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Features
·
Guaranteed Longest Lasting
Sensors Available with performance guarantee *
·
Sensors are compatible with most
existing pH/ORP Meters, Transmitters & Analyzers **
·
Application Specific Engineering
results in optimum Lifetime & Performance ***
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Integrated Temperature
Compensation, Preamplifiers & Solution Ground Elements
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Solid State Reference System offers superior resistance to Fouling
& Dehydration
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Applications such as Acid/Fluoride,
Hi-Temp, Saturated Sodium and Sulfide Resistant are available as standard
options
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Custom Applications are available,
often at no additional charge
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Most Installation Styles are
Supported Including: Immersion, Twist Lock, Valve Retractable
& Sanitary
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Available in a wide range of plastics,
from cost effective CPVC to thermally & chemically resilient ULTEM®
and PEEK thermoplastic
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High Pressure Applications up to
100 psi for Valve Retractable & 150 psi for Inline Installations can be
supported for continuous use
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Operating Temperatures from -30
to +150 ºC (-22 to +302 ºF) can be supported
for continuous use
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Case Study No. 10 – Bleaching
in Pulp Mills
pH and ORP sensors as used
for process control in bleaching operations at Pulp Mills
Specially Engineering Dissolved
Chlorine Gas Resistant Solid State Reference
Flat, yet rugged break resistant
glass minimize cleaning requirements
Application specific engineered
thermoplastics and conductive polymer materials of construction lead to
optimized sensor lifetime and accuracy
The Problem
A pulp and paper producer wanted to improve
their control and reduce their maintenance time and costs for their ClO2
bleaching process lines. They wanted to better control the brightness of the
resultant pulp and reduce down time due to pH and ORP sensor failure and cleaning
requirements. This meant that they were replacing their sensor every 1-2
months and cleaning and calibrating bi-weekly.
Conventional
pH/ORP sensors experienced fast intrusion into the reference element due to
the high temperature (from 100 to 150 ºC, 212 to 302 ºF) and pressure (50 to
100 psi) in the presence of high concentrations of chlorine dioxide gas.
Previously used pH and ORP sensors required frequent calibrations due the
drift of the reference element. The strong bleaching agent attacked both the sensor’s
internal “O”-rings and other external “O”-rings that sealed it to the
titanium sheath. Failure of these “O”-rings permitted the dangerous process
gas to intermittently escape intermittently during removal and insertion of
the multi-component valve retractable sensor assembly. The sealing agent for
the junction and pH components were dissolved and eroded, allowing the gas to
intrude all the way through the reference element and to the back of the sensor.
The Solution
The hardware solution was the use of a 316
stainless steel, complete isolation double ball valve sensor retraction and
insertion assembly. The sensor solution incorporated dissolved gas (chlorine
dioxide) and slurry/viscous material resistant pH and ORP components. These
sensors were sealed from the front and back end with agents that were
selected based upon the chemicals and process conditions present. The
non-porous cross-linked high-density conductive polymer triple junction reference
system did not allow for the chlorine dioxide to diffuse in the junction thus
extending the lifetime of the sensor five-fold.
The frequency
of calibration was significantly reduced as well as the drift of the
reference signal. The single unit, completely sealed, “O”-ring free design sensor
design allowed the high grade thermoplastic (ULTEM and PEEK) sensor body housed
¾”-¾” MNPT immersion sensors to be installed directly into the double ball
valve retraction assembly. This significantly reduced maintenance
time required, eliminating the need for disassembly and re-assembly of
insertion sheaths (unlike other manufacturer’s multi-component valve
retractable designs). The safety of operating the double ball valves improved
by removing the possibility of “O”-ring seal through ASTI’s “O”-ring free
design. The required temperature compensation element was embedded directly
into the sensor, permitting the cable to be connected directly from the back
of the sensor in the original equipment manufacturer’s (OEM) transmitter. In
this way, the company was able to leave the process control loop in place,
yet greatly improve the quality of their process through superior pH &
ORP sensor performance and lifetime.
The pH Sensor Used:
Model: PNCTJ 6342-3000-15 pH Sensor
Description: ¾”- ¾” MNPT Immersion PEEK Bodied Slurry/Viscous Material
and Dissolved Chlorine Gas Resistant pH Sensor with Triple Junction reference
system; Integrated 3000 Balco Temperature Element; 15 feet cable to connect
directly to TBI-Bailey-ABB pH Transmitter
The ORP Sensor Used:
Model: PNCTJ 6842-0000-15 ORP Sensor
Description: ¾”- ¾” MNPT Immersion PEEK Bodied Slurry/Viscous material
and Dissolved Chlorine Gas Resistant ORP Sensor with Triple Junction
reference system; No Temperature Element; 15 feet cable to connect directly
to TBI-Bailey-ABB ORP Analyzer/Transmitter
Choosing the Correct pH/ORP
Sensor
1.
Choose a sensor body type that
suits the physical parameters of the
installation (refer to the Configurations
Portion of pH/ORP and Ion Selective webpages).
2. Choose
a sensor that suits the process application, temperature,
chemistry, and physical
parameters of the installation (refer to Sensor Selection Guides
and call factory or local sales agent for support)
3. Choose a sensor housing material that is compatible
with the process chemistry, temperature & pressure (refer
to Chemical Resistance Charts as posted under the Technical
Documents portion of the website).
4.
Select suitable temperature compensation element, solution
ground & integrated preamplifier based upon the mating pH/ORP Instrument (refer to Electrochemical Instrumentation
Page & ask for factory support).
5.
Specify the required
cable length based
upon installation
location (refer
to Part Numbering Guide).
*
Subject to application qualification and review by an approved ASTI sales
agent and/or factory. Performance guarantee is posted on the ASTI online
application questionnaire page.
**
See list of supported pH/ORP/ISE Instruments webpages as posted on the ASTI website.
***
Completion of Application Questionnaire form is required. Other restrictions
may apply.
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