4.1 Test Facility
- a. The required apparatus consists of a chamber or cabinet together with auxiliary instrumentation capable of maintaining and monitoring the required conditions of high temperature (and humidity, where required) throughout an envelope of air surrounding the test item(s) (see Part One, paragraph 5.18).
- b. Unless 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).
- c. Continuously record chamber conditions and, if required, test item temperatures.
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)) or chamber air temperature, re-stabilize the test item at the required temperature before continuing the test. For Procedure II, if the operational check is not completed within 15 minutes, reestablish test item temperature/RH conditions before continuing.
- b. Rate of temperature change. Unless otherwise specified or documented in the LCEP, use a rate of temperature change not exceeding 3 °C (5 °F) per minute to prevent thermal shock.
- c. Temperature measurement. Install temperature sensor instrumentation on or in the test item to measure temperature stabilization data (see Part One, paragraph 5.4).
- d. Data recording. Record chamber temperature (and humidity if controlled) in accordance with Part One, paragraphs 5.2 and 5.18, and at a sufficient rate to satisfy the 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 required or optional performance checks.
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.
- (a) Cycling. If a cyclic high temperature test is being conducted and an unscheduled interruption occurs that causes the test conditions to fall out of allowable tolerances toward standard ambient temperatures, continue the test from the end of the last successfully-completed cycle.
- (b) Steady state. If a steady state (non-cyclic) test is being conducted (only for items near constant-heat-producing sources), and an unscheduled interruption occurs that causes the test conditions to fall out of allowable tolerances toward standard ambient conditions, re-stabilize the test item at the required test temperature and continue the test from the point where test conditions were interrupted.
- (2) Overtest interruption (e.g., loss of chamber control).
- (a) Inspection and performance check. If an interruption in a cyclic or steady state test results in more extreme exposure of the test item than required by the materiel specifications, follow the interruption by a complete physical inspection and an operational check (where possible) before continuing the test.
- (b) Safety, performance, materials problems. When these types of problems are discovered after an overtest, the preferable course of action is to terminate the test and re-initiate testing with a new test item. If this is not done and a test item failure occurs during the remainder of the test, the test
MIL-STD-810H
METHOD 501.7
results could be considered invalid because of the overtest conditions. If no problem has been encountered, reestablish pre-interruption conditions and continue from the point where the test tolerances were exceeded.
4.3.2 Interruption Due to Test Item Operation Failure
Failure of the test item(s) to function as required during mandatory or optional performance checks during testing 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 interruption, consider prior testing on the same test item and consequences of such.
4.4 Test Setup
- a. General. See Part One, paragraph 5.8.
- b. Unique to this Method. Include in the test setup any additional heat sources or an appropriate simulation (see paragraph 2.3.2b).
4.5 Test Execution
The following steps, alone or in combination, provide the basis for collecting necessary information concerning the materiel in a high temperature environment.
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.). (See paragraph 3.1, above.)
4.5.1.2 Pretest Standard Ambient Checkout
All test items require a pretest standard ambient checkout to provide baseline data. Conduct the checkout as follows:
- Step 1 Conduct a visual examination of the test item with special attention to stress areas, such as corners of molded cases, and document the results.
- Step 2 In order to determine thermal response (paragraph 3.1c), install temperature sensors in, on, or around the test item as described in the test plan.
- Step 3 Conduct an operational checkout (Part One, paragraph 5.8.2) at standard ambient conditions (Part One, paragraph 5.1) as described in the plan and record the results.
- Step 4 If the test item operates satisfactorily, proceed to paragraph 4.5.2, 4.5.3, or 4.5.4 as appropriate. If not, resolve the problems and repeat Step 3 above. 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
NOTE: If the LCEP has defined the need to operate the test item at the high operational temperature immediately following storage, consider using Procedure III.
Step 1 Place the test item in its storage configuration and install it in the chamber.
- Step 2 Adjust the chamber environment to the required test conditions, either cyclic exposure (Tables 501.7-II or 501.7-III) or constant exposure (see paragraph 2.3.3.1), for the start of the test period at a rate not to exceed 3 °C/min (5 °F/min). Maintain for the specified time following temperature stabilization of the test item.
MIL-STD-810H
METHOD 501.7
Step 3 a. For cyclic storage, expose the test item to the temperature (and humidity, if applicable) conditions of the storage cycle for a minimum of seven continuous 24-hour cycles, or as specified in the LCEP and the test plan. Record the thermal response of the test item.
b. For constant temperature storage (to be used only for items situated in close proximity to equipment producing constant high temperatures; see paragraph 2.3.2b(2)), maintain the test temperature at least two hours following test item temperature stabilization (see Part One, paragraph 5.4). The additional two hours will help ensure unmeasured internal components actually reach stabilization. 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 At the completion of the constant temperature soak or the last cycle, adjust the chamber air temperature to standard ambient conditions and maintain until the test item temperature is stabilized.
Step 5 Conduct a visual examination and operational checkout of the test item, and record the results for comparison with pretest data. See paragraph 5 for analysis of results.
4.5.3 Procedure II - Operation
| Step 1 | With the test item in the chamber in its operational configuration, install any additional temperature sensors necessary to measure the maximum temperature response of the test item, ensuring the functioning components are included. |
| Step 2 | If performing the constant temperature exposure, go to Step 3. For cycling temperature exposure, go to Step 8. |
| Step 3 | Constant temperature exposure. Adjust the chamber air conditions to the required temperature (and humidity, if applicable) at which the materiel must operate at rate not to exceed 3 °C/min (5 °F/min). |
| Step 4 | Maintain the chamber conditions at least two hours following test item temperature stabilization (see Part One, paragraph 5.4). If not possible to instrument internal components, base the additional soak time on thermal analysis or previously measured data to ensure temperature stabilization throughout the test item. |
| Step 5 | Conduct as thorough a visual examination of the test item as possible considering chamber access limitations, and document the results for comparison with pretest data. |
| Step 6 | Operate the test item and allow its temperature to re-stabilize. Conduct an operational checkout of the test item in accordance with the test plan and document the results for comparison with pretest data. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure. |
| Step 7 | Skip Steps 8 through 10 and proceed directly to Step 11. |
| Step 8 | Cycling temperature exposure. Adjust the chamber air temperature (and humidity, if applicable) to the initial conditions, of the operational cycle appropriate for materiel deployment, at a rate not to exceed 3 °C/min (5 °F/min). Maintain until the test item's temperature has stabilized. |
| Step 9 | Expose the test item to at least three cycles or the number of cycles necessary to assure repeated test item response. Document the maximum test item response temperature. Conduct as complete a visual examination of the test item as possible considering chamber access limitations. Document the results. |
| Step 10 | Operate the test item during the maximum test item temperature response period of the exposure cycle. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure. The maximum test item temperature response period may not coincide with the maximum temperature cycle conditions because of the thermal lag of the test item. Repeat until a successful operational checkout of the test item has been accomplished in accordance with the approved test plan, and the results have been documented. |
| Step 11 | With the test item not operating, adjust the chamber air temperature to standard ambient conditions and maintain until the test item temperature has stabilized. |
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METHOD 501.7
Step 12 Conduct a complete visual examination and operational checkout in accordance with the approved test plan and document the results for comparison with pretest data. See paragraph 5 for analysis of results.
4.5.4 Procedure III - Tactical-Standby to Operational
- Step 1 With the test item in the chamber and in its tactical configuration, install any additional temperature sensors necessary to measure the temperature response of the test item, ensuring the functioning components are included.
- Step 2 Adjust the chamber air temperature to the anticipated maximum non-operating temperature, and maintain this temperature until the test item temperature has stabilized, plus a minimum of two additional hours to ensure complete stabilization.
Step 3 Adjust the chamber air temperature to the high operational temperature identified in the LCEP as quickly as possible (at a rate no less than 2 °C (3.6 °F) per-minute). As soon as the chamber instrumentation indicates this temperature has been reached, operate the test item in accordance with the approved test plan and document the results for comparison with pretest data. If the test item fails to operate as intended, follow the guidance in paragraph 4.3.2 for test item failure. If identified in the LCEP that the item will be subjected to multiple exposures of this environment, repeat Steps 2 and 3 as required by the test plan.
- Step 4 With the test item not operating, adjust the chamber air temperature to standard ambient conditions and maintain until the test item temperature has stabilized.
- Step 5 Conduct a complete visual examination and operational checkout in accordance with the approved test plan, and document the results for comparison with pretest data. See paragraph 5 for analysis of results.