Subject: Re: [sdss3-25mlog 1330] Re: 2.5m obslog 20130718 (MJD 56492)
From: Kaike Pan
Date: Fri, 19 Jul 2013 16:50:17 -0600
On Jul 19, 2013, at 9:19 AM, Dan Long wrote:
> Hi Dmitry,
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>   Just to let you know, the secondary dewar (10L) pressure being zero =
will not be fixed by startfillseq. That command requests the camera =
dewars to fill from the 10L dewars.  If the pressure is zero in the 10L =
the primary fill will fail.  Hence the second alert of SP1LN2Fill Fault. =
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>   Forcing a fill on the 10L dewars by pushing the fill button on the =
silver autofill control box is the way to fix the problem if the reason =
for zero pressure is an empty 10L. =20
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>   With the lines hooked up it shouldn't have gone empty unless the =
sensor didn't trigger or the ground connection was bad.  Since you were =
able to force a fill on the 10L, it probably wasn't the ground.  It is =
strange that it would have gone empty since the interval between =
secondary fills wasn't abnormally long (about 13 hours),  so maybe the =
dewar pressure going to zero wasn't because it was empty (but it is the =
usual cause).  So the reason for the zero pressure on sp1's 10L is a bit =
of a mystery.
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> 		Cheers,
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> 		    Dan
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Sometimes, an extremely low pressure is seen after a primary fill is =
just finished and there is no more N2 in the 10L dewar.
-kaike
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