Parker ChemTec II, Installation, Operating, & Maintenance Instructions

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Exponential Feed - Mass Flow, Example
A biotechnology company generated the following 75-hour, exponential feed. Utilizing a utility pump hooked
up to a process control device, 150 data points were required to define the exponential feed strategy over this
75-hour period.
Parker offered a simpler, alternative approach by generating an exponential feed based on six, linear
segments, each segment being 12.5 hours long. This approach reduced the required number of data points
from 150 to 7 without adversely affecting the feeding accuracy. The following data set, which was derived
from the original 150-point data set, was used to define the six, linear feeding segments:
A ChemTec II CP-8 with a TANDEM 1081 peristaltic pump head
(8 RPM pump motor) was used for this feed application. PharMed pump tubing #16 since it can generate
pump rates from 0.4 ml/min. to 6.4 ml/min.
The following recipe was entered into the Mass Flow mode:
START
Interpolate from 0.37 gm/min to 0.50 gm/min over 12 hours, 30 minutes
Interpolate from 0.50 gm/min to 0.94 gm/min over 12 hours, 30 minutes
Interpolate from 0.94 gm/min to 1.28 gm/min over 12 hours, 30 minutes
Interpolate from 1.28 gm/min to 1.75 gm/min over 12 hours, 30 minutes
Interpolate from 1.75 gm/min to 2.39 gm/min over 12 hours, 30 minutes
END
When executing the above program, the ChemTec II will generate an initial pump rate of 0.37 g/m, which is
ramped up to 0.50 g/m during the first 12.5-hour segment. As shown in Figure 2, the six linear segments
provide an excellent fit. The largest deviation (error) from the original, exponential feed rate is found in the
last segment, which starts at 62.5 hours and ends at 75.0 hours. If necessary, the error associated with the
last segment can be substantially reduced by generating two segments each 6.25 hours long in its place:
SEGMENTS
Interpolate from 1.75 gm/min to 2.05 gm/min over 6 hours, 15 minutes
Interpolate from 2.05 gm/min to 2.39 gm/min over 6 hours, 15 minutes
Time, hrs. Mass Flow Rate, gr/min.
0.0 0.37
12.5 0.50
25.0 0.69
37.5 0.94
50.0 1.28
62.5 1.75
75.0 2.39