MIL-DTL-45300C
4.6.4 Leakage (all types). To determine conformance to 3.4.2, a filler neck, with cap mounted, shall be placed in
an airtight chamber (see figure 1). The chamber shall be 3/4 filled with a liquid of the viscosity of gasoline. It shall be
rotated to place the cap below the liquid level. An internal pressure of 2 psi shall be applied for type I and 1 psi for
types 11 and III caps and any leakage shall be recorded.
4.6.5 Pressure relief valve opening.
4.6.5.1 Type 1. To determine conformance to 3.4.3.1, fabricate an air pressure chamber from a MS35644 filler
neck assembly. Gradually increase the air pressure to verify that the relief valve opens at 4 to 5 psig. The vent
opening may be plugged with a rubber stopper. For safety reasons, the air supply system should be designed to
preclude exceeding 10 psig. Since the effective area of the relief valve is approximately 1 square inch, an equivalent
mechanical force may be used in lieu of air pressure. Visually observe the relief valve opening with a 4 to 5 lb force
applied to the ball chamber by a suitable means, such as a spring scale.
4.6.5.2 Type II. To determine conformance to 3.4.3.2, the cap shall be placed on a filler neck and the fording valve
shall be closed. Internal pressure of the filler neck shall be increased at a rate not exceeding 0.1 psi per second until
pressure relief valve opens at a maximum of 6 psi is obtained.
4.6.6 Free breathing (types I and II). To determine conformance to 3.4.4, the cap shall be installed on a filler neck
that is mounted on testing apparatus conforming to figure 2. One psi of vacuum shall be applied and the air flow
meter shall be checked for resulting air flow through the cap.
4.6.7 Shear strength (all types). To determine conformance to 3.4.5, the cap shall be mounted on a filler neck.
Torque shall be applied with a torque wrench until the rotation of the inner member of the type I cap with respect to its
outer shell and until rotation of cup on inner plate or inner plate on shell for type II and type III caps occur. The value
of torque in foot-pounds shall be recorded.
4.6.8 External pressure (types I and II). To determine conformance to 3.4.6, the cap shall be mounted on a filler
neck. The assembly shall be inverted and placed in an airtight container (see figure 1) filled 3/4 full of water. The
cap shall be below the water surface and the filler neck shall be vented to atmospheric pressure. A pressure of 5 psi
shall be applied to the airtight container and maintained for 60 to 70 seconds after which the assembly shall be
disassembled and inspected for leakage.
5. PACKAGING
5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in the contract or order
(see 6.2). When packaging of materiel is to be performed by DoD or in-house contractor personnel, these personnel
need to contact the responsible packaging activity to ascertain packaging requirements. Packaging requirements are
maintained by the Inventory Control Point's packaging activities within the Military Service or Defense Agency, or
within the military service's system commands. Packaging data retrieval is available from the managing Military
Department's or Defense Agency's automated packaging files, CD-ROM products, or by contacting the responsible
packaging activity.
6. NOTES
6.1 Intended use. Caps covered by this specification are used on the following vehicles.
6.1.1 Type I. The cap is used on military tactical vehicles which are not used in fording operations.
6.1.2 Type II. The cap is used on military tactical vehicles with fuel supply systems designed for atmospheric
venting through the fuel cap (fording valve open) and fuel systems incorporating a vacuum relief valve or combination
vacuum and pressure relief valve (fording valve closed).
6.1.3 Type III. The cap is used on military combat and tactical vehicles with fuel supply systems designed for
atmospheric venting by way of the engine air induction system or direct-to-atmospheric above the water line on
fording.
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