QRL helium leak tightness and consolidation during LS2

1. QRL helium leak tightness and consolidation during LS2 TE-CRG-OP K. Brodzinski CRG-TM 27th May 2019

2. Outlook • Introduction • QRL design, failure mechanism and analysis • Work done during LS1 • Necessary tooling and manpower • LS2 after warm up diagnostics – today status • LS2 open actions • Conclusions K. Brodzinski_CRG-TM_2019.05.27

3. Introduction The Cryogenic Distribution Line (QRL) is the main distribution circuit of LHC cryogenics. Following the machine, it is divided into 8 sectors supplying all cold magnets of the LHC. The QRL is built mainly from austenitic stainless steel contracting between 300 K and 1.9 K by 3 mm/m (90% of contractions are done between 300 K and 80 K). QRL unit element so called QRL cell (example for standard cell 15R4) ~ 107 m QRIOA Internal tubes connection type: QRIOA QRIOA QRICA QRIAA Service module Pipe element Fixed point element Internal fixed point Internal fixed point (or vacuum barrier) Internal tubes connection type: end-end end-end end-end end-end compensators sleeves end-end end-end compensators sleeves Thermal contraction of ~54 m  162 mm Magnet cell 14R4 Magnet cell 15R4 K. Brodzinski_CRG-TM_2019.05.27

4. Available documentation QRL interconnection with integrated compensators Main drawings: C1105H018 A4 1/2 and 2/2 – QRL interconnection QRICA C1105L502 A1 – QRL interconnection QRICA – isolation C1105L504 A1 – QRL interconnection QRICA – isolation 5 K, 20 K C1105L105 A2 – QRL interconnection QRICA – isolation 80 K Main procedures: C1105-PO-123 Procédure de réalisation de l'isolation des interconnexions sur site. (EDMS #502707) C1105-PO-037 Procédure d’isolation des interconnexions QRICA sur site. (EDMS #556420) C1105-PO-099 Installation et soudage manuel des compensateurs externes. (EDMS #520401) The QRL header C or D leakrepairs (experiencedduring LS1). (EDMS #1290284) Tunnel wall LHC magnets K. Brodzinski_CRG-TM_2019.05.27

5. Failure mechanism A real “virtual” leak (not seen during global leak test) He (P, T) Metallographic analysis by EN-MME (S45, 14R4) Filling of the inter-layer space with time (3-4 years of operation) Pressure increase of the inter-layer space during warm-up  compensator collapsing ! LS1 confirmed compensators collapsed on lines C and D of the QRL. K. Brodzinski_CRG-TM_2019.05.27

6. Analysis The failures were seen during the warm up process with punctual rapid vacuum degradation with progressive pressure recovery – see below curve. Dedicated He leak tests confirmed He presence in the vacuum volume. Following the problem discovery dedicated X-ray campaign was done during LS1 on whole QRL length (header C and D compensators) discovering additional deformed compensator (still tight not seen on vacuum pressure signal). Vacuum pressure s8-1 ss D K. Brodzinski_CRG-TM_2019.05.27

7. LS1 repairs – dashboard Each spare compensator was checked for tightness by VSC before installation process. • Global duration of one compensator repairs affects 3 teams and takes ~8 weeks: • Spare validation – 1 week • Mechanical work – 4 weeks • Vacuum subsector pumping – 2 weeks • Final tightness validation – 1 week Two blue cases represents new design bellows with one compensation layer tight and all other vented to vacuum. K. Brodzinski_CRG-TM_2019.05.27

8. Available spares and tooling Originally 7 .. 10 spare bellows/compensator type were placed at CERN storage. Regarding LS1 experience, the spares strategy for lines C, D and E/F was reviewed and defined number of spares was ordered. The list of available critical spares is presented below: Line C (DN100) -> 26 spares Line D (DN150) -> 48 spares Line F (DN80) -> 17 spares (in most of the cases can be installed also on line C) Two types of rotating cutting machines are needed for a compensator replacement intervention. K. Brodzinski_CRG-TM_2019.05.27

9. VSC feedback for LS2 There is no compensator failure detected by partial abrupt vacuum degradation observed during warm up process in any QRL vacuum subsector. At the limit of being critical – more details and required actions on next slide Known after EYETS new Well known leak on line B ~10^-4 mbar*l/s at 1 bar, present since beginning of the LHC operation – no action as B is a VLP Known after EYETS new Known after EYETS LS2C on 17.05.2019 by VSC • S4-5/ssG/lineD (new, ~5*10^-8 mbar l/s at 1 bar): • Actions: x-rays of all QRICx interconnections to be done (8 positions). Then further actions will be defined. • S7-8/ssH/lineC (new, ~5*10^-8 mbar l/s at 1 bar): • Actions: x-rays of all QRICxinterconnections to be done (9 positions). Then further actions will be defined. • S8-1/ssD/lineD(known, 1.5*10^-7 mbar l/s at 1 bar): • Actions: x-rays of all QRICxinterconnections to be done (8 positions). Then further actions will be defined. K. Brodzinski_CRG-TM_2019.05.27

10. Sector 1-2, ss B leak • s1-2/ssB/lineC (known, 2*10^-4 mbar l/s at 10 bar, dcum 2770 ... 2774 m): this leak was detected during LS1, pre-localized on QRICA in 14L2 – tightness test after opening of external compensator did not confirm any leak at this location. Present localization points at neighbor, rigid pipe to pipe interconnect QRIOA. • Actions: two nearest QRICA will be x-rayed, opening of the interconnection and tightness test of line C is required. To be x-rayed Dcum: 2813 To be x-rayed To be open and tested 2760 2772 Line D compensator replaced during LS1, Checked during LS1 and EYETS? – no leak found on line C • X-rays planned for 28th May (tomorrow) • Opening of external compensator – tbd asap! K. Brodzinski_CRG-TM_2019.05.27

11. QRIOA 2772 – available space Measurements by CRG-OP on QRIOA 14L2 2772 m (21-05-2019) 24 cm 16 cm 17 cm 16 cm K. Brodzinski_CRG-TM_2019.05.27

12. Additional verification with x-rays • In addition to defined on previous slides x-rays for leak detection, 19 different interconnections shall be check because of minor NC seen during LS1. K. Brodzinski_CRG-TM_2019.05.27

13. Conclusions • The QRL is in good shape after LS2 warm up – no abrupt vacuum degradation was observed during thermal transient, • One known critical leak is present in s45/ssB/line C – localization and repairs require mechanical opening of external interconnection bellow  to be planed asap for definition of further actions – dedicated mechanical team needs to be defined for this task (2 x-rays are planned for 28th May on neighboring compensation interconnections), • Three other leaks need to be localized and further actions defined (25 interconnections to be x-rayed), no compensator replacement cannot be excluded in concerned regions, • Additional 19 x-rays will be applied to investigate on minor NC left after LS1 (all 46 x-rays to be completed at latest by end of August 2019 – agreed with EN-MME). Thank you ! K. Brodzinski_CRG-TM_2019.05.27

14. Back up – needed manpower (LS1) T0 – x-ray team to be available for investigation (EN-MME/Qualitec) – experience from LS1 shows that with one team production rate is 5 .. 8 rays/night T1 – mechanical team (2 technicians from TE-CRG) – mechanical preparation of the interconnection + isolation T2 – mechanical team (1 welder and 1 piper from TE-CRG) – integration of the compensator and welding of the interconnection (T1 and T2 require supervision and coordination of one technical engineer from TE-CRG) T3 – vacuum team (TE-VSC/AL40-30) – qualification of the spare compensators and final leak tightness tests Entire activity is to be coordinated by the QRL reference engineer from TE-CRG in collaboration with LS2 global coordination from EN-ACE. K. Brodzinski_CRG-TM_2019.05.27