MIL-PRF-27407D
4.4.1 Purity. The helium percent shall be found by determining the aggregate impurities by the
methods of CGA G-9.1. The aggregate impurities shall include all of the impurities listed in Table I,
regardless of the Grade analyzed. The percent helium is the value obtained when this amount,
expressed as volume percent, is subtracted from 100 percent.
4.4.2 Impurities. The analytical procedures described in CGA G-9.1 shall be used to determine
the concentration of each impurity listed in Table I.
4.5 Helium assurance test (Type II). Liquid helium is generally assumed to be extremely pure
because contaminants have been removed during the early stages of the liquefaction process which
occurs at -269°C. It follows that assuring that the fluid is helium is sufficient to verify a contaminant free
product. The requirement for ensuring that the loaded fluid is liquid helium can be satisfied by one of the
following methods:
a. Analyzing the vent gas and verifying the purity for the grade from one of the shipping
containers by:
1. A thermal conductivity detector (TCD) measuring the aggregate impurities that have
different thermal conductivities than helium. The analyzer shall be calibrated at appropriate intervals by
using gas calibration standards (see 4.4).
2. Determining the aggregate impurities using the methods in 4.4.
3. Determining the aggregate of all impurities by mass spectrometer. The percent helium is
the value obtained when the aggregate expressed as percent (v/v) is subtracted from 100%.
b. Demonstrating that fluid in one of the shipping containers or the storage tank from which the
shipping containers are filled is below the hydrogen triple point (-259°C).
4.6 Containers of Type I helium.
4.6.1 Filling pressure. Containers shall be stabilized to 21°C (70°F). Containers shall be tested
for proper filling pressure by attaching a calibrated Bourdon-tube gauge or calibrated electronic equivalent
gauge to the valve outlet. The gauge shall have scale divisions not greater than 100 kPa (15 psi). Then
the valve shall be opened and the internal pressure observed on the gauge. If the internal pressure differs
from the applicable filling pressure value by more than 100 kPa (15 psi), the container, and all other
containers filled from the same manifold at the same time, shall be rejected.
4.6.2 Leakage. Each Type I helium container shall be tested for leaks at the neck threads, stem
packing, and safety device of the valve with leak detection fluid. Valve seat leakage shall be tested after
filling has been completed by connecting a hose to the valve outlet and placing the other end of the hose
under the surface of a liquid. Methods of leak detection and/or the leak check guidance in CGA P-15 may
also be used.
4.6.3 Inspection and maintenance. Compressed gas cylinders shall be inspected, maintained
and charged according to MIL-STD-1411.
4.6.3.1 Valves. Valves shall conform to A-A-59860.
4.6.3.2 Color coding. Government-owned cylinders shall be color coded according to
MIL-STD-101.
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.
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