Hach DR2400 Manual page 555

Tips and Techniques for Using the Vacuum Pretreatment Device
• If the sample does not flow through the Chloride Removal Cartridge (CRC), increase the vacuum until flow starts, then reduce the
vacuum down to 20 inches of water. Proceed as usual.
• The maximum range of the VPD gauge is 40 inches of water; it will not indicate the full vacuum level obtained. Full vacuum is
20–25 inches of mercury; this can be measured at the vacuum pump with a gauge calibrated for inches of mercury.
• Dispose of the used Chloride Removal Cartridge. Do not reuse it.
Using the Vacuum Pretreatment Device
1.
Attach the Vacuum
Pretreatment Device*
(VPD) to a vacuum pump
(not an aspirator-type
vacuum) that can create a
vacuum of 20–25 inches
of mercury.
*Patent Pending
OxygenCOD_Other_Other_MD3_Eng_Ody.fm
2.
Label each Mn III
COD vial and remove the
cap. Place the vials in one
of the numbered holes in
the VPD base.
Oxygen Demand, Chemical
3.
Place the VPD top on
the base. Insert a fresh
Chloride Removal
Cartridge** (CRC)
directly above each
Mn III COD Reagent Vial.
Plug any open holes in
the VPD top using the
stoppers provided.
**U.S. Patents 5,667,754;
5,683,914
4.
Turn on the vacuum
pump and adjust the
vacuum regulator valve
on top of the VPD until
the internal gauge reads
20 inches of water.
Oxygen Demand, Chemical
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