MIL-PRF-27407D
TABLE II. Sampling for test.
Number of containers in lot
Number of containers to be sampled
1
1
2 40
2
41 70
3
71 over
4
4.2.2 Sampling tests. Type I helium shall be selected according to 4.2.2.1 and tested for the
requirements of Table I as specified in 4.4. Type II helium shall be selected according to 4.2.2.2 and
tested for the requirements of 3.1.2 as specified in 4.5.
4.2.2.1 Sampling plan (Type I). The number of helium containers sampled from each lot, as
defined in 4.2.3, shall be selected in accordance with Table II.
4.2.2.2 Sampling plan (Type II). One sample shall be taken from each lot, as defined in 4.2.3.
4.2.3 Lot. A lot shall consist of one of the following:
a. Type I. For gas cylinders, a lot is defined as all of the helium supplied in one or more
container(s) filled from a single manifold at the same time. This includes gas containers that are
interconnected by a single manifold that equalizes the pressure across all the containers. The first and
last cylinders filled within a given lot are typically sampled. Other samples may be selected at random as
required (see 6.2).
b.
Type II. Each filled container shall constitute a lot.
4.2.4 Sample. Each sample shall be of sufficient size to conduct all the quality conformance
tests as specified herein. Unless otherwise specified, the quality conformance tests shall be performed
on each required sample (see 6.2). When required, an equivalent sample shall be forwarded to a
laboratory designated by the procuring activity for testing. Each sample taken for analysis shall be
representative of the entire contents of the container being sampled.
4.2.5 Sampling Methods. Unless otherwise specified in the acquisition requirements, sampling
shall be accomplished by one of the following methods.
a. Type I, gaseous helium may be sampled in accordance with ASTM F307 and Type II, liquid
helium may be sampled in accordance with ASTM F310. It is critical that the sampling port be clean and
free of contaminants.
b. Connect the shipping container being sampled directly to the analytical equipment using
suitable pressure regulation as required to prevent over-pressurization of the equipment.
4.3 Rejection. When any sample tested in accordance with 4.4 or 4.5 fails to conform to the
requirements specified herein, the entire lot represented by the sample shall be rejected.
4.4 Analytical procedures (Type I). Unless otherwise specified, samples shall be analyzed
according to the procedures described below. Calibration gas standards may be required to calibrate
(zero and span) analytical instruments used to determine the purity and impurity contents of the helium.
The accuracy of the calibration gas standards is to be traceable to the National Institute of Standards and
Technology (NIST).
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