Modular Construction Gains Ground

Issue 3 and Volume 112.

Rising costs, labor shortages, safety and other factors favor modularization for power plant construction projects. With the potential benefits, however, come some risks.

By Steve Blankinship, Associate Editor

“Plug and play” is a term often applied to electronic devices, especially computers and video games. It is less often used to describe large, expensive and complex facilities. And few facilities are larger, costlier or more complex than power plants.

But a look at how far modularization has come in recent years suggests plug-and-play might not be such a far-fetched idea. The fact is, more major power projects are being built using ever more—and ever larger—modularized components.

The factors pushing modularization (or pre-fabrication, as some prefer to call it) are many. They include cost, schedules, lack of skilled labor and safety issues.

“It’s no news that 25 years ago there were more pipe fitters, electricians and millwrights in the construction force,” said Bob Heina, principal of coal plant generation for Burns & McDonnell. “Today, even if you can get enough people, they don’t have the experience they had in the past. Lack of construction skills and experience means a lot more engineering is going into the power plant.” He said more details are engineered today to enable construction labor to build the plant with fewer details left for the construction force to interpret. In addition, constructors are building more things on the ground, then lifting them into place. “It reduces construction labor and time.”

Heina, who most recently was involved with Kansas City Power & Light’s 850 MW Iatan plant, has had a lot of experience with fabrication, both good and bad. “When you try to prepackage everything, it’s certainly not without risk. We try to have installation contractors on board and available to oversee factory assembly. You try to get the construction contract awarded early enough so the contractor can go to the test or set-up demonstration and confirm that all the dimensions are correct.”

And although he said he’s amazed at how precise modern technology allows surveyors to get with parts of power plants sometimes separated by hundreds of feet, he still sees a few worrisome elements with current surveying. “We seem to see more errors in either location or installation; a lot more fabrication errors than we saw 25 years ago.” Details like bolt holes, flange locations and connections. Today with 3D design the dimensions are in small fractions of an inch. “Unfortunately, pipe fitters still build with yardsticks,” he said. “It used to be if there was a one-inch bust-out in the field, engineers would never hear about it. Construction would just pull it over and weld it up. Today, it’s a big deal.”

The highest risk on any power project is not the capital, equipment or materials cost, but the cost to do the installation, said Heine. Burns & McDonnell typically uses a multi-contract approach. One of the first things is to buy the steam turbine with a performance contract. “Once we have the steam flow nailed down we can buy the boiler and after that we can buy a lot of equipment. We start producing drawings and preliminary layout. Then we start moving dirt and designing substructures and foundations,” Heine said.

Prefabricated Safety

Ty Larson, construction manager for Bechtel, has his own list of reasons to modularize. Topping his list is safety. “The less man-hours on site, the less congestion and therefore the less chance for job site injuries,” he said. “Building as much as you can inside a shop means no wind, darkness or weather issues.”

This bag house module was built off site and delivered by barge to We Energies’ Elm Road Plant in Wisconsin. It measures 48 x 49 x 20 feet and weighs 100 tons. Photo courtesy of Bechtel.
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Dennis Fedock, manager of construction technology for Babcock & Wilcox (B&W), said he also views modularization as a safety enhancer. “Anything you can do on the ground or under controlled conditions is a lot more efficient that trying to build in place in the air,” he said. “There aren’t as many skilled workers who can work well in high places.”

Complicating things are federal requirements that mandate 100 percent tie-offs. That means a worker can’t move around without changing the rigging that keeps him or her completely secured to the structure at all times.

Next on Larson’s list of positives is the quality that comes from a shop. This factor is especially critical today due to the lack of skilled craft workers. “Everywhere we go we hear about the aging workforce and the ability to attract welders and riggers and so forth,” said Larson. “So it can be easier to find a few good people and have them in shop where conditions are optimal.” That approach lends itself to shortening the construction schedule.

Modularization also means fewer shipments that have to be received at the construction site. It’s usually easier to get a module in one piece than receive 100 pieces for the same component, then store and track the materials. Pre-fabrication also can mean fewer site personnel—including superintendents, engineers and procurement specialists. Finally, off-site construction lets a project take advantage of lower-cost overseas labor.

Fabrication Leader

Babcock & Wilcox may do more modularization than any other original equipment manufacturer in the power industry. Fedock traces the company’s move toward more modularization to three significant events. The first was the conversion of the Zimmer plant in Ohio—originally planned as a nuclear unit—to a coal-fired plant after it was already under construction. The second was the boom to retrofit massive environmental control systems onto existing coal plants. The third was the evolution of the heavy lift cranes that offered ever-increasing lifting capabilities.

Zimmer was originally being built as a nuclear unit. “With much of the original construction already in place, very little lay down area was available for the coal conversion project,” said Fedock. The owners emphasized that maximum modularization was a pre-qualification to the bid. The bigger the shop-assembled pieces were, the better. B&W modularized boiler components, including horizontal convection pass surface and pendant primary superheater and reheat superheater outlet banks, absorber towers, the electrostatic precipitator, the air preheater, flue and duct, two startup boilers and 14 pulverizers.

The utility also provided a Lampson Model LTL-1200 transi-lift crane with 1,200 tons of capacity on-site for both barge off-loading and final installation. “The heaviest module erected on the project was a fully shop-assembled precipitator field weighing approximately 600 tons. It was lifted into place from a radius of approximately 100 feet,” said Fedock.

The Zimmer conversion set the stage for things to come, including retrofitting wet scrubbers at AEP’s Gavin plant. “Most of our expertise is based on fundamental knowledge and experience gained in modularizing boiler components and accessories, selective catalytic reduction components and wet flue gas desulfurization systems” said Fedock. “We retrofitted a lot of environmental equipment on existing plants, and many of them were water accessible, which plays a major role in how the job is approached.” He said that the high alloy base materials from which the absorber towers are constructed, as well as the configuration of the towers, are factors driving modularization.

“The towers could be cut into five or six modules and be totally shop-assembled with internals and externals completely installed. They could then be shipped by barge to the site, then moved from the barge unloading area to the heavy lift crane for final installation. Recognizing these opportunities helped kick off the trend toward upscaling what B&W did with modularization.”

Cranes and Water

Availability of huge cranes and accessibility to water transportation are modularization’s two most crucial enablers. Modern cranes have strength and agility far beyond what was available during the last power plant construction boom.

Fedok said that during the lull in power plant construction during the early 1990s, one U.S. crane manufacturer’s decision helped enable today’s modularization potential. “After the U.S. construction downturn, many support industries withdrew, including crane manufacturers. But Manitowoc continued to build even bigger high-capacity mobile cranes. They started at the 300-ton range and extended upwards to 1,000 tons. ”

Access to such cranes, combined with the fact that most of the company’s retrofit work took place at plants accessible to water, let B&W fabricate to an even greater extent, both at remote locations and on the ground at plant sites.

Buy-in Needed

Bechtel’s Larson said that modularization requires full cooperation from all parties engaged in the project. “You have to have cooperative vendors who are willing to work with you. If you have one that doesn’t want to work that way, make other plans.”

The availability of big, agile cranes is one crucial enabler of modularization.
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Chris Molzone of Hitachi said that the U.S. power industry historically has not fully embraced all that modularization can offer, in part because of the way construction practices evolved. In Japan, for example, nearly all power plants are near the ocean. In the United States, many are landlocked. Because Japanese projects tend to be so water-oriented, Hitachi has done more modularization than might have occurred elsewhere.

“Modularization is not new to us,” said Molzone. “Hitachi has been pushing to modularize and we have systems that can increase its use even at landlocked sites. Most people build boilers from the back, but we have a way that you just build from the ground and jack them up into place. But if you do that, it means you have to procure and engineer differently. “The U.S. mindset is different.” He said such a degree of modularization requires an entirely different project management and engneering process for U.S. erectors to consider.

Larson cautioned that modularization can affect the entire project schedule. “If you had a schedule that calls for something that would have taken 16 months without fully utilizing modularization and you decide you want to fabricate to a greater degree, the vendor might need 18 months.”

Careful analysis is needed to determine if a component will be cheaper to assemble in a shop and then transport, or assemble it at the site. Modularizing also means less room for error and less flexibility to “make it work” once the component gets to the site. “You have to make sure it will fit,” said Larson. “You need to take extra shop measurements and keep asking for more. You increase the risk of error. If it gets to the site and it doesn’t fit, you have a big problem. You have to find any problems in the shop and fix them there.”

Modularization can also occur in the field as well as in the shop, said Mike Garkawe of Hitachi. Hybrid modularization means bringing large fabricated components to the site where they are further integrated with other components. Such additional site fabrication requires large lay-down and staging areas.

“Many components at MidAmerican (Energy’s) Council Bluffs plant (where Hitachi provided the supercritical boiler) were brought into the boiler cavity,” said Garkawe. “That lets you build the boiler much faster.” Reducing boiler construction time can be a major cost savings. Assembling small components in the boiler cavity can be unsafe and time consuming. As a result, “if you have some lay down area and can make a lot of components away from the boiler cavity and then bring them in, you are much better off.”

Although modularization relieves some on-site construction logistics, it increases others, including those that involve delivering modules from their fabrication point to the plant site.

“These things can be coming from Asia, Europe or Canada and there are some big challenges that we have to get worked out,” said Larson. “Sometimes Bechtel is responsible for shipping, sometimes the manufacturers (are) and sometimes (it’s) a little bit of both.” And the cost of cranes for movement and rigging isn’t cheap. “You must obtain the cranes a long time in advance. And you have to have a heavy haul plan,” he said.

For We Energies’ Elm Road coal plant, some components were built in Asia and arrived in the U.S. by sea at the mouth of the Mississippi River. From there, they were barged upriver to a shop in Milwaukee, then along Lake Michigan to the job site. Elm Road’s coal silos, which otherwise would have been assembled from 20 to 25 individual pieces at the site, were finally fitted together at the site from two large pieces. “A lot of work went into them, but it worked very well,” said Larson. “We had people at the (manufacturing) source in China camped out for about a month to make sure it was done right.”

Then, too, there is the issue of “shipping steel,” which is the steel used to package and protect modules during shipping and handling. The man-hours necessary to remove it must be well thought-out. “You need to plan so you don’t have to cut it in a hundred places,” Larson said. “Then you need to figure ways to use that steel on site or sell it for scrap.”

Gas and Nuclear Modularization

Combined cycle gas-fired plants, although highly standardized and somewhat modularized to start with, can also benefit from pre-fabrication, assuming they have water access. Larry White of Hitachi cited a combined cycle job where pipe racks were delivered in six modular towers weighing 200 tons each.

“It was all barged in with access to an inland waterway on the East Coast,” he said. That included instrumentation, too. He said natural gas-fired plants lend themselves to modularization because there can be four gas turbines or four heat recovery steam generators in a row.

Workplace rules requiring 100 percent tie-offs for construction workers favor modular approaches.
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A critical element, however, is water access. “Without it you have nothing,” he said. That’s because moving large components by road can be difficult at best. And any load large enough to require escort makes things worse. Every state through which a large load is shipped requires permits and collects fees for the road use. As a result, the costs and time required for permitting can severely limit “over the road” delivery sizes.

Tom Beverly, who is involved with Hitachi’s nuclear operations, said the company is looking at modularizing new nuclear projects in the United States. “With this surge coming there are various areas of preparation we are looking at. I think Japan is way out ahead of the U.S. on this,” he said. “The Japanese are modularizing everything from the major plant components to piping and valves. Because of the long lead time for nuclear, there’s tremendous time savings in bringing completed modules to the site.”

He said one plan could be to have a modularization plant that can bring in all the various components needed for a complete plant construction.

Most construction experts agree that the more modularization that can be done, the better. They also seem to agree that the trend for more fabrication will grow. But growth requires understanding the risks and tradeoffs and knowing how to correctly identify the costs and benefits.

“It all boils down to careful planning,” said Larson. “People have to work together: engineering, procurement, construction, shop quality control.” After all, he said, construction and engineering firms have high risk and a lot of money at stake.