Hi Sameer
First of, congrats on your building upgrades ! My thoughts are :
* The legs can be down. They are needed only for filtering out floor
vibrations when spectroscopy is done. When in sleep mode, its better to
leave the magnet on its rigid support base. But, ff there are
substantial floor vibrations due to construction, it's a tempting idea
to keep the legs elevated but, recall that the legs are good at
dampening only high frequencies. If possible at all, you can use an
accelerometer to get a measure of floor vibration during construction
start and decide. Even a smart phone app might be a handy poor-man's
choice for this !
* Once again, I don't expect the room temperature fluctuation to do
anything adverse to the magnet's quiescent state. Barometric pressure
variation can change the Helium boil off rate. But I don't know if HVAC
systems do anything about this (some chemistry labs have air handler
systems that keep a high pressure differential compared to the corridor;
apparently this is done to avoid any toxic spillage from spreading).
Also, I will simply setup a routine fill cycle of Helium based on the
history and just fill the magnet, without bothering about Helium gauge,
etc. On one of my old 500-s I have even removed the faulty Helium
sensor completely and I am just filling the system routinely. Nothing
is amiss so far. The only useful thing I keep an eye on is the flow
gauge because that gives me a direct measure of how the magnet is
behaving on a daily basis.
* As to the stray field, I can't say because all my magnets are located
in the basement. But, ours being an old building, we have 20 ft
ceiling and so stray field on the floor above was never an issue, even
with old magnets.
* The only other X-factor is this. Please put the fear of god in every
one of the construction team so that they don't wander with a wrench or
spade or similar closer to the proximity of the magnet. If at all
possible, make your enclosure out of good plywood with an access door
for Helium fills, that can be locked. Since there are no heat
dissipation requirements for the magnet, it may not be a bad idea to
cover the top portion of the magnet with plastic sheeting, if you expect
any 'man made rain' as part of construction activity.
Good Luck and let us know how it went, in six months !
Regards
Rajan
On 11/14/2016 08:36 AM, Sameer Al-Abdul-Wahid wrote:
>
> Hello Spinlanders,
>
> I wanted to please ask your experiences and thoughts regarding keeping
> magnets at field during a 5-month building closure.
>
> During the closure, all the building utilities will be renovated and
> we will have no electricity, ventilation/AC, or compressed air. As to
> vibrations, I expect drilling through concrete but no major structural
> demolitions. Our NMR lab (unshielded 400, shielded 500 and 600, all
> Bruker) is on the third floor.
>
> The project team is leaning towards keeping the magnets at field. We’d
> have weekly access for cryogen fills. The magnets would be fenced off
> at their 5 Gauss lines and covered with plastic to protect from dust.
>
> I am still unsure of the following:
>
> - Outdoor temperatures range from 32C/90F to 15C/60F and the
> humidity ranges from 60-90%. Without ventilation/AC I expect our lab
> to be quite warm and humid. Aside from increased nitrogen boil-off, is
> there anything else I should expect?
>
> - Is it safer to keep the magnet legs ‘up’ using compressed
> air cylinders, or keep them down?
>
> - The stray field plot for our 400 indicates ~35 Gauss for
> ceiling of the second floor (i.e. below the magnet). Any horror
> stories on work done on the ceiling below a magnet?
>
> - Has anyone used a Bruker Zurich magnet with a standalone
> helium sensor like the Magnex E5011? Our SLCB-based sensors won’t have
> power.
>
> - Any other “X” factors that I haven’t foreseen?!
>
> Many thanks,
>
> Sameer
>
> --
>
> Sameer Al-Abdul-Wahid, Ph.D.
>
> Manager, Nuclear Magnetic Resonance Centre
>
> University of Guelph
>
> 50 Stone Road East, Guelph, ON N1G 2W1
>
> Tel: 519-824-4120 x58914 <tel:519-824-4120%20x58914>
>
> Web: http://nmr.uoguelph.ca/
>
--
____________________________________
____________________________________
Rajan K Paranji, Ph.D.
NMR Facility Manager
*Department of Chemistry*
*Room 65, Bagley Hall*
University of Washington
Seattle, WA 98195
phone : 206 685 2581
fax: 206 685 8665
email: rajanp_at_uw.edu
____________________________________
Received on Mon Nov 14 2016 - 09:50:45 MST