Seasonal variations

As May 1, and its raucous celebrations, mark the traditional end of Winter in Finland ( though this year’s May Day passed in low temperatures and a biting wind), seasonal changes in chemical accidents are again apparent.

As well as the anticipated rise in chlorine compound accidents at swimming pools, marking the beginning of the summer season in the northern hemisphere, it is interesting to note the effects of drought are already apparent. This was also highlighted by May 1 in Oxford, UK, where there was an unusually high number of injuries caused by people leaping into the River Cherwell in a traditional May Morning ritual. What many failed to notice is that an unusually dry spring had left the river only one metre deep. It is not a good idea to leap 8m into 1m of water. Further signs of drought have been apparent here in Finland, where the winter has been short and snowfalls light. In India, a land one tends to associate more with arid conditions than Britain and Finland, Mangalore Refinery & Petrochemicals Ltd was forced to shut down part of its refinery on April 15 because of a shortage of cooling water.

All of these, and other, signs point to the possibility of a potentially difficults ummer for the operators of chemical plant. It is to be hoped that everyone has remembered the lessons of the summer of 2003, when several plants in Europe, Russia and North America suffered cooling problems due to water shortages and high ambient temperatures. The wise ones will have installed extra cooling capacity and kept their heat-exchangers clean; the foolish ones will not have done so, and could be in for a nasty shock. Given the shortage of US refinery capacity, and the near financial panic induced by the loss of an isomerization unit at BP, Texas City, the prospect of even one US refinery shutting downd uring the peak period for gasoline usage is "interesting".

BP Texas City

The investigation into the March 23 explosion of the isomerization unit plods steadily on, but already a probable scenario is emerging. On the current evidence, it appears that the column of the raffinate splitter flooded, and the flooded column over-pressurised, relieving into the blow-down drum.

The volume of material relieved was clearly too large for the blow-down drum and liquid and vapour were expelled through the drum’s vent stack – which was not a flare. (Some have claimed that if the stack had been a flare, the accident might not have happened. This seems unlikely, since such a large volume of liquid would have overwhelmed a flare.)

The question which must be asked is: “Why was the blow-down drum inadequate for the quantity of liquid released?” Normal practice would be to size the blow-down drum on the assumption of a flooded column, which should be adequate unless either there is two-phase flow into the drum or there is a high influx of liquid into thec olumn. Now, it is known that the site of the isomerization unit was originally the site of an ultraformer and it is not unknown that when a plant area changes from one usage to another, as much equipment as possible is salvaged for the new application. Was this the case with the blow-down drum? It is a question that needs to be asked.

Good News

Finally, it is a pleasure to report some good news. As noted in the News section, Brunei Shell Petroleum (BSP) has achieved five million hours without a lost timei njury, while Brunei Shell Marketing (BSM) has achieved four million hours without a lost time injury. Surpassing this, Brunei LNG Sdn Bhd (BLNG) hasa chieved 21 years without a lost time injury at the Seria Oil Refinery. This remarkable achievement by BLNG was marked with a celebration on April 15 where child safety seats were given to staff of the Seria Oil Refinery as part ofe fforts to enhance road safety.

Now if only Shell Brunei would share the secret with everyone else, the world might be a safer place.