A fertilizer producer in the Midwestern United States transported petroleum coke through a square chute ending in a cylindrical spout. The internal transition caused material to enter the spout unbalanced, leading to bridging. Bridging happens when an arch of condensed material builds around the downspout, preventing cargo from flowing. To loosen the material, operators installed two vibrators on each chute, but they damaged the walls and seams of the hopper. Staff had to re-weld and wrap a 2 inch (50 mm) ratchet strap around the chute to keep it from separating. Bridging caused several unscheduled shutdowns per week and required a worker with an air lance to clear the obstruction, which affected production and raised the cost of operation.
Martin Engineering was invited into the plant to assess the situation and offer solutions. The technicians installed two 35-liter Martin® Hurricane Air Cannons. Connected to the plant's compressed air system, they fire a powerful shot of pressurized air in response to a positive signal from a solenoid valve. The unique valve design provides more force to loosen bridged material using less air than larger cannons. One cannon was fitted onto the existing clean-out port, pointing downward into the cylindrical downspout. The other was installed on the opposite side above the transition -- the common bridging point -- to sweep the back wall of the chute and loosen any compacted material that could lead to clogging.
Installation of the cannons was performed during scheduled downtime and required minimal changes to the chute structure. The cannons are easily fired from a nearby solenoid box when needed or can be set on a firing schedule based on the needs of the application. Since installation, operators have reported zero downtime due to clogging and no need to pull workers from other essential tasks to lance obstructions. "We're very pleased with the outcome," said a manager close to the project. "The shutdowns were getting unsustainable, so this has offered a fast return on our investment." Plant managers are planning to install cannons on other problem chutes / head boxes in the future.