How It Works
Scatter
is the effect particles have on a light shining through liquid. Typical
engineering units are PPM (parts per million), NTU, EBC, JTU and others.
In a scatter analyzer, light is collimated in a liquid, and the light
scattered (by reflection, etc.) is proportional to the concentration of
particles.
The HSB measures light scatter at a right angle to the incident light.
This has become an international standard, accepted by the EPA in the
United States, the EBC in Europe and other authorities
The Model HSB consists of a flow cell unit and the control/indicator
unit.
The unique 4-chamber design isolates scatter, transmitted and trapped
stray light.
The flow cell includes:
1. The optical light source.
2. The measuring detector which measures light scattered 90 degrees
from the main light path – the nephelometric measurement.
3. The reference detector measures transmitted light from the main
light source to provide a compensating ratio for variations in color,
lamp deterioration and/or fouling of optical surfaces.
4. A test lamp is used to test the measuring detector sensor. This
also provides a light trap.
The indicator/control cabinet contains the modular electronic circuitry
necessary to process signals from the photo-sensors to provide readings in
the required units, to display those readings, to input desired set
points, to indicate alarm levels, to operate relays and to provide
self-diagnostics.
From Light Beer to Coal Slurry…
McNab Clarity Analyzers measure suspended solids in process liquids
with:
- 0.1% Repeatability per year
- Complete international conformance—EPA, DIN, ISO; correlates with
original hazemeter and other instruments
No Standardization Required
The HSB achieves measurement stability of 0.1% per year, allowing
maintenance-free operation. This is made possible by two critical matched
signal verifying modules (SVMs), each with 100-megohm input impedance.
These SVM’s eliminate drift, so there is no need for constant
restandardization. SVM's also correct for any variation in sensor cable
length, so nearby electric interference does not affect operation, even at
cable distances of 600 feet (180m).
Built-in Zero Standard
The unique built-in zero standard can be used at any time to verify
standardization, even when the process is operating. Simply press the test
button, and the system verifies that actual standardization has been
maintained; no drift has occurred. No down time or removal is needed.
High-Sensitivity Measurement In Problem Liquids
New
high technology optics and UV-enhanced sensors deliver 1,000 times more
sensitivity than was possible just a few years ago. The HSB uses this
dramatic improvement to measure suspended solids in "problem"
liquids like dark stout and orange juice.
Complete Color Compensation
Color
is "dissolved" in a liquid. Color does not scatter light, but it
will attenuate light, interfering with accurate particle measurement.
To prevent color interference, the Model HSB measures light attenuated
by color and completely adjusts for this interference. The result is
accurate, stable measurements without moving parts or adjustments.
Center-Of-Pipe Measurement
The
ideal scatter measurement is made in the center of the actual process
pipe. Near the pipe wall, in a by-pass pipe or in a slipstream, scatter
particles will settle out because minimum velocity is not maintained. To
eliminate this problem, the HSB measures only in the high velocity region
in the center of the pipe. This is essential for high accuracy measurement
and can yield a 2:1 improvement in accuracy.
Extended-Life Light Source
Optical
lamp life has been extended to an average of five years by use of optional
improved lamp control circuitry. This makes a truly maintenance-free
system.
High Sensitivity For Ultra-Clean Liquids
Measurement of liquids, like WFI and ultra-pure water, requires high
sensitivity measuring geometry. The HSB uses a new, proprietary light trap
chamber to give a 3:1 improvement in sensitivity over the previous state
of the art. This chamber configuration traps stray light that would
otherwise block high-sensitivity measurement, as in other designs.
Model HSB
|
Principle of Operation: |
Scatter, 90º ratio, nephelometric meets
APHA, ASBC, EBC, EPA, ISO 7027. Color corrected - does not over
respond to color, matches typical laboratory angle of measurement. |
Indicator
|
Range: |
0 - 2, 20, 200 (199.9) NTU (U)
0 - 2, 20, 200, (JTU/PPM (P)
0, 200, 2000 (199.9) ASBC (A)
0 - 190% Concentration (C) |
Repeatability: |
0.1% Fullscale per year |
Sensitivity: |
0.001 NTU (0-2 range) |
Ambient Conditions: |
32 - 120ºF (0 - 50ºC),
0 - 100% relative humidity |
Recorder Output: |
0 - 1 mA |
4-20 Output: |
Two-wire, ground isolated for computer
application. |
Alarms: |
Two independent adjustable set-point
alarms 3P/DT 5A resistive unpowered. |
Built-in test and
fault-isolation: |
Alarms, relays and 4-20 trip when bulb
fails, wetted windows become obscured , or power loss. |
Housings: |
NEMA 4X (stainless - cabinet) hinged door
W13" x H 16" x D 7" (33 x 41 x 18 cm) for wall
mounting, or semi-flush. |
Meter: |
3½-Digit LED |
Weight: |
25 lb./11.3 kg |
System Test: |
Zero and span, push-to-test switches. |
Front Panel Instructions: |
Available in English, German, Dutch,
French, and other languages (per customer). |
Flow Cell Assembly
|
Range: |
Follows indicator. |
Material: |
Stainless Steel, ASTM 316L/DIN 4435,
other materials available. |
Windows (optical cell): |
Tempered borosilicate glass, vitreous
silica, TFE 3/8" to 1" (10 - 25 mm) thick. |
Seals (optical cell): |
TFE, Ethylene propylene, Buna N, PFE,
fluoroelastomer butyl, etc. |
Flow Chamber: |
Unrestricted, full diameter flow. |
Operating Pressure: |
150 psig, 10 bar, PN 10 (Contact
factory for higher ratings.) |
Operating Temperature: |
15 to 225ºF (-10
- 115ºC). Up to 480ºF (250ºC) with air purge. |
Process Flange: |
Butt weld - typical, (Flange, ASTM, DIN
and threaded and dairy available.) |
Enclosures: |
NEMA 4 (watertight - blue heads)
NEMA 6 IP68 (submersible - wetted optical cells) IP68
NEMA 7 (explosion-proof heads) |
Separation from indicator: |
600 ft. (180 meters). Complete with
cables. |
System Calibration: |
2-point: polymer bead, formazin, or
diatomaceous earth. |
Specification may be changed or
improved as necessary. |
A90-85B Rev B
|