Instruction Manual

13
6.5 Calibration
Figure 7, sample flow calibration curve
All metering pumps must be calibrated to accurately specify stroke length settings for
required flow rates.
A typical calibration chart is shown above. Although output is linear with respect to stroke
length setting, an increase in discharge pressure decreases output uniformly, describing a
series of parallel lines, one for each pressure (only two are shown).
The theoretical output flow rate at atmospheric discharge pressure is based on the
displacement of the diaphragm, stroke length and the stroking rate of the pump. With
increasing discharge pressure there
is a corresponding decrease in output flow. Pumps are
rated for a certain flow at a rated pressure (check nameplate). Whenever possible, calibration
should be performed under actual process conditions (i.e., the same or a similar process liquid
at system operating pressure).
To construct a calibration chart, measure the flow rate several times at three or more stroke
settings (i.e., 25, 50, 75, and 100), plot these values on linear graph paper, and draw a best-fit
line through the points. For stable conditions, this line should predict settings to attain required
outputs.
All users are encouraged to test the flow rate of their pump once installed in their
system, to ensure best accuracy and reliable operation.