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TE-5170V VFC TSP 21 Operations Manual
The slope and intercept are taken from the Qactual section of the Orifice
Calibration Worksheet.
The first step is to convert the orifice readings to the amount of actual air
flow they represent using the following equation:
Qa = 1/m[Sqrt((H2O)(Ta/Pa))-b]
where:
Qa = actual flow rate as indicated by the calibrator orifice, m3/min
H2O = orifice manometer reading during calibration, in. H2O
Ta = ambient temperature during calibration, K ( K = 273 + °C)
Pa = ambient barometric pressure during calibration, mm Hg
m = slope of Q actual orifice calibration relationship
b = intercept of Q actual orifice calibration relationship.
Once these actual flow rates have been determined for each of the five run
points, they are recorded in the column titled Qa, and are represented in
cubic meters per minute. EPA guidelines state that at least three of these
calibrator flow rates should be between 1.1 to 1.7 m3/min (39 to 60 CFM).
This is the acceptable operating flow rate range of the sampler. If this
condition is not met, the sampler should be recalibrated. An air leak in the
calibration system may be the source of this problem. In some cases, a filter
may have to be in place during the calibration to meet this condition.
The sampler H2O readings need to be converted to mm Hg and recorded in
the column titled Pf. This is done using the following equation:
Pf = 25.4 (in. H2O/13.6)
where: Pf is recorded in mm Hg
in. H2O = sampler side pressure reading during calibration.
Po/Pa is calculated next. This is used to locate the sampler calibration air
flows found in the Look Up Table. This is done using the following equation:
Po/Pa = 1 - Pf/Pa
where: Pa = ambient barometric pressure during calibration, mm Hg.
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