Chemical Engineering December 2010 - 20

Pepperl+Fuchs
Newsfront
In applications where
there is foam or an emulsion
layer, ultrasonic techniques
were traditionally used. However,
the technology was limited
in that it would read the top of
the emulsion layer or the foam.
But improved signal reliability allows
radar devices to differentiate
and give an accurate reading.
When it comes to solids, most devices
in the past provided good, accurate
level measurement when the tank
was static, but when there was product
movement, the resulting dust in the
vessel would cause the device to lose
the signal. Improving signal reliability
has allowed the signal to be maintained
through fill and release of product.
Radar technologies are also able
to work despite vapor conditions and
high pressures or temperatures.
Because of the myriad of benefits
and opportunities to use radar devices
in a variety of applications, many
level-measurement-device suppliers
have launched new radar products,
each with its own spin. " Before radar
was a prevalent technology, there were
other technologies you could use, but
none of them really tackled these more
difficult issues, " says Jerry Boisvert,
strategic marketing specialist with
Siemens (New York, N.Y.). " It was
like forcing your foot into a too small
shoe, so we are working on introducing
technologies that aren't a forced
fit on difficult applications. "
One such technology is Siemens'
Sitrans LR400, a four-wire, 24 GHz
FMCW (frequency modulated continuous
wave technology) radar level
transmitter for continuous monitoring
of liquids and slurries in storage and
process vessels including high-temperature
and high-pressure applications,
to a range of 164 ft. It is suitable
for use on low dielectric media.
The combination of 24 GHz and high
signal-to-noise ratio contribute to improve
signal reflection, smaller and
more compact designs, better accuracy
and the ability to solve problems that
may have been difficult in the past,
says Boisvert.
Honeywell (Morristown, N.J.) also
offers SmartLine non-contact and
guided-radar level-meters for traditionally
difficult applications. The
level MeAsureMent
service providers
Figure 2. The
Pulscon LTC transmitter
for continuous level
measurement in powdery to
granular bulk solids and liquids
provides measurement independent
of density, temperature and
dust and can also be used with
foam on the surface
non-contact version employs
FMCW technology for level measurement
of solids and liquids and
can be used to calculate volume. It
provides a more stable measurement
than pulse radar and is suitable
for use in agitated process
conditions in demanding applications.
The guided version operates
on time delay reflectometry to measure
level, distance, interface, level
and interface, volume and mass. It
is suited for measuring liquids as
well as granular solids.
Endress+Hauser (E+H; Greenwood,
Ind.) offers an interesting
twist in radar devices via its Levelflex
FMP55, which is a multiparameter
technology that provides
interface and level measurement
in liquids. The FMP55 combines
W
Automation Products
Group
BinMaster
Endress+Hauser
Honeywell
K-Tek
www.apgsensors.com
www.binmaster.com
us.endress.com
www.honeywell.com
www.ktekcorp.com
Ohmart/VEGA www.ohmartvega.com
Pepperl+Fuchs www.pepperl-fuchs.com
Siemens
usa.siemens.com
guided radar and capacitance technologies
in the same unit on the same rod
or cable. " The advantage of this is that
by using two technologies, it can measure
interface well, especially those
that have an emulsion or rag layer, "
says Gene Henry, product business
manager with E+H. " The capacitance
technology measures interfaces that
have rag layers well but can't measure
overall level. Guided radar measures
overall [level] well, but is not always
reliable with interfaces. By combining
the two into one instrument, you can
have the best of both worlds. "
Pepperl+Fuchs (P+F; Twinsburg,
Ohio) also offers a radar device with
something extra. The Pulscon LTC
transmitter for continuous level measurement
in powdery to granular bulk
solids and liquids provides measureAvoiding
overspill
hile not as technologically advanced as many of the continuous level products,
point level measurement is taking on an increasingly important role for chemical
processors since environmental safety concerns have moved to the forefront.
" Most chemical processors are looking closely at their level measurement devices for
overspill protection due to the environmental and safety impact an accidental overfill
can create, " says E+H's Henry. " If you have a hazardous or flammable material that
gets out of the tank, vapors may spread away from the site and a fire or explosion can
result either on your site or in another area, so overspill protection is key for chemical
and petrochemical processors who want to keep their safety record intact. "
The increasing importance of overspill protection has led to two trends. The first being
the use of SIL-rated instruments (SIL = safety integrity level; for more on SIL, see Tolerable
Risk, Chem. Eng., September 2007, pp. 69-74). With SIL-rated instruments, it is not just
the instrument, but the fact that to maintain an SIL rating, there must be a total solutiondriven
process that includes testing the instruments and the system to make sure they are
working. " To maintain a SIL rating, there have to be frequent system and instrument checks
and tests, which all plays into having a program for overspill protection, " says Henry.
The other occurrence resulting from increased overspill protection is the replacement
of mechanical high-level switches to more advanced technologies. " Historically floats or
mechanical switches were used in these applications, but now we are see more vibrating
level switches, many of which offer an SIL rating, because they are more reliable, " says
Omhart Vega's Bailey.
Vibrating fork technology is growing in popularity because it is immune to a lot of
influences such as viscosity, solids forming within a liquid, foams, temperature and humidity.
" It functions equally well in a lot of environments, which isn't the case with many
traditional, point level switches, " says P+F's product manager, Mike Mendicino.
Bailey adds that as environmental regulations continue to tighten, many processors
are going the extra mile and adding some sort of continuous technology to at least one
point level device. " This provides redundancy and reliability and shows a tremendous
commitment to trying to prevent overspills, " says Bailey.
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20 ChemiCal engineering www.Che.Com DeCember 2010

http://www.apgsensors.com http://www.binmaster.com http://us.endress.com http://www.honeywell.com http://www.ktekcorp.com http://www.ohmartvega.com http://www.pepperl-fuchs.com http://usa.siemens.com http://www.Che.Com

Chemical Engineering December 2010

Table of Contents for the Digital Edition of Chemical Engineering December 2010