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TCS Chiller Performance Review

Phil Willems

Nov. 17, 2004

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Design Requirements

Device Max power dissipated Flow requirement Source of requirement

Carbon dioxide laser 80W ½ gpm Access Laser Co.

Laser power supply 40W ‘cool to the touch’ Access Laser Co.

AOM 30W 250 ml/min IntraAction, Inc.

AOM driver TBD TBD IntraAction, Inc.

1. Laser temperature: around room temperature, ±.5K2. Flow rates:

3. Noise: acoustic and EMI must be under ambient at nearest sensitive device (optical lever system)

4. Monitoring and control from control room using EPICS 5. Leak tight and robust

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Commissioning Timeline

Device was installed on 2K Y arm Oct. 27-29 Device was commissioned from Oct. 29 to Nov. 8. Commissioning paused after overheating incident

Nov. 6-7. Forensics from Nov. 8 to today.

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Installation

Site chilled water delivered to chiller from over 100 feet away through uninsulated copper pipe» This may account for some temperature issues and surges during

control valve operation

Site chilled water and TCS table water pipes interlaid and touching» Insulation of TCS table supply pipe required for temperature

stability

Prototype control electronics not plug and play Control software implemented but not safety

interlocks

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Commissioning

Submerged thermistor failed after 2 days (Nov. 1)» Thermistor was fine; problem later traced to bad solder joint outside

chiller

» Short term solution was to glue another thermistor to pipe leaving chiller

Laser power stabilized without AOM on (Nov. 3-5) Laser power unstable with AOM on (Nov. 5) Chiller noise performance verified (Nov. 6-7)

» http://blue.ligo-wa.caltech.edu/ilog/pub/ilog.cgi?group=detector&date_to_view=11/07/2004&anchor_to_scroll_to=2004:11:07:22:32:32-robert

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Overheating Incident

After noise test, chiller was switched on to run overnight

Apparently, one or both pumps failed to switch on System ran at very high temperature for about 1-2

days Much damage and corrosion to the chiller Thermistors on TCS table showed no overheating, no

flow to table- TCS table not affected

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Why a Chiller Is Not a Boiler

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Overheating Incident Analyzed

Without submerged thermistor operating, no way to monitor chiller reservoir temperature

Without software interlocks programmed, system could not power down safely had the submerged thermistor worked» Had system been fully operational before running unattended chiller

would have safely shut itself down

Why did pump fail to start?» LHO reports that all Rio pumps studied failed to start 100% of the

time

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Forensics

Chiller disassembled, analyzed, and rebuilt» Now it runs well even with the AOM on (for 30 minutes at least…)

Rio 1100 pumps tested for reliability» One pump tested by hand- 200 starts without failure

» One pump tested by robot- robot itself not 100% reliable, but pump starts ~15,000 times without failure

» Rio 2100 pump known to fail at LHO now under test

Coolant corrosion tests» Chloramine T not compatible with chiller components under

accelerated aging test

» Propylene glycol and sodium hydroxide are compatible

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Chiller Performance After Rebuild

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Final Results Compared to Requirements

1. Temperature of chiller and laser held to within .5K, as required

2. Flow rate is 1.3GPM, as required3. Acoustic and electromagnetic noise is below

ambient, as required4. Operation fully controlled and monitored from the

control room, as required5. System is not yet robust to failure modes

Design not fully implemented, software interlocks missing when needed

New safeties can be added without change to conceptual design

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Are the Design Requirements Good Enough?

• The TCS laser stability is unverified even though the TCS chiller meets requirements. Laser power and coolant temperature fluctuations are frequently correlated.• Is .5K temperature stability sufficient?• Is 1.3GPM flow sufficient?

• Recommend that no more TCS chillers be installed until reconditioned prototype performance is verified. • New chiller parts will replace boiled parts• Software interlocks will be fully implemented• Hardware interlocks under consideration• Plan new commissioning effort Nov. 29-Dec. 3.