Chemical Engineering March 2014 - 22

GF Piping Systems
Newsfront
SenSorS Save
the Day
New and improved sensors support
chemical processing applications
in a multitude of ways
T
he chemical processing industries
(CPI) rely heavily upon
the use of sensors to measure
everything from weight to temperature
to pH to pressure. Because
sensors are used for measurements
that affect critical processing elements,
such as quality, efficiency
and safety, it is important that sensors
be placed almost everywhere
in the facility, including in highly
corrosive environments. Also, sensor
readings from these and other
operations must remain stable and
reliable. Knowing this, sensor manufacturers
continue to make improvements
to their technologies so
that chemical processors can have
confidence that the sensors, as well
as their operations, will not fail.
Smarter sensors for reliability
Keeping a system running reliably
is one of the biggest challenges faced
by chemical processors. And, depending
on the sensing technology, regular
maintenance and calibrations
can consume a lot of time. However,
if not done regularly, a bad batch or
product can be the result. " This is
especially true in the case of pH and
ORP (oxidation reduction potential),
where the electrodes are consumable
devices, requiring periodic cleaning
and calibration in order to provide
stable and reliable process readings
for proper control, " says David Vollaire,
instrumentation product manager
with GF Piping Systems (Tustin,
Calif.; www.gfps.com).
For this reason, he says, smarter
sensors are being developed that
can give the
operator an indication
of any
potential issues that may
arise between maintenance
and calibration procedures.
" In the case of pH sensors and
electrodes, they are now being
outfitted with such technology, "
says Vollaire. Self-diagnostics will
detect broken glass and high glass
impedance, alerting the operator to
probe failure or maintenance needs.
Built-in memory chips will allow for
calibration of electrodes in laboratory
or other settings and installation of
pre-calibrated probes in the field,
reducing system downtime and cumbersome
use of buffers and cleaning
solutions in the process environment.
Memory-chip-enabled electrodes can
also store operational data, such as
minimum and maximum pH/mV
readings, runtime and minimum/
maximum temperature for troubleshooting
and operations evaluation.
For example, GF Piping's Signet
2751 pH/ORP Advanced Sensor
Electronics featuring the DryLoc
connector offers realtime monitoring
of the health of the pH electrode. In
conjunction with the 9900 SmartPro
Transmitter, the 2751 will detect
broken glass and high glass impedance,
alerting the operator to probe
failure or maintenance needs.
The company's Signet 2734-2736
pH and ORP Electrodes feature a
patented reference-electrode design
and use the DryLoc connector. The
large-area PTFE reference junction,
salt bridge and reference electrode
22 ChemiCal engineering www.Che.Com marCh 2014
Figure 1. GF Piping's Signet 27342736
pH and ORP electrodes contain
an embedded memory chip, which
will store the probe calibration,
allowing the user to
calibrate in the laboratory
and install in the field
Figure 2. Endress + Hauser's
FMD71 and FMD72 looppowered,
4-20-mA HART
electronic differential pressure
Endress+Hauser
systems eliminate errors from
impulse tubing and provide additional
sensor diagnostics
are constructed to increase
the total reference effectiveness,
resist chemical attack, and ensure
long service life. The electrodes contain
an embedded memory chip,
which will store the probe calibration,
allowing the user to calibrate
in the laboratory and install in the
field. The memory chip will record
the electrode runtime, minimum
and maximum readings for evaluation
of performance over extended
time periods (Figure 1).
Craig McIntyre, chemical industry
manager with Endress+Hauser, Inc.
(Greenwood, Ind.; www.us.endress.
com), adds that quality and trust of
the measurement information is a
related challenge. " As increased process
reliability and control improvements
are sought, the demands for
more precise and trustworthy measurement
information from sensors
increase, " he says.
" Vendors are driven to design in
not only physical sensor reliability
improvements, but also calibration/
verification and sensor informationqualification
improvements, both
inside the sensors themselves and
also in companion sensor performance
management tools, " McIntyre
continues. " For example, sensor improvements
and available data are
supporting sensor calibration and
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Chemical Engineering March 2014

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