# Presentation: 571463

## ISL Cooling Leak: 

**ISL Cooling Leak: **
**Cause and Mitigation**

***Jose E. Garcia  **********  FNAL *** ****

_***for ISL Task Force***_

**All Experiments Meeting**

## ISL Repair Task Force

**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**

## CDF Silicon System

- ISL/L00 Portcards

**CDF Silicon System**

***Jose E. Garcia  **********  FNAL***

## ISL Cooling

**ISL 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***

## Problem Starts

**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***

## History Short

- Conductivity

- 3300

- 1200

- 700

- 8

- 16

- 3

- 0.5

- AUG-06

- MAR-06

- APR-07

- MAY-07

**History Short**

- 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***

## System Drain

**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/cm****	****pH = 2.8**

***Jose E. Garcia  **********  FNAL***

## System Drain II

**Drainings and pH obtained depending on the total of the volume drained**

**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***

## Conductivity vs Acidity

**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/cm****	****pH = 4.5**

- Our Lab Tests proved that Conductivy and pH are completely correlated.

***Jose E. Garcia  **********  FNAL***

## WE BROUGTH pH UP, BUT.... 

**Acidity**

**WE BROUGTH pH UP, BUT.... **
**... ****WHY pH DECREASED IN FIRST PLACE???**

***Jose E. Garcia  **********  FNAL***

## Source of Acidity

**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***

## Leaks in the ISL Cooling

- 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.

**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***

## SHUTDOWN COMES... 

**Shutdown**

**SHUTDOWN COMES... **
**...****REPAIR IS PERFORMED...**

***Jose E. Garcia  **********  FNAL***

## ISL Leak

***Jose E. Garcia  **********  FNAL***

**ISL Leak**

## ISL Cooling Repair

**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 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***

## Repair...

**Repair...**

**Hole**

***Jose E. Garcia  **********  FNAL***

## Ladder Cooling Lines

**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***

## Corrosion Studies

**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***

## Instrumentation Improvement

**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.

**pH has been kept during the shutdown well within the safe range 4 – 6 **

***Jose E. Garcia  **********  FNAL***

## ...AND THE SILICON...

**...****AND THE SILICON...**

***Jose E. Garcia  **********  FNAL***

## BEFORE SHUTDOWN

**Silicon Operation**

**BEFORE SHUTDOWN**

***Jose E. Garcia  **********  FNAL***

## ISL Task force will continue:

**Summary**

- 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***

## ...END...

**...****END...**

***Jose E. Garcia  **********  FNAL***

## Aluminum Corrosion

**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***

## Leak Geometry

**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***