Tip of the Week
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Click HERE for related Standard Operating Procedure (EPA2-02)
Pitot Tube Alignment
USEPA Method 2 specifies the allowable configurations of a pitot tube relative to the probe thermocouple and nozzle. Essentially, there are five things you should always check to ensure that the assembly meets these specifications prior to using a probe for a test:
- The pitot tube openings extend at least 3 inches beyond the end of the probe sheath.
- The thermocouple is at least 2 inches behind the pitot tube openings (center of opening to thermocouple tip).
- The nozzle is separated from the pitot tubes by at least ¾-inch.
- The end of the nozzle is even with the end of the pitot tube tips.
- The pitot tube impact side opening is even with or above the opening of the nozzle.
The figures below from Method 2 illustrate these points.
If these criteria are not met, then the flow results will likely be biased high, possibly by as much as 10%!
3 inches from end of sheath to centerline of pitot
tips
2 inches from Thermocouple and pitot
tip openings
¾-inch separation between tubes and nozzle
Pitot and nozzle ends aligned
Pitot tips even or ABOVE nozzle opening
plane.
