MIL STD 810 G – Test Method 507.5 – Humidity
The purpose of this method is to determine the resistance of materiel to the effects of a warm, humid atmosphere.
This method applies to materiel that is likely to be stored or deployed in a warm, humid environment, an environment in which high levels of humidity occur, or to provide an indication of potential problems associated with humidity. Although it is preferable to test materiel at appropriate natural environment sites, it is not always practical because of logistical, cost, or schedule considerations. Warm, humid conditions can occur year-round in tropical areas, seasonally in mid-latitude areas, and in materiel subjected to combinations of changes in pressure, temperature, and relative humidity. Often materiel enclosed in non-operating vehicles in warm, humid areas can experience high internal temperature and humidity conditions. Other high levels of humidity can exist worldwide. Further information on high temperatures and humidity is provided in AR 70-38 (paragraph 6.1, reference a), MIL-HDBK-310 (paragraph 6.1, reference b), or NATO STANAG 4370, AECTP 200, Category 230, Section 2311 (paragraph 6.1, reference c). See also Part Three of this document.
This method may not reproduce all of the humidity effects associated with the natural environment such as long-term effects, nor with low humidity situations. This method does not attempt to duplicate the complex temperature/humidity environment but, rather, it provides a generally stressful situation that is intended to reveal potential problem areas in materiel. This method includes natural and induced temperature/humidity cycles (for guidance purposes) for identified climatic categories, but these cycles cannot replicate naturally-occurring environments. Testing in the natural environment, whenever practical, may provide more valuable results. Specifically, this method does not address:
Condensation resulting from changes of pressure and temperature for airborne or ground materiel.
Condensation resulting from black-body radiation (e.g., night sky effects).
Synergistic effects of solar radiation, humidity, or condensation combined with biological and chemical contaminants.
Liquid water trapped within materiel or packages and retained for significant periods.
This method is not intended for evaluating the internal elements of a hermetically sealed assembly since such materiel is air-tight.
Procedure I – Storage & Transit Cycles (Cycles B4 or B5), and Natural (Cycles B1, B2, or B3)
Step 1. With the test item in the chamber, ensure it is in its storage and/or transit configuration, adjust the chamber temperature to 23 ± 2°C (73 ± 4°F) and 50 ± 5 percent RH, and maintain for no less than 24 hours.
Step 2. Adjust the chamber temperature and relative humidity to those shown in the appropriate induced (storage and transit) category of Table 507.5-I for time 0000.
Step 3. Unless other guidance is provided by the test plan, cycle the chamber air temperature and RH with time as shown in the appropriate storage and transit cycle of Table 507.5-I (or in the appropriate approximated curve from Figures 507.5-1, 507.5-2, or 507.5-3) through the 24-hour cycle, and for the number of cycles indicated in Table 507.5-II for the appropriate climatic category.
Step 4. Adjust the chamber temperature to 23 ± 2°C (73 ± 4°F) and 50 ± 5 percent RH, and maintain until the test item has reached temperature stabilization (generally not more than 24-hours).
Step 5. If only a storage and/or transit test is required, go to Step 15.
Step 6. Conduct a complete visual checkout of the test item and document the results.
Step 7. Put the test item in its normal operating configuration.
Step 8. Conduct a complete operational checkout of the test item and document the results. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure. Otherwise, go to Step 9.
Step 9. Compare these data with the pretest data.
Step 10. Adjust the test item configuration to that required for naturally occurring temperature humidity cycles (B1, B2, or B3).
Step 11. Adjust the chamber conditions to those given in Table 507.5-I for the time 0000 of the specified cycle.
Step 12. Perform 24-hour cycles for the number of cycles indicated in Table 507.5-II for the appropriate climatic category with the time-temperature-humidity values specified in Table 507.5-I, or the appropriate approximated curve of Figures 507.5-3 through 507.5-5.
Step 13. If the materiel (test item) could be functioning non-stop in the natural environment, operate the test item continuously throughout the test procedure. If shorter operational periods are identified in the requirements document(s), operate the test item at least once every five cycles, and during the last cycle, for a duration necessary to verify proper operation. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure.
Step 14. Adjust the chamber temperature to 23 ± 2°C (73 + 4°F) and 50 ± 5 percent RH, and maintain until the test item has reached temperature stabilization (generally not more than 24-hours).
Step 15. Conduct a complete visual examination of the test item and document the results.
Step 16. Conduct an operational checkout of the test item in accordance with the approved test plan, and document the results. See paragraph 5 for analysis of results.
Step 17. Compare these data with the pretest data.
Procedure II – Aggravated
This test consists of a 24-hour conditioning period (to ensure all items at any intended climatic test location will start with the same conditions), followed by a series of 24-hour temperature and humidity cycles for a minimum of 10 cycles, or a greater number as otherwise specified in the test plan, unless premature facility or test item problems arise.
Step 1. With the test item installed in the test chamber in its required configuration, adjust the temperature to 23 ± 2°C (73 + 4°F) and 50 ± 5 percent RH, and maintain for no less than 24 hours.
Step 2. Adjust the chamber temperature to 30°C (86°F) and the RH to 95 percent.
Step 3. Expose the test item(s) to at least ten 24-hour cycles ranging from 30-60ºC (86-140°F) (Figure 507.5-6) or as otherwise determined in paragraph 2.2.1. Unless otherwise specified in the test plan, conduct a test item operational check (for the minimum time required to verify performance) near the end of the fifth and tenth cycles during the periods shown in Figure 507.5-6, and document the results. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure. Otherwise, continue with Step 4.
NOTE: If the operational check requires the chamber to be open or the test item to be removed from the chamber, and the check cannot be completed within 30 minutes, in order to prevent unrealistic drying, recondition the test item at 30°C and 95 percent RH for one hour, and then continue the checkout. Extend the test time for that cycle by one hour. Continue this sequence until the checkout has been completed. If the operational check is conducted in the chamber, and extends beyond the 4-hour period noted in Figure 507.5-7, do not proceed to the next cycle until the checkout is completed. Once the check has been completed resume the test.
Step 4. At the completion of 10 or more successful cycles, adjust the temperature and humidity to 23 ±2°C (73 + 4°F) and 50 ± 5 percent RH, and maintain until the test item has reached temperature stabilization (generally not more than 24-hours).
Step 5. Perform a thorough visual examination of the test item, and document any conditions resulting from test exposure.
Step 6. Conduct a complete operational checkout of the test item and document the results. See paragraph 5 for analysis of results.
Step 7. Compare these data with the pretest data.
NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.