Servomex NanoTrace DF-760E, Instruction Manual

Page: 111 / 182

User Interface DF-760E 107
During normal operation the gas flow is constantly monitored by a flowswitch mounted in
the bypass loop that is set to trip when the flow drops below .1 lpm. In the event that flow
is reduced, the switch will automatically isolate the gas panel valves. In addition the
pressure reading will be forced to zero. When the system detects a zero pressure reading a
message will be displayed which states that backflow prevention is engaged and to check
sample and bypass flow. See Figure 119. The analyzer will remain in isolation and the user
will not have control of any valves at this point.
CAUTION
While the Back Flow Prevention System is engaged the moisture
reading is
not valid.
The user must determine the cause of the loss of gas flow and remedy the situation. When
flow has been restored to the analyzer the pressure reading will go to a non-zero value and
a message will be then appear stating that sample flow has been restored and to wait five
minutes to restore internal sample flow to the sensors. See Figure 120.
Figure 119: Back Flow Prevention Warning
A five minute timeline is displayed and the user will still not have valve control until the
five minutes are up. During this time, the
Esc key may be hit to cancel the five minute
delay and return control to the user. Once the Esc key is hit, or the five minute waiting
period has expired, all remaining messages are cleared from the screen and the system will
remain in isolation until the user restores flow. See page 103 for additional information on
restoring gas flow.
Figure 120: Re-established flow delay