Chemical Engineering March 2020 - 35

ponents: ammonia, water and atmospheric
air. However, the manufacturing
process is very energy- and
capital-intensive, using several turbomachines,
such as compressors,
pumps, tailgas-expansion
turbines
and several large motors. It is, therefore,
important for manufacturers to
maintain a high level of efficiency for
the process to remain profitable.
Rather than replacing complete
assets when their productivity starts
to drop, it is far more cost-effective
to repair the worn component and
even improve its design at the same
time. Modern three-dimensional (3D)
laser-scanning technology means
that the original OEM drawings are
not required; parts can be created
from the original component, even if
it has been damaged.
Boiler feed pumps
Many manufacturing plants use
steam to generate their own electricity
supply, and these systems rely on
boiler feed pumps to deliver a consistent
water supply. In many cases,
these important assets can perform
reliably for decades, but reduced efficiency
will take its toll on the cost
of operation. However, after so many
years, the OEM may not be in a position
to supply new parts, so an alternative
solution is needed.
Today, seal improvements and
efficiency upgrades through nonmetallic
wear parts and improved
rotor designs can be created and
manufactured using state-of-theart
equipment. Modern design processes
and additive manufacturing
techniques can greatly reduce the
lead time for new parts.
Retrofit programs can go much
further and alter the output of the
asset where demand from the
pump has changed over the years.
By changing impeller profiles or reducing
the number of stages, the
pump can be optimized for its current
application, often reducing the
power requirements and reducing
running costs.
Compressors
Large compressors are commonplace
in the chemical manufacturing
sector and they often operate around
FIGURE 2. Custom manufacturing of new components can reduce lead times
the clock. As such, reliability and efficiency
are very important, so rigorous
maintenance schedules and condition
monitoring equipment are usually
in place.
In many cases, compressor operators
hold spare rotors that can
be exchanged quickly, minimizing
downtime and allowing more time to
refurbish the rotor that has been in
service (Figure 1). However, this procedure
does not enable time to access
to the stationary section of the
compressor, which may also need
attention during an overhaul or a retrofit
project.
This can be mitigated by using laserscanning
technology and by creating
a 3D computer-aided design (CAD)
model of the rotor and the casing. By
combining the two, and using cuttingedge
technology, a performance chart
for the 3D model can be generated.
This can be compared to the actual
data from the compressor itself and
used to refine the model until it is a
true representation.
Modeling improvements
From this point, designers can introduce
improvements to the model
and establish their influence on output
and efficiency. Changes in impeller
profiles, enhancements to bearings
and labyrinth seals, can all be
simulated and evaluated to establish
the most beneficial designs.
Modern manufacturing and machining
technologies can be applied
to not only reduce lead times,
but also create more efficient components,
such as impellers with 3D
FIGURE 3. Precision fit of gas turbine parts increases efficiency
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Chemical Engineering March 2020

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