Compatibility of DiEGME and TriEGME Fuel System Icing Inhibitor Additives with BMS 10-39 Aircraft Tank Topcoat Material

Abstract

In recent years, the fuel system icing inhibitor (FSII) diethylene glycol monomethyl ether (DiEGME) has been implicated in an increasing incidence of peeling of topcoat material in the ullage space of integral wing tanks in the B-52 and other military aircraft. Work has indicated that, for the combination of DiEGME in JP-8 fuel, the icing inhibitor additive can concentrate in the tank ullage and condense at elevated concentrations on cooled tank walls. These high concentrations of DiEGME cause swelling and subsequent peeling of the epoxy-based topcoat. Here, we report on detailed studies of the compatibility of DiEGME and FSII replacement candidate triethylene glycol monomethyl ether (TriEGME) with BMS 10-39 fuel tank topcoat material. Tests were designed to simulate fuel tank wall exposures with subsequent topcoat degradation measured by icing inhibitor uptake analyses and pencil hardness evaluations. The lower volatility of TriEGME relative to the JP-8 fuel components results in it being less able to concentrate in the tank ullage and promote topcoat failure, as compared to DiEGME. This was confirmed with lower additive levels measured in the ullage, condensed vapors, and the exposed topcoat material. The pencil hardness of topcoat material exposed to fuel vapors was significantly improved upon changing from DiEGME to TriEGME exposure. Simulation experiments were able to reproduce the fuel tank topcoat peeling observed in the field as well as determine the conditions (concentration and temperature) required for topcoat degradation.

Effects of TRiEGME on water icing behavior in aviation turbine fuel

“…Because of its corrosivity and high vapor pressure, the peeling of aircraft fuel tank topcoat material has been identified with the use of DiEGME. TriEGME has been proposed as a potential DiEGME replacement and has already demonstrated more compatible with aircraft fuel system materials as shown in references . However, its use has not been accepted by airworthiness authority because of lack of thermodynamic data of water in jet fuel when TriEGME is added.…”

“…It is a hydrophilic material with the potential for strong hydrogen bonding to water, thus increasing water solubility and lowering freezing point . It has been successfully applied to military aircrafts for years till recently, it has been identified to be associated with the peeling of fuel tank topcoat material, which results in increase in scheduled and unscheduled maintenance costs and decrease in aircraft mission capabilities . The swelling and peeling of epoxy‐based topcoat in the ullage space of integral wing tanks is partially attributed to the contact between topcoat materials and jet fuel condensates with relatively high DiEGME concentration in them.…”

“…It shall also be able to partition into the aqueous phase creating a solution with a low freezing point. Of all the potential candidates, triethylene glycol monomethyl ether (TriEGME) fits all the aforementioned requirements . Experiments have already demonstrated TriEGME has a better compatibility with aircraft tank topcoat material than DiEGME .…”

“…Of all the potential candidates, triethylene glycol monomethyl ether (TriEGME) fits all the aforementioned requirements . Experiments have already demonstrated TriEGME has a better compatibility with aircraft tank topcoat material than DiEGME . Even though numerical experiments have illustrated TriEGME is a good candidate for DiEGME replacement, it still has not been officially accepted by airworthiness authority because of lack of understanding its nature and interaction with water and fuel.…”

National Aerospace Fuels Research Complex

“…RZPF evaluated both alternative FSIIs (such as triethylene glycol monomethyl ether) and lower levels of the current FSII to ensure that the effectiveness of the additive is maintained [7,8]. Flight tests involving both options are planned in 2010.…”