High Temperature | Alta temperatura

MIL STD 810 G – Test Method 501.5 – High Temperature

 

SCOPE

 

Purpose
Use high temperature tests to obtain data to help evaluate effects of high temperature conditions on materiel safety, integrity, and performance.
Application
Use this method to evaluate materiel likely to be deployed in areas where temperatures (ambient or induced) are higher than standard ambient.
Limitations
Limit use of this method to evaluating the effects of relatively short-term (months, as opposed to years), even distributions of heat throughout the test item. This method is not generally practical for:
  1. Evaluating time-dependent performance degradation (aging) effects that occur during constant long-term exposure to high temperatures (under storage or operational modes) where synergetic effects may be involved. For such high temperature aging effects, test in the natural environment.
  2. Evaluating materiel in a high temperature environment where solar radiation produces significant thermal gradients in the materiel. For simulating direct solar impingement, use Method 505.5, Procedure I.
  3. Evaluating actinic (photochemical) effects (use Method 505.5, Procedure II).
  4. Evaluating the effects of aerodynamic heating.
  5. Although high temperature testing may be considered for assessment of munitions, accomplish safety or hazard testing in accordance with MIL-STD-2105C (paragraph 6.1, reference 6.1d).

 

TEST PROCESS

 

Procedure I – Storage
  • 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 for either cyclic exposure (Tables 501.5-II or 501.5-III) or constant exposure (see paragraph 2.3.3.1) for the start of the test period and maintain for the specified time following temperature stabilization of the test item.
  • Step 3:
  1. For cyclic storage, expose the test item to the temperature (and humidity, if applicable) conditions of the storage cycle for a minimum of seven 24-hour cycles, or as specified in the LCEP and the test plan. Record the thermal response of the test item.
  2. 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 controlled 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.
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. Otherwise, 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.
  • 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 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, and 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 controlled ambient conditions and maintain until the test item temperature has stabilized.
  • 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.
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 3.6oF 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..
  • Step 4. With the test item not operating, adjust the chamber air temperature to controlled 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.

 

NOTE: Tailoring is essential. Please, ask to your confidence laboratory for further details about tailoring of test methods.

 

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