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

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Gas Bypass Control
System
4. Using the tie-wrap as a reference, pull the probes to the new level.
Caution If blue or black heat shrink tubing becomes visible when pulling
up wires, maximum height adjustment has been reached. Adjustments
above this tubing may cause LN
2
overflow. ▲
5. Route the sensor wires back over the red cap and reinstall the clamp.
Note On Vapor Phase settings, the high and low levels should be at least 2
inches apart. On Liquid Phase settings, the high and low level settings
should be at least 5 inches apart. ▲
The factory installed option Gas Bypass Control System (P/N 195021,
120VAC or P/N 195023, 230VAC) consists of a thermocouple sensor
located in the fill line, the fill solenoid, and the vent valve. Refer to Figure
4-1.
The Gas By-pass System works with the sensor to cause the warm nitrogen
gas to automatically bypass the storage tank and be vented to the
atmosphere (during the fill cycle).
At the start of the fill cycle, the sensor detects warmer nitrogen vapor in
the fill line coming from LN
2
supply source. The sensor causes the fill
solenoid to temporarily close, which causes the warm gas to bypass the fill
system and be vented to the atmosphere through the vent valve. This
prevents warm gas from entering the tank.
When the sensor detects colder liquid nitrogen in fill line, fill solenoid
opens, permitting LN
2
to flow into storage tank.
If cold liquid nitrogen is not detected in one hour, the unit goes into
Bypass Shutdown alarm. In this alarm state, the following occurs:
• alarms LED lights
• low level and high level LED flash
• audible alarm will cycle on and off
• all valves will close
• remote alarm contacts will activate.
To clear this alarm (after the alarm condition is corrected), the unit power
switch must be turned off, then turned on.
2-4 7000740r7 Cryo Series Thermo Scientific
Section 2
Operation
Sensor Adjustment
(continued)