POWER March 2012 - 18

7EA Conversion Saves
Time and Money
ProEnergy Services (PES) was recently
contracted to install six Frame 7 DLN1.0
dual-fuel assemblies in Venezuela. The
problem: The lead time to purchase the
conversion hardware from the original
equipment manufacturer (OEM) would
not meet the customer's schedule. The
only option was for PES to convert the
fuel nozzles removed from a gas-only
unit to a dual-fuel configuration, a
process that had never before been attempted.
Starting
with new sets of dual-fuel
end covers and secondary nozzles, the
fuel nozzles were disassembled down to
the smallest component. The detail dimensions
of each component were then
found by laser scan to create a 3-D model
and followed by a dimension check
to validate the model. These component
3-D models were next converted into
individual SolidWorks models suitable
for design and manufacture. The individual
solid models were then virtually
reassembled to ensure proper fit of the
entire assembly before a single part was
manufactured. The individual solid models
were then used to create detailed
part drawings suitable for manufacture.
The entire reengineering portion of
the project was completed in just three
weeks. PES's knowledgeable and respected
vendor base made it possible
for all details to be manufactured, inspected,
and delivered within six weeks
of the project start date.
Many Technical Challenges
Converting a gas-only DLN1.0 fuel system
into a dual-fuel system required a
number of innovative designs, particularly
on the primary end covers and the
secondary nozzles.
Primary End Covers. One of the
first challenges the team faced was how
to introduce an atomizing air cavity
into the gas-only end cover. The team
first believed this to be an easy task,
as the dual-fuel nozzles already had the
cavity installed. A closer examination of
the covers revealed that the gas passage
on the gas-only end covers was installed
on the cold side of the end cover
rather than on the hot side, as on the
dual-fuel end covers. Unfortunately, the
position of the cavity overlapped the
atomizing air passage of the dual-fuel
18
covers, making it impossible to merely
install a passage similar to the dual
fuels. The 3-D model allowed the team
to identify a location in the assembly
for the passage that did not affect the
minimal wall thicknesses of the internal
passages, nor did it reduce the cavity
cross-sectional area (Figures 1 and 2).
The location of the gas passage on
the cold side also posed a problem
for mounting the fuel blocks: The fuel
blocks' mounting bolts would now pass
directly into the gas passage. This problem
was solved by deepening the passage
and installing isolation blocks
(Figures 3 and 4).
The team also took the opportunity
to correct another problem on the assembly.
During operation, thermal expansion
of the midsection has caused
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the upper braze joint on each nozzle
boss to crack. The team eliminated this
condition by constructing the insert out
of two pieces. Each of the two parts has
only one point of retention, thereby
reducing the stresses typically experienced
by the boss (Figures 5 and 6).
One of the last challenges the team
faced was that during the processing
of the end cover it was necessary to
remove a minimal amount of material
across the entire surface to ensure each
new boss was installed perpendicular
to the end cover mounting face. If too
much material was removed, the liquid
core would insert too far into the atomizing
air cone and impinge on the water
injection holes. This condition was
corrected by installing welded shims
under the fuel blocks, allowing for inPOWER
| March 2012
1. Conversion begins. ProEnergy Services
decided to convert a gas-only end cover (cold
side) for a Frame 7 DLN1.0 to a dual-fuel end
cover design. Courtesy: ProEnergy Services
2. Machine air passages. The gasonly
end cover design with the new atomizing
air passages installed. Courtesy:
ProEnergy Services
3. Braze block mounts. Fuel block
mounting locations were machined into the
end cover. Courtesy: ProEnergy Services
4. Completed assembly. The end cover
with the atomizing air passage and isolation
blocks installed. Courtesy: ProEnergy Services
http://www.powermag.com
POWER March 2012

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