2.1 Selecting the Immersion Method
After examining requirements documents and applying the tailoring process in Part One of this Standard to determine where immersion or fording is anticipated in the life cycle of materiel, use the following to confirm the need for this Method and to place it in sequence with other methods.
2.1.1 Effects of Leakage During Immersion
Penetration of water into materiel or packaging enclosures can result in problems. Consider the following typical problems to help determine if this Method is appropriate for the materiel being tested. This list is not intended to be all-inclusive.
- a. Fouling of lubricants between moving parts.
- b. Formation of electrically conductive paths that may cause electrical or electronic equipment to malfunction or become unsafe to operate.
- c. Corrosion due to direct exposure to the water or to the relatively high humidity levels caused by the water.
- d. Impairment of the burning qualities of explosives, propellants, fuels, etc.
- e. Failure of vehicle engines to operate.
2.1.2 Sequence Among Other Methods
- a. General. Use the anticipated life cycle sequence of events as a general sequence guide (see Part One, paragraph 5.5).
MIL-STD-810H
METHOD 512.6
- b. Unique to this Method.
- (1) There are at least two philosophies related to test sequence. One approach is to conserve test item life by applying what are perceived to be the least damaging environments first. For this approach, generally apply the immersion test prior to most other climatic tests.
- (2) Another approach is to apply environments to maximize the likelihood of disclosing sequential problems. For this approach, consider the immersion test both before and after structural tests such as shock and vibration to aid in determining the test item's resistance to dynamic tests.
2.2 Selecting Procedures
This Method includes two test procedures, Procedure I (Immersion) and Procedure II (Fording). Determine the procedure(s) to be used.
2.2.1 Procedure Selection Considerations
When selecting procedures, consider:
- a. The operational purpose of the materiel. From the requirements documents, determine the functions to be performed by the materiel when partially or completely immersed in water.
- b. The natural exposure circumstances.
- c. The test data required to determine whether the operational purpose of the materiel has been met.
2.2.2 Difference Between Procedures
While both procedures involve some degree of immersion, they differ in that Procedure I (Immersion) primarily addresses leakage during immersion of encased materiel, while Procedure II (Fording) focuses on vehicles traversing a body of water or materiel secured to such vehicles.
2.3 Determine Test Levels and Conditions
Having selected this Method and relevant procedures (based on the materiel's requirements documents and the tailoring process), it is necessary to complete the tailoring process by selecting specific parameter levels and special test conditions/techniques for these procedures based on requirements documents, Life Cycle Environmental Profile (LCEP), and information provided with this procedure. From these sources of information, determine the functions to be performed by the materiel while immersed or following exposure to immersion. Then, determine the depth and duration of immersion anticipated in areas in which the materiel is designed to be employed. To do this, consider the following in light of the operational purpose and life cycle of the materiel.
2.3.1 Identify Climatic Conditions
Identify the appropriate climatic conditions for the geographic areas in which the materiel will be operated and stored, and whether or not test item needs to be operated during the test.
2.3.2 Determine Exposure Conditions
Base the specific test conditions on field data if available. In the absence of field data, determine the test conditions from the applicable requirements documents. If this information is not available, use the following guidance:
2.3.2.1 Test Item Configuration
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 with openings that are normally covered.
MIL-STD-810H
METHOD 512.6
2.3.2.2 Conditioning Temperature
Experience has shown that a temperature differential between the test item and the water can affect the outcome (leakage) of an immersion test. The temperature of the water shall be 18 °C ±10 °C (64 °F ±18 °F). Increasing the test item temperature above the water temperature for the immersion test (Procedure I) usually includes heating of the test item to establish a pressure differential (while cooling) to determine if the seals or gaskets leak under relatively low pressure differential, and to induce expansion/contraction of materials. Although desired, establishing a specific temperature differential for fording tests is often impractical due to the size of the materiel. Also, consider materiel adjacent to heat-producing equipment such as engines, and use temperatures indicative of actual exposure.
- a. Unless otherwise identified, three options are provided for the conditioning of the test item:
- (1) 27 °C (49 °F) above the water temperature - to represent exposure to solar heating immediately prior to immersion.
- (2) 10 °C (18 °F) above the water temperature - to represent a typical temperature difference between materiel and water.
- (3) 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.
- b. Recommend the duration of conditioning immediately prior to immersion be at least two hours to ensure maximum heat loss during immersion and cooling.
2.3.2.3 Depth of Immersion
- a. Complete immersion. For testing the integrity of a test item, use a 1 m covering depth of water or to the required depth as identified in the LCEP or the requirements document (measured from the uppermost surface of the test item to the surface of the water). When testing to depths greater than 1 m within a pressure vessel, it is required to completely immerse the test item in water and then apply the required pressure. The relevant depth/pressure equation follows:
P = 9.8d (fresh water)
P = 10.045d (salt water)
Where:
d = depth of the water in meters
P = pressure in kPa (1 psi = 6.895 kPa).
NOTE: When testing to depths greater than 1 m, within a pressure vessel, the volume of water shall continue to surround the test item throughout the test. The equivalent head of sea water is 0.975 times the head of fresh water for the same pressure difference.
- b. Partial immersion. Where materiel is unlikely to be completely immersed either due to anticipated water depths or to its ability to float, and being unlikely to be restrained, a partial immersion test may be appropriate. In this case, specify depths as being measured from the base of the materiel rather than from the top.
2.3.2.4 Depth of Fording
The fording test may also be used to cover the requirements of STANAG 2805 (paragraph 6.1, reference a), that specifies the following depths.
- a. Shallow fording.
- (1) Tanks and armored cars:
- (a) Light tanks and armored cars – 1 m (39.4 in.).
MIL-STD-810H
METHOD 512.6
- (b) Other tanks (slightly more ground compression) - 1.05 m (41.3 in.).
- (2) Vehicles under 2 ton payload - 0.5 m (19.7 in.).
- (3) Other vehicles - 0.75 m (29.5 in.).
- b. Deep fording. It is essential that all tactical vehicles and guns, either with built-in waterproofing or by the use of waterproofing kits, be able to deep ford six (6) minutes in fresh or salt water to the depths indicated below (the depth to take into account ramp angle as well as wave height):
- (1) Fully enclosed armored vehicles should be able to deep ford to the top of the turret. (Alternatively, these vehicles are to be fitted with flotation equipment.)
- (2) All other prime movers or self propelled guns, except trailed loads, should be able to deep ford 1.5 m (59 in.).
- (3) All trailers or towed guns should be capable of complete immersion. (Alternatively, this materiel should be capable of flotation.)
2.3.2.5 Materiel Fording
Materiel designed to be transported on open vehicles and trailers (such as equipment trailers) should be capable of withstanding partial immersion as anticipated during fording exercises. Examples of fording depths for this type of materiel are as follow:
- a. S-280 shelter: 53 cm (21 inches).
- b. S-250 shelter: 76 cm (30 inches).
2.3.2.6 Duration of Immersion or Exposure
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 (other than as specified in paragraph 2.3.2.2) that may be extended if justified by the anticipated life cycle profile.