Powering Up an Age Old Design

Reverse engineering helps power companies generate up to 15 % more power

by david olson, Verisurf Software

Verisurf Software helps power companies reverse engineer steam turbine rotor assemblies to support new and improved bladding. Southern California Edison, GE, Alstom, Siemens, Mitsubishi and Toshiba have all used Verisurf Software to create ‘as built’ CAD models of existing rotor assemblies. Why go to all that trouble you might ask? After 130 years, steam turbines are still a wonderful and powerful design generating approximately 90 percent of the electrical power in the United States.

Most of the steam turbine power plants in use today around the world were built over 60 years ago, long before CAD and advanced surface and fluid analysis.

Replacing old blading can increase power output by 8 to 15 percent.
Replacing old blading can increase power output by 8 to 15 percent.

When plants are taken offline today for maintenance, repair and overhaul, there is an opportunity to upgrade turbine rotors with more efficient blades that are capable of generating 8 to 15 percent more power from the same rotor configuration.

The turbine housings are extremely large castings and the rotor assemblies have tight tolerances, which makes the design and integration of improved blades tricky.

This is compounded by the fact that drawings and detailed plans for the original rotor assemblies do not exist; requiring a detailed ‘as built’ dimensional CAD model of the entire rotor – coupling face, shaft, bearings, steam seals and blading area.

Southern California Edison created Edison ESI in 1987 specifically to support the metrology requirements of its nuclear and conventional electric power generating plants.

In the beginning Edison ESI employed a team of people to capture 2D measurements using traditional hand tools (rulers, tapes, calipers, plumb-bobs), then return to their offices to assemble the hand measurements into a 2D drawing.

As metrology software and supporting digital capture devices evolved Edison EDI standardized on Verisurf Software as their application of choice.

“My team and I have traveled all over the world providing ‘as built’ and ‘best fit’ data for turban fan retrofits,” said Peter Tavis, Quality Control Inspector for Edison ESI. “Our data has always been considered to be highly accurate gaining us the reputation as the ‘go to’ source for reverse engineering of rotor assemblies.”

Turban rotor assembly tolerances are extremely tight. Errors can be catastrophic.

Probe data collection in progress on main rotor assembly.
Probe data collection in progress on main rotor assembly.

A typical turban fan can rotate at 3,600 RPM.

At this speed the blade tips are turning at close to mach speed.

All components, including coupling face, bearings and shaft must match the rotor exactly.

Verisurf Reverse Software was selected for its power, flexibility and ease of use.

It is capable of processing scan or probe data to produce usable 2D or 3D manufacturing models.

Developed on a robust CAD/CAM platform, Verisurf Reverse is able to support the final deliverable of an intelligent CAD model.

Retrofit turban fan manufacturers are able to import the data directly into their CAD/CAM application and provide a ‘best fit’ for the new fan. The reverse engineering of the rotor assembly requires probe data as opposed to scan data, which means fewer data points but greater accuracy.

Typically a Faro Platinum portable CMM was used for probing.

Given the nature of the rotor assembly the final output is a 2D CAD model.

Due to location and size of steam turbans portability of the overall metrology solution is important.

Verisurf Software operates on a 64-bit, PC laptop platform. Portable CMMs and scanners, though highly sensitive measuring devices, are also easily transported in suitable travel cases.

Since Verisurf serves has a common metrology platform, compatible with all digital measuring devices, it is just a matter of selecting the right digital measuring device – fixed CMM, portable CMM, laser scanner, laser radar, etc. Verisurf supports them all.

Verisurf Software, Inc. is a 3D measurement solutions company, committed to delivering advanced computer-aided surface analysis, inspection, tool building, assembly guidance and reverse engineering solutions.

Verisurf software helps manufacturers produce higher quality products in less time and at a lower cost with automated, Model-Based processes.

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