Ways of reducing the chances of a fuel tank explosion. I just wonder how many are covered by the use of the bomb bay as a fuel tank.
"To prevent tank explosions, designers have always assumed a flammable vapor exists in the fuel tanks and adopted standards to preclude ignition sources from the fuel tanks. The following are some of the design measures taken to satisfy that philosophy:
a. Surface temperatures inside the tanks, under normal and failure conditions, are kept at least 50°F below the minimum necessary to ignite a fuel-air mixture. Pump motors are kept cool by an integral passage of circulating fuel. The motors have a temperature fuse which cuts the electrical supply before an unsafe surface temperature is reached. In addition, the pumps and other similar equipment inside the tanks, are designed and tested to explosion-proof standards. Where hot air-conditioning pipes external to fuel tanks are routed close to tank walls, such as the engine bleed air pipes in the wing leading edge, it is current practice to position heat-sensitive detector wires on the structure to protect it from overheat in the event of pipe failure or joint leaks.
b. Electrical components and wiring within a fuel tank are designed to handle 1500 volts ac which is well in excess of the power available on the airplane and the operating voltage of the fuel quantity gauging system.
c. Electrical energy applied to any component in the fuel tank is limited to a value that is 10 times lower than the minimum energy necessary to ignite a fuel-air mixture. The minimum ignition energy (MIE) for hydrocarbon vapors is thought to be about 0.25 mj.
d. During the flow of a hydrocarbon type fuel through pipes, valves, filters, etc., an electrostatic charge can be generated in the fuel, which, if relaxed sufficiently fast, could allow the accumulation of hazardous potential levels inside a receiving tank. This is kept within acceptable safe limits by avoiding very high rates of fuel flow in the refueling system and by controlled distribution of the fuel in the tanks, such as bottom loading and
the use of diffusers on pipe outlets. In addition, meticulous attention is paid to electrical bonding of all metallic parts to dissipate the charge. Some countries around the world insist on the use of static dissipater additives in the fuels to increase the fuel electrical conductivity."