Ringelmann scale

The Ringelmann scale is a scale for measuring the apparent density or opacity of Smoke.[1] It was developed by a French professor of agricultural engineering Maximilien Ringelmann of La Station d'Essais de Machines in Paris in 1888.[2] Ringelmann also discovered what is now called the Ringelmann effect.[3]

The scale is 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. Shade 1 is slightly grey and is usually categorized by air pollution boards as acceptable. It corresponds to an opacity of 20%. Shades 2, 3, 4 and 5 correspond to opacities of 40%, 60%, 80% and 100% (completely black) and are usually considered to be "black smoke" by air pollution boards of most countries.[4]

History

Originally when made in 1887, there was no definitive chart, rather, Prof. Ringelmann provided 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. The chart was introduced into the United States by William Kent in an article published in Engineering News of November 11, 1897, with a comment that he had learned of it in a private communication from a Bryan Donkin of London. By then, the scale had come into somewhat extensive use in Europe. Kent proposed in 1899 that it be accepted as the standard measure of smoke density in the standard code for power-plant testing that was being formulated by the American Society of Mechanical Engineers. It was subsequently adopted as a chart by the Technologic Branch of the U.S. Geological Survey (which later formed the nucleus of the US Bureau of Mines) in their studies of smokeless combustion at St. Louis in 1904. By 1910,it became part of Massachusetts legislature and subsequently, the US Department of mines. This is one of the popular versions that is used today.[5]

Versions and uses

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. A four scale version is used by the Hong Kong Marine Department to check smoke emitted by ships.[6]

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 sun relative to the observer while the accuracy of the chart itself depends on the whiteness of the paper and blackness of the ink used.

In use, the observer views the plume at the point of greatest opacity and determines the corresponding Ringelmann Number. A Ringlemann 0, 1, 2, 3, 4 and 5 are equivalent to an opacity of 0, 20, 40, 60, 80 and 100.[7] Some agencies issue cards that can be compared to the smoke while others use apps on phones.[8]

References

  1. ↑ IC 8333 - Ringelmann smoke chart (PDF). USA: Bureau of mines. 1 May 1967. Retrieved 31 August 2018.
  2. ↑ The Ringelmann smoke chart (PDF). The solid fuel technology institute. Retrieved 31 August 2018.
  3. ↑ "Sensing change". https://www.sciencehistory.org. Science history institute. Retrieved 31 August 2018. External link in |website= (help)
  4. ↑ Dark smoke - an introduction to air pollution control (smoke) regulations (PDF). Hong Kong: Environment protection department, Hong Kong. Retrieved 31 August 2018.
  5. ↑ A brief history of the Ringelmann chart (PDF). USA: Department of mines. Retrieved 31 August 2018.
  6. ↑ No excessive dark smoke emissions from vessels (PDF). Hong Kong: Mardep. 1 July 2014. Retrieved 31 August 2018.
  7. ↑ Randolph, Karen; et al. (February 3, 2012). "Visible Emissions Field Manual EPA Methods 9 and 22" (PDF). United States Environmental Protection Agency. Retrieved April 20, 2013.
  8. ↑ "Ringelmann smoke chart (mining publications)". https://www.cdc.gov. CDC, USA. Retrieved 31 August 2018. External link in |website= (help)
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