Subject: Re: [sdss3-25mlog 1861] 2.5m obslog 20140825 (MJD 56895)
From: Dan Long
Date: Tue, 26 Aug 2014 10:27:32 -0600
Hi Dmitry and Patrick,
   The dewar you took off and put in the shed seems fine.  There is no =
leak and the pressure built back up to ~20 psi, which would indicate =
that the pressure relief is working properly.
   When you say =93leaking from a valve not involved in filling=94 are =
you saying that the leak wasn=92t anywhere in the liquid line?  If so, =
where did you see the leak?
   Since the plot showed not only pressure but significant weight loss, =
there was liquid escaping somewhere.  Were you meaning that liquid was =
coming out from the line even though the 10L wasn=92t being filled?
   The dewar you put on it its place had a serious leak at the =
connection to the 10L (it lost something like 50 lb during the night).  =
We thawed out the line, and dried the connector of the fill line and 10L =
connection.  When hooked back up it didn=92t leak and filled normally.  =
I suspect there must have been some ice on the connector or gasket that =
was preventing a good connection (and that might have been true of the =
first dewar as well if the leak was in the same place).
-Dan
On Aug 26, 2014, at 5:03 AM, dmbiz@apo.nmsu.edu wrote:
>=20
>                       APACHE POINT OBSERVATORY SDSS 2.5M
>=20
>                                 OBSERVING LOG
>                          Monday August 25, 2014
>=20
>                                  (MJD 56895)
>=20
> ----  Observing Team ----
>=20
> Patrick Gaulme
> Dmitry Bizyaev
>=20
>=20
>=20
> ---- Observing Plan ----
>=20
> MaNGA Observing plan for night of Aug 25
>=20
> Plate 7991: Visibility window LST 14:46 - 19:55, UT: 23:36 - 4:45
> Obtain as many dithered exposures as possible until UT 4:45
>=20
> Plate 8069: Special all-sky plate, take two 15-minute exposures (no =
dither=20
> required) between LST 21:00-0:06, UT: 5:50-8:56
> Special Instruction: Because MaNGA's two carts cannot fill the 5.1 =
hours of MaNGA=20
> time, after 7991's window expires, switch to an eBOSS plate. Then =
return anytime=20
> between UT 5:50-8:56 to MaNGA plate 8069 to obtain two 15miniute =
non-dithered=20
> exposures. Then continue with other eBOSS plates.
>=20
> ---- Observing Summary ----
>=20
> Note: dewar on sp2 is leaking from a valve not involved into filling. =
This leads
> to low pressure causing non finishing sp2 filling.=20
> We replaced the dewar while it was cloudy.=20
> The leaking one is on the dewar cart in the LN2-room, to let you find =
it easily.
> At the moment of replacement its weight was ~180 lbs.
> New dewar leaks, too, close to the quick connector, but less intense.=20=
>=20
>=20