Shutdown epi2 SNF 2008-11-02 11:33:00: Chamber A main scrubber fault - manual gas flows not allowed

shott at snf.stanford.edu shott at snf.stanford.edu
Sun Nov 2 13:34:20 PST 2008


The epi2 scrubber had indeed gone down as a result of the TGO MST 30 alarm this morning.
When I tried to restart it, however, it seemed to have problems .... the "double reset" only go the temperature up to 120 degrees C before it timed out.  Hitting it again got it about 15 degrees higher.
Repeating that a number of times finally got it up to about 230 degrees C (the interlock is set at 200) ...
but it would still not stay on.
So, I powered it down and cleaned the "flame sense" thermocouple.  While the manual claims that pulling it out, will remove most of the deposits, I cleaned it more thoroughly with Scotchbrite.  I also removed both ignition plugs which also had a certain amount of deposit on them.  I'm afraid that I don't know what is normal.  I looked for replacement plugs (which I know we have) but couldn't fine them.  So, as the next best thing, I covered the "outside part" of the plugs with a rubber glove and bead blasted the "in the line of fire" part of the plug.   The inner electrode is almost spherical in shape that leads me to believe that they should be replaced soon.  I don't know what our normal plug replacement interval is, but I think that we should review the frequency with which we clean the thermocouple and replace the plugs.  Also, looking into the main burn chamber, there is quite a bit of deposit.  I believe that it would be wise to carefully take that apart during the shutdown and clean it .... with the normal precautions in handling scrubber parts that are prone to spontaneously flash or ignite.
In any event, after cleaning the thermocouple and the plugs, the restart went much better .... it was up to an indicated flame temperature of about 360C within about 2 minutes and has stayed ignited.
As a result, I'm removing the shutdown on epi2.
Thanks,
John




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