Chain Hoist Overload Device
Does overload protection replace rated-capacity planning?
No. The rated capacity remains the legal and engineering limit; overload protection is a last-line safeguard.
What happens in a slip-clutch design?
The drive transmits torque only up to a preset threshold; above that, the clutch slips and the hoist motor may continue turning without raising the load.
Is overload prevention required by WorkSafeBC for every hoist?
Not as a universal blanket requirement, but WorkSafeBC specifically requires an overload prevention system when the load cannot be accurately determined and imposes overload-related requirements on certain crane/hoist categories.
A chain hoist overload device is a safety feature that prevents or limits lifting when the hoist is asked to raise a load beyond its rated capacity. On electric chain hoists, this is commonly a slip-clutch mechanism, while on some systems it may be an electronic or electromechanical overload prevention device. It detects excessive lifting force and blocks upward travel, slips mechanically, or interrupts the lift circuit before damaging overload occurs.
On a Canadian shop floor, the hoist's rated capacity governs the lift, and the overload device is not a substitute for knowing the load weight. WorkSafeBC requires an overload prevention system when the load weight cannot be accurately determined. The device is used during lifts where load mass is uncertain, variable, or partially concealed, providing a hardware safeguard against exceeding capacity. Common on electric chain hoists as a factory-set slip clutch, it slips when overload is reached, preventing the load from rising. In advanced systems, a sensor interrupts the up function once a preset threshold is reached, while allowing safe lowering. It is treated as a backup safeguard, not a method to test the hoist's capacity.
Assuming the presence of overload protection: Many users assume every hoist has it, but hoist performance standards do not necessarily require overload limiting as standard equipment, so the hoist may be unprotected unless specified.
Using the device as a load-weighing tool: The overload clutch is an emergency protective device and is not a reliable indicator of the exact load or a permitted way to find the hoist limit by trial lift.
Ignoring mechanical wear or incorrect setup: Repeated overload events can wear clutch surfaces or detune the protection system, and a worn or incorrectly adjusted device can fail to protect the hoist.