UFC 3-460-03
21 JANUARY 2003
3.3.5.1.3. After each screen is dry, hold it horizontally and pour tap water onto the screen from a
height of 25 to 50 millimeters (1 to 2 inches) above the screen. Pour water along the entire length
of the screen while slowly rotating the screen. Under test, observe the way the water appears on
the surface of the Teflon-coated screen. If the water soaks through the screen instead of beading
up or rolling off, the screen must be recleaned.
3.3.5.1.4. The Teflon-coated screen must be visually inspected for small cuts and breaks. Small
breaks in the Teflon-coated screen can be repaired for temporary service by patching with a fuel-
resistant sealant, epoxy adhesive, or epoxy-base putty. If major holes appear in the Teflon-coated
screen, rendering it impracticable to repair, the screen should be replaced.
3.3.5.2. Installing and Handling. Just before installing the Teflon-coated screens, agitate the screens
briefly in a container of clean fuel to flush off all remaining water. (Use the same type of fuel being
filtered.) Extra care must be taken during installation to ensure screens are not damaged. Screens
must be installed very carefully to prevent physical damage to the Teflon coating. When installing
the Teflon-coated screen assembly, the securing nut should not be overtorqued, as this can damage
the screen assembly.
3.3.6. Initial Filling of Aviation Turbine Fuel F/Ss. Internal flash fires have occurred within F/Ss. In
some cases, there were no audible sounds or immediate indications of a problem. These incidents are
mainly due to electrostatic ignition of the volatile fuel-air mixture during the initial filling operation.
Ignition inside the F/S is possible regardless of the type of aviation turbine fuel handled (e.g., JP-4,
JP-5, JP-8). In most cases, coalescer elements cannot be grounded or bonded to expeditiously
dissipate the static electric charge that is generated. Slow filling is the only authorized method of
refilling an empty F/S (rule of thumb is to never fill a vessel in less than ten minutes). This slows the
buildup of static electricity in the fuel, reducing the possibility of a spark igniting the explosive
atmosphere inside the vessel.
3.4. Meters. Petroleum systems typically use positive displacement meters designed for either one- or
two-way flow; however, MIL-HDBK-1022A allows turbine and orifice meters under certain
circumstances. One-way flow meters are installed on truck fill stands and receipt facilities. Two-way
flow meters are installed in the filter meter pit of some Type I hydrant refueling systems. The meters
record the actual amount of fuel issued and defueled through the system. Meters used for custody
transfer must be compensated for temperature. MIL-HDBK-1022A describes meter accuracy standards.
3.5. Valves. Manual valves are used to isolate portions of fuel systems, to throttle, to control flow, or
direct the flow of fuel. All valves should be identified on the system charts and identified with a
matching tag or stenciled marking on the valve. See Attachment 4 for a suggested method of identifying
valves.
3.5.1. Plug valves.
3.5.1.1. Lubricated plug valves are not allowed in aircraft fueling systems and must be replaced.
3.5.1.2. Non-lubricated plug valves may be used in new systems or when existing lubricated plug
valves are replaced. They are used as block valves, or where quick shut-off is required in various
parts of the system.
3.5.2. DBB valves (Figure 3.5) conforming to API Specification (Spec) 6D, Pipeline Valves (Gate,
Plug, Ball, and Check), are used as positive isolation valves around tanks and in piping runs. DBB
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