Fuel Tank Explosion Protection

Small-scale and large-scale experiments were conducted to determine the flame arrester effectiveness of three types of hollow, perforated polyethylene spheres proposed for fuel tank fire and explosion protection. In small-scale experiments, the flame quenching effectiveness of the spheres decreased with an increase in initial pressure and flame run-up distance (ignition void length) and with a decrease in sphere size and packing density. Randomly-packed beds of sphere types A (1-inch diameter, 0.1-inch perforations) and B (1-inch diameter, 0.05-inch perforations) were effective in preventing flame propagation at pressures up to 5 and 0 psig, respectively, whereas sphere type C (3/4-inch diameter, 0.10-inch perforations) failed at 0 psig; with uniformly-packed beds, none of the spheres failed at 0 psig. All three types were noticeably less effective than 10 pore/inch reticulated polyurethane foam. Results from most of the large-scale gun firing experiments with randomly-packed spheres revealed that the spheres were not effective in preventing flame propagation at 0 psig in a 74-gallon modified fuel tank. Other data that were obtained in pressure drop experiments at various air velocities indicated that the flow resistance is slightly greater for sphere type C than for A or B. Empirical relationships are presented for predicting the pressure drop gradients across dry and wet beds of the spheres at air velocities from 5 to 25 ft/sec.