Insertion Depth Determination; Calibration Constants Determination - Hoffer Flow Controls HP Series User Manual

INSERTION DEPTH DETERMINATION

A review of the principles of fluid flow in pipelines reveals that the velocity of
the fluid across the pipe is not constant. Under a given set of conditions a flow
profile exists which varies from a parabolic shape in laminar flow to
approximately flat in the turbulent flow region.
It is the average flow in the pipeline which is of interest in obtaining a
measurement of flow in the pipe. For medium diameter pipes (diameters of 10
inches and less) the turbine is positioned at the center of the pipe. Center line
positioning is recommended to avoid the effects of stagnant flow near the pipe
wall and the turbulence of fluid near the riser.
(diameters greater than 10 inches), the turbine is positioned at the depth where
the flow equals the average fluid velocity of the flow.
Table C lists the required insertion depth for selected pipe diameters.

CALIBRATION CONSTANTS DETERMINATION

Calibration of the metering section consists of relating the precise velocity
measurement at the specified insertion depth to the geometry of the piping to
obtain a measurement of the entire flow through the metering section.
Calculate the calibration constant for the metering section (K
following equation:
=
K
MS
PF
=
F
MS
where
K - K FACTOR from calibration sheet (Hz/FPS)
PF - Mean Profile Scaling Factor (equal to 1 for large diameter pipes)
OF - Obstruction Factor
ID - Inner diameter of pipe (inches)
HP-208
K

ID

  
OF

24
AVE
K
3
(Hz / FT / Min)
MS
60
Page 14 of 17
For large diameter pipes
(Pulses / FT )
2



) using the
MS
3
HP Insertion Meter