for correcting any gain in the system, its introduction commences at this time after the zero has been accomplished. The duration to the calibration of the auto zero is about 10-15 secs longer. This is considered a full auto- cal updated function where both zero and span are updated each hour. The air/N2 backflush causes a great disturbance in the detector preampli- fiers. The recorder when used and the ppm oil reading on the control unit digitial display, however, will not notice it due to the hold action of the sample and hold circuitry (if the analyzer is configured to “hold” and not
track, as mentioned in section 3.39, part I).
2.6ZERO CORRECTION FOR HIGH BACKGROUND STREAMS (REFERENCE B71046-0 PIPING) OR CUS-
TOMER SPECIFIC PIPING)
1.When the stream contains high background impurities, these must be cancelled out in the autozeroing each hour due to their possible normal variances in the process stream. In this case we are measuring “total oil and grease recoverable” and any non-oil organic background hydrocar- bons must be corrected for on a continuous basis. In this way, the filter assemblies are used wherein the filter labeled (F1, 3 micron) eliminates the non-dissolved oil in the process steam; while filter(s) labeled (F2, 0.2 to 1 micron) and (F3, 0.2 micron teflon element filter) eliminates over 98% of the dissolved oil species. When only the F1 filter is selected by V4 (in the up position), the autozeroing will cancel out the dissolved oil left in the process sample; thereby allowing one to measure only the non- dissolved oil (This becomes important for some users who are allowed low levels of dissolved oil in their process stream). For “total oil and grease recoverable” the V4 3-way valve is selected (in the down positon) to choose both F1, F2 and F3 filter assemblies thereby autozeroing for all oil and grease applications. In this way, the non-oil organic background is cancelled out on a hourly basis.
During the normal measuring function, sv3 is normally opened allowing the sample to enter the analysis sample cell for oil analysis. When an autozero timing signal occurs, sv3 is activated and diverts the process through the filter assembly(s) to correct the background anomolies usually on a hourly basis.
(NOTE: During calibration practices, a grab sample of the zero process fluid is obtained here at the Grab zero/Sample Cal Drain Collection. Valves, V6 and V7 are carefully opened (Caution:Be aware of any high pressure that may be in the sample) to collect a suitable zero
Teledyne Analytical Instruments