Guidelines for Accepting or Rejecting a Fuel Delivery

ISO Specifications for fuel deliveries



ISO 4259:2006 provides for the systematic evaluation of the validity of a given result and assumes that the sample being analysed is a "representative" sample of the product delivered/received. Clause 9 of ISO 4259:2006 further establishes the means by which a supplier or recipient of fuel can judge its quality compared to the specification when a single test result is available.





First, some ISO 4259 terminology - ISO 8217:2010 tables 1 and 2 specify maximum and/or minimum limits for the true value of a given property as measured by the specified test method.



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True Value



As defined by ISO 4259:2006, true value represents the average of an infinite number of single results obtained by an infinite number of laboratories. Therefore this true value can never be established exactly.



Above: fuel delivery graph and reproducibility

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Reproducibility of test results



This is the closeness of agreement between individual (test) results obtained in the normal and correct operation of the same (test) method on identical test material but under different test conditions. It is the value where there is a 95% confidence that any good laboratory will report for a given sample value.



To apply the ISO standard requires knowledge of the precision statement of the test method used for analysing that parameter. If the test result is more than the specification limit plus 0.59 times the Reproducibility, then it is 95% certain that this fuel is off spec. In algebraic terms, the fuel fails specification when: 

Test Result exceeds Max Specification plus (0.59 x the Reproducibility). If the specification is a lower limit such as Flash Point, the sign is changed to minus. 



All ISO 8217: 2010 fuel category quality parameters can be viewed by clicking here.