Case Studies

BIM Makes Prefab Easy for Nelson-Carlson Mechanical


March 26, 2015

Nelson-Carlson Mechanical, a family owned plumbing and mechanical company that has been in business for almost 100 years, recently found itself faced with a growing requirement – especially with its government contracts – to use building information modeling (BIM). As Nelson-Carlson implemented the changes necessary to adopt a BIM workflow, the company quickly evolved from using 3D layout solely on an as-needed basis to using it almost every day.

“In the beginning, our use of BIM was strictly based on it being a requirement, but it was such a good fit with our prefabrication process that it really just took off from there,” said Tom Brown, a leading foreman’s instructor with Nelson-Carlson.

3D Disto Improves Speed and Accuracy

Brown, who has been in the trade over 30 years – 20 years as a foreman and 10-plus years as an instructor – helped the company jump into BIM with the purchase of its first entry-level layout robot, the Leica 3D Disto, around 15 months ago.

Prior to this investment, the company’s prefabrication process was more complicated. First, a foreman would take field measurements, which would then be used to generate single line drawings in AutoCAD. These 2D drawings would then be sent to the fabrication shop, where the piping is designed and readied for installation. The process required multiple steps and a number of manual operations.

Today, Nelson-Carlson uses the Leica 3D Disto to capture 3D information with discrete points and transfer dimensions directly from the field to the fabrication shop without having to use AutoCAD. The company also uses the Leica 3D Disto for collecting 3D as-built measurements as a basis for creating models.

Not only does this save both time and money, it also significantly reduces the potential for rework due to errors.

“We do a lot of remodel work where we go out and measure dimensions of rooms and then bring that information back to the fabrication shop,” said Brown. “Bringing information from the field into the shop and then having to accurately fit the pipes we created back into the field allows three opportunities for error. The 3D Disto gives us an anchor point to prevent that.”

With the added checks and balances throughout the process, expensive rework can be almost completely avoided, Brown said.

“It’s almost like it is its own control point because you are setting parameters on the front end, and then these parameters don’t change when you transfer information from one person to the next,” he said. “All of the coordination in the world doesn’t do any good if that info doesn’t get transferred to the field accurately.”

The 3D Disto is also helpful for accurately transferring dimensions from floor to floor in a building, where there is often no reliable line of sight, Brown said.

“We were recently working in a building with concrete columns that didn’t line up from floor to floor,” said Brown. “It wasn’t until we took the dimensions from the first floor to the second floor that we realized the numbers weren’t working because the columns were offset. Without this information, the pre-fab piping would not have fit and we would have cored holes through the floor in the wrong location. This would have been expensive and embarrassing to fix.”

Scanning Total Station Cuts Installation Time by One-Third

The company’s next step in BIM adoption is to purchase a scanning total station, which can be used for laying out underground piping. Brown has his eye on the Leica Nova MS50 MultiStation, which does scanning as well as layout.

Nelson-Carlson Mechanical plans to use the new equipment on two multimillion dollar projects it is currently working on that include remodeling new boilers in existing boiler rooms in two different high schools.

“The 3D Disto is quicker than the old way of getting measurements by hand, but nowhere near as fast as what we could do with a total station with scanning capabilities that has almost 10 times the range,” Brown said. “In larger areas where you have more underground work, it’s nice to have the range and a prism that it can follow.”

Brown believes the ability to scan underground, and use MicroSurvey software for field layout will enable him to reduce the amount of time a foreman is needed on each project by half. “But this is just the beginning,” he says. “The actual install time will be cut by a third, at least. Having the total station to watch ditch grade and location will minimize overdigging, which will save on material.”

On a conventional underground project, workers have to keep hubs clear, which prevents them from being able to pile dirt where it’s convenient and increases operator and plumber labor costs. With the MS50, “the total station/dxf/handheld units become my hubs,” he says. “When I’m done, I have my as-built locations for record drawings and the information for fabricating the above-ground piping. These jobs are becoming a lot faster.”

BIM Increases Productivity and Quality

As more and more general contractors require the use of BIM, project coordination has become smoother, making it easier for everyone involved to get their work done on time and on budget, Brown said.

Another huge benefit is the increased accuracy the overall process provides.

“Without an accurate model and coordination, crews go out in the field and then the information doesn’t get back to the office and it affects everyone’s productivity,” he said. “Not only has the use of BIM improved our accuracy, but it has enabled us to simplify and improve our prefabrication process, which improves productivity and enables us to better serve our clients.”