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MIL-STD-202 Method 104A Immersion Testing

The MIL-STD 202 immersion testing standard was established to determine the effectiveness of the seal of component parts. The MIL-STD-202 immersion test calls for the unit under test to be immersed in liquid at various temperatures. By using these various temperatures, the unit is subjected to thermal and mechanical stresses. These stresses will detect a number of possible problems. These problems can include a partially closed seam, defective terminal assembly or molded enclosure. These problems generally arise from mechanical damage caused by environmental or other physical tests.

In general, an immersion testing lab will complete the immersion testing immediately after the completion of other environmental testing. This order of testing is used because the mechanical testing will tend to aggravate an incipient defect. These defects most commonly occur in bushings, seals and seams. The MIL-STD 202 testing standard is a good guide for completing case testing and enclosure testing.

The MIL Standard 202 testing is essentially a measurement of the effectiveness of the seal or gasket. The effectiveness determination is made by way of an observation.

An immersion test lab can complete the testing using either salt or fresh water. The liquid to use will be based on the nature and use of the component part being tested. After the immersion cycling is conducted, electrical measurements can be made to obtain evidence of leakage through seals. The use of a salt solution instead of fresh water will facilitate the detection of moisture penetration. This test provides a simple and ready means of detection of the migration of liquids. Effects noted can include lowered insulation resistance, corrosion of internal parts, and the appearance of salt crystals. The test described is not intended as a thermal shock or corrosion test. However, this test may incidentally reveal inadequacies in these respects.

The MIL-STD 202 Method 104 immersion test procedure consists of successive cycles of immersion. Each cycle of immersion consists of specific time periods and temperatures.

The first immersion in the test procedure is a hot bath immersion. The hot bath is fresh water or tap water. The water temperature is 65⁰ C +5⁰, -0⁰. The Fahrenheit conversion is 149⁰ F +9⁰, -0⁰. Following the immersion in to the hot bath, an immersion into cold baths is completed. Included below are the test procedures for the cold bath immersions:

Test Condition

Number of Cycles

Duration of Each Immersion

Immersion Bath

Temperature of Cold Bath

A

2

15

Fresh or Tap Water

25⁰ C (+10,-5)

B

2

15

Saturated Solution of Sodium Chloride and Water

25⁰ C (+10,-5)

C

5

60

Saturated Solution of Sodium Chloride and Water

0⁰ C +3

The transfer of items under test from one bath to another bath should be completed as quickly as possible. Upon completion of the final immersion test cycle, the unit must be thoroughly and quickly washed. All of the surfaces then need to be wiped and air-blasted clean and dry.

The final measurements must be made as soon as possible after completion of the final cycle. The MIL-STD-202 spec calls for at least four hours but no more than 24 hours. Upon completion of this ingress protection standard, the following details must be documented. First is the test condition letter. The second is the stated time between the measurement and the final cycle was completed. The final documentation is the measurement itself.

As a leader in ingress protection testing, Keystone Compliance is the chosen MIL-STD 202 immersion testing lab of many manufacturers. We have substantial capabilities with ingress protection and all other mechanical / environmental testing. Contact us to request a quote and realize firsthand why so many companies trust Keystone Compliance as their immersion test lab.