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MPP meeting
Participants
Amalia Ballarino
Andrzej SIEMKO
Antonio Perin
Antonio Vergara Fernandez
Arjan Verweij
Boris Bellesia
Glyn Kirby
Jean-Philippe Tock
Juan Casas-Cubillos
Maria Paz Casas Lino
Marta Bajko
Michele Modena
Nuria Catalan Lasheras
Rob Wolf
Roberto Saban
Thiesen Hugues
Vincent Chareyre
Vittorio Remondino
Walter Venturini Delsolaro
MPP meeting 28 April 2008
1. Replacement of dipole 1055 by 1334. All arc circuits were affected and the electrical qualification was performed successfully. The replacement took 6-7 weeks. The preparation of the dipole took one week in parallel with opening the interconnect.
2. The line N splices were inspected in the four interconnects which were already open for the dipole replacement. There was no evidence of bad splices but most of these splices were re-done as part of the reconnection activities.
3. Shortening of the 500 bus-bars concerning six 500 series SSS. All circuits in the M lines were affected and qualification followed the repair.
4. The inner triplet was interconnected for the first time.
5. Insulation pieces were added to the DFBAO affecting all 6kA circuits powered through it.
6. The short in MB 3006 was found in the IFS and repaired.
7. Continuous monitoring showed a leakage current in Q22L8 during cool-down which disappear when cold and re-appear during warming-up at the same temperature. Insulation was repaired affecting the RQD circuit.
8. The high resistance measured at cold in one of the dipole correctors of Q5R8 prevents the powering of the circuit. A warm corrector has been installed in the tunnel and is being commissioned.
9. An insulation fault was localized in the connection cryostats when the cool-down started. All the CC have been repair and qualified.
The pending non-conformity concerns the high resistance of the MCBCHS5.L8B1. Investigation at warm localized the fault inside the Q5 cold mass. New measurements confirm the resistance is still there and is now five times larger. Last year measurements showed resistance growing with current up to 20 mO at 6 A. The latest measurements showed 20 mOhms at 1 A. It need to be studied if we can put some current into the circuit. PO needs to be informed to connect or ground accordingly the detector to the power supply. The other MCBCs in the same cold mass and of the same polarity need to be tested above nominal to determine the spare correcting capacity. They have been trained in the manufacturer above to 100 A. This will be added to the specific document for 7-8. (Action: G. D'Angelo)
During the high voltage tests of the main dipole circuit there were two discharges (1800 and 1900A in MBB and MBA lines). Two electronic cards for temperature sensors in the 13 kA current leads were burnt. As it happened already in the past, one sensor has been lost but this time it can not be changed. As there is a second sensor in the lead, the lead can still be operated but loosing this last sensor will imply extracting and repairing the current lead (four weeks).
ElQA proposes to change the testing procedure. The circuits together with the proximity equipment will be tested in a first phase, The measurement chain including electronic cards and cabling will be tested separately in phase two. In the last phase, the measurement system will be reconnected to the RB circuits and tested again. The heater system circuits can stay connected at all times. The QPS detection system and cables have been qualified at 3.1 kV and needs to be tested in both circuits at the same time. Testing them separately will mean four high voltage tests. The procedure to test them needs to be clarified with the QPS team in order not to stress excessively the insulation. MPP suggested to invest time on finding the origin of the failure. (Action: J. Casas for next MPP meeting)
G. Kirby reminded that one of the quench heaters in Q4L8 was lost and the magnets is protected bu the redundant circuits.
In the DFBX, additional sensors have been installed in the G11 insulation pieces to control the flow on the copper leads. The leads were designed to be controlled in voltage. The current threshold for QPS has been set at 140mV what may indicate the leads are not conveniently cooled. Current tests have been performed for 10 minutes at 550A. A long run will be needed to validate this solution.
A voltage tap in a MCBC corrector is lost. This is still being investigated to locate where the circuit is broken.
A. Vergara reminded that the specific documents for sector 7-8 are being circulated for approval.
Sector 7-8 consolidation J.Ph. Tock
Consolidation work done in the sector 7-8 affecting the electrical circuits:1. Replacement of dipole 1055 by 1334. All arc circuits were affected and the electrical qualification was performed successfully. The replacement took 6-7 weeks. The preparation of the dipole took one week in parallel with opening the interconnect.
2. The line N splices were inspected in the four interconnects which were already open for the dipole replacement. There was no evidence of bad splices but most of these splices were re-done as part of the reconnection activities.
3. Shortening of the 500 bus-bars concerning six 500 series SSS. All circuits in the M lines were affected and qualification followed the repair.
4. The inner triplet was interconnected for the first time.
5. Insulation pieces were added to the DFBAO affecting all 6kA circuits powered through it.
6. The short in MB 3006 was found in the IFS and repaired.
7. Continuous monitoring showed a leakage current in Q22L8 during cool-down which disappear when cold and re-appear during warming-up at the same temperature. Insulation was repaired affecting the RQD circuit.
8. The high resistance measured at cold in one of the dipole correctors of Q5R8 prevents the powering of the circuit. A warm corrector has been installed in the tunnel and is being commissioned.
9. An insulation fault was localized in the connection cryostats when the cool-down started. All the CC have been repair and qualified.
Review of the ElQA non conformities in sector 7-8. V. Chareyre
All but one the ElQA non-conformities in sector 7-8 have been closed. Two recently found non-conformities are being treated.The pending non-conformity concerns the high resistance of the MCBCHS5.L8B1. Investigation at warm localized the fault inside the Q5 cold mass. New measurements confirm the resistance is still there and is now five times larger. Last year measurements showed resistance growing with current up to 20 mO at 6 A. The latest measurements showed 20 mOhms at 1 A. It need to be studied if we can put some current into the circuit. PO needs to be informed to connect or ground accordingly the detector to the power supply. The other MCBCs in the same cold mass and of the same polarity need to be tested above nominal to determine the spare correcting capacity. They have been trained in the manufacturer above to 100 A. This will be added to the specific document for 7-8. (Action: G. D'Angelo)
During the high voltage tests of the main dipole circuit there were two discharges (1800 and 1900A in MBB and MBA lines). Two electronic cards for temperature sensors in the 13 kA current leads were burnt. As it happened already in the past, one sensor has been lost but this time it can not be changed. As there is a second sensor in the lead, the lead can still be operated but loosing this last sensor will imply extracting and repairing the current lead (four weeks).
ElQA proposes to change the testing procedure. The circuits together with the proximity equipment will be tested in a first phase, The measurement chain including electronic cards and cabling will be tested separately in phase two. In the last phase, the measurement system will be reconnected to the RB circuits and tested again. The heater system circuits can stay connected at all times. The QPS detection system and cables have been qualified at 3.1 kV and needs to be tested in both circuits at the same time. Testing them separately will mean four high voltage tests. The procedure to test them needs to be clarified with the QPS team in order not to stress excessively the insulation. MPP suggested to invest time on finding the origin of the failure. (Action: J. Casas for next MPP meeting)
G. Kirby reminded that one of the quench heaters in Q4L8 was lost and the magnets is protected bu the redundant circuits.
Status of the DFBs in sector 7-8
A. Perin informed that there is not yet conclusion for the liquid levels. Boil-off tests have not be done yet as priority was put on performing ElQA. Anti-condensation system were installed. Small problems have been fixed. No powering can be done yet.In the DFBX, additional sensors have been installed in the G11 insulation pieces to control the flow on the copper leads. The leads were designed to be controlled in voltage. The current threshold for QPS has been set at 140mV what may indicate the leads are not conveniently cooled. Current tests have been performed for 10 minutes at 550A. A long run will be needed to validate this solution.
Status of the level gauges in the stand alone magnets in sector 7-8
J. Casas Cubillos informed that preliminary observations show a volume 40-70% higher than predicted. The data still needs to be analyzed. They can not be released for powering.AOB
V. Chareyre informed that a leakage current has been measured in the RB circuit of sector 3-4. An ElQA team will investigate if the problem is in the cold part after which it is suggested to stop the cool-down and stabilize the temperature at 180 K to verify the short. It is not advisable to wait for 80 K as the damage threshold of the PIMs will be reached.A voltage tap in a MCBC corrector is lost. This is still being investigated to locate where the circuit is broken.
A. Vergara reminded that the specific documents for sector 7-8 are being circulated for approval.
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