very different from those of the oil tanker trade, and could lead to chemical tanker crews facing even more risk from asphyxiation than from the dangers nitrogen IG would be intended to protect them from.”

The association points out: “The Inter Industry Group, after lengthy deliberations, concluded that the primary contributory factor in most of the incidents was a failure to follow procedures, not just onboard ship, but at the highest level of management ashore.”

Some low-flash products are extremely high volume cargoes. Roughly 167 million tonnes of chemical products are shipped in bulk each year. Just nine products, namely Methanol, Ethanol, Ethylene dichloride, Styrene Monomer, Benzene, MTBE, Xylenes, Toluene Acetic acid, make up some 49 million tonnes, or 29% of this. If one factor in the 260 other low-flash products that are carried in smaller quantities, it becomes clear that low-flash cargoes are likely to make up a substantial portion of the cargoes carried on a parcel or chemical tanker. Some tankers have as many as 50 cargo tanks.

There are currently around 1,800 IMO-classed chemical tankers of between 3,000 dwt and 30,000 dwt trading internationally, although some are operated effectively as product tankers in the clean petroleum trade and only infrequently carry Annex II cargoes, while others will carry primarily vegetable oils and/or easy chemicals.

IPTA argues: “Most chemical cargoes entail a relatively high level of tank preparation, which will usually involve the crew entering the tank to complete cleaning operations and then again to inspect the tanks prior to presentation for loading. In most cases, an independent cargo surveyor will also enter the tanks to verify that they are ready for loading. Since these operations usually involve more than one person entering the tank, a full loading programme on a vessel with 30 tanks could involve over 200 man/tank entries. At a very conservative estimate, 900 vessels will be involved in the parcel trade. If one estimates an average of 30 tanks per vessel, and a conservative hypothesis of 5 loading programmes per year, one arrives at 900,000 man/tank entries per year. If one assumes that 40% of those entries will be into tanks that have held a low-flash cargo which, under a regime mandating inert gas for chemical carriers, would be inerted with nitrogen, we are left with more than 350,000 tank entries per year where, if procedures are not followed very rigidly, there is a possibility of asphyxiation.”

Another issue that concerns IPTA is addition fuel consumption: “The need to run a nitrogen generator will, naturally, increase fuel consumption. Information received indicates that the amount of the increase would be around 1.2 tonnes per day for a 875 m3/h generator operating at 95% capacity on a 6,000 dwt vessel and between 2.5 tonnes and 3 tonnes per day for a 1,000 m3/h generator operating at 95% capacity on a 19,000 dwt vessel. For a 40,000 dwt ship running a generator of 3,500 m3/h, the fuel consumption can be as high as 5 tonnes per day.” This would increase emissions.

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