American Magnetics 430, Инструкции по установке, эксплуатации и обслуживанию

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R
EV
9
XIII
A
MERICAN
M
AGNETICS
, I
NC
. F
OREWORD
: G
ENERAL
P
RECAUTIONS
Metals to be used for use in cryogenic equipment application must
posses sufficient physical properties at these low temperatures. Since
ordinary carbon steels, and to somewhat a lesser extent, alloy steels,
lose much of their ductility at low temperatures, they are considered
unsatisfactory and sometimes unsafe for these applications. The
austenitic Ni-Cr alloys exhibit good ductility at these low temperatures
and the most widely used is 18-8 stainless steel. Copper, Monel
®
, brass
and aluminum are also considered satisfactory materials for cryogenic
service.
M
AGNET
Q
UENCHES IN
LH
E
-C
OOLED
S
YSTEMS
When an energized superconducting magnet transitions from
superconducting state to normal state, the magnet converts magnetic
energy to thermal energy thereby rapidly converting the liquid helium to
a vapor. When this phase transformation occurs, pressures can build
rapidly in the cryostat due to the fact that one part of liquid helium will
generate 782 parts of gaseous helium at STP (standard temperature and
pressure). The cryostat must be designed to allow the generated vapor
to rapidly and safely vent to an area of lower pressure. Cryostats are
designed with pressure relief valves of sufficient capacity so as to limit
the pressure transients within the container in order to prevent damage
to the vessel. Operating a superconducting magnet in a cryostat without
properly sized relief mechanisms or disabled relief mechanism is unsafe
for the operator as well as for the equipment. If there is any doubt as to
the sufficiency of the pressure relief system, contact the manufacturer of
the magnet and cryostat for assistance.
R
ISK OF
E
XPLOSION
Ensure cryogen container and/or magnet system vent relief valves are
kept clear
. An improperly ventilated cryostat/system may become
blocked by ice with subsequent RISK OF EXPLOSION and uncontrolled
release of cryogens from the system. Relief valves and rupture disks
may also discharge cold gas violently without warning. Relief valves
should always be pointed in a safe direction. Care must be taken not to
disable pressure relief devices or otherwise create a condition where
pressure buildup can occur in a magnet system or cryogen container
because of the RISK OF EXPLOSION. FAILURE TO HEED THIS
WARNING COULD RESULT IN INURY OR DEATH.
M
AGNETIC
F
IELDS
The following notices should be posted to warn personnel of the dangers
of strong magnetic fields produced by superconducting magnets:
i. WARNING: The operation of medical electronic implants, such as
cardiac pacemakers, may be affected by magnetic fields, WHICH
COULD CAUSE INJURY OR DEATH.