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OPERATING
INSTRUCTIONS FOR ELECTRIC PRESSURE
BUILDING SYSTEMS
To
avoid damaging container and/or heating element, turn power
off immediately after transfer is complete. Never operate
the electric pressure-building system in any empty dewar or
in open air.
Single
Set Point Models
Prepare
the dewar for normal withdrawal as described in "Operating
Instructions for Model CMSH Multishielded Liquid Helium Containers".
Plug power cord into an appropriate outlet and turn power
switch on. Pressure in dewar will start to rise shortly. If
the transfer line has no shutoff valve then liquid will start
to flow as soon as the pressure in the dewar rises to a sufficient
value. The pressure will continue to rise until it reaches
the nominal set point. A built-in pressure switch will automatically
maintain the pressure at the set point for the remainder of
the transfer. When the dewar is empty, turn off the power
and unplug the power cord.
NOTE
When
the electric pressure-building system is operated in a full
dewar the pressure may build very rapidly upon initial turn-on.
Even though the heating element is automatically switched
off at the set pressure, there may be a pressure overshoot.
This is normal. As transfer continues, the pressure should
drop down near the nominal set point and oscillate slightly
for the remainder of the withdrawal.
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