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APPENDIX C
C1 7997 100 Sensors
C1.1 Description
This sensor no longer available;. It has been replaced by the 7997 201
and 7997 202 sensors. It is included here to provide information for
users of existing 7997 100 sensors.
The sensor is designed to operate at very low turbidity values of less than
0.1 NTU. At these very low turbidity values it is most important that
additional sources of light scattering are eliminated, i.e. gas bubbles in
the sample. To minimize sample degassing, sample flow rate and line
pressure must be controlled by a valve on the outlet of the flowcell and
NOT on the inlet – see Fig. C2.
If the line pressure is above the flowcell limit of 3 bar, line pressure cannot
be reduced before the flowcell without introducing degassing. In this
case an optional debubbler (part number 7997 500) is available to
eliminate the effect of gas bubbles.
C1.2 Flow Unit Dimensions
M
o
d
l e
H
e
g i
t h
7
9
9
7
1
0
0
2
5
7
0 .
Set Up Procedure for Optional
De-bubbler
With a system which includes a
de-bubbler, set it up as follows:
1) Ensure that the 'sample in'
isolating valve (A) is fully open.
2) Adjust the sample flow through
the turbidity system using the
regulating valve (B).
3) If necessary, close the 'sample
in' isolating valve (A) such that
the overflow from the de-
bubbler is at a minimum.
= Optional
Note. Sample isolating and regulating valves together with a flow indicator are recommended to ensure easy maintenance
and consistent performance. These devices are not supplied with the 7997 Turbidity Monitoring System.
42
W
d i
h t
D
e
p
h t
3
2
0
0 .
2
1
6
0 .
Important Note.
The de-bubbler MUST be
mounted vertically with the flow
upwards.
De-bubbler
Drain
Outlet
Tundish
Valve (A)
Flow
Regulation
Valve
Sample in
Fig. C2 Typical System Installation for 7997 100
Flow-chamber
Cap
Inlet/Isolating
Valve
Optical
Receiver
Optical
Emitter
Fig. C1 Main Components
Minimise height
to avoid syphoning
effect
Caution.
See also Fig. 2.13
7997 100
Inlet/Isolating
Valve
Flow-chamber
Outlet/Isolating
Valve
7997 100
4670
4675
Valve (B) Flow
Regulation
Valve
Valve (B)
Flow Indicator
Flow
0.5 to
1.5 l/min
Valve (B)
Outlet/Isolating
Valve
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