Evaluation of Digital Refractometers for Field Determination of FSII Concentration in JP-5 Fuel

Specification MIL-DTL-5624 requires the addition of Diethylene Glycol Monomethyl Ether (DiEGME) as a fuel system icing inhibitor at a concentration of 0.10 vol% to 0.15 vol% at the point of additive addition. During transport of JP-5 fuel from the point of additive injection to the point of use, additive loss is experienced to some degree resulting in additive concentrations frequently below 0.1 vol%. Navy field determination of the additive concentration is currently conducted using the American Society for Testing and Materials, ASTM D5006 referenced HB/B2 Analog refractometer. The HB/B2 refractometer has been in service for over 30 years and is a very precise instrument for DiEGME concentrations above 0.03 vol%. However, HB/B2 analog refractometer scale reading at the low DiEGME concentrations requires interpolation and is subjective. The ASTM D5006 method recently included digital refractometer instruments for DiEGME concentration determination. More precise measurements of DiEGME at low concentrations could be obtained by Navy field operators with the use of the digital refractometers. NAVAIR successfully completed the evaluation of the digital refractometers and determined the ASTM Method D5006 referenced Gammon HB/2D Digital and the MISCO PA202 series digital refractometers are acceptable for Navy field determination of DiEGME fuel system icing inhibitor additive levels in Specification MIL-DTL-5624, JP-5 fuel. The original document contains color images.