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Investigation on flexible hoses in DFBAs

Investigation on flexible hoses in DFBAs. L. Tavian 21 July 2009 With the contribution of B. Vullierme, EN-MME. Today situation. Detection of news leaks in the vicinity of two DFBAs (L1 & L3) with symptoms identical to the leaks found in the S4-5 in 2007 in flexible hoses.

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Investigation on flexible hoses in DFBAs

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  1. Investigation on flexible hoses in DFBAs L. Tavian 21 July 2009 With the contribution of B. Vullierme, EN-MME

  2. Today situation • Detection of news leaks in the vicinity of two DFBAs (L1 & L3) with symptoms identical to the leaks found in the S4-5 in 2007 in flexible hoses. • The probability of new flexible-hose damages is high.

  3. S4-5 case reminder

  4. S4-5 case reminder TS-MME analysis

  5. TS-MME analysis

  6. TS-MME analysis Coloration visible à l’intérieur de l’onduleux

  7. 2007 investigation conclusion • The defects have been produced after the braid installation. • Multiple fusion points on the top of the corrugation equally distributed over 360°. (Affected length 10 cm). • No mixing of materials (braid vs corrugation) • Identification of several leak holes (min 3) • No visible oxidation. • No trace of mechanical wearing • No trace of chemical elements • No damage in between braid layers • Present most probable cause: Electrical phenomenon • Extremely short (<5ms) or without oxygen or with a cleaning after the defect creations. • Today this electrical phenomenon is not identifed yet: • During flexible production (but followed by an efficient cleaning)? • During B183 assembly activity ? (external welding activity with the DFB under vacuum?) • In the tunnel after vacuum evacuation ? (welding/brazing operation? Ground current return with vibration ? ELQA ?)

  8. Flexible-hose manufacturer recommendations • 1/Avoid bended flexible hoses. • 2/ Avoid high velocities in corrugated hoses which could create resonant vibrations resulting in premature fatigue failure. For braided hoses: < 50 m/s in gas if not bended < 25 m/s in gas if bended at 90° • Whatis the velocityseen by the DFBA hoses ?

  9. Flow scheme D line C line (PT961, TT961) Kv max, =%, R Flexible hose PT821 (L side only) Flexible hose configuration (straight or bended) not yet known (under investigation).

  10. He velocity in flexible hoses S1-2 S2-3 S3-4 S4-5

  11. He velocity in flexible hoses S5-6 S6-7 S7-8 S8-1

  12. DFBA comparison At least 4 DFBA more critical !

  13. Ultra-sonic vibrations • Is the flow able to produce ultra-sonic vibrations? • Velocity V= 25 to 100 m/s • Corrugation wave length: l= 0.005 m • Frequency: V/l= 5 to 20 kHz • If yes, what about ultrasonic welding? • Could explain the multiple fusion points • If yes, what about the status of the other flexible-hoses? • Braid and corrugations stuck together waiting a thermal or pressure transient (cool-down and quenches) to develop leaks? • If yes, DFBA in L5, L7, R7 & L8 are critical. • Braid and corrugations affected but still free of relative displacement? • If yes, stopping the flow will stop the degradation process.

  14. Proposal for consolidation of DFBAs in L1 and L3 • Replace the flexible hoses by smooth piping with lyres and/or pigtails (enough “free” space in the DFB vacuum vessel). • Integration study under way (collaboration with EN-MME) but as the “as built” configuration is not known, it will need in-situ adjustment. • Proposed internal diameter:10 mm • As for the S4-5, repair intervention by EN-MME. • Limit the velocity (i.e. the valve opening) in the 16 DFBA circuits. Could have impact on: • The cool-down time of the Q7L. • The PIMs recooling process (time, autonomy) • The temperature uniformity for SCS test.

  15. Consolidation road map (Already done as preventive measure) No mixing of materials Simultaneous development of several leaks

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