Thermo Scientific Cryo 740 Series, Руководство по эксплуатации и техническому обслуживанию

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2-2 7000740r7 Cryo Series Thermo Scientific
Section 2
Operation
Liquid Level
Controller
The Cryo Series liquid level controller is a three sensor liquid level
controller, with high and low level alarm capabilities. The liquid nitrogen
is controlled between the low level sensor, and the high level sensor.
When liquid nitrogen drops below the low level sensor, the solenoid valve
will be activated, and liquid nitrogen will enter the tank and fill to the
high level sensor. If the low level sensor is not immersed in liquid nitrogen
within ten minutes, the low alarm system will be activated. The low alarm
LED will illuminate, as will the Alarm indicators and an audible alarm
will sound. The Silence key pad will silence the alarm, but the LED and
Alarm indicators will remain on and audible alarm will sound every 30
minutes for as long as the alarm condition exists.
If the low level sensor is not immersed in liquid nitrogen within one hour,
the unit will go into low level shut down alarm. When in this alarm state,
the following occurs: high level LED (off ), audible alarm (cycle on and
off ), all valves close and remote alarm contacts activate. To clear this alarm
(after the alarm condition is corrected), the unit power switch must be
turned off, then on.
The high level alarm signals an overfill condition, and is activated when
liquid nitrogen touches the high level alarm sensor and remains there for at
least two minutes. The Silence key pad will silence the audible alarm, but
the High LED and Alarm indicators will remain on and audible alarm will
sound about every 30 minutes for as long as the alarm condition exists.
Both alarm systems activate relay contacts that can be interfaced with most
remote alarm systems.
The Cryo Series liquid level controller continuously monitors the integrity
of the three liquid level sensors and associated wiring harness. If any one of
the sensors or the wiring harness should fail (open circuit), the unit will go
into open sensor alarm. When in this alarm, the following will happen:
alarms LED (cycle on and off ), high and low level LEDs (off ), all valves
will close and remote alarm contacts will activate. To clear this alarm (after
the alarm condition is corrected), the unit power switch must be turned
off, and back on.