1. ISL Cooling Leak: Cause and Mitigation Jose E. Garcia  FNAL  for ISL Task Force All Experiments Meeting

2. 2 ISL Repair Task Force Jose E. Garcia  FNAL Del Allspach, Mary Convery*, Jose Enrique Garcia, Doug Glenzinski, Ignacio Redondo Fernandez*, Ulrich Husemann, C.M. Lei, Mike Lindgren, Aseet Mukherjee*, Bill Noe, Robert Roser*, Ken Schultz, David Stuart*, Bob Wagner, Peter Wilson *not shown in the photo

3. ISL/L00 Portcards 3 CDF Silicon System Jose E. Garcia  FNAL

4. 4 ISL Cooling Cool sensors, readout electronics on detector (SVX chips) and nearby readout electronics (Portcards) SVX and ISL have independent cooling systems: –SVX (-10 o C) Need to keep SVX colder to reduce impact of radiation damage SVX 70/30 water/glycol –ISL (+6 o C) Includes portcards for ISL/L00 on one cooling ring and SVX on a separate cooling ring ISL initially used distilled water, added 10% glycol in 2005 to avoid rare freeze condition Each system broken into ~10 cooling circuits on face of central detector with separate electronic control valves Operated sub-atmospheric: leak sucks air into system rather than pushing coolant onto detector or electronics Jose E. Garcia  FNAL

5. 5 Problem Starts Since March 2006: the conductivity of the ISL system went out of scale. –Several attempts to bring it down were not successful –Problem was investigated Beginning of 2007: ISL Cooling System degrades –During last month of 2006 the ISL cooling system became more touchy. After a trip or a power outage the flows used to operate the detector were not easily recovered. –At the beginning of 2007 some of the electronic valves started to fail. This problem got worse with time. Jose E. Garcia  FNAL

6. 6 Conductivity 3300 1200 700 8 16 30.5 AUG-06MAR-06 APR-07 MAY-07 History Short DrainDI Resin Now March 2006 ISL conductivity went out of range of the inline conductivity meter –Dashed line shows the estimated behavior of the conductivity –Numbers show measurements performed by external labs Problems were observed on e-valves in February – March 2007. pH measured on March was found to be ~ 2 (Vinegar). Problem was attacked!!! Jose E. Garcia  FNAL

7. 7 System Drain In March 2007, pH of the ISL cooling system was 1.9 and the conductivity 3300  S/cm. Treating the coolant with chemicals was discarded without a complete risk evaluation. Diluting and/or draining the system was the option chosen to obtain the desired coolant quality. This option will also remove the glycol from the system. 2 shifts access was requested to perform the draining of the around 700 liters contained in the system. The piping system was divided in several circuits and each of them was drained. Around 3 – 4 barrels of coolant were taken out of the system. Glycol was almost completely removed (less than 1% concentration remained in the system) Conductivity = 700  S/cmpH = 2.8 Jose E. Garcia  FNAL

8. Drainings and pH obtained depending on the total of the volume drained 8 System Drain II The first draining was successful but the pH achieved was still too low. The desired range for the pH was 4 - 6 Being pH a logarithmic scale leaving even a small amount of coolant (5 to 10%) decreases much the effect of the draining Final pH obtained was consistent with a draining of around 80% of the total system coolant (some of the legs in the pipes are difficult to drain). To obtain a pH around 4, two or three drains will be needed. The conductivity was also decreased by the dilution, but the coolant acidity questioned the effectiveness of the resin. Tests in lab showed that at pH ~ 2, the resin worked perfectly. But samples not only had a decrease in conductivity in addition pH increased. Jose E. Garcia  FNAL

9. 9 Conductivity vs Acidity We used a setup with 1/100 of coolant in the system to emulate the effect of a resin bed exchange on the ISL system. We tested the effect of several resin exchanges in the conductivity/pH in the system. Obtained a prediction of the quantity of resin needed to get the desired pH and Conductivity. We used a larger resin bed to decrease Conductivity and increase pH. Values obtained were: Conductivity = 8  S/cmpH = 4.5 Our Lab Tests proved that Conductivy and pH are completely correlated. pH Conductivy (  S/cm) Conductivity  pH  Jose E. Garcia  FNAL

10. 10 Acidity WE BROUGTH pH UP, BUT…. … WHY pH DECREASED IN FIRST PLACE??? Jose E. Garcia  FNAL

11. 11 Source of Acidity Formic Acid Acetic/Glycolic Ion chromatography analysis at Argonne National Laboratory showed carboxylic acids, mostly formic acid, as source of the low pH. Very likely that these acids came from the oxidation of glycol Al becomes vulnerable of corrosion for pH below 2 as Alumina becomes soluble. Corrosion resistance is alloy-dependent: –Heat affected zone around junctions in PortCard manifold most sensitive (alloy: 6061-Al). Less corrosion resistant junctions PortCard Ring Manifold Jose E. Garcia  FNAL

12. Coolant was successfully neutralized by draining (to 700  Si/cm, pH 2.8) and de-ionizing with resin (to 8  Si/cm, pH 4.5). Degradation on West portcard flows stopped after pH was increased. No additional flow problems with ladder lines. But… Welds of the aluminium rings which cool the optical transmitters (portcards) had already corroded. Since the system is sub-atmospheric, leaks result in lower flows. In May flow was too low to operate the portcards. 12 Leaks in the ISL Cooling Since May and up to the shutdown in August we were able to operate East ISL/L00 (affected 300 pb -1 ) Jose E. Garcia  FNAL

13. 13 Shutdown SHUTDOWN COMES… …REPAIR IS PERFORMED… Jose E. Garcia  FNAL

14. Cooling Pipes Manifold Leaks 14 ISL Leak Wire Chamber COT ~28 inches COT FACE

15. 15 ISL Cooling Repair Action was taken during 2007 shutdown. Important point during the operation was to keep the silicon cold and dry (annealing): – Plastic barrier encloses wire chamber bore, 600 ft 3 volume. – Desiccant based air drier provided 300 ft 3 /min to the volume. Dew point always below –10 C. Cover holes with epoxy from the inside of the pipe using borescopes and catheters Repairs performed over a month with 4 people shifts lead by FNAL specialist Ken Schultz. Vacuum tests show that the Al lines are as tight as the stainless steel ones (SVX system) Jose E. Garcia  FNAL

16. 16 Repair… Hole Jose E. Garcia  FNAL

17. 17 Ladder Cooling Lines Ladder cooling lines were investigated during the Bore access. Several lines were opened. –No corrosion was observed in the pipes –The epoxy used in the ladder cooling lines did not show any sings of degradation Vacuum in cooling lines is worse than on 2006 but no clear signs on the lines. epoxy Cooling lines Jose E. Garcia  FNAL

18. 18 Corrosion Studies Tests were performed to understand the corrosion process occurred in the system and to predict possible future problems. All test samples were immersed in acidic solutions at room temperature, visual inspection, mass loss, dimensional changes if any, were checked. 4 kinds of solution were prepared using 7 kinds of Al samples and samples of the epoxy used for the repair (DP190). pH of the samples was either 2 or 4, adjusted with formic acid. No significant mass loss was observed in the samples of the Aluminum immersed in a 4.5 solution Some loss was measured for some of the Al types in the acidic solution. More tests are ongoing Jose E. Garcia  FNAL

19. 19 Instrumentation Improvement During the shutdown improvements in monitoring and instrumentation have been implemented in the system: –Larger range conductivity probes (0 – 100  S/cm) –Flow switch in the DI circuit Better monitoring of the pH in the system: –Weekly samples taken: pH measured and recorded –Periods of high risk sampling increased to daily. Improvements and monitoring will continue. NEW COND. METER NEW FLOW METER pH pH has been kept during the shutdown well within the safe range 4 – 6 Jose E. Garcia  FNAL

20. 20 …AND THE SILICON… Jose E. Garcia  FNAL

21. 21 Silicon Operation BEFORE SHUTDOWN Jose E. Garcia  FNAL BACK TO NORMAL

22. 22 Summary ISL Task force will continue: –Corrosion studies will proceed analyzing the future behavior of the system –Instrumentation has been improved –Monitoring the pH will be done weekly –No further degradation observed in the lines ISL/L00 East have been recovered for data taking –The FULL system has been included on several runs/stores Jose E. Garcia  FNAL

23. 23 …END… Jose E. Garcia  FNAL

24. 24 Aluminum Corrosion Corrosion by acidic coolant Analysis by Argonne: 12.2g/L formic acid + 2.5g/L of either acetic of glycolic acid. Consistent with breakdown of gylcol (10% to 9%). Formic acid corrosive to Al At high concentrations (pH<~4) expect uniform loss At low concentration (pH>4) expect pitting corrosion In general, heat affected zones are more susceptible to corrosion Jose E. Garcia  FNAL

25. 25 Leak Geometry Cooling pipes Corrosion/leaks observed in Heat affected Zone of the welds Manifold - AL 6061-T6, 0.7 mm wall, 127 mm long tube 6 mm ID Cooling Rings - AL 5052, 5 mm wall, oval tubes (21 sided) Welded - either 5356 or 4043 filler Inner surface area: 0.12m2 Fed by Cilran (Silicon) tubing from COT face Impossible to access from outside, isolated by volume full of cables,~60cm in z. Jose E. Garcia  FNAL