The client operates two bulk unloaders at its facility in South America. The boom on one unloader buckled due to a snag event, when the grab bucket struck the edge of the vessel opening during operation.
Liftech provided engineering services for temporarily securing the damaged unloader, structural concepts and design for boom stabilization, and structural concepts for boom removal and repair. Other engineering services included a boom failure investigation, snag time history analysis to evaluate multiple modification concepts, structural design for a new snag protection system, and basis of design, specifications, and design review for procuring the snag protection system.
Snag mitigation methods considered included modifying the bucket geometry, integrating a mechanical or structural fuse in the hoist system, and integrating a fast‑acting braking system.
Liftech developed concepts for modifying the bucket geometry and integrating a fuse into the hoist system. The recommended fuse consists of rocking beams and hydraulic cylinders. The system detects rope loads, and for loads above a preset value, the cylinders release, allowing the rocker beams to rotate a fixed amount. This results in a decrease in rope stretch, which provides time for the brakes to set and the machinery to stop rotation prior to overloading the structure and other components.
We provided concept drawings and a comprehensive report describing the hoist system response, including required characteristics and resulting improvements from the recommended hydraulic fuse system.