Hach-Lange 2100 AN Laboratory Turbidimeter User Manual - Manual (Page 35)

if interferences caused by color or light absorbing particles are not
present.
Using the air purge system
The air purge system is used to keep condensation off the external
surface of the sample cell when cold samples are measured.
The air purge system pushes dry air through the optical compartment to
keep the outside the sample cell dry. The connection is made at the air
purge fitting on the back of the instrument
Figure 2 on page 8.
Use dry nitrogen or instrument grade air (ANSI MC 11.1, 1975) at no
greater than 138 kPa (20 psig). The manufacturer recommends an air
consumption rate of 3 to 10 SCFH (standard cubic feet/hour).
When the sample temperature is about or less than 2 °C (35 °F), use a
desiccant dryer and particle filter to make sure that the dew point of the
air purge is less than the sample temperature. The air dryer contains
silica gel desiccant that turns pink. Replace the desiccant when it turns
pink.
If only shop air is available, use a coalescing filter with an automatic
drain and a dryer and particle filter to get instrument quality air. Use a
coalescing filter that typically operates for greater than 2000 hours.
Replace the particle filter when the air dryer is replaced.
Figure 7 and Figure 8 show the methods for connecting the two types of
air supply to the instrument.
Note: The dryer and filter are not necessary if dry nitrogen is used.
Figure 7 Instrument quality air
1 Particle filter (Balston DFU 9933-
05-BQ or equivalent)
3 Pressure regulator
2 Air dryer (Balston DAU 9933-
05-101 or equivalent)
4 Instrument air
Figure 8 Standard shop air
1 Particle filter 5 Filter (Balston 100-12-BX or
equivalent)
2 Air dryer 6 Auto drain (Balston 20-105 or
equivalent)
3 Coalescing filter/regulator (0–
30 psig)
7 Filter housing (Balston
FR-920-30 or equivalent)
4 Shop air
Using a flow cell
C A U T I O N
Do not use a flow cell with flammable samples or those that contain
hydrocarbons, solvents, concentrated acids or concentrated bases that may
damage wetted parts of the cells. Conduct tests before use of flow cells if sample
compatibility is not known.
Note: Do not use a high pressure flow cell kit with this instrument.
Use a flow cell to increase the speed, accuracy and reproducibility of
measurement. The manufacturer especially recommends using a flow
cell for low turbidity measurements.
A flow cell must be used to get the accuracy and reproducibility values in
Specifications on page 5 for color, absorbance or transmittance.
Install a flow cell
1. Fully clean and assemble the flow cell, tubing and stand. Refer to
Clean a flow cell assembly on page 34 and the user instructions
provided with the flow cell.
English 33