507.6-44 test process

4.1.1 General Description

The required apparatus consists of a chamber or cabinet, and auxiliary instrumentation capable of maintaining and monitoring (see Part One, paragraph 5.18) the required conditions of temperature and relative humidity throughout an envelope of air surrounding the test item. (See Part One, paragraph 5.)

4.1.2 Facility Design

Unless otherwise specified, use a test chamber or cabinet with a test volume and the accessories contained therein constructed and arranged in such a manner as to prevent condensate from dripping on the test item. Vent the test volume to the atmosphere to prevent the buildup of total pressure and prevent contamination from entering.

4.1.3 Test Sensors and Measurements

Determine the relative humidity by employing either solid state sensors whose calibration is not affected by water condensation, or by an equivalent method such as fast-reacting wet-bulb/dry-bulb sensors or dew point indicators. Sensors that are sensitive to condensation, such as the lithium chloride type, are not recommended for tests with high relative humidity levels. A data collection system, including an appropriate recording device(s), separate from the chamber controllers is necessary to measure test volume conditions. If charts are used, use charts readable to

MIL-STD-810H

METHOD 507.6

within ±0.6 °C (±1 °F). If the wet-wick control method is approved for use, clean the wet bulb and tank and install a new wick before each test and at least every 30 days. Ensure the wick is as thin as realistically possible to facilitate evaporation (approximately 1/16 in. thick) consistent with maintaining a wet surface around the sensor. Use water in wet-wick systems that is of the same quality as that used to produce the humidity (see Part One, paragraph 5.16). When physically possible, visually examine the water bottle, wick, sensor, and other components making up relative humidity measuring systems at least once every 24 hours during the test to ensure they are functioning as desired.

4.1.4 Air Velocity

Use an air velocity flowing across the wet bulb sensor of not less than 4.6 meters/second (900 feet/minute, or as otherwise specified in sensor response data), and ensure the wet wick is on the suction side of the fan to eliminate the effect of fan heat. Maintain the flow of air anywhere within the envelope of air surrounding the test item between 0.5 and 1.7 meters/second (98 to 335 feet/minute).

4.1.5 Humidity Generation

Use steam or water injection to create the relative humidity within the envelope of air surrounding the test item. Use water as described in Part One, paragraph 5.16. Verify its quality at periodic intervals (not to exceed 15 days) to ensure its acceptability. If water injection is used to humidify the envelope of air, temperature-condition it before its injection to prevent upset of the test conditions, and do not inject it directly into the test section. From the test volume, drain and discard any condensate developed within the chamber during the test so as to not reuse the water.

4.1.6 Contamination Prevention

Do not bring any material other than water into physical contact with the test item(s) that could cause the test item(s) to deteriorate or otherwise affect the test results. Do not introduce any rust or corrosive contaminants or any material other than water into the chamber test volume. Achieve dehumidification, humidification, heating and cooling of the air envelope surrounding the test item by methods that do not change the chemical composition of the air, water, or water vapor within that volume of air.

4.3.1 Interruption Due to Chamber Malfunction

• a. General. See Part One, paragraph 5.11, of this Standard.
• b. Specific to this Method.
• (1) Undertest interruption. If an unscheduled interruption occurs that causes the test conditions to fall below allowable limits, the test must be reinitiated at the end of the last successfully completed cycle.
• (2) Overtest interruptions. If the test item(s) is exposed to test conditions that exceed allowable limits, conduct an appropriate physical examination of the test item and perform an operational check (when practical) before testing is resumed. This is especially true where a safety condition could exist, such as with munitions. If a safety condition is discovered, the preferable course of action is to terminate the test and reinitiate testing with a new test item. If this is not done and test item failure occurs during the remainder of the test, the test results may be considered invalid. If no problem has been encountered during the operational checkout or the visual inspection, reestablish pre-interruption

MIL-STD-810H

METHOD 507.6

conditions and continue from the point where the test tolerances were exceeded. See paragraph 4.3.2 for test item operational failure guidance.

4.3.2 Interruption Due to Test Item Operation Failure

Failure of the test item(s) to function as required during operational checks presents a situation with several possible options.

• a. The preferable option is to replace the test item with a “new” one and restart from Step 1.
• b. A second option is to replace / repair the failed or non-functioning component or assembly with one that functions as intended, and restart the entire test from Step 1.

NOTE: When evaluating failure interruptions, consider prior testing on the same test item and consequences of such.

4.4.1 Preparation for Test

4.4.1.1 Test Setup

• a. General. See Part One, paragraph 5.8.
• b. Unique to this Method. Verify that environmental monitoring and measurement sensors are of an appropriate type and properly located to obtain the required test data.

4.4.1.2 Preliminary Steps

Before starting the test, determine the test details (e.g., procedure variations, test item configuration, cycles, durations, parameter levels for storage/operation, etc.) from the test plan.

4.4.1.3 Pretest Checkout

All items require a pretest checkout at standard ambient conditions to provide baseline data. Conduct the checkout as follows:

• Step 1. Install appropriate instrumentation, e.g., thermocouples, in or on the test item.
• Step 2. Install the test item into the test chamber and prepare the test item in its storage and/or transit configuration in accordance with Part One, paragraph 5.8.1.
• Step 3. Conduct a thorough visual examination of the test item to look for conditions that could compromise subsequent test results.

Step 4. Document any significant results.

• Step 5. Conduct an operational checkout (if appropriate) in accordance with the test plan, and record results.
• Step 6. If the test item operates satisfactorily, proceed to the appropriate test procedure. If not, resolve the problems and repeat Step 5 above.

4.4.2 Test Procedures

4.4.2.1 Procedure I - Storage and Transit Cycles (Cycles B2 or B3), 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 ± 3.6 °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 507.6-I for time 2400.

MIL-STD-810H

METHOD 507.6

• 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 507.6-I (or in the appropriate approximated curve from Figures 507.6-1, 507.6-2, or 507.6-3) through the 24-hour cycle, and for the number of cycles indicated in Table 507.6-II for the appropriate climatic category.
• Step 4. Adjust the chamber temperature to 23 ± 2 °C (73 ± 3.6 °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 507.6-I for the time 2400 of the specified cycle.
• Step 12. Perform 24-hour cycles for the number of cycles indicated in Table 507.6-II for the appropriate climatic category with the time-temperature-humidity values specified in Table 507.6-I, or the appropriate approximated curve of Figures 507.6-4 through 507.6-6.
• 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 the 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 ± 3.6 °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.

4.4.2.2 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 ± 3.6 °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 30-60 °C (86-140 °F) (Figure 507.6-7) 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 507.6-7, and

MIL-STD-810H

METHOD 507.6

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 ±2 °C (86°F ± 4 °F) 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 507.6-7, 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 ± 3.6 °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.