Safety approval of the installed copper cooling pipes CO2 Cooling Safety approval of the installed copper cooling pipes CMS upgrade meeting 28 January 2009 Hans Postema - CERN

Cooling Pipes The currently installed cooling pipes are virtually impossible to replace People ask: “Is this really the case” Please have a look at the following slides 28 January 2009 Hans Postema - CERN

Empty YB0 – far left 28 January 2009 Hans Postema - CERN

YB0 – fully cabled 28 January 2009 Hans Postema - CERN

YB0 - numbers Tracker cooling pipes below all the cables HB: 180 cables, 180 optical fiber cables EB: 1600 cables, 180 optical fiber cables Tracker: 3000 cables, 640 Optical fiber cables 9 month plus, installation time Removing and reinstalling ~10 year old EB cables is inviting trouble 28 January 2009 Hans Postema - CERN

Re-use of installed pipes The currently installed pipes are OD=14 and OD=16 mm copper pipes with a wall of 1 mm Cannot be used for 2 phase CO2 cooling without special precaution But can be used when the system design takes care that pressures remain below a limit Avoiding 100+ bar pressures is also advantageous for detector design 28 January 2009 Hans Postema - CERN

Storage tank The system contains a cooled storage tank When system is inoperative, all liquid is condensed in the tank, all warm components are filled with gas (Standard for cryogenic systems) A very similar system is used for the CDF COT flange cooling, same concept, different fluid, different temperature. See next slide 28 January 2009 Hans Postema - CERN

CDF – COT endplate cooling Courtesy Richard Schmitt FNAL 28 January 2009 Hans Postema - CERN

Which pressures Strong request for detector operation with coolant at +15 C. Avoids condensation during the installation and testing phase. For this a safety valve setting at 57 bar, corresponding to +20 C seems acceptable. Normal operation is below 0 degree C, which corresponds to 35 bar 28 January 2009 Hans Postema - CERN

Operation modes Normal operation, system cooled by commercial chiller, CO2 temperatures between 0 and -20 C, pressures 35 to 20 bar Testing during installation, system cooled by chilled water, temperature +15 C, pressure 50 bar Storage during shutdown, cooled by standard CERN chilled water system, temp +5 C, 40 bar 28 January 2009 Hans Postema - CERN

Meeting with CERN safety Meeting with Benoit Delille on 5/12/2008 Using French safety code CODAP-2000 Stress limit during operation: UTS/4 Stress limit during test: UTS/2.6 Thus pressure test at 1.43x max. operating pressure 28 January 2009 Hans Postema - CERN

CERN safety, question 1 Check that the stress at 57 bar is indeed 44 MPa, including possible thermal effects, including the brazed connections. 28 January 2009 Hans Postema - CERN

CERN safety, question 1 (2) A qualification program was set up for for the brazed connections. The testing was performed by TS-MME-MM The last report in the test series was: Metallurgical qualification of Cu brazed assemblies for the cooling circuit of the CMS tracker 14-05-07 EDMS number 842794 Available at: http://cern.ch/Postema/CO2_cooling/copper_tube/ 28 January 2009 Hans Postema - CERN

CERN safety, question 1 (3) Follow up QA took place and was documented Last report in this series was: Follow-up of witness samples of Cu brazed assemblies for the cooling circuit of the CMS tracker 08-08-07, week 31/07 EDMS number 861965 Available at: http://cern.ch/Postema/CO2_cooling/copper_tube/ 28 January 2009 Hans Postema - CERN

CERN safety, question 1 (4) An overview of the complete documentation is described in: Brazed_connections.doc Available at: http://cern.ch/Postema/CO2_cooling/copper_tube/ Conclusion: All brazed connections are stronger than the copper pipe material 28 January 2009 Hans Postema - CERN

CERN safety, question 1 (5) Pipes are supported in Aerogel insulation material and can slide freely. The longest straight sections are about 4 m radially out along the YB0 iron and about 5 m along the vac tank of the CMS coil Thermal contraction of copper from +20 to -20 is 680 micron/meter 4 mm contraction is easily absorbed by the Aerogel, no additional stress in pipe material 28 January 2009 Hans Postema - CERN

YB0 – fully cabled 28 January 2009 Hans Postema - CERN

Pipe trays and insulation Final holding strap Insulation: Aerogel Spaceloft 9251, k=0.013 W/m*K (against 0.04 W/m*K of Armaflex). Dusty and difficult material to handle, but excellent performance. All parts enclosed in polyethylene bags, sealed, then adhesive vapor barrier around Pipe comb Nuts to be welded on the Vacuum tank 28 January 2009 Hans Postema - CERN

CERN safety, question 2 Check that this stress level is below UTS/4 for the type of copper that is currently installed. Reply: Certificate of the copper tube material received from Christian Saint-Jal (CERN). http://cern.ch/Postema/CO2_cooling/copper_tube/ Minimum tensile strength 220 MPa 44 MPa below 220/4=55 MPa 28 January 2009 Hans Postema - CERN

CERN safety, question 3 When calculating the pressure test, can you consider a maximum stress of UTS/2.6? A maximum stress during operation of UTS/4 and a maximum test stress of UTS/2.6 implies that the pressure test takes place at 1.43x operating pressure. Max. operating stress at 57 bar = 44 MPa Stress during pressure test 1.43x44=63 MPa 28 January 2009 Hans Postema - CERN

CERN safety, question 3 (2) Factory test Rp 0.2 = 75 MPa Test by Stefano Sgobba Rp 0.5 = 106 MPa Pressure test at 1.43x operating is thus in principle acceptable, still below elastic limit Since the stress during test is rather close to the elastic limit, we would like to propose the following: 28 January 2009 Hans Postema - CERN

CERN safety, question 3 (3) Our proposal: Test one equivalent circuit in the lab at 1.43x maximum operating Test all circuits installed in CMS at 1.25x maximum operating 28 January 2009 Hans Postema - CERN

Meeting with Safety 23/1/09 Dear Hans, Last week, you showed me your presentation which concerns the cooling circuits for the CMS pixels. For a design pressure of 57 bar, the level of stresses you mention (44MPa) is below the limit of 217/4=55MPa.For the test pressure of 1.43*57 bar, the level of stresses (63 MPa) is below the limit of 217/2.6= 83MPa. As the design looks fine for these conditions, I accept that a test at 1.43 times the design pressure is done on a representative piece of equipment in a lab (with representative supports, ...). I would like to add a destructive test of that piece of equipment under pressure (test carried out with water). For the pipes already installed, as you will carry out the tests with gas for cleanliness, please take 1.25 times the design pressure as test pressure. Can you also make sure that in the whole installation, there is no possibility of having cold gas-liquid trapped (between valves for example). In such case, protections against overpressure (safety valve or rupture disc) have to be installed. Looking forward to the tests, Benoit Delille 28 January 2009 Hans Postema - CERN

Summary With this system design, max coolant temp at 15 degrees C and safety valve at 57 bar, the currently installed copper tubes can be approved by CERN safety We will build one equivalent circuit for destructive testing by CERN safety We will pressure test the installed copper tubes with gas at 1.25x57=71 bar 28 January 2009 Hans Postema - CERN

Conclusion The most crucial step towards a CO2 cooling system has been achieved With this approval, the road to CO2 cooling for the CMS Tracker is OPEN! 28 January 2009 Hans Postema - CERN