Hach Lange astroTOC Basic User Manual page 18

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 considerations
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 a larger process pipe to minimize interference from air bubbles or
pipeline bottom sediment. A sample line going into the center of a process pipe is best.
Figure 9 shows examples of good and bad methods of sample line installation into a process pipe.
Keep sample lines as short as possible. Sediment can accumulate in long sample lines.
Sediment absorbs total organic carbon during occurrences of high concentration. Later, total organic
carbon dissolves into the sample and causes high readings or longer response times to sample
concentration changes.
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.
Plumb the sample dilution line
Refer to Figure 15 on page 30 to identify if the analyzer has a dilution pump. If the analyzer has a
dilution pump, plumb the sample dilution line.
1. Plumb tubing to the dilution inlet. Refer to
18 English
Figure 8 on page 17.
on page 3 for sample requirements.
Figure 8
2 Sample flow
Figure 8
on page 17.
on page 17.