Pennoni Perspective Volume 22 • Issue 2 • Summer 2018 - Page 10

Project facts: • 10,000 tons of refrigeration capacity (about 3,500 typical homes or 37,552 standard refrigerators) • Four 400 hp, 8,200 gallons per minute pumps (fill an Olympic size swimming pool in 20 minutes, 400 bath tubs in one minute or one bathtub in 0.15 seconds) • Stainless Steel piping up to 36 inches in diameter • Two 2,500 kva; 12KV electric substations For more information on this project, please contact: James Tardona Division Manager 302-351-5238 The DuPont Experimental Station in New Castle County, Delaware is the DuPont company’s largest research and development facility. The campus houses and operates a 15,000-ton refrigeration plant, requiring constant use of two massive cooling towers. DuPont initiated a replacement of one of these cooling towers, first erected in 1956. The wooden structure was once capable of producing 6,000 tons of condenser cooling water, but its old age was beginning to show. The proposed replacement tower would be a larger, more versatile and higher efficiency unit. Service continuity to the site was imperative and DuPont gave Pennoni an eight-month project window while not interrupting daily use of the facility. This construction window required the creation of an innovative design plan as the initial project timeline nearly doubled the window to 15 months. After evaluating multiple designs, re-siting plans and temporary cooling alternatives, DuPont and Pennoni partnered with Energy Transfer Solutions, a local representative for Evapco Cooling Towers, and M Davis Mechanical Contractors, a local Delaware firm. The team elected to develop a design that would shop fabricate the entire cooling tower system into modular units and then assemble the units by connecting them in the field. This would allow the new towers to be located on the same footprint as the existing tower, which was DuPont’s preferred location. With the extensive skid fabrication capabilities of M Davis, a modular skid design was used which was completely fabricated and assembled within one of their nearby facilities. The in- shop fabrication commenced in June 2017, an efficient three months ahead of the scheduled 10 | P E N N O N I existing tower demolition. While fabrication and assembly occurred, the demolition and civil, geo- tech and structural field activities occurred during the next four months. Using Revit software, the design team developed and coordinated the individual modular skid designs to conform to the required weight and dimensional parameters needed to transport, lift and maneuver each skid into place while accommodating the placement of the needed equipment, piping and supports. The first skid arrived at the job site in January 2018. To facilitate the skid placement, air skids were used to simply “push” the approximately 48,000-pound skids into their exact location for interconnection. The large 36-inch diameter piping and associated dynamic loads from four 400-horsepower (hp), 8,200-gallons per minute (gpm) pumps required an in-depth pipe stress analysis and custom pipe support design. The entire tower was completely assembled by the team and turned over to DuPont for start-up and commissioning on April 1, 2018. Pennoni’s electrical engineers teamed with Applied Controls Engineering, Eaton, and Rockwell Automation to design and fabricate pre- engineered and pre-fabricated electrical control rooms which house the many electrical drive units and controls required to operate the cooling tower fans and pumps. Like the equipment skids, these pre-assembled units were lowered into place in the field and electrically interconnected to the site power distribution system and cooling tower. This methodology of pre-assembling this entire structure is what enabled the project team to satisfy the original project schedule and allowed the client to start-up as scheduled on May 1, 2018, just in time for cooling season.