PS and crates service

1. PS and crates service Issue observed on some Wiener LVPS internal power lines & other news… vincent.bobillier@cern.ch

2. PS and crates service • Outline • Wiener LVPS internal power line issue • Observed problem • Analysis and discussion with Wiener • Outcome and recommendation • Water cooled PSU and cooling network cleanliness • Short preventive maintenance status report • Caen purchase contract and forecasts vincent.bobillier@cern.ch

3. PS and crates service • Wiener LVPS internal power line issues – Observed problem • Observed during the modification of 4 water-cooled Atlas-TRT LVPS by Wiener • Some power wires (connecting the PS output plug to the modules) have been found with melted and cracked insulation material • Potentially concerned: • All Maraton and PL5xx LVPS with an output current of 50A and above. vincent.bobillier@cern.ch

4. PS and crates service • Wiener LVPS internal power line issues – Analysis and discussion with Wiener • First assumption from Wiener: Related to the wire isolation material causing oxidation of individual copper strands followed by overheating. • Wiener changed this wire for a tinned version on units produced after 2007. • Discussion on the wire cross-section: • According to EN standards 10mm2 are required for 50A (Wiener internal wire: 6mm2) • Wiener explained that for short distances the wire can be assimilated to PCB tracks. Wiener provided a copy of the TUV CE certification tests (according to the EN-60950 standard). • Safety concern: Wiener states that this internal wire issue presents no risk for users nor risk of inflammation. Each PSU channel is self protected against over currents and overheating (PS level). • Wiener did not observe other occurrences of damaged power wires, but did measure high resistance values on checked wires. vincent.bobillier@cern.ch

5. PS and crates service • Wiener LVPS internal power line issues – Analysis and discussion with Wiener • Wire loss measurements were performed on a few PSUs (of different types and used in different setups). • Measurement method • Disconnected sense lines and no local sense jumpers (on-module internal regulation). • Voltage measurement on the output connectors with and without load. • Delta V is directly related to the internal wire loss. • Different LVPS types have different internal wire lengths and layout Sense lines disconnected Local sense jumpers removed DVM measurement Connection to load vincent.bobillier@cern.ch

6. PS and crates service Wiener LVPS internal power line issues – Measurement results vincent.bobillier@cern.ch

7. PS and crates service • Wiener LVPS internal power line issues – Outcome and recommendation • The source of the problem is not yet fully understood. Possible origins: • Aging effect on the wires • Related to the operating conditions (temperature, absence of airflow / installation in confined space) • No other occurrences of damaged wires was observed so far. • Next steps and recommendation: • Perform material analysis on the broken wires (Goal: confirm Wiener suspicion on the corrosion effect of the isolation material) • Monitor the stability of the wire resistance over time • Users/experiments to perform further internal voltage drop analysis • Select a few PSUs (if possible different types, operational conditions and produced before/after 2007) • Perform the measurements presented on the previous slides regularly (for example during every technical stop) on the selected units. • Share your results with the PS service • Re-assess the situation yearly vincent.bobillier@cern.ch

8. PS and crates service • Water cooled PSU and cooling network cleanliness • Wiener and Elcotron reported this on several occasions • Important amount of metallic particles found in the water cooled LVPS. High risk of clogging the 4mm PSU cooling circuit. • Degraded connector seal resistance to pressure (when disconnected) • Recommendation for the PSU • Purge all PSU with compressed air • Clean the internal PSU cooling circuit with clear water • Repeat the operation twice • Some ideas for the cooling network • Inspect/change the rubber tubes • Install magnetic filtering systems • Use an alternative fluid? Internalview of a rubber tube (from CMS) Metallicdustfoundwhilecleaning a PSU vincent.bobillier@cern.ch

9. PS and crates service • On going preventive maintenance campaign (focus on Wiener equipment) • Atlas Status: On going Total: 287 units Done / in progress: 180 • CMS Status: On going Total: 349 units Done / in progress: 200 • LHCb Status: To be scheduled Total: 143 units • AliceNA Total: none • New request : BE-CO wants to have 200 VME PSU maintained preventively before the end of LS1. Details to be received and discussed • Current issues: • Shortage of shipping boxes for equipment shipped back to Wiener • Internal CERN transportation takes longer than expected • Will have some impact on the schedule • Many thanks for the good cooperation so far. vincent.bobillier@cern.ch

10. PS and crates service • Caen purchase contract and forecasts • Caen purchase frame-contract B1226 status • Running until end of 2019 • Spent so far: 4.4 MCHF • Remaining CERN budget code expenditure shall not exceed 380 kCHF until 2019 • Make effort to spend on team money • Purchase forecasts for the coming years is required from the experiments and users. Particularly if CERN budget codes are planned to be used. • Electronics coordinators please assess exceptional purchase needs (if any) for LS2. vincent.bobillier@cern.ch