A gas supply operation in North America commissioned three new steam boilers in a plant expansion project that included a Robinson forced draft (FD) fan on each boiler. During the boiler start-up in a low-fire condition, the operation was experiencing severe duct vibration due to aerodynamic instabilities. After some fan equipment and ducting was damaged, the plant decided to investigate the issue and brought in a team of suppliers to troubleshoot the problem. Over three facility visits, the team was able to identify the problem and make the necessary operational changes to mitigate the issue.