1. Cryogenics Fault Tree A. Niemi & E. Rogova

2. Contents 1.Introduction of the current tree structure 2.Failure rates observed in 2015 failure data 3.Unsure classifications in failure data Objective: Ensure 1.Sensible structure of the tree 2.Completeness of failure classifications

3. Cryogenics Unavailability at the Top Level CRYO-PRI: Primary failures within cryogenics systems CRYO-SEC: Failures in system operating environment i.e. users of cryo-cooling and systems that cryogenics depends on CRYO-MAINT: Planned maintenance

4. CRYO-MAINT CRYO-MAINT-PM: Scheduled preventive maintenance CRYO-MAINT-DCM: Delayed corrective maintenance Fault that does not require instant repair and can be repaired e.g. during technical stop or other planned time

5. CRYO-SEC Failures in CRYO operating environment CRYO-SEC-USER (user related) CRYO-SEC-UTI (Utility related) CRYO-SEC-SEU (Single event upset)

6. CRYO-SEC-USER Includes failures in cryogenics users (and user related systems) that cause cryogenics unavailability CRYO-USER-MAGNET CRYO-USER-CL (Current Leads) CRYO-USER-BSCR (Beam Screens) CRYO-USER-RF CRYO-USER-QPS

7. CRYO-SEC-UTI Failures in utilities that cryogenics depends on CRYO-UTI-CV (Cooling and Ventilation) CRYO-UTI-EL (Electricity) CRYO-UTI-CAIR (Compressed Air) CRYO-UTI-IVAC (Insulation vacuum) Is this correct? CRYO-UTI-NET (Network)

8. CRYO-PRI Failures within Cryogenics system and its operations and maintenance CRYO-PRI-OP (Human factors in operations causing downtime) CRYO-MAINT-FAULT (Failure during maintenance task causing additional downtime)

9. CRYO-PRI-PNO Process not optimized: contains factors that are not failures of equipment but non optimization of operating procedures that causes downtime CRYO-PNO-DFB: Distribution Feed Box level oscillation CRYO-PNO-BSCR: Beam Screen (temperature) Regulation CRYO-PNO-REF: Example situation missing

10. CRYO-PRI-CO Cryogenic specific control failures CRYO-CO-SW Control software failures CRYO-CO-PLC Prog. Logic Controller failure CRYO-CO-FEC Front End Computer CRYO-CO-FB Field Bus

11. CRYO-PRI-EQUIP CRYO-EQUIP-DIST = Cryogenics cooling distribution in sectors CRYO-EQUIP-REF = Regenerators: CRYO-REF-4.5K CRYO-REF-1.8K

12. CRYO-REF-4.5K CRYO-4.5K-ROT: Rotating machines CRYO-4.5K-VALVE CRYO-4.5K-EH: Electrical heating CRYO-4.5K-PASSIV: Passive equipment Filters, Absorbers, Coalescers, Oil separators, pipes etc. CRYO-4.5K-INST: Instrumentation

13. CRYO-4.5K-ROT CRYO-4.5K-WARMC: Warm compressors CRYO-4.5K-TURB: Turbines CRYO-4.5K-OILP: Oil pumps CRYO-4.5K-VACP: Vacuum pumps

14. CRYO-REF-1.8K Similar structure to CRYO-REF-4.5K tree Different naming 4.5K = 1.8K The CRYO-1.8K-ROT has a node CRYO-1.8K-CC = cold compressor CRYO-REF-1.8K is dependent on CRYO-REF-4.5K

15. CRYO-DIST Structure is similar to 4.5K and 1.8K Different naming 1.8K, 4.5K = DIST CRYO-DIST has no rotating machinery, so CRYO-DIST-ROT node does not exist CRYO-DIST is dependent on CRYO-REF-1.8K

16. 2015 Fault Data Name Number of occurrences CRYO-PNO 110 CRYO-USER-QUENCH 25 CRYO-DIST-INST 17 CRYO-PRI-OP 8 CRYO-1.8K-CC (Communications Card)5 CRYO-CO-PLC 5 CRYO-UTI-EL 5 CRYO-MAINT-DCM4 CRYO-MAINT-FAULT4 CRYO-UTI-CV 3 CRYO-CONTROLS-SW 2 CRYO-1.8K-CC1 CRYO-4.5K-INST1 CRYO-4.5K-OILP 1 CRYO-4.5K-VALVE 1 CRYO-DIST-EH 1 CRYO-DIST-VALVE 1 NOTE numbers are not checked by experts! IMO The CRYO-PNO modes hard to distinguish, as cause is system wide Also, difference between USER-BSCR and CRYO-PNO is not solid Should cryogenics be able to take the heat load is does the user generate too much heat CRYO-USER-QUENCH is better than QPS, Magnet and UFO quenches. As from cryogenics point of view it is irrelevant what caused the quench. The system boundaries in controls are not clear: e.g. cables between systems