Tile Cs hydraulic system issues

1. Oleg Solovyanov / Cs team Tile Cs hydraulic system issues Update and next steps

2. Oleg Solovyanov / Cs team The leak • 26 November 2013 a water leak from Tile Cs calibration system had occurred during the dummy capsule tests • The leak was identified with the help of an endoscope in one of the glued joints of calibration tubes of LBA26 Tile calorimeter module • Air pressure test confirmed the leak: 0.5 bar drop during 30 minutes = 45 mbar*l/s • Thanks to the LAr team a good access to the bad tube was provided quickly • The tube was cut away and a new one was glued in situ • One joint of the LBA29 has very old leak traces (circa 2007?) and has to be reinforced “just in case”. Waiting for LAr team to provide safe access to the joint

3. Oleg Solovyanov / Cs team LBA26 access (before cable removal)

4. Oleg Solovyanov / Cs team LBA26 tube gluing • Old tube was cut in the middle, then with the help of the heat gun the epoxy glue was softened and the tube was removed • A new tube was glued in place and reinforced by the glue outside of the joint, filling the hole in the endplate

5. Oleg Solovyanov / Cs team LBA26 cut tube • Examination of the cut tube suggested that the cause of the leak is the degradation of the epoxy adhesion to the stainless steel pipe • This is most probably due to the violation of the tube preparation (insufficient treatment/grinding of the inner surface). • For the moment this is the first case since 2007, but rather worrying

6. Oleg Solovyanov / Cs team Air pressure tests after LBA26 gluing • After the curing of the glue (couple of days) a long air pressure test was performed, it gave the leak estimate of 0.04 mbar*l/s (700 mbar for 25 days) • The second test gave 0.0025 mbar*l/s (<10 mbar for 150 hours), probably the small leaks were plugged by salt. • The EBA pressure test shows 0.012 mbar*l/s LB EBA

7. Oleg Solovyanov / Cs team EBA37 suspected leak • Following the small pressure drop in EBA a suspicious trace was found in the ITC region of EBA37 • Safe access to the suspected leak place requires scaffolding (balcony), waiting for TC to provide it

8. Oleg Solovyanov / Cs team Next steps 1/3 • Reinforce LBA29 tube once the access is provided, next week? • Check EBA37 for the suspected leak, need scaffolding • Finalize the implementation of the drainage piping of the Cs garages and garage leak sensors installation • Search for potential leaks using sniffer and tracer gas: Ar, CO2, R134a. Unfortunately the best tracer gas He will damage PMTs, so it cannot not be used

9. Oleg Solovyanov / Cs team Next steps 2/3 • Finalize the procedure of the air pressure tests before each Cs scan just before the water filling (what pressure, for how long, etc.) • Improve the pressure sensor system (optimize the range) • Improve the precision of the water level metering and implement the automatic alarm in case of a leak • Reduce the operating pressure to the bare minimum

10. Oleg Solovyanov / Cs team Next steps 3/3 • Study a more permanent approach to leak sealing from inside, construct the mockup from calibration straight and bent tubes for leak search and sealing tests • Evaluate the possibility to move the source with “negative” pressure, like in ATLAS leak-less cooling system • Have a new Cs hydraulic system follow-up and eventually a new review

11. Oleg Solovyanov / Cs team Leak-less system • Many experiments, including ATLAS are using so-called “leak-less” cooling systems • The main idea is to keep the pressure in the tube below atmospheric one • The holes in the pipe system will show-up as incoming air, but theoretically there liquid will not go out • Need to understand how one could modify the existing Cs system to run below the atmospheric pressure • A kick-off meeting with ATLAS cooling experts will happen tomorrow

12. Oleg Solovyanov / Cs team Garage refurbishing • All nine garages were removed from the cavern for refurbishing • New NBR rubber caps and O-rings were fitted • Garages were tested for few hundred opening-close cycles • LB and EBA garages were installed back • EBC garages to be installed soon

13. Oleg Solovyanov / Cs team Garage draining • To prevent runaway water in case of (improbable) leak of the garages, the garage housing was modified to provide water drains • Water will be collected via rubber hoses to the remote container • TC engineers will install and connect water leak sensors in each garage

14. Oleg Solovyanov / Cs team Pressure sensors • Cs system uses differential pressure sensors installed in the tee-connectors of the supply tubes, in the hydro-drive and water station • The MPX5700D sensor can measure positive pressure difference up to 7 bar • New modes of operation may require “negative” pressure difference, hence the need of an “absolute” pressure sensor • A set of such absolute pressure sensors, MPX5700A has been purchased and new sensors have been assembled and are under tests, first results are encouraging

15. Oleg Solovyanov / Cs team Water level meter • Water level in the hydro-drive is measured by optical sensor pairs and is known with 200 ml resolution • A new level meter based on magnetic pickup with four times better resolution of 50 ml is being designed • Need to confirm its stable working in the presence of a small magnetic field in the UX15 rack, 70-100 Gauss.

16. Oleg Solovyanov / Cs team Leak search with tracer gas • While the hole might be too restrictive for the water it will leak with gas, so one can search for “potential” leaks with a tracer gas, like Ar, CO2, R134a, or even He • Helium is damaging for PMTs, cannot be used • ATLAS cooling team lend us Inficon 3000 sniffer and R134a gas, doing tests in B.175 • TRT and RPC experts were contacted to help with CO2 and Ar sniffers

17. Oleg Solovyanov / Cs team Leak sealing from inside • Ideally one should reinforce all 4k tube joints with glue from outside • Big fraction of the Tile Cs piping system is hidden behind the LAr cryostat, LAr FE crates, ID cables, and not accessible • The other way is to seal from inside • In the past we successfully used a standard automotive radiator stop-leak gel, mixed with water and pressurized, but it is known not to last for very long time • More professional product Loctite Resinol RTC is used to seal pores in metal castings anaerobically. Henkel representatives were contacted and are helping us to understand if this product is applicable to our case • Other commercial product called ZORIC was successfully used by nuclear plants and particle accelerators to seal cooling leaks. The AMEC company was contacted to see if this product could be used here • The ideal fix would be to use a self-plugging mixture of demineralized water and some “leak plugging” additive during Cs scans • To test various approaches a special mockup of calibration tubes with joints is being constructed in B.175

18. Oleg Solovyanov / Cs team Summary • The last water leak from Cs calibration system resulted in a halt of Cs system re-commissioning • The location of the leak was identified in a tube joint of LBA26 module and the tube joint was redone • Latest air pressure tests show that the leak was fixed • Other suspected cases will have to be checked and reinforced • A set of additional measures is being studied and implemented • A study of “leak-less” implementation has been started • A follow-up and a eventually a new review is needed • Cs system is required to certify Tile drawers position