K-Factors Explained
Page 42
May 2020
DSY-PM-01378-EN-08
Example 2
Known values are:
Full Scale Flow Rate
=
85 gpm
Full Scale Output Frequency =
650 Hz
650 Hz × 60 sec = 39,000 pulses per min
K-factor
39,000 pulses per min
85 gpm
458.82 pulses per gallon
=
=
The calculation is a little more complex if the velocity is used because you first must convert
the velocity into a volumetric flow rate to be able to compute a K-factor�
To convert a velocity into a volumetric flow, the velocity measurement and an accurate
measurement of the inside diameter of the pipe must be known as well as one US gallon of
liquid is equal to 231 cubic inches�
Example 3
Known values are:
Velocity
= 4�3
ft/sec
Inside Diameter of Pipe
=
3�068 in�
Find the area of the pipe cross section�
2
3.068
2
Area = πr
2
Area = π
= π x 2.35 = 7.39 in
2
Find the volume in one foot of travel�
88.71in
2
7.39 in
2
x 12 in. (1 ft)
ft
=
What portion of a gallon does one foot of travel represent?
= 0.384 gallons
88.71 in
3
231 in
3
So for every foot of fluid travel 0�384 gallons will pass�
What is the flow rate in gpm at 4�3 ft/sec?
0�384 gallons × 4�3 FPS × 60 sec (1 min) = 99�1 gpm
Now that the volumetric flow rate is known, all that is needed is an output frequency to
determine the K-factor�
Known values are:
Frequency
=
700 Hz (By measurement)
Flow Rate
=
99�1 gpm (By calculation)
700 Hz × 60 sec = 42,000 pulses per gallon
K-factor
42,000 pulses per min
99.1 gpm
423.9 pulses per gallon
=
=
