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ISL Cooling Leak: ISL Cooling Leak: Cause and MitigationCause and Mitigation
Jose E. Garcia FNAL for ISL Task Force
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ISL Repair Task ForceISL 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
ISL/L00 Portcards
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CDF Silicon SystemCDF Silicon System
Jose E. Garcia FNAL
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ISL CoolingISL Cooling
• Cool sensors, readout electronics on detector (SVX chips) and nearby readout electronics (Portcards)
• SVX and ISL have independent cooling systems:– SVX (-10oC)
• Need to keep SVX colder to reduce impact of radiation damage• SVX 70/30 water/glycol
– ISL (+6oC)• 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
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Problem StartsProblem 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
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Co
nd
uct
ivity
3300
1200 700
8163 0.5
AU
G-0
6
MA
R-0
6
AP
R-0
7
MA
Y-0
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History ShortHistory Short
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• 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
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System DrainSystem 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/cm pH = 2.8
Jose E. Garcia FNAL
Drainings and pH obtained depending on the total of the
volume drained
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System Drain IISystem 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
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Conductivity vs AcidityConductivity 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/cm pH = 4.5
Our Lab Tests proved that Conductivy and pH are completely correlated.
pH
Co
nd
uct
ivy
(S
/cm
)
Conductivity pH
Jose E. Garcia FNAL
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AcidityAcidity
WE BROUGTH pH UP, BUT….
… WHY pH DECREASED IN FIRST PLACE???
Jose E. Garcia FNAL
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Source of AciditySource 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
ManifoldJose E. Garcia FNAL
• 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.
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Leaks in the ISL CoolingLeaks 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
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ShutdownShutdown
SHUTDOWN COMES…
…REPAIR IS PERFORMED…
Jose E. Garcia FNAL
Jose E. Garcia FNAL
Cooling Pipes
Manifold
Leaks
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ISL LeakISL Leak
Wire Chamber
COT
~28 inches
CO
T F
AC
ECOT FACECOT FACE
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ISL Cooling RepairISL 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 ft3 volume.
– Desiccant based air drier provided 300 ft3/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
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Repair…Repair…
Hole
Jose E. Garcia FNAL
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Ladder Cooling LinesLadder 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
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Corrosion StudiesCorrosion 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
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Instrumentation ImprovementInstrumentation 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. METERNEW FLOW METER
pH
pH has been kept during the shutdown well within
the safe range 4 – 6
Jose E. Garcia FNAL
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…AND THE SILICON…
Jose E. Garcia FNAL
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Silicon OperationSilicon Operation
BEFORE SHUTDOWN
Jose E. Garcia FNAL
BACK TO NORMAL
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SummarySummary
• 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
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…END…
Jose E. Garcia FNAL
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Aluminum CorrosionAluminum 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
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Leak GeometryLeak 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