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Determining the Failure Mechanisms in Water-Absorbing Filter Monitor Elements, 08-9416

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Principal Investigators
Gary Bessee
Scott Hutzler
Vic Hughes (Consultant)

Inclusive Dates: 08/25/03 - 10/15/03

Background - The aviation industry currently faces a major threat to fuel quality with water-absorbent fuel monitors prematurely failing in the field. Aviation pipelines and airport terminals use water-absorbent monitor elements to remove free water from the aviation fuel during aircraft re-fueling. Recent inspections of monitors in the field revealed that they are potentially performing only one-third of their advertised life. Industry has performed limited research, with no success, to determine the cause of these failures.

Approach - New and used water absorbent monitors were obtained from manufacturers and a commercial airline, respectively. These monitors will be evaluated according to API 1583 to determine how they function in accordance with the standardized test method. Results will be compared to determine if the used monitors are actually depleted. Laboratory analysis will also be performed to determine if the water-absorbent polymer can be detected. Results for both the new and used monitors will be compared.

Accomplishments - The airline provided used monitors from three manufacturers from a busy airport. New monitors from two manufacturers have been received; other new monitors are expected soon. The API flow loop is being re-configured to perform the API 1583 tests.

Scanning Electron Microscope (SEM) images of one supplier's monitors indicates the water-absorbent polymer is no longer present. Energy-dispersive x-ray (EDX) and diffractive x-ray were also performed to reveal particulate debris on the monitors. Various clay-like minerals were detected.

Nuclear Magnetic Resonance Spectroscopy (NMR), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimeter (DSC) analysis are currently being performed on new and used monitors. NMR will determine the chemical composition of the polymers. TGA and DSC analyses will determine the quantity of polymer present in the new and used monitors. These results will support visual data collected from the SEM images.

A literature search indicated that some water-absorbent polymers are slightly soluble in aromatic compounds. Aviation fuels contain approximately 25 percent aromatics. An extraction was performed using a toluene/water azeotrope with a new monitor. ICP analysis was performed on both the water and toluene factions. An ion known to be present in this polymer was found in both fractions, indicating aromatic compounds very well may be gradually removing the polymer from the monitor.

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