7
Normal Blow Back Mode
Normal Blow Back Mode can only be accessed during Normal Mode and is an automated process which
occurs every 60 minutes. The time interval is user definable but is factory defaulted to occur every 60
minutes. Normal Blow Back Mode is used to blow high pressure air through the probe to clear it of any
dust or particles that could clog the sintered end of the probe and cause a low flow condition.
Low Flow Blowback mode
Low Flow Blow Back Mode can occur at anytime during Normal Mode. Low Flow Blow Back Mode begins if
the flow detector goes outside of its normal range and signals that there is a low flow condition. The Low
Flow Blow Back works just like the Normal Blow Back mode except that it is not a timed event and relies on
a low flow condition to start it.
Calibration Mode
Calibration Mode begins when the Universal Transmitter is put into Calibration by the user. All other
modes are disabled during this mode. The pump and solenoids are off and the flow detector reading is
ignored.
Maintenance Mode
Maintenance Mode should be entered by the user anytime that work is being performed on the system.
This will ensure that the scheduled blow back to occur every 30 minutes will not happen and the pumps
and solenoids will be turned off unless forced on by the user. Maintenance Mode is a useful tool for
trouble shooting and checking for proper operation of individual components. From this mode the pump
and solenoids can all be turned on individually. Other modes can also be selected from maintenance
mode to ensure they are working correctly. If the Sample Panel is left in Maintenance mode for longer
than 2 hours the (User selectable via HMI) PLC energizes the trouble relay and a signal is sent to the DCS
requiring that the error be acknowledged. This will ensure that the sample panel is not accidentally left in
maintenance mode.
Trouble Conditions
Low Flow alarm
The amount of gas flow to the sensor was too low and was not able to be restored to normal flow (2-
3LPM) after low flow blow back sequences.
Sensor fail
The calculated gas value has drifted negative by more than 3% of the monitors full range. A gas
calibration will typically correct this issue. If the sensor cannot pass calibration sensor replacement is
required.
