Experience: past events and accidents Andrzej Siemko SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 First accident during pioneering time of the experimental test bench “TB1” Year Accident Type Reason Action/Lesson learnt Comment 1996 Discharge of large quantity of GHe through the rupture disc to the hall. Operation Operator error. Safety PLC strapped to gain the operation time and then …forgotten. Since this accident strapping of any safety device is strictly forbidden. Accident on the first experimental bench. This type of accident never appeared again. MFB emergency discharge system performed well. SM 18 LHC Magnet test safety review - 2005

HV Breakdown Accident in Signal Feedthrough Box of MBP2N1 on “TB3” Year Accident Type Reason Action/Lesson learnt Comment 1999 HV breakdown during a quench among quench heater leads in the signal feedthrough box. Electrical. Signal feedthrough box design deficiency and capillary tightness defect/deficiency. Rearrangement of the cable and connector distribution. Introduction of the feedthrough box air vent. Accident on the first prototype bench and prototype magnet. This type of accident never appeared again. Magnet and test station electronics severely suffered. SM 18 LHC Magnet test safety review - 2005

HV Breakdown Accident in Signal Feedthrough Box of MBP2N1 on “TB3” SM 18 LHC Magnet test safety review - 2005

HV Breakdown Accident in Signal Feedthrough Box of MBP2N1 on “TB3” SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Loss of insulation vacuum on prototype test bench “TB3” – test of MBP2A2 Year Accident Type Reason Action/Lesson learnt Comment 2000 Loss of insulation vacuum. Foreign LN/air burnt an operator hand. Cryogenics. Sequence of events. 2MW Transformer defect (explosion). Wrong functioning of the vacuum valve in safety position. Equipment rescue action under unconsciousness of the risk. Since this accident dedicated, PLC driven, GHe flow in ACR’s introduced. Loss of insulation vacuum appeared in the future several times but without LN/air production. SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Loss of the capillary tightness in the MBP2O1 prototype tested on the test bench “TB3” Year Accident Type Reason Action/Lesson learnt Comment 2000 Loss of the capillary tightness during a quench. Discharge of significant quantity of GHe through the the signal feedthrough box to the hall. Cryogenics. Capillary tightness defect and design deficiency. Complete redesign of this element for future magnets. Accident on the first prototype bench and prototype magnet. This type of accident appeared once more again. SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Loss of the capillary tightness in the MBP2O1 prototype tested on the test bench “TB3” SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Loss of the capillary tightness in the MBP2O1 prototype tested on the test bench “TB3” SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Quench Heater PS Energy Discharge in the Signal Interconnection Box on “TB4” Year Accident Type Reason Action/Lesson learnt Comment 2001 Energy of the quench heater power supplies discharged in one of the connector of the interconnection box. Electrical. Operation. Magnet “last minute” redesign. Operator error. Operation by unauthorized person. Boxes interlocked on the prototype benches and later redesigned and improved on the series benches. Test procedures reinforced. Accident on the prototype bench and one of the modified prototype magnets. This type of accident never appeared again. SM 18 LHC Magnet test safety review - 2005

Noell 3004 incident on “TB4” (TB A1) Year Accident Type Reason Action/Lesson learnt Comment 2002 Noell 3004 magnet suffered from an inter-turn short circuit, which appeared during a quench at nominal current. Excessive heat deposited in the short-circuited turn caused a meltdown of the cable and then of the cold bore. Electrical. Operation. Magnet defect in form of the inter-turn short. Precursor wrongly interpreted and neglected. Audit in all three magnet manufacturers. Test procedures reinforced. Relevant alarms on precursors introduced in Automatic Quench Analysis. Accident on the prototype bench and preseries magnet. Magnet damaged. Significant damage to the test equipment. This type of accident can not be excluded in the future. SM 18 LHC Magnet test safety review - 2005

Noell 3004 incident on “TB4” (TB A1) Temperature below –50 C SM 18 LHC Magnet test safety review - 2005

13kA Water Cooled Cable Leak Incident on RM.E (TB E) Year Accident Type Reason Action/Lesson learnt Comment 2004 Water flood into the RM.E and RM.B power converters and surrounding area. Electrical. Bad workmanship of the cable extremity installation. Revision and correction of all suspected cables by cable manufacturer. Accident on the series test bench during its initial operation period. No damage to the test equipment. SM 18 LHC Magnet test safety review - 2005

13kA Water Cooled Cable Leak Incident on RM.B (TB B) Year Accident Type Reason Action/Lesson learnt Comment 2004 Water flood into the RM.B power converter and surrounding area. Electrical. Material defect. Replacement of bad cable by cable manufacturer. Accident on the series test bench during its initial operation period. No damage to the test equipment. SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Conclusion Testing of superconducting magnets in operational conditions is not risk free! In practice all major accidents/incident happened on preseries test benches and prototype/preseries magnets. Significant effort and resources were invested in the design and construction of the series test benches regarding the safety aspects. SM 18 LHC Magnet test safety review - 2005

SM 18 LHC Magnet test safety review - 2005 Conclusion Except two accidents with water leaks in 13kA cables, which appeared at early stage of the operation of the new test benches, all series dipoles and quadrupoles tested on the series test benches were up to now tested without significant safety problems. This good result do not release responsible people from further analysis of their systems/activities and actions if required. SM 18 LHC Magnet test safety review - 2005