It’s an exciting time to be involved in the natural gas-fired generation market. Trends are coming together to create extraordinary opportunities to better serve electric customers.
Gas turbine technology is in a constant state of evolution, but roughly once a decade or so, the accumulated changes and new concepts are significant enough that the original equipment manufacturers (OEMs) give the equipment a new class designation.
The latest generation represents some of the largest, most efficient turbines the industry has ever seen. Designing and constructing an installation for such a big machine is a mighty undertaking. Fortunately for everyone, innovative aspects in the design of advanced class turbines are converging with emerging efficiencies in installation to facilitate their construction.
Fabricating Efficiencies and Enhanced Safety
Modularization is a significant factor in the innovation at work, and it is at least partially responsible for improvements in both safety and quality. Most of the turbine compartment for the latest generation of equipment is prefabricated off-site and then shipped in a series of modules, including much of the necessary piping. This approach reduces the need to stick-build enclosures, saves project costs and enhances quality control. Each hour of engineered and prefabricated efficiency saves multiple hours of field construction time.
Prefabricated modules and piping can be scheduled and sequenced to provide a balance of predictability and efficiency, ultimately yielding cost savings and reducing risks. As we have proved with our state-of-the-art fabrication facility in Appleton, Wisconsin, the efficiencies of modular design — for combined-cycle plants and other industrial applications — are amplified when leveraged into an integrated project delivery approach.
The ease of constructability is directly connected to how much effort the OEM has put into designing the hardware for that purpose, and so results can vary. But enhanced modularization means the right project partners can install the latest, largest equipment in a comparable timeframe to older technology with minimal additional complexity.
More Opportunities for Innovation
The competition to provide fully integrated engineering, procurement and construction (EPC) services around the newer technology has gotten tighter in recent years as some have left the market. One area where competitors can differentiate involves efficiencies around heat recovery steam generators (HRSG).
With the larger advanced class gas turbines, a lot more exhaust comes off the back end of the turbine, providing more available heat to make steam. That in turn is leading to bigger boilers, which presents another opportunity to modularize and gain construction efficiencies.
Often for these projects, the bidding will be based around the same turbine package, but there is more room for innovation around the HRSG, the piping layout and sequence of shipping. Those factors can add up and have a bigger effect on the efficiency of the project execution.
In selecting HRSGs, many customers prefer to buy the lowest-cost equipment but fail to consider the total installed cost (i.e., the purchase price plus the installation cost). We have found that evaluating the differences in total installed cost (TIC) — with a renewed emphasis on constructability — is a better way to determine the right fit for a project.
For balance of plant scope, there are significant potential savings by minimizing welding in the field, since much can be done on the modules in the shop at a fraction of the cost. Also, simple things like supplemental steel can be designed into the pipe rack as part of the structural steel package, then bolted and installed more efficiently with the rack steel.
Putting the Pieces Together
Imagine buying a toy for your child, and you can choose between one that comes in 1,000 pieces or one that comes in 10 larger pieces at a lower cost. Which would you pick?
It’s an oversimplified analogy, but it offers some insight into the advantages of advanced class gas turbine projects — and how an integrated firm can handle design and construction of projects at that scale.
In addition to increasing efficiency, modular construction can offer predictable results and mitigate safety risks when approached with proper planning and management considerations. 