1. 25-11-08E.Focardi1 Tracker cooling plant Plant description Operational experience Upgrade project

2. 25-11-08E.Focardi2 Service cavern Detector cavern CMS location

3. 25-11-08E.Focardi3 TK cooling scheme Chilled water Primary plant (main chiller) Backup chiller “Brine” circuit Silicon Strip 1 Silicon Strip2 Pixel Preshower 1 USC Thermal Screen 2 Preshower 2 Thermal Screen 1 UXC

4. 25-11-08E.Focardi4 CMS fluorocarbon cooling system 7 liquid monophase detector cooling unit (2 for Silicon Strip Tracker, 2 for Thermal Screen, 1 for Pixels and 2 for Preshower) TS/CV-ContractCMS-Contract x piping 3 cooling loops in cascade: chiller, brine (now C6F14 after important failure on heat exchangers), fluorocarbon

5. 25-11-08E.Focardi5 5 Bizer compressor are located on the service cavern. They produce the cold fluid using the R507. In the first design the R507 exchange heat with a ‘brine’ fluid Tyfoxit. The Tyfoxit transports the cold fluid in the cavern and exchange with the C6F14 that is the final cooling fluid of CMS. The reason of using the Tyfoxit was related to the low cost and the high merit factor for the heat exchange properties. Using this fluid, the heat exchange area can be minimized. On the other hand the PH is ~12, so the fluid is aggressive especially with some alloy like aluminum and stainless steel. Particular attention to be dedicated to the selection of the material, i.e. stainless steel 316

6. 25-11-08E.Focardi6 CMS Tracker Strip Total of 15’232 detector modules Si operating temp. -10 0 C

7. 25-11-08E.Focardi7 TIB (Tracker Inner Barrel) Per each end: 4 cylindrical layers Layer 1 & 2: double sided, 168+216 modules Layer 3 & 4: single sided, 270+324 modules Triplets of modules are mounted on support cooling strings in a cylindrical distribution, each one of the 56 cooling loops serves groups of strings on the same layer as in the scheme below

8. 25-11-08E.Focardi8 TOB (Tracker Outer Barrel) 6 cylindrical layers Layer 1 & 2: double sided, 504+576 modules Layer 3 to 6: single sided, 648+720+792+888 modules Modules are mounted on “rods”, with 6 or 12 modules each. 688 rods, 344 rods at each end of TOB (symmetry) Each one of the 44 loops serve group of rods on the same layer as per the schematic below:

9. 25-11-08E.Focardi9 TEC (Tracker End-Caps) Per each end: 9 disks, each one with 8 front and 8 backward petals Number of modules varies from 22 to 15 for front petals, from 18 to 14 for back petals Each cooling loop serves “towers” of petals, one behind the other on different disks (petals on disks 1,3,5,7 and on disks 2,4,6,8,9)

10. 25-11-08E.Focardi10 Pipes, supports & manifolds Lessons learnt - resume Module contact material/ geometry Pipe material & shape Joining techniques Good choice, to repeat!Be careful! Special attention to… WhatWhyWhatWhy Stainless steel manifolding quality can be carefully checked with X-rays Stainless steel weldings Thin pipes require experienced manufacturer and careful control of welding parameters Soft soldering Easy to perform, can be repaired Aluminium pipes Deformation during bending, difficult to weld (?) Control of applied torque for screwed modules If the optimum is measured by testing, then all the assemly procedure is speed up Complex manifolding/distribution Pressure drops can dramatically increase and are not easy to calculate. Tests are needed on complete system Al pipingshort radiation lengthSilicon hoses Chemical degradation with fluorocarbon, maximum allowable pressure is low! Cu-Ni pipes 10% rejected due to leaks through pipe walls

11. 25-11-08E.Focardi11 Pressure & leak testing techniques Methods used: –Pressure test with N2, soap: 10 -5 mbar*l/s, easy to prepare, operator dependent, no quantification –He mixture, sniffer mode: 10 -7 mbar*l/s, ok but background noise –He, vacuum mode: 10 -10 mbar*l/s, some complexity for big systems, very reliable, quantification of leaks (see study of He/C6F14 leak rate correspondence by E. Anttila) –X-rays for all welds: necessary! Quality protocol to be established, either following ISO standard or through testing and validation He leak size Loss of PF-5060 [g/y][ml/y] > 10 -3 mbarl/s18701113 10 -4 mbarl/s10563 4 x 10 -5 mbarl/s1811 < 10 -10 mbarl/s85 Outcome: –The sub-systems shall be tested for a uniform leak rate and a uniform pressure, keeping a safety factor with respect to operating p (3x operating p in all sub-systems of Tk, none on Pixels) –Fluorocarbon requires almost vacuum level of leak tightness and careful selection of materials –Low temperatures play a significant role on leaks: to be taken into account! –He tests in vacuum mode are practical, also on assembled parts for a general quantification of leaks

12. 25-11-08E.Focardi12 From TK support tube to PP1 (1) At the Tracker support tube: custom-made “Lancashire fittings” (double NBR o-ring, irradiated with C6F14 and tested), 2 designs for different pipes. Manual tightening also in restricted spaces! Pre-bent pipes in soft copper, ID 10 mm: 3D models to get the numerical machine bending! Soft soldered connection to “long pipes” arriving in PP1 Custom-made ceramic connectors in PP1 for electrical insulation

13. 25-11-08E.Focardi13 From support tube to PP1 (2) Soft soldering: the tool applies a uniform heat around the pipe Testing with air at 10 bar, with soap Dielectric joints: ceramic parts vacuum brazed to copper connectors They are placed in PP1 for space reasons.

14. 25-11-08E.Focardi14 Piping: layout & connections Brazed connections along vacuum tank Top of cooling plant connections: -Reduced space and difficult routing -Wrong joints! no double ferrule, too big, no insert in copper pipes! They leak! All have been cured with Epoxy (which is reducing the leaks but not eliminating them!) Quality assurance protocol for brazed joints: 1)Qualification of manpower 2)2.5% of total tested, 2 samples on the most difficult geometry x week tested 3)Acceptance criteria: visual inspection, tensile test and Rm > 220 MPa, leak test 30 min 20 bar, burst test (>200 bar), metallurgical section: continuous ligament >3mm, total ligament. 5mm over 8 mm length

15. 25-11-08E.Focardi15 Manifold at the plant (1) shut-off Pneumatic shut-off valves Calibrated orifice flow rate measurement differential pressure. Calibrated orifice to allow flow rate measurement on the basis of the differential pressure. regulation Manual regulation valve to set flow rate Electronics Cold C6F14 Return C6F14 MAIN DISTRIBUTION LINESINGLE COOLING LOOPS

16. 25-11-08E.Focardi16 Manifold at the plant (2) Main difficulties encountered: Not trivial to find components compatible with the environmental conditions (magnetic field, radiation, fluorocarbon, low T) Tightness of different components: joints, plastic tubing crimped, Schrader valves Calibration of orifices: EN standards would ask for much bigger components, those installed had to be calibrated with C6F14 at different temperatures Operation: Safety valves: they have to be dismounted for a “line by line” leak test – vacuum testing cannot be performed since they are not tight in counter flow Differential pressure transmitter are pretty delicate Schrader valve inserts: they are delicate and tend to be deformed during connection/disconnection phases Crimped connection

17. 25-11-08E.Focardi17 P5 operation & experience Installation: commissioning the plants during the installation of pipes/detector is difficult. Testing of leak tightness –an overall measurement method has to be chosen –testing campaign to be done since the installation Instrumentation –Plant instrumentation: to be improved to reach a satisfactory monitoring level Instabilities – allow enough time for commissioning to reducce it during operation

18. 25-11-08E.Focardi18 Plants schematics and HEX Chilled water C 6 F 14 Chiller Detector cooling unit Tyfofit USC55 UXC55 First failure Nov 07

19. 25-11-08E.Focardi19 1 st failure (by chance) without tracker connected. All the system was contaminated by the mixture of water and salt. It took months to clean with no complete success. Water still was trapped inside the valves and other parts. When the system was restarted and we try to go low temperature the water clogged the heat exchanger. We had to stop the circuit and to start a new procedure of dry-out. The presence of the water is one of the most dangerous event that could happen. It can form fluoride acid that can destroy all metals. In the mean time several part of the circuit in the cavern were dismounted. We discover some unwanted grease and glue.

20. 25-11-08E.Focardi20 The condenser of the R507 fails and the water migrate on the chiller circuit. The condenser has the same mechanics of the other heat exchanger. The result of analysis failure said that the heat exchanger fails for mechanical stress. It was decided to change all heat exchangers of the circuits using commercial units from a well known producer: Alfa Laval, Honda…... Second failure May ‘08

21. 25-11-08E.Focardi21 Interventions during the first period. CHILLER UNIT -The condenser was replaced -The evaporator unit was replaced -Chiller unit: all the compressors were cleaned because full of water and oil -All the chiller circuit was dried -Distribution line in UXC55 -All line of SS2 were dried -All the heat exchangers were changed. -All the regulation valves were dismount, nipple were glued and gasket were added -All the pneumatic actuators were dismount twice -Most of the joint were glued -The connecting line between the reservoir and the circuit was changed to improve the air evacuation. (bigger line) -All the sealing of the schraeder valves were changed several times

22. 25-11-08E.Focardi22 Thermal performances 29 August 2008, Tracker run (TEC+ only), T coolant =13 °C TIB TID TOB TEC

23. 25-11-08E.Focardi23 Operation summary Primary plant was recommissioned and in operation since 12-th of June During TK checkout and commissioning: –Difficult temperature constraints due to high dewpoint in CMS cavern. –Too much air in the system Purging procedures are developed and applied. –High leak rate for Ss1 Several leaky points were found and sealed. Work in progress –Stability of Ss1 and Ss2 Improved after some changes in layout Some instabilities of the Primary plant during CRUSET 3 –Water pressure regulation valve is changed –Tuning of the regulation parameters During CRAFT (1 month of cosmic data taking) cooling plants tripped 9 times Last day: 1 pump motor burned

24. 25-11-08E.Focardi24 Temperature vs time

25. 25-11-08E.Focardi25 Pressure vs time

26. 25-11-08E.Focardi26 SS1 coolant level DateSs1 kg/day 25/07 – 28-0730 07/07 – 08/0715 After repair campaign 02/08 – 09/0815 20/08 – 25/0820 30/08 – 01/0925 12/09 – 15/0927 18/09 – 4 hours run50 14/10 –14/1125 after repair campaign repaired refill Cost: 50 CHF/kg

27. 25-11-08E.Focardi27 SS2 coolant level refill

28. 25-11-08E.Focardi28 Tracker Cooling Plants Upgrade Project Given the poor performances of the cooling system and trying to reduce the Fluid consumption (now, we spend 2500 CHF/day!!!) the Tracker group propose a plan to upgrade the system to increase the reliability of the Tracker cooling plants (mainly SS1 and SS2) given the limited access to the area. A plan is proposed for the next shutdown assuming beam in summer ‘09. The proposed plan gives a fair chance to have time to troubleshoot the plants before the shutdown end. 3 Main chapters have been addressed: Leak Tightness improvement. Air purging. Miscellanea.

29. 25-11-08E.Focardi29 S.S.- Cu Fitting connection. Partially glued. Fitting connection with NBR O-ring Crimped connections Cu-Cu brazed connection (a` la YB0). Redoing this connection allows also a better pipe layout on top. Brazed connection Fitting connection with metallic gasket Leak Tightness Main guidelines: Try to have brazed/welded connections as much as possible. Limit the use of plastics or elastomeric materials. Reduce or eliminate altogether the use of orifices on each line. Use orifices (already installed) or more sophisticated flowmeters only on the 4 main supply manifolds. Bring the cabinets with pipes to the surface and install the new piping there. Pre fabricate all the pipes and He test them. Only 1 brazing to be done in situ Foresee pressure pick ups on some supply lines (brazed schraders). Different flow control valve model

30. 25-11-08E.Focardi30 Air Purging Tank Return Manifold Pump Purge valve Move tank one floor up to statically fill the cooling plant to get rid of air trapped inside it plus improve the NPSHA on the plant. One bigger tank foreseen. Present Layout Elbow right off the pump supply Straight section Vac. Pump to remove the air and good control on the return pressure. Bring it outside the UX. Remove air effectively from the system protects the pumps and improves the stability of the plants operations. Avoids sending air to the Tracker which might cause air locks, unwanted vibrations and poor cooling performances.

31. 25-11-08E.Focardi31 New tank and distr. line components

32. 25-11-08E.Focardi32 If the present leak rate cannot be reduced, it’ s desirable to have the possibility to refill the plants remotely without being coupled to direct access to the UXC. Remote Refill system Take advantage of the “brine” system. Implement an independent system using flexible lines (multilayer pipe) easy to route from the CV room to UXC and a simple pumping station

33. 25-11-08E.Focardi33 Miscellanea (main items) PLC: revamp the whole control system to make it more reliable and user friendly. TS-CV will do it (already started). More convenient from the support point of view. Add instrumentation to improve monitoring. Monitor pressure drop and temperature across the exchangers, monitor pressure on the pump supply, pump return, return manifold and across the bypass valves, ….). This should include the “Brine” system as well. Test the cooling capacity with the present Hexs running in bypass and using the heater. –It will be performed at the end of the refurbishment. Complete the insulation boxes on top of the cooling plants.

34. 25-11-08E.Focardi34 Proposed refurbishment plan for next shutdown (Assuming beam in summer ‘09) Implement the plan for the leak tightness. –Disconnect the final distribution cabinets (to be done by our technicians), bring them on surface and install the already manufactured and leak tested copper pipes. The new installation to be done according to a new layout of pipes and manifolds in the cabinets and also to a better specified quality control procedure. A new layout of pipes on top of the cooling pant is under study. The goal is to avoid the “spaghetti bundle” layout. –While the cabinets are on surface, redo the pipes layout in the cavern as proposed above and possibly complete the leak search in order to verify if there are leaks downstream of the cooling plants. This will decide the priority for the implementation of the remote refill system. Air purge Work on the tanks and the cooling plants “core” on the balconies (to be done by an external company). Install instrumentation to improve monitoring (to be done by tracker techs and Cern services) Accomplish ALL the tasks in the miscellanea list. Implement the remote refilling system.

35. 25-11-08E.Focardi35 Cooling plants upgrade Org. Structure, Resources needed and Tasks E.Focardi Tk Tec. coord F. Raffaelli consultant

36. 25-11-08E.Focardi36 Resources Design phase (Engineers and Designers) from now through January. –2 Eng. from Cern –2 Eng. Equivalent from INFN-Pisa –1 Eng. from USCB –1 Eng. from Fermilab –1 Physicist INFN –2 Designers from INFN Pisa and Cern. Implementation phase (field coordinators and technicians) from January through May. –External contractor (Cosmi or Zec). –3 Techs equivalent from Cern. –2 techs equivalent from Fermilab. –1 Tech from USCB –4 Techs equivalent from INFN –4 Eng/Phys equivalent as field coordinators –Possibility to get an engineer from Italy (hired by Fermilab) to support TS. Cost Present estimate is about 500 - 600 KCHF. The bulk of the cost is the leak tightness (contractor labor and material) and possibly TS-CV involvement. Sharing: US ~200 KCHF+ manpower, Cern ~ 200 KCHF+ manpower Germany ~200 KCHF(on request), Italy: manpower

37. 25-11-08E.Focardi37 General schedule overview

38. 25-11-08E.Focardi38 Leak tightness improvement General Schedule No contingency in this plan Double shifts foreseen (realistic assumption if drawings and parts are available before the start of the implementation phase).

39. 25-11-08E.Focardi39 About 5.5 months available –2 months for design and parts procurement. –3.5 months for implementation. As the details will become more clear, schedule optimization will be possible. A CMS engineering review has been setup for Nov 26. By that time the different work packages, manpower usage and costs will be better defined. The integration of the final distribution should allow future possible improvements of the plant “core” (Heat exchangers, filtering system…). Set up technical reviews at the end of each design phase. A review of the new PLC system proposed by TS-CV will be held before the end of the year. General remarks