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Electrical Shutdown and Insulation Issues at Cryogenic Cooling Tower: Incident Report

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On November 29, 2011, a short-circuit occurred in the water level sensor at cooling tower SF4, resulting in an electrical shutdown and cessation of cooling to the cryogenic installation at point 4. Further investigations revealed a deterioration in the vacuum insulation on the DSLC, with significant pressure rise and evidence of icing in the annex volume. Intervention was required to restore nominal vacuum conditions and address potential air leaks. A comprehensive plan for maintenance and recovery has been developed, involving inspections and equipment checks.

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Electrical Shutdown and Insulation Issues at Cryogenic Cooling Tower: Incident Report

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  1. Cryo problem – point 4 • At 20:26 water level sensor of the cooling tower SF4 at pt 4 had a short-circuit, which resulted in an electrical shutdown of the tower (24V). This cut the water to the cryo and at 20:29 the cryo installation at pt 4 switched off. • Deterioration of insulation vacuum on DSLC

  2. DSLC Pressure Rise 29 Nov 2011 permanent turbo pump permanent turbo pump vac gauges vac gauges DSLC 500 meters DFBLC Arc 3-4 Q7R Q11R • annex volume • current lead? • heater? Sector 3-4 UJ33 Simplified insulation vacuum layout Paul Cruikshank TE/VSC 29/11/2011

  3. Icing of annex volume Oct 2011, Pressure perturbation seen on DSLC when put into communication with annex Self recovery of pressure indicates air leak Paul Cruikshank TE/VSC 29/11/2011

  4. DSLC Pressure Rise 29 Nov 2011 UJ33 Sector 3-4 permanent turbo pump permanent turbo pump vac gauges vac gauges DSLC 500 meters DFBLC Arc 3-4 Q7R Q11R annex volume - current lead, heater? Summary of events: Ice observed on DFBLC annex volume Oct 2011 Annex volume connected to DFBLC volume 11/10/11 Cryo stop P4 28/11/2011 pm Pressure in DSLC rises to 10 mbar in few hours VSC piquet intervention to install mobile pump Nominal vacuum conditions re-established Annex volume still in communication!! Cause of leak ?? Consolidation to do?? Paul Cruikshank TE/VSC 29/11/2011

  5. Max. Temperature on DSLC reaching 250 K at 14:00 and in a short period  need ELQA before powering (A. Siemko)

  6. 600 A on Sector 34 (M. Pojer) Not powered from DSLC Not used

  7. Currents on the circuits powered via DSLC

  8. Plan • 09:00 Access for blocking out power converters (EPC) + patrol for verifying the DSL (ice or condensation) – VSC+CRG • 10:00 Access for disconnecting cables • 12:00 at the earliest cryo conditions for ELQA • ELQA (~2 hours) • Re-connection (~2 hours) • Unblocking power converters • HW commissioning tests over (part of) night  need MP3 and QPS support. Possible list (M. Pojer, A. Siemko) • PIC2_CIRCUIT QUENCH VIA QPS • PCS (to check the splices) • PNO.a3 (cycle to full current)

  9. In the best case fill in the early morning • Van der Meer scan starting in the late morning/afternoon.

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