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SMACC local splice quality control

Learn about ELQC procedures, R-8 test precision, reliability, and quality control of splices produced before LS1. Compare results from 2009 and 2013, assess visual controls, and planned modifications for LS1 production.

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SMACC local splice quality control

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  1. SMACC local splice quality control • S. Heck, C. Scheuerlein, M. Solfaroli, P. Thonet • ELQC tests performed by BE-OP team led by M. Solfaroli • LabVIEW data acquisition software by O. Andreassen, EN-ICE-MTA

  2. Outline • ELQC procedures • R-8 test precision and reliability • ELQC of splices produced before LS1 • Comparison of R-8 results obtained in 2009 and 2013 for identical splices • Visual control of cables; diagnostics for assessing the quality of potentially overheated cables • R-8 of splices produced during LS1 • R-8 after busbar machining • Planned modification of the ELQC sequence for LS1 production splices • R-top-side of consolidated splices • R-8 of consolidated splices • ELQC of DFBA splices • Control of the quality documentation of consolidated diodes • ELQC of US welds • Conclusion C. Scheuerlein, 4th Splice Review, 23 July 2013

  3. ELQC Procedures • LHC-QBBI-TP-0002 v.1.0 Visual Inspection and Geometrical Test of the US Welded Line N Splices- Released • LHC-QBBI-TP-0003 v.2.0 Visual Inspection and Geometrical Test of the US Welded Auxiliary Busbar Splices in Lines M1 and M2 - Released • LHC-QBBI-TP-0004 v.1.0 Quality Control of the LHC Main Interconnection Splices Produced during LS1 (Before Application of Shunts) - Released • LHC-QBBI-TP-0005 v.1.0 Quality Control of the Stabilised LHC Main Busbar Cables before Splice Assembly- Released • LHC-QBBI-TP-0006 v.1.0 Quality Control of the LHC Main Interconnection Splices Produced before LS1 (before Application of Shunts) - Released • LHC-QBBI-TP-0007 v.1.0 Quality Control of the LHC Main Interconnection Splices after Consolidation by Application of Shunts- Released • LHC-QBBI-TP-0008 v.2.0 Visual Inspection of the Insulation Box of the Consolidated LHC Main Interconnection Splices during LS1 - Released • LHC-QBBI-TP-0009 v.1.0 Quality Control of the LHC Main Interconnection Splices after Busbar Machining- Released • LHC-QBBI-TP-0011 v.0.2 Control of the QC Documents for the Bolted LHC Quadrupole Diode Splices after Consolidation- Released • LHC-QBBI-TP-0012 v.1.0 Quality Control of the LHC Main Interconnection Short-Circuit Splices - Released • LHC-QBBI-TP-0013 v.1.0 Keywords for Opening Non-Conformity Reports by the ELQC Team during LS1- Released • LHC-DFBA-TP-0001 v.1.0 Quality Control of the Main Interconnection Splices in the LHC Distribution Feed Boxes before Consolidation- Released • LHC-DFBA-TP-0002 v.1.0 Quality Control of the Main Interconnection Splices in the LHC Arc Electrical Feed Boxes after Consolidation- Released C. Scheuerlein, 4th Splice Review, 23 July 2013

  4. Reliability of the R-8 test • The DLRO10X Digital Low Resistance Ohmmeters areregularly tested using calibration resistors. • With the LabVIEW data acquisition software operators can verify themselves if the R-8 test was successful: • by verifying the standard deviation of the three measurements from which the average value is calculated (STDEV must be <0.8 µΩ). • by comparing the sum of both R-8 results and R-16 (accepted range 2.5 µΩ > R-8Left+R-8Right–R-16 > -0.5 µΩ) Resistance measurement of a standard resistor with the DLRO10X. Histogram ΣR-8 minus R-16 for old splice (all) and consolidated splices in sector 56(updated 21.06.2013). C. Scheuerlein, 4th Splice Review, 23 July 2013

  5. Precision of the R-8 test • The precision of the R-8 test has been assessed by statistical analysis of consolidated splices: • M1,M2consolidated: µ=8.99 μΩ, σ=0.38 μΩ(n=2036) • M3consolidated: µ=5.39 μΩ, σ= 0.29 μΩ(n=1070) • The precision of the R-8 test is ±0.4 µΩ and ±0.3 µΩ (±σ) or better for quadrupole and dipole splices, respectively. Histogram of all R-8 results for consolidated M3 splices (n=1070, µ =5.4 µΩ, σ=0.29 µΩ). C. Scheuerlein, 4th Splice Review, 23 July 2013

  6. ELQC of splices produced before LS1 • The ELQC team must detect all splices that are not safe at nominal LHC operating conditions, as well as the splices which cannot be consolidated as is. • In particular ELQC tests must assure that: • R-8 is not too high (R-8excess<5 µΩ) • That a flat surface for shunt installation can be produced by removing less than a 1.5 mm-thick Cu layer. • That the insulation box can be mounted. C. Scheuerlein, 4th Splice Review, 23 July 2013

  7. Typical geometrical splice defects QBBI.B17R5-M1-Int local height gauge does not fit QQBI.13R5-M3 global gauge does not fit M3 busbar stabiliser nose is too strongly bent to machine a flat surface C. Scheuerlein, 4th Splice Review, 23 July 2013

  8. R-8 summary for splices produced before LS1 • There are significantly less splices with R-8excess>5 µΩ in sector 5/6 (2.7%) than in sector 6/7 (7.1%). • One M1 splice with extremely high R-8 of 116 µΩ was found in 7/8. • Most defects for M1 and M3 splices are located on the so-called “Left” side (Lyra side), which is probably due to the asymmetry of the tooling used for splice assembly and heating. C. Scheuerlein, 4th Splice Review, 23 July 2013

  9. The maximum R-8 detected so far • R-8 of quadrupole splice QQBI.20L8 M1-Ext-Left is 116 µΩ, corresponding with an insulated cable length of about 9 cm (NCR https://edms.cern.ch/document/1300043/1 ). • As can be seen from so-called R-transversal resistance maps, the cable is insulated inside the busbar stabiliser of SSS 011: • Along the wedge R-transversal=0.67±0.11 µΩ (R-transversal max is 0.83 µΩ). • The maximum R-transversal on the left side of the wedge is 98 µΩ. R-transversal resistance mapping to localise where the busbar cable is insulated. C. Scheuerlein, 4th Splice Review, 23 July 2013

  10. Comparison of R-8 results obtained in 2009 and 2013 for identical splices • So far for 63 splices R-8 has been measured in 2009 and in 2013. • The maximum difference ΔR-8 is 3.4 µΩ. This difference is possibly due to measurement uncertainties. • R-8M3-2009=5.81±0.34 µΩ; R-8M3-2013=5.85±0.41 µΩ; n=76 • R-8M1,M2-2009=9.57±0.72 µΩ; R-8M1,M2-2013=9.93±1.06 µΩ; n=50 ΔR-8 (R-82013 minus R-82009) histogram C. Scheuerlein, 4th Splice Review, 23 July 2013

  11. ELQC of disconnected cables • All cables of disconnected splices are controlled by the ELQC team after cable pre-tinning. • The goal of the visual cable inspection is to detect all cable defects that would cause a significant additional 1.9 K splice resistance. • So far all cables controlled could be re-connected as is, apart from one pair of cables in a 1.9 K resistance outlier segment. • The splices of the remaining 1.9 K outlier segments will be controlled before splice opening, in order to detect possible signs of overheating. C. Scheuerlein, 4th Splice Review, 23 July 2013

  12. Overheated cables • One pair of cables has been found severely damaged, presumably during LHC installation (NCR https://edms.cern.ch/document/1290623/1). • There are obvious signs of a strong busbar and cable overheating. • It is likely that the cable is not in contact with the busbar stabiliser over a long length. • The splice QBBI.A21L6-M2-Int is part of a 1.9 K outlier segment (about 2 nΩ excess). All splices of this segment have been opened. No signs of overheating have been observed in the other splices. C. Scheuerlein, 4th Splice Review, 23 July 2013

  13. Diagnostics for assessing cable damage • The cable damage caused by overheating can be assessed by magnetisation measurements of strand samples extracted at different positions of the potentially defective cable. • After excessive heating, the reduction of critical current density is accompanied by a degradation of the mechanical properties (the cable becomes brittle). • Excessive heating makes the cable unsolderable. Variation of the Nb-Ti strand magnetization (ΔM) at 4.2 K in magnetic field up to 6 T after heat treatment to different peak temperatures (duration always 5 minutes) (a) and relative flux pinning reduction vs. annealing temperature at different magnetic field (b). Nb-Ti/Cu strand elongation at fracture vs. peak temperature From “Temperature induced degradation of Nb-Ti/Cu composite superconductors”, Journal of Physics: Conference Series 234 (2010) 022031 C. Scheuerlein, 4th Splice Review, 23 July 2013

  14. Magnetisation measurement results • Strand samples have been extracted at the cable extremities and in the cable center. • Magnetisation measurements courtesy of David Richter, TE-MSC-SCD. • Magnetisation results show that both cables are degraded over the entire length and cannot be reconnected as is. • Least, but still important degradation is observed at the busbar ends. • Repair method is under definition, not yet validated. • Repairs of overheated cables may be particularly difficult at the connection side, and in extreme cases could require replacement of a magnet. Comparison of the variation of magnetic moment in magnetic field up to 5 Tesla of strand samples extracted from QBBI.A21L6-M2-Int cables and reference strands. C. Scheuerlein, 4th Splice Review, 23 July 2013

  15. QBBI.B33R4-M3-Ext splice control • Splice is in a segment with additional 1.9 K resistance of 0.85 nΩ. • No signs of overheating on busbars and cables of QQBI.33R4-QBQI.33R4-QBBI.B33R4-M3-Ext. • R-transversal resistance mapping results along QBBI.B33R4-M3-Ext are 0.4 µΩ higher as normal almost over the entire splice length (see NCR https://edms.cern.ch/document/1287651/1 ). QBBI.B33R4-M3-Ext and Int before disconnection Resistance maps along different M3 splices may indicate a poor intercable contact in splice QBBI.B33R4-M3-Ext. Courtesy F. Mueller. C. Scheuerlein, 4th Splice Review, 23 July 2013

  16. QBBI.B33R4-M3-Ext cables control • Both cables are ductile, and there are no obvious signs of overheating. • Magnetisation measurements of extracted strand samples confirm that the cables are not strongly degraded. • The visual cable surface aspect may indicate that after splice de-soldering the cable surfaces are more oxidised than usual. C. Scheuerlein, 4th Splice Review, 23 July 2013

  17. ELQC of splices produced during LS1 • No major problems detected. • R-8 statistics (updated 18.06.2013): M1 Splices • R-8M1-Right=9.58±0.54µΩ (n=126, R-8M1-Right-max=11.2 µΩ, R-8M1-Right-min=8.4 µΩ) • R-8M1-Left=9.61±0.52 µΩ (n=126, R-8M1-Left-max=12.2 µΩ, R-8M1-Left-min=7.9 µΩ) M2 Splices • R-8M2-Right=9.45±0.47µΩ (n=50, R-8M2-Right-max=11.2 µΩ, R-8M2-Right-min=8.2 µΩ) • R-8M2-Left=9.66±0.57 µΩ (n=50, R-8M2-Left-max=12.2 µΩ, R-8M2-Left-min=9.0 µΩ) M3 Splices • R-8M3-Right=5.76±0.25 µΩ (n=69, R-8M3-Right-max=6.5 µΩ, R-8M3-Right-min=4.9 µΩ) • R-8M3-Left=5.84±0.35 µΩ (n=69, R-8M3-Left-max=7.5 µΩ, R-8M3-Left-min=5.1 µΩ) • 2009 production for comparison [i]: • R-8M1,M2= 9.51±0.74 μΩ • R-8M3=5.69±0.30 µΩ [i] S. Heck, C. Scheuerlein, “Statistical analysis of LHC main interconnection splices room temperature resistance (R-8) results”, CERN-ATS-Note-2012-076 TECH C. Scheuerlein, 4th Splice Review, 23 July 2013

  18. ELQC of machined splices • No major geometrical problems detected after busbar machining. • The average ΔR-8 increase after machining is as expected, considering that M1 and M3 splices are in most cases more deformed on the “Left” side. ΔR-8 (R-8 after machining minus R-8 before machining; updated 19.06.2013): • Δ R-8M1-Right=0.18±0.52 µΩ (n=302, Δ R-8 max=1.8 µΩ, Δ R-8 min=-2.0 µΩ) • Δ R-8M1-Left=0.50±0.60 µΩ (n=301, Δ R-8 max=3.3 µΩ, Δ R-8 min=-2.0 µΩ) • ΔR-8M2-Right=0.34±0.63 µΩ (n=298, Δ R-8 max=3.4 µΩ, Δ R-8 min=-2.1 µΩ) • Δ R-8M2-Left=0.24±0.66 µΩ (n=298, Δ R-8 max=2.8 µΩ, Δ R-8 min=-2.1 µΩ) • ΔR-8M3-Right=0.07±0.55 µΩ (n=319, Δ R-8 max=2.0 µΩ, Δ R-8 min=-3.0 µΩ) • Δ R-8M3-Left=0.18±0.53 µΩ (n=319, Δ R-8 max=1.9 µΩ, Δ R-8 min=-1.6 µΩ) . • Only in few cases a R-8 increase indicated a splice degradation due to busbar machining. The strongest R-8 increase observed so far is from 14.0 µΩ to 20.0 µΩ (this case is not yet included in the statistics shown above). • The vast majority of splices which R-8 resistance is below the R-8 excess acceptance criterion of 5 µΩ appears to be mechanically strong enough to prevent splice breakage during machining. C. Scheuerlein, 4th Splice Review, 23 July 2013

  19. Planned modification of the ELQC sequence for LS1 production splices • The ELQC step after busbar machining, which was initially considered to be done only in the first sector, will be performed systematically for all splices until the end of LS1. • The LS1 production splices are of comparable quality as the 2009 production splices. So far only two LS1 production splice needed to be redone, one because of too high R-8, and one because a geometrical defect. Both defects would have been detected after busbar machining as well. • At this point the ELQC step of LS1 production splices before busbar machining does not add a significant value anymore. • Therefore, at the SMACC-QA meeting of the 18.7.2013 it was decided to stop the ELQC step of LS1 production splices. It is planned to change the ELQC sequence in Wish accordingly from the 1st of August 2013. • This will free 1 FTE of the ELQC team, which helps to concentrate on the crucial ELQC tasks, and in particular to keep the systematic ELQC step of all splices after busbar machining until the end of LS1. • The procedure LHC-QBBI-TP-0004 v.1.0 for the control of LS1 production splices remains operational and can be re-applied again at any moment if this is needed. C. Scheuerlein, 4th Splice Review, 23 July 2013

  20. ELQC of consolidated splices:Example of a real R-top-side outlier From “Splices local Quality Control”, First LHC Splice Review, October 18, 2010 http://indico.cern.ch/conferenceDisplay.py?confId=109100 C. Scheuerlein, 4th Splice Review, 23 July 2013

  21. R-top-side statistics • Shunts are of good quality, as seen by visual, geometrical and R-top-side tests. • Five R-top-side measurements are performed on each shunt. In average, R-top-side M1,M2 values exceed R-top-side M3 by 0.25 µΩ (1.29 µΩ vs. 1.04 µΩ). • R-top-side acceptance threshold values: • Single R-top-side values must not exceed 2.2 µΩ and 2.4 µΩ for dipole and quad shunts, respectively. • The average of the 5 values must not exceed Ø R-top-side=1.7 µΩ and 1.9 µΩ for dipole and quad shunts, respectively. Ø R-top-side for all shunts controlled before the 10.6.2013 (for M1,M2 n=103, for M3 n=116)

  22. R-top-side individual measurements summary (updated 17.6.2013) • In few cases R-top-side slightly exceeded the acceptance threshold value, but no real outlier has been detected so far. • Average R-top-sideM1,M2=1.29±0.20 µΩ (n=4700). • All shunts for which R-top-side exceeds the acceptance threshold value are systematically retested before requesting a repair. C. Scheuerlein, 4th Splice Review, 23 July 2013

  23. ΔR-8 after consolidation (updated 20.6.2013) • ΔR-8=R-8 after consolidation minus R-8 after machining • ΔR-8M1-Right=-1.05±0.55 µΩ (n=256, ΔR-8M1-Right-max=0.63 µΩ, ΔR-8M1-Right-min=-3.00 µΩ) • ΔR-8M1-Left=-1.47±0.72 µΩ (n=256, ΔR-8M1-Left-max=0.23 µΩ, ΔR-8M1-Left-min=-4.87 µΩ) • ΔR-8M2-Right=-1.28±0.72 µΩ (n=258, ΔR-8M2-Right-max=0.70 µΩ, ΔR-8M2-Right-min=-5.13 µΩ) • ΔR-8M2-Left=-1.15±0.62 µΩ (n=258, ΔR-8M2-Left-max=0.87 µΩ, ΔR-8M2-Left-min=-4.87 µΩ) • ΔR-8M3-Right=-0.75±0.43 µΩ (n=277, ΔR-8M3-Right-max=0.53 µΩ, ΔR-8M3-Right-min=-2.90 µΩ) • ΔR-8M3-Left=-0.93±0.59 µΩ (n=277, ΔR-8M3-Left-max=0.17 µΩ, ΔR-8M3-Left-min=-3.67 µΩ) • The calculated R-8 decrease due to the additional splice cross section (45 mm2 or 90 mm2 over 50 mm length) is -1.35 µΩ and -0.80 µΩ for quadrupole and dipole splices,respectively. C. Scheuerlein, 4th Splice Review, 23 July 2013

  24. R-8 distribution of quadrupole splices before and after consolidation (updated 17.7.2013) C. Scheuerlein, 4th Splice Review, 23 July 2013

  25. R-8 distribution of dipole splices before and after consolidation (updated 17.7.2013) C. Scheuerlein, 4th Splice Review, 23 July 2013

  26. ELQC of DFBA splices • ELQC of DFBA splices is followed up by S. Heck. • All DFBA splices are controlled before and after consolidation. • Two DFBAJ pigtail splices have been strongly bent so that the 21 mm-wide gauge did not fit ( NCR https://edms.cern.ch/document/1295854/1 ). • Repair is needed before a smooth surface for shunting can be machined. C. Scheuerlein, 4th Splice Review, 23 July 2013

  27. DFBAK SHM-HCM splice damage during Cu machining Damaged splice No. 1 • During the machining operation on the IC closest to the LHC arc, quadrupole splices No. 1 and No. 4 were damaged. • R-8 of the damaged splices was increased by about 2.5 µΩ with respect to the R-8 measured before machining. Damaged splice No. 4 Splices 1 and 4 after repair C. Scheuerlein, 4th Splice Review, 23 July 2013

  28. ELQC of consolidated diode splices • The quality of the consolidated quadrupole diode splices is assured by various tests performed by the LMF team. • The ELQC team does not perform additional measurements and controls. Instead the ELQC of the consolidated diodes is based on the verification of photos and test results provided by the LMF team. • Only the consolidated busbar splice resistance results will be verified by the ELQC team (but not the internal diode resistances). • A too high room temperature resistance of the bolted splices may indicate a poor assembly and/or too low torque of the connecting screws. It is not possible to conclude on the 1.9 K resistance of bolted splices. • The room temperature resistance threshold values for Ni plated and Ag plated diode busbar splices are 1.5 µΩ and 1.0 µΩ, respectively. C. Scheuerlein, 4th Splice Review, 23 July 2013

  29. Verifications of the diode photos provided by LMF team • On the photos the ELQC team verifies: • Correct diode busbar assembly • Presence of Ag plated connection plates • Presence of screws with counter plates • Shims welded to diode housing • Insulation well positioned Photos, courtesy L. Grand-Clement. C. Scheuerlein, 4th Splice Review, 23 July 2013

  30. ELQC of US welds • ELQC of US welds is followed up by P. Thonet. • ELQC team performs visual and geometrical control of US welds produced during LS1. • Regular production and characterisation of test loops and witness samples are under the responsibility of the SIT team. • The width of the gauge used to verify the correct line M US weld alignment was changed from 3.1 mm to 3.4 mm, following an increase of the US weld compression to 0.8 mm. • ELQC of US welds produced before LS1 are not controlled by the ELQC team. • Exceptionally special US welds of round to rectangular wires in sector 7/8 are controlled if they are accessible. US welds with misaligned strands in QBQI.30R7 C. Scheuerlein, 4th Splice Review, 23 July 2013

  31. Conclusions • The precision of the LS1 R-8 test is ±0.4 µΩ and ±0.3 µΩ (±σ) or better for quadrupole and dipole splices, respectively. • The quality of LS1 production splices is comparable to that of splices produced in 2009. • No strong R-8 variations for identical splices measured in 2009 and 2013. • In some cases a relatively strong R-8 increase indicated a splice degradation during busbar machining. The ELQC test after busbar machining for all splices will be continued during entire LS1. • For LS1 production splices the ELQC after busbar machining is sufficient to detect non-conform splices, and the ELQC step of LS1 production splices before machining will be stopped, in order to focus on the critical ELQC steps, and in particular on the ELQC after busbar machining. • After application of shunts the average R-8 is reduced as expected, taking into account the additional Cu cross section. No real R-top-side outlier has been detected so far. • Cable defects in 1.9 K resistance outlier segments may require some complicated repairs, and in the worst case could require a magnet replacement. C. Scheuerlein, 4th Splice Review, 23 July 2013

  32. Back-up slides

  33. R-8 measurement uncertainties • R-8 measurements are performed with a Digital Low Resistance Ohmmeter (Avo DUCTER DLROX 10) using the 4-point method, with a test current of 10 A and a resolution of 0.1 µΩ. • The accuracy of the DLROX 10 stated by the manufacturer is ±0.2 µΩ. • The inhomogeneous current distribution due to the point like current injection close to the voltage taps causes a systematic error in the R-8 results of approximately +10%. • The estimated temperature variation in the LHC tunnel is between 14 °C to 20 °C. This causes a maximum uncertainty in the R-8 results of 0.21 µΩ and 0.12 µΩ for quadrupole and dipole splices, respectively. • The influence of the splice temperature on R-8 is neglected. C. Scheuerlein, 4th Splice Review, 23 July 2013

  34. R-8 distribution of M1 splices produced before LS1 in sectors 5/6 and 6/7 • All histograms from S. Heck, updated the 17.07.2013. Sector 6/7 (ELQC completed)n=832 67× R-8excess>5 μΩ (8.1%)R-8max=41.7 μΩ Sector 5/6 (ELQC completed) n=722 9× R-8excess>5 μΩ (1.2 %) R-8max=30.4 μΩ C. Scheuerlein, 4th Splice Review, 23 July 2013

  35. R-8 distribution of M2 splices produced before LS1 in sectors 5/6 and 6/7 Sector 6/7 (ELQC completed) n=834 40× R-8excess>5 μΩ (4.8%) R-8max=39.2 μΩ Sector 5/6 (ELQC completed) n=724 5× R-8excess>5 μΩ (0.7%) R-8max=27.7 μΩ C. Scheuerlein, 4th Splice Review, 23 July 2013

  36. R-8 distribution of M3 splices produced before LS1 in sectors 5/6 and 6/7 Sector 6/7 (ELQC completed) n=836 71× R-8excess>5 μΩ (8.5%) R-8max=40.6 μΩ Sector 5/6 (ELQC completed) n=764 16× R-8excess>5 μΩ (2.1%) R-8max=34.2 μΩ C. Scheuerlein, 4th Splice Review, 23 July 2013

  37. R-8 distribution of M1 and M2 splices produced before LS1 in sectors 7/8 and 8/1 Sector 7/8 (updated 17.07.2013) n=136 (M1+M2) 14× R-8excess>5 μΩ (10.3%) R-8max=116 μΩ Sector 8/1 (updated 17.07.2013) n=152 (M1+M2) 12× R-8excess>5 μΩ (7.8%) R-8max=34.9 μΩ C. Scheuerlein, 4th Splice Review, 23 July 2013

  38. R-8 distribution of M3 splices produced before LS1 in sectors 7/8 and 8/1 Sector 8/1 (updated 17.07.2013) dipole R-8 results; n=80 15× R-8excess>5 μΩ (18.8%) R-8max= 34.5 μΩ Sector 7/8 (updated 17.07.2013) dipole R-8 results; n=68 7× R-8excess>5 μΩ (10.3%) R-8max=28.4 μΩ C. Scheuerlein, 4th Splice Review, 23 July 2013

  39. US weld imperfections in QQBI.7R5 before repair • Examples non conform line M US welds • No excess length • Displaced strands • Welding until the extremity of the cable (no excess length) • Spools crossed on the welded joint No excess length Displaced strands C. Scheuerlein, 4th Splice Review, 23 July 2013

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