MIL-STD-202H.pdf - 第82页

MI L - S TD - 202 - 112 C O N T E N T S ( c ont i nued) PARAGRAPH PAG E 6 NOTE S ………… ……………… ………………………. ………………. 14 6.1 Suppression d ata …………… ………………. ………………………… 14 TABLE PAG E I. Fixed co nditions pr o c edur e I I I a …

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MIL-STD-202-112
CONTENTS (continued)
PARAGRAPH PAGE
4.4.4.3 Procedure III…………………..…………………….……..…...... 6
4.4.4.3.1 Testing precautions………..……………………….……..…...... 6
4.4.4.3.2 General procedure………..…………….………….……..…...... 6
4.4.4.3.2.1 Procedure IIIa……………..…………….………….……..…...... 6
4.4.4.3.2.2 Procedure IIIb……………..…………….………….……..…...... 7
4.4.4.3.2.2.1 Activation parameters…….…………….………….……..…...... 7
4.4.4.3.2.2.2 Determination of counting efficiency (k)………..……..…...... 7
4.4.4.3.2.2.3 Evaluation of surface sorption..………………………..…...... 7
4.4.4.3.2.2.4 Specific procedure IIIb…………………………………..…...... 8
4.4.4.3.2.2.5 Personnel precautions…………………………………..…...... 8
4.4.4.3.2.3 Procedure IIIc……………………………..…............................ 9
4.4.4.4 Procedure IV…………………………..…..…............................ 9
4.5 Test Condition D………..…………………….…………………. 9
4.5.1 Materials……..…………………….…………………………..…. 9
4.5.1.1 Fluorocarbon liquid…………….……………………………..…. 9
4.5.2 Apparatus……….……………………………………………..…. 9
4.5.2.1 Heated fluid container………………………………………..…. 9
4.5.2.2 Filter…………………………………………………………….…. 10
4.5.2.3 Magnifier……………………………………………………….…. 10
4.5.3 Precautions…………………………………………………….…. 10
4.5.4 Procedure……………………………………..……………….…. 10
4.6 Test Condition E………..…………………….…………………. 10
4.6.1 Materials……..…………………….…………………………..…. 9
4.6.1.1 Fluorocarbon liquid…………….……………………………..…. 9
4.6.2 Apparatus……….……………………………………………..…. 9
4.6.2.1 Heated fluid container………………………………………..…. 9
4.6.2.2 Filter…………………………………………………………….…. 9
4.6.2.3 Magnifier……………………………………………………….…. 10
4.6.2.4 Chamber……………………………………………………….…. 10
4.6.2.5 Lighting source………….…………………………………….…. 11
4.6.2.6 Instruments…..………….…………………………………….…. 11
4.6.2.7 Fixtures……….………….…………………………………….…. 11
4.6.3 Precautions…………………………………………………….…. 11
4.6.4 Procedure……………………………………..……………….…. 11
4.7 Test Condition F………..…………………….…………….……. 11
4.7.1 Materials……..…………………….…………………………..…. 11
4.7.1.1 Fluorocarbon liquid…………….……………………………..…. 11
4.7.2 Apparatus……….……………………………………………..…. 12
4.7.2.1 Chamber ………………………….…………………………..…. 12
4.7.2.2 Filter…………………………………………………………….…. 12
4.7.2.3 Detector………………………………………………….…….…. 12
4.7.2.4 Instruments..…………………………………………………..…. 12
4.7.3 Precautions…………………………………………………….…. 12
4.7.4 Procedure……………………………………..……………….…. 12
4.7.4.1 Failure criteria………………………………………………….…. 12
4.8 Measurements……………………………………………..….…. 13
5. DETAILED REQUIREMENTS……………………………………...… 13
5.1 Summary………..………………………………………………… 13
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MIL-STD-202-112
CONTENTS (continued)
PARAGRAPH PAGE
6 NOTES………………………………………………….………………. 14
6.1 Suppression data…………………………….………………………… 14
TABLE PAGE
I. Fixed conditions procedure IIIa…………………….………………....…… 6
II. Test pressure and duration for condition F……………………………….. 13
III. Purge time for condition F………………………………………….....…… 13
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MIL-STD-202-112
METHOD 112
SEAL
1. SCOPE
1.1 Purpose. The purpose of this test method is to determine the effectiveness of the seal of a component part
which has an internal cavity which is either evacuated or contains air or gas. A defect in any portion of the surface
area of a sealed part can permit entrance of damaging contaminants which will reduce its effective life. This test will
detect leaks due to the use of inferior sealing materials, or to the manufacturing processes used to form the seal.
The degree of completeness of the seal can be verified by testing in the "as received" condition or after submission to
other environmental or physical-characteristics tests, such as thermal shock, physical shock, or vibration. This test
method does not include the many existing versions of lesser-sensitivity seal tests now appearing in some
specifications, which verify such requirements as "water tightness", "moisture proofness", etc. In those
lesser-sensitivity seal tests, parts are submerged to various depth in water, heated water, water or alcohol with a
vacuum, water with a wetting agent, etc; all these tests depend on observation of bubbles as the criterion for failure.
2. APPLICABLE DOCUMENTS
This section not applicable to this standard.
3. DEFINTIONS
3.1 Standard leak rate. Standard leak rate is defined as the quantity of dry air at 25°C in atmospheric cubic
centimeters flowing through a leak or multiple leak paths per second when the high-pressure side is at 1
atmosphere (760 mm Hg absolute) and the low-pressure side is at a pressure of not greater than 1 mm Hg
absolute. Standard leak rate shall be expressed in units of atmospheric cubic centimeters per second (atm
cm
3
/s).
3.2 Measured leak rate. Measured leak rate (R
1
) is defined as the leak rate of a given package as measured
under specified conditions and employing a specified test medium. Measured leak rate shall be expressed in
units of atmospheric cubic centimeters per second (atm cm
3
/s). For the purpose of comparison with rates
determined by other methods of testing, the measured leak rates must be converted to equivalent standard
leak rate.
3.3 Equivalent standard leak rate. The equivalent standard leak (L) rate of a given package, with a measured leak
rate (R
1
), is defined as the leak rate of the same package with the same leak geometry, which would exist
under the standard conditions of 1.1a. The formula (does not apply to procedure IIIb) in 4.4.4.3.2.3 represents
the L/R
1
ratio and gives the equivalent standard leak rate (L) of the package with a measured leak rate (R
1
)
where the package volume and leak test conditioning parameters influence the measured value of (R
1
). The
equivalent standard leak rate shall be expressed in units of atmospheric cubic centimeters per second (atm
cm
3
/s).
3.4 Sensitivity. (Minimum detectable leak rate). Sensitivity is the smallest leak rate that an instrument, method, or
system is capable of measuring or detecting under specified conditions. To compare sensitivities of two or
more different test conditions, the sensitivity should be converted to sensitivity under standard conditions by
using the appropriate conversion factors.
3.5 Ambient background. For a scintillation-crystal counting station, ambient background is the oscillatory reading
obtained on the meter readout due to electrical noise plus the reading in counts per minute due to cosmic
radiation that penetrates the lead shielding of the closed crystal system. This value must be determined just
before device counting.
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