We have been reviewing the licence permit for ExxonMobil and Shell at the Mossmorran complex, which are two very lengthy and complex documents that provide a list of what the operators can and cannot do at the facilities.
One of the restrictions which is worth mentioning is from the section 4.3 Flaring and Venting Operations, specifically;
4.3.2 Flaring which gives rise to, or is likely to give rise to dark smoke emissions greater that the equivalent of Ringelmann shade 2 for periods greater than 15 minutes shall be treated as an incident.
The reason we are highlighting this specific clause is that a couple of months back, when Mossmorran was flaring black smoke, it was reported to SEPA by a local resident, who submitted images both to SEPA and our group, and those images helped provide a timeline and show SEPA that it was an incident.
However, unknown to us, even lesser shades of dark smoke should have been reported to SEPA according to the Ringelmann Shade chart which could also be treated as ‘incidents’ if the duration was longer than 15 minutes.
The reason that the Ringelmann Shade Chart is important is due to what the colours of smoke during flaring events indicate. An explanation of dark smoke and the Ringelmann chart is provided by SOLIFTEC (The Solid Fuel Technology Institute) below;
Dark smoke is partially burned particles of fuel, the result of incomplete combustion. It can be dangerous because small particles are absorbed into the lungs. White smoke is mainly tiny water droplets, generated when vapour released during combustion condenses in cool air. Generally, dark smoke is clearly visible against a light sky but difficult to see at night or against a dark background, white smoke is visible in darkness when illuminated but will be more difficult to see against a light sky background.
Smoke is commonly measured in terms of its apparent density in relation to a scale of known greyness. The most widely-used scale is that developed by Professor Maximilian Ringelmann of La Station d’Essais de Machines in Paris in 1888. It has a 5 levels of density inferred from a grid of black lines on a white surface which, if viewed from a distance, merge into known shades of grey.
There is no definitive chart, rather, Prof. Ringelmann provides a specification; where smoke level ‘0’ is represented by white, levels ‘1’ to ‘4’ by 10mm square grids drawn with 1mm, 2.3mm, 3.7mm and 5.5 mm wide lines and level ‘5’ by all black. A popular version is that published by the U.S. Bureau of Mines in circular 8333 of 1967. The British Standard version (BS2742:1969) alters Ringelmann’s specification to give a chart similar, on modern paper with modern ink, to the probable appearance of charts produced on earlier, possibly darker, paper, with paler ink.
It should be remembered that the data obtained has definite limitations. The apparent darkness of a smoke depends upon the concentration of the particulate matter in the effluent, the size of the particulate, the depth of the smoke column being viewed, and natural lighting conditions such as the direction of the accuracy of the chart itself depends on the whiteness of the paper and blackness of the ink used.
The reason the Ringelmann Shade Chart is worth highlighting, is that many residents will have witnessed Shade 2 and darker emissions, but we reckon will mostly only report emissions on the higher end of the scale.
SEPA cannot monitor emission of smoke on a 24/7 basis and rely upon the operators of the plant to report any incidents, reports from local residents, and their own investigations.
By raising awareness of the Ringelmann Shade Chart, residents overlooking the Mossmorran complex can be more aware of what issues can be reported to SEPA, who will then investigate any reported issue. If the smoke event is Shade 2 (or higher) and longer than 15 minutes, this will then be treated as an incident and appropriate action can be taken to resolve the issue.