AMMRLers,
Some months ago I posted to the group on this topic. I received a few responses
(thank you to Dean, Gary, Tanya, Pedro, Simon, Tuomas, Bob, Ryan, Jonathan,
and Johnny). The responses generally fell into two categories:
One category was categorically against allowing these sort of lifts in the
lab (most responses); suggesting to request an exception or use aluminum
scaffolding for the job.
The other category suggested that it might be okay, staying outside the 5 G
line, and pointed out that while shielded magnets reduce the horizontal stray
field, the vertical stray field is still considerable. One suggestion was
to put a sample in the magnet and lock it, and monitor the lock level. A
perturbation in the magnetic field results in a reduction in the lock level,
which can be used as an indicator.
The category that was conspicuously absent was one saying, "we did this and
it turned out (OK / bad)". To this end, I add this category to the record,
and it turned out good.
Details:
None of the lights are directly above the magnets, though one is very close
to an Ascend 400.
Having a scaffold set up was going to be very costly, and would require a 3rd
party to do it. Our in-house facilities guys are very conscientious, but
third party contractors are an unknown.
We used a Genie AWP-20S lift. This lift is mostly aluminum (including the
mast,outriggers, and the worker platform/railings); the base (up to about 6"
from the floor) is made of steel, as is a plate on the back of the mast. As
we moved the lift nearer to the magnets, I paid attention to the lock level.
We got to around the 2.5 G line of the UltraShield 400 magnet, and I noticed
no effect on the lock level at all. We were around the 1 G line of an Ascend
400 magnet, which seems unnervingly close; but again there was no effect
observed on the lock level. I will note that we positioned the lift so that
the motor and steel plate of the mast were furthest from the magnet.
Steve
-----Original Message-----
> From: Steven Clemens
> Sent: November 20, 2020 09:26
> To: ammrl_at_ammrl.org
> Subject: Using personnel lifts (eg. JLG lift) near supercon magnets
Greetings, all.
Our lab has high ceilings and we have a few lights burned out, some are somewhat
near our magnets. Our maintenance folks used to use a big aluminum
ladder to reach these, but rules have changed about the height at which fall
protection is required so the ladder is no longer an option.
They want to use a lift like this: www.jlg.com/en/equipment/vertical-lifts/driveable-mast-boom/copy%20of%2020mvl-driveable-vertical-mast-lift
Does anybody have experience with use of lifts like this near NMR magnets?
How close did they get to your magnet? Two of our magnets are Ascends,
so they wouldn't be anywhere near the 5G line, but one is an Ultrashield,
so they'd be probably around the 3G line.
Thanks,
Steve
Received on Wed Mar 31 2021 - 06:11:28 MST