Avoid These 3 Misconceptions About Overhead Cranes
Posted on: 17 April 2020
Overhead cranes carry many benefits with them. For one, they make the lifting of heavy loads much easier. Likewise, they reduce on-floor obstructions and worker fatigue. And they can increase safety because they're out of the way.
While overhead cranes can, indeed, increase safety in the factory, some common misconceptions about their features can have the opposite effect. Avoid the following dangerous misconceptions for a safe work environment.
1. Upper Limit Switch
One misconception is that operators need to lift their loads as high as possible — all the way to the upper limit switch. In fact, the purpose of the upper limit switch is to prevent the hook assembly from hitting the drum. So, while it's reasonably safe to trigger the upper limit switch, it is supposed to function as a safety measure, not as a manner of operation.
What's more, the upper limit switch can fail. The hook assembly may hit the drum, which will most likely cause the crane to drop its load. The better practice is to only lift loads as high as needed in order to clear all obstacles.
2. Secondary Brake
A second misconception also involves a safety feature. The thought is that overhead cranes feature a secondary brake that will kick in if the primary brake fails, which renders the area under a load safe for work. In fact, secondary brakes can be either a mechanical load brake or a regenerative brake, and the type will determine what the crane does with the load in the event of primary brake failure.
A mechanical load brake will, indeed, continue to hold the load if the primary brake fails. Because of expense and brake limitations, the mechanical load brake is less in use than the regenerative model. The regenerative brake prevents the crane from dropping the load. But it doesn't hold the load. Rather, it lowers the load at the normal rate of speed, which means the area below is unsafe.
3. Side Pull
The third misconception involves the loading capacity of the crane. Some operators might think it's safe to pull a relatively light item from the next bay over with the crane, a practice known as the side pull. Overhead cranes are designed to lift straight up with the load directly below them. A side pull can result in the load chain moving out of its groove in the hoist drum, which causes damage.
Physics play a part in this misconception, too. As the crane pulls the load out sideways, the load will attempt to center itself again. The result is a pendulous swinging, which can be harmful to both property and people. Instead, it's possible to have installation experts add an adjustable lifting beam and counterweight to facilitate off-center loading.
Avoid the above pitfalls, and your overhead crane operation should be safe.
To learn more, contact an overhead crane supplier.
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