INDICO-FNAL (Indico)



US HL-LHC Accelerator Upgrade ProjectDisposition of Non-Conforming Plasma Coated PartsPrepared by:Miao Yu, US HL-LHC AUP Coil Parts L3 Manager, FNALReviewed by: James Blowers, US HL-LHC AUP QA Manager, FNALApproved by:Miao Yu, US HL-LHC AUP Coil Parts L3 Manager, FNALFred Nobrega, US HL-LHC AUP Coil Fabrication at FNAL L3 Manager, FNALJesse Schmalzle, US HL-LHC AUP Coil Fabrication at BNL L3 Manager, BNLGiorgio Ambrosio, US HL-LHC AUP MQXFA L2 Manager, FNALJames Blowers, US HL-LHC AUP QA Manager, FNALRuben Carcagno, HL-LHC AUP Deputy Project Manager, FNALGiorgio Apollinari, HL-LHC AUP Project Manager, FNALRevision HistoryRevisionDateSection No.Revision DescriptionV15/23/2019AllInitial ReleaseTABLE OF CONTENTS TOC \h \z \t "Level 1,1,Level 2,2,Level 3,3" 1.Introduction PAGEREF _Toc6561983 \h 42.End Spacers PAGEREF _Toc6561984 \h 43.End Saddles PAGEREF _Toc6561985 \h 54.Splice Blocks PAGEREF _Toc6561986 \h 65.Requirements PAGEREF _Toc6561987 \h 66.References PAGEREF _Toc6561988 \h 6IntroductionEnd spacers, saddles and splice blocks, to be used in MQXFA coils [1], are plasma coated using Al2O3 powder with 200 ?m ± 50 ?m thickness to increase the dielectric strength between the conductor and stainless steel parts. This insulation is in addition to the coil insulation scheme. Fig. 1.1 shows the models of 16 different end parts, which are coated everywhere except the surfaces inside the slits and the holes.Fig. 1.1 QXFA Coil End PartsDue to the brittleness of the thin layer of the coating material, careful handling, shipping and installation is always required, but sometimes the coating chips off. The criteria described in this engineering note are intended to be used when coating defects are found at the two coil winding facilities, including receiving inspection at both labs.Regarding when chips occur after the part has been installed in a coil, if at all possible repairs should be made to the end part (as opposed to unwinding and replacing the part). This is true even if the chip does not meet the acceptance criteria defined in this document. Such repairs are typically completed after reaction and before impregnation.End SpacersPart numbers include:F10088257Spacer-1, Lead End Layer 1 B2-IC1F10042026Spacer-2, Lead End Layer 1 B2-IC2F10042027Spacer-3, Lead End Layer 1 B2-IC3F10042035Spacer-1, Return End Layer 1 B2-IR1F10042036Spacer-2, Return End Layer 1 B2-IR2F10042032Spacer-1, Lead End Layer 2 B2-OC1F10042033Spacer-2, Lead End Layer 2 B2-OC2F10042034Spacer-3, Lead End Layer 2 B2-OC3F10042029Spacer-1, Return End Layer 2 B2-OR1F10042030Spacer-2, Return End Layer 2 B2-OR2From an electrical point of view, end spacers are floating parts between two adjacent turns, like coil wedges. The maximum voltage difference between adjacent turns in MQXFA coils will never exceed 105 V (including heater failure scenarios, as reported in [2]), which is lower than the Paschen minimum for helium.?Therefore, end spacers without coating in some areas are acceptable for use in MQXFA coils. In conclusion, unless the missing coating affects other functional requirements, end spacers with chips are accepted for use in MQXFA coils within the following constraints:Each individual defect shall fit within a theoretical circle of diameter 5mm. This may be verified using a defect size estimation transparency, or equivalent method. There shall be no more than 5 coating defects per part.Coating defect repair guidance:Defect on the spacer tips: cover with 3 mil S2 glass (the same tape to repair the cable insulation)Defect on the bottom ID surface of L1 spacers or top OD surface of L2 spacers: repair after reaction only, and cover with 1 mil KaptonDefect on the rest of the surfaces: no repair or engineer judgement.End SaddlesPart numbers include: F10042022Saddle, Lead End Layer 1 B2-IC4F10042037Saddle, Return End Layer 1 B2-IR3F10042031Saddle, Lead End Layer 2 B2-OC4F10042028Saddle, Return End Layer 2 B2-OR3Each end saddle is in contact with a midplane turn, and there may be a weak insulation between inner and outer layer saddles due to their large surfaces.? Peak voltages between midplane turns can reach 300 V in nominal conditions [3]. Therefore 100% coverage is required on the surface in contact with the cable. In this case, if the coating is missing at the edges or tips of the part, which can be repaired by adding S2 glass during winding and adding Kapton after reaction to provide the requisite 100% coverage, the part is acceptable for use, otherwise shall be rejected. On the other surfaces, end saddles with chips are accepted for use in MQXFA coils within the following constraints:Each individual defect shall fit within a theoretical circle of diameter 5mm. This may be verified using a defect size estimation transparency, or equivalent method. There shall be no more than 5 coating defects per part.Coating defect repair guidance (the saddle shall not be removed after reaction for repair):Defect on the saddle tips and edges that are not accessible after reaction: cover with 3 mil S2 glass (the same tape to repair the cable insulation)Defect on ID surface of L1 saddle or OD surface of L2 saddle: repair after reaction only, and cover with 1 mil KaptonDefect on the midplane surfaces: repair after reaction only, and cover with 1 mil KaptonDefect on the rest of the surfaces: no repair or engineer judgement.Splice BlocksPart numbers include:F10042599Splice Block, Lead End Layer 1 B2-IC5F10042600Splice Block, Lead End Layer 2 B2-OC5Each splice block is in contact with a midplane lead turn, and there may be a weak insulation between inner and outer layer saddles due to their large surfaces.? Peak voltages between midplane turns can reach 300 V in nominal conditions [3]. Therefore 100% coverage is required on the surface in contact with the lead cable. Since the splice blocks are always accessible to be repaired by adding Kapton after reaction without damaging the reacted cable, unless the missing coating affects other functional requirements, the part?is accepted for use in MQXFA coils within the following constraints:Each individual defect shall fit within a theoretical circle of diameter 5mm. This may be verified using a defect size estimation transparency, or equivalent method. There shall be no more than 5 coating defects per part.Coating defect repair guidance:Defect on any surface: repair after reaction only, and cover with 1 mil KaptonRequirementsUse of this procedure for acceptance of coating defects shall be documented in a manner traceable by individual coil.ReferencesMQXFA Final Design Report, US-HiLumi-doc-948MQXFA Electrical Design Criteria, US-HiLumi-doc-826Analysis of MQXF coil to coil-part electrical shorts and proposal of revised values for Electrical QC, US-HiLumi-doc-2122 ................
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