Charging and ignition of sprayed fuel

There have been many recorded incidents of aircraft fuel tank ignition. Whi le electrostatic discharges have undoubtedly started fires during fuelling on the ground, the cause of in-flight fuel tank explosions is difficult to establish and attributing these events to static electricity is very contro versial. This paper describes an experimental investigation into the chargi ng of isolated objects in a fuel spray representing the practical circumsta nce of the electrical isolation of pipe clamps from the grounded pipe withi n the fuel tank. The results, which are presented, show that while charging readily occurs, insufficient charge is retained by the target objects, und er the present conditions, even to cause sparking. The influence of fuel co nductivity on the balance between the rates of charging and charge leakage from the target is examined. The data shows that while fluids with consider able conductivity may wet the insulating material supporting the target obj ect, the leakage resistance can be high. It is concluded that under certain circumstances, increasing fuel conductivity may, therefore, exacerbate the electrostatic problem. (C) 2000 Elsevier Science B.V. All rights reserved.