General Troubleshooting - Ametek Thermox 2000 ATEX Series User Manual

General Troubleshooting

6-16 | Thermox Series 2000 WDG-HPII / HPIIC - ATEX
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. Also be sure that the mounting plate or
mounting flange gasket on the rear of the sensor is in place (see the "Sen-
sor Mounting" section in Chapter 2 for details on the placement of the
gasket).
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. 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 sensor components). 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). If not
convenient to view the control unit display, you can also apply a volt meter
to terminals 1 and 2 on the sensor board (Cell + and Cell -) to see if the cell
millivolts change, indicating a leak.
If you want, you can also remove the sensor from the process (after allow-
ing 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.
If you see bubbles, it indicates a leak. If using this method be sure to pre-
vent the liquid from reaching the furnace. If the furnace does get wet,
allow it sufficient time to thoroughly dry.
Plugged Plumbing Check
Exercise care when working on the sensor. Allow the unit to cool
!
and wear gloves.
CAUTION
Examine the inlet and exhaust for plugging problems. When possible, rod
out the probe and exhaust. If this doesn't solve the problem, disassemble
the analyzer to locate the plug. Clean the plumbing using hot water and a
bottle brush. When assembly is complete, check for leaks using a leak de-
tecting liquid.