4.1 Test Facility
- a. 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 low temperature throughout an envelope of air surrounding the test item.
- b. Unless otherwise justified by the materiel platform environment and to prevent unrealistic heat transfer in the materiel, maintain the air velocity in the vicinity of the test item so as to not exceed 1.7 m/s (335 ft/min).
4.2 Controls
- a. Temperature. Unless otherwise specified in the test plan, if any action other than test item operation (such as opening the chamber door) results in a significant change of the test item temperature (more than 2 °C (3.6 °F)), restabilize the test item at the required temperature before continuing. If the operational check is not completed within 15 minutes, reestablish the test item temperature conditions before continuing.
- b. Rate of temperature change. Unless otherwise specified, control the rate of temperature change to not exceed 3 °C (5 °F) per minute to prevent thermal shock.
- c. Temperature measurement. Install temperature sensor(s) on or in the test item to measure temperature stabilization data (see Part One, paragraph 5.4).
- d. Temperature recording. Record chamber temperature at a sufficient rate to capture data necessary for post-test analysis (see Part One, paragraph 5.18).
4.3 Test Interruption
Test interruptions can result from two or more situations, one being from failure or malfunction of test chambers or associated test laboratory equipment. The second type of test interruption results from failure or malfunction of the test item itself during operational checks.
MIL-STD-810H
METHOD 502.7
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. Follow an interruption that allows test temperatures to fluctuate outside allowable tolerances toward ambient conditions by a complete physical inspection and operational check (where possible). If no problems are encountered, restabilize the test item at the test temperature and continue from the point of the interruption. Since no extreme conditions were encountered, consider any problems as a test item failure.
- (2) Overtest interruption. Follow any interruption (loss of chamber control) that results in more extreme exposure of the test item than required by the materiel specification by a complete physical examination and operational check (where possible) before any continuation of testing. This is especially true where a safety problem could exist, such as with munitions. If a problem 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 could be considered invalid because of the overtest condition. If no problem has been encountered, reestablish pre-interruption 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 of the pretest requirements.
- b. A second option is to replace / repair the failed or non-functioning component or assembly within the test item with one that functions as intended, and restart the entire test from Step 1 of the pretest requirements.
NOTE: When evaluating failure interruptions, consider prior testing on the same test item, and consequences of such.
4.4 Test Setup
- a. See Part One, paragraph 5.8.
- b. Unique to this Method. There is no guidance unique to this Method.
4.5 Test Execution
The following steps, alone or in combination, provide the basis for collecting necessary information concerning the test item in a low temperature environment. Conduct pretest and post test operational checkouts after storage and after manipulation to verify successful completion of both procedures.
4.5.1 Preparation for Test
4.5.1.1 Preliminary Steps
Before starting the test, review pretest information in the test plan to determine test details (e.g., procedures, test item configuration, cycles, durations, parameter levels for storage/operation, etc.).
4.5.1.2 Pretest Standard Ambient Checkout
All test items require a pretest standard checkout at standard ambient conditions to provide baseline data. Conduct the checkout as follows (change of step sequence may be required for large test items):
Step 1 Conduct a complete visual examination of the test item, with special attention to stress areas such as corners of molded cases, and document the results.
MIL-STD-810H
METHOD 502.7
Step 2 Install temperature sensors in or on the test item as required to determine the test item temperature(s). If not possible to instrument internal components, base any additional soak time on thermal analysis to ensure temperature stabilization throughout the test item.
Step 3 Conduct an operational checkout at standard ambient conditions (See Part One, paragraph 5.1), and in accordance with the approved test plan and record the results.
Step 4 If the test item operates satisfactorily; proceed to the first test procedure as determined from the test plan. If not, resolve the problems and repeat Steps 3 and 4. If resolution requires replacement of the item or removal of sensors in order to repair, then repeat Steps 1 through 3 above.
4.5.2 Procedure I - Storage
Step 1 Place the test item in its storage configuration and install it in the test chamber.
Step 2 Adjust the chamber air temperature to that specified in the test plan for storage at a rate not to exceed 3 °C/min (5 °F/min).
Step 3 Stabilize the test item at the storage temperature (Part One, paragraph 5.4) and maintain for the duration as specified in the test plan. If not possible to instrument internal components, base any additional soak time on thermal analysis to ensure temperature stabilization throughout the test item.
Step 4 Conduct a visual examination of the test item and compare the results with the pretest data. Record any pertinent physical changes or the fact that there were no obvious changes.
Step 5 Adjust the chamber air temperature to standard ambient conditions (at a rate not to exceed 3 °C/min (5 °F/min)), and maintain it until the test item has achieved temperature stabilization.
Step 6 Conduct a complete visual examination of the test item and document the results.
Step 7 If appropriate, conduct an operational checkout of the test item and document the results. See paragraph 5 for analysis of results.
Step 8 Compare these data with the pretest data.
4.5.3 Procedure II - Operation
Step 1 With the test item in its operational configuration and installed in the test chamber, adjust the chamber air temperature to the low operating temperature of the test item as specified in the test plan at a rate not to exceed 3°C/min (5°F/min). Maintain this for at least two hours following temperature stabilization of the test item. If not possible to instrument internal components, base any additional soak time on thermal analysis to ensure temperature stabilization throughout the test item.
Step 2 Conduct as complete a visual examination of the test item as chamber access limitations will allow, and document the results.
Step 3 Conduct an operational checkout of the test item and record results for comparison with data obtained in paragraph 4.5.1.2. If the test item fails to operate as intended, see paragraph 5 for analysis of results, and follow the guidance in paragraph 4.3.2 for test item failure.
Step 4 If manipulation of the test item is required at low temperature; proceed to Step 2 of paragraph 4.5.4. If not, proceed to Step 5 of this procedure.
- Step 5 Adjust the chamber air temperature to standard ambient conditions at a rate not to exceed 3 °C/min (5 °F/min), and maintain it until temperature stabilization of the test item has been achieved.
Step 6 Conduct a complete visual examination of the test item, and document the results.
- Step 7 If appropriate; conduct an operational checkout and record results for comparison with data obtained in paragraph 4.5.1.2. If the test item fails to operate as intended, see paragraph 5 for analysis of results, and follow the guidance in paragraph 4.3.2 for test item failure.
MIL-STD-810H
METHOD 502.7
4.5.4 Procedure III - Manipulation
- Step 1 With the test item in the test chamber and in its storage configuration, adjust the chamber air temperature to the low operating temperature of the test item as determined from the test plan at a rate not to exceed 3°C/min (5°F/min). Maintain it for two hours following temperature stabilization of the test item.
- Step 2 While maintaining the low operating temperature, place the test item in its normal operating configuration. Based on the type of test chamber available, select one of the two following options:
- Option 1 - To be used when a "walk-in" type chamber is available: With personnel clothed and equipped as they would be in a low temperature tactical situation, disassemble the test item as would be done in the field, and repack it in its normal shipping/storage container(s), transit case, or other mode and configuration.
- Option 2 - To be used when small chambers (non-walk-in) are used: Perform the option 1 procedure, except the disassembly and packing will be performed by personnel reaching through chamber access holes or the open door while they are wearing heavy gloves such as would be required in the natural environment.
NOTE: Opening of the chamber door may cause frost to form on the test item in addition to a gradual warming of the test item. Limit manipulation necessary to perform the required setup or teardown to 15-minute intervals, between which reestablish the temperature of Step 1 above.
- Step 3 Reestablish the temperature to that used in Step 1, above and maintain it for two hours following temperature stabilization of the test item.
- Step 4 If operation of the test item is required at low temperatures; proceed to Step 1 of paragraph 4.5.3. If not, proceed to Step 5 of this procedure.
- Step 5 Conduct a complete visual examination of the test item, and document the results for comparison with the pretest data.
- Step 6 Adjust the chamber air temperature to standard ambient conditions (at a rate not to exceed 3 °C/min (5 °F/min)), and maintain it until the test item has reached temperature stabilization.
- Step 7 Conduct a complete visual examination of the test item, and document the results.
- Step 8 If appropriate; conduct an operational checkout of the test item and record results for comparison with data obtained in paragraph 4.5.1.2. If the test item fails to operate as intended, see paragraph 5 for analysis of results, and follow the guidance in paragraph 4.3.2 for test item failure.