A project that requires the HVAC piping system to be supported only from the floor is rare. Supporting pipe from above is the standard as it leaves space free of obstruction, providing mobility for the workforce executing the project. Creating modular fabricated skid assemblies is a new concept to most owners and design teams.

For example, consider a project where the design requirement for a 15,000-square-foot mechanical plant requires that all system piping be supported from the floor. It is not unique to use the floor for some support; however, it is unique in that support from above was removed as an option.

Recently, Shapiro & Duncan was faced with this challenge. A forest of floor supports is a major obstacle to productivity. This was a suitable project to maximize our capabilities; optimize productivity through prefabrication and modular assemblies; and give the owner and design team the best mechanical solution.

Our team comprised of project managers, virtual design construction (VDC) specialists, fabricators, logistics coordinators, trucking operators and on-site field personnel created fabricated modular skid assemblies to house and support all mechanical system components.

These included heating/hot water pumps, chilled water pumps, chiller piping connections, condensing boilers, steam boilers, buffer tanks, heat exchanger pumps and a heat exchanger.

However, creating modular fabricated skid assemblies was a new concept to the owner and design team. Therefore, it was essential that we get the ownership team behind our proposed solution during the initial planning phase. Once we had the ownership team on board, we were able to move forward.

Immediately, we faced serious implementation challenges. First was the location of the mechanical room. Typically, mechanical systems are supported by a concrete slab on grade, but since this mechanical room was on the second floor of the structure, additional weight as well as sound and vibration transmission were major engineering concerns.

Secondly, on the design side, we had to ensure the skid assemblies would be fully supported to maintain the structural integrity of the mechanical system. Not only in the final resting place, but also during shipment to the job site. Our skid assemblies would have to travel from our fabrication facility to the jobsite on lowboy tractor trailers, hoisted into the building and rigged to final placement.

Solution

Our mechanical solution began, as our solutions usually do, with full VDC coordination. The first step was to break the room layout of mechanical equipment into modular skids which were as large as possible (physical size and weight), liftable, riggable and transportable. In addition, it was important for us to carefully consider the constructabity restraints in our shop and the connection obstacles in the field.

Our design team contracted a third-party structural engineer to size the framework, support and bracing for all of the skids. DOT trailer load requirements were taken into consideration when it came time to stack skid assemblies on the trailers. Overpass clearances also had to be checked and verified on the delivery route. On the job site, we coordinated with the general contractor and subcontractors to ensure there were appropriate openings in the building to allow hoisting and installation of the skids.

Extensive cross bracing was required to keep skids from swaying back and forth during transportation. All braces had to be drawn and detailed in the building information model (BIM) and coordinated with other trades to eliminate clashes and conflicts. To further alleviate the concerns about sound and vibration, the modular skid design placed the steel-framed bottoms of the skids on isolated concrete housekeeping pads.

All modular skid assemblies were pre-fabricated in our 51,000-square-foot facility in Landover, Md., following lean construction principles that minimize waste, maximize time savings and ensure delivery of completed assemblies to the jobsite to help us stay on schedule. Our fabrication shop provides a controlled, safe environment that enhances productivity. Not surprisingly, this leaner, safer and more productive approach helped to build confidence of the ownership and design team in our mechanical solution.

Results

The plan came together and the team executed the work bringing the central plant to full operation as scheduled. The facilities director was an early adopter of our modular design concept and a valuable team member in bringing the rest of the ownership and design team on board. The final product is a show piece of which he is extremely proud of and he couldn’t be happier with the results.

In retrospect, there was a considerable number of moving parts in this project and the need for a great deal of coordination. The success of this project was a testament to the perseverance shown by our entire project team. Our VDC team worked well with equipment vendors in overcoming a host of hurdles to bring this concept to fruition. Once they came up with the idea of building the fabricated modular skid assemblies, this team never gave up on making it happen.

This was a design and construction requirement that our team had not previously encountered. Our people rose to the challenge and were able to think outside the box to deliver an innovative solution that delighted the client. Our people drive innovation.

https://www.shapiroandduncan.com/modular-mechanical-room-construction/