You may have heard that overhead crane side pulling can be dangerous. How serious can it really be? And what exactly constitutes a side pull? To find out answers to these questions, and learn how to prevent side pulling, read on!
What is Side Pulling?
According to OSHA 29 CFR 1910.179(a)(54),
“Side pull means that portion of the hoist pull acting horizontally when the hoist lines are not operated vertically.”
So, what does that mean?
Perhaps you are having a rough time getting that load centered beneath the hoist. It might be odd shaped, and you do not have the right type of sling for the object you need to lift. Rather than stop and find the sling you need, you try to lift it anyway. When the load is not centered, and the operator performs the lift anyway, that is considered one type of side pulling.
Maybe you just need to drag a small piece of equipment over a few feet across the floor, and it’s too heavy to lift. You could center the hoist over it and get a rope around it, but it seems easier just to use the overhead crane to pull it into position.
Well, another type of side pulling occurs when an attempt is to move the load object horizontally (instead of vertically) without the load fully suspended beneath the hoist.
Sometimes you may want to lift a load that is beyond the end of the bridge beam for your crane. It doesn’t seem like a big deal, but it could easily damage the safety stops and, in rare cases, lead the trolley hoist to fall off the end of the beam. That is another example of a side pull.
Overhead cranes and hoists are engineered to lift and lower straight up and down, respectively. They are only meant to handle vertical loads, not horizontal loads — and subjecting them to side pull loads can be extremely dangerous.
Hazards of Side Pulling
Here is what ASME B30.16 has to say in relation to overhead hoists:
“Hoists shall not be operated unless the hoist unit is centered over the load, except when authorized by a qualified person who has determined that the components of the hoist and its mounting will not be overstressed.”
Overhead cranes are simply not designed to pull loads sideways. In fact, just 2° out of plumb will introduce stresses the crane was not accounted for in its design. Your overhead crane’s specifications, loads, and safety limits do not account for side pulling which makes side pulling extremely dangerous.
There are a couple of different things that can happen when side pulling is involved. Because the load is applied from the side rather than straight up or down, the wire rope can jump the drum and become tangled around the shaft. The wires can also slide out of the groove and scrub against either the drum or remaining rope.
The pendulum effect that occurs as the load tries to center itself can be dangerous and unpredictable. A swinging load can injure those near the load, damage other equipment, and cause the wire rope to jump the drum. There are also going to be unexpected stresses on the rope which might exceed its rating. Even if everything seems fine once the load has managed to center itself, the swinging may have caused stresses on the crane not designed to handle.
All these situations can cause damage to the rope, drums, sheaves and other components of the overhead crane that can lead to weakness and inability to handle. The next time a lift is performed, there is a chance the crane may fail at a load that would otherwise be within its capabilities.
How to Prevent Side Pulling
One of the best ways to prevent side pulling is operator and rigger training that includes specific definitions of side pulling and the hazards involved.
The center of gravity of a load must be positioned beneath the hoist for a safe lift that avoids side loads. It is also wise to make sure that the appropriate hoists remain available to side pull due to using the wrong type of hoist. However, there are other solutions besides training.
There are limiting systems and warning systems to help you avoid accidental side pulling. They make use of a tilt sensor, or inclinometer, clamped either to the hoist near the frame or at the dead end of the wire rope. When they sense a load is off axis, they either issue a warning or stop motion and travel. This solution is quite rugged but can be costly.
Side pull prevention mechanisms and limiting bars that can stop or momentarily reverse the lifting and travel motions are critical when a side load is detected. These mechanisms take up more space than limiting and warning systems and are more susceptible to damage, but they tend to be cheaper.
Another solution, especially for those situations where the load is beyond the reach of the crane, would be to use a portable gantry crane or engine hoist to position the load for safe lifting. These can be used to position the load beneath the overhead crane for safer lifting.
Benefits of Avoiding Side Pulls
Besides the safety aspects of avoiding side pulls, there are other benefits. You will lengthen the useful life of your equipment by not overloading it, and that includes the loads that result from side pulls. Avoiding side pulls also reduces the overall maintenance and repair costs for your equipment–and reduce costly equipment downtime. And don’t forget the costs involved in proper training and additional equipment is minimal compared to injuries and damaged equipment resulting from improper lifts.
If you have any questions about how to avoid side pulling or are interested in employing measures to prevent side pulls, give us a call at Hi-Speed Industrial Service. Not only do we have years of experience in cranes and hoists, but we are also familiar with the safety regulations involved. Let our team help you protect your equipment and employees!