Status on the DFBXF commissioning

Transcription

1 Status on the DFBXF commissioning Cryogenic Performance Panel C. Darve March 28th

2 Procedure steps and checks Based on S78 commissioning (R. Rabehl 05 July 2007): Cool-down part 1 (cool-down from 300 K) Monitor insulation vacuum in the DFBX mbar Monitor pressures, current leads temperature See graph Check that every lead is correctly identified at the level of the cryogenic control Y14 and Y13 are swapped. Check that the FT are installed at the correct position X1, Y14 and Z4&5 Check the lead-head heater system for correct functioning. Verify correspondence between the setpoint and the measured temperature. In addition, the lead flag Pt sensor and the cartridge heater thermocouple readings should be compared and the control loop retuned as necessary Raised temperature set-point to 50 C Tune the valve alignment to operate CV891 in their correct range On going difficulty Check the PCO phase 10, 30 and50 operations Used semi-automatic The temperatures at the top of the HTS part, TT891) brought to the nominal standby value (70 K) Stable for days Nominal cooldown flows should be established in each of the DFBX low current lead clusters on going difficulty Record the mass flows in all current leads at stable condition See graph Check for cold spots on the DFBX Condensation was identified 2

3 Procedure steps and checks Cool-down part 2 (filling with LHe and current leads at operating temperature; cold operations) Check liquid helium consistency geometric and control parameters are ok Make sure that no oscillations occur. PID optimized Check the lead-head heater system all functional Monitor current lead chimneys for condensation or ice band heater work properly. Check for cold spots on the DFB None Check gas flow for cooling and its control HTS ok, difficulties with low current leads (Vapor Cooled Current Leads). Measure and note down boil-off rate of the DFBX at zero current see figure Measure and note down the mass flow through the individual leads see graph Check and optimization of operational parameters (levels, flows, temperatures) to meet the requirements for the operation of the current leads main loops are tuned. Further work to complete next week. Verify the process and recovery procedures after non-nominal conditions and transients caused by utility stops checked with cryo-system events 3

4 Status for ELQA- this morning 2g/s off set 4

5 DFBXF Issues Condensation First cool-down of the DFBXF (12/03/08) condensation on the resistive lead chimneys T < -10 C observed with LHe in the helium tank. risk of ice on the top plate structural integrity Lead cooling valves, CV981, don t allow proper flow rate. i.e. too large flow for 2% opening. G10 isolators covered with H 2 O created electrical hazard Root Causes of condensation and excessive flow: 1. The baffle power lead design is not effective. 2. Modification of PV890 into a control valve was not sufficient w/o control variable. 3. Sector pressure variations and excessive pressure drop through a check valve prevent an accurate control of CV891. Note: consolidation must take into account the limited space available G10 to remain dry Frosted Chimneys

6 DFBXF Solution - Condensation Heater system installation on the four chimneys: 80 W of heater by chimney. Estimated contact surface ~ 50% Completed CV891 electronics tuning for 200 mbar operating range Completed Using previous DFB expertise, the DFBXF cool-down was resumed last week. Temporary anticondensation system was validated in less than a week. Ongoing attempts to limit the excessive flow: - Tuning of low current lead cooling flows by implementation of a new control loop Can we operate CV891 without the risk of freezing the resistive leads? - Testing the operation of CV891 for different valve opening and DP: With larger DP for 5% opening Recall: When no current: Validate the use of 1) fixed minimum voltage/resistance or 2) no cooling through the resistive lead control valves, CV891 (short and long term solution?) When leads are powered: Use Voltage/Current/Resistance. 6

7 Two boil-off tests with identical results (12 and 21 of March) ~ 100 Watt 7

8 Control on resistance status Goal: collect all current and voltage read-back on the same platform. Use PLC for PVSS loop control 600 and 120 A currents are already available for PVSS/SCADA control loop. Use pre-defined control loop on TT voltages are recorded on QPS machine (PC): can we import them to our PLC? long term plan : get the 120 Voltage on PVSS 7.0E-02 AMI 600 A 6 Lead Assembly Test Data Voltage Drop vs. Coolant Flow 6.5E E-02 On going effort with M. Soubiran, E. Blanco and many others. Coolant Flow per Lead, g/sec 5.5E E E-02 = Recommended Operating Point Write the specification and functional analysis into development 4.0E E E Lead Voltage Drop, mv LBNL EN: Voltage drop as a function of coolant flow for the AMI 600 A 6-lead assembly. 8

9 DFBXF Issue Check valve, NV893 Large pressure drop observed during earlier fill of the helium tank Large impedance on the helium tank venting circuit preventing LHe fill on 03/27/08 (third time refill was made) 9

10 DFBXF Check valve, NV893 Design weakness NB: Estimated cracking pressure: 220 gr 25 mbar 10

11 Input from Joseph Ranson, Phil Fund, Roger Rabehl and Tom Peterson PHPK design 11

12 DFBXF Solution Check valve, NV893 Remove the check valve, NV893, preventing the third refill (03/27/08) Completed DFBXF cool-down was resumed without problem. Better pressure stability and level control w/o NV Can we operate without? Risk of liquid level instability More sensitive to header D pressure variation Quench recovery PV930 pressure switch 12

13 Planning Short term: Check if we can operate w/o NV893. Tune cooling parameters using the new control loop on PV890. Conclude on the Engineering Change Request (add temperature sensors, controlled PV890, etc..) Optimized request (performance, time, money). Long term: CV891 manner: Initial tray accounting for HCC priority (test 600A, no 120A correctors tested for 5 TeV run) Condensation manner: Consolidation of every DFBX based on a final configuration (bracket heaters, dry air ) Check valve, NV893 manner: Consolidation of every DFBX (remove them all, re-machine Vespel extremity, etc..) 13