Bruker BioSpin NMR Fourier 300, Site Planning Manual

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B127527_00_03
2 Safety
2.1 Introduction
In terms of safety the presence of a relatively strong magnet is what differentiates NMR
spectrometers from most other laboratory equipment. When designing an NMR
laboratory, or training personnel who will work in or around the laboratory, no other
feature is of greater significance. As long as correct procedures are adhered to, working
in the vicinity of superconductive magnets is completely safe and has no known harmful
medical side effects. Negligence however can result in serious accidents. It is important
that people working in the vicinity of the magnet fully understand the potential hazards.
Of critical importance is that people fitted with cardiac pacemakers or metallic implants
should never be allowed near the magnet.
The magnet is potentially hazardous due to:
• The large attractive force it exerts on ferromagnetic objects.
• The large content of liquid Nitrogen and Helium.
2.2 Magnetic Safety
A Magnetic Field surrounds the magnet in all directions. This field (known as the stray
field) is invisible, hence the need to post warning signs at appropriate locations. Objects
made of ferromagnetic materials, e.g. iron, steel etc. will be attracted to the magnet. If a
ferromagnetic object is brought too close, it may suddenly be drawn into the magnet with
surprising force. This may damage the magnet, or cause personal injury to anybody in
the way!
The Fourier 300 super conducting magnet is actively shielded. The following must be
understood when working with such a shielded magnet.
• The active shielding of the super conducting coil reduces the stray magnetic field
and therefore its effect. The
5 Gauss line in the horizontal direction extends
26.5 cm around the outside of the magnet. In the vertical direction it extends about
24 cm out of the can at the middle but it does not go above the helium stacks or
below the floor.
• In spite of the active shielding, the stray magnetic field immediately adjacent to the
bore of the magnet is very high and the attractive forces on ferromagnetic objects
are very strong!
2.3 Cryogenic Safety
The magnet contains relatively large quantities of liquid helium and nitrogen. These
liquids, referred to as cryogens, serve to keep the magnet core at a very low
temperature.
Because of the very low temperatures involved, gloves, a long sleeved shirt or lab
coat and safety goggles should always be worn when handling cryogens. Direct