In September 2015, Fast Fix 8, the $62-million-dollar bridge renovation project of the Tennessee Department of Transprtation (TDOT), was nearing completion in Nashville. At this stage, a Versa-Flex BDM system (poly, shear) was scheduled to be applied on four pairs of bridge surfaces. The bridges had been repaired by the city numerous times since they were built in 1968.
Challenges included minimizing disruption of interstate 40, a massive downtown highway with average daily traffic (ADT) of 130,000, and meeting a tight deadline on a weekend-only work schedule. ProTech Coatings (Salt Lake City, Utah), the Fast Fix 8 contractor, reached out to SprayWorks Equipment Group for an automated solution that would speed up the process.
One major challenge was dealing with a short timeline where contractors could only work on weekends. This shows one of the four bridges worked on, just as the project began. Photos: Courtesy of SprayWorks Equipment Group
Deterioration of the bridges was a huge safety issue and a major concern for TDOT, as there had been three instances of chunks of concrete from the bridge deck falling on oncoming cars during the summer of 2013.
This picture shows three two-man working teams, each on a Spraybot. The teams worked through the night to prevent distruption in traffic flow.
Turning to Automation
The team at SprayWorks Equipment Group, a polyurethane equipment supplier based in Canton, Ohio, knew spraying Versa-Flex by hand on 45,000 square feet of bridge surface in just two days would be a tall challenge. Instead, the company used three lightweight automated spray robots, weighing 340 pounds each. SprayWorks representatives taught the contractor's applicators to apply coatings with the adjustment of a few settings on the spray robot's control panel, and they also assisted with execution. Each Spraybot operated with a two-man working team - one to guide the robot and one to manage the hose, which transported the chemical compounds from a mobile rig to the application point. Having a smaller team applying material with the Spraybot freed up other workers to attend to other requirements of the project.
Aerial view of two Spraybots running simultaneously, with two-men crews.
Speeding Up the Process
Automation is in high demand by architects, engineers and contractors, as projects are expected to be completed faster, more accurately and, in many situations, using the construction manager/general contractor (CM/GC) project delivery method, designed to help accelerate projects that included Fast Fix 8.
Spraying 6 gallons per minute of material, the automated robot was able to evenly and consistently apply a seven-foot-wide pass of material at 80 mils thick (.080 inches) with just a single pass. Each pass covered more square footage than would have been covered by hand, which would typically be three to four feet wide with a variable pattern. The robot's accuracy also helped to minimize starting and stopping points after each pass.
The latest version of the Spraybot robotic spray applicator: The Spraybot has the ability to apply variable millage with a consistant and accurate pass.
Decreasing the Work Load
Spraying by hand can be inconsistent, and applicators are required to go back and check their work to ensure that minimum application requirements have been met. In some of these cases, additional applications of the material are needed. Not only did the automation expedite the application process, but it decreased the amount of applicators needed to apply the material.
Other project concerns included windy conditions, which often require even more manpower, but by using the Spraybot, no extra manpower was needed. Each robot came equipped with a wind screen, preventing overspray onto passing vehicles and nearby structures. The automated equipment used relatively little power, operating on a 90-volt DC electric current and Honda E-U 1000 generator, which was stored on the robot's cart. This eliminated the need for additional generators for power and additional power lines, which would have required additional workers.
Finalizing the Project
Total time on the entirety of the project was decreased from the anticipated three years to only seven months. Additionally, only 10 weekend closures were needed, as opposed to the 13 weekend closures expected. Ultimately, ProTech Coatings was able to complete the project ahead of schedule — allowing the busy city traffic to return to normal.
About the Spraybot
The Spraybot was designed in 2004 by inventor Jim Davidson, owner of SprayWorks Equipment Group. At 340 total pounds, including the spray head, cart, generator, wheels and toolbox, the Spraybot is easy to transport and the spray head is easily removed. The equipment accurately adjusts for millage and thickness: +/- 2 mills coatings and +/- 1/16 inches SPF. The max operating slope is 9.5 degrees, 2:12. Output is provided at up to 50 pounds per minute of spray foam and up to six gpm Polyurea output. By 2015, the Spraybot had reached a milestone of over 300 bridge applications.
Learn more and see how the Spraybot works:
Watch the Spraybot in action on the Fast Fix 8 project: