CHART MVE 1842P-150, Руководство по эксплуатации и техническому обслуживанию

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MVE Biological Systems
TEC 3000 Operating and Maintenance Freezer Manual
13289499 Rev H •
44
7.1.11. Hot Gas Bypass
The Hot Gas Bypass is a feature on HE/MVE/HEco freezer series equipped with a TEC 3000.
The Hot Gas Bypass is able to vent the warm nitrogen gas from the supply line before initiating
a fill cycle. This prevents warm gas from entering the freezer space. The bypass system helps
to maintain a stable temperature gradient inside the freezer and increases the efficiency by
preventing excess LN2 evaporation while filling. This feature is advantageous for any freezer
setup and is especially ideal for sites where longer transfer hoses cannot be avoided.
The Hot Gas Bypass system consists of these components:
•
Solenoid Valve (24 VDC)
•
Temperature sensor (Pt-1000 RTD)
•
Muffler
•
Plumbing and electrical connections
Freezers with the Hot Gas Bypass installed and enabled will complete a bypass cycle prior to
filling. When a fill is initiated, the bypass solenoid valve will open first and begin venting
nitrogen gas from the supply line through the muffler and into the atmosphere. The TEC 3000
monitors and displays the temperature in the plumbing system throughout the bypass cycle. As
LN2 begins flowing, the temperature in the plumbing system will decrease. Once the bypass
temperature sensor readings reach the user-defined Bypass Temperature Setpoint, the bypass
solenoid valve will close terminating the bypass cycle. The fill solenoid valves will then open
and the freezer will begin filling. The default Bypass Temperature Setpoint is -70°C and can be
adjusted based on the freezer setup.
The Bypass Alarm Time Delay is the maximum allowable bypass time. If the temperature in the
plumbing system does not reach the Bypass Temperature Setpoint within the Bypass Alarm
Time Delay setting, the TEC 3000 will terminate the bypass cycle, initiate the fill cycle, and
trigger a Hot Gas Bypass Time Alarm. Once the immediate fill cycle is complete, auto fill will be
disabled until the Hot Gas Bypass Time Alarm is acknowledged. This feature prevents a freezer
from continuing to attempt to fill from an empty supply. A Hot Gas Bypass Time Alarm could be
a sign of an empty supply, a supply with too low of pressure, or it could mean that the Bypass
Alarm Time Delay needs to be increased in order to effectively purge the supply line of nitrogen
gas. The default Bypass Alarm Time Delay is 5 minutes, but should be adjusted based on the
freezer setup. It should be arranged so that the Bypass Temperature Setpoint is easily reached
within the Bypass Alarm Time Delay setting.
NOTE: If a Hot Gas Bypass Time Alarm is triggered, once the immediate fill cycle is
complete, auto fill will be disabled until the alarm is acknowledged.