5-2 | Thermox WDG-V / VC / VCM with Blow Back
General Troubleshooting
Your system may pass calibrations, yet still seem to be reading incorrect
oxygen levels. If this is the case, you may want to check the following:
Leak Check
Leaks can lead to inaccurate readings, especially if operating under a sig-
nificant pressure or vacuum.
• Check that all compression fitting and pipe thread connections are
leak tight.
• Be sure that the mounting plate or mounting flange gasket on the rear
of the sensor is in place (see the “Sensor Mounting” section in Chapter
2 for details on the placement of the gasket).
SnifngforLeaks
For processes under vacuum you can check for leaks by sniffing the fit-
tings with another gas (for example, nitrogen or pure oxygen), being sure
to avoid the area over the top of the cell.
1. Use a piece of tygon or plastic tubing with a 1/8” stainless steel nozzle
to apply the gas from a cylinder (using stainless steel prevents any
problems that might occur with plastic melting the nozzle on hot sen-
sor components).
2. Monitor the response from the cell. When the cell millivolt reading
changes, it indicates a leak in that area of the plumbing (the vacuum
of the process pulls in the gas).
3. If not convenient to view the AMEVision display, you can also apply a
voltmeter to the Cell terminals on the sensor board labeled (+O2-) to
see if the cell millivolts change, indicating a leak.
Pressurizing for Leaks
1. Remove the sensor from the process (after allowing sensor to cool)
and pressurize it with 5 lbs. of air, plugging any exiting ports, the inlet
probe, and exhaust tube holes. Then go over the sensor fittings with a
leak detector fluid.
2. If you see bubbles, it indicates a leak. If using this method be sure to
prevent the liquid from reaching the furnace. If the furnace does get
wet, allow it sufficient time to thoroughly dry.
To Next Page
Loading...
Need help?
General
