COATLIFE Software Saves Money, Time for Combustion Turbine Operators.

SAN ANTONIO -- Inspecting the coating on a gas turbine blade is a costly and tedious process that requires shutting down the turbine and destroying the blade itself during inspection. Southwest Research Institute(R) (SwRI(R)) has developed COATLIFE Spreadsheet Program 4.0, a nondestructive analytical tool that can cost-effectively and efficiently predict the oxidation and thermomechanical fatigue life of combustion gas turbine coatings and coated blades under variable operating conditions.

Turbine blades require protective coatings because of the extreme temperatures they face during operation.

"COATLIFE was developed to compute the usable coating life through a mechanistic treatment of relevant coating degradation mechanisms such as oxidation, spallation and inward diffusion," said Dr. Kwai S. Chan, an Institute scientist in the SwRI Mechanical and Materials Engineering Division.

The program was developed under funding from the U.S. Department of Energy through an Electric Power Research Institute (EPRI) subcontract. COATLIFE is one of the key enabling developments supporting the larger EPRI program addressing CT hot section life management aimed at reducing O&M costs by at least 25 percent.

The current practice requires turbines to be out of service for about a month while a blade is sectioned and the coating layers examined. Because of the extensive downtime, blade life evaluations can be done only during a long outage, scheduled or otherwise, of a gas turbine machine. Compared to this method, COATLIFE 4.0 eliminates unnecessary machine outage and avoids destroying blades that could still be in good operating condition. In addition, COATLIFE 4.0 provides relevant information for planning maintenance schedules for blade refurbishment, repair or replacement.

"This program provides tremendous cost-savings for users by optimizing maintenance schedules, extending blade life by eliminating destructive testing methods and estimating the remaining life and usability of the existing coated blades," Chan said.

A single turbine blade costs between $15,000 to $40,000. Add to that the costs for a month-long sabbatical to retrieve a blade; perform a metallurgical evaluation; make the decision to replace, repair, or to continue using the blade; insert spare blades to replace removed blades; and finally resume operation. In addition, the costs for an unanticipated plant outage can range up to several million dollars.

COATLIFE 4.0 is easily expanded to add new coatings as they are developed. The software is not limited to coatings or coated blades in land-based gas turbines. It can also be easily adapted to life-prediction applications for coated hot section components in aero-engines, as well as other industrial coatings.

For more information, contact Chan at 210-522-2053 or [e-mail].

SwRI is an independent, nonprofit, applied research and development organization based in San Antonio, with more than 2,900 employees and an annual research volume of more than $399 million.