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Features
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Guaranteed Longest Lasting
Sensors Available with performance guarantee *
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Sensors are compatible with most
existing pH/ORP Meters, Transmitters & Analyzers **
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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 ULTEMŽ
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 ēC (-22 to +302 ēF) can be supported
for continuous use
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Case Study No. 2
High Sulfide, High pH Process Media
pH & ORP Measurement in
High Sulfide, High Temperature and pH process solutions
Specialized Sulfide Resistant
Triple Junction Reference Junction
Thick Wall Ruggedized, High pH
sensitive measurement element
Waterproofing Assembly for
completely Submersible Installations
The Problem
A
catalyst manufacturer had a process requiring the removal of sulfides. The
selected method of elimination was by stripping the sodium sulfide in a
sodium hydroxide solution. The sodium sulfide concentration is controlled via
a redox potential (ORP) measurement. In order to prevent free hydrogen
sulfide gas from forming, the pH was kept at the maximum possible level (12
to 14.5). The problem having such a high pH solution was that it attacked the
pH glass while the sulfide content entered the reference junction and
destroyed the reference element causing premature sensor failure.
Similar
side effects occurred when the pH drifted below 12, when hydrogen sulfide gas
was produced. The gas then diffused through the reference junction into the
sensor, destroying both the reference and pH components. The previously used
sensors experienced corrosion problems, whereby sulfides would end the cable
from the back side of the sensors, causing a sudden electrical short. The
process conditions described manifested themselves in rapid sensor drift,
frequent calibration and shortened sensor lifetime. The inaccuracy of the pH
readings (particularly at very high pH) resulted in exceeding the emission
limits, occasional emergency evacuations and EPA penalties.
The Solution
The
solution was the combination of a high pH resistant pH and ORP glass elements
sealed against sulfides together with a sulfide resistant solid state triple
junction reference system. An ULTEM thermoplastic sensor body housing was
chosen for its excellent chemical and thermal resistance to sulfides at a
variety of pH and temperatures values.
Waterproofing option A was installed
on the sensors to make the assemblies suitable for completely submersible
installation.
The
appropriate electronic components were integrated into these built to order
(custom) pH and ORP sensors such that they could be installed on the existing
pH and ORP transmitters. The result of using ASTIs custom engineered pH
and ORP sensors was to reduce the potential drift to a minimum and eliminate
the need for frequent calibrations. The increased accuracy reduced the
consumption of large quantities of chemicals and almost tripled the lifetime
of the sensor, all with requiring the installation of new pH and ORP
instrumentation.
The pH Sensor Used:
Model: PNXTJ 6631-1000JYC-15 pH Sensor with Waterproofing
Option A
Description: ž- 1 MNPT Immersion ULTEM Bodied Sulfide Resistant
pH Sensor with Triple Junction reference system; Accu-Temp Fast Response Integrated
1000 Ohm Platinum Temperature Element and Stainless Steel Solution Ground; 15
feet cable to connect directly to Johnson Yokogawa pH Analyzer/Transmitter
with Waterpoofing Option A
The ORP Sensor Used:
Model: PNXTJ 6831/6631-1000JYC-15 ORP Sensor with
Waterproofing Option A
Description: ž- 1 MNPT Immersion ULTEM Bodied Sulfide
Resistant ORP Sensor with Triple Junction reference system; Accu-Temp Fast
Response Integrated 1000 Ohm Platinum Temperature Element and Stainless Steel
Solution Ground; 15 feet cable to connect directly to Johnson Yokogawa pH
Analyzer/Transmitter with Waterpoofing Option A
A plastic body housing material is available to suit
any application from the mundane to the most difficult
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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