108 Operation Manual
7 Resource Conservation
Resource Conservation
The 7890B GC provides an instrument schedule to conserve
resources such as electricity and gases. Using the instrument
schedule, you can create sleep, wake, and conditioning
methods that allow you to program resource usage. A SLEEP
method sets low flows and temperatures. A WAKE method
sets new flows and temperatures, typically to restore
operating conditions. A CONDITION method sets flows and
temperatures for a specific run time, typically high enough
to clean out contamination if present.
Load the sleep method at a specified time during the day to
reduce flows and temperatures. Load the wake or condition
method to restore analytical settings before operating the GC
again. For example, load the sleep method at the end of each
day or work week, then load the wake or condition method
an hour or so before arriving to work the next day.
Sleep Methods
Create a sleep method to reduce gas and power usage during
times of reduced activity.
When creating a sleep method, consider the following:
• The detector. While you can reduce temperatures and gas
usage, consider the stabilization time required to prepare
the detector for use. See Table 1, “Detector stabilization
times,” on page 18. The power savings is minimal.
• Connected devices. If connected to an external device
such as a mass spectrometer, set compatible flows and
temperatures.
• The columns and oven. Be sure to maintain sufficient
flow to protect the columns at the temperature set for the
oven. You may need to experiment to find the best
reduced flow rate and temperature. Also consider whether
the additional thermal cycling might loosen fittings,
especially for MS transfer line connections. In this case,
consider keeping the oven temperature > 110 °C.
•The inlets. Maintain sufficient flow to prevent
contamination.
•Cryo cooling. Devices which use cryo cooling may start
immediately using cryogen if the wake method requires it.
See Table 14 below for general recommendations.
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