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    User name Olivier

    Log entry time 12:05:54 on June17,2000

    Entry number 44031

    This entry is a followup to: 43999

    keyword=Michael's answer about coolant pressure problem

    Hi target operators,

    the target seems to be fine, except:

    last night the operator observed that the 20K return pressure (PT83) was
    increasing. It should be about 45psi, within 12h it increased to 75psi.
    To be totally confusing, this minute it went back to 56psi.

    PT 83 is located just in front of the warm return valve, which is closed.
    I openened the warm return valve (don't do it, it was just and exercise
    for me), the pressure dropped to 42psi before I had to close again because
    the ESR temperature sky-rocketed.
    Cryo checked their line, they have resonable pressure readings of about
    2.8 atm, so they don't understand our problem. There are two
    possibilities:

    o our transducer got radiation damage. Hasn't happened with this one so
    far, and the reading increased very fast, so I don't know what to
    think.
    o we have an obstruction somewhere before the first reading cryo gets.
    I remember ice was observed on the outside of one of the flexible
    metal tubes just before the distribution box, but does this indicate a
    leak, and does vapor go in if 3 atm Helium are inside?


    Again, if it wouldn't be this pressure reading everything would be
    considered fine. There is no other indication something is wrong. We
    continue running, but please keep an eye on this reading and report
    significant increases to target on call, run coordinator etc. The return
    line is equipped with relief valves which open at 20 atm, I assume the
    pipe is tested for that, so even if the pressure is unusually high they is
    no immediate danger.
    Again, if the pressure is increasing significantly again (lets say by more
    than 20psi), inform target and run coordinator. The target is fine now,
    but if there is really an obstruction which is closing in time, we may get
    a problem.

    Good luck,

    Michael