Chemical Engineering June 2016 - 21

NOV
and provide a better return on investment.
" If we are using less material,
it results in a lighter heat exchanger
that can be hung in framework on
the second or third floor in a facility
where weight might previously have
been an issue. Also, the exchanger
will likely last twice as long because
it won't deteriorate with corrosion, so
it provides a better return on investment, "
says Herman.
Another area that affects reliability
Figure 2. Kenics heat exchangers are equipped
with streamlined Kenics static mixer elements to
offer uniform heat transfer, as well as efficiency and
reliability in difficult, demanding applications
ceptance of welded plate and spiral
heat exchangers in more demanding
applications and difficult services, "
adds Shamsi.
Why upgrade?
" A lot of the exchangers in service
today were built over twenty-five
years ago and likely used materials
such as carbon steel or copper
tubes and, in today's chemical
processing environment, that's no
longer acceptable because of corrosion
concerns, " explains Ron Herman,
director of sales and marketing
with enerquip (medford, Wis.; www.
enerquip.com). " Some of the older
units were also built without following
the current standards of the Tubular
exchanger manufacturer's Assn.
(TemA; Tarrytown, N.y.; www.tema.
org), so if there is thermal expansion
in a process, safety and environmental
concerns also may be an issue.
Or, older units may simply be difficult
to clean and maintain so maintenance
doesn't occur as often as it
should and that results in fouling and
unplanned downtime. "
" There are so many improvements
in today's materials and designs that
it is often worthwhile to upgrade, "
Herman continues. " The capabilities
of heat exchanger manufacturers
are so much more advanced today
than they were when these older exchangers
were designed and put into
service that we can not only replace
a unit, but also greatly improve its operation
and efficiency. "
for example, he says enerquip
offers reverse-engineering capabilities.
" If a customer provides the
dimensions, parameters and process
flows, we can not only run a
simulation model that will duplicate
the performance of a customer's
current heat exchanger, but also
allow us to make recommendations
that will improve its performance,
including upgrading the materials,
planning for thermal expansion or
simplifying maintenance. "
Increasing reliability and safety
many older exchangers were built
using materials that could not withstand
the corrosive environment
sometimes found in the CPI, so they
were built with a " corrosion allowance, "
meaning that the materials
were layered and thickened to compensate
for the corrosion that was
expected to occur. This increased
weight and size of the units. " With
today's materials we don't have to
overcompensate for corrosion anymore, "
explains Herman. " There are
different blends and entirely new
brands of metals that were specifically
designed for corrosion resistance
in the chemical industry. " Not
only does the use of these new materials
result in a more robust, reliable
heat exchanger, but it also means
that the unit will be lighter in weight
ChemiCal engineering www.Chemengonline.Com june 2016
is thermal expansion. If a hot gas is
entering the shell and there's cold
water in the tubes, they fight against
each other. If you are using different
materials in the tubing than in the
shell, they may expand and contract
at different rates, which is likely
to cause stress on the unit, causing
a possible rupture over time. " If the
exchanger wasn't designed to combat
thermal expansion or if someone
didn't account for the thermal expansion
that might occur during process
upsets or high-temperature cleaning
processes, there could be a safety
issue, " notes Herman.
He says expansion joints are one
way to deal with thermal expansion.
However, today's latest improvement
comes in the form of a floating
tube sheet-style exchanger, which
features a tube sheet that is fixed
in place on one end but allowed to
move within the shell at the other
end. " There's some spring action
involved so that the unit doesn't get
damaged if there's thermal expansion, "
explains Herman.
Improvements to alternatives
many exchanger styles, such as
plate-based and spiral technologies,
would not have been considered
for chemical process applications in
the past. However, improvements
to the design and technologies are
making today's models viable and
beneficial solutions.
" There has been a lot of development
in the components from
gaskets to welding technology to
materials construction that make
compact heat exchangers good for
very severe applications where we
may not have recommended them
previously, " explains Klas Abrahamsson,
director, process industry with
21
http://www.enerquip.com http://www.tema http://www.Chemengonline.Com
Chemical Engineering June 2016

Table of Contents for the Digital Edition of Chemical Engineering June 2016
