Shortridge Instruments ADM-860C, Руководство по эксплуатации

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ADM-860C 04/14/08 27
2. Determine the "actual" volumetric air flow through the given AMD air movement device. Pitot tube
duct traverse is likely the most reliable means of determining the actual air flow. Direct air flow
measurements can also be used in areas where duct air velocity measurements are not practical,
by using the FlowHood with custom designed tops.
3. Calculate the effective average face velocity (fpm) by dividing the actual air flow measured in Step
#2 (cfm) by the gross active face area (sq ft) calculated in Step #1.
4. Measure the average face velocity at the AMD using the VelGrid, AirFoil probe or other velocity
instrument being tested for a Kv. Document the procedure used to obtain the average face velocity
including all factors such as: the instrument used, the sensing probe positions, spacing of the
velocity sample points and the number of readings taken to obtain the average for each
measurement location. Always record the instrument type and any specific set up conditions such
as whether readings were taken in local or standard air density (ADM-870 and ADM-870C models
read both local and standard density), and whether or not the correction included temperature.
5. Calculate the velocity correction factor "Kv" for this particular AMD by dividing the effective average
velocity obtained in Step #3 above by the measured velocity obtained in Step #4 above. This "Kv"
factor should now be used routinely as a required multiplier to correct velocity readings taken at this
specific AMD design, model and size. The specific procedures developed for measuring air
velocities at a given AMD must always be used to obtain the air velocity measurements.
This "demanding" five step procedure seems to leave little room for the "art" of Testing and Balancing. This is
not altogether true. The measurement of the air velocity in Step #4 is affected by the position and orientation
of the air velocity measuring probe. By selective experimental positioning of the sampling point locations, a
procedure can be developed which will result in a Kv for this particular AMD very near or equal to 1.0.
The face velocity test procedure should be included in the AMD test report. The result is a documented,
repeatable face velocity measurement that can be confirmed by a trained technician using the proper
instrumentation and following the test procedure. This procedure may also be used by laboratory personnel to
retest the air flow at periodic intervals to confirm that the flow still conforms to test report data.
6.2 PITOT TUBE VELOCITY MEASUREMENT
The pitot tube is primarily used to obtain air velocity measurements in ductwork. A pitot tube is stainless steel
with a 90 degree bend at one end and two connectors at a 90 degree angle located near the base. The
measurement range of the AirData Multimeter with the pitot tube is 25 to 29,000 fpm (calibration accuracy is
certified from 50 to 8,000 fpm). A "traverse" of the duct is obtained by taking multiple air velocity readings at
equal area locations within the duct cross-section. See AIR BALANCE MANUALS AND TRAINING
PROGRAMS for sources of detailed information on performing duct traverses and other air balance procedures.
The stainless steel pitot tube included in the AirData Multimeter kit is suitable for use in temperatures up to
1500
/ F.
Connect one of the tubing sections from the positive (+) port of the meter to the total pressure connection (in
line with the main shaft) on the pitot tube and connect the negative (-) port to the static
pressure connection (perpendicular to the main shaft).