You may find the introduction article from following link:https://pals.com.tr/blog/environmental-test-engineering-and-pals-service-article-series-1
We will proceed to elaborate on the "Methods" and "Procedure"s of environmental standard of MIL-STD-810 in our article series. Instead of writing down the obvious information already given in the standard, we will be discussing more practical information on product design, features regarding "Equipment Under Test" (EUT) and conducting tests.
The immersion test is performed to determine if the materiel can withstand immersion or partial immersion in water (e.g., fording), and operate as required during or following immersion. This method is used for materiel that may be exposed to partial or complete immersion, with or without operation. This test may, in some cases, be used to verify watertightness in lieu of a rain test, provided the material configuration would be the same for both situations, and the method of water ingress is well understood. There are documented situations in which the impact of rain causes pumping of water across seals during the rain test. That does not occur when seals are held tight against a backing plate by the static pressure of the immersion test. In most cases, both tests should be performed.
Procedure I – Immersion. Primarily addresses leakage during immersion of encased materiel.
Procedure II – Fording. Focuses on vehicles traversing a body of water or materiel secured to such vehicles.
• Use a test item configuration that reproduces, as close as possible, the anticipated materiel configuration during storage or use, such as:
a. Enclosed in a shipping/storage container or transit case.
b. Protected or unprotected.
c. Deployed realistically or with restraints, such as openings that are normally covered.
• Identify the appropriate climatic conditions for the geographic areas in which the materiel will be operated and stored, and whether or not the test item needs to be operated during the test.
• For complete immersion, use a 1m covering depth or the required depth identified in the LCEP or other documents. This is measured from the uppermost surface of the test item to the surface of the water. When testing to depths greater than 1m within a pressure vessel, completely immerse the test item in water, then apply pressure. For partial immersion, specify depths as being measured from the base of the material rather than from the top.
• Three options are provided for the conditioning of the test item:
a) 27°C above the water temperature - to represent exposure to solar heating immediately prior to immersion.
b) 10°C above the water temperature to represent a typical temperature difference between materiel and water.
c) Equal to the water temperature to represent situations in which little or no temperature differential exists. This may be used for large items for which adequate conditioning facilities are not available, provided the depth of immersion is adjusted to result in the same differential pressure.
• Use a duration of immersion typical of that anticipated during use. If this duration is unknown, a 30-minute immersion period is considered adequate to develop leakage if it is to occur. Use one hour fording durations that may be extended if justified by the anticipated life cycle profile.
• The formation and location of bubbles during testing will indicate leaks. It is also important to know the water temperature 15 minutes following immersion and the pretest water and test item temperatures.
• After completion of the test the amount of free water inside the item ,and probable points of entry should be noted. Notes should be made about the actual covering depth of water and the duration of immersion. Any deviations from the original test plan and appropriate photographs should be recorded.
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