As part of its $420 million health facility upgrade, the Palos Community Hospital in southwest Chicago is adding a 300,000-square-foot, seven-story east wing. It includes a powerful, redundant and efficient $48.9-million central utility and power distribution plant.
The new central plant connects to the existing distribution system via a complex system of below-grade utility tunnels, which contain the steam, water, chilled water, medical gas, fire protection and other piping systems. As the mechanical contractor for the project, F.E. Moran Inc.’s job is to connect the new and old mechanical systems rooms through a sloping underground tunnel.
Jason Smith, chief engineer for Illinois-based F.E. Moran, said, “There was no room for error in the limited underground space. We needed to translate design concepts and fabricated components to the field with great accuracy and precision. For a complex HVAC system such as the Palos Community Hospital, we opted to employ newly implemented BIM (building information modeling)-to-field tools.”
TransitionsThe new Palos hospital plant includes four steam boilers totaling 2,400 boiler horsepower, 5 chillers totaling 5,100 tons of cooling, and a set of plate and frame heat exchangers to provide 1,100 tons of free cooling. The new 3,000-kilowatt emergency-generating system provides back-up power to the campus. A redundant 15-kilovolt distribution system and three new double-ended substations serve the new central plant and campus. The underground tunnel that holds the mechanical systems slopes up while the steam piping must slope down.
“We are coordinating components down to the nearest inch, sometimes less,” Smith said. “Therefore, our model and the as-built conditions must match as closely as possible or we would end up with discontinuities that would cost time and money.”
In support of 3-D coordination amongst the entire project team, F.E. Moran created a structural model of the central plant and distribution system using QuickPen computer-aided drafting software. The structural model included the tunnel structure, utility plant structure along with footing and grade beams to accommodate underground coordination. Then, F.E. Moran used Trimble MEP Layout, which includes a robotic total station, handheld device and software, to bring the as-built conditions into the structural model.
Interoperable with most CAD and BIM tools, the robotic product allows F.E. Moran to bring data to and from the field easily through import-export functionality. All field points, such as hanger inserts, equipment pads or equipment objects, were also located in the model.
Because of jobsite conditions, time allowed and the margin of error on large jobsites, the precision defined in the 3-D model was difficult to carry out in the field. The robotic total station offered a connection.
ConnectionsOnce the pipes and metal components were designed, F.E. Moran’s team exported the field and control points from the CAD model to the robotic layout tool. Site engineers placed the robotic total station on the approximately 17,500-square-foot deck and subsequently calibrated positions by referencing the control points provided by the surveyor with the points input into the CAD model.
“Using the handheld robotic total station, we set approximately 500 individual field points in one day with one person,” Smith said. “Comparable conventional methods using a tape measure would have taken several days. When it comes to concrete deck insert layouts, we have increased our productivity by a factor of 10.”
During the concrete deck layout, F.E. Moran is usually working alongside other mechanical, electrical and plumbing trades as well as the concrete re-bar steel installation crews.
“It would have been cumbersome to have our two-person crews working in this area using a traditional tape measure and paper drawings,” Smith said. “The BIM field layout solution allows one person to work more efficiently around the clutter.”
Soon after, company officials used the BIM-connected robotic total station to layout steam piping within the sloping utility tunnel.
Continuing benefitsThe hospital tunnel incorporates several landings designed to meet requirements of the Americans With Disabilities Act. There are approximately four vertical risers with a “drip leg” to raise the main back up to the highest possible location, which accommodates the pitching of the steam main. Because the drip legs and the landings did not match up dimensionally, the elevation of the pipe through the entire tunnel varied.
Similar to the concrete deck, F.E. Moran workers imported survey control points provided by the civil contractor into the CAD software, and then designed the piping system adding field points with elevation. Once the components were fabricated, the company exported the points to the total station, calibrated the instrument onsite using the defined control points, and then placed the points in the field. As pre-fabricated pipe components arrived, construction crews could install the complex network of pipes quickly and accurately.
“We were able to exactly coordinate the support positions between the model and the field thanks to the interactive links between the robotic solution and the 3-D model,” Smith said. “The tight connection between our 3-D design and actual construction assures us that we’ve delivered the best possible solutions to our client, and that the client has an accurate as-built model from which to facilitate commissioning and facility management.”
F.E. Moran is using BIM on all of its projects, including work for clients such as Lurie Children’s Memorial Hospital, BP Bright Lights, Kraft Foods, WMS, Walsh Construction and the University of Iowa’s Pappajohn Biomedical Discovery Building.
The Palos hospital upgrade is on schedule for completion in late 2012.
This article and its images were supplied by Trimble, a manufacturer of building information modeling and global positioning products.