Chemical Engineering July 2021 - 12

Endress+Hauser
FIGURE 2. The iTHERM TrustSens uses an internal
reference material that enables the device to recalibrate
itself without removing the sensor
material is determined with extreme
accuracy for each sensor (typically
around 118.0°C), so each time there
is a cooling process starting at higher
temperatures, such as a steam-sterilization
of the plant, the sensor is
calibrated automatically. If the measured
deviation between the reference
and the sensor is outside the
set limits, the device sends an alarm
message, which is also displayed on
the device as a flashing red LED.
Because steam-sterilization is
often performed daily, the calibration
is performed much more frequently
compared to manual calibration intervals
that have been determined
based on a risk assessment. This
saves considerable time and money,
because the calibration is performed
without any personnel costs or additional
planned downtimes, says marketing
manager Amar Löffler.
Although it took some time to convince
users, the TrustSens is now
becoming accepted by industry, with
thousands of units installed, says Löffler.
From initial field testing, it was
found that the device doesn't just save
time, but it prevents mistakes - " improved
precision (that is, consistency
of accurate results at lower risk of drift
or undetected failures) was found to
be the biggest benefit, " he says.
Endress+Hauser is further developing
this technology for applications in
the chemical industry, where clean-inplace
operations are performed regularly,
but at lower temperatures, says
Löffler. The company has been looking
for a reference material with a TC
of around 60°C for such applications.
Thermowell design
Last June, Emerson introduced the
Rosemount Thermowell Design Accelerator
(TDA), which eliminates the larg12
est
" pain point " of temperature process
design - manual thermowell iterations
- significantly increasing operational
efficiencies and cost savings. " Emerson's
TDA allows customers to perform
wake frequency calculations per ASME
PTC 19.3 on their thermowell designs,
and automatically iterates failed tags
to reduce design time, " explains Emerson's
Stultz. The TDA software will
also provide users with solutions, including
Rosemount X-well Technology
(described below) and Rosemount
Twisted Square thermowell.
When conventional thermowells
don't pass the ASME PTC 19.3 thermowell
evaluations, the majority of
the time it is due to dynamic stress on
the thermowell from the process, explains
Stultz. " The Rosemount Twisted
Square thermowell design [Figure 3]
eliminates over 90% of these dynamic
stresses to achieve an accurate process
temperature measurement and
reduce the risk of thermowell failure, "
he says. " This leads to a more accurate,
safer temperature measurement. "
Last
year, Endress+Hauser introduced
a patented Dual Seal feature
for its iTHERM Moduline TM131 temperature
transmitter, which adds a
second safety barrier to the process.
The loss of thermowell integrity, due
to abrasion or corrosion, is detected
and immediately seals off the sensor
insert, thereby preventing the leakage
of hazardous process medium to the
environment or into the control room
(for example, through conduits). The
temperature transmitter then relays a
message to the control system so that
safety measures can be taken to avoid
harm to people or the environment, explains
Löffler. " In the past, it could take
a long time before you realize there a
problem, and might only notice after
the damage is done, " says Löffler.
Non-invasive measurement
" The biggest trend and technological
development we see at Measurement
& Analytics is clearly non-invasive
temperature measurement, " says
Guruprasad Sosale, global product
manager, non-invasive & wireless
technologies of ABB Measurement
& Analytics (Munich, Germany; www.
abb.com). " In 2018, ABB ushered in
a new era of temperature measurement,
using non-invasive sensors,
when we launched our very own noninvasive
sensing device that allows
plant operators to measure process
temperature without compromising
on performance: no shutdown, no
holes, with dramatically simplified engineering, "
he says.
" Every plant process engineer,
maintenance engineer and plant manager
knows the benefit of being able
to measure temperature accurately
without having to engineer and install
a thermowell. For future facilities, a
non-invasive approach to temperature
measurement simplifies engineering
temperature points and dramatically
reduces the capital expenditure costs
of up to 75% due to reductions in design
and engineering, materials and
installation costs, " says Sosale.
To measure surface temperatures,
ABB uses a double sensor architecture
that overcomes the drawbacks
of traditional skin-temperature sensors,
explains Sosale. One sensor is
in contact with the surface of the pipe
while the second measures the ambient
temperature in the vicinity. A thermal
model using these measurements
compensates for contact resistances
and ambient effects to measure the
surface temperature at the tip. The
actual process temperature is then
inferred using thermal models of typical
fluids flowing in piping to predict
FIGURE 3. The Rosemount Twisted Square thermowell design reduces the risk of thermowell failure
Emerson
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Chemical Engineering July 2021

Table of Contents for the Digital Edition of Chemical Engineering July 2021