A machine’s boom was stuck in place with about 400 lb hanging from the crane mounted to it. The worker operating it reached over his head and gave the boom a good, sharp shove. The action was immediately followed by a pain in his back that later radiated into his neck.
The boom in question was mounted on the back of a spike-reclaiming machine working on railroad tracks. The machine pulls spikes from the railroad ties and deposits them on a conveyor belt. The conveyor transports the spikes toward the rear of the machine and into metal kegs set up to collect them.
The boom and gantry crane hang over the conveyor’s end and the keg staging area. Operators attach straps on a full keg to a cable that leads to the crane. The crane winches up one or two kegs and carries them to the end of the boom so they clear the end of the spike reclaimer. Then operators pivot the boom and deposit the kegs trackside for later pickup.
The boom pivots between two steel support brackets. Horizontal wear plates welded to each bracket directly contact the boom surface. This type of design was considered standard and acceptable in the railroad industry at the time of the incident.
Investigators examined the spike reclaimer after the incident and determined the pivot point may not have been sufficiently lubricated.
The pivot pin that holds the boom between the two brackets does not carry the majority of the gantry crane load. Instead, most of the load is transmitted to the wear plates, so it is these surfaces that must be properly maintained and lubricated.
As part of the investigation, railroad workers and engineers attached a force gage to the cable when it was loaded with two full kegs. The investigators were able to move the boom, loaded with 400 lb, by applying 40 to 46 lb horizontally to the cable when the boom was properly lubricated.
Lack of lubrication is the most likely explanation for the boom sticking prior to and during the incident. The wear plates are visible and easily accessible, so operators can add lubricant at the beginning of a shift or as needed when a loaded boom begins to stick.
Investigators concluded that the worker should have unloaded the crane and properly lubricated the boom pivot before continuing with the job. Removing one of the kegs so the boom was not so heavily loaded could have also been a temporary fix.
Although the worker needed to move quickly to keep up with the flow of reclaimed spikes the conveyor delivered to the kegs, both investigators and the worker’s employer felt efficiency was not an excuse for putting himself in danger. The company had provided safety training, backwellness programs, safety-feedback opportunities, and a general culture that empowered employees to be safe on the job. Employees were encouraged to get help lifting heavy objects. They also could take the initiative to shut down equipment when they saw an unsafe condition.
Unfortunately, the worker who was injured did not take the time to do his job safely.
Edited by Jessica Shapiro
This month’s safety violation comes from the files of Lanny Berke, a registered professional engineer and Certified Safety Professional involved in forensic engineering since 1972. Got a safety violation to share? Send your images and explanations to [email protected].