March 15, 2008

Extend EOH tracking to the entire plant

Peter S. Jackson, PE, and David S. Moelling, PE, Tetra Engineering Group Inc.

Put it all together

Tetra Engineering Group has developed EOH programs for many combined-cycle plants. They range from programs that cover only the HRSG to those that cover a complete plant, including its gas and steam turbines. In our experience, the best ways to reap the full benefit of these programs are to:

• Keep EOH formulas simple but realistic. Develop a system that can capture significant plant upsets without too much effort. Avoid excessive detail, because it can result in an unworkable system.
• Expect minimal guidance from vendors. Be prepared to develop your own maintenance bases.
• Automate service tracking via your distributed control, performance indicator, or similar system. Make sure the system you use has basic data validation and replacement functions. The last thing you need is a tracking system that crashes due to the failure of an instrument.
• Consider renewal factors. Does overhauling a system or component make it as good as new again, or something less?
• Focus on the big-ticket items if your budget is tight.

Leveraging the effort

A good EOH program can also help justify the replacement of substandard components or the upgrade of an existing system (such as for water chemistry). In addition, it can justify taking action to address water chemistry or fuel problems reflected by higher EOH values. Finally, the actual operating and cost data developed by a strong EOH program are very helpful when developing dispatch cost and variable O&M cost studies (Figure 4) for plants that must routinely bid into competitive markets for operating hours.

4. Pay the freight. This chart shows a typical distribution of variable O&M costs, in $/MWh, for a combined-cycle plant. A plantwide EOH program can make managing these costs more precise. Source: Tetra Engineering Group Inc.

—Peter S. Jackson, PE (pjackson@tetra-eng.com) is director of field services, and David S. Moelling, PE (dave.moelling@tetra-eng.com) is chief engineer at Tetra Engineering Group Inc.