ECDTech - Electro-Chemical Devices

ISSUE
11/08
TECHNOLOGY NEWS FOR PROCESS LIQUID ANALYSIS
ECDTech
this issue
FAQ’s
What is the portable
PHA351? Analyzer or
Calibrator? …….Both
ECD's portable products are both an analyzer and calibrators They are a simple convenient way to obtain fast, accurate pH, ORP or conductivity measurements. They provide a mV output signal for fast field analysis of samples, calibration verification, or trouble‐shooting of installed sensors.
Features and Benefits Large LCD display read‐out Easy visual data analysis pH analyzer includes manual/ auto temperature control Adjustable temperature compensation for field measurements pH analyzer includes a built‐in "standardize" control feature Provides compensation for natural asymmetry shifts in pH or ORP electrodes Also for Conductivity CA351 Conductivity analyzer includes temperature control feature Adjustable temperature compensation for field measurements Choice of three different kit package configurations .
Triton DO8 – Optical DO Sensor P.1
FAQ’s – Portable Analyzer/Calibrator P.1
ECD Application – Water Hardness P.2
pH Electrode – Chemically Resistant P.2
New Release -Triton DO8
Optical Dissolved Oxygen Sensor
With a state-of-the-art fluorescence sensing
element, the breakthrough Triton DO8 Dissolved
Oxygen Sensor from Electro-Chemical Devices
(ECD) delivers exceptionally accurate DO
measurement with greatly reduced maintenance
requirements for a low cost of ownership over a
long service life in a wide range of municipal and
industrial water treatment applications.
The trouble-free Triton DO8 Sensor is designed
with precision fluorescence quenching (FQ)
optical technology coupled with intelligent
microprocessor-based electronics.
The selfmonitoring DO8 stores calibration data within the
sensor, which minimizes maintenance over long
service
intervals
while
providing
stable,
dependable DO measurement.
The highly accurate Triton DO8 Sensor features
a maximum error rate of less than 2 percent,
repeatability of ±0.5 percent and resolution of 0.01
ppm or 0.01 percent saturation. It operates over a
wide measurement range with three different
outputs from 0 to 20 mg/l (0-20 ppm), 0-200
percent saturation or 0-500 hPa (0-6 psi).
Developed for rugged municipal and industrial
water treatment environments, the Triton DO8
Sensor is designed to withstand ambient
temperatures from -20 to 60°C (0-140°F) and
records measurements at temperatures from -5 to
50°C (20-120°F). It withstands pressures up to a
maximum of 10 bar (145 psi).
The Triton DO8 Sensor relies on a proven FQ
method to determine the oxygen concentration in
water. A circular layer of optically-active, oxygensensitive molecules is integrated into an easily
replaceable cap. This durable layer is highly
permeable to oxygen and rapidly equilibrates to its
surroundings. The cap aligns the optically-active
fluorescence layer above two optical components
inside the sensor—an emitter and a detector.
The sensor’s emitter flashes a green light at the
layer and the layer fluoresces back a red light.
The duration and intensity of the fluorescence are
directly dependent on the amount of oxygen in the
layer. With little to no oxygen in the layer, the
response is longer and more intense. The
presence of more oxygen, however, quenches
(reduces) the fluorescence effect.
The Triton DO8 Sensor continuously analyzes
the oxygen level and water temperature with an air
pressure input setting to calculate dissolved
oxygen values. Via digital communications, the
DO8 sends DO data to ECD’s C-22 Controller,
which provides a 4-20mA output signal to a water
treatment plant’s control room. The RS-485 digital
signal is nearly immune to common EMI/RFI noise
that is typically a problem in many plant
environments.
Unlike many amperometric sensors, the Triton
DO8 has no membranes to replace, no
electrolytes to refill and no anode/cathode
assemblies to service or replace. The only service
required is the simple replacement of the DO8’s
sensor cap, which lasts two years or longer, and
the occasional wiping of the sensor head.
ELECTRO‐CHEMICAL DEVICES
www.ecdi.com
ECD Application ‐ Measuring Water Hardness
History - The term 'hardness' , as descriptive of water, has its origins in folk terminology relating to the amount of soap required to produce suds. The 'harder' the water, the greater the amount of effort (and soap) required to obtain suds. Soap suds were used as a measure of cleaning ability; no suds meant add soap and elbow grease! Background Data - We now know that hardness is caused by the presence of Calcium and Magnesium, usually in either the carbonate (CaC03 or MgC03) or bicarbonate (Ca(HC03)2 or Mg(HC03)2) form. In addition to the
original detergent‐related problems, water hardness is known to be a major source of scale (lime
deposits) in heat exchange equipment, boilers and pipelines. Hardness also adversely affects processes such as dyeing, distillation and rinsing. Natural Sources of Hardness Aqueous calcium and magnesium carbonates are usually formed when slightly acidic rain, formed by the
dissolution of atmospheric carbon dioxide (C02) into the rainwater, comes in contact with limestone and
magnesium bearing deposits. This is why rainwater (which has not come into contact with calcium and
magnesium sources) is usually much "softer" (i.e. less hard) than well
water. Unique local conditions affect both the total and relative amounts of calcium and magnesium. In general,
the ratio of dissolved calcium to magnesium is 3:1. Therefore, measuring the amount of one allows for the inferential determination of the second. It is typically the CaC03 that is measured. The unit of
measurement is either milligrams per liter (mg/L) or parts per million (ppm). In most cases, concentrations in the Article by : Joseph M. Bradley Director of Sales
range of 0.1 to 10 ppm are encountered. The usual unit of common measurement
and discussion is as equivalent ppm or mgll CaC03. Sodium Zeolite Softening - The most common method of Ca/Mg removal is via the sodium zeolite softening method. The term zeolite is applied to insoluble, solid materials which have the property of exchanging various ions with
which they come into contact. In most cases this material is in the form of small resin beads which,
collectively, are called a resin 'bed". When water containing the Ca and Mg compounds is passed through the bed, sodium (Na+) ions (attached to the resin beads) replace
both the calcium (Ca++) and
magnesium (Mg++) ions. Hot & Cold Lime‐Soda Softening Another softening method is a process in which Ca and Mg are
chemically precipitated and removed
through the use of calcium hydroxide (Ca(OH)2) and sodium carbonate (NaC03). Insoluble products
are
removed
by
sedimentation and filtration. Although ECD Hardness equipment will work in this softening processes,
the high temperatures (>100 degrees C) frequently used in this method can be a problem for the Ca electrode. This is no problem, of course, for an ECD Conductivity
measurement!
ELECTRO‐CHEMICAL DEVICES
23665 Via Del Rio
+1-714-692-1333
Yorba Linda, CA 92887
+1-800-729-1333
Fax +1-714-692-1222
www.ECDI.com
sales@ecdi.com
What ECD Measures and Why Since magnesium salts are more soluble than those of calcium, there are more Mg++ ions available for
replacement by the Na+ attached to the resin. As the resin bed deteriorates (sodium is 'consumed'
or replaced by Ca++/Mg++), a gradual increase in Ca will precede the increase in Mg. The ECD
Hardness measurement/control system is used to detect this increase (termed `breakthrough's of Ca’indicating a need for the zeolite bed to be regenerated). Because the Na‐Ca exchange does not reduce the alkalinity of the softened water, many times a Hydrogen (H+) zeolite process will be run in parallel. Water from the H+ zeolite process, which has a lower pH from the formation of Carbonic acid (H2C03) can be blended with water from the sodium zeolite to achieve a desired pH. Existing Measurement Techniques
- "On‐Line" Titration is still often used to analyze HARDNESS and pH in water softening systems. These devices require having to isolate a representative sample and condition and protect it from
contamination. Continuously using expensive chemical reagents, while requiring large amounts of time for
cleaning the sample handling ware is part of the 'cure' of using photometric/colorimetric on‐line titration devices. In addition, the sample used (10 ‐100 mV min) by the titration devices must be "wasted'. Frequent grab‐sampling with laboratory determination of
hardness is required to maintain calibration of these devices. The ECD Electrode System - The drawbacks associated with using the titration devices make continuous, on‐line measurement and control systems using a unique electrode system a popular alternative. The specific equipment models ECD recommends for this measurement are as follows: Typical Instrumentation used: The transmitter: T23‐CA/MA‐SP1‐UM, the SP1 option for the control relays. Set points are set in "ON‐OFF" ppm values. The sensor: MVS17‐T23‐CBL‐EG‐
VSS‐2005043.VIT Valve retractable calcium ion sensor with p/n 2005043.VIT calcium ion electrode and Viton o‐rings. The electrode to
use for those
harsh chemical
environments
S10/S17 Sensors
with 2005066
Electrode
ECD also has the
answer for pH in those
difficult chemical
environments ……
the 2005066 electrode.
The ECD S10/S17
sensor design has been
field proven in harsh
chemical applications.
This chemically
resistant electrode has
a two tine PEEK body,
double junction
reference and slightly
radiused pH bulb for
strength. The PEEK
body is suitable for use
in the most aggressive
solvents, oxidizing
solutions and acids or
bases. This electrode is
optimized for a harsh
chemical environment
and is suitable for
service up to 130oC.
Chemical separations
and solvent recovery in
the CPI and
pharmaceutical
industries along with
chlorine production and
flotation in mining are
suggested applications.
Take a look at the
S10/S17 product
brochure for the ECD
six point advantage.
This can be downloaded
from the ECD website
homepage.
www.ECDI.com
.
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