MIL STD 810 G – Test Method 512.5 – Immersion
The immersion test is performed to determine if materiel can withstand immersion or partial immersion in water (e.g., fording), and operate as required during or following immersion.
Use this method 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 materiel 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.
Immersion tests are not intended to be used for buoyant items unless the life cycle profile identifies specific applications such as restraints (including palletized loads) that could hold the materiel under water.
Procedure I – Immersion
Step 1. If weight gain is likely to be an acceptable method of determining leakage, weigh the test item.
Step 2. Three times immediately before the test, open and close (or remove and replace) any doors, covers, etc., that would be opened during normal use to ensure any seals are functioning properly and are not adhering to the sealing (mating) surfaces.
Step 3. Measure and record the immersion water temperature.
Step 4. Condition the test item as in paragraph 220.127.116.11 and record the conditioning temperature and duration. Leave the test item’s sealed areas (where appropriate) open throughout the conditioning cycle. Also, materiel occasionally incorporates valves or venting devices that may or may not be opened in normal service use. If the test item incorporates such devices, open them throughout the conditioning portion of the test.
Step 5. Close all sealed areas and valves; assemble the test item in its test configuration and, as quickly as possible, immerse the test item in water so that the uppermost point of the test item is 1 ± 0.1m below the surface of the water, or as otherwise required by the test plan. The orientation of the test item should represent that of its expected in-service orientation. If several orientations are possible, select that which is most severe.
Step 6. Following a 30-minute immersion period (or as otherwise specified in the test plan), remove the test item from the water, wipe the exterior surfaces dry (giving special attention to areas around seals and relief valves) and, if applicable, equalize the air pressure inside by activating any manual valves. Be careful to not allow water to enter the test item while activating the manual valves.
Step 7. If appropriate, re-weigh the test item.
Step 8. Open the test item and examine the interior and contents for evidence of and quantity of any leakage and, if leakage occurred, for probable areas of entry.
Step 9. If appropriate, conduct an operational check of the test item and record results. See paragraph 5 for analysis of results.
Procedure II – Fording
Conduct the fording test in one of two ways: by towing or driving the test item through water at the appropriate depth, or by securing the test item in a tank and flooding the tank to the required depth. Unless otherwise justified, condition the test item as in paragraph 18.104.22.168.
Step 1. If weight gain is likely to be an acceptable method of determining leakage, weigh the test item prior to the test.
Step 2. With the test item in its fording configuration, ensure that any drain plugs or apparatus are closed, and either:
tow or drive the test item into the water at the required depth or,
secure the test item in a watertight tank.
Step 3. If using the tank method, flood the tank to the required height above the bottom of the test item.
Step 4. Maintain the test item in the water for a duration as determined in paragraph 22.214.171.124.
Step 5. Either remove the test item from the water, or drain the water from the facility, and inspect the interior of the test item for evidence of free water.
Step 6. Measure and record the amount of any free water, and the probable point(s) of entry. If appropriate, re-weigh the test item.
NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.