Hoist Overload Devices Increase Safety
Though overload protection is common in hoists today, many safety managers assume their cranes have them when they actually may not. Overloading a crane or hoist by inexperienced operators or through negligence is a dangerous practice that could result in mechanical or structural failure of the crane, hoisting equipment, or the supporting structure. Many hoists are mechanically capable of lifting more than the rated load and even more than the 125% test load as required by ASME and OSHA when placing a new unit into service.
Test loads exceeding the rated load must never be more than 125% of the capacity rating of the lifting device or system. And this testing is to be performed under controlled conditions only by qualified and trained professionals and only to verify the structural and mechanical condition of the hoist or crane unit.
Hoist overload protection is becoming increasingly more common in new hoists; however, many existing hoists throughout the United Stated do not have overload protection and require careful use by the crane operator to avoid lifting loads exceeding the hoist’s capacity. Overload sensing devices can be retrofitted to all hoists and the costs are well justified by the peace of mind knowing an operator cannot overload the hoist.
Hoist overloads come in different types and complexity:
The most simple overload is clutch-type devices found on inexpensive Electric Chain Hoists. If you overload this type of hoist over some percentage over 100%, the clutch will start to slip and the load cannot be raised. Frequent overloads will wear out the clutch surface requiring adjustment and ultimately, replacement of the hoist load limiting clutch.
Mechanical/Electrical hoist overloads are used in the hoist reeving or other structural components of the hoist. These devices employ springs or bevelled washers that compress under a defined load to engage an electrical switch, that will shut off the upward-lifting motion. Electric overhead protection devices sense how much current is being drawn by the motor and ceases the upward-lifting capability when the current draw indicates too much force is being required to lift the load. Overload protection can be integrated into many hoist variable frequency drive controllers.
Responsible, trained and qualified operators are your first line of defence against potentially overloading your crane and hoists, but overload protection is a great way to ensure that an accident caused from overloading will not impact your business.
Your local CRANE 1 Technician or Inspector can help you determine whether your crane is equipped with overload protection and recommend the type that’s best suited to your application.
