Brooks On-Board 8, Installation And Maintenance Instructions Manual

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Cryo-Torr 8600 Compressor Operation, Installation and Maintenance Guide
©2013 Brooks Automation Inc. Pub. No. 8040564, Rev. AA, 01/15/13 ECO No. 64541 4-1
Section 4 - Maintenance
Helium Circuit Decontamination
The information in this section guides you through removing gaseous
contamination from an On-Board GLE Cryopump helium circuit by
freezing the contaminant in the coldhead of the On-Board GLE Cryopump.
A contaminated helium circuit will cause the On-Board GLE Cryopump to
operate in a noisy manner, typically referred to as
ratcheting , which
degrades On-Board GLE Cryopump performance.
Separate decontamination of the compressor is only required if the
compressor has been opened to atmosphere or the helium pressure in the
compressor has dropped to zero.
Three methods of decontamination are described in Table 4-1 and on the
following pages. These methods all have isolating gaseous contamination
in common by freezing them in one or more cold On-Board GLE
Cryopumps. The method to be used will most likely be determined by the
amount of time available for the decontamination.
Table 4-1: Methods of Decontamination
Method
Starting
Condition
Estimated Time
Effectiveness of
Decontamination
1. Cooldown and
Sequential decon-
tamination of all
On-Board
Cryopumps Requires all
On-Board
GLE
Cryopumps
to be cold. After all On-Board GLE
Cryopumps are cold, 45 minutes
to decontaminate the first On-
Board GLE Cryopump. 30 min-
utes for each additional On-
Board GLE Cryopump. Maximum
2. Decontamination
of only cold
On-Board
Cryopumps Only one
On-Board
GLE
Cryopump
needs to be
cold. 45 minutes to decontaminate the
first
cold On-Board GLE
Cryopump. 30 minutes for each
additional
cold On-Board GLE
Cryopump.
Acceptable