The building blocks of an overhead bridge crane are a blend of modern alloys and state-of-the-arts physics. The alloys support the framework of the crane, combining with a series of tracks to enable an awkward payload to move smoothly to any point within the crane’s coverage area. Load wheels whir into action, establishing a familiar workflow where the bridge crane harnesses three planes of movement. In translating this building block approach into real life values, the system is actually comprised of welded gantry sections and precisely fastened components, mechanical assemblies possessed of the necessary attributes to convey dangerously heavy materials while maintaining a rigorous safety standard.
In an ideal world, the burden of a rated load will always be lifted and delivered without issue. Unfortunately, we live in the real world, a place where parts wear and age. Whether intent on avoiding a slow and dismal breakdown, or in curtailing the possibility of a catastrophic failure, some kind of inspection procedure must be adhered to when operating a bridge crane. The legislation of this inspection requirement, of course, depends on which country the crane is being operated. The OSHA (Occupational Safety and Health Administration) governs this process in the United States, with Australian crane operations complying with the Safe Work Australia policy guide. Note, it’s worth linking across to the Safe Work Australia documentation site to read the information on bridge and gantry crane Working Load Limit (WLL) before going any further, arming yourself and potential crane operators on where to locate the rated load capacity on your crane.
Moving on from matters of legislation, the professional maintenance of an overhead crane should always contain an element of common sense. In other words, focus on the load bearing components, on the parts that will age fastest, following up with a visual inspection of the runway guides to check for the invasive presence of debris and foreign matter. It’s amazing how fast a few small pebbles can bring an expensive crane to a halt if the tracks are obstructed.
- Inspect the condition and integrity of fasteners, clips and bolts
- Evaluate the alignment of the rails (Checking for rail parallelism)
- Analyze the general state of the tracks, evaluating each span for aging and/or damage.
- Carry out the same procedures on the load wheels.
Remember, this is a three-dimensional operation. Carry out scheduled inspections to measure parallelism between runway spans, but shift up this check by also looking to see if the rails are level with respect to the beams or framework they’ve been installed upon. Pay particular attention to load points, areas of stress where the track deviates or turns, and look for stress fractures and broken tie-backs. Finally, expand the inspection procedure to cover crane cradles and cables, finishing the inspection with a comprehensive report and call to action.
