MIL-STD-202H.pdf - 第37页

MI L - S TD - 202 - 10 6 CO NT E N T S PARAGRAPH PAG E FOREW ORD … ………………………………………………………. ii 1. SCOPE 1 1.1 Purpose …… ………………… …………………. …… .. …………. 1 2. APPLICABLE D O C U M EN T S 1 3. DEFINTIONS 1 4. GENERAL RE Q UI R …

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MIL-STD-202-106
FOREWORD
1. This standard is approved for use by all Departments and Agencies of the Department of Defense.
2. This entire standard has been revised. This revision has resulted in many changes to the format, but the most
significant one is the splitting the document into test methods. See MIL-STD-202 for the change summary.
3. Comments, suggestions, or questions on this document should be emailed to std202@dla.mil or addressed to:
Commander, Defense Logistics Agency, DLA Land and Maritime, ATTN: VAT, P.O. Box 3990, Columbus, OH
43218–3990. Since contact information can change, you may want to verify the currency of this address
information using the ASSIST Online database at https://assist.dla.mil.
ii
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MIL-STD-202-106
CONTENTS
PARAGRAPH PAGE
FOREWORD…………………………………………………………. ii
1. SCOPE 1
1.1 Purpose………………………………………….……..…………. 1
2. APPLICABLE DOCUMENTS 1
3. DEFINTIONS 1
4. GENERAL REQUIREMENTS 1
4.1 Apparatus ……………………………………………..…………. 1
4.1.1 Chamber………………………………………………………….. 1
4.1.1.1 Opening of the chamber door………………………………….. 1
4.1.1.2 Water……………………………………………………………… 1
4.2 Procedure………………………………………………………… 2
4.2.1 Mounting………………………………………………………….. 2
4.2.2 Initial measurements……………………………………………. 2
4.2.3 Number of cycles………………………………………………… 3
4.2.4 Subcycle of step 7……………………………………………….. 3
4.2.4.1 Step 7a……………………………………………………………. 3
4.2.4.2 Step 7b (when applicable)……………………………………… 3
4.2.5 Polarization and load. …………………………………………… 3
4.3 Final measurements……………………………………………… 3
4.3.1 At high humidity…………………………………………………… 3
4.3.2 After high humidity……………………………………………….. 3
4.3.2 After high humidity………………………………………………. 3
4.3.3 After drying period……………………………………………….. 3
5. DETAILED REQUIREMENTS 4
5.1 Summary……………..…………………………..………………. 4
6. NOTES 4
6.1 Supersession data………………………………………………. 4
FIGURE PAGE
1. Graphical representation of moisture-resistance test.…………….. 2
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MIL-STD-202-106
METHOD 106
MOISTURE RESISTANCE
1. SCOPE
1.1 Purpose. The moisture resistance test is performed for the purpose of evaluating, in an accelerated manner,
the resistance of component parts and constituent materials to the deteriorative effects of the high-humidity and heat
conditions typical of tropical environments. Most tropical degradation results directly or indirectly from absorption of
moisture vapor and films by vulnerable insulating materials, and from surface wetting of metals and insulation. These
phenomena produce many types of deterioration, including corrosion of metals, physical distortion and decomposition
of organic materials, leaching out and spending of constituents of materials; and detrimental changes in electrical
properties. This test differs from the steady-state humidity test (method 103 of this standard) and derives its added
effectiveness in its employment of temperature cycling, which provides alternate periods of condensation and drying
essential to the development of the corrosion processes and, in addition, produces a "breathing" action of moisture
into partially sealed containers. Increased effectiveness is also obtained by use of a higher temperature, which
intensifies the effects of humidity. The test includes low temperature and vibration subcycles (when applicable, see
4.2.4.2) that act as accelerants to reveal otherwise indiscernible evidence of deterioration since stresses caused by
freezing moisture and accentuated by vibration tend to widen cracks and fissures. As a result, the deterioration can
be detected by the measurement of electrical characteristics (including such tests as dielectric withstanding voltage
and insulation resistance) or by performance of a test for sealing. Provision is made for the application of a polarizing
voltage across insulation to investigate the possibility of electrolysis, which can promote eventual dielectric
breakdown. This test also provides for electrical loading of certain components, if desired, in order to determine the
resistance of current-carrying components, especially fine wires and contacts, to electro-chemical corrosion. Results
obtained with this test are reproducible and have been confirmed by investigations of field failures. This test has
proven reliable for indicating those parts which are unsuited for tropical field use.
2. APPLICABLE DOCUMENTS
This section not applicable to this standard.
3. DEFINTIONS
This section not applicable to this standard.
4. GENERAL REQUIREMENTS
4.1 Apparatus
4.1.1 Chamber. A test chamber shall be used which can meet the temperature and humidity cycling specified on
figure 1. The material used to fabricate the platforms and standoffs, which support the specimens, shall be non-
reactive in high humidity. Wood or plywood shall not be used because they are resiniferous. Materials shall not be
used if they contain formaldehyde or phenol in their composition. Provisions shall be made to prevent condensate
from the chamber ceiling dripping onto the test specimens.
4.1.1.1 Opening of the chamber door. During the periods when the humidity is ascending or descending, the
chamber door should not be opened. If the chamber door must be opened, it should be opened during the 16th hour
through the 24th hour of an individual cycle. While the chamber is at 25°C (77°F), and the relative humidity tolerance
must be maintained, the chamber door should be opened only for a short period of time.
4.1.1.2 Water. Steam, or distilled and demineralized, or deionized water, having a pH value between 6.0 and 7.2
at 23°C (73.4°F) shall be used to obtain the specified humidity. No rust or corrosive contaminants shall be imposed
on the test specimens by the test facility.
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