Colorimeter Module, Holding Coil, And Reaction Coil; Rotary Valve Module; Mixer Module; Plumbing Diagram And Tubing Lengths - Hach APA 6000 Operation Manual

Section 1

1.2.3 Colorimeter Module, Holding Coil, and Reaction Coil

1.2.4 Rotary Valve Module

1.2.5 Mixer Module

1.2.6 Plumbing Diagram and Tubing Lengths

Page 8
General Description
1.6 mL and it can move in either direction to aspirate or dispense fluids over a
0.1 to 8.0 mL/minute range.
Samples are measured in a temperature-controlled single-wavelength flow
cell. Light from an LED in the colorimeter passes through a 600 nm bandpass
filter. The path length is 8.75 mm (0.344 inches). The temperature is
controlled at 50 °C (120 °F).
The holding coil is a length of 0.030 inch ID Tefzel tubing arranged to minimize
mixing. The holding coil allows low volumes of representative sample to be
measured each cycle. The holding coil also effectively brings the sample and
reagents to the temperature control point. Without the holding coil, "old"
sample would need to be flushed from the burette. This would require at least
10x greater volume and longer analysis times, higher wastes, more sample
conditioning, more standard consumption, etc.
This parameter also utilizes a 550 µL reaction coil. The reaction coil allows
reproducible dispersion (or spreading) of the sample/indicator with the titrant
(acid). As the two fluids disperse, a full range of concentrations result. This
range begins with all sample/indicator then transitions to a greater
concentration of titrant. Eventually, a maximum concentration of titrant is
reached and as the transition continues, the titrant strength drops until only
sample/indicator is present again. The reaction coil is placed between the
valve and detector. After the dispersion described above occurs, the response
is measured as fluids pass through the detector.
The rotary valve directs fluids to various components in the instrument. The
valve is a selection valve with a common port at the center. An internal rotor
turns to align a grove between the center port and any one of the ten available
ports around the perimeter. The valve has a face sealing design. All tubing is
factory-assembled and labeled for each individual chemistry.
The mixer module mixes reagents with the sample or standards. Fluid
normally enters and exits through the bottom of the module. The openings at
the top supply an overflow and vent. The vent line is connected to the drain
block. The mixer is made of acrylic and has an approximate volume of 2.0 mL.
The mixer is filled, emptied, and rinsed during a typical measurement cycle.
Mixing and excess air removal is accomplished via a magnetic stir bar.
Figure 1 on page 10 shows the user-replaceable tubing on the analyzer and
Table 1 on page 10 describes the terminal end size of each tube. The tubing
is 0.030 inch ID Tefzel. The small diameter allows for low-volume and high-
flow rates. A higher flow rate, along with properly applied sample conditioning,
prevents the tubing from plugging.
General information for replacing the tubing is presented in the APA 6000
Installation and Maintenance Manual (Cat. No. 62005-18).
6200018overview.fm