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Third LHC Splices Review
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  1. Third LHC Splices Review Review of actions from 2 last reviews • Double shunt on quadrupole bus • Insulation system • Spiders and lyras electrical insulation • DFBA consolidation • Actions covered by TE-MPE • Technical aspects • Management aspects • Other • NB : 33 actions from first review, 15 non-closed ones • 18 actions from second review Third LHC Splice Review

  2. Third LHC Splices Review Double shunt on quadrupole bus Review I: II.3 1) p7/14 : Double shunt on the quadrupole bus The Committee recommends that a double shunt be applied to the quad bus. 2nd Review: The Task Force has not found a satisfactory way to implement this recommendation. We believe that the single shunt can be acceptable if certain other conditions discussed above are met. This cannot be closed until the insulating cover design is complete and shown to provide adequate mechanical constraint, and the other criteria cited in recommendation (n) above. Review II: 1 II.1 p4/11/14 : Criteria for single shunt on quad bus The following criteria must be met, if a single shunt is to be used on the quadrupole bus: - The rebuild criteria presented in Christian Scheuerlein’s talk must be applied rigorously. - The insulating cover must be effective in limiting the deflection and stress on the splice, to prevent the future degradation of the copper stabilizer connection. - The energy extraction time constant must be reduced to ≤ 20 sec. - The shunt must be soldered properly and QC of the shunt must be done correctly. The soldering procedures and QC plans should be presented at the next review. See presentations by F Savary, C Scheuerlein, Knud Dahlerup Petersen, and other ones Third LHC Splice Review

  3. Third LHC Splices Review Consolidated insulation system Review I: II.3 4) p7/14 : Mechanical calculations Make mechanical calculations for the shunt design and the insulating part (3D stress analysis including fatigue and thermal stresses) and document them to support the final design. All the new model calculations need to incorporate shunts in the most severe conditions assumptions (for example no mechanical connections internal to the original splice due to the lack of soldering). 2nd Review: Much of this has been accomplished, but the current model for the insulation box is not fully adequate Review I: II.3 6) p8/14 : Clamping system Continue the development of the design for a clamp that would hold together the shunt and splice in the absence of solder, to help limit the damage during the time of an energy extraction, and implement the chosen design. 2nd Review:Good progress, but design is not yet final Review I: II.4 1) p9/14 : Industrialize manufacturing procedures The Splice Task Force needs to work on improving the manufacturing procedures and the tooling in such a way these are reproducible and not depending on the individuals doing the work. This includes developing adequate QC plans. The review committee recognized the fact that, at this stage of the consolidation programme, this is more important than working out a detailed schedule. 2nd Review:Excellent progress overall, but cannot be completed until the design is complete, particularly of the insulation box Review II: 2 II.1 p4/11 : Insulation cover modelling Review the design and the modelling of the insulation cover to show that it is effective in reducing the mechanical stresses on the splice and shunt, for both dipole and quadrupole connections See presentations by F Savary Third LHC Splice Review

  4. Third LHC Splices Review Actions from second review Review II: 12 II.3.3 p6/11 : Spiders insulation Continue to explore ways to insulate the spider from ground potential and to increase the creep path of the buss to metal support of the spider. Review II: 13 II.3.3 p6/11 : Lyras insulation Continue to explore external methods to insulate the lyras from ground potential. Even if a solution cannot be found for all case where these two electrical insulation problems are in issue it would still be best to repair what is readily accessible. Triggered by: Screening for Defects in the LHC Magnets Electrical Circuits (Mar2010-Jun2011), Final Report, Conclusions and Recommendations [EDMS 1176186] Presented at the Review by H Ten Kate • Working method • The screening person prepares a presentation with supporting documents and raises a list of risk issues he or she thinks are relevant. • The experts group defines (a list of) practical recommendations for the system under study… • A group (TE-MSC-LMF) documents a detailed analysis, design and engineering solution. • CERN management decides to execute or not the engineered solution following the recommendation Third LHC Splice Review

  5. Third LHC Splices Review Actions from second review • The consolidated electrical insulation (H Prin) https://indico.cern.ch/getFile.py/access?contribId=40&sessionId=4&resId=1&materialId=slides&confId=157231 • Presentation of a first concept, only partial and not finalised ? Implementation Heating during welding (~300°C) Friction during cooling Fixation to the flange Behavior during quench Reliability in time Remnant in the cryogenics filters • A lot of work was accomplished (solution, tests,…) Third LHC Splice Review

  6. Third LHC Splices Review Actions from second review Available partial solution H Prin:SMACC Meeting 11.07.2012 [EDMS 1232922] / LHC splices TF 12.09.2012 [EDMS 1241232] Fixation to the insulation box (Stainless Steel) Flange aperture not covered to avoid degradation during welding Rolled sheet of fiber glass impregnated with EPOXY (0.25mm) Third LHC Splice Review

  7. Third LHC Splices Review Actions from second review Available partial Solution implemented on the Q8-Q9 test in Sm18 on both M1 & M3 lines Third LHC Splice Review

  8. Third LHC Splices Review Actions from second review Experience: Spiders: Only one NC [EDMS 831608] The PAQ HV test of the half-cell 23R6 not passed. Short between the main BB M3 ext. and the ground.Resistancemain BB M3 ext. versus ground is 0.3 Ohm (measured at QBQI.22R6) and 5.3 Ohm (measured at QBQI.23R6) • Bellows was cut, insulation reinforced and spider was corrected • A corrective procedure is available and mastered • Was detected during standard ELQA test during assembly, prior to operation • Likely generated by assembly work (surface or interconnection in the tunnel) • This kind of defect (if any) will be detected during the ELQA test during splices consolidation • Present ELQA diagnostics guarantee that there is no such defect in the LHC • QPS diagnostics will likely be improved (amplitude to be defined) Third LHC Splice Review

  9. Third LHC Splices Review Actions from second review Experience: Lyras: [LMC 22.09.2009] After 3 day of cool-down, a short circuit to ground was detected on the MBA.A67 line of the main dipole circuit. After diagnostic, the defect is localized at the level of dipole 3287 at the position A12R6. The warm-up is launched for repair. • Sleeves and bellows were cut and insulation reinforced • Corrective procedure available and mastered • No preventive action recommended (LMC) • Was detected by ELQA monitoring during cool-down, prior to operation • Generated by motion during thermal contraction • This kind of defect (if any) will be detected by the ELQA diagnostics • Present ELQA diagnostics guarantee that there is no such defect in the LHC • QPS diagnostics will likely be improved (amplitude to be defined) Third LHC Splice Review

  10. Third LHC Splices Review Actions from second review Experience: Lyras: Repair procedure Third LHC Splice Review

  11. Third LHC Splices Review Actions from second review INVENTORY OF THE SINGULAR POINTS AND FIRST RISK ASSESSMENT FOR THE LHC 13 KA CIRCUITS [EDMS 1144154: 267 pages] Risk index = (Technical) ( Criticality + Sensibility ) Frequency • Technical : mechanical aspects, cu-cu joint, SC splice, insulation concern [4 to 12] • Criticality : quality of the construction process : Sum of construction difficulty and access difficulty [0 to 5] • Sensibility : consequences of a failure : Sum of failure detectability and failure consequences [0 to 5] • Frequency : Recurrence of each singular point / Total number of Singular Points [X / ≈ 22 500] Singular points are : every splices in the cold mass, lyras, fixed points, diodes connections, …. For the spiders : RI = 6 * (1 + 3) * 0.064 = 1.54 (dipole circuit) 6 * (1 + 3) * 0.032 = 0.768 (quadrupole circuits) For the lyras/sextupole corrector supports : RI = 7 * (3 + 4) * 0.064 = 3.144 Third LHC Splice Review

  12. Third LHC Splices Review Actions from second review Aren’t we contaminated by the lamppost syndrome ? Ex 1. Splices inside the cold masses have a higher risk index Corrective actions for the more critical cases 8 dipoles and 1 SSS replaced Third LHC Splice Review

  13. Third LHC Splices Review Actions from second review Ex 2. BUS BAR – HEAT EXCHANGER CONTACT • No systematic preventive action • Reinforced on cold masses installed during LS1 • A corrective procedure is available and mastered Other cases for which no systematic action is planned because not pragmatically feasible. • The best solution would be to redesign the spiders and other weak components • Not pragmatically feasibleschedule [many months], budget [several MCHF]: in the best cases • Not riskless operations Third LHC Splice Review

  14. Third LHC Splices Review Actions from second review Our approach is to carry out corrective interventions complemented by systematic inspection of new magnets and random partial inspections in the LHC tunnel because: • Corrective procedures are available and mastered • No failure occurred during operation • Diagnostics efficiency for this kind of issue is proven • LHC machine can tolerate one fault to ground per sector • Systematic preventive interventions are not pragmatically feasible and are not riskless • In the unlikely case of failure, the extent of the damages will be limited thanks to finalisation of consolidation measures (Safety relief devices, SSS anchoring to ground) Third LHC Splice Review

  15. Third LHC Splices Review DFBA consolidation Review II: 9 II.3.3 p6/11 : Consolidate DFBA splices Apply shunts to the 13 kA splices in all DFBAs, including the most difficult circuits Repair these joint up to the same standards and based on the same designs as in the magnet to magnet interconnect. Splice repairs should be done by the same crew that repairs the magnet to magnet interconnects. Review II: 10 II.3.3 p6/11 : Initiate design for DFBA splices consolidation Initiate the design for the DFBA splice repair immediately Review II: 11 II.3.3 p6/11 : Study methods to lower risks for specific DFBAs Investigate methods and/or procedures that would lower the risk of repair of the two DFBAs that require re-location to perform the work. See presentation by A Perin Third LHC Splice Review

  16. Third LHC Splices Review Actions covered by TE-MPE Review I: II.7 3) p14/14 : Actual operating voltages Determine the actual operating voltages to judge required hipot levels 2nd Review: In progress, but new hipot voltages have not been formally established. Review I: II.7 4) p14/14 : Proper dump voltages Check documented dump circuit requirements or redo quench calculations to assure dump voltage levels are proper 2nd Review: In progress Review I: II.7 5) p14/14 : Simultaneous hipots of different buses Consider simultaneous hipots of different buses to test bus-to bus withstand capability without going to needlessly high hipot stresses 2nd Review: This technique seems not to have been considered as part of the re-evaluation of hipot voltages. It should still be considered. Review I: II.2 4) p5/14 : Ground current/voltage monitors. Make necessary changes so that ground current monitors are installed on all lower current circuits. These ground current signals should be included in the control system to be logged and to be alarmed when above a pre-set level. The alarm level should be ubstantially below the power supply hardware interlock for high ground current 2nd Review: Closed, Implementing it See presentations by K Dahlerup Petersen & R Schmidt Third LHC Splice Review

  17. Third LHC Splices Review TE-MPE Review I: II.2 3) p5/14 : Hot spot calculations. Include in the integrated system surveys the temperature limits of the various components of each circuit. Perform the calculations to determine the maximum temperatures for the components in the different circuits. Check to see that there is an appropriate margin for the maximum temperature of the circuit components and that the overall risk are balanced between voltage and temperature. 2nd Review: Work in progress. This analysis should be completed, at least for the more critical elements, before LS1 to be able to profit from anything that is learned from the analysis. Review II: 8 II.3.2 p6/11 : IT and MS splices measurement Provide sufficient resources to make splice measurements on the inner triplet and matching section circuits well before the beginning of the long shutdown. Review II: 15 II.3.3 p7/11 : Documentation and modeling Supply the necessary resources to finish the documentation and modelingtasks. The Task Force needs this information and tools to analyze the various electrical systems to better understand potential failure mechanisms and to improve testing of various system See presentations by R Schmidt Third LHC Splice Review

  18. Third LHC Splices Review Technical aspects Review I: II.3 Com2 p6/14 : Document shunt testing The Committee finds results from high current shunt testing between FRESCA and SM18 confusing. Modelling of all test cases should be documented and qualified based on experimental data, and then applied to the shunt design with worst case assumptions. • Report was released on 20.01.2012 • “Electro-thermal and mechanical validation experiment of the consolidation of the LHC 13 kA arc splices” • See presentation by F Lackner & F Savary Third LHC Splice Review

  19. Third LHC Splices Review Technical aspects Review I: II.3 3) p7/14 : Multiple samples to get experience Make multiple samples/trials of critical steps, as part of a qualification plan to be developed, to get a statistically significant basis for assessing the risks of there being any important imperfections in the machine after installation 2nd Review : Have done multiple tests on many variants of the splice repair components. Once the design is completed, a statistically significant number of samples of the final design still need to be tested Review I: II.5 3) p11/14 : Lead containing solder The Splices Task Force should consider the potential hazards for workers associated to the utilization of lead-containing solder, and work with the Safety Commission to plan the work to minimize or eliminate this risk • T Otto’s presentation 2nd Review: Barely begun. This is important, since in the original design of the LHC the use of lead-containing solder was rejected on safety grounds. Review I: II.5 4) p11/14 : Tooling calibration plan A verification and calibration plan for the special tooling should be drawn up and implemented to assure a constant quality of the work throughout the production • Started 2nd Review: Nothing presented at this review. Third LHC Splice Review

  20. Third LHC Splices Review Technical aspects Review I: II.6 2) p12/14 : Optimize tooling and validated on mock-ups The Splices Task Force should draw out a work plan for redesigning and optimizing the various tooling needed for the consolidation activities. These tooling should be validated on the surface simulating as real working conditions as possible (e.g. space constraints) 2nd Review: Good progress. Potential still exists for improvement in some testing fixtures and tooling related to installation of the insulating cover has not been finalized. Review II: 4 II.1 p4/11 : Procedures for training Write detailed manufacturing procedures and QA procedures within the next few months in order to be used for the training of the crews. • Launched Review II: 5 II.1 p4/11 : Procure tools Start procurement of the M-line cutting machines, busbar machining tooling, shunt soldering tooling and main splice tooling now in order to stay on schedule. Review II: 6 II.2.2 p4/11 : Consolidated QC plan, clarify criteria Consolidate the QC plan, in particular on how to implement the plans and procedures and some of the qualification criteria which have not yet been clarified. Third LHC Splice Review

  21. Third LHC Splices Review Management aspects Review I: II.4 2) p9/14 : Workplan, schedule, WBS It is necessary to have a preliminary work plan with its associated schedule and WBS 2nd Review:In progress. No WBS exists yet. See presentations on SMACC Organisation and by K Foraz, M Pojer Review I: II.4 3) p9/14 : Professional scheduler It would be advantageous for the Splice Task Force to work with an experienced/ professional planner/scheduler. The planning needs to be integrated with the planning for other work that will be done in the tunnel during the same shutdown. 2nd Review:This has begun, but most of the work still remains to be done • The Organization, Scheduling and Safety section of EN-MEF was reinforced by M. Bernardini (Work in close collaboration). See also K Foraz’s presentation • R Principe (MSC-LMF) is in charge of the detailed scheduling of the splices consolidation Review I: II.4 4) p9/14 : Contingency and extra resources The planning needs to take account of the possibility of unforeseen developments that will slow down or disrupt the orderly work flow. For example, a larger number of splices than the currently estimated 15% may be required to be remade, or problems with the machining of the copper stabilizer could arise. Include schedule contingency into the baseline and ensure that additional resources are available to able to maintain the schedule. • Enough? 2nd Review: Little progress since last year See presentations on SMACC Organisation Third LHC Splice Review

  22. Third LHC Splices Review Management aspects • Enough? Review I: II.6 1) p12/14 : Alternative scenario with unforeseen issues Study alternate scenarios in view of optimizing the utilization of the critical resources that will certainly be limited (in terms of qualification and experience). Study unforeseen/unexpected scenarios 2nd Review: No evidence that this has started See presentations on SMACC Organisation • Enough? Review II: 3 II.1 p4/11 : Ratio exp/non-exp staff Do not reduce the ratio of experienced staff to contract or other temporary labor below the currently planned level, in order to maintain the required quality of the repairs See presentations on SMACC Organisation Review II: 16 II.4 p7/11 : Update plans, for work QC resources and schedules Update the plans for the work organization, the quality control, the resources and the schedules. Make further updates once the designs are final. • Enough? See presentations on SMACC Organisation Review II: 17 II.4 p7/11 : Resources loaded schedule for the preparation phase Prepare a detailed resource-loaded schedule of the work that remains to prepare for the shutdown. This needs be developed within the next month to be an effective planning tool. Not formally but through SMACC project and TF structures Third LHC Splice Review

  23. Third LHC Splices Review Other Review I: II.6 2) p12/14 : Risk analysis CERN should insure that enough resources are allocated to ensure that the risk assessment and subsequent risk analysis can be executed on the planned time scale 2nd Review: Excellent work was done on the screening exercise, but it is important that the recommendations that result be implemented. It should be the goal to complete the critical ones before LS1 To be revisited by the splices TF Review II: 7 II.2.3 p5/11 : CSCM to be considered for periodic requalification Consider the utility and practicality of utilizing the CSCM for periodic “requalification” tests of the main quadrupole bus circuit. See dedicated session (H Thiesen) Review II: 14 II.3.3 p6/11 : Diode joint resistance Continue working on determining the root cause of the measured increase in diode mechanical joint resistance See next presentation by F Savary Third LHC Splice Review

  24. Third LHC Splices Review Conclusion ? Review II: II.4 p7/11 : Address the recommendations that remain open from the previous review before the next review. This presentation in particular and more generally this review Third LHC Splice Review