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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Brandon
Date posted: Thu May 8 4:09:30 US/Eastern 2003
Subject: Can HASS replace ESS??
Message:
Hi, I wonder whether HASS can replace ESS? Under what condition(s) we cannot apply HASS? Also, is there any restriction in carrying out HASS? Can HASS be carried out for SRUs? Thank you.


Reply:

Subject: HASS VS ESS
Reply Posted by: BWD (bdudley@alionscience.com )
Organization: RAC
Date Posted: Mon May 12 12:49:24 US/Eastern 2003
Message:
The simple answer is, HASS "Highly Accelerated Stress Screening" can take the place of ESS "Environmental Stress Screening". The limiting factor for the HASS testing is the fact that you MUST perform a HALT test, "Highly Accelerated Life Test", to determine the destruction limits of the product, then determine a "generous margin" between destruction limits and the HASS stress levels. ESS always uses lower stress levels that are within the product operating limits, so ESS testing does not have this overstress potential problem. Of course, this means that the test for ESS will tend to be longer. As for the last question, HASS testing can be applied to shop replaceable units provided that HALT tests have been performed to determine the destruction limits.


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