Hach-Lange HACH 5500 sc Installation - Manual (Page 10)

• Collect samples from locations that are sufficiently distant from points
of chemical additions to the process stream.
• Make sure that the samples are sufficiently mixed.
• Make sure that all chemical reactions are complete.
Connect the sample stream
Install each sample line into the center of a larger process pipe to
minimize interference from air bubbles or bottom sediment.
Figure 6
shows examples of good and bad installation.
Keep the sample lines as short as possible to prevent the accumulation
of bottom sediment. The sediment can absorb some of the analyte from
the sample and cause low readings. The sediment can later release the
analyte and cause high readings. This exchange with the sediment also
causes a delayed response when the analyte concentration in the
sample increases or decreases.
Figure 6 Sampling methods
1 Air 2 Sample flow
Set the bypass flow rate
N O T I C E
Do not loosen the screw by more than 4 turns for the multi-stream.
The bypass flow can be adjusted when the analyzer is in shutdown
mode. Adjust the flow rate of the sample bypass line with the flow valve
as shown in
Figure 7 or Figure 8 . Refer to Specifications on page 3 for
the sample flow rate range. Use an external meter to measure the flow
rate of the sample bypass line. Increase the flow rate of the sample
bypass line when the process stream is far from the analyzer for a faster
response to changes in the process stream.
Figure 7 Bypass flow rate adjustment - one stream
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