CAT Chat Minutes

February 17, 2003


Information and Follow-up

Thomas Gog questioned the status of the ODH response procedure when alarms go off in enclosures.

Bill Wesolowski answered that one does not know the nature of a leak or how severe it might be, and that is why access is denied under the present policy. The reason for Control Room response is that there is always an operator present at the facility, even during maintenance periods. There was concern expressed that the mono would run out of LN2 supply if the drop valve was closed. See attached comment from Bill explaining that there is at least a 2-3 hour supply of LN2 remaining, and the ODH response should be completed well before this time limit. E. Chang, Bill and Roger are reviewing the present policy to consider a visual check by Floor Coordinators or Operators wearing proper PPE before calling 911. The safety concern is that there can be entry into a hazardous oxygen-deficient environment by untrained personnel. There will be more information on the results of this review in future.

Reinhard Pahl asked about the procedure for cleaning up spilled water inside and outside enclosures on the APS experimental floor. Apparently, custodians first call in HP techs for a survey before cleaning up a spill. Reinhard has asked that we defer discussion of this until March 3rd CAT Chat.

We will have P. K. Job, radiation specialist, come to CAT Chat and present information/clarification.

D. Keane asked why he cannot access an archive tool to look up logs of PV orbit values on the web. At one time he used to look up orbit parameter history which was beneficial to his research. Available also were live displays indicating pressures, beam current, etc.

Glenn Decker, Ned Arnold, and John Carwardine are standardizing the PV logging using OAG toolkit. The data is still being logged, and floor coordinators can presently generate these logs for users. Glen will address this at the February 24th CAT Chat.


User Operations

There were no reported user problems with running at 112 ma top-up beam. A number of users asked if we could continue to run 112 ma.

There was concern that the higher current operation may have been connected with RF4 trips on Saturday. It turns out that recent studies have demonstrated that the RF4 klystron requires tuning to avoid a region where sidebands become a problem. This should have nothing to do with 112 ma operation, and is more related to the age of the klystron.

Beamline Faults:  Roger Klaffky reported that there were six beamline faults recorded by floor coordinators during the period 2/7-14/2003. 

2/07/2003 (11:06) Chilled water flow/pressure interruption 0 hrs., 5 mins. PFS
2/07/2003 (11:06) Chilled water flow/pressure interruption 0 hrs., 5 mins. PFS
2/07/2003 (18:22) Front End pressure loss (bad relay) 1 hr., 55 mins. ES/PSS
2/12/2003 (14:05) Improper operation of mode shutter 0 hr., 45 mins. User

Comments on ODH/LN2 hazards B. Wesolowski:  Normal fill of the cryo-pump "vessel" is at a level of 40%.  When the LN2 drops to this level, the vessel is re-filled to 60%.  This takes two to three hours (depending upon the ID gap) before the level again drops to 40%.  (NOTE: the LN2 drop valve is always open.  It is the cryo-pump solenoid valve that is opened and closed as determined by the level in the vessel.)  At the 40% level, the heat exchange coil of the high pressure side is fully submerged in the LN2 bath.  If it is at this level when the LN2 supply valve is closed (worse possible case), it would take about an hour for the level to drop to about 32% (most of the heat exchanger coil of the high pressure line would still be submerged in LN2).  Closing the LN2 drop valve does NOT stop the pump operation.  Only in the case where the LN2 drop enters the enclosure, if there is an ODH alarm which calls for closing the LN2 drop valve, responding and ascertaining the cause would take about a half hour.  The monochrometer would continue to be cooled; there is sufficient LN2 level in the vessel so that the cryo-pump system itself would not over pressurize.  If there truly was a breach in the liquid lines in the enclosure, the LN2 drop valve would have to be closed regardless.  If it was determined that it was a false alarm, the LN2 drop valve can be re-opened and remedial action would take place.  In the case of sector 5 and sector 9, possibly others, the LNDS fills a 160 liter dewar which in turn fills the cryo-pump vessel.  This gives a reserve supply, so that with this method, the LN2 drop valve could be closed for several hours without affecting the system.

Provided that cryo-pump and dewar vents are piped to the outside of the enclosure  (piping capable of tolerating LN2 temperatures -minus 170 degrees C - are to be used) and/or adequate ventilation is provided, the occurrence of an ODH alarm would be minimized and the occurrence would be due to a breach in the system that would allow LN2 into the enclosure.  If LN2 is spraying, one would not want untrained, unprotected personnel accessing the enclosure, and since this possibility could exist 24/7 (even during maintenance periods, off normal hours, the only personnel always available are the MCR personnel and the fire dept. personnel who are prepared to handle these situations).  It is more important to save a persons sight since unprepared opening of the door could be such that liquid spray could strike some ones eyes.  The pneumatic door opens fully; one cannot limit travel.  Ones inconvenience does not justify exposing someone to either a LN2 spray hazard or an oxygen deficient environment hazard.  The procedures are being reviewed and, tentatively, MCR personnel and Floor Coordinators will assess the need for making a 911 call by first inspecting the hutch.

Additionally, there are specialized cases where the beam-line personnel have extended the LN2 lines to provide drops to multiple enclosures.  This usually entails a beam-line solenoid valve operating to fill a 160 liter dewar which in turns fills another dewar which provides cold gas to cool the sample under study.  These are being looked at on a case-by-case basis with EFOG providing assistance.