Hach SP-51 Manual Básico Del Usuario página 10

4.2 Plumb the instrument
Fire hazard. This product is not designed for use with flammable liquids.
Chemical hazard. If there is a leak in the fluid system, hazardous substances may leak
out of the lower enclosure. Put the supplied reagent bottle tray or a bucket under the
drain to catch any spills.
Chemical exposure hazard. Dispose of chemicals and wastes in accordance with local,
regional and national regulations.
Use quick-connect type connectors for ¼-inch OD tubes to install the sample inlet and drain
connections.
1. Install 3 feet of tubing in the ½-inch enclosure drain to keep dust out of the analyzer. Refer to
Figure 1 on page 7, item 11.
Note: Make sure that the enclosure drain is open. The drain must be open to remove sample water if leaks
occur.
2. Push the ¼-in OD poly tube on the sample line connector. The tube will "stop" two times as it is
pushed on the connector. For more information, refer to the installation kit documentation.
3. Make sure that the tubes are pushed completely on the connector. Incorrect installation can
cause the tube to come off of the connector when water pressure is applied.
Note: The sample drain connector will install on ½-inch ID flexible tubes (customer-supplied).
4.2.1 Connect the air purge (optional)
An air purge is necessary in an environment with high humidity or caustic vapors. Additional
information is available on the manufacturer's website.
4.2.2 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.
4.2.3 Connect the sample stream
Install the 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.
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Figure 5 shows examples of good and bad installation.