POWER May 2017 - 43

TECHNOLOGY
2. 3-D printing with metal. Selective
laser melting (SLM) and direct metal laser
melting (DMLM) use lasers to melt metallic
powder one layer at a time, to build complex
gas turbine components. Courtesy: GE Oil &
Gas
cycles, which ultimately benefits the customer, "
Cecconi explained.
One of the most significant advantages
to the additive manufacturing process is its
quick turnaround time. According to Siemens,
pieces produced via additive manufacturing
can be produced " up to 90 percent
faster " than those produced through traditional
means.
More specifically, Siemens boosts turnaround
times 75% faster for research and development
and prototyping, and lead times reduced up to
60% for burner tip repair (Figure 3).
" Recently, we did apply this technology
ponents will be more or less ready for the
application, " Navrotsky said.
GE has similar reasons for choosing the
DMLM process. " This process has the advantage
of the best dimensional accuracy
compared to other additive processes, and it
is also the most widely known and tested. A
lot of different alloys have been developed
and qualified for it, " Cecconi said.
LMD. The LMD process also uses metal
powder for the 3-D printing process, but instead
of the powder being laid on a plate, it is
supplied from a nozzle and injected directly
into the beam of the laser.
According to Navrotsky, LMD is not without
its drawbacks. " You can do much bigger
components much quicker, " he said. " But
then you need to do the final machining. "
EBM. EBM is very similar to the SLM process,
differing only in that the EBM process
uses an electron beam as opposed to a laser.
EMB is somewhat more limited in that it can
only be used with a limited number of metals.
" At GE, we're exploring and testing many
different additive processes as every one of
them has specific pros and cons that make
them more or less suitable for specific industrial
applications, " Cecconi said.
Pros of 3-D Printing
The advent of additive manufacturing has
opened a whole new world to the energy industry.
While there are certainly limitations
to what can be achieved through 3-D printing,
the technology has allowed engineers to
address longstanding difficulties in innovative
ways.
" Additive manufacturing allows us to develop
parts and products more efficiently,
with better performance and cost-effectively,
and it accelerates the speed at which we can
bring products to market: production times
are drastically reduced-the finished product
can be completed in weeks instead of
months, significantly reducing production
May 2017 | POWER
for the design of new components-design
and validation. Just to do the design of the
blades and vanes it usually takes about one
year and a half, two years, in order to do the
design and get the prototype blade, which is
custom, " Navrotsky said. " With one of our
small engines, we in two months-instead
of in two years or one year and a half-we
did the design of the blade, and we did the
manufacturing of the blade, and we put this
blade into the engine in order to validate the
improvement of the cooling design. "
Through its agreement with Total Refining
& Chemicals, " GE Oil & Gas will use advanced
manufacturing methods, such as 3-D
laser scanning and DMLM, to 3-D print impellers
on a 1/1 scale, leading to a significant
reduction in lead time-from months to an
average of three weeks from 3-D laser scanning
availability-higher technology sophistication, "
Cecconi said.
Additive
manufacturing
also
removes
many limitations of the traditional manufacturing
process. As Navrotsky said: " If you
can dream it, we can print it. "
Such was the case for the Krško nuclear
power plant. The plant's operators needed
to replace a part of its fire protection pump.
Unfortunately, that particular piece was no
longer in production. The operators did not
want to replace the entire pump and decided
to find out if they could have a replacement
impeller printed.
The impeller that needed to be replaced had
been in operation since 1981 and was designed
and produced by a company that is no longer
in business. More specifically, the piece is " a
metallic, 108mm diameter impeller for a fire
protection pump that is in constant rotating
operation, " a Siemens release explains.
The part had to be reverse engineered,
with Siemens' experts developing a " digital
twin, " which was then used to create the new
3-D printed part.
The technology isn't just useful in reproduction,
it also allows for greater customization,
which in turn can lead to improved
design. For example, according to Siemens,
the 3-D printed burner nozzles it produces
www.powermag.com
43
allows for co-firing at higher combustion
temperatures due to their innovative design.
" As a result of a redesign of the SGT-700/800
nozzle and its lattice structure, which was not
possible with conventional production methods,
these turbine types can now handle up
to 60 percent hydrogen, and we are aiming
for 100 percent, " according to a Siemens
factsheet.
The additive manufacturing process, while
certainly not cheap, can be the best-cost option
in certain cases. Complex components
that in traditional manufacturing might be
comprised of more than a dozen pieces welded
together can instead be made in one piece,
saving money on time and materials. " Compared
with traditional production techniques,
additive manufacturing allows for the production
of a single piece instead of multiple
parts that would need to be brazed, welded,
or bolted together, " Cecconi said.
And Cons
Unfortunately, it's not all pros when it comes
to additive manufacturing. Cost remains a
significant barrier to the widespread adoption
of the technology, Navrotsky said. " In
general for the application of this technology,
the equipment itself is still quite expensive,
so we are coming from like €0.6 million up
to €1.5 million for the different machines, "
he said.
Beyond the machines themselves, the raw
materials are also quite costly. " The metallic
powder which we are using for the components
is also expensive, " Navrotsky continued.
" In some cases, the price for the powder could
3. Speedy repair. Using additive manufacturing,
Siemens can repair burner tips 60%
faster than using traditional methods. Courtesy:
Siemens
http://www.powermag.com
POWER May 2017

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