MIL-PRF-27401G
shall be rounded off in the last right-hand digit used in expressing the specification limit, using the
Rounding Method of ASTM E29.
3.3 Filter.
3.3.1 Containers. A filter with a rating of at least 10-micrometer nominal and 40-micrometer
absolute rating shall be installed between the manufacturer's plant system and the manifold used to fill
the gas or liquid containers for delivery.
3.3.2 Pipelines. A filter with a rating of at least 3.5-micrometer nominal and 12-micrometer
absolute rating shall be installed downstream of compressors and/or converters and as close to the user's
interface as possible for delivery into pipelines. The filter shall remove all particles greater than 100
micrometers in any dimension.
TABLE I. Grade limits for nitrogen.
Grade
Test
Method
A
B
C
a, b
Purity
, % by vol,
min
99.5
99.99
99.995
4.4.1
Impurities, ppm by
c
c
c
--
50
100
5000
volume, max
4.4.2
Water
5.7
11.5
26.3
Total hydrocarbons as
4.4.2
methane
5.0
5.0
58.3
4.4.2
Oxygen
20
50
5000
d
d
4.4.2
Hydrogen
0.5
--
--
d
e
4.4.2
Argon
2
20
--
d
e
4.4.2
5
5
--
Carbon dioxide
d
e
4.4.2
5
5
--
Carbon monoxide
f
Particulate , mg/L, max
1.0
1.0
1.0
4.4.3
Notes.
a. Percent nitrogen includes trace quantities of argon (Grade A), neon, and helium.
b. If direct method is required, use the alternate method found in 6.3.
c. Sum, in parts per million (ppm), of water, hydrocarbons, oxygen, and if applicable, argon,
hydrogen, carbon monoxide, and carbon dioxide.
d. No limit for this grade.
e. If required by contract (see 6.2).
f. Applies only to Type II (Liquid) nitrogen. The particulate limit may be removed by the procuring
activity (see 6.2).
4
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