Student meeting 08.07.2013 MTTF calculations for the BLEDP card

Vegard Joa Moseng BI - BL

Student meeting 08.07.2013

MTTF calculations for the BLEDP card

From «THE NEW BLM SYSTEM FOR THE INJECTOR COMPLEX» BI Day 2012

The card:

From «Acquisition Crate Design» 26 August 2011 – William Viganò

Card overview:

MTTF: The value is for the entire BLEDP card which

includes 2x Circuit Breakers, 8x Input Monitors and 8x ADC circuits.

Failure rate: 1.108E-05 MTTF in hours: 9.024E+04 MTTF in years: ~10.3 years

Note: The value is a combination of a military

handbook and supplier given failure rates. The handbook is 20 years old, and so given

the expectation that quality and reliability on generic components are higher today, the value should be viewed as very conservative.

The supplier given failure rates are significantly lower than the military handbook and for the most part, much more complicated. A confidence level of 90% has been selected as often as possible.

The failure rate takes into account that all failures, in every way, will cause there to be a full stop. This is not the case, and so the actual number of failures that will cause full stops are expected to be lower.

Reliability analysis

Statistics: 325 different Prediction blocks – components with

a different set of parameters. 4477 different parameters have been evaluated. 1375 parameters are affecting the failure rate. BLEDP card

block overview

Comments

The overall failure rate is a total of the weighted average where all the components are included as stand alone system blocks, using the so called part count method. Because the method used gives a conservative failure rate, and because the failure rate doesn’t take into account failure modes that are not critical, the overall Mean Time To Failure estimate of 10.3 years is probably higher.