A Midwestern power plant faced a logistical challenge when it came time to replace its coal ash conveyor. The new conveyor was 110 feet long and weighed a hefty 138 tons—and it needed to be lifted 10 feet, so permanent legs could be installed to support the structure. Adding to the complexity was the low headroom and congested space inside of the power plant. These factors precluded the use of a crane, and jacking via bulky cribbing stacks was not feasible.
Alberici Constructors worked with Engineered Rigging to develop a solution. The companies started with a thorough review of the project goals and workspace challenges. Shop drawings were reviewed, and measurements were taken of columns, interferences, and tight enclosures. The data was used to model the space in Autodesk Inventor, a mechanical design application, and numerous route simulations were conducted to identify feasible solutions. After several brainstorming sessions and checks of the engineering in the RISA 3D model, an innovative three-part lifting strategy was developed.
1. Engineers designed a system to move a massive coal ash conveyor adjacent to the boiler at a Midwestern power plant. The system features 16 omnidirectional load skates, each with 10-ton capacity, and custom fabricated support beams connected via an integrated load stool. Courtesy: Engineered Rigging
First, the engineers identified how to move the massive conveyor adjacent to the boiler, a distance of about 20 feet, and position it on a grade. They designed a system (Figure 1) featuring 16 omnidirectional load skates, each with a 10-ton capacity, and custom fabricated support beams that connected via an integrated load stool.
After conducting computer simulations to ensure the system would interface with the conveyor and perform within the space constraints, the system was fabricated, built, and load tested in Engineered Rigging’s Arkansas facility. Videos were used to document the testing process and minor adjustments were made to the design as needed.
The second part of the strategy involved development of a lift plan and special fixture to set four hoppers onto the conveyor. Head height and space constraints required modeling of the process to ensure no interferences occurred during the actual lift. The combination of a pick-and-carry crane with a low-height lift fixture enabled success during this phase of the project.
For the final phase, a powerful, space-efficient solution was developed to elevate the entire assembly 10 feet so the conveyor’s support legs could be installed. A customized lift system, comprised of 24 lifting columns, was created.
Safety was a top priority, and Engineered Rigging designed the lift system so that a single operator could remotely control the 24 lifting columns. In addition, as the columns raised the conveyor, they mechanically locked into place, which enabled the installation of the legs without a suspended load. The system was tested using computer simulation to plan for a variety of scenarios, such as the ability to deliver a synchronized lift even with an unbalanced load.
“We needed to avoid any surprises when the equipment reached the plant,” explained Mike Beres, director for Engineered Rigging. “The ultimate success of the project was due to the well thought out plan that was rigorously tested.”
The modular lift system was assembled inside the plant in just two days of double shifts. The system lifted the 138-ton conveyer into place and positioned it on grade with a total lift time of 30 minutes. Tear-down was accomplished in a single day of double shifts.
“By having a breadth of talent, heavy-lift technology, and fabrication capabilities in-house, [we are] able to deliver rapid turnaround times for custom heavy-lift solutions,” said Beres. “From concept to completion, we fulfilled the power company’s bottom ash conversion project needs in just 16 weeks.”
Ryan Bearden, assistant project manager of Alberici Constructors, said, “The bottom ash conversion project’s success was based largely on the performance of the team during the nine-week plant shutdown when the new ash handling conveyor was tied into the existing boiler. The tight schedule required innovative solutions to complete the tie-in on time and safely. With Engineered Rigging’s equipment, we were able to safely preassemble most of the critical pieces of the project on the ground and rapidly raise them into place. This provided the project with huge safety and schedule benefits.”
—Christopher Cox, PE is president of Engineered Rigging, a global innovator in heavy lifting solutions.