Alarms
| Appendix E-9
Oven Heater Over-Temperature RTD Open [14]
The software monitors the condition of the Resistive Temperature Detec-
tor (RTD) that monitors heater temperature in the oven. If the device fails,
a Level 1 alarm occurs. This is a safety issue as the heater cannot be al-
lowed to exceed 200 °C and reach the auto-ignition temperature of pro-
cess gas. There are two redundant sensors in the heater.
User intervention is needed to clear the alarm condition. The RTD could
be defective or one of the three RTD wires may have been disconnected.
Manifold Pressure Alarm [15]
The Model 888 analyzer uses pneumatic control valves. The software
monitors the manifold pressure for these valves. The manifold pressure
alarm occurs if the pressure drops below the minimum operating pressure
for the valves. This alarm is a Level 1 alarm.
User intervention is needed to increase the manifold pressure above the
minimum limit. Adjust the pressure regulator on the manifold assembly.
Make sure there is a nitrogen or air supply as required in the manual.
Detector Temperature Alarm [16]
The detector assembly (883048901) includes a heated optical filter block. It
is maintained at a constant 40 °C. The filters are kept at an elevated tem-
perature to avoid humidity from compromising the filters. A Level 2 alarm
condition occurs if the temperature is out of the allowed range.
This alarm may indicate that the ambient temperature has exceeded 40 °C.
The detector assembly may need to be replaced if the ambient tempera-
ture is not above 40 °C and an alarm exists.
The analyzer will continue to operate normally if this alarm occurs.
Flange Temperature Alarm [17]
There is a temperature sensor mounted to the pipe flange on the oven en-
closure. If the temperature of the flange drops below the alarm set point,
there is a danger that sulfur deposits will occur within the probe. If left
unchecked, this will lead to a blockage. This is a Level 1 alarm.
This alarm is cleared by raising the temperature of the flange. Check the
insulation around the external ball valve and make sure there is sufficient
heat applied to the ball valve.
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