21 JANUARY 2003
may be attracted to the F/S while negative ions are attracted to the aircraft tank) The bonding wire
provides a return path for the ions to equalize.
9.4.2. Most electrostatic problems can be prevented through design, bonding, and adhering to safety
procedures. It is important to remember to initially fill tanks and F/Ss slowly.
9.5. Grounding or Bonding Procedures. Although generation
of static electricity
and stray currents
can be reduced, they cannot be completely eliminated. To further reduce the hazard of a possible spark
discharge, static charges can be greatly reduced by proper grounding or bonding techniques. The
following grounding procedures must be followed with still greater care during the storage and handling
of jet fuel because of the increased possibility of ignition by static charge (standard grounding criteria
are in AFMAN 32-1065, Grounding Systems. NOTE: Do not use stainless steel ground rods.
9.5.1. Storage Tanks. Figure 9.1 shows a typical grounding method installed on existing
aboveground tanks. The current design criteria for new aboveground vertical tanks requires the use
of a plastic liner between the sand support of the tank and native soil, so grounding is required. Older
tanks, without a liner, where the tank rests on the earth, do not require the use of ground rods. If
necessary, a grounding system will be installed using galvanized steel ground rods and 6.3- to
9.5-millimeter (0.25- to 0.375-inch) galvanized guy wires as the grounding conductor. No copper is
used in the grounding system. The purpose of this requirement is to eliminate corrosion caused by
steel reacting with copper. On existing aboveground tanks where grounding is provided and the tank
is in contact with the earth (including oil-treated sand), using copper ground rods or copper grounding
conductors, the grounding system should be removed and treated in the same way as prescribed for
new installations. Also, original design criteria calls for various methods of bonding floating roofs to
tank walls in floating-roof tanks. A typical grounding method for existing aboveground tanks is
shown in Figure 9.1; this includes bonding ladders on floating roof tanks as shown in Figure 9.3.
When these bonding cables require replacement, use 2.3-millimeter (0.09-inch) stainless steel wire
rope, nylon-covered (NSN 4010-00-575-6234).