Cranes, which are used in factories, on construction sites, and in dozens of others kinds of workplaces, are necessary to help move large loads from one level to another. However, every year, dozens of people report injuries and deaths due to crane collapse, crane tip over, and other crane problems.
While these accidents can sometimes be attributed to malfunction and faulty manufacturing, in the vast majority of cases, the accidents are simply a result of improper usage or poor employee training. Therefore, many of these accidents can be avoided altogether, significantly cutting down on the number of workplace injuries due to cranes. Cranes come equipped with a number of standard safety devices that help make the job of workers easier, if they understand how to use them. One such device working to keep employees safer is the upper limit switch.
According to report prepared by Boise State, which you can read here, all building crane a hoist systems should have limit switches. Limit switches are meant to keep the hook and ball part of the crane from colliding with the drum. If that happens, the hook block will crash into the drum, which, more often than not, will cause the cable to snap, tangle, or otherwise fail. If that happens, not only will the load come crashing down, but it can also cause the crane to become suddenly off balance and tip, or can cause the crane’s boom to collapse. The wire rope system, when it snaps, can also whip into the air dangerously, so you can see how this can easily be a very dangerous situation.
Upper limit switches prevent this from happening. When the hoist reaches the highest limit, the upper limit switch will shut off the crane’s electricity to the hydraulics or other system that raises the load. Most cranes also have a lower limit switch, which alerts the operator when the drum is reaching the end of the cable. However, reaching the upper limit is much more dangerous. Many cranes have a second fail-safe mode so that if the first upper limit switch fails, the second will kick into action.
In most cases, the upper limit switch shouldn’t need to stop power at all. The problem, though, as talked about here, is that some operators use the upper limit switch as an operating tool. This is not how the switch is meant to be used. The upper limit switch is strictly a safety device and should not be used passively to reach the highest lift limit possible on every lift. Most of the time, you have no need to lift that high.
The upper limit switch can also fail if not properly tested. As part of OSHA rule at 29 CFR 1910.179(n)(4)(i), crane operators are required to test the upper limit switch at the beginning of every shift. The test should be done very slowly and with no load attached, so that if the switch fails, there is little opportunity for injury. Many operators never test limit switches, which can be a huge problem. You can read more about OSHA requirements for testing here. At the end of the day, this step may take some time, but it is worth it to keep everyone on the job site safe. If you have been injured in a crane accident contact a crane accident lawyer today.