Reconstructed St. Louis cold room improves throughput

In this installment of What Works, problem-solvers meet trouble on a tight schedule at Sigma-Aldrich’s St. Louis chemical plant.

Demolition and reconstruction of a two-story, 11,000-sq.-ft. cold room within Sigma-Aldrich’s St. Louis chemical plant had barely begun when construction workers made a significant discovery.

“We were working on one of the building’s exterior walls when we discovered the columns were rotted at the bottom,” says Tom Kreher, vice president for McCarthy (www.mccarthy.com). The company served as construction manager on the $9 million project. The problem was that the plans called for these columns to be reused.

That was the first of several surprises that awaited the project team as they dug deeper into the 1930s-era structure. “You can plan and plan on a project like this,” Kreher says. “But until you start the demolition process, you can’t be 100% sure of what you’re working with.”

There were a few things, however, about which the project team could be absolutely certain. They knew they had 120 days to demolish and rebuild the space, without disturbing the chemical processing going on all around. They also knew that even a single day of overrun could wreak havoc for Sigma-Aldrich, which uses the 45°F cold room to produce more than 160 enzymes, proteins and other materials used in pharmaceutical research and production.

Originally a foundry, the cold room had been built on a concrete slab with cinderblock walls. Inside sat 24 1,000- to 12,000-gallon tanks and more than 20 columns. With as many as 10 products in production at any given time, the tanks were plumbed by quick-connect hoses for production flexibility.

Among the goals of the new construction was to improve the cold room’s throughput by simplifying and speeding the transitions between production runs. “We needed well-organized piping runs and transfer stations that allow us to configure the equipment in multiple ways,” explains Bob Ringering, director of production for Sigma-Aldrich.

The sheer complexity of day-to-day production requirements was a driving factor behind the construction project’s tight 120-day schedule. “We couldn’t just move production to other areas of the plant,” Ringering says, “That would be like trying to bake a cake, except now the pan isn’t available and you must use a cupcake pan to make the same cake.”

The original plan was to reinforce the masonry wall, install a new interior surface for cleanability, and add an exterior sandwich panel to improve the insulating value. That plan changed when demolition workers discovered that the lower third of the steel columns had rusted away.

Instead, the construction team was faced with shoring up the roof and taking down the entire wall while replacing its six load-bearing columns one at a time. Further investigation showed that the cold room’s interior walls, while in better shape than the exterior wall, would need reinforcement.

To keep construction on schedule, a new exterior wall was designed, detailed, fabricated, delivered and installed – all within a two-week time frame. The project’s structural engineers subsequently adapted their designs to use available steel to keep the project on track.

Meanwhile, questions arose over how to tie in the new and existing construction. The problem was that the H-shaped steel beams of the 1930s didn’t match modern beam dimensions. The old shapes weren’t manufactured anymore. To address this, the project architect changed the exterior wall to a thicker, insulated sandwich panel assembly that could be erected quickly and would tie into the adjacent masonry walls with specialized transition details.

Up on the rooftop, workers were discovering additional challenges. The original upgrade called for replacing only a small portion of the existing wood-deck roof. Conditions, however, were worse than anticipated. Eventually, more than one-third of the wood decking was replaced. Existing trusses required considerable reinforcement to accommodate new, higher-capacity rooftop HVAC equipment.

The new roof installation, however, would have to wait. For the project’s first two months, the cold room sat roofless, with the construction below exposed to the elements, so the room’s equipment could be brought in from above by cranes. Once the roof was torn off, it stayed off until the tanks, pumps and other new equipment could be delivered.

But for every obstacle that presented itself, a solution was found. Exactly 119 days after the original cold room was shut down, the new cold room was opened, on budget and on schedule. The secret to the project’s success: “We got really good at working through problems right on the factory floor,” Ringering says. “Whenever something came up, we’d get everyone together right there on floor and work toward a solution so we didn’t lose time. And it worked.”

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