Hach astroTOC UV 4195-1010 Manuel D'utilisation page 18

Plumb the sample line and sample bypass
1. Plumb tubing to the sample inlet(s).
2. Put the tubing in the zero standard container.
3. When the start-up is complete, plumb a sample source to the sample inlet(s) and plumb the
sample bypass outlet(s). Refer to
Refer to Specifications
4. Install a check valve on the sample line near the analyzer so that the sample stream can be
stopped for maintenance.
Sample line guidelines
Select a good, representative sampling point for the best instrument performance. The sample must
be representative of the entire system.
To prevent erratic readings:
• 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.
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 9 Sampling methods
1 Air
Plumb the cleaning solution line
1. Plumb tubing to the cleaning solution inlet (CLEAN port). Refer to
2. Put the tubing in a container of cleaning solution.
18 English
Figure 8 on page 17.
on page 3 for sample requirements.
Figure 9 shows examples of good and bad installation.
2 Sample flow
Figure 8 on page 17.