• Method adopted/last revised: 2002
• Method reapproved: None
• REF/ISBN: IP463-2935231
• Status: Current
• First printed in STM books: January 2002

Scope

This standard specifies an ambient temperature procedure for the rapid determination of the presence of compounds in middle distillate fuels which affect the potential instability in storage. The fuel types include automotive and marine diesel fuels, heating fuels and gas turbine fuels, in which products of fuel degradation lead to performance problems. The test method uses a portable spectrophotometer to measure the  absorbance of light caused by the presence of phenalene and/or phenalenones, and can thus be carried out on site or in the laboratory. It is applicable to distillate fuels from both petroleum and non-petroleum origin, and at all points in the distribution chain from refinery to end use. It is also applicable to fuels containing dyes and/or markers, but not those containing residues from petroleum processing. It may not give the same predictive power on potentially unstable fuels containing other degradation precursors.

NOTE 1 - Def Stan 91-4 , allows the requirement for test by Def Stan 05-50 Part 40 to be waived, if the result by this standard is less than 0,20 absorbance units (AU). This level of absorbance has been shown to be equivalent to 10 mg/l total sediment.