Warranty Returns Improve Product Reliability

In the SEL product hospital, a root cause analysis of failure is performed on every returned device. If the customer-observed failure cannot be repeated, the relay electronics are replaced with new components and shipped to the customer so that tests can continue to be performed on the defective components. These tests may involve environmental testing equipment such as SEL’s Highly Accelerated Life Test (HALT) chamber and vibration table.
HALT testing is performed on returned products to evaluate the effect of environmental impacts on product reliability. The testing performed in the HALT chamber is also used to ensure proper operation and a long life for SEL products in harsh station environments. With the widest rated temperature range in the industry, SEL products will operate in ambient temperatures from -40º to +85ºC. Years of operational temperature cycling can be simulated in a matter of weeks.
The information derived from examination of all returned units is used to constantly improve product quality. The observed Mean Time Between Failure (MTBF) for SEL products has risen from 68 years in 1989 to over 300 years today. This means that on the average, for every 300 SEL devices in service, one may experience a failure in any given year. This is observed data, not calculated or estimated based on component counts.

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