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GWright Mar 31, 2019 08:13 AM
In the reporting of Fuels Quality, EEA Report No 24/2017 for example, section 3.4 Exceedances of fuel quality limits, talks about tolerance limits. How are the tolerance limits determined? I've looked at EN14724:2013, and it mentions "Limiting Values" -
The limiting values are "true values" according to EN ISO 4259, but I don't see Tolerance Limits mentioned. Are they +/-0.59R depending on a max or min limit, or some other factor of R?
 Very much appreciate your guidance.
Replies (1)
EEA Apr 08, 2019 10:47 AM
Dear M. 'GWright',

Thank you for contacting the European Environment Agency (EEA).

According to Directive 98/70/EC the minimum and maximum limiting values for each parameter are established. Every parameter considered under the Fuel Quality Directive (FQD) is tested using a specific standard (e.g. for RON is EN ISO 5164, for MON is EN ISO 5163 etc.) as mentioned in “Methods&Limits” sheet of Art.8 template. Each standard describes the calculation of Reproducibility, R. The tolerance limits as described in the template are depicting the 95% confidence interval of the measurements taken for every parameter, to make certain that the “true value” (as mentioned in EN ISO 4259) is contained.

Indeed, EN 14274 and the FQD mention only the limit values and not the tolerance limits. However, due to potential miscalibrations of the equipment used for the testing and analysis of the samples, a 95% confidence interval to eliminate values which do not conduct a reliable outcome is applied.
The tolerance limits are defined as the product of R times a +/- 0.59 factor, depending on the implementation on a min or max value.

We hope that this information will be useful for you.

With kind regards,
EEA Enquiry Service