MIL-PRF-27720G
The insulation shall not settle or be displaced in service. If a getter (impurity absorbing) material
is used in the annular space, it shall be secured in direct thermal contact with the inner shell (see
4.5.1, 4.5.10).
3.5.8 Liquid line. A single liquid line shall be provided between the inner and outer shells for
filling and emptying the tank. The line shall be not less than 1 inch in diameter. The line shall
permit liquid withdrawal at a height not less than 1.0 inch or more than 1.25 inches above the
bottom of the inner shell to preclude withdrawing sediment with the liquid. The installation shall
ensure against liquid entering the line from the inner shell when all liquid line valves are closed
and the tank is tilted 10 degrees along either the longitudinal or lateral axis. The installation
shall also ensure that the inner shell can be gravity drained to the level of the standpipe through
the liquid fill line or liquid servicing line without pressurization (see 4.5.1).
3.5.9 Liquid fill line. The tank assembly shall have a liquid fill line for filling the tank with
liquid oxygen or nitrogen. The fill line shall have a manual shutoff valve as near as possible to
its connection to the liquid line (see 3.5.8). The line shall have a diameter of not less than 1 inch
and shall terminate outside the control housing in a 1-inch external pipe thread for installation of
the disconnect coupling. The fitting mounting shall withstand a torque of 300 ft-lb per inch of
nominal line size applied to the fitting in either direction. The mounting shall have clearance to
allow use of a 24-inch wrench (see 4.5.1, 4.5.14). The disconnect coupling shall be as follows:
a. For the Type I oxygen tank, the disconnect coupling shall consist of a coupling cap, seat,
and gasket, conforming to Ordnance Corps drawings C8987869, C8987855, and B8987833,
respectively, assembled as shown on drawing C8987830. The horizontal centerline distance
between the fill line termination and the servicing line termination shall be a minimum of 9.0
inches (see 4.5.1, 4.5.14).
b. For the Type II nitrogen tank, the disconnect coupling shall consist of a coupling cap,
seat, and gasket, conforming to Ordnance Corps drawings C8987890, C8987876, and
B8987833, respectively, assembled as shown on drawing C8987888. The horizontal
centerline distance between the fill line termination and the servicing line termination shall
be a minimum of 9.0 inches (see 4.5.1, 4.5.14).
3.5.10 Liquid servicing line. The tank assembly shall have a liquid servicing line for
transferring liquid oxygen or nitrogen from the inner shell. The servicing line shall have a
manual shutoff valve as near as possible to its connection to the liquid line (see 3.5.8). The line
shall have a diameter of not less than 1 inch and shall terminate outside the control housing in a
1-inch external pipe thread disconnect fitting, oriented to discharge vertically upward, for
attachment of the liquid servicing hose (see 3.4.2). The fitting mounting shall withstand a torque
of 300 ft-lb per inch of nominal line size applied to the fitting in either direction. The mounting
shall have clearance to allow use of a 24-inch wrench (see 4.5.1, 4.5.14).
3.5.11 Vapor vent line. The tank assembly shall have a vapor vent line that will permit filling of
the tank as specified (see 3.6.4). The line shall have an inside diameter of not less than 1 inch.
The line shall extend along the top inside of the inner shell and shall have spray holes so that
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