Beam Interlock System Dependability Study RSWG – 31 st January 2005

Beam Interlock System Strategy 2 of 12 On the Agenda… 1. Failure Mode, Effect and Criticality Analysis -Background 3. Conclusions -How things look so far 2. Performing the FMECA -Beam Interlock System User Box Only

Beam Interlock System Strategy 3 of 12 FMECA Failure Modes, Effects and Criticality Analysis In what way can something go wrong?… …when it does go wrong, what happens to the system?… …and just how much of a problem does this cause?

Beam Interlock System Strategy 4 of 12 How is it done? FMECA starts at the Component Level of a system get subsystem schematics, component list, and understand what it does Break a large system into blocks, defining smaller, manageable sub-systems get MTBF of each component on the list, derive P FAIL (mission) derive failure modes and failure mode ratios for each component explain the effect of each failure mode on both the subsystem and system determine the probability of each failure mode happening. Draw conclusions! MIL-STD-1629 FMD-97 MIL-HDBK-338 MIL-HDBK-217

Beam Interlock System Strategy 5 of 12 Applying the Method to the CIBU 1. Failure Mode, Effect and Criticality Analysis -Background 3. Conclusions -How things look so far 2. Performing the FMECA -Beam Interlock System User Box Only

Beam Interlock System Strategy 6 of 12 Block Diagram Subsystem: CIBU System: Beam Interlock

Beam Interlock System Strategy 7 of 12 Applying the Methodology 1/2 MIL-HDBK-217F or manufacturer FMD-97 MIL-HDBK-338 Bill of Materials

Beam Interlock System Strategy 8 of 12 Applying the Methodology 2/2 Designer Knowledge MIL-HDBK-338 Schematic multiply through

Beam Interlock System Strategy 9 of 12 So… What’s the Next Step 1. Failure Mode, Effect and Criticality Analysis -Background 3. Conclusions -How things look so far 2. Performing the FMECA -Beam Interlock System User Box Only

Beam Interlock System Strategy 10 of 12 Conclusion 75 Simultaneous Beam Dump CIBU 39 Independant Beam Dump CIBU 10 Hour LHC mission 400 Missions per year During one year it’s probable that for all CIBUs 2-3 will fail in one way or another 0-1 will fail without having any impact on the system 0-1 will fail during a mission causing a Beam Dump, and requesting Maintenance 1-2 will fail only requesting Maintenance at the end of the current mission 3.00E-02 is Probability of a single channel failing blind 1.47E-08 is Probability of a both channels failing blind in the same CIBU SIL 3

Beam Interlock System Strategy 11 of 12 And another thing ●It’s very tedious calculating a FMECA like this – Bottom up, means you have to look through lists of components – It’s easy to make mistakes – It’s all based on a lot of assumptions, and speculation ●Maintainability – From the FMECA it’s relatively simple to derive the Maintainability of the system… Just have to calculate the repair times… – On my list of things to do

Beam Interlock System Strategy 12 of 12 FIN